Patent Publication Number: US-2022218206-A1

Title: Micro-optic probes for neurology

Description:
RELATED APPLICATIONS 
     This application is a continuation application of U.S. patent application Ser. No. 15/566,041 (Docket No. GTY-001-US), titled “Micro-Optic Probes for Neurology”, filed Oct. 12, 2017, United States Publication Number 2018-0125372, published May 10, 2018, which in a National Phase entry of International PCT Patent Application Serial Number PCT/US2016/027764 (Docket No. GTY-001-PCT), titled “Micro-Optic Probes for Neurology” filed Apr. 15, 2016, Publication Number WO 2016/168605, published Oct. 20, 2016, which claims the benefit of: U.S. Patent Provisional Application Ser. No. 62/322,182, titled “Micro Optic Probes for Neurology”, filed Apr. 13, 2016 and U.S. Provisional Application Ser. No. 62/148,355, titled “Micro-Optic Probes for Neurology”, filed Apr. 16, 2015, the content of each of which is incorporated herein by reference in its entirety for all purposes. This application is related to: U.S. Provisional Application Ser. No. 62/212,173, titled “Imaging System includes Imaging Probe and Delivery Devices”, filed Aug. 31, 2015; the content of which is incorporated herein by reference in its entirety for all purposes. 
    
    
     FIELD 
     Inventive concepts relate generally to imaging systems, and in particular, neural imaging systems including imaging probes, imaging consoles and delivery devices. 
     BACKGROUND 
     Imaging probes have been commercialized for imaging various internal locations of a patient, such as an intravascular probe for imaging a patient&#39;s heart. Current imaging probes are limited in their ability to reach certain anatomical locations due to their size and rigidity. Current imaging probes are inserted over a guidewire, which can compromise their placement and limit use of one or more delivery catheters through which the imaging probe is inserted. There is a need for imaging systems that include probes with reduced diameter, high flexibility and ability to be advanced to a patient site to be imaged without a guidewire, as well as systems with one or more delivery devices compatible with these improved imaging probes. 
     SUMMARY 
     According to one aspect of the present inventive concepts, an imaging system for a patient comprises: an imaging probe and is configured to produce an image of the patient. The imaging probe comprises: an elongate shaft for insertion into the patient and comprising a proximal end, a distal portion, and a lumen extending between the proximal end and the distal portion; a rotatable optical core comprising a proximal end and a distal end, the rotatable optical core configured to optically and mechanically connect with an interface unit; a probe connector positioned on the elongate shaft proximal end and surrounding at least a portion of the rotatable optical core; and an optical assembly positioned in the elongate shaft distal portion and proximate the rotatable optical core distal end, the optical assembly configured to direct light to tissue and collect reflected light from the tissue. 
     In some embodiments, the imaging probe comprises a shear-thinning fluid located within the distal portion of the elongate shaft, such as a shear-thinning fluid configured to reduce undesired rotational variances of the rotatable optical core (e.g. and the attached optical assembly  130 ) while avoiding excessive loads being placed on the rotatable optical core. 
     In some embodiments, the imaging probe further comprises at least one space reducing element positioned between the elongate shaft and the rotatable optical core, and the at least one space reducing element can be configured to reduce rotational speed variances of the rotatable optical core. The at least one space reducing element can be positioned at least in a portion of the elongate shaft distal portion. The at least one space reducing element can be configured to reduce the rotational speed variances by increasing the shear-thinning of the shear-thinning fluid. 
     In some embodiments, the imaging probe further comprises an inertial assembly configured to reduce rotational speed variances of the rotatable optical core. 
     In some embodiments, the imaging probe further comprises an impeller attached to the rotatable optical core and configured to resist rotation of the rotatable optical core when the rotatable optical core is retracted. 
     In some embodiments, the imaging probe further comprises a stiffening element embedded into the elongate shaft that is configured to resist flexing of the elongate shaft and comprises an optically transparent portion. 
     In some embodiments, the imaging probe further comprises a reduced inner diameter portion of the elongate shaft, wherein the reduced inner diameter portion is configured to reduce rotational speed variances of the rotatable optical core. 
     In some embodiments, the imaging system is configured to create a three dimensional image by retraction of the elongate shaft. 
     In some embodiments, the imaging system is configured to detect and/or quantify malapposition of a flow diverter implanted in the patient. 
     In some embodiments, the imaging system is configured to provide quantitative and/or qualitative information used to determine the size of a flow diverter to be implanted in the patient and/or position a flow diverter in the patient. The quantitative and/or qualitative information can comprise information related to a parameter selected from the group consisting of: perforator location; perforator geometry; neck size; flow diverter mesh density; and combinations thereof. 
     In some embodiments, the imaging system is configured to image a stent retriever at least partially positioned in thrombus of the patient. The imaging system can be configured to image thrombus at least one of: thrombus not engaged with the stent retriever or thrombus not removed by the stent retriever. 
     In some embodiments, the imaging system is configured to quantify a volume of thrombus in the patient. The quantified thrombus can comprise thrombus selected from the group consisting of: residual thrombus in acute stroke; thrombus remaining after a thrombus removal procedure; thrombus present after flow diverter implantation; and combinations thereof. 
     In some embodiments, the imaging system is configured to provide implant site information, and the implant site information is used to select a particular implantable device for implantation in the patient. The system can further comprise the implantable device for implantation in the patient, and the implantable device can comprise a device selected from the group consisting of: stent; flow diverter; and combinations thereof. The implantable device can be selected based on an implantable device parameter selected from the group consisting of: porosity; length; diameter; and combinations thereof. 
     In some embodiments, the imaging system is configured to provide porosity information of a device implanted in the patient. The porosity information can comprise porosity of a portion of the implanted device that is to be positioned proximate a sidebranch of a vessel in which the implanted device is positioned. The system can be configured to provide the porosity information based on a wire diameter of the implanted device. The system can further comprise the implanted device, and the implanted device can comprise a device selected from the group consisting of: stent; flow diverter; and combinations thereof. The imaging system can be further configured to provide information related to implanting a second device in the patient. The first implanted device can comprise a stent, and the second implanted device can comprise a flow diverter. The first implanted device can comprise a flow diverter and the second implanted device can comprise a flow diverter. The imaging system can be further configured to provide an image during deployment of the implanted device. The imaging system can be further configured to allow modification of the implanted device while the optical assembly is positioned proximate the implanted device. The modification can comprise a modification of the porosity of the implanted device. The system can further comprise a balloon catheter configured to perform the porosity modification. 
     In some embodiments, the imaging system is configured to image at least one perforator artery of the patient. The at least one perforator artery can comprise a diameter of at least 50 μm. The system can further comprise a therapeutic device. The therapeutic device can comprise a device selected from the group consisting of: stent retriever; embolization coil; embolization coil delivery catheter; stent; covered stent; stent delivery device; aneurysm treatment implant; aneurysm treatment implant delivery device; flow diverter; balloon catheter; and combinations thereof. 
     In some embodiments, the system further comprises at least one guide catheter. The at least one guide catheter can comprise a microcatheter. The microcatheter can comprise an inner diameter between 0.0165″ and 0.027″. The microcatheter can comprise an inner diameter between 0.021″ and 0.027″. 
     In some embodiments, the imaging probe is constructed and arranged to access a vessel of a human being. 
     In some embodiments, the imaging probe is configured to access blood vessels of the brain. 
     In some embodiments, the elongate shaft comprises a material selected from the group consisting of: FEP; PTFE; Pebax; PEEK; Polyimide; Nylon; and combinations thereof. 
     In some embodiments, the elongate shaft comprises a material selected from the group consisting of: stainless steel; nickel titanium alloy; and combinations thereof. 
     In some embodiments, the elongate shaft comprises a first portion comprising a metal tube and a second portion comprising a braided shaft. 
     In some embodiments, the elongate shaft comprises a hydrophobic material configured to reduce changes in length of the elongate shaft when the elongate shaft is exposed to a fluid. 
     In some embodiments, the elongate shaft comprises an outer diameter that varies along the length of the elongate shaft. 
     In some embodiments, the elongate shaft comprises an inner diameter that varies along the length of the elongate shaft. 
     In some embodiments, the elongate shaft comprises an outer diameter between 0.006″ and 0.022″. 
     In some embodiments, the elongate shaft comprises an outer diameter of approximately 0.0134″. 
     In some embodiments, the elongate shaft comprises an inner diameter between 0.004″ and 0.012″. The elongate shaft can comprise a wall thickness of approximately 0.003″. 
     In some embodiments, the elongate shaft comprises an outer diameter less than or equal to 500 μm. 
     In some embodiments, the elongate shaft comprises an outer diameter less than or equal to 1 mm. 
     In some embodiments, the elongate shaft comprises an outer diameter of approximately 0.016″. At least the most distal 30 cm of the elongate shaft can comprise an outer diameter less than or equal to 0.016″. 
     In some embodiments, the elongate shaft can comprise an outer diameter of approximately 0.014″. The elongate shaft can be configured to be advanced through vasculature without a guidewire or delivery device. At least the most distal 30 cm of the elongate shaft can comprise an outer diameter less than or equal to 0.014″. 
     In some embodiments, the elongate shaft comprises a mid portion proximal to the distal portion, and the distal portion comprises a larger outer diameter than the mid portion. The elongate shaft distal portion can comprise a larger inner diameter than the inner diameter of the mid portion. The larger outer diameter distal portion can surround the optical assembly. 
     In some embodiments, the elongate shaft comprises a length of at least 100 cm. The elongate shaft can comprise a length of no more than 350 cm. 
     In some embodiments, the elongate shaft comprises a length of at least 200 cm. The elongate shaft can comprise a length of at least 220 cm. The elongate shaft can comprise a length of at least 240 cm. The elongate shaft can comprise a length of approximately 250 cm. 
     In some embodiments, the elongate shaft further comprises a middle portion, and the elongate shaft distal portion comprises a larger inner diameter than the elongate shaft middle portion. The elongate shaft distal portion inner diameter can be at least 0.002″ larger than the inner diameter of the elongate shaft middle portion. The elongate shaft distal portion can comprise a similar outer diameter to the outer diameter of the elongate shaft middle portion. The elongate shaft distal portion can comprise an outer diameter than is greater than the elongate shaft middle portion outer diameter. The elongate shaft distal portion outer diameter can be at least 0.001″ larger than the outer diameter of the elongate shaft middle portion. The elongate shaft distal portion can comprise a wall thickness that is less than the elongate shaft middle portion wall thickness. The elongate shaft distal portion can comprise a stiffer material than the elongate shaft middle portion. The elongate shaft distal portion can comprise a stiffening element. 
     In some embodiments, the elongate shaft distal portion comprises a rapid exchange guidewire lumen. The guidewire lumen can comprise a length of less than or equal to 150 mm. The guidewire lumen can comprise a length of at least 15 mm. The guidewire lumen can comprise a length of at least 25 mm. 
     In some embodiments, the elongate shaft distal portion comprises an optically transparent window, and the optical assembly is positioned within the optically transparent window. The optically transparent window can comprise a length less than 20 mm, or less than 15 mm. The optically transparent window can comprise a material selected from the group consisting of: Pebax; Pebax 7233; PEEK; amorphous PEEK; polyimide; glass; sapphire; nylon 12; nylon 66; and combinations thereof. The elongate shaft can comprise at least a first portion, positioned proximate the optically transparent window, and the first portion can comprise a braided shaft. The elongate shaft can further comprise a second portion positioned proximal to the first portion, and the second portion can comprise a metal tube. The optically transparent window can comprise a length between 1 mm and 100 mm. The optically transparent window can comprise a length of approximately 3 mm. The optically transparent window can comprise a material selected from the group consisting of: nylon; nylon 12; nylon 66; and combinations thereof. 
     In some embodiments, the elongate shaft comprises a stiffening element. The stiffening element can be positioned at least in the elongate shaft distal portion. The stiffening element can be constructed and arranged to resist rotation of the elongate shaft distal portion during rotation of the rotatable optical core. The stiffening element can terminate proximal to the optical assembly. The stiffening element can comprise a coil. The stiffening element can comprise metal coils wound over PTFE. The stiffening element can comprise a coil wound in a direction such that rotation of the rotatable optical core tightens the metal coil. The imaging probe can further comprise a fluid positioned between the rotatable optical core and the elongate shaft, and the metal coil can be configured to reduce twisting of the elongate shaft by torque forces applied by the fluid. 
     In some embodiments, the elongate shaft comprises a distal end, and the imaging probe comprises a spring tip attached to the elongate shaft distal end. The spring tip can comprise a radiopaque portion. The spring tip can comprise a length between 2 cm and 3 cm. 
     In some embodiments, the elongate shaft comprises a proximal portion constructed and arranged to be positioned in a service loop, and the elongate shaft proximal portion has a different construction than the remainder of the elongate shaft. The different construction can comprise a larger outer diameter. The different construction can comprise a thicker wall. 
     In some embodiments, the system further comprises a fluid positioned in the elongate shaft lumen, and a fluid interacting element positioned in the distal portion of the lumen of the elongate shaft, and the fluid interacting element is configured to interact with the fluid to increase load on the rotatable optical core during rotation of the rotatable optical core. The fluid interacting element can comprise a coil positioned in the elongate shaft lumen. The fluid interacting element can comprise a non-circular cross section of the lumen. The non-circular cross section can comprise a geometry selected from the group consisting of: polygon shaped cross section of a lumen of the elongate shaft; projections into a lumen of the elongate shaft; recesses in inner diameter of the elongate shaft; and combinations thereof. The fluid can comprise a low viscosity fluid. The fluid can comprise a viscosity at or below 1000 Cp. 
     In some embodiments, the imaging probe further comprises a first sealing element located within the elongate shaft lumen, the sealing element positioned between the rotatable optical core and the elongate shaft, and configured to slidingly engage the rotatable optical core and to resist the flow of fluid around the sealing element (e.g. to provide a seal as the rotatable optical core is rotated). The first sealing element can be positioned in the elongate shaft distal portion. The imaging probe can further comprise a first liquid positioned proximate the optical assembly and a second fluid positioned proximate the rotatable optical core, and the first sealing element can be positioned between the first liquid and the second liquid. The first liquid can comprise a first viscosity and the second liquid can comprise a second viscosity greater than the first viscosity. The first sealing element can be further configured to resist rotation of the rotatable optical core. The first sealing element can comprise a hydrogel. The first sealing element can comprise an adhesive bonded to the elongate shaft. The first sealing element can comprise a UV-cured adhesive bonded to the elongate shaft. The rotatable optical core can comprise a material that does not bond to the adhesive. The first sealing element can comprise a compliant material. The compliant material can comprise silicone. The system can further comprise a second sealing element positioned between the rotatable optical core and the elongate shaft, and the second sealing element can be configured to slidingly engage the rotatable optical core and can be further configured to resist flow of fluid around the second sealing element, and the imaging probe can further comprise a fluid positioned between the first sealing element and the second sealing element. The first and second sealing elements can be separated by a distance of between 1 mm and 20 mm. The fluid positioned between the first and second sealing elements can comprise a viscosity between 10 Cp and 100 Cp. The first sealing element can be positioned proximal and proximate the optical assembly and the second sealing element can be positioned distal to the first sealing element. 
     In some embodiments, the imaging probe comprises a sealing element positioned proximate the proximal end of the elongate shaft. The sealing element can be positioned between the elongate shaft and the probe connector. 
     In some embodiments, the rotatable optical core comprises a single mode glass fiber with an outer diameter between 40 μm and 175 μm. 
     In some embodiments, the rotatable optical core comprises a single mode glass fiber with an outer diameter between 80 μm and 125 μm. 
     In some embodiments, the rotatable optical core comprises a polyimide coating. 
     In some embodiments, the rotatable optical core comprises an outer diameter between 60 μm and 175 μm. The rotatable optical core can comprise an outer diameter of approximately 110 μm. 
     In some embodiments, the rotatable optical core comprises a material selected from the group consisting of: silica glass; plastic; polycarbonate; and combinations thereof. 
     In some embodiments, the rotatable optical core comprises a numerical aperture of approximately 0.11. 
     In some embodiments, the rotatable optical core comprises a numerical aperture of at least 0.11. 
     In some embodiments, the rotatable optical core comprises a numerical aperture of approximately 0.16. 
     In some embodiments, the rotatable optical core comprises a numerical aperture of approximately 0.20. 
     In some embodiments, the rotatable optical core is constructed and arranged to rotate in a single direction. 
     In some embodiments, the rotatable optical core is constructed and arranged to rotate in two directions. 
     In some embodiments, the rotatable optical core is configured to be retracted within the elongate shaft. The system can further comprise purge media introduced between the rotatable optical core and the elongate shaft. The purge media can provide a function selected from the group consisting of: index matching; lubrication; purging of bubbles; and combinations thereof. 
     In some embodiments, the optical assembly comprises an outer diameter between 80 μm and 500 μm. The optical assembly can comprise an outer diameter of approximately 150 μm. 
     In some embodiments, the optical assembly comprises an outer diameter of at least 125 μm. 
     In some embodiments, the optical assembly comprises a length between 200 μm and 3000 μm. The optical assembly can comprise a length of approximately 1000 μm. 
     In some embodiments, the optical assembly comprises a lens. The lens can comprise a GRIN lens. The lens can comprise a focal length between 0.5 mm and 10.0 mm. The lens can comprise a focal length of approximately 2.0 mm. The lens can comprise a ball lens. 
     In some embodiments, the optical assembly comprises a reflecting element. 
     In some embodiments, the optical assembly comprises a lens, a reflecting element and a connecting element, and the connecting element positions the reflecting element relative to the lens. The connecting element can comprise an element selected from the group consisting of: tube; flexible tube; heat shrink; optically transparent arm; and combinations thereof. The connecting element can position the reflecting element a distance of between 0.01 mm and 3.0 mm from the lens. The connecting element can position the reflecting element a distance of between 0.01 mm and 1.0 mm from the lens. The reflecting element can comprise a cleaved portion of a larger assembly. The reflecting element can comprise a segment of a wire. The wire can comprise a gold wire. The lens can comprise a GRIN lens. The lens can have at least one of an outer diameter of 150 μm or a length of 1000 μm. The lens can further comprise a coreless lens positioned proximal to and optically connected to the GRIN lens. 
     In some embodiments, the imaging probe comprises the inertial assembly, and the inertial assembly is positioned proximate the optical assembly. 
     In some embodiments, the imaging probe comprises the inertial assembly, and the inertial assembly further comprises a wound hollow core cable comprising a proximal end and a distal end, the distal end of the wound hollow core cable being affixed to the rotatable optical core at a location proximal to the optical assembly, and the proximal end of the wound hollow core cable being unattached to the optical core. 
     In some embodiments, the imaging probe comprises the inertial assembly, and the inertial assembly comprises fluid within the elongate shaft lumen and a mechanical resistance element positioned on the distal portion of the optical core, and the mechanical resistance element is in contact with the fluid and configured to resist rotation of the rotatable optical core. 
     In some embodiments, the imaging probe comprises the inertial assembly, and the inertial assembly is constructed and arranged to provide inertial dampening which increases with rotational speed. 
     In some embodiments, the imaging probe comprises the inertial assembly, and the inertial assembly comprises a projection from the rotatable optical core. The projection can be constructed and arranged to frictionally engage the elongate shaft. The projection can be constructed and arranged to cause shear force that applies a load to the rotatable optical core during rotation. 
     In some embodiments, the imaging probe comprises the inertial assembly, and the inertial assembly comprises a projection from the elongate shaft. The projection can be constructed and arranged to frictionally engage the rotatable optical core. The projection can be constructed and arranged to cause shear force that applies a load to the rotatable optical core during rotation. The projection can be created by a thermal processing of the elongate shaft. 
     In some embodiments, the imaging probe comprises the inertial assembly, and the inertial assembly comprises a compressed portion from the elongate shaft. The system can further comprise at least one band configured to crimp the elongate shaft to create the compressed portion. 
     In some embodiments, the imaging probe comprises the inertial assembly, and the inertial assembly comprises the impeller. 
     In some embodiments, the imaging probe comprises the impeller, and the impeller is constructed and arranged to cause wind-up loading of the rotatable optical core during rotation. 
     In some embodiments, the imaging probe comprises the impeller and the imaging probe further comprises fluid in a lumen, and the impeller is configured to engage the fluid during rotation of the rotatable optical core. 
     In some embodiments, the imaging probe comprises the impeller, and the impeller comprises a turbine. 
     In some embodiments, the imaging probe comprises the impeller, and the impeller is configured to frictionally engage the elongate shaft during rotation of the rotatable optical core. 
     In some embodiments, the imaging probe comprises the impeller, and the impeller comprises a vane-type micro structure. 
     In some embodiments, the imaging probe comprises the impeller, and the impeller comprises a flywheel. 
     In some embodiments, the imaging probe comprises the stiffening element. 
     In some embodiments, the imaging probe comprises the stiffening element, and the stiffening element comprises a wire coil embedded in the elongate shaft, and the wire spiral geometry and a pullback spiral rotational pattern of the optical assembly are matched but offset by approximately one-half of a wire spiral, such that an imaging beam of the optical assembly passes between the wire spirals during pullback. 
     In some embodiments, the imaging probe comprises the stiffening element, and the stiffening element comprises a wound wire formed over the rotatable optical core. 
     In some embodiments, the imaging probe comprises the stiffening element, and the stiffening element comprises a stiffening member embedded in the elongate shaft, and the stiffening member geometry and a pullback spiral pattern of the optical assembly are matched but offset by approximately one-half of a wire spiral, such that an imaging beam of the optical assembly passes between the wire spirals during pullback. 
     In some embodiments, the imaging probe comprises the reduced portion of the elongate shaft. The imaging probe can comprise at least one band crimped about the elongate shaft and constricting the elongate shaft to create the reduced portion of the elongate shaft. At least one band can provide a seal to be formed between the rotatable core and the elongate shaft. The reduced portion of the elongate shaft can comprise a thermally treated portion of the elongate shaft. 
     In some embodiments, the imaging probe further comprises a fluid positioned within the lumen of the elongate shaft. The fluid can be configured to reduce variances in rotational speed of the rotatable optical core. The system can further comprise a sealing element positioned proximate the proximal end of the elongate shaft, and the seal can be configured to maintain the fluid within the lumen. The fluid can comprise a first fluid positioned around the optical assembly and a second fluid positioned around the rotatable optical core. The first fluid can comprise a first viscosity and the second fluid can comprise a second viscosity greater than the first viscosity. The second fluid can be constructed and arranged to reduce variances in rotational speed of the rotatable optical core. The system can further comprise a sealing element positioned between the first fluid and the second fluid. The fluid can comprise a gel. The fluid can comprise a shear-thinning fluid. The fluid can comprise a shear-thinning gel. The fluid can be configured to provide lubrication. The fluid can be configured to cause the rotatable optical core to tend to remain centered in the elongate shaft during rotation of the rotatable optical core. The first fluid can comprise a viscosity between 10 Pa-S and 100,000 Pa-S. The first fluid can be configured to reduce in viscosity to a level of approximately 3 Pa-S at a shear rate of 100 s-1. The fluid can comprise a lubricant configured to reduce friction between the rotatable optical core and the elongate shaft. The fluid can comprise a first fluid and a second fluid, and the second fluid can be positioned within the elongate shaft proximate the optical assembly, and the first fluid can be positioned within the elongate shaft proximal to the second fluid. The imaging probe can further comprise a sealing element in between the first fluid and the second fluid. The sealing element can be positioned between 1 mm and 20 mm from the optical assembly. The sealing element can be positioned approximately 3 mm from the optical assembly. The first fluid can comprise a viscosity between 10 Pa-S and 100,000 Pa-S. The first fluid can comprise a shear-thinning fluid. The first fluid can be configured to reduce in viscosity to a level of approximately 3 Pa-S at a shear rate of 100 s-1. The first fluid material can comprise a fluid selected from the group consisting of: hydrocarbon-based material; silicone; and combinations thereof. The second fluid can comprise a viscosity between 1 Pa-S and 100 Pa-S. The second fluid can comprise a viscosity of approximately 10 Pa-S. The second fluid can comprise a fluid selected from the group consisting of: mineral oil; silicone; and combinations thereof. The imaging system can be configured to pressurize the fluid in the lumen. The imaging system can be constructed and arranged to perform the pressurization of the fluid to reduce bubble formation and/or bubble growth. The imaging system can be configured to pressurize the fluid in the lumen to a pressure of at least 100 psi. The imaging system can comprise a pressurization assembly configured to perform the pressurization of the fluid. The pressurization assembly can comprise a check valve. The fluid can comprise a lubricant. The lubricant can be configured to reduce friction between the rotatable optical core and the elongate shaft when at least a portion of the elongate shaft is positioned proximate and distal to the carotid artery. The fluid can comprise a high viscosity fluid. The elongate shaft can be constructed and arranged to expand when the fluid is pressurized. The elongate shaft can be constructed and arranged to expand to a first inner diameter when the fluid is at a first pressure. The elongate shaft can be constructed and arranged to expand to a second inner diameter when the fluid is at a second pressure. The elongate shaft can be constructed and arranged to become more rigid when the fluid is pressurized. The elongate shaft can be constructed and arranged to increase space between the rotatable optical core and the elongate shaft during the expansion by the pressurized fluid. The elongate shaft can be constructed and arranged to remain at least partially expanded when the fluid pressure is reduced. 
     In some embodiments, the imaging probe further comprises a torque shaft with a proximal end and a distal end, and the torque shaft can be fixedly attached to the rotatable optical core such that rotation of the torque shaft rotates the rotatable optical core. The torque shaft can comprise stainless steel. The torque shaft can comprise an outer diameter between 0.02″ and 0.09″. The torque shaft can comprise an outer diameter of approximately 0.025″. The torque shaft can comprise a length of approximately 49 cm. The torque shaft can comprise a dimension selected from the group consisting of: an inner diameter of approximately 0.015″; an outer diameter of approximately 0.025″; and combinations thereof. The torque shaft can comprise a wall thickness between 0.003″ and 0.020″. The torque shaft can comprise a wall thickness of approximately 0.005″. The torque shaft distal end can be positioned within 60 cm of the optical connector. The torque shaft distal end can be positioned within 50 cm of the optical connector. The torque shaft distal end can be positioned at least 50 cm from the optical assembly. The torque shaft distal end can be positioned at least 100 cm from the optical assembly. The imaging system can further comprise a retraction assembly constructed and arranged to retract at least one of the rotatable optical core or the elongate shaft, and the torque shaft distal end can be positioned proximal to the retraction assembly. The imaging probe can further comprise a fixation tube positioned between the torque shaft and the rotatable optical core. The fixation tube can be adhesively attached to at least one of the torque shaft or the rotatable optical core. 
     In some embodiments, the imaging system further comprises a visualizable marker constructed and arranged to identify the location of the optical assembly on a second image produced by a separate imaging device. The separate imaging device can comprise a device selected from the group consisting of: fluoroscope; ultrasonic imager; MM; and combinations thereof. The visualizable marker can be positioned on the optical assembly. The visualizable marker can be positioned at a fixed distance from the optical assembly. The imaging system can further comprise a connecting element connecting the visualizable marker to the optical assembly. 
     In some embodiments, the imaging probe can comprise multiple markers constructed and arranged to provide a rule function. The at least one of the multiple markers can comprise at least one of a sealing element or a rotational dampener. The multiple markers can comprise two or more markers selected from the group consisting of: radiopaque marker; ultrasonically reflective marker; magnetic marker; and combinations thereof. The multiple markers can be positioned on the rotatable optical core. The multiple markers can be positioned on the elongate shaft. 
     In some embodiments, the imaging system further comprises a console comprising a component selected from the group consisting of: rotation assembly; retraction assembly; imaging assembly; algorithm; and combinations thereof. 
     In some embodiments, the imaging system further comprises a rotation assembly constructed and arranged to rotate the rotatable optical core. The rotation assembly can comprise a motor. The imaging system can further comprise a retraction assembly constructed and arranged to retract at least one of the rotatable optical core or the elongate shaft. The imaging system can further comprise a translatable slide, and the rotation assembly can be positioned on the translatable slide. The rotation assembly can be constructed and arranged to be positioned independent of the position of the retraction assembly. The retraction assembly can be constructed and arranged to be positioned closer to the patient than the rotation assembly. The rotation assembly can provide motive force to the retraction assembly. The rotation assembly can comprise a drive cable that provides the motive force to the retraction assembly. The elongate shaft can be constructed and arranged to be retracted by the retraction assembly. The elongate shaft can comprise a proximal portion constructed and arranged to provide a service loop during retraction by the retraction assembly. The rotation assembly can rotate the rotatable optical core at a rate between 20 rps and 2500 rps. The rotation assembly can rotate the rotatable optical core at a rate of approximately 250 rps. The rotation assembly can rotate the rotatable optical core at a rate of up to 25,000 rps. The rotation assembly can be constructed and arranged to rotate the rotatable optical core at a variable rate of rotation. The imaging system can further comprise a sensor configured to produce a signal, and the rotational rate can be varied based on the sensor signal. The sensor signal represents a parameter selected from the group consisting of: tortuosity of vessel; narrowing of vessel; presence of clot; presence of an implanted device; and combinations thereof. The rotation assembly can be configured to allow an operator to vary the rate of rotation. The rotation assembly can be configured to automatically vary the rate of rotation. The rotation assembly can be configured to increase the rate of rotation when collecting image data from a target area. 
     In some embodiments, the imaging system further comprises a retraction assembly constructed and arranged to retract at least one of the rotatable optical core or the elongate shaft. The retraction assembly can be constructed and arranged to retract the rotatable optical core without retracting the elongate shaft. The retraction assembly can be constructed and arranged to retract both the rotatable optical core and the elongate shaft. The retraction assembly can be constructed and arranged to retract the rotatable optical core and the elongate shaft simultaneously. The retraction assembly can be constructed and arranged to retract the rotatable optical core and the elongate shaft in unison. The imaging probe can comprise a fluid between the rotatable optical core and the elongate shaft, and the retraction assembly can be constructed and arranged to perform the retraction while minimizing bubble formation in the fluid. The elongate shaft distal portion can comprise an optically transparent window, and the optical assembly can be positioned within the optically transparent window. The optically transparent window can comprise a length of less than or equal to 6 mm, less than or equal to 15 mm, or less than or equal to 20 mm. The optically transparent window can comprise a length of between 5 mm and 50 mm. The optically transparent window can comprise a length of approximately 10 mm, or approximately 12 mm. The optically transparent window can comprise a length of less than or equal to 4 mm. The optically transparent window can comprise a length of approximately 3 mm. The elongate shaft can comprise an outer diameter less than or equal to 0.025″. The elongate shaft can comprise an outer diameter less than or equal to 0.016″. The elongate shaft can comprise an outer diameter less than or equal to 0.014″. The retraction assembly can be constructed and arranged to retract the elongate shaft. The elongate shaft can comprise a proximal portion constructed and arranged to provide a service loop during retraction by the retraction assembly. The retraction assembly can comprise a telescoping retraction assembly. The telescoping retraction assembly can comprise a disposable motor. The imaging probe can comprise a Tuohy valve and the retraction assembly can operably engage the Tuohy valve during retraction. The retraction assembly can be configured to perform a retraction over a time period of between 0.1 seconds and 10 seconds. The retraction assembly can be configured to perform a retraction over a time period of approximately 4 seconds. The retraction assembly can be constructed and arranged to retract the at least one of the rotatable optical core or the elongate shaft over a distance of approximately 50 mm. The retraction assembly can be constructed and arranged to retract the at least one of the rotatable optical core or the elongate shaft over a distance of approximately 75 mm. The retraction assembly can be constructed and arranged to retract the at least one of the rotatable optical core or the elongate shaft over a distance of between 20 mm and 150 mm. The retraction assembly can be constructed and arranged to have its retraction distance selected by an operator of the system. The retraction assembly can be configured to perform the retraction at a rate between 3 mm/sec and 500 mm/sec. The retraction assembly can be configured to perform the retraction at a rate of approximately 50 mm/sec. The retraction assembly can be constructed and arranged to retract the at least one of the rotatable optical core or the elongate shaft at a variable rate of retraction. The imaging system can further comprise a sensor configured to produce a signal, and the retraction rate can be varied based on the sensor signal. The sensor signal can represent a parameter selected from the group consisting of: tortuosity of vessel; narrowing of vessel; presence of clot; presence of an implanted device; and combinations thereof. The retraction assembly can be configured to allow an operator to vary the retraction rate. The retraction assembly can be configured to automatically vary the retraction rate. The retraction assembly can be configured to decrease the rate of retraction when visualizing a target area. The imaging system can further comprise a catheter device comprising at least one of a vascular introducer or a guide catheter, the elongate shaft insertable through the catheter device, and the retraction assembly can be attachable to the catheter device. The imaging system can further comprise a catheter device comprising at least one of a vascular introducer or a guide catheter, the elongate shaft insertable through the catheter device, and the retraction assembly can be constructed and arranged to be positioned within 20 cm from the catheter device. 
     In some embodiments, the imaging system further comprises an imaging assembly configured to provide light to the rotatable optical core and to collect light from the rotatable optical core. The imaging assembly can comprise a light source configured to provide the light to the rotatable optical core. The imaging assembly can comprise a fiber optic rotary joint comprising an optical core configured to transmit light to the rotatable optical core and receive light from the rotatable optical core. The rotatable optical core can comprise a fiber with a first numerical aperture, and the imaging assembly can comprise an imaging assembly optical core with a second numerical aperture different than the first numerical aperture. The first numerical aperture can be approximately 0.16 and the second numerical aperture can be approximately 0.11. The imaging system can further comprise an adaptor configured to attach the imaging probe to the imaging assembly. The adaptor can comprise a lens assembly configured to match different numerical apertures. The adaptor can be configured to be used in multiple clinical procedures, but in less procedures than the imaging assembly. The adaptor can comprise a fiber with a numerical aperture chosen to minimize coupling losses between the imaging probe and the imaging assembly. The numerical aperture of the adaptor fiber can be approximately equal to the geometrical mean of the numerical aperture of the rotatable optical core and the numerical aperture of the imaging assembly. The numerical aperture of the adaptor fiber can be approximately equal to the arithmetic mean of the numerical aperture of the rotatable optical core and the numerical aperture of the imaging assembly. 
     In some embodiments, the imaging system further comprises an algorithm. The imaging system can further comprise a sensor configured to produce a signal, and the algorithm can be configured to analyze the sensor signal. The sensor signal can represent light collected from tissue. The sensor signal can represent a parameter related to: tortuosity of a blood vessel; narrowing of a blood vessel; presence of clot; presence of implanted device; and combinations thereof. 
     In some embodiments, the imaging system further comprises at least one guide catheter configured to slidingly receive the imaging probe. The imaging system can further comprise a flushing fluid delivery assembly configured to deliver a flushing fluid between the at least one guide catheter and the imaging probe. The flushing fluid can comprise saline and/or contrast (e.g. radiopaque contrast). The flushing fluid delivery assembly can be configured to deliver flushing fluid at a rate of approximately 6 ml/sec. The imaging system can further comprise the flushing fluid, and the flushing fluid can comprise iodinated contrast including an iodine concentration between 50 mg/ml and 500 mg/ml. The flushing fluid can comprise a fluid whose viscosity ranges from 1.0 Cp to 20 Cp at a temperature of approximately 37° C. The at least one guide catheter can comprise a first guide catheter comprising an optically transparent window, and the optical assembly can be constructed and arranged to be positioned within the optically transparent window. The first guide catheter can comprise a microcatheter with an inner diameter between 0.021″ and 0.027″. The first guide catheter can comprise a microcatheter with an inner diameter between 0.0165″ and 0.027″. The at least one guide catheter can further comprise a second guide catheter configured to slidingly receive the first guide catheter. 
     In some embodiments, the imaging system further comprises a torque tool constructed and arranged to operably engage the elongate shaft and subsequently apply torsional force to the elongate shaft. 
     According to another aspect of the present inventive concepts, methods of using the imaging system described herein are provided. 
     INCORPORATION BY REFERENCE 
     All publications, patents, and patent applications mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, features and advantages of embodiments of the present inventive concepts will be apparent from the more particular description of preferred embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same or like elements. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the preferred embodiments. 
         FIG. 1  is a schematic view of an imaging system comprising an imaging probe, an imaging console and one or more delivery devices, consistent with the present inventive concepts. 
         FIG. 1A  is magnified view of the distal portion of the shaft of the imaging probe of  FIG. 1 , consistent with the present inventive concepts. 
         FIG. 2  is a perspective view of an imaging probe comprising a metal coil in a distal portion of its shaft, consistent with the present inventive concepts. 
         FIG. 3  is a chart illustrating non-uniform rotational distortion. 
         FIG. 4  is a side sectional view of the distal portion of an imaging probe comprising a thin walled segment of shaft about an optical assembly, consistent with the present inventive concepts. 
         FIG. 5  is a side sectional view of the distal portion of an imaging probe comprising two fluids within the shaft of the imaging probe, consistent with the present inventive concepts. 
         FIG. 6  is a perspective view of an impeller, and a side sectional view of a distal portion of an imaging probe comprising the impeller, consistent with the present inventive concepts. 
         FIG. 7  is a side sectional view of a proximal portion of an imaging probe comprising a pressurization element, consistent with the present inventive concepts. 
         FIG. 8  is a side sectional anatomical view of a system comprising a guide catheter, an imaging probe and a treatment device, each of which having been placed into a vessel of the patient, consistent with the present inventive concepts. 
         FIG. 9  is a side sectional anatomical view of the system of  FIG. 8 , after the guide catheter has been partially retracted, consistent with the present inventive concepts. 
         FIG. 10  is a side sectional anatomical view of the system of  FIG. 8 , after the imaging probe has been advanced through the treatment device, consistent with the present inventive concepts. 
         FIG. 11  is a side sectional anatomical view of the system of  FIG. 8 , as the imaging probe is being retracted through the treatment device, consistent with the present inventive concepts. 
         FIG. 12  is a side sectional anatomical view of a system comprising an imaging probe and a treatment device, consistent with the present inventive concepts. 
         FIG. 13  is a side sectional view of an imaging probe comprising precision spacing between a rotatable optical core and a shaft, the spacing configured to provide capillary action to a fluid, consistent with the present inventive concepts. 
         FIG. 14  is partially assembled view of an imaging probe comprising a shaft, rotatable optical core, and torque shaft, consistent with the present inventive concepts. 
         FIG. 15A-C  are side sectional views of an imaging probe in a series of expansion steps of its shaft via an internal fluid, consistent with the present inventive concepts. 
         FIG. 16  is a side sectional view of the distal portion of an imaging probe comprising a distal marker positioned in reference to an optical assembly, consistent with the present inventive concepts. 
         FIG. 17  is a side sectional view of the distal portion of an imaging probe comprising two sealing elements, consistent with the present inventive concepts. 
         FIG. 18  is a side sectional view of the distal portion of an imaging device comprising a lens and deflector separated and connected by a projection, consistent with the present inventive concepts. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
     The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the inventive concepts. Furthermore, embodiments of the present inventive concepts may include several novel features, no single one of which is solely responsible for its desirable attributes or which is essential to practicing an inventive concept described herein. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. 
     It will be further understood that the words “comprising” (and any form of comprising, such as “comprise” and “comprises”), “having” (and any form of having, such as “have” and “has”), “including” (and any form of including, such as “includes” and “include”) or “containing” (and any form of containing, such as “contains” and “contain”) when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     It will be understood that, although the terms first, second, third etc. may be used herein to describe various limitations, elements, components, regions, layers and/or sections, these limitations, elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one limitation, element, component, region, layer or section from another limitation, element, component, region, layer or section. Thus, a first limitation, element, component, region, layer or section discussed below could be termed a second limitation, element, component, region, layer or section without departing from the teachings of the present application. 
     It will be further understood that when an element is referred to as being “on”, “attached”, “connected” or “coupled” to another element, it can be directly on or above, or connected or coupled to, the other element, or one or more intervening elements can be present. In contrast, when an element is referred to as being “directly on”, “directly attached”, “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). 
     It will be further understood that when a first element is referred to as being “in”, “on” and/or “within” a second element, the first element can be positioned: within an internal space of the second element, within a portion of the second element (e.g. within a wall of the second element); positioned on an external and/or internal surface of the second element; and combinations of one or more of these. 
     Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like may be used to describe an element and/or feature&#39;s relationship to another element(s) and/or feature(s) as, for example, illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and/or operation in addition to the orientation depicted in the figures. For example, if the device in a figure is turned over, elements described as “below” and/or “beneath” other elements or features would then be oriented “above” the other elements or features. The device can be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The term “and/or” where used herein is to be taken as specific disclosure of each of the two specified features or components with or without the other. For example “A and/or B” is to be taken as specific disclosure of each of (i) A, (ii) B and (iii) A and B, just as if each is set out individually herein. 
     As described herein, “room pressure” shall mean pressure of the environment surrounding the systems and devices of the present inventive concepts. Positive pressure includes pressure above room pressure or simply a pressure that is greater than another pressure, such as a positive differential pressure across a fluid pathway component such as a valve. Negative pressure includes pressure below room pressure or a pressure that is less than another pressure, such as a negative differential pressure across a fluid component pathway such as a valve. Negative pressure can include a vacuum but does not imply a pressure below a vacuum. As used herein, the term “vacuum” can be used to refer to a full or partial vacuum, or any negative pressure as described hereabove. 
     The term “diameter” where used herein to describe a non-circular geometry is to be taken as the diameter of a hypothetical circle approximating the geometry being described. For example, when describing a cross section, such as the cross section of a component, the term “diameter” shall be taken to represent the diameter of a hypothetical circle with the same cross sectional area as the cross section of the component being described. Shafts of the present inventive concepts, such as hollow tube shafts comprising a lumen and a wall, include an inner diameter (ID) equal to the diameter of the lumen, and an outer diameter (OD) defined by the outer surface of the shaft. 
     The terms “major axis” and “minor axis” of a component where used herein are the length and diameter, respectively, of the smallest volume hypothetical cylinder which can completely surround the component. 
     The term “transducer” where used herein is to be taken to include any component or combination of components that receives energy or any input, and produces an output. For example, a transducer can include an electrode that receives electrical energy, and distributes the electrical energy to tissue (e.g. based on the size of the electrode). In some configurations, a transducer converts an electrical signal into any output, such light (e.g. a transducer comprising a light emitting diode or light bulb), sound (e.g. a transducer comprising a piezo crystal configured to deliver ultrasound energy), pressure, heat energy, cryogenic energy, chemical energy; mechanical energy (e.g. a transducer comprising a motor or a solenoid), magnetic energy, and/or a different electrical signal (e.g. a Bluetooth or other wireless communication element). Alternatively or additionally, a transducer can convert a physical quantity (e.g. variations in a physical quantity) into an electrical signal. A transducer can include any component that delivers energy and/or an agent to tissue, such as a transducer configured to deliver one or more of: electrical energy to tissue (e.g. a transducer comprising one or more electrodes); light energy to tissue (e.g. a transducer comprising a laser, light emitting diode and/or optical component such as a lens or prism); mechanical energy to tissue (e.g. a transducer comprising a tissue manipulating element); sound energy to tissue (e.g. a transducer comprising a piezo crystal); chemical energy; electromagnetic energy; magnetic energy; and combinations of one or more of these. 
     As used herein, the term “patient site” refers to a location within the patient, such as a location within a body conduit such as a blood vessel (e.g. an artery or vein) or a segment of the GI tract (e.g. the esophagus, stomach or intestine), or a location with an organ. A “patient site” can refer to a location in the spine, such as within the epidural space or intrathecal space of the spine. A patient site can include a location including one or more of: an aneurysm; a stenosis; thrombus and/or an implant. 
     As used herein, the term “neural site” refers to a patient site proximate the brain, such as at a location within the neck, head or brain of a patient. A neural site can include a location proximate the brain including one or more of: an aneurysm; a stenosis; thrombus and/or an implant. 
     As used herein, the term “proximate” shall include locations relatively close to, on, in and/or within a referenced component or other location. 
     As used herein, the term “transparent” and “optically transparent” refer to a property of a material that is relatively transparent (e.g. not opaque) to light delivered and/or collected by one or more components of the imaging system or probe of the present inventive concepts (e.g. to collect image data of a patient site). 
     It is appreciated that certain features of the inventive concepts, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the inventive concepts which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. For example, it will be appreciated that all features set out in any of the claims (whether independent or dependent) can be combined in any given way. 
     The present inventive concepts include imaging systems comprising imaging probes and one or more delivery devices, such as delivery catheters and/or guidewires. The imaging probe can be configured to be positioned proximate a patient site and to collect image data from the patient site, such as a neural site, spinal site and/or other patient site as defined hereabove. The imaging probe comprises an elongate shaft including a lumen. In some embodiments, a rotatable optical core and a distally positioned optical assembly are positioned within the lumen of the probe shaft. A probe connector can be positioned on the proximal end of the elongate shaft, the connector surrounding at least a portion of the rotatable optical core (e.g. the proximal end of the rotatable optical core). The present inventive concepts further includes methods of introducing the imaging probe to a patient site, such as a neural site, using one or more delivery devices such as delivery catheters and/or guidewires. In some embodiments, the imaging probe is advanced through a delivery catheter to a patient site, without being advanced over a guidewire. 
     In some embodiments, the imaging probe comprises an inertial assembly configured to reduce rotational speed variances of the rotatable optical core. In some embodiments, the imaging probe comprises an impeller attached to the rotatable optical core and configured to resist rotation of the rotatable optical core, such as when the rotatable optical core is retracted. 
     In some embodiments, the imaging probe comprises a reinforcing assembly embedded into the elongate shaft. The reinforcing assembly can be configured to resist flexing of the elongate shaft and can comprise an optically transparent portion. 
     In some embodiments, the imaging probe comprises an elongate shaft in which at least a portion of the shaft includes a reduced inner diameter or otherwise comprises a portion in which the gap between the elongate shaft and the rotatable optical core is reduced. The reduced gap portion can be configured to reduce rotational speed variances of the rotatable optical core. In some embodiments, the reduced gap portion causes the elongate shaft to frictionally engage the rotatable optical core, providing a dampening force configured to reduce undesired speed variances of the rotatable optical core (e.g. to avoid undesired rotational speed variances in the attached optical assembly  130 ). Alternatively or additionally, a fluid can be positioned in the reduced gap portion (or other locations between the elongate shaft and the rotatable optical core), such as to similarly reduce undesired speed variances of the rotatable optical core. The fluid can comprise a shear-thinning fluid configured to avoid excessive loading on the rotatable optical core (e.g. during high speed rotation to prevent breaking of the rotatable optical core). 
     Systems, devices and methods of the present inventive concepts can be used to diagnose and/or treat stroke. Stroke is the 4th-leading cause of death in the United States and leads all ailments in associated disability costs. Stroke is a result of vascular disease and comes in two major forms: ischemic, in which the blood supply to the brain is interrupted; and hemorrhagic, in which a ruptured vessel leaks blood directly in the brain tissue. Both forms have associated high morbidity and mortality, such that improved diagnosis and treatment would have a significant impact on healthcare costs. 
     Imaging of the vessels is the primary diagnostic tool when planning and applying therapies such as: thrombolytic drugs or stent retrievers for clot removal (ischemic stroke); or coils, flow diverters and other devices for aneurysm repair (hemorrhagic stroke). External, non-invasive, imaging technologies, such as x-ray, angiography or MRI, are the primary imaging techniques used, but such techniques provide limited information such as vessel size and shape information with moderate resolution (e.g. approximately 200 μm resolution). Such levels of resolution do not permit the imaging of important smaller perforator vessels present in the vasculature. An inability to adequately image these vessels limits pre-procedural planning as well as acute assessment of therapeutic results. These imaging technologies are further limited in their effectiveness due to the shadowing and local image obliteration that can be created by the therapies themselves (e.g. in the case of implantation of one or more coils). Thus there is a desire to also perform intravascular imaging to examine the detailed morphology of the interior vessel wall and/or to better plan and assess the results of catheter based interventions. Currently, intravascular imaging techniques such as Intravascular Ultrasound (IVUS) and intravascular Optical Coherence Tomography (OCT) have been developed, but are only approved for use in the coronary arteries. IVUS is also used in the larger peripheral vasculature. Currently, intravascular imaging has not been extended for use into the neurological vessels except for the larger carotid arteries. The limitations of current technologies correlate to: the neurological vessel sizes can become very small, on the order of 1 mm in diameter or less, and the vessel tortuosity becomes quite high (e.g. if attempting to navigate the tortuous carotid sinus to reach and image the mid-cranial artery as well as branches and segments above). 
     Due to the fundamental limits of ultrasound resolution, especially the unavoidable beam spreading when small transducers are used, optical techniques are more appropriate. In particular, with the advent of new light sources such as broad band SLED&#39;s, visible wavelength laser diodes, and compact swept-frequency light sources, which are all compatible with single-mode fibers and interferometric imaging such as OCT, the use of optical techniques is highly advantageous both from a clinical performance as well as commercial viewpoint. The use of single mode fibers allows small diameter imaging catheters. 
     Referring now to  FIG. 1 , a schematic view of an imaging system comprising an imaging probe and one or more delivery devices is illustrated, consistent with the present inventive concepts. System  10  is constructed and arranged to collect image data and produce an image based on the recorded data, such as when system  10  comprises an Optical Coherence Tomogrophy (OCT) imaging system. System  10  comprises imaging probe  100 , and at least one delivery device, such as at least one delivery catheter  50  and/or at least one guidewire  60 . System  10  can further comprise an imaging console, console  200  which is configured to operably attach to imaging probe  100 . System  10  can further comprise a fluid injector, such as injector  300  which can be configured to inject one or more fluids, such as a flushing fluid, an imaging contrast agent (e.g. a radiopaque contrast agent, hereinafter “contrast”) and/or other fluid, such as injectate  305  shown. System  10  can further comprise an implant, such as implant  85  which can be implanted in the patient via implant delivery device  80 . System  10  can further comprise a device configured to treat the patient, treatment device  91 , which can be configured to dilate a stenotic site, remove stenotic material (e.g. thrombus) and/or otherwise treat a patient disease or disorder. System  10  can further comprise a second imaging device, such as imaging device  92  shown. 
     Imaging probe  100  comprises an elongate shaft, shaft  110 , comprising proximal end  111 , distal end  119 , proximal portion  111   a , a middle portion (mid portion  115 ), and distal portion  119   a . An optical connector, connector  102  is positioned on the proximal end  111  of shaft  110 , such as a connector configured to operably attach probe  100  to console  200 . Imaging probe  100  is configured to provide a patient image, such as a three dimensional (3D) image created when shaft  110  of imaging probe  100  is retracted. In some embodiments, imaging probe  100  and/or another component of system  10  is of similar construction and arrangement to the similar components described in applicant&#39;s co-pending U.S. Provisional Application Ser. No. 62/148,355, titled “Micro-Optic Probes for Neurology”, filed Apr. 29, 2015, the content of which is incorporated herein in its entirety for all purposes. 
     Imaging system  10  can comprise one or more imaging probes  100 , each suitable for imaging highly tortuous bodily lumens such as the mid-cranial artery, various peripheral arteries, and ducts of the endocrine system such as the liver (bile) and pancreatic ducts. Each imaging probe  100  can comprise very small cross-sections, typically less than 1 mm in OD and contain a rotatable optical core, core  120  comprising a single fiber optically connected on its distal end to an optical assembly, optical assembly  130 . Core  120  is rotated to create a high fidelity image of the luminal wall through which probe  100  is inserted. Imaging probe  100  and other components of imaging system  10  can be configured to facilitate uniform rotational velocity of core  120  while imaging probe  100  traverses difficult anatomies. Imaging system  10  can comprise multiple imaging probes  100  provided in a kit configuration, such as when two or more probes  100  comprise different characteristics (e.g. different length, diameter and/or flexibility) 
     Imaging probe  100  is constructed and arranged to collect image data from a patient site. Distal portion  119   a  can be configured to pass through the patient site, such as a patient site including occlusive material such as thrombus or a patient site including an implant. In some embodiments, probe  100  is constructed and arranged to collect image data from a neural site, such as a neural site selected from the group consisting of: artery of patient&#39;s neck; vein of patient&#39;s neck; artery of patient&#39;s head; vein of patient&#39;s head; artery of patient&#39;s brain; vein of patient&#39;s brain; and combinations of one or more of these. In some embodiments, probe  100  is constructed and arranged to collect image data from one or more locations along or otherwise proximate the patient&#39;s spine. In some embodiments, probe  100  is constructed and arranged to collect image data from tissue selected from the group consisting of: wall tissue of a blood vessel of the patient site; thrombus proximate the patient site; occlusive matter proximate the patient site; a blood vessel outside of blood vessel in which optical assembly  130  is positioned; tissue outside of blood vessel in which optical assembly  130  is positioned; extracellular deposits outside of the lumen of the blood vessel in which optical assembly  130  is positioned (e.g. within and/or outside of the blood vessel wall); and combinations of one or more of these. Alternatively or additionally, optical assembly  130  can be constructed and arranged to collect image data from an implanted device (e.g. a temporary or chronically implanted device), such as implant  85  described herebelow or a device previously implanted in the patient. In some embodiments, optical assembly  130  is constructed and arranged to collect image data regarding the placement procedure in which the implant was positioned within the patient (e.g. real time data collected during placement). Optical assembly  130  can be constructed and arranged to collect implant data comprising position and/or expansion data related to placement of an implant or other treatment device, such as a device selected from the group consisting of: a stent retriever (also known as a stentriever); an embolization device such as an embolization coil; an embolization coil delivery catheter; an occlusion device; a stent; a covered stent; a stent delivery device; a flow diverter; an aneurysm treatment device; an aneurysm delivery device; a balloon catheter; and combinations of one or more of these. In some embodiments, optical assembly  130  is constructed and arranged to collect data related to the position of an implant  85  or other device comprising a stimulation element, such as an electrode or other stimulation element positioned proximate the brain (e.g. an electrode positioned in the deep brain or other brain location) or a stimulation element positioned proximate the spine (e.g. stimulation element configured to treat pain by stimulating spine tissue). Implantation of implant  85  can be performed based on an analysis of collected image data (e.g. an analysis of collected image data by algorithm  240 ). The analysis can be used to modify an implantation parameter selected from the group consisting of: selection of the implantable device (e.g. selection of implant  85 ); selection of the implantable device porosity; selection of the implantable device metal coverage; selection of the implantable device pore density; selection of the implantable device diameter; selection of the implantable device length; selection of the location to implant the implantable device; a dilation parameter for expanding the implantable device once implanted; a repositioning of the implantable device once implanted; selection of a second implantable device to be implanted; and combinations thereof. An adjustment of the implantation can be performed based on one or more issues identified in the analysis, such as an issue selected from the group consisting of: malposition of implanted device; inadequate deployment of implanted device; presence of air bubbles; and combinations thereof. 
     In some embodiments, optical assembly  130  is constructed and arranged to collect data related to the position of a treatment device, such as treatment device  91  described herebelow, during a patient treatment procedure. 
     Delivery catheters  50  can comprise one or more delivery catheters, such as delivery catheters  50   a ,  50   b ,  50   c  through  50   n  shown. Delivery catheters  50  can include a vascular introducer, such as when delivery catheter  50   a  shown in  FIG. 1  comprises a vascular introducer, delivery catheter  50   INTRO . Other delivery catheters  50  can be inserted into the patient through delivery catheter  50   INTRO , after the vascular introducer is positioned through the skin of the patient. Two or more delivery catheters  50  can collectively comprise sets of inner diameters (IDs) and outer diameters (ODs) such that a first delivery catheter  50  slidingly receives a second delivery catheter  50  (e.g. the second delivery catheter OD is less than or equal to the first delivery catheter ID), and the second delivery catheter  50  slidingly receives a third delivery catheter  50  (e.g. the third delivery catheter OD is less than or equal to the second delivery catheter ID), and so on. In these configurations, the first delivery catheter  50  can be advanced to a first anatomical location, the second delivery catheter  50  can be advanced through the first delivery catheter to a second anatomical location distal or otherwise remote (hereinafter “distal”) to the first anatomical location, and so on as appropriate, using sequentially smaller diameter delivery catheters  50 . 
     Each delivery catheter  50  comprises a shaft  51  (e.g. shafts  51   a ,  51   b ,  51   c  and  51   n  shown), each with a distal end  59  (e.g. distal ends  59   a ,  59   b ,  59   c  and  59   n  shown). A connector  55  (e.g. connectors  55   a ,  55   b ,  55   c  and  55   n  shown) is positioned on the proximal end of each shaft  51 . Each connector  55  can comprise a Touhy or other valved connector, such as a valved connector configured to prevent fluid egress from the associated catheter  50  (with and/or without a separate shaft positioned within the connector  55 ). Each connector  55  can comprise a port  54  as shown on delivery catheters  50   b ,  50   c , and  50   n , such as a port constructed and arranged to allow introduction of fluid into the associated delivery catheter  50  and/or for removing fluids from an associated delivery catheter  50 . In some embodiments, a flushing fluid, as described herebelow, is introduced via one or more ports  54 , such as to remove blood or other undesired material from locations proximate optical assembly  130 . Port  54  can be positioned on a side of connector  55  and can include a luer fitting and a cap and/or valve. Shafts  51 , connectors  55  and ports  54  can each comprise standard materials and be of similar construction to commercially available introducers, guide catheters, diagnostic catheters, intermediate catheters and microcatheters used in interventional procedures. 
     Each delivery catheter  50  comprises a lumen  52  (reference number  52  shown on delivery catheter  50   a  but removed from the remaining delivery catheters  50  for illustrative clarity) extending from the connector  55  to the distal end  59  of shaft  51 . The diameter of each lumen  52  defines the ID of the associated delivery catheter  50 . Each delivery catheter  50  can be advanced over a guidewire (e.g. guidewire  60 ) via lumen  52 . In some embodiments, a delivery catheter  50  is configured for rapid exchange advancement and retraction over a guidewire, such as via a sidecar with a rapid exchange (Rx) guidewire lumen as is known to those of skill in the art. In some embodiments, probe  100  and at least one delivery catheter  50  are cooperatively constructed and arranged such that the delivery catheter  50  is advanced through a vessel, such as a blood vessel, and probe  100  is slidingly received by the delivery catheter  50  and advanced through the delivery catheter  50  to a location proximate a patient site PS to be imaged (e.g. a location just distal to, within and/or just proximate the patient site PS to be imaged). In some embodiments, a second delivery catheter  50  is slidingly received by a first delivery catheter  50 , and probe  100  is advanced through the second delivery catheter  50  to a location proximate a patient site PS to be imaged. In yet other embodiments, three or more delivery catheters  50  are coaxially inserted in each other, with probe  100  advanced through the innermost delivery catheter  50  to a location proximate a patient site PS to be imaged. In some embodiments, probe  100  is advanced through (e.g. through and beyond) one or more delivery catheters  50  without the use of a guidewire. 
     Delivery catheters  50  can comprise one or more delivery catheters selected from the group consisting of: an introducer; a vascular introducer; an introducer with an ID between 7 Fr and 9 Fr; a delivery catheter (also referred to as a guide catheter) for positioning through the aortic arch (e.g. such that its distal end is just distal or otherwise proximate the aortic arch) such as a delivery catheter with an ID between 5 Fr and 7 Fr or an ID of approximately 6.5 Fr; a delivery catheter (also referred to as an intermediate catheter) for insertion through a larger, previously placed delivery catheter, such as an intermediate delivery catheter with an ID of between 0.053″ and 0.070″; a delivery catheter (also referred to as a microcatheter) with an ID of between 0.0165″ and 0.027″; and combinations of one or more of these. In some embodiments, delivery catheters  50  comprise a first delivery catheter  50   INTRO  comprising an introducer, such as an introducer with an ID of between 7 Fr and 9 Fr or an ID of approximately 8 Fr. Delivery catheters  50  further can further comprise a second delivery catheter  50  constructed and arranged to be inserted into the first delivery catheter  50 , such as a second delivery catheter  50   GUIDE  constructed and arranged for positioning through the aortic arch and comprising an ID between 5 Fr and 7 Fr or an ID of approximately 6 Fr. Delivery catheters  50  can comprise a third delivery catheter  50  constructed and arranged to be inserted through the first delivery catheter  50   INTRO  and/or the second delivery catheter  50   GUIDE , such as a third delivery catheter  50   INTER  (e.g. an intermediate catheter) with an ID of between 0.053″ and 0.070″. Delivery catheters  50  can comprise a fourth delivery catheter  50   MICRO  constructed and arranged to be inserted through the first, second and/or third delivery catheters  50 , such as a fourth delivery catheter  50   MICRO  with an ID of between 0.0165″ to 0.027″. Imaging probe  100  can be constructed and arranged to be inserted through first, second, third and/or fourth delivery catheters  50 , such as when imaging probe  100  comprises an OD of less than 0.070″, such as when at least the distal portion of imaging probe  100  comprises an OD of less than or equal to 0.025″, 0.022″, 0.018″, 0.016″, 0.015″ or 0.014″. In some embodiments, at least the distal portion of imaging probe  100  comprises an ID of approximately 0.014″ (e.g. an ID between 0.012″ and 0.016″). In some embodiments, system  10  comprises a probe  100  and one or more delivery catheters  50 . 
     Each delivery catheter  50  can comprise an optically transparent segment, such as a segment relatively transparent to light transmitted and/or received by optical assembly  130 , such as transparent segment  57  shown on delivery catheter  50   n  and described herein. Transparent segment  57  can comprise a length of up to 50 cm, such as a length of between 1 cm and 15 cm, or a length of up to 2 cm or up to 5 cm. Transparent segment  57  can be part of a delivery catheter  50  comprising a microcatheter with an ID between 0.0165″ and 0.027″, or between 0.021″ and 0.027″. System  10  can comprise a first delivery catheter  50  that slidingly receives probe  100  and includes a transparent segment  57 , and a second delivery catheter  50  that slidingly receives the first delivery catheter  50 . 
     Each delivery catheter  50  can comprise a spring tip, not shown but such as spring tip  104  described herein as attached to shaft  110  of probe  100 . 
     Guidewires  60  can comprise one or more guidewires, such as guidewires  60   a ,  60   b  through  60   n  shown. Guidewires  60  can comprise one or more guidewires constructed and arranged to support advancement (e.g. intravascular advancement) of probe  100  (e.g. via a rapid exchange lumen in distal portion  119   a  of shaft  110 ) and/or a delivery catheter  50  into a patient site PS such as a neural site. Guidewires  60  can comprise one or more guidewires selected from the group consisting of: a guidewire with an OD between 0.035″ and 0.038″; a guidewire with an OD between 0.010″ and 0.018″; an access length guidewire such as a guidewire with a length of approximately 200 cm; an exchange length guidewire such as a guidewire with a length of approximately 300 cm; a guidewire with a length between 175 cm and 190 cm; a guidewire with a length between 200 cm and 300 cm and/or an OD between 0.014″ and 0.016″; a hydrophilic guidewire; a Stryker Synchro™ guidewire; a Terumo guidewire such as the Terumo Glidewire™ guidewire; a Terumo Traxcess™ guidewire; an X-Celerator™ guidewire; an X-Pedion™ guidewire; an Agility™ guidewire; a Bentson™ guidewire; a Coon™ guidewire; an Amplatz™ guidewire; and combinations of one or more of these. In some embodiments, system  10  comprises a probe  100  and one or more guidewires  60 . Guidewires  60  can comprise one or more visualizable portions, such as one or more radiopaque or ultrasonically reflective portions. 
     System  10  can comprise various sets and configurations of delivery catheters  50  and guidewires  60 . In some embodiments, delivery catheters  50  comprise a first delivery catheter  50   INTRO  comprising an introducer (e.g. a vascular introducer), and at least two delivery catheters  50  that are inserted through delivery catheter  50   INTRO , these catheters comprising corresponding different sets of IDs and ODs, such as to allow sequential insertion of each delivery catheter  50  through the lumen  52  of a previously placed delivery catheter  50 , as described in detail herein. In some embodiments, a first delivery catheter  50  is advanced over a first guidewire  60 , and a smaller OD delivery catheter  50  is subsequently advanced over a smaller OD guidewire  60  (e.g. after the first guidewire  60  is removed from the first delivery catheter  50  and replaced with the second guidewire  60 ). In some embodiments, after image data is collected by an imaging probe  100  positioned within a delivery catheter (e.g. after a retraction in which the image data is collected), imaging probe  100  is removed and replaced with a guidewire  60  over which an additional device can be placed (e.g. another delivery catheter  50 , a treatment device  91 , an implant delivery device  80  or other device). In some embodiments, probe  100 , one or more delivery catheters  50  and/or one or more guidewires  60  are inserted, advanced and/or retracted as described herein. 
     Probe  100 , one or more delivery catheters  50  and/or one or more guidewires  60  can be advanced to a patient site PS through one or more blood vessels (e.g. advancement of or more delivery catheters  50  over a guidewire  60  through one or more arteries or veins). Alternatively or additionally, probe  100 , one or more delivery catheters  50  and/or one or more guidewires  60  can be advanced to a patient site PS via a non-blood vessel lumen, such as the epidural and/or intrathecal space of the spine, or via another body lumen or space (e.g. also as can be performed over a guidewire  60 ). 
     In some embodiments, one or more delivery catheters  50  comprise a functional element  53  (e.g. functional elements  53   a ,  53   b ,  53   c  and  53   n  shown). Each functional element  53  can comprise one or more functional elements such as one or more sensors, transducers and/or other functional elements as described in detail herebelow. In some embodiments, shaft  110  comprises a length of at least 100 cm, at least 200 cm, at least 240 cm. In some embodiments, shaft  110  comprises a length of approximately 250 cm. In some embodiments, shaft  110  comprises a length less than or equal to 350 cm, less than or equal to 250 cm, or less than or equal to 220 cm. 
     In some embodiments, shaft  110  comprises an outer diameter (OD) between 0.005″ and 0.022″ along at least a portion of its length (e.g. at least a portion of distal portion  119   a ). In some embodiments, shaft  110  comprises an OD of approximately 0.0134″, an OD at or below 0.014″ or an OD at or below 0.016″, along at least a portion of its length (e.g. along a portion surrounding core  120  and/or optical assembly  130 , and/or along at least the most distal 10 cm, 20 cm or 30 cm of shaft  110 ). In these embodiments, imaging probe  100  can be configured to be advanced and/or retracted without a guidewire or delivery catheter (e.g. when optical assembly  130  and shaft  110  are retracted in unison during collection of image data). In some embodiments, shaft  110  comprises an OD that is less than 1 mm, or less than 500 μm, along at least a portion of its length. In some embodiments, shaft  110  comprises an OD that changes along its length. In some embodiments, distal portion  119   a  comprises a larger OD than an OD of mid portion  115 , such as when the portion of distal portion  119   a  surrounding optical assembly  130  has a larger OD than an OD of mid-portion  115 . In these embodiments, distal portion  119   a  can comprise a larger or similar ID as an ID of mid portion  115 . 
     In some embodiments, shaft  110  comprises an inner diameter (ID) between 0.004″ and 0.012″, along at least a portion of its length. In some embodiments, shaft  110  comprises an ID of approximately 0.0074″ along at least a portion of its length (e.g. along a portion surrounding core  120  and/or optical assembly  130 ). In some embodiments, shaft  110  comprises an ID that changes along its length. In some embodiments, distal portion  119   a  comprises a larger ID than an ID of mid portion  115 , such as when the portion of distal portion  119   a  surrounding optical assembly  130  has a larger ID than an ID of mid-portion  115 . 
     In some embodiments, shaft  110  comprises a wall thickness of 0.001″ to 0.005″, or a wall thickness of approximately 0.003″, along at least a portion of its length (e.g. along a portion surrounding core  120  and/or optical assembly  130 . In some embodiments, shaft  110  comprises a thinner wall surrounding at least a portion of optical assembly  130  (e.g. thinner than a portion of the wall surrounding core  120 ). 
     In some embodiments, shaft  110  distal portion  119   a  has a larger ID than mid portion  115  of shaft  110 , such as when mid portion  115  has an ID at least 0.002″ larger than the ID of distal portion  119   a . In these embodiments, the OD of mid portion  115  and the OD of distal portion  119   a  can be of similar magnitude. Alternatively, the OD of mid portion  115  can be different than the OD of distal portion  119   a  (e.g. the OD of distal portion  119   a  can be greater than the OD of mid portion  115 , such as when distal portion  119   a  is at least 0.001″ larger). 
     In some embodiments, imaging probe  100  comprises a stiffened portion, such as when imaging probe  100  comprises stiffening element  118 . Stiffening element  118  is positioned in, within and/or along at least a portion of shaft  110 . In some embodiments, stiffening element  118  is positioned within or on the inside surface of the wall of shaft  110 . In some embodiments, stiffening element  118  comprises a wire wound over core  120 . In some embodiments, stiffening element  118  terminates proximal to optical assembly  130 . Alternatively, stiffening element  118  can travel lateral to and/or potentially beyond optical assembly  130 , such as when the portion of stiffening element  118  comprises one or more optically transparent materials. 
     In some embodiments, distal portion  119   a  comprises a wall thickness that is less than the wall thickness of mid portion  115 . In some embodiments, distal portion  119   a  comprises a stiffer material than the materials of mid portion  115 , and/or distal portion  119   a  includes a stiffening element (e.g. stiffening element  118   a  shown in  FIG. 13  herebelow), such as when distal portion  119   a  comprises a wall thickness less than the wall thickness of mid portion  115 . 
     In some embodiments, probe  100  comprises a guidewire lumen, such as a rapid exchange guidewire lumen positioned in a sidecar  105  shown in  FIG. 1 . Sidecar  105  can comprise a length of less than 150 mm. Sidecar  105  can comprise a length of at least 15 mm, such as a length of approximately 25 mm. 
     In some embodiments, proximal portion  111   a  of shaft  110  is configured to be positioned in a service loop. Shaft  110  proximal portion  111   a  can comprise a different construction than mid portion  115  or different than distal portion  119   a . For example, proximal portion  111   a  can comprise a larger OD than mid portion  115  or a thicker wall than mid portion  115 . 
     In some embodiments, shaft  110  comprises an outer shaft and an inner “torque” shaft, which can be shorter than the outer shaft, such as is described herebelow in reference to  FIG. 14 . In some embodiments, the torque shaft terminates prior to a portion of probe  100  that enters the patient. 
     In some embodiments, system  10  comprises torque tool  320 , a tool that frictionally engages shaft  110  of probe  100  (e.g. from a lateral direction at a location along proximal portion  111   a ), and allows an operator to apply torsional force to shaft  110 . 
     Referring additionally to  FIG. 1A , a magnified view of distal portion  119   a  is illustrated, consistent with the present inventive concepts. A lumen  112  extends from proximal end  111  of shaft  110  to distal portion  119   a , ending at a location proximal to distal end  119 . Positioned within lumen  112  is a rotatable optical core, core  120 . An optical assembly, optical assembly  130  is positioned on the distal end of core  120 . Optical assembly  130  includes lens  131 , and a reflecting surface, reflector  132 . Optical assembly  130  is positioned within an optically translucent and/or effectively transparent window portion of shaft  110 , viewing portion  117 . Optical assembly  130  is constructed and arranged to collect image data through at least a portion of shaft  110 . In some embodiments, optical assembly  130  is further constructed and arranged to collect image data through at least a portion of an additional device, such as at least a portion of a shaft of a delivery catheter  50  (e.g. an optically transparent portion of a delivery catheter  50 , such as transparent segment  57  described herein). In  FIG. 1A , optional components sidecar  105  and stiffening element  118  have been removed for illustrative clarity. 
     In some embodiments, a fluid  190  is included in lumen  112  (e.g. in the space not occupied by core  120  and optical assembly  130 ), such as fluid  190   a  and fluid  190   b  shown in  FIG. 1A  where fluid  190   b  is positioned around optical assembly  130 , and fluid  190   a  is positioned around core  120  proximal to optical assembly  130 . Fluid  190  (e.g. fluid  190   b ) can comprise an optically transparent fluid. In some embodiments, fluid  190   a  and fluid  190   b  comprise similar materials. Alternatively or additionally, fluid  190   a  and fluid  190   b  can comprise dissimilar materials. In some embodiments, fluid  190   a  comprises a more viscous fluid than fluid  190   b . Fluid  190   a  and/or  190   b  (singly or collectively fluid  190 ) can be constructed and arranged to limit undesired variations in rotational velocity of core  120  and/or optical assembly  130 . In some embodiments, fluid  190  comprises a gel. In some embodiments, fluid  190  comprises a non-Newtonian fluid (e.g. a shear-thinning fluid) or other fluid whose viscosity changes with shear. Alternatively or additionally, fluid  190  can comprise a lubricant (e.g. to provide lubrication between core  120  and shaft  110 ). In some embodiments, fluid  190  comprises a shear-thinning fluid, and core  120  is rotated at a rate above 50 Hz, such as a rate above 100 Hz or 200 Hz. At higher rotation rates, if fluid  190  comprised a high viscosity Newtonian fluid, the resultant viscous drag during rotation of core  120  would result in a torsional load on core  120  which would cause it to break before the high rotation could be reached. However, a fluid  190  comprising a low viscosity Newtonian fluid is also not desired, as it would not provide sufficient dampening (e.g. would not provide adequate rotational speed control), such as during low-speed (“idle-mode’) imaging. For these reasons, probe  100  can comprise a fluid  190  that is a relatively high viscosity, shear-thinning (non-Newtonian) fluid, that provides sufficient loading during low speed rotation of core  120  and, due to its varying viscosity, avoid excessive loading during high speed rotation of core  120 . In some embodiments, fluid  190  comprises a shear-thinning fluid whose viscosity changes non-linearly (e.g. its viscosity rapidly decreases with increasing shear rate). In some embodiments, probe  100  comprises a reduced gap between shaft  110  and core  120  along at least a portion of shaft  110  (e.g. a portion of shaft  110  proximal to optical assembly  130 ), such as via a space reducing element as described herebelow in reference to  FIG. 16 . This gap can range from 20 μm to 200 μm (e.g. a constant or varied gap between 20 μm and 200 μm). Fluid  190  (e.g. a high viscosity, shear-thinning fluid) can be positioned (at least) in the reduced gap portion of shaft  110 . In this configuration, the amount of force applied to core  120  to reduce rotational variation is proportional to the shear stress and the length of shaft  110  in which fluid  190  and shaft  110  interact (the “interaction length”). Positioning of this interaction length relatively proximate to optical assembly  130  optimizes reduction of undesired rotational velocity variation of optical assembly  130  (e.g. since core  120  can have low torsional rigidity, dampening sufficiently far from optical assembly  130  will not provide the desired effect upon optical assembly  130 ). 
     In some embodiments, optical assembly  130  comprises a lens  131  with an OD that is greater than the diameter of lumen  112  of shaft  110  (e.g. greater than the diameter of at least a portion of lumen  112  that is proximal to optical assembly  130 ). The OD of lens  131  being greater than the diameter of lumen  112  prevents optical assembly  130  from translating within lumen  112 . For example, lens  131  can comprise a relatively large diameter aperture lens, such as to provide a small spot size while collecting large amounts of light (e.g. a lens  131  with an OD approaching up to 350 μm). Lumen  112  can be less than this diameter (e.g. less than 350 μm), such as to allow a reduced OD of shaft  110  proximal to optical assembly  130  (e.g. as shown in  FIGS. 4, 5, 6, 12, 13 and 16 ). In embodiments in which the OD of optical assembly  130  is greater than the diameter of lumen  112  at locations proximal to optical assembly  130 , the portion of shaft  110  surrounding optical assembly  130  has a larger OD and/or ID than the portions of shaft  110  proximal to optical assembly  130 . In these embodiments, both shaft  110  and optical assembly  130  are retracted simultaneously during collection of image data, since lumen  112  has too small a diameter to accommodate translation of optical assembly  130 . 
     In some embodiments, fluid  190  (e.g. fluid  190   a ) comprises a fluid with a viscosity between 10 Pa-S and 100,000 Pa-S. In these embodiments, fluid  190  can be configured to thin to approximately 3 Pa-S at a shear rate of approximately 100 s −1 . In some embodiments, fluid  190  (e.g. fluid  190   b ) comprises a viscosity between 1 Pa-S and 100 Pa-S, such as a viscosity of approximately 10 Pa-S. In some embodiments, fluid  190  is configured to cause core  120  to tend to remain centered within lumen  112  of shaft  110  as it rotates (e.g. due to the shear-thinning nature of fluid  190 ). In some embodiments, fluid  190   a  comprises a hydrocarbon-based material and/or silicone. In some embodiments, fluid  190   b  comprises mineral oil and/or silicone. In some embodiments, probe  100  includes one or more fluids  190  in at least the most distal 20 cm of shaft  110 . 
     In some embodiments, a seal is included in lumen  112 , sealing element  116 , constructed and arranged to provide a seal between core  120  and the walls of shaft  110  (e.g. when positioned within distal portion  119   a ). Sealing element  116  can allow for the rotation of core  120 , while preventing the mixing and/or migrating of fluids  190   a  and/or  190   b  (e.g. by resisting the flow of either around seal  116 ). In some embodiments, a sealing element  116  is positioned between 1 mm and  200  from optical assembly  130 , such as when sealing element  116  is positioned approximately 3 mm from optical assembly  130 . In some embodiments, sealing element  116  comprises two or more sealing elements, such as two or more sealing elements  116  which slidingly engage core  120  and/or optical assembly  130 . In some embodiments, probe  100  comprises a sealing element positioned in a proximal portion of shaft  110  (e.g. within or proximate connector  102 ), such as sealing element  151  described herebelow in reference to  FIG. 7 . 
     Sealing element  116  and/or  151  can comprise an element selected from the group consisting of: a hydrogel material; a compliant material; silicone; and combinations of one or more of these. In some embodiments, sealing element  116  and/or  151  can comprise a material bonded to shaft  110  with an adhesive, or simply an adhesive itself on shaft  110  (e.g. a UV cured adhesive or an adhesive configured not to bond with core  120 ). 
     In some embodiments, fluid  190  is configured to be pressurized, such as is described herein in reference to  FIG. 7 , such as to reduce bubble formation and/or bubble growth within fluid  190 . 
     Shaft  110  can comprise one or more materials, and can comprise at least a portion which is braided and/or includes one or more liners, such as a polyimide or PTFE liner. In some embodiments, at least the distal portion  119   a  of shaft  110  comprises an OD less than or equal to 0.025″, such as an OD less than or equal to 0.022″, 0.018″, 0.016″, 0.015″ or 0.014″. In some embodiments, shaft  110  comprises a material selected from the group consisting of: polyether ether ketone (PEEK); polyimide; nylon; fluorinated ethylene propylene (FEP); polytetrafluoroethylene (PTFE); polyether block amide (Pebax); and combinations of one or more of these. In some embodiments, shaft  110  comprises at least a portion including a braid including stainless steel and/or a nickel titanium alloy, such as a shaft  110  including a braid positioned over thin walled FEP or PTF. The braided portion can be coated with Pebax or other flexible material. In some embodiments, shaft  110  comprises at least a portion (e.g. a proximal portion) that is metal, such as a metal hypotube comprising stainless steel and/or nickel titanium alloy. In some embodiments, shaft  110  comprises a first portion that is a metal tube, and a second portion, distal to the first portion, that comprises a braided shaft. In some embodiments, shaft  110  comprises at least a portion that comprises a hydrophobic material or other material configured to reduce changes (e.g. changes in length) when exposed to a fluid. 
     Viewing portion  117  of shaft  110  can comprise one or more materials, and can comprise similar or dissimilar materials to a different portion of shaft  110 . Viewing portion  117  can comprise a similar ID and/or OD as one or more other portions of shaft  110 . In some embodiments, viewing portion  117  comprises an ID and/or OD that is larger than an ID and/or OD of shaft  110  at mid portion  115  of shaft  110 . Viewing portion  117  can comprise a similar or dissimilar flexibility as one or more other portions of shaft  110 . Viewing portion  117  can comprise one or more optically transparent materials selected from the group consisting of: Pebax; Pebax 7233; PEEK; amorphous PEEK; polyimide; glass; sapphire; nylon 12; nylon 66; and combinations of one or more of these. 
     In some embodiments, a flexible tip portion is positioned on the distal end of shaft  110 , such as spring tip  104  shown. Spring tip  104  can comprise a length of between 0.5 cm and 5 cm, such as a length of approximately lcm, 2 cm or 3 cm, or a length between 2 cm and 3 cm. At least a portion of spring tip  104  can be made visible to an imaging apparatus, such as by including a radiopaque material such as platinum or other material visible to an X-ray imaging device. Spring tip  104  can comprise a core comprising a material such as stainless steel. 
     In some embodiments, probe  100  and/or other components of system  10  comprise one or more markers (e.g. radiopaque or other visualizable markers), sensors, transducers or other functional elements such as: functional elements  53   a - n  of delivery catheters  50 ; functional element  83  of implant delivery device  80 ; functional element  93  of treatment device  91 ; functional elements  113   a  and  113   b  (singly or collectively functional element  113 , described herebelow) of shaft  110 ; functional element  123  of core  120 ; functional element  133  of optical assembly  130 ; functional element  203  of console  200 ; and functional element  303  of injector  300 . 
     In some embodiments, core  120  comprises a single mode glass fiber, such as a fiber with an OD between 40 μm and 175 μm, a fiber with an OD between 80 μm and 125 μm, a fiber with an OD between 60 μm and 175 μm, or a fiber with an OD of approximately 110 μm. Core  120  can comprise a material selected from the group consisting of: silica glass; plastic; polycarbonate; and combinations of one or more of these. Core  120  can comprise a fiber with a coating, such as a polyimide coating. Core  120  can comprise cladding material and/or coatings surrounding the fiber, such as are known to those of skill in the art. Core  120  can comprise a numerical aperture (NA) of at or above 0.11, such as an NA of approximately 0.16 or 0.20. In some embodiments, core  120  can comprise an NA (e.g. an NDA between 0.16 and 0.20) to significantly reduce bend-induced losses, such as would be encountered in tortuous anatomy. System  10  can be configured to rotate core  120  in a single direction (uni-directional rotation) or multi-directional (bi-directional rotation). 
     In some embodiments, probe  100  and other components of system  10  are configured to retract core  120  within shaft  110 . In these embodiments, probe  100  can be configured such that a material (e.g. fluid  190 ) is introduced into and within shaft  110  (e.g. between core  120  and shaft  110 ). The introduced material can be configured to provide a function selected from the group consisting of: index matching; lubrication; purging of bubbles; and combinations of one or more of these. 
     In some embodiments, optical assembly  130  comprises an OD between 80 μm and 500 μm, such as an OD of at least 125 μm, or an OD of approximately 150 μm. In some embodiments, optical assembly  130  comprises a length of between 200 μm and 3000 μm, such as a length of approximately 1000 μm. Optical assembly  130  can comprise one or more lenses, such as lens  131  shown, such as a GRIN lens and/or a ball lens. Optical assembly  130  can comprise a GRIN lens with a focal length between 0.5 mm and 10.0 mm, such as approximately 2.0 mm. Optical assembly  130  can comprise one or more reflecting elements, such as reflecting element  132  shown. 
     In some embodiments, optical assembly  130  comprises a lens  131  and a reflecting element  132  which is positioned offset from lens  131  via one or more connecting elements  137  as shown in  FIG. 18 . Connecting element  137  can comprise a tube (e.g. a heat shrink tube) surrounding at least a portion of lens  131  and reflecting element  132 . Connecting element  137  can comprise one or more elements selected from the group consisting of: tube; flexible tube; heat shrink; optically transparent arm; and combinations of one or more of these. Connecting element  137  can position reflecting element  132  at a distance of between 0.01 mm and 3.0 mm from lens  131 , such as at a distance between 0.01 mm and 1.0 mm. Reflecting element  132  can comprise a partial portion of a larger assembly that is cut or otherwise separated (e.g. cleaved) from the larger assembly during a manufacturing process used to fabricate optical assembly  130 . Use of the larger assembly can simplify handling during manufacturing. In some embodiments, the resultant reflecting element  132  comprises a shape-optimized reflector. Reflecting element  132  can comprise a segment of wire, such as a gold wire. In these embodiments, lens  131  can comprise a GRIN lens, such as a lens with an OD of approximately 150 μm and/or a length of approximately 1000 μm. In some embodiments, lens  131  further comprises a second lens, such as a coreless lens positioned proximal to and optically connected to the GRIN lens. 
     In some embodiments, imaging probe  100  comprises a reduced diameter portion (e.g. a reduced outer and/or inner diameter portion) along shaft  110 , at a location proximal to optical assembly  130 , such as is shown in  FIGS. 4, 5, 6, 12, 13 and 16 . In these embodiments, optical assembly  130  can comprise an OD that is larger than lumen  112  of shaft  110  (e.g. at a location proximal to optical assembly  130 ), such as to provide a larger lens  131  for improved imaging capability. In some embodiments, probe  100  comprises a space reducing element between shaft  110  and core  120 , such as is described herebelow in reference to elements  122  of  FIG. 16 . Functional elements  113  and/or  123  can comprise a space reducing element (e.g. a projection from shaft  110  and/or core  120 , respectively). 
     Console  200  can comprise an assembly, rotation assembly  210  constructed and arranged to rotate at least core  120 . Rotation assembly  210  can comprise one or more motors configured to provide the rotation, such as a motor selected from the group consisting of: DC motor; AC motor; stepper motor; synchronous motor; and combinations of one or more of these. Console  200  can comprise an assembly, retraction assembly  220 , constructed and arranged to retract at least shaft  110 . Retraction assembly  220  can comprise one or more motors or linear drive elements configured to provide the retraction, such as a component selected from the group consisting of: DC motor; AC motor; stepper motor; synchronous motor; gear mechanism, linear drive mechanism; magnetic drive mechanism; piston; pneumatic drive mechanism; hydraulic drive mechanism; and combinations of one or more of these. Rotation assembly  210  and/or retraction assembly  220  can be of similar construction and arrangement to those described in applicant&#39;s co-pending application U.S. Provisional Application Ser. No. 62/148,355, titled “Micro-Optic Probes for Neurology”, filed Apr. 29, 2015; the content of which is incorporated herein by reference in its entirety for all purposes. 
     Console  200  can comprise an imaging assembly  230  configured to provide light to optical assembly  130  (e.g. via core  120 ) and collect light from optical assembly  130  (e.g. via core  120 ). Imaging assembly  230  can include a light source  231 . Light source  231  can comprise one or more light sources, such as one or more light sources configured to provide one or more wavelengths of light to optical assembly  130  via core  120 . Light source  231  is configured to provide light to optical assembly  130  (via core  120 ) such that image data can be collected comprising cross-sectional, longitudinal and/or volumetric information related to the patient site PS or implanted device being imaged. Light source  231  can be configured to provide light such that the image data collected includes characteristics of tissue within the patient site PS being imaged, such as to quantify, qualify or otherwise provide information related to a patient disease or disorder present within the patient site PS being imaged. Light source  231  can be configured to deliver broadband light and have a center wavelength in the range from 800 nm to 1700 nm. The light source  231  bandwidth can be selected to achieve a desired resolution, which can vary according to the needs of the intended use of system  10 . In some embodiments, bandwidths are about 5% to 15% of the center wavelength, which allows resolutions of between 20 μm and 5 μm, respectively. Light source  231  can be configured to deliver light at a power level meeting ANSI Class 1 (“eye safe”) limits, though higher power levels can be employed. In some embodiments, light source  231  delivers light in the 1.3 μm band at a power level of approximately 20 mW. Tissue light scattering is reduced as the center wavelength of delivered light increases, however water absorption also increases. Light source  231  can deliver light at a wavelength approximating 1300 nm to balance these two effects. Light source  231  can be configured to deliver shorter wavelength light (e.g. approximately 800 nm light) to traverse patient sites to be imaged including large amounts of fluid. Alternatively or additionally, light source  231  can be configured to deliver longer wavelengths of light (e.g. approximately 1700 nm light), such as to reduce a high level of scattering within a patient site to be imaged. 
     Imaging assembly  230  (or another component of console  200 ) can comprise a fiber optic rotary joint (FORJ) configured to transmit light from light source  231  to core  120 , and to receive light from core  120 . In some embodiments, core  120  comprises a fiber with a first numerical aperture (NA), and imaging assembly  230  comprises an imaging assembly optical core with a second NA different than the first NA. For example, the first NA (the NA of of core  120 ) can comprise an NA of approximately 0.16 and the second NA (the NA of the imaging assembly optical core) can comprise an NA of approximately 0.11. In some embodiments, system  10  comprises an adaptor  310  configured to optically connect probe  100  to imaging assembly  230  (e.g. a single use or limited use disposable adaptor used in less procedures than imaging assembly  230 ). Adaptor  310  can comprise a lens assembly configured to “optically match” (e.g. to minimize coupling losses) different numerical apertures (such as the first and second NAs described hereabove). In some embodiments, adaptor  310  comprises a fiber with an NA that is the geometric mean of the two different NAs. In some embodiments, adaptor  310  comprises a fiber with an NA that is the arithmetic mean of the two different NAs. 
     Rotation assembly  210  can be constructed and arranged to rotate core  120  (and subsequently one or more components of optical assembly  130 ), at a rotational velocity of approximately 250 rps, or at a rotational velocity between 40 rps and 1000 rps. Rotation assembly  210  can be configured to rotate core  120  at a rate between 20 rps and 2500 rps. In some embodiments, rotation assembly  210  can be configured to rotate core  120  at a rate up to 25,000 rps. In some embodiments, the rotation rate provided by rotation assembly  210  is variable, such as when the rotation rate is varied based on a signal provided by a sensor of system  10 , such as when one or more of functional elements  53 ,  83 ,  93 ,  113 ,  123 ,  133 ,  203  and/or  303  comprise a sensor, and algorithm  240  is used to analyze one or more signals from the one or more sensors. In some embodiments, the sensor signal represents the amount of light collected from tissue or other target. In some embodiments, system  10  is configured to vary the rotation rate provided by rotation assembly  210  when the sensor signal correlates to a parameter selected from the group consisting of: tortuosity of vessel in which probe  100  is placed; narrowing of vessel in which probe  100  is placed; presence of clot proximate optical assembly  130 ; presence of an implanted device proximate optical assembly  130 ; and combinations thereof. In some embodiments, the rotation rate provided by rotation assembly  210  is varied by an operator of system  10  (e.g. a clinician). Alternatively or additionally, system  10  can vary the rotation rate provided by rotation assembly  210  automatically or at least semi-automatically (“automatically” herein), such as an automatic variation of a rotation rate as determined by one or more signals from one or more sensors as described hereabove. In some embodiments, rotation by rotation assembly  210  is increased (manually or automatically) when optical assembly  130  is collecting image data from a target area. 
     In some embodiments, rotation assembly  210  is constructed and arranged to rotate core  120  at one rate (e.g. at least 150 rps or approximately 250 rps) during image data collection (i.e. an “imaging mode”), and at a different rate (e.g. a slower rate, such as a rate between 30 rps and 150 rps), during a “preview mode”. During preview mode, a “positioning operation” can be performed in which optical assembly  130  is linearly positioned and/or a flush procedure can be initiated. The positioning operation can be configured to visualize bright reflections (e.g. via one or more implants such as an implanted stent, flow director and/or coils). Alternatively or additionally, the preview mode can be configured to allow an operator (e.g. a clinician) to confirm that optical assembly  130  has exited the distal end  59  of a surrounding delivery catheter  50 . The preview mode can be configured to reduce time and acceleration forces associated with rotating core  120  at a velocity to accommodate image data collection (e.g. a rotational velocity of at least 150 rps or approximately 250 rps). 
     Retraction assembly  220  can be constructed and arranged to retract optical assembly  130  (e.g. by core  120  and/or retracting shaft  100 ) at a retraction rate of approximately 40 mm/sec, such as a retraction rate between 3 mm/sec and 500 mm/sec (e.g. between 5 mm/sec and 60 mm/sec, or approximately 50 mm/sec). Retraction assembly  220  can be constructed and arranged to perform a pullback of between 20 mm and 150 mm (e.g. a pullback of approximately 50 mm or 75 mm), such as a pullback that is performed in a time period between 0.1 seconds and 15.0 seconds, such as a period between 0.1 and 10 seconds, or a period of approximately 4 seconds. In some embodiments, pullback distance and/or pullback rate are operator selectable and/or variable (e.g. manually or automatically). In some embodiments, the pullback distance and/or pullback rate provided by retraction assembly  220  is variable, such as when the pullback distance and/or pullback rate is varied based on a signal provided by a sensor of system  10 , such as when one or more of functional elements  53 ,  83 ,  93 ,  113 ,  133 ,  203  and/or  303  comprise a sensor, and algorithm  240  is used to analyze one or more signals from the one or more sensors. In some embodiments, the sensor signal represents the amount of light collected from tissue or other target. In some embodiments, system  10  is configured to vary the pullback distance and/or pullback rate provided by retraction assembly  220  when the sensor signal correlates to a parameter selected from the group consisting of: tortuosity of vessel in which probe  100  is placed; narrowing of vessel in which probe  100  is placed; presence of clot proximate optical assembly  130 ; presence of an implanted device proximate optical assembly  130 ; and combinations thereof. In some embodiments, the pullback distance and/or pullback rate provided by retraction assembly  220  is varied by an operator of system  10  (e.g. a clinician). Alternatively or additionally, system  10  can vary the pullback distance and/or pullback rate provided by retraction assembly  210  automatically or at least semi-automatically (“automatically” herein), such as an automatic variation of a pullback distance and/or pullback rate as determined by one or more signals from one or more sensors as described hereabove. In some embodiments, pullback distance and/or pullback rate by retraction assembly  220  is varied (increased or decreased, manually or automatically) when optical assembly  130  is collecting image data from a target area. 
     In some embodiments, retraction assembly  220  and probe  100  are configured such that during image data collection, retraction assembly  220  retracts core  120  without causing translation to shaft  110  (e.g. core  120  retracts within lumen  112  of shaft  110 ). 
     In some embodiments, retraction assembly  220  and probe  100  can be configured such that during image data collection, retraction assembly  220  retracts core  120  and shaft  110  in unison. In these embodiments, shaft  110  can comprise a relatively short viewing window, viewing portion  117  surrounding optical assembly  130 , since optical assembly  130  does not translate within shaft  110 . For example, in these embodiments, viewing portion  117  can comprise a length less than or equal to 20 mm, less than or equal to 15 mm, less than or equal to 6 mm, or less than or equal to 4 mm, such as when viewing portion  117  comprises a length of approximately 3 mm. In some embodiments, viewing portion  117  comprises a length between 5 mm and 50 mm, such as a length of approximately 10 mm or approximately 12 mm. In these embodiments in which optical assembly  130  does not translate within shaft  110 , shaft  110  diameter (ID and/or OD) can be reduced at locations proximal to viewing portion  117 , such as when the OD of shaft  110  (at least the portion of shaft  110  surrounding and proximate optical assembly), comprises a diameter of less than or equal to 0.025″, 0.016″ or 0.014″. Alternatively or additionally, in these embodiments in which optical assembly  130  does not translate within shaft  110 , portions of the shaft proximal to optical assembly  130  (e.g. proximal to viewing portion  117 ) can include a non-transparent construction, such as a braided construction or a construction using materials such as metal tubing (e.g. nitinol or stainless steel hypotube), such as to improve pushability of probe  100 . 
     Retraction assembly  220  can be configured to minimize formation of bubbles within any fluid (e.g. fluid  190 ) within shaft  110 , such as by retracting shaft  110  and core  120  in unison, or by retracting core  120  at a precision rate to avoid bubble formation. When shaft  110  is retracted, proximal portion  111   a  can be configured to be positioned in a service loop. Retraction assembly  220  can comprise a translatable slide, and rotation assembly  210  can be positioned on the translatable slide. 
     Retraction assembly  220  can comprise a telescoping retraction assembly. Retraction assembly  220  can comprise a motor, such as a single use or otherwise sometimes disposable motor, such as a disposable motor that is part of a telescoping retraction assembly. 
     In some embodiments, rotation assembly  210  can be independently positioned in reference to retraction assembly  220 . In some embodiments, retraction assembly  220  is configured to be positioned closer to the patient than the rotation assembly  210  is positioned (e.g. when retraction assembly  220  is positioned within 20 cm of a vascular introducer or other patient introduction device through which probe  100  is inserted). In some embodiments, retraction assembly  220  is configured to removably attach to a patient introduction device, such as to connect to a Touhy connector of a vascular introducer through which probe  100  is inserted, such as a delivery catheter  50  described herein. 
     In some embodiments, retraction assembly  220  receives “motive force” from console  200 , such as via drive shaft  211  that may be operably attached to rotation assembly  210  as shown in  FIG. 1 . 
     Console  200  can comprise a display  250 , such as a display configured to provide one or more images (e.g. video) based on the collected image data. Imaging assembly  230  can be configured to provide an image on display  250  with an updated frame rate of up to approximately 250 frames per second (e.g. similar to the rotational velocity of core  120 ). Display  250  can provide a 2-D and/or 3-D representation of 2-D and/or 3-D data. 
     Console  200  can comprise one or more functional elements, such as functional element  203  shown in  FIG. 1 . Functional element  203  can comprise one or more functional elements such as one or more sensors, transducers and/or other functional elements as described in detail herebelow. 
     Console  200  can comprise an algorithm, such as algorithm  240  shown, which can be configured to adjust (e.g. automatically and/or semi-automatically adjust) one or more operational parameters of system  10 , such as an operational parameter of console  200 , probe  100  and/or a delivery catheter  50 . Alternatively or additionally, algorithm  240  can be configured to adjust an operational parameter of a separate device, such as injector  300  or implant delivery device  80  described herebelow. In some embodiments, algorithm  240  is configured to adjust an operational parameter based on one or more sensor signals, such as a sensor signal provided by a sensor-based functional element of the present inventive concepts as described herein (e.g. a signal provided by one or more of functional elements  53 ,  83 ,  93 ,  113 ,  123 ,  203  and/or  303 ). Algorithm  240  can be configured to adjust an operational parameter selected from the group consisting of: a rotational parameter such as rotational velocity of core  120  and/or optical assembly  130 ; a retraction parameter of shaft  110  and/or optical assembly  130  such as retraction velocity, distance, start position, end position and/or retraction initiation timing (e.g. when retraction is initiated); a position parameter such as position of optical assembly  130 ; a line spacing parameter such as lines per frame; an image display parameter such as a scaling of display size to vessel diameter; a probe  100  configuration parameter; an injectate  305  parameter such as a saline to contrast ratio configured to determine an appropriate index of refraction; a light source  231  parameter such as power delivered and/or frequency of light delivered; and combinations of one or more of these. In some embodiments, algorithm  240  is configured to adjust a retraction parameter such as a parameter triggering the initiation of the pullback, such as a pullback that is initiated based on a parameter selected from the group consisting of: lumen clearing; injector  300  signal; change in image data collected (e.g. a change in an image, based on the image data collected, that correlates to proper evacuation of blood from around optical assembly  130 ); and combinations of one or more of these. In some embodiments, algorithm  240  is configured to adjust a probe  100  configuration parameter, such as when algorithm  240  identifies (e.g. automatically identifies via an RF or other embedded ID) the attached probe  100  and adjusts a parameter such as arm path length and/or other parameter as listed above. 
     Injector  300  can comprise a power injector, syringe pump, peristaltic pump or other fluid delivery device configured to inject a contrast agent, such as radiopaque contrast, and/or other fluids. In some embodiments, injector  300  is configured to deliver contrast and/or other fluid (e.g. contrast, saline and/or Dextran). In some embodiments, injector  300  delivers fluid in a flushing procedure as described herebelow. In some embodiments, injector  300  delivers contrast or other fluid through a delivery catheter  50  with an ID of between 5 Fr and 9 Fr, a delivery catheter  50  with an ID of between 0.53″ to 0.70″, or a delivery catheter  50  with an ID between 0.0165″ and 0.027″. In some embodiments, contrast or other fluid is delivered through a delivery catheter as small as 4 Fr (e.g. for distal injections). In some embodiments, injector  300  delivers contrast and/or other fluid through the lumen of one or more delivery catheters  50 , while one or more smaller delivery catheters  50  also reside within the lumen  52 . In some embodiments, injector  300  is configured to deliver two dissimilar fluids simultaneously and/or sequentially, such as a first fluid delivered from a first reservoir and comprising a first concentration of contrast, and a second fluid from a second reservoir and comprising less or no contrast. Injector  300  can comprise one or more functional elements, such as functional element  303  shown in  FIG. 1 . Functional element  303  can comprise one or more functional elements such as one or more sensors, transducers and/or other functional elements as described in detail herebelow. 
     Implant  85  can comprise an implant (e.g. a temporary or chronic implant) for treating one or more of a vascular occlusion or an aneurysm. In some embodiments, implant  85  comprises one or more implants selected from the group consisting of: a flow diverter; a Pipeline™ flow diverter; a Surpass™ flow diverter; an embolization coil; a stent; a Wingspan™ stent; a covered stent; an aneurysm treatment implant; and combinations of one or more of these. Delivery device  80  can comprise a catheter or other tool used to deliver implant  85 , such as when implant  85  comprises a self-expanding or balloon expandable portion. Implant delivery device  80  can comprise a functional element, such as functional element  83  shown in  FIG. 1 . Functional element  83  can comprise one or more functional elements such as one or more sensors, transducers and/or other functional elements as described in detail herebelow. In some embodiments, system  10  comprises a probe  100 , one or more implants  85  and/or one or more implant delivery devices  80 , such as is described in applicant&#39;s co-pending application U.S. Provisional Application Ser. No. 62/212,173, titled “Imaging System includes Imaging Probe and Delivery Devices”, filed Aug. 31, 2015; the content of which is incorporated herein by reference in its entirety for all purposes. In some embodiments, probe  100  is configured to collect data related to implant  85  and/or implant delivery device  80  (e.g. implant  85  and/or implant delivery device  80  anatomical location, orientation and/or other configuration data), after implant  85  and/or implant delivery device  80  has been inserted into the patient. 
     Treatment device  91  can comprise an occlusion treatment or other treatment device selected from the group consisting of: a balloon catheter constructed and arranged to dilate a stenosis or other narrowing of a blood vessel; a drug eluting balloon; an aspiration catheter; a sonolysis device; an atherectomy device; a thrombus removal device such as a stent retriever device; a Trevo™ stentriever; a Solitaire™ stentriever; a Revive™ stentriever; an Eric™ stentriever; a Lazarus™ stentriever; a stent delivery catheter; a microbraid implant; an embolization system; a WEB™ embolization system; a Luna™ embolization system; a Medina™ embolization system; and combinations of one or more of these. In some embodiments, treatment device  91  comprises a therapeutic device selected from the group consisting of: stent retriever; embolization coil; embolization coil delivery catheter; stent; covered stent; stent delivery device; aneurysm treatment implant; aneurysm treatment implant delivery device; flow diverter; balloon catheter; and combinations thereof. In some embodiments, probe  100  is configured to collect data related to treatment device  91  (e.g. treatment device  91  location, orientation and/or other configuration data), after treatment device  91  has been inserted into the patient. Treatment device  91  can comprise a functional element, such as functional element  93  shown in  FIG. 1 . 
     2 nd  Imaging device  92  can comprise an imaging device such as one or more imaging devices selected from the group consisting of: an X-ray; a fluoroscope such as a single plane or biplane fluoroscope; a CT Scanner; an MM; a PET Scanner; an ultrasound imager; and combinations of one or more of these. 
     Functional elements  53 ,  83 ,  93 ,  113 ,  123 ,  133 ,  203 , and/or  303  can each comprise one or more sensors, transducers and/or other functional elements, as described in detail herebelow. 
     In some embodiments, a functional element  113  is positioned proximate optical assembly  130  (e.g. functional element  113   b  positioned distal to optical assembly  130  as shown in  FIG. 1A , at the same axial location as optical assembly  130  and/or proximal to optical assembly  130 ). In some embodiments, imaging probe  100  comprises functional element  113   a  shown in  FIG. 1 . Functional element  113   a  is shown positioned on a proximal portion of shaft  110 , however it can be positioned at another probe  100  location such as on, in and/or within connector  102 . Functional elements  113   a  and/or  113   b  (singly or collectively functional element  113 ) can each comprise one or more functional elements such as one or more sensors, transducers and/or other functional elements as described in detail herebelow. 
     In some embodiments, functional element  53 ,  83 ,  93 ,  113 ,  123 ,  133 ,  203  and/or  303  comprise a sensor, such as a sensor configured to provide a signal related to a parameter of a system  10  component and/or a sensor configured to provide a signal related to a patient parameter. Functional element  53 ,  83 ,  93 ,  113 ,  123 ,  133 ,  203  and/or  303  can comprise one or more sensors selected from the group consisting of: a physiologic sensor; a pressure sensor; a strain gauge; a position sensor; a GPS sensor; an accelerometer; a temperature sensor; a magnetic sensor; a chemical sensor; a biochemical sensor; a protein sensor; a flow sensor such as an ultrasonic flow sensor; a gas detecting sensor such as an ultrasonic bubble detector; a sound sensor such as an ultrasound sensor; and combinations of one or more of these. In some embodiments, functional element  53 ,  83 ,  93 ,  113 ,  123 ,  133 ,  203  and/or  303  can comprise one or more physiologic sensors selected from the group consisting of: a pressure sensor such as a blood pressure sensor; a blood gas sensor; a flow sensor such as a blood flow sensor; a temperature sensor such as a blood or other tissue temperature sensor; and combinations of one or more of these. In some embodiments, algorithm  240  is configured to process the signal received by a sensor, such as a signal provided by a sensor as described herein. In some embodiments, functional element  53 ,  83 ,  93 ,  113 ,  123  and/or  133  comprises a position sensor configured to provide a signal related to a vessel path (e.g. a vessel lumen path) in three dimensions. In some embodiments, functional element  53 ,  83 ,  93 ,  113 ,  123  and/or  133  comprises a magnetic sensor configured to provide a signal for positioning optical assembly  130  relative to one or more implanted devices (e.g. one or more implants  85  described herein comprising a ferrous or other magnetic portion). In some embodiments, functional element  53 ,  83 ,  93 ,  113 ,  123  and/or  133  comprises a flow sensor, such as a flow sensor configured to provide a signal related to blood flow through a blood vessel of the patient site PS (e.g. blood flow through a stenosis or other partially occluded segment of a blood vessel). In these embodiments, algorithm  240  can be configured to assess blood flow (e.g. assess the significance of an occlusion), such as to provide information to a clinician regarding potential treatment of the occlusion. In some embodiments, optical assembly  130  comprises functional element  113 , such as when optical assembly  130  is constructed and arranged as a sensor that provides a signal related to blood flow. In some embodiments, functional element  53 ,  83 ,  93 ,  113 ,  123  and/or  133  comprises a flow sensor configured to provide a signal used to co-register vessel anatomic data to flow data, which can be used to provide pre and post intervention modeling of flow (e.g. aneurysm flow), assess risk of rupture and/or otherwise assess adequacy of the intervention. In some embodiments, functional element  53 ,  83 ,  93 ,  113 ,  123  and/or  133  comprises an ultrasound sensor configured to provide a signal (e.g. image or frequency data) which can be co-registered with near field optical derived information provided by optical assembly  130 . In some embodiments, functional element  53 ,  83 ,  93  and/or  113  are configured to be deployed by their associated device, such as to implant the functional element (e.g. a sensor-based functional element) into the patient. The implantable functional element  53 ,  83 ,  93  and/or  113  can comprise microchip and/or MEMS components. The implantable functional element  53 ,  83 ,  93  and/or  113  can comprise at least a portion that is configured to be visualized (e.g. by image data collected by probe  100  and/or a separate imaging device such as second imaging device  92 . 
     In some embodiments, functional element  53 ,  83 ,  93 ,  113 ,  123 ,  133 ,  203  and/or  303  comprise one or more transducers selected from the group consisting of: a heating element such as a heating element configured to deliver sufficient heat to ablate tissue; a cooling element such as a cooling element configured to deliver cryogenic energy to ablate tissue; a sound transducer such as an ultrasound transducer; a vibrational transducer; and combinations of one or more of these. 
     In some embodiments, functional element  53 ,  83 ,  93  and/or  113  comprises a pressure release valve configured to prevent excessive pressure from accumulating in the associated device. In some embodiments, functional element  53 ,  83 ,  93  and/or  113  comprises one or more sideholes, such as one or more sideholes used to deliver a fluid in a flushing procedure as described herein. 
     In some embodiments, functional element  53 ,  83 ,  93 ,  113 ,  123 ,  133 ,  203  and/or  303  comprise a visualizable marker, such as when functional element  53 ,  83 ,  93  and/or  113  comprise a marker selected from the group consisting of: radiopaque marker; ultrasonically reflective marker; magnetic marker; ferrous material; and combinations of one or more of these. 
     Probe  100  is configured to collect image data, such as image data collected during rotation and/or retraction of optical assembly  130 . Optical assembly  130  can be rotated by rotating core  120 . Optical assembly  130  can be retracted by retracting shaft  110 . Optical assembly  130  can collect image data while surrounded by a portion of a shaft of a delivery catheter  50  (e.g. when within a transparent segment  57  of a delivery catheter) and/or when there is no catheter  50  segment surrounding optical assembly  130  (e.g. when optical assembly  130  has been advanced beyond the distal ends  59  of all delivery catheters  50  into which probe  100  is inserted). 
     During collection of image data, a flushing procedure can be performed, such as by delivering one or more fluids, injectate  305  (e.g. as propelled by injector  300  or other fluid delivery device), to remove blood or other somewhat opaque material (hereinafter non-transparent material) proximate optical assembly  130  (e.g. to remove non-transparent material between optical assembly  130  and a delivery catheter and/or non-transparent material between optical assembly  130  and a vessel wall), such as to allow light distributed from optical assembly  130  to reach and reflectively return from all tissue and other objects to be imaged. In these flushing embodiments, injectate  305  can comprise an optically transparent material, such as saline. Injectate  305  can comprise one or more visualizable materials, as described herebelow. Injectate  305  can be delivered by injector  300  as described hereabove. 
     Flush rates required for providing clearance around optical assembly  130  can scale inversely with the viscosity of the flush medium. This mathematical relationship can be driven by the downstream draining of the flush medium in the capillary bed. If the capillary bed drains slowly, it is easier to maintain the upstream flush at a pressure at or slightly above native blood pressure, such that fresh blood will not enter the vessel being imaged (e.g. at a location proximate optical assembly  130 ). Conversely, if the capillary bed drains rapidly, the flush rate will need to increase correspondingly. Since saline (a standard flush medium) has a viscosity about ⅓ that of blood (e.g. 1 Cp vs 3.3 Cp), roughly three times normal flow rate will be required to clear a vessel (in the area proximate optical assembly  130 ), and such flow rates can pose a risk to vessel integrity. As an alternative, contrast media (e.g. radiopaque contrast media) can be used for flushing. Contrast material has a high viscosity (due to its high iodine concentrations, typically a concentration of approximately 300 mg/ml). System  10  can comprise a flushing fluid comprising contrast, such as contrast with a concentration between 50 mg/ml to 500 mg/ml of iodine (e.g. correlating to viscosities approximately two to five times that of blood). System  10  can comprise a flushing fluid (e.g. a radiopaque or other visualizable flushing fluid) with a viscosity between 1.0 Cp and 20 Cp (e.g. at a temperature of approximately 37° C.). 
     Alternative or in addition to its use in a flushing procedure, injectate  305  can comprise material configured to be viewed by second imaging device  92 , such as when injectate  305  comprise a contrast material configured to be viewed by a second imaging device  92  comprising a fluoroscope or other X-ray device; an ultrasonically reflective material configured to be viewed by a second imaging device  92  comprising an ultrasound imager; and/or a magnetic material configured to be viewed by a second imaging device  92  comprising an MRI. 
     Injectate  305  can be delivered by one or more delivery catheters  50  (e.g. in the space between a first delivery catheter  50  and an inserted delivery catheter  50 , or in the space between a delivery catheter  50  and an inserted probe  100 ). Injectate  305  delivered in a flushing procedure (or other injectate  305  delivery procedure) can be delivered out the distal end  59  of a delivery catheter  50  (e.g. a distal end  59  positioned proximal to optical assembly  130 ), such as is described in applicant&#39;s co-pending U.S. Provisional Application Ser. No. 62/212,173, titled “Imaging System includes Imaging Probe and Delivery Devices”, filed Aug. 31, 2015, the content of which is incorporated herein by reference in its entirety for all purposes. Alternatively or additionally, any delivery catheter  50  can comprise one or more sideholes passing through a portion of the associated shaft  51 , such as sideholes  58  shown positioned on a distal portion of delivery catheter  50   c . In some embodiments, a delivery catheter  50  comprises a microcatheter comprising sideholes  58  positioned on a distal portion, such as a microcatheter with an ID less than 0.027″ (e.g. a microcatheter with an ID between 0.016″ and 0.027″ or an ID between 0.021″ and 0.027″). In some embodiments, flushing fluid is delivered towards optical assembly  130  from both sideholes  58  and from the distal end  59  of a delivery catheter  50 . Sideholes  58  can be constructed and arranged to allow a flushing fluid to pass from within shaft  51  and through the sideholes  58 , such as when a separate shaft is inserted within the delivery catheter  50  (e.g. a shaft  51  of an additional delivery catheter  50  or the shaft  110  of probe  100 ). Delivery of flushing fluid through sideholes  58  and/or the distal end of the delivery catheter  50  can be performed to clear blood from an area from a luminal segment surrounding optical assembly  130 , such as during collecting of image data. 
     In some embodiments, the delivery of injectate  305  during a flushing procedure is based on a parameter selected from the group consisting of: a pre-determined volume of injectate to be delivered; a pre-determined time during which injectate is delivered; an amount of time of delivery including a time extending from a time prior to retraction of shaft  110  that continued until the collecting of the image data has been completed (e.g. completion of retraction of shaft  110 ); and combinations of one or more of these. In some embodiments, injector  300  delivers fluid in a flushing procedure with an approximate flow profile selected from the group consisting of: contrast (e.g. between 20% and 100% contrast that can be mixed with saline) at 5 ml/second for 6 seconds (e.g. for imaging of a carotid artery including 4 seconds of collecting image data); contrast (e.g. between 20% and 100% contrast that can be mixed with saline) at 4 ml/second for 6 seconds (e.g. for imaging of a vertebral artery including 4 seconds of collecting image data); and combinations of one or more of these. In some embodiments, a flushing procedure comprises delivery of injectate  305  (e.g. via one or more delivery catheters  50 ) for between 2 seconds to 8 seconds, such as a delivery of injectate for approximately 4 seconds (e.g. to purge blood or other non-transparent fluid from a luminal segment of a blood vessel or other area surrounding optical assembly  130  during collection of image data from a patient site PS). In similar flushing procedures, injectate  305  can be delivered at a rate between 3 ml/second and 9 ml/second (e.g. approximately 6 ml/sec via one or more delivery catheters  50 ), to purge non-transparent material. 
     In these flushing procedures, injectate  305  can comprise a transparent fluid selected from the group consisting of: saline; contrast; Dextran; and combinations of one or more of these. In some embodiments, the volume of injectate  305  delivered and/or the time of injectate  305  delivery during a flushing procedure is determined by a parameter selected from the group consisting of: type of procedure being performed; diameter of vessel in which optical assembly  130  is positioned; length of pullback; duration of pullback; and combinations of one or more of these. In some embodiments, injectate  305  is delivered during a flushing procedure by a delivery catheter with an ID greater than 0.027″ (e.g. a first delivery catheter  50  whose distal end  59  is more proximal than a second delivery catheter  50  inserted into the first delivery catheter  50 ). In some embodiments, injectate  305  is delivered via multiple lumens  52  in associated multiple delivery catheters  50  (e.g. in the space between two or more pairs of delivery catheters  50  arranged to slidingly receive each other in a sequential fashion). 
     In some embodiments, injectate comprises a first fluid delivered in a first portion of a flushing procedure (e.g. a fluid comprising saline and/or a fluid comprising no or minimal contrast), and a second fluid including contrast (e.g. a second fluid comprising saline and contrast), such as to limit the amount of contrast delivered to the patient during the flush procedure. In these embodiments, injector  300  can comprise two reservoirs (as described hereabove), such as a first reservoir for supplying the first fluid and a second reservoir for supplying the second fluid. When comprised of two reservoirs, injector  300  can be configured to deliver the fluids in each reservoir at different rates, such as to achieve different pressures and/or to provide flushing through different catheters with different IDs. 
     As described herein, optical assembly  130  can be rotated (e.g. via rotation of core  120 ) and retracted (e.g. via retraction of shaft  110  by retraction assembly  220 ) during collection of image data, such as a rotation combined with retraction to create a 3D image of the patient site PS. In some embodiments, optical assembly  130  is rotated at a rate between 40 rps and 1000 rps, such as a rate of approximately 250 rps. In some embodiments, optical assembly  130  is rotated at a first rate during an imaging mode, and a second rate during a preview mode (imaging mode and preview mode each described hereabove). In some embodiments, the retraction of optical assembly  130  spans of distance of between 1 cm and 15 cm, such as a retraction of approximately 4 cm. In some embodiments, optical assembly  130  is retracted at a rate of between 1 mm/sec and 60 mm/sec. In some embodiments, the retraction of optical assembly  130  comprises a retraction of approximately 7.5 cm over 4 seconds and/or a retraction rate of approximately 20 mm/sec. In some embodiments, retraction of optical assembly  130  comprises a resolution of between 5 μm and 20 μm axially and/or a resolution between 20 μm and 100 μm longitudinally. The longitudinal resolution is governed by two factors: the spot-size (light beam cross-section) at the tissue surface being imaged and the spacing between successive rotations of optical assembly  130  during retraction. For a rotation rate of 100 rps and a pullback rate of 22 mm/sec, a pitch of 200 μm between rotations results. In these configurations, a spot size between 20 μm and 40 μm would result in collecting image data which under-samples the objects being imaged. System  10  can be configured to more closely match spot size with pitch, such as by correlating spot size with rotation rate and/or pullback rate. 
     In some embodiments, imaging system  10  is constructed, arranged and used to create an image as described in applicant&#39;s co-pending U.S. Provisional Application Ser. No. 62/212,173, titled “Imaging System includes Imaging Probe and Delivery Devices”, filed Aug. 31, 2015; the content of each of which is incorporated herein by reference in its entirety for all purposes. 
     In some embodiments, system  10  is configured to assist in the selection, placement and/or use of a treatment device  91 . Treatment device  91  can comprise a stent retriever configured to remove thrombus or other occlusive matter from a patient, such as when imaging probe  100  images the anatomy and/or the treatment device  91  to produce anatomical information (e.g. used to select the size or other geometry of the stent retriever), visualize the stent retriever at the occlusive site (e.g. to position treatment device  91 ), and or visualize occlusive matter (e.g. thrombus) engaged with and/or not removed by the treatment device  91 . In some embodiments, system  10  is configured to quantify a thrombus volume, such as a thrombus to be removed by a treatment device  91 . Thrombus visualized by system  10  can comprise thrombus selected from the group consisting of: residual thrombus in acute stroke; thrombus remaining after a thrombus removal procedure; thrombus present after flow diverter implantation; and combinations thereof. 
     In some embodiments, system  10  is configured to provide anatomical information to be used to select a site of implantation and/or to select a particular implantable device to be implanted in the patient, such as implant  85  of system  10  described hereabove. System  10  can be configured to image at least one perforator artery of the patient, such as to image one, two or more perforator arteries of at least 50 μm in diameter. Implant  85  can be implanted in the patient via implant delivery device  80 , such as when implant  85  comprises a stent and/or a flow diverter. System  10  can be configured to perform a function selected from the group consisting of: detect and/or quantify implant  85  apposition (e.g. a stent or flow diverter malapposition); provide quantitative and/or qualitative information regarding the size and/or placement of an implant  85  to be implanted in a patient, such as information related to perforator location; perforator geometry, neck size and/or flow diverter mesh density; and combinations of one or more of these. System  10  can be configured to provide information related to an implant  85  parameter selected from the group consisting of: porosity; length; diameter; and combinations thereof. System  10  can be configured to provide implant  85  porosity information comprising the porosity of one or more portions of implant  85 , such as a portion to be positioned proximate a sidebranch of a vessel in which implant  85  is implanted. System  10  can be configured to provide porosity information based on a wire diameter of implant  85 . System  10  can be configured to provide information related to the implantation (e.g. implantation site or device information) of a second implant  85  to be implanted in the patient. In these embodiments in which two implanted devices  85  are used, the first and second implanted devices can comprise similar or dissimilar devices (e.g. a stent and a flow diverter, two stents or two flow diverters). System  10  can be configured to collect image data during deployment of one or more implants  85 . System  10  can be configured to collect image data used to modify an implanted device (e.g. during and/or after implantation), such as to modify the porosity of implant  85  (e.g. via a treatment device  91  comprising a balloon catheter used to adjust the porosity of a partially or fully implanted implant  85 ). 
     Imaging conventionally inaccessible areas of the body (e.g. coronary arteries, neurovascular arteries, the endocrine system, pulmonary airways, etc.) using specialized catheters has been in use for several decades. Even so, products for these applications are still being widely developed as technological advances allow higher resolution, new modalities (e.g. spatially-resolved spectroscopy), and lower cost probes to be realized. Limitations and other issues with the current catheters are described herebelow. Such imaging catheters commonly utilize high-speed rotation of distally-located optics to create a cross sectional view of a body lumen since reduced diameter imaging catheters generally precludes the use of conventional optics or so-called coherent fiber bundles. Rather than creating a multi-pixel conventional ‘snapshot’, the image with rotating optics is built up one or two pixels at a time by scanning a single imaging spot, similar to the raster scan employed by older CRT&#39;s. This rotation may be coupled with a longitudinal motion (‘pull-back’) to create a spiral scan of the artery or lumen, which can be rendered as a 3-D image. The majority of currently available imaging catheters have a distally located imaging element, connected optically or electrically to a proximal end. The imaging element is attached to a mechanical transmission that provides rotation and pullback to occur. Recently, advances in micro-motor technology can supplant the mechanical transmission with distally located actuation, but pullback is still required. However, these motors are expensive and relatively large (available designs do not allow probes below 1 mm OD to be constructed). 
     There are a number of commercially available “torque shafts” which are miniature wire-wound tubes intended to transmit torque over a long and flexible shaft. Such devices are now commonly used in intravascular ultrasound (IVUS) procedures as well as OCT procedures. Imaging probes combined with torque shafts perform rotational scanning in coronary arteries for example. Generally however, these devices are approximately 0.8 to 1.3 mm in OD, (2.4 Fr to 4 Fr) and are thus 2 to 4 times larger than the devices required by neurological applications. Presently, such torque wires are not scalable to the sizes required to permit the construction of scanning imaging catheters less than 0.7 mm in OD. 
     Since optical imaging in arteries necessitates the clearing of obfuscating blood, usually with a flush solution, the imaging catheter diameter becomes critically important in smaller or obstructed vessels (e.g. due to use of smaller guides). Since it is often diseased or obstructed vessels that require imaging for diagnosis and treatment, imaging probe  100  can be designed for a small diameter (e.g. an OD less than or equal to 0.025″, 0.016″ or 0.014″). 
     As has been previously disclosed (Petersen, et al U.S. Pat. No. 6,891,984 [the &#39;984 patent]; Crowley U.S. Pat. No. 6,165,127 [the &#39;127 patent], the content of each of which is incorporated herein by reference in its entirety for all purposes), using a viscous fluid located at the distal region of the imaging catheter is provided to prevent twisting. 
     Achieving uniform rotational scanning at the distal tip of a single fiber imaging catheter, while maintaining an overall device size less than 500 μm in OD is a significant challenge. Because it is currently impractical to add a motor to the distal tip that is sized less than 1 mm in OD (see Tsung-Han Tsai, Benjamin Potsaid, Yuankai K. Tao, Vijaysekhar Jayaraman, James Jiang, Peter J. S. Heim, Martin F. Kraus, Chao Zhou, Joachim Hornegger, Hiroshi Mashimo, Alex E. Cable, and James G. Fujimoto; “Ultrahigh speed endoscopic optical coherence tomography using micro-motor imaging catheter and VCSEL technology”, Biomed Opt Express. 2013 Jul. 1; 4(7): 1119-1132), with the attendant wires and size issues, a way must be found to apply torque to the proximal end and transmit the torque to the distal tip (which may be as much as three meters away in some clinical applications) while maintaining uniform rotational speed. Uniform speed is paramount to image fidelity as non-uniform rotation can lead to image smearing and severe distortions (See  FIG. 3 ). If the extremely low inherent rotational stiffness of a glass fiber is considered, the issues of uniformly spinning the distal tip by driving the proximal end can be appreciated. Uniform rotation is critically important in endoscopic techniques in order to obtain accurate circumferential images. The term ‘NURD’ (non-uniform rotational distortion) has been coined in the industry to describe these deleterious effects. 
     An example of distortion caused by non-uniform rotational distortion (NURD) is shown in  FIG. 3 . The solid curve is a simulated perfectly round artery, 4 mm in diameter. The curve with square data points is the image of the same arterial wall with NURD. In this case, the catheter rotation is slowed by 50% over a small portion of the cycle, and sped up by 50% in another portion, such that the average distal rotational speed matches the proximal rotational speed (as it must, otherwise rapidly accumulating twist would cause the core  120  to break). It can be seen that this NURD can lead to significant measurement errors. The imaging probe  100  and other components of system  10  are configured to reduce these types of distortions. 
     The &#39;127 patent discloses the use of a viscous fluid located inside the bore of an ultrasound catheter. The purpose of the fluid is to provide loading of a torque wire such that the wire enters the regime of high torsional stiffness at moderate spin rates. As described in the &#39;127 patent, this fluid is housed within a separate bore formed inside the main catheter, increasing the overall size of the device. The fluid does not contact the imaging tip, nor does the ultrasound energy propagate through this fluid. This approach also requires the use of a torque wire, limiting the achievable reduction in size needed. In the imaging probe of the present inventive concepts, one or more viscous fluids (e.g. one or more fluids  190 ) can be provided to deliberately cause twisting (i.e. winding) of core  120 . The twisting can comprise dynamic twisting that changes with total (i.e. end-to-end) frictional load (torque) of probe  100 , to result in a relatively constant rotational rate. Probe  100  can be configured such that the amount of twisting changes during a pullback of one or more portions of probe  100  (e.g. a pullback of core  120  and/or a pullback of core  120  and shaft  110 ). 
     The &#39;984 patent utilizes a viscous fluid with a high index of refraction to simultaneously reduce refractive effects at the curved sheath boundary as well as provide viscous loading to allow an optical fiber to be the torque transmitter. This configuration allows a certain reduction in size. However, the &#39;984 patent fails to describe or disclose a mechanism for confining the fluid at the distal tip within the geometry constraints; unavoidable migration of this fluid during transport and storage will cause unavoidable loss of performance. Similarly, the &#39;984 patent fails to address issues that could arise during pullback of the internal fiber which will cause voids to form in the viscous fluid, these voids causing relatively large optical effects (so-called ‘bubble-artifacts’, see, for example, “Expert review document on methodology, terminology, and clinical applications of optical coherence tomography: physical principles, methodology of image acquisition, and clinical application for assessment of coronary arteries and atherosclerosis”, Francisco Prati, et al, European heart Journal, Nov. 4, 2009). In some embodiments, probe  100  is configured to rotate core  120  in a single direction (i.e. unidirectional) during use. In some embodiments, probe  100  comprises a torque shaft within shaft  110  and frictionally engaged with core  120 , such as torque shaft  110   b  described herebelow. Torque shaft  110   b  can extend from the proximal end of probe  100  to a location proximal to optical assembly  130 , such as a torque shaft with a distal end that is located at least 5 cm from optical assembly  130 , or a distal end that is located proximal to the most proximal location of shaft  110  that is positioned within the patient. 
     A liquid, gel or other fluid-filled (e.g. and sealed) imaging probe  100  has the advantage that it does not require purging (e.g. to remove air bubbles). The fluid  190   a  or  190   b  can be configured as a lubricant, reducing friction between core  120  and shaft  110 . In embodiments in which core  120  is pulled back relative to shaft  110  to obtain an image, a void is created at the end of core  120  that can be filled with liquid, gel or other fluid (e.g. fluid  190 ). 
     It is difficult for fluid to “fill in” this region as it must be provided from the proximal end of shaft  110  and travel the length of the core  120 . Bubbles are likely to form here as a low pressure can be generated. In embodiments of the present inventive concepts, rather than retracting the core  120  within shaft  110 , the entire imaging probe  100  is pulled back during image data collection (i.e. core  120  and shaft  110  are retracted in unison without relative axial motion between the two). Since the shaft  110  moves along with the core  120 , the presence of a low-pressure region at the end of the imaging core is eliminated or at least mitigated. 
     As shown in  FIG. 4 , such “mutual” motion of shaft  110  and core  120  allows shaft  110  to have a larger diameter around optical assembly  130 , as relative motion between optical assembly  130  and shaft  110  is avoided. A larger diameter optical assembly  130  (e.g. a larger diameter lens of optical assembly  130 ) provides collection of more light, which can correlate to a brighter image. This configuration can also provide a lens of optical assembly  130  that has a focal length that is positioned farther away from the OD (i.e. outer surface) of shaft  110  surrounding optical assembly  130 , improving distal image quality. Alternatively or additionally, and also as shown in  FIG. 4 , optical assembly  130  can comprise an OD that is larger than an ID of at least a portion of shaft  110  proximal to optical assembly  130 . In these embodiments, optical assembly  130  and shaft  110  can be retracted simultaneously during collection of image data from a target area. 
     In some embodiments, the shaft  110  wall is relatively thicker over a majority of its length as compared to a thinner wall of shaft  110  at a distal portion of shaft  110  (e.g. thinner at a shaft  110  portion proximate optical assembly  130 ). Such a configuration allows for improved longitudinal and torsional control for positioning of imaging probe  100 . In some embodiments, shaft  110  can comprise a stiffened portion positioned about optical assembly  130 , such as a stiffened segment of shaft  110  comprising: a different (stiffer) wall material; a braided shaft portion; and or a stiffening element (e.g. a wire embedded in the wall of shaft  110 ). The stiffened distal portion of shaft  110  can correlate to a thinner wall, which in turn correlates to optical assembly  130  comprising larger optical components (e.g. one or more larger diameter lenses), for example without having to increase the OD of shaft  110  surrounding optical assembly  130 . In some embodiments, shaft  110  has varying mechanical properties along its length (e.g. a stiffened proximal segment for “push-ability”), and a gradually decreasing stiffness distally (e.g. to improve deliverability and safety as advanced into tortuous anatomy). 
     Also as shown in  FIG. 4 , optical assembly  130  can comprise a lens  131  and a reflecting element  132  (e.g. to “turn” the light). Reflecting element  132  is configured such that optical assembly  130  is asymmetrical. When optical assembly  130  is spun at high speed, the presence of viscous liquids or other viscous fluids in the optical path surrounding optical assembly  130  could, in some cases, cause cavitation in the region behind reflector  132 . As shown in  FIG. 5 , in some embodiments, probe  100  includes a first fluid, fluid  190   a  that surrounds core  120 , and a second, different fluid, fluid  190   b , that surround optical assembly  130 , such that fluid  190   a  can be configured to provide a first function (e.g. prevent or at least reduce undesired rotational variances of core  120 ), while fluid  190   b  provides a second function (e.g. prevent or at least reduce cavitation about optical assembly  130 ). In some embodiments, the viscosity of fluid  190   b  can be selected to be relatively low viscosity, such as to minimize cavitation, while the viscosity of fluid  190   a  can be selected to be relatively high (e.g. at least more viscous than fluid  190   b ) to optimize uniformity in the rotational speed. 
     In neurological placement, imaging probe  100  is usually placed into a femoral vessel of the patient. There is significant tortuosity in the vasculature proximal to a neurological imaging area, starting with the carotid artery take off from the aorta. In some embodiments, the use of a high viscosity fluid  190   a  in the mid and/or proximal section of imaging probe  100  allows the fluid  190   a  to provide the additional function of lubricating the spinning core  120  in the shaft  110  (e.g. lubrication of benefit due to the high tortuosity in which imaging probe  100  is placed). The reduced friction that results reduces the stress on the core  120 , and allows smoother motions over any discontinuities in shaft  110  or core  120 . Fluid  190  can be configured to provide sufficient lubrication or other advantageous parameter to eliminate or at least reduce (“reduce” herein) adverse effects that would otherwise occur as probe  100  is positioned in tortuous anatomy (e.g. when distal portion  119   a  is positioned proximate and distal to the carotid artery). In these embodiments, fluid  190  can comprise a high viscosity fluid. 
     Additionally, the presence of a high viscosity fluid  190   a  helps maintain the lower viscosity fluid  190   b  in the distal end of shaft  110  prior to use, as the higher viscosity fluid  190   a  in shaft  110  operates as a barrier, and reduces the likelihood of fluid  190   b  migration from the imaging region about optical assembly  130  prior to use (e.g. during sterilization and shipping of imaging probe  100 ). In some embodiments, a sealing element, such as sealing element  116 , is positioned between two or more different fluids  190 . Alternatively, no separating element may be present, such as when one or more of the fluids  190  comprise a gel configured not to mix with a neighboring fluid  190 . 
     In some embodiments, imaging probe  100  includes an inertial assembly comprising an impeller, propeller or other inertia-based element configured to reduce undesired variances in rotational speed of optical assembly  130 , such as is shown in  FIG. 6 . Imaging probe  100  comprises impeller  182  that is attached to the core  120 . Drag on impeller  182  “winds up” core  120  and decreases unintended or otherwise undesired variances in rotational velocity of the fiber. Impeller  182  operates to spin the fluid  190  between shaft  110  and optical assembly  130 . The impeller  182  blades form drag, which due to its symmetry around its rotational axis, remains uniform through the rotation. In some embodiments, the radial extending ends of impeller  182  intentionally contact an inner wall of shaft  110 , to alternatively or increasingly provide drag. Impeller  182  can comprise one or more projections from core  120 , such as projections that frictionally engage shaft  110  and/or otherwise cause shear force that applies a load to core  120  during rotation. Impeller  182  can comprise one or more projections from shaft  110 , such as projections that frictionally engage core  120  and/or otherwise cause shear force that applies a load to core  120  during rotation. 
     Impeller  182  can be configured to cause wind-up loading of core  120 . Impeller  182  can be configured to frictionally engage fluid  190  and/or shaft  110  during rotation of core  120 . Impeller  182  can comprise a component selected from the group consisting of: turbine; vane-type micro-structure; flywheel; and combinations of one or more of these. 
     Liquid, gel or other fluid positioned inside shaft  110  can have a tendency to form bubbles. If these bubbles are in the optical path they will reduce the light transmission. In some embodiments, fluid  190   a  and/or fluid  190   b  (singly or collectively fluid  190 ) can be pressurized (e.g. to a pressure of 100 psi or above) to prevent or at least reduce the size of any bubbles in shaft  110 , such as is described herein in reference to  FIG. 7 . 
     Small tire inflators are commonly used for filling bicycle tires. They are available in sizes smaller than 1 inch, which is suitable for this application. These and similarly configured inflators can provide pressures up to and beyond 100 psi, which when applied to fluid  190  can significantly reduce the bubble size. Assuming a bubble size at atmospheric pressure is to be 0.1 microliters, the bubble size at 100 psi can be calculated as: 
     
       
      
       V 
       p 
       =V 
       a 
       P 
       a 
       /P 
       p  
      
     
     where: 
     V p =Bubble volume under pressure 
     V a =Bubble volume at atmospheric pressure (e.g. 0.1 μL) 
     P a =Atmospheric pressure (14.7 PSI) 
     P p =Pressurizing device pressure (e.g. 100 psi) 
     Under pressurization, the bubble volume decreases from 0.1 μL to 0.0147 μL. The corresponding bubble diameter is reduced from 0.022″ to 0.011″, which will mitigate or eliminate deleterious effects on the optical beam. 
       FIG. 7  is a sectional view of an imaging probe including a pressurization system, consistent with the present inventive concepts. Imaging probe  100  comprises shaft  110  with proximal end  111 , lumen  112 , core  120  and optical connector  102 , each of which can be of similar construction and arrangement as those described hereabove in reference to  FIG. 1 . Imaging probe  100  can include pressurization assembly  183  (e.g. a pressurized gas canister) which can be fluidly connected to lumen  112  via valve  184  (e.g. a one way check valve). In some embodiments, each imaging probe  100  is provided with a pressurization assembly  183 . Alternatively, a single pressurization assembly  183  can be reused (e.g. used on multiple imaging probes  100  in multiple clinical procedures). In some embodiments, pressurization assembly  183  can be pre-attached to shaft  110 , or separated and attachable. In some embodiments, pressurization assembly  183  can be operably attached and/or activated just prior to the time of clinical use of imaging probe  100 , such as to pressurize fluid within lumen  112  or other imaging probe  100  internal location, such as to reduce the size of one or more gas bubbles in a fluid, such as fluid  190  described herein. 
     In some embodiments, at a location near to proximal end  111  of shaft  110 , sealing element  151  (e.g. a compressible O-ring) is positioned between core  120  and shaft  110 . Shaft  110  and sealing element  151  can be constructed and arranged to maintain a relative seal as lumen  112  is pressurized (e.g. as described above), while allowing core  120  to rotate within shaft  110  and sealing element  151 . Sealing element  151  can provide a seal during rotation of core  120  within shaft  110 . Retraction of shaft  110  and core  120  simultaneously during imaging, as described herein, simplifies the design of sealing element  151 . In some alternative embodiments, core  120  is retracted within shaft  110 , and sealing element  151  is configured to maintain a seal during that retraction. 
     In some embodiments, at least a portion of shaft  110  is configured to radially expand as fluid  190  is pressurized, such as is shown in  FIGS. 15A-C . Pressurization assembly  183  is attached to connector  102  such that fluid  190  can be introduced and/or pressurized into and/or within shaft  110 . In  FIG. 15A , proximal portion  111   a  of shaft  110  is expanded (e.g. lumen  112  is expanded in the region of proximal portion  111   a ). In  FIG. 15B , proximal portion  111   a  and mid portion  115  of shaft  110  are expanded. In  FIG. 15C , proximal portion  111   a , mid portion  115  and distal portion  119   a  are expanded. In these embodiments, system  10  can be configured to rotate core  120  after shaft  110  has been fully expanded as shown in  FIG. 15C . Expansion of shaft  110  can create and/or increase space between core  120  and the inner wall of shaft  110 . In some embodiments, shaft  110  remains at least partially expanded (e.g. shaft  110  has been plastically deformed) when the pressure of fluid  190  is decreased (e.g. to atmospheric pressure). Shaft  110  can be configured to expand to a first diameter (ID and/or OD) when fluid  190  is pressurized to a first pressure, and to expand to a second, larger diameter, when fluid  190  is pressurized to a second, higher pressure. In some embodiments, shaft  110  is configured to become more rigid as the pressure of fluid  190  increases. 
     There can be two attachments from probe  100  (e.g. a disposable catheter) to the non-disposable components of system  10 . One is attached to shaft  110  (a non-rotating shaft) and the other to core  120 . Attachment of imaging probe  100  to console  200  can comprise two functional attachments. One attachment comprises attachment of shaft  110  to a retraction assembly, such as retraction assembly  220  described herein, such that shaft  110  (and optic assembly  130 ) can be retracted during collection of image data. Another attachment comprises attaching core  120  to a rotational assembly, such as rotation assembly  210 , such that core  120  can be rotated during collection of image data. Both attachments can be retracted together during collection of image data. The attachment of core  120  makes the optical connection between core  120  and an imaging assembly (e.g. imaging assembly  230  described herein) and can provide the motive power to rotate core  120  (e.g. an attachment to rotation assembly  210 ). 
     The imaging system and associated imaging probes of the present inventive concepts provide enhanced compatibility with traditional therapeutic catheters, such as those used in neurological procedures as described herein. 
     Stent retrieval devices (also referred to as “stent retrievers”) are used for endovascular recanalization. While the rate of successful revascularization is high, multiple passes of the stent retrieval device are often required to fully remove the clot, adding to procedure times and increasing likelihood of complications. The addition of imaging to a stent retrieval procedure has the potential to reduce both procedure time and complications. In  FIGS. 8-11 , system  10  comprises imaging probe  100  and a therapeutic device, treatment device  91 . While treatment device  91  is shown as a stent retriever, other therapeutic devices would be applicable, such as a treatment device  91  selected from the group consisting of: stent retriever; embolization coil; embolization coil delivery catheter; stent; covered stent; stent delivery device; aneurysm treatment implant; aneurysm treatment implant delivery device; flow diverter; balloon catheter; and combinations thereof. Imaging probe  100  and treatment device  91  have been placed into a vessel, such as a blood vessel of the neck or head. Imaging probe  100  and treatment device  91  can be insertable into a single catheter, such as delivery catheter  50   d  shown. 
     Positioning of optical assembly  130  and resulting images produced assure correct placement of the treatment device  91  (e.g. positioning of the stent retriever distal to the thrombus) and also assures that therapy is completed successfully (e.g. sufficient thrombus has been removed), which can both reduce procedure times and improve clinical results. 
     In some embodiments, system  10  comprises delivery catheter  50   a  (not shown, but such as a 6-8 Fr guide catheter) that can be placed into a target vessel (e.g. artery), such as by using transfemoral access. In some embodiments, delivery catheter  50   a  comprises a standard balloon guide catheter, such as to prevent distal thrombus migration and to enhance aspiration during thrombectomy. System  10  can further comprise delivery catheter  50   b  (not shown but such as a flexible 5-6 Fr catheter) that is used as an intermediate catheter, advanced through delivery catheter  50   a  to gain distal access close to the occluded segment of the vessel. System  10  can comprise a third delivery catheter  50   c , shown, such as a 0.021″ to 0.027″ microcatheter used to cross the thrombus or otherwise provide access to a target site to be treated and/or imaged. Angiographic runs can be performed through the delivery catheter  50   c  to angiographically assess the proper position of the delivery catheter  50   c  tip (e.g. position of tip distal to the thrombus and to estimate the length of the clot). The treatment device  91  (e.g. the stent retriever shown) is subsequently released by pulling back delivery catheter  50   c  while holding the treatment device  91  in place. In some embodiments, the treatment device  91  should cover the entire length of an occlusion in order to achieve flow restoration (e.g. when the stent portion opens). 
     In  FIG. 8 , a distal portion of delivery catheter  50   c  has been positioned in a blood vessel (e.g. within a vessel location including thrombus). A stent portion of treatment device  91  remains undeployed, captured within the distal portion of delivery catheter  50   c . In  FIG. 9 , delivery catheter  50   c  is retracted, such that the stent portion of treatment device  91  deploys (e.g. to engage thrombus, thrombus not shown). In  FIG. 10 , imaging probe  100  is advanced through the deployed stent portion of treatment device  91 . Image data can be collected during the advancement. In  FIG. 11 , imaging probe  100  is being retracted (optical assembly  130  passes through the stent portion of treatment device  91 ) as image data is collected, such as to perform a procedural assessment as described herein. 
     In some embodiments, system  10  is constructed and arranged such that proximally applied torque (e.g. to core  120 ) and distally applied rotational speed control (e.g. to core  120  and/or optical assembly  130 ) is provided. This configuration has several benefits, including but not limited to: small size; low-cost; and an independence from the tortuous path proximal to the distal tip of imaging probe  100 . 
     In some embodiments, system  10  is configured to provide precise rotational control (e.g. avoid undesired rotational speed variances of core  120  and/or optical assembly  130 ) via inertial damping, such as inertial damping which increases with rotational speed. This control can be accomplished with: a viscous fluid in contact with core  120  and/or optical assembly  130  (e.g. fluid  190   a  and/or  190   b  described herein); a fluid in contact with a mechanical load such a vane-type micro-structure; a mechanical load acting as a flywheel; and combinations thereof. 
     In some embodiments, imaging probe  100  comprises a guidewire independent design, comprising a shaft  110  with an OD of 0.016″ or less (e.g. approximately 0.014″), and configured such that its shaft  110 , core  120  and optical assembly  130  are retracted in unison using external pullback (e.g. retraction assembly  220  described herein). 
     In some embodiments, imaging probe  100  is configured to be advanced through vessels to a target site with or without the use of a microcatheter. 
     In some embodiments, imaging probe  100  is configured such that core  120  and optical assembly  130  are configured to be retracted within shaft  110  during image data collection, such as an internal pullback using purge media (e.g. fluid  190  or other purge media introduced between the core  120  and the shaft  110 ). In some embodiments, the introduced material is configured to provide a function selected from the group consisting of: index matching; lubrication; purging of bubbles; and combinations thereof. 
     In some embodiments, imaging probe  100  comprises an Rx tip. In these embodiments, imaging probe  100  can be configured such that core  120  and optical assembly  130  are configured to be retracted within shaft  110  during image data collection. 
     In some embodiments, imaging probe  100  comprises a highly deliverable, very small cross-section probe. In some embodiments, shaft  110  comprises one or more optically transparent materials providing an optically transparent window, viewing portion  117 , positioned within distal portion  119   a  of shaft  110 . Viewing portion  117  can comprise a length between 1 mm and 100 mm, such as a length of approximately 3 mm. In some embodiments, viewing portion  117  can comprise a length less than 50 mm, such as less than 20 mm or less than 15 mm (e.g. a relatively short window in embodiments in which both shaft  110  and optical assembly  130  are retracted simultaneously during the collection of image data). Viewing portion  117  can comprise a material selected from the group consisting of: nylon; nylon 12; nylon 66; and combinations of one or more of these. In some embodiments, at least a portion of shaft  110  comprises a reinforced portion, such as a reinforced portion comprising a stiffening element (e.g. stiffening element  118  shown in  FIG. 1 ). In some embodiments, stiffening element  118  terminates proximal to optical assembly  130  (e.g. proximal to viewing portion  117  of shaft  110 ). Alternatively, stiffening element  118  can extend beyond optical assembly  130 , such as is shown in  FIG. 2 , and the pullback geometry can be coordinated such that the light path to and from optical assembly  130  avoids the stiffening element  118 . Stiffening element  118  can be included to resist twisting of distal portion  119   a , such as during rotation of the core  120 . For example, stiffening element  118  can comprise an element selected from the group consisting of: a coil; a metal coil; a metal coil wound over a plastic such as PTFE; a tube; a metal tube; a metal and/or plastic braid positioned within the wall of shaft  110 ; and combinations thereof. In some embodiments, shaft  110  comprises a stiffening element  118  comprising a coil wound in a direction such that rotation of the core  120  tends to cause the coil to tighten (e.g. to further resist twisting of shaft  110 ). In some embodiments, one or more portions of stiffening element  118  come into contact with a fluid maintained within shaft  110  (e.g. fluid  190  described herein), such that twisting of shaft  110  is reduced by torque forces applied by the fluid to stiffening element  118 . 
     In some embodiments, system  10  includes integration of imaging probe  100  with one or more therapeutic devices (e.g. one or more treatment devices  91 ). For example, a treatment device  91  can comprise a stent retriever, and system  10  can provide real time simultaneous visualization of one or more of: the patient&#39;s anatomy (e.g. blood vessel wall and other tissue of the patient); the treatment device  91  (e.g. one or more struts of treatment device  91 ); and/or thrombus or other occlusive matter. The simultaneous visualization can be correlated to reduced procedure time and improved efficacy. 
     In some embodiments, system  10  is configured to apply proximal pressure to imaging probe  100 , such as to keep the distal portion bubble-free or at least to mitigate bubble generation within one or more fluids  190  of imaging probe  100 . 
     As described herein, imaging probe  100  can comprise a core  120  including a thin fiber that can be optically coupled on its distal end to optical assembly  130  comprising a lens assembly. In some embodiments, a fluid interacting element (e.g. a coil or length of wound wire, though not necessarily a torque wire), can be positioned just proximal to optical assembly  130  (e.g. embedded in the wall of or within shaft  110 ). In some embodiments, the shaft  110  can be filled with a low viscosity fluid  190 , such as to interact with the fluid interacting element and create drag. The coil or other fluid interacting element, in contrast to a conventional torque wire, is not wound to create a high-fidelity transmission of torque but to increase viscous drag. The fluid  190  can be low viscosity (e.g. with a viscosity at or below 1000 Cp) to allow for easier filling and will reduce bubble artifacts created in high viscosity solutions. The fluid interacting element can comprise an impeller, such as impeller  182  described herein. The fluid interacting element comprises a non-circular cross section portion of a portion of shaft  110 , such as a cross section with a geometry selected from the group consisting of: polygon shaped cross section of a lumen of shaft  110 ; projections into a lumen of shaft  110 ; recesses in inner diameter (i.e. the inner wall) of shaft  110 ; and combinations of one or more of these. 
     In some embodiments, imaging probe  100  comprises a formed element to create viscous drag, such as impeller  182  described herein. This element can have a variety of shapes designed to maximize the interaction with an internal fluid  190 . 
     In some embodiments, imaging probe  100  is constructed and arranged such that viscous drag is created by mechanical friction between a part rigidly coupled to core  120  and in close contact with the wall of shaft  110 . The friction may be created by the shear force of a narrow annulus between the mechanical element and the shaft  110  wall, such as when the shaft  110  is filled with fluid  190 . 
     In some embodiments, imaging probe  100  comprises at least one fluid  190  that is contained by at least one sealing element (e.g. sealing element  116  and/or sealing element  151  described herein). Sealing element  116  and/or  151  can be constructed and arranged to allow core  120  to rotate in the sealed region while preventing the (viscous) fluid  190  to penetrate through the seal. In some embodiments, two sealing elements  116   a  and  116   b  are included, such as one positioned just proximal to the optical assembly  130  and one positioned further distal, such as is shown in  FIG. 17 . In these embodiments, the separation distance between the two sealing elements  116  and/or the viscosity of the captured fluid  190  can be chosen to create sufficient torsional loading as core  120  is rotated. In some embodiments, the two sealing elements  116   a  and  116   b  are positioned apart at a distance between 1 mm and 20 mm. In some embodiments, the fluid  190  comprises a viscosity between 10 Cp and 100 Cp. 
     In some embodiments, system  10  comprises an imaging probe  100  and a console  200 . Imaging probe  100  comprises: a proximal end  111  and a distal end  119 , and at least one lumen  112  extending between the proximal end  111  and the distal end  119 . Core  120  is positioned within lumen  112 , the proximal end of core  120  in optical and mechanical communication with console  200 , and the distal end of core  120  in optical communication with an optical assembly configured to collect image data within a body lumen. 
     In some embodiments, imaging probe  100  comprises optical assembly  130  located at the distal end of core  120 , optical assembly  130  in mechanical and optical communication with core  120 , the optical assembly  130  directing light to the target (e.g. thrombus, vessel wall, tissue and/or implant) being imaged and collecting return light from the imaged target. Imaging probe  100  can further comprise an inertial system (e.g. impeller  182 ) located proximate the distal end of the core  120 , wherein the inertial system reduces undesired rotational speed variances that occur during a rotation of the core  120 . The inertial system can comprise a (predetermined) length of wound hollow core cable, the distal end of the cable being affixed to core  120  just proximal to optical assembly  130 , the proximal end unattached (e.g. not attached to core  120 ). The inertial system can comprise a mechanical resistance element located in the distal region of core  120 , and can be in contact with a fluid  190  confined within a lumen  112  of shaft  110 , the mechanical resistance arising during rotation within the fluid  190 . 
     In some embodiments, imaging probe  100  comprises a sealing element, such as sealing element  151  described herein, located within lumen  112  of shaft  110 . Sealing element  151  can be configured to allow rotation of core  120  while forming substantially liquid-tight seals around core  120  and the inner wall of shaft  110 . In some embodiments, sealing element  151  is further configured as a mechanical resistance element. In some embodiments, sealing element  151  is formed from a hydrogel. In some embodiments, the sealing element  151  is formed by an adhesive (e.g. a UV-cured adhesive), bonding to the inner wall of shaft  110 , but not the surface of core  120 . In some embodiments, the surface of core  120  is configured to avoid bonding to an adhesive (e.g. a UV adhesive). In some embodiments, the sealing element  151  is formed from a compliant material such as a silicone rubber. 
     In some embodiments, an imaging system comprises an imaging probe  100  and an imaging console, console  200 . The imaging probe  100  comprises: a proximal end  111 , a distal end  119 , and at least one lumen  112  extending between the proximal end  111  and distal end  119 . The imaging probe further comprises: a core  120  contained within a lumen  112  of the shaft  110 , the proximal end of core  120  in optical and mechanical communication with console  200 , the distal end optically connected to an optical assembly  130  configured to collect image data within a body lumen. Optical assembly  130  is positioned at the distal end of the core  120 , and is configured to direct light to the target (e.g. thrombus, vessel well, tissue and/or implant) being imaged and collecting return light from the imaged target. 
     In some embodiments, imaging probe  100  comprises a core  120  and one, two or more inertial elements, such as impeller  182  described herein, attached to optical assembly  130  and/or core  120  (e.g. attached to a distal portion of core  120 ). Impeller  182  can be configured such that when the core  120  is retracted (e.g. in the presence of liquid, gel or gaseous medium, such as fluid  190 ), the impeller  182  imparts a rotational force to core  120 , such as to reduce undesired rotational speed variances. Impeller  182  can comprise a turbine-like construction. 
     In some embodiments, system  10  comprises an imaging probe  100  and an imaging console, console  200 . Imaging probe  100  comprises a proximal end  111 , a distal end  119 , and at least one lumen  112  extending between proximal end  111  and distal end  119 . Imaging probe  100  can further comprise a rotatable optical core, core  120  contained within a lumen  112  of shaft  110 , the proximal end of core  120  in optical and mechanical communication with console  200 , and the distal end configured to collect image data from a body lumen. 
     As described herein, imaging probe  100  comprises optical assembly  130  which is positioned at the distal end of core  120 . Optical assembly  130  is in mechanical and optical communication with core  120 , and is configured to direct light to tissue target being imaged and collect return light from the imaged target. Imaging probe  100  can further comprise a reinforcing or other stiffening element (e.g. stiffening element  118  described herein) embedded into shaft  110  that creates an improved stiffness but effectively optically transparent window for rotational and pullback scanning. Stiffening element  118  can comprise an embedded wire and/or a stiffening member (e.g. a plastic stiffening member) in shaft  110 . Stiffening element  118  can comprise a spiral geometry. As described hereabove, the spiral geometry of stiffening element  118  and a pullback spiral rotational pattern of optical assembly  130  can be matched but offset by approximately one-half of the spiral of stiffening element  118 , such that an imaging beam of optical assembly  130  passes between the stiffening  118  spirals during pullback of optical assembly  130 . 
     Referring now to  FIG. 12 , a side sectional view of the distal portion of probe  100  is illustrated, having been inserted into a vessel, such that optical assembly  130  is positioned within treatment device  91  (e.g. a stent deployment device, stent retriever or other treatment device), consistent with the present inventive concepts. Probe  100  comprises shaft  110 , core  120 , optical assembly  130 , lens  131  and reflector  132 , and those and other components of probe  100  can be of similar construction and arrangement to those described hereabove. In some embodiments, distal end  119  comprises a geometry and/or a stiffness to enhance advancement of distal end  119  through blood vessels and/or one or more devices positioned within a blood vessel. For example, distal end  119  can comprise the bullet-shaped profile shown in  FIG. 12 . Alternatively or additionally, treatment device  91  can comprise a proximal portion (e.g. proximal end  91   a  shown), which can be configured to enhance delivery of distal end  119  through proximal end  91   a . In some embodiments, probe  100  comprises a spring tip, such as spring tip  104  described hereabove. 
     Probe  100  and other components of system  10  can be configured to allow a clinician or other operator to “view” (e.g. in real time) the collection of thrombus or other occlusive matter into treatment device  91 , such as to determine when to remove treatment device  91  and/or how to manipulate treatment device  91  (e.g. a manipulation to remove treatment device  91  and/or reposition treatment device  91  to enhance the treatment). The ability to view the treatment can avoid unnecessary wait time and other delays, as well as improve efficacy of the procedure (e.g. enhance removal of thrombus). 
     Referring now to  FIG. 13 , a side sectional view of the distal portion of probe  100  is illustrated, consistent with the present inventive concepts. Probe  100  comprises shaft  110 , lumen  112 , core  120 , optical assembly  130 , lens  131  and reflector  132 , and those and other components of probe  100  can be of similar construction and arrangement to those described hereabove. In some embodiments, distal portion  119   a  of shaft  110  comprises a reinforcing element, stiffening element  118   a  as shown in  FIG. 13 . Inclusion of stiffening element  118   a  can allow the wall of shaft  110  surrounding optical assembly  130  to be thin (e.g. thinner than the wall in a more proximal portion of shaft  110 ). Stiffening element  118   a  can comprise an optically transparent material as described herein. Stiffening element  118   a  can be configured to provide column and/or torsional strength to shaft  110 . In some embodiments, probe  100  comprises a lumen narrowing structure, such as tube  114  shown positioned within lumen  112  of shaft  110 . Tube  114  can be adhesively or at least frictionally engaged with the inner wall of shaft  110  or the outer surface of core  120 . In some embodiments, tube  114  is simply a projection from the inner wall of shaft  110  (e.g. part of shaft  110 ). Tube  114  can be configured to provide a function selected from the group consisting of: increase torsional strength of shaft  110 ; increase column strength of shaft  110 ; provide a capillary action between fluid surrounding core  120  and/or optical assembly  130 ; and combinations thereof. In some embodiments, probe  100  comprises fluid  190   a  and/or fluid  190   b  shown, such as is described hereabove. Fluid  190   a  and fluid  190   b  can comprise similar or dissimilar fluids. In some embodiments, fluid  190   a  and/or fluid  190   b  comprise a low viscosity fluid as described hereabove. In some embodiments, fluid  190   a  and/or fluid  190   b  comprise a shear-thinning fluid as described hereabove. 
     Referring now to  FIG. 14 , a schematic of an imaging probe is illustrated, shown in a partially assembled state and consistent with the present inventive concepts. Probe  100  can comprise a first portion, comprising a connector  102   a , outer shaft  110   a  and spring tip  104 , constructed and arranged as shown in  FIG. 14 . Probe  100  can further comprise a second portion, connector  102   b , torque shaft  110   b , core  120  and optical assembly  130 . Outer shaft  110   a , spring tip  104 , core  120  and optical assembly  130  and other components of probe  100  can be of similar construction and arrangement to those described hereabove. Connector  102   b  can be of similar construction and arrangement to connector  102  described hereabove, such as to optically connect probe  100  to console  200 . Connector  102   a  can be configured to surround and mechanically engage connector  102   b , such that connectors  102   a  and/or  102   b  mechanically connect to console  200 . 
     Torque shaft  110   b  frictionally engages core  120  (e.g. via an adhesive), at least at a distal portion of torque shaft  110   b . Torque shaft  110   b  can be attached to connector  102   b  via an adhesive or other mechanical engagement (e.g. via a metal tube, not shown, but such as a tube that is pressed into connector  102   b ). In some embodiments, a strain relief is provided at the end of torque shaft  110   b , tube  121  shown. Tube  121  can be configured to reduce kinking and/or to increase the fixation between torque shaft  110   b  and core  120 . Tube  121  and torque shaft  110   b  can have similar IDs and/or ODs. 
     During assembly, torque shaft  110   b , optical assembly  130  and core  120  are positioned within shaft  110   a . Connector  102   a  can be engaged with connector  102   b  to maintain relative positions of the two components. 
     Torque shaft  110   b  can comprise one or more plastic or metal materials, such as when torque shaft  110   b  comprises a braided torque shaft (e.g. a braid comprising at least stainless steel). Torque shaft  110   b  can comprise a length such that the distal end of torque shaft  110   b  terminates a minimum distance away from optical assembly  130 , such as a length of approximately 49 cm. In some embodiments, torque shaft  110   b  comprises a length such that none or a small portion of torque shaft  110   b  enters the patient. In these embodiments, retraction assembly  220  can be positioned and engage shaft  110  at a location distal to the distal end of retraction assembly  220 . 
     Referring now to  FIGS. 15A-C , a series of side sectional views of an imaging probe in a series of expansion steps of its shaft via an internal fluid, consistent with the present inventive concepts. Probe  100  comprises connector  102 , shaft  110 , core  120  and optical assembly  130 , and those and other components of probe  100  can be of similar construction and arrangement to those described hereabove. Shaft  110  comprises proximal portion  111   a , mid portion  115  and distal portion  119   a . Probe  100  further comprises pressurization assembly  183 , which may include valve  184 , each of which can be of similar construction and arrangement to the similar components described hereabove in reference to  FIG. 7 . Probe  100  can be configured such that as fluid is introduced into lumen  112 , and/or the pressure of fluid within lumen  112  is increased, shaft  110  expands. For example, a first introduction of fluid  190  into lumen  112  and/or a first increase of pressure of fluid  190  in lumen  112  (e.g. via pressurization assembly  183 ) can be performed such that the proximal portion  111   a  of shaft  110  expands as shown in  FIG. 15A . Subsequently, a second introduction of fluid  190  into lumen  112  and/or a second increase of pressure of fluid  190  in lumen  112  can be performed such that the mid portion  115  of shaft  110  expands as shown in  FIG. 15B . Subsequently, a third introduction of fluid  190  into lumen  112  and/or a third increase of pressure of fluid  190  in lumen  112  can be performed such that the distal portion  119   a  of shaft  110  expands as shown in  FIG. 15C . In some embodiments, shaft  110  is expanded to create a space between the inner wall of shaft  110  and core  120  and/or to create a space between the inner wall of shaft  110  and optical assembly  130 . 
     Referring now to  FIG. 16 , a side sectional view of the distal portion of an imaging probe comprising a distal marker positioned in reference to an optical assembly is illustrated, consistent with the present inventive concepts. Probe  100  comprises shaft  110 , core  120 , optical assembly  130 , lens  131  and reflector  132 , and those and other components of probe  100  can be of similar construction and arrangement to those described hereabove. Shaft  110  comprises proximal portion  111   a  (not shown), distal portion  119   a  and distal end  119 . Probe  100  can comprise a functional element  133   a , which can be positioned on or relative to optical assembly  130  (e.g. positioned on or at a desired and/or known distance from optical assembly  130 ). Functional element  133   a  is shown positioned distal to optical assembly  130 , and at a fixed distance as determined by a connecting element, tube  134  (e.g. heat shrink tubing or other plastic tube). In some embodiments, functional element  133   a  comprises a sensor, transducer or other functional element as described herein. In some embodiments, functional element  133   a  comprises a visualizable element, such as a radiopaque element, ultrasonically visible element and/or magnetically visible element. In some embodiments, functional element  133   a  comprises a visualizable element used to identify the location of optical assembly  130  on an image produced by an imaging device (e.g. a fluoroscope, ultrasonic imager or MRI) and the fixed location of functional element  133   a  relative to optical assembly  130  avoids registration issues, such as would be encountered if functional element  133   a  was positioned on shaft  110  or other component of probe  100  whose dimensions or other relative position to optical assembly  130  may change over time (e.g. due to expansion or contraction due to temperature shifts). In some embodiments, functional element  133   a  is attached to optical assembly  130  via a connecting element, such as tube  134  described hereabove, and tube  134  or other connecting element (e.g. connecting element  137  described herein) is configured to avoid dimensional changes (e.g. is minimally affected by changes in temperature). In some embodiments, probe  100  comprises fixation element  136  (e.g. an adhesive such as a UV cured adhesive) positioned just distal to functional element  133   a  as shown in  FIG. 16 , and configured to maintain the position of functional element  133   a.    
     Probe  100  can comprise one or more elements that cause frictional engagement between shaft  110  and core  120  and/or simply reduce the space between shaft  110  and core  120 , such as one or more of elements  122   a ,  122   b  and  122   c  shown in  FIG. 16 , such as to reduce undesired variations in rotational rate as described herein. In some embodiments, probe  100  comprises a compression element, band  122   a , positioned about and/or within shaft  110  and causing a portion of the inner wall of shaft  110  to frictionally engage core  120 . Alternatively or additionally, shaft  110  can comprise one or more projections  122   b  (e.g. annular projections) that extend to frictionally engage core  120 . Alternatively or additionally, core  120  can comprise one or more projections  122   c , each extending to frictionally engage shaft  110 . One or more of each of elements  122   a ,  122   b  and/or  122   c  can be included, and each can be configured to create a shear force that applies a load to core  120  during rotation of core  120 . In some embodiments, a fluid  190  is positioned between shaft  110  and core  120 , such as a shear-thinning fluid as described herein. In these embodiments, one or more of elements  122   a ,  122   b  and/or  122   c  can comprise a space reducing element configured to increase the shear-thinning of the fluid  190  as core  120  is rotated (i.e. by interacting with the fluid  190  to increase the amount of thinning than that which would have occurred without the presence of the one or more space reducing elements  122 ). 
     Referring now to  FIG. 17 , a side sectional view of the distal portion of an imaging probe comprising two sealing elements is illustrated, consistent with the present inventive concepts. Probe  100  comprises shaft  110 , core  120 , optical assembly  130 , lens  131 , reflector  132  and viewing portion  117 , and those and other components of probe  100  can be of similar construction and arrangement to those described hereabove. Shaft  110  comprises lumen  112 , proximal portion  111   a  (not shown), distal portion  119   a  and distal end  119 . Probe  100  can further comprise spring tip  104 . Probe  100  can comprise functional element  113 , as shown, or other functional elements as described herein. Probe  100  of  FIG. 17  comprises two sealing elements, sealing element  116   a  (e.g. an O-ring surrounding core  120 ) and sealing element  116   b  (e.g. an elastomeric disk). In some embodiments, a fluid  190   b  is positioned within shaft  110  between sealing elements  116   a  and  116   b , such as is described hereabove. Alternatively or additionally, a second fluid  190   a  is positioned within shaft  110  proximal to sealing element  116   a . In some embodiment, a third fluid  190   c  (not shown), is positioned within shaft  110  distal to sealing element  116   b . Fluids  190   a - c  can comprise similar or dissimilar fluids, also as described hereabove. 
     Referring now to  FIG. 18 , a side sectional view of the distal portion of an imaging probe comprising a reflecting element offset from a lens and multiple visualizable markers is illustrated, consistent with the present inventive concepts. Probe  100  comprises shaft  110 , core  120 , optical assembly  130 , lens  131  and reflector  132 , and those and other components of probe  100  can be of similar construction and arrangement to those described hereabove. Shaft  110  comprises lumen  112 , proximal portion  111   a  (not shown), distal portion  119   a  and distal end  119 . 
     In some embodiments, reflector  132  can be positioned distal to lens  131 , and connected via connecting element  137 , as shown in  FIG. 18  and described hereabove. 
     In some embodiments, probe  100  comprises multiple visualizable markers, such as the four functional elements  123   a  shown in  FIG. 18 , which can be configured to provide a “ruler function” when visualized by a separate imaging device such as a fluoroscope, ultrasonic imager or MRI (e.g. when functional elements  123   a  comprise a radiopaque marker; an ultrasonically reflective marker or a magnetic marker, respectively). Functional elements  123   a  can comprise one or more visualizable bands (e.g. one or more compressible bands and/or wire coils) frictionally engaged with core  120 . Alternatively or additionally, one or more functional elements  123   a  can be positioned on, within the wall of and/or on the inner surface of shaft  110 . Functional elements  123   a  can be positioned equidistantly apart and/or at a known separation distance. In some embodiments, one or more functional elements  123   a  can be further configured as a sealing element (e.g. to provide a seal to a contained fluid such as one or more fluids  190  described herein) and/or as a rotational dampener configured to reduce undesired rotational velocity changes of core  120  and/or optical assembly  130 . 
     While the preferred embodiments of the devices and methods have been described in reference to the environment in which they were developed, they are merely illustrative of the principles of the present inventive concepts. Modification or combinations of the above-described assemblies, other embodiments, configurations, and methods for carrying out the inventive concepts, and variations of aspects of the inventive concepts that are obvious to those of skill in the art are intended to be within the scope of the claims. In addition, where this application has listed the steps of a method or procedure in a specific order, it may be possible, or even expedient in certain circumstances, to change the order in which some steps are performed, and it is intended that the particular steps of the method or procedure claim set forth herebelow not be construed as being order-specific unless such order specificity is expressly stated in the claim.