Patent Publication Number: US-2022225884-A1

Title: Devices, systems, and methods for assessment of vessels

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of U.S. patent application Ser. No. 16/286,331, filed Feb. 26, 2019, now U.S. Pat. No. 11,298,030, which is a continuation of U.S. patent application Ser. No. 14/335,603, filed Jul. 18, 2014, now U.S. Pat. No. 10,226,189, which claims the benefit of the filing date of provisional U.S. Patent Application No. 61/856,509, filed Jul. 19, 2013, each of which is herein incorporated by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to the assessment of vessels and, in particular, the assessment of the severity of a blockage or other restriction to the flow of fluid through a vessel. Aspects of the present disclosure are particularly suited for evaluation of biological vessels in some instances. For example, some particular embodiments of the present disclosure are specifically configured for the evaluation of a stenosis of a human blood vessel. 
     BACKGROUND 
     A currently accepted technique for assessing the severity of a stenosis in a blood vessel, including ischemia causing lesions, is fractional flow reserve (FFR). FFR is a calculation of the ratio of a distal pressure measurement (taken on the distal side of the stenosis) relative to a proximal pressure measurement (taken on the proximal side of the stenosis). FFR provides an index of stenosis severity that allows determination as to whether the blockage limits blood flow within the vessel to an extent that treatment is required. The normal value of FFR in a healthy vessel is 1.00, while values less than about 0.80 are generally deemed significant and require treatment. Common treatment options include angioplasty and stenting. 
     Coronary blood flow is unique in that it is affected not only by fluctuations in the pressure arising proximally (as in the aorta) but is also simultaneously affected by fluctuations arising distally in the microcirculation. Accordingly, it is not possible to accurately assess the severity of a coronary stenosis by simply measuring the fall in mean or peak pressure across the stenosis because the distal coronary pressure is not purely a residual of the pressure transmitted from the aortic end of the vessel. As a result, for an effective calculation of FFR within the coronary arteries, it is necessary to reduce the vascular resistance within the vessel. Currently, pharmacological hyperemic agents, such as adenosine, are administered to reduce and stabilize the resistance within the coronary arteries. These potent vasodilator agents reduce the dramatic fluctuation in resistance predominantly by reducing the microcirculation resistance associated with the systolic portion of the heart cycle to obtain a relatively stable and minimal resistance value. 
     However, the administration of hyperemic agents is not always possible or advisable. First, the clinical effort of administering hyperemic agents can be significant. In some countries (particularly the United States), hyperemic agents such as adenosine are expensive, and time consuming to obtain when delivered intravenously (IV). In that regard, IV-delivered adenosine is generally mixed on a case-by-case basis in the hospital pharmacy. It can take a significant amount of time and effort to get the adenosine prepared and delivered to the operating area. These logistic hurdles can impact a physician&#39;s decision to use FFR. Second, some patients have contraindications to the use of hyperemic agents such as asthma, severe COPD, hypotension, bradycardia, low cardiac ejection fraction, recent myocardial infarction, and/or other factors that prevent the administration of hyperemic agents. Third, many patients find the administration of hyperemic agents to be uncomfortable, which is only compounded by the fact that the hyperemic agent may need to be applied multiple times during the course of a procedure to obtain FFR measurements. Fourth, the administration of a hyperemic agent may also require central venous access (e.g., a central venous sheath) that might otherwise be avoided. Finally, not all patients respond as expected to hyperemic agents and, in some instances, it is difficult to identify these patients before administration of the hyperemic agent. 
     Accordingly, there remains a need for improved devices, systems, and methods for assessing the severity of a blockage in a vessel and, in particular, a stenosis in a blood vessel. In that regard, there remains a need for improved devices, systems, and methods for assessing the severity of a stenosis in the coronary arteries that do not require the administration of hyperemic agents. Further, there remains a need for improved devices, systems, and methods for providing visual depictions of vessel that allow assessment of the vessel and, in particular, any stenosis or lesion of the vessel. Further still, there remains a need for improved devices, systems, and methods that simulate one or more available treatment options for the vessel. 
     SUMMARY 
     Embodiments of the present disclosure are configured to assess the severity of a blockage in a vessel and, in particular, a stenosis in a blood vessel. In some particular embodiments, the devices, systems, and methods of the present disclosure are configured to provide visual depictions of vessel that allow assessment of the vessel and, in particular, any stenosis or lesion of the vessel. Further, in some embodiments the devices, systems, and methods of the present disclosure are configured to simulate one or more treatment options for the vessel. The simulation of the treatment option(s) can be utilized to identify the most viable treatment option for a particular vessel. 
     In some embodiments, methods of evaluating a vessel of a patient are provided. The method includes obtaining pressure measurements from first and second instruments positioned within a vessel of a patient while the second instrument is moved longitudinally through the vessel from a first position to a second position and the first instrument remains stationary within the vessel; and outputting an image of the vessel on a display, the output image including visualizations based on the obtained pressure measurements. In some implementations, the first position is distal of at least one stenosis of the vessel and the second position is proximal of the at least one stenosis of the vessel such that moving the second instrument longitudinally through the vessel comprises a pullback. In some instances, the image is an intravascular image, such as an intravascular ultrasound (IVUS) image or an optical coherence tomography (OCT) image. In some instances, the image is an extravascular image, such as a two dimensional angiographic image, a three dimensional angiographic image, or a computed tomography angiographic (CTA) image. 
     In some implementations, the visualizations include an intensity map based on changes in a pressure ratio of the obtained pressure measurements from the first and second instruments. For example, a first visual characteristic of the intensity map is associated with pressure ratios above a threshold value and a second visual characteristic of the intensity map is associated with pressure ratios below the threshold value. In some embodiments, the visualizations include a graph of a pressure ratio of the obtained pressure measurements from the first and second instruments. The graph is scaled, rotated, and mirror imaged, as necessary, to align the proximal and distal portions of the graph with the corresponding proximal and distal portions of the vessel as depicted in the image in some instances. In some embodiments, the visualizations include numerical values of a pressure ratio of the obtained pressure measurements from the first and second instruments. In some implementations, the visualizations include markings representative of a pressure ratio of the obtained pressure measurements from the first and second instruments. In that regard, the number of markings is representative of a relative change in the pressure ratio in some instances. Systems for performing such methods are also provided. 
     Additional aspects, features, and advantages of the present disclosure will become apparent from the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Illustrative embodiments of the present disclosure will be described with reference to the accompanying drawings, of which: 
         FIG. 1  is a diagrammatic perspective view of a vessel having a stenosis according to an embodiment of the present disclosure. 
         FIG. 2  is a diagrammatic, partial cross-sectional perspective view of a portion of the vessel of  FIG. 1  taken along section line  2 - 2  of  FIG. 1 . 
         FIG. 3  is a diagrammatic, partial cross-sectional perspective view of the vessel of  FIGS. 1 and 2  with instruments positioned therein according to an embodiment of the present disclosure. 
         FIG. 4  is a diagrammatic, schematic view of a system according to an embodiment of the present disclosure. 
         FIG. 5  is a visual depiction of a vessel profile based on pressure measurements according to an embodiment of the present disclosure. 
         FIG. 6  is a visual depiction of a vessel profile based on pressure measurements similar to that of  FIG. 5 , but illustrating an alternative embodiment of the present disclosure. 
         FIG. 7  is a visual depiction of a vessel profile based on pressure measurements according to another embodiment of the present disclosure. 
         FIG. 8  is a visual depiction of a vessel profile based on pressure measurements according to another embodiment of the present disclosure. 
         FIG. 9  is an angiographic image of a vessel according to an embodiment of the present disclosure. 
         FIG. 10  provides visual depictions of a profile of the vessel of  FIG. 9  based on pressure measurements according to an embodiment of the present disclosure. 
         FIG. 11  is an annotated version of the angiographic image of  FIG. 9  based on the profile information of  FIG. 10  according to an embodiment of the present disclosure. 
         FIG. 12  is an annotated version of the angiographic image of  FIG. 9  based on the profile information of  FIG. 10  according to another embodiment of the present disclosure. 
         FIG. 13  provides visual depictions of a profile of the vessel of  FIG. 9  similar those of  FIG. 10 , but simulating a treatment option according to an embodiment of the present disclosure. 
         FIG. 14  is an annotated version of the angiographic image of  FIG. 9  based on the treatment option of  FIG. 13  according to an embodiment of the present disclosure. 
         FIG. 15  is an angiographic image of a vessel according to another embodiment of the present disclosure. 
         FIG. 16  provides visual depictions of a profile of the vessel of  FIG. 15  based on pressure measurements according to an embodiment of the present disclosure. 
         FIG. 17  is a three dimensional model of the vessel of  FIG. 15  based on the profile information of  FIG. 16  according to an embodiment of the present disclosure. 
         FIG. 18  is a three dimensional model of the vessel of  FIG. 15  based on the profile information of  FIG. 16  according to another embodiment of the present disclosure. 
         FIG. 19  provides visual depictions of a profile of the vessel of  FIG. 15  similar those of  FIG. 16 , but simulating a treatment option according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the present disclosure, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It is nevertheless understood that no limitation to the scope of the disclosure is intended. Any alterations and further modifications to the described devices, systems, and methods, and any further application of the principles of the present disclosure are fully contemplated and included within the present disclosure as would normally occur to one skilled in the art to which the disclosure relates. In particular, it is fully contemplated that the features, components, and/or steps described with respect to one embodiment may be combined with the features, components, and/or steps described with respect to other embodiments of the present disclosure. For the sake of brevity, however, the numerous iterations of these combinations will not be described separately. 
     Referring to  FIGS. 1 and 2 , shown therein is a vessel  100  having a stenosis according to an embodiment of the present disclosure. In that regard,  FIG. 1  is a diagrammatic perspective view of the vessel  100 , while  FIG. 2  is a partial cross-sectional perspective view of a portion of the vessel  100  taken along section line  2 - 2  of  FIG. 1 . Referring more specifically to  FIG. 1 , the vessel  100  includes a proximal portion  102  and a distal portion  104 . A lumen  106  extends along the length of the vessel  100  between the proximal portion  102  and the distal portion  104 . In that regard, the lumen  106  is configured to allow the flow of fluid through the vessel. In some instances, the vessel  100  is a blood vessel. In some particular instances, the vessel  100  is a coronary artery. In such instances, the lumen  106  is configured to facilitate the flow of blood through the vessel  100 . 
     As shown, the vessel  100  includes a stenosis  108  between the proximal portion  102  and the distal portion  104 . Stenosis  108  is generally representative of any blockage or other structural arrangement that results in a restriction to the flow of fluid through the lumen  106  of the vessel  100 . Embodiments of the present disclosure are suitable for use in a wide variety of vascular applications, including without limitation coronary, peripheral (including but not limited to lower limb, carotid, and neurovascular), renal, and/or venous. Where the vessel  100  is a blood vessel, the stenosis  108  may be a result of plaque buildup, including without limitation plaque components such as fibrous, fibro-lipidic (fibro fatty), necrotic core, calcified (dense calcium), blood, fresh thrombus, and mature thrombus. Generally, the composition of the stenosis will depend on the type of vessel being evaluated. In that regard, it is understood that the concepts of the present disclosure are applicable to virtually any type of blockage or other narrowing of a vessel that results in decreased fluid flow. 
     Referring more particularly to  FIG. 2 , the lumen  106  of the vessel  100  has a diameter  110  proximal of the stenosis  108  and a diameter  112  distal of the stenosis. In some instances, the diameters  110  and  112  are substantially equal to one another. In that regard, the diameters  110  and  112  are intended to represent healthy portions, or at least healthier portions, of the lumen  106  in comparison to stenosis  108 . Accordingly, these healthier portions of the lumen  106  are illustrated as having a substantially constant cylindrical profile and, as a result, the height or width of the lumen has been referred to as a diameter. However, it is understood that in many instances these portions of the lumen  106  will also have plaque buildup, a non-symmetric profile, and/or other irregularities, but to a lesser extent than stenosis  108  and, therefore, will not have a cylindrical profile. In such instances, the diameters  110  and  112  are understood to be representative of a relative size or cross-sectional area of the lumen and do not imply a circular cross-sectional profile. 
     As shown in  FIG. 2 , stenosis  108  includes plaque buildup  114  that narrows the lumen  106  of the vessel  100 . In some instances, the plaque buildup  114  does not have a uniform or symmetrical profile, making angiographic evaluation of such a stenosis unreliable. In the illustrated embodiment, the plaque buildup  114  includes an upper portion  116  and an opposing lower portion  118 . In that regard, the lower portion  118  has an increased thickness relative to the upper portion  116  that results in a non-symmetrical and non-uniform profile relative to the portions of the lumen proximal and distal of the stenosis  108 . As shown, the plaque buildup  114  decreases the available space for fluid to flow through the lumen  106 . In particular, the cross-sectional area of the lumen  106  is decreased by the plaque buildup  114 . At the narrowest point between the upper and lower portions  116 ,  118  the lumen  106  has a height  120 , which is representative of a reduced size or cross-sectional area relative to the diameters  110  and  112  proximal and distal of the stenosis  108 . Note that the stenosis  108 , including plaque buildup  114  is exemplary in nature and should be considered limiting in any way. In that regard, it is understood that the stenosis  108  has other shapes and/or compositions that limit the flow of fluid through the lumen  106  in other instances. While the vessel  100  is illustrated in  FIGS. 1 and 2  as having a single stenosis  108  and the description of the embodiments below is primarily made in the context of a single stenosis, it is nevertheless understood that the devices, systems, and methods described herein have similar application for a vessel having multiple stenosis regions. 
     Referring now to  FIG. 3 , the vessel  100  is shown with instruments  130  and  132  positioned therein according to an embodiment of the present disclosure. In general, instruments  130  and  132  may be any form of device, instrument, or probe sized and shaped to be positioned within a vessel. In the illustrated embodiment, instrument  130  is generally representative of a guide wire, while instrument  132  is generally representative of a catheter. In that regard, instrument  130  extends through a central lumen of instrument  132 . However, in other embodiments, the instruments  130  and  132  take other forms. In that regard, the instruments  130  and  132  are of similar form in some embodiments. For example, in some instances, both instruments  130  and  132  are guide wires. In other instances, both instruments  130  and  132  are catheters. On the other hand, the instruments  130  and  132  are of different form in some embodiments, such as the illustrated embodiment, where one of the instruments is a catheter and the other is a guide wire. Further, in some instances, the instruments  130  and  132  are disposed coaxial with one another, as shown in the illustrated embodiment of  FIG. 3 . In other instances, one of the instruments extends through an off-center lumen of the other instrument. In yet other instances, the instruments  130  and  132  extend side-by-side. In some particular embodiments, at least one of the instruments is as a rapid-exchange device, such as a rapid-exchange catheter. In such embodiments, the other instrument is a buddy wire or other device configured to facilitate the introduction and removal of the rapid-exchange device. Further still, in other instances, instead of two separate instruments  130  and  132  a single instrument is utilized. In some embodiments, the single instrument incorporates aspects of the functionalities (e.g., data acquisition) of both instruments  130  and  132 . 
     Instrument  130  is configured to obtain diagnostic information about the vessel  100 . In that regard, the instrument  130  includes one or more sensors, transducers, and/or other monitoring elements configured to obtain the diagnostic information about the vessel. The diagnostic information includes one or more of pressure, flow (velocity), images (including images obtained using ultrasound (e.g., IVUS), OCT, thermal, and/or other imaging techniques), temperature, and/or combinations thereof. The one or more sensors, transducers, and/or other monitoring elements are positioned adjacent a distal portion of the instrument  130  in some instances. In that regard, the one or more sensors, transducers, and/or other monitoring elements are positioned less than 30 cm, less than 10 cm, less than 5 cm, less than 3 cm, less than 2 cm, and/or less than 1 cm from a distal tip  134  of the instrument  130  in some instances. In some instances, at least one of the one or more sensors, transducers, and/or other monitoring elements is positioned at the distal tip of the instrument  130 . 
     The instrument  130  includes at least one element configured to monitor pressure within the vessel  100 . The pressure monitoring element can take the form a piezo-resistive pressure sensor, a piezo-electric pressure sensor, a capacitive pressure sensor, an electromagnetic pressure sensor, a fluid column (the fluid column being in communication with a fluid column sensor that is separate from the instrument and/or positioned at a portion of the instrument proximal of the fluid column), an optical pressure sensor, and/or combinations thereof. In some instances, one or more features of the pressure monitoring element are implemented as a solid-state component manufactured using semiconductor and/or other suitable manufacturing techniques. Examples of commercially available guide wire products that include suitable pressure monitoring elements include, without limitation, the PrimeWire PRESTIGE® pressure guide wire, the PrimeWire® pressure guide wire, and the ComboWire® XT pressure and flow guide wire, each available from Volcano Corporation, as well as the PressureWire™ Certus guide wire and the PressureWire™ Aeris guide wire, each available from St. Jude Medical, Inc. Generally, the instrument  130  is sized such that it can be positioned through the stenosis  108  without significantly impacting fluid flow across the stenosis, which would impact the distal pressure reading. Accordingly, in some instances the instrument  130  has an outer diameter of 0.018″ or less. In some embodiments, the instrument  130  has an outer diameter of 0.014″ or less. 
     Instrument  132  is also configured to obtain diagnostic information about the vessel  100 . In some instances, instrument  132  is configured to obtain the same diagnostic information as instrument  130 . In other instances, instrument  132  is configured to obtain different diagnostic information than instrument  130 , which may include additional diagnostic information, less diagnostic information, and/or alternative diagnostic information. The diagnostic information obtained by instrument  132  includes one or more of pressure, flow (velocity), images (including images obtained using ultrasound (e.g., IVUS), OCT, thermal, and/or other imaging techniques), temperature, and/or combinations thereof. Instrument  132  includes one or more sensors, transducers, and/or other monitoring elements configured to obtain this diagnostic information. In that regard, the one or more sensors, transducers, and/or other monitoring elements are positioned adjacent a distal portion of the instrument  132  in some instances. In that regard, the one or more sensors, transducers, and/or other monitoring elements are positioned less than 30 cm, less than 10 cm, less than 5 cm, less than 3 cm, less than 2 cm, and/or less than 1 cm from a distal tip  136  of the instrument  132  in some instances. In some instances, at least one of the one or more sensors, transducers, and/or other monitoring elements is positioned at the distal tip of the instrument  132 . 
     Similar to instrument  130 , instrument  132  also includes at least one element configured to monitor pressure within the vessel  100 . The pressure monitoring element can take the form a piezo-resistive pressure sensor, a piezo-electric pressure sensor, a capacitive pressure sensor, an electromagnetic pressure sensor, a fluid column (the fluid column being in communication with a fluid column sensor that is separate from the instrument and/or positioned at a portion of the instrument proximal of the fluid column), an optical pressure sensor, and/or combinations thereof. In some instances, one or more features of the pressure monitoring element are implemented as a solid-state component manufactured using semiconductor and/or other suitable manufacturing techniques. Currently available catheter products suitable for use with one or more of Siemens AXIOM Sensis, Mennen Horizon XVu, and Philips Xper IM Physiomonitoring 5 and include pressure monitoring elements can be utilized for instrument  132  in some instances. 
     In accordance with aspects of the present disclosure, at least one of the instruments  130  and  132  is configured to monitor a pressure within the vessel  100  distal of the stenosis  108  and at least one of the instruments  130  and  132  is configured to monitor a pressure within the vessel proximal of the stenosis. In that regard, the instruments  130 ,  132  are sized and shaped to allow positioning of the at least one element configured to monitor pressure within the vessel  100  to be positioned proximal and/or distal of the stenosis  108  as necessary based on the configuration of the devices. In that regard,  FIG. 3  illustrates a position  138  suitable for measuring pressure distal of the stenosis  108 . In that regard, the position  138  is less than 5 cm, less than 3 cm, less than 2 cm, less than 1 cm, less than 5 mm, and/or less than 2.5 mm from the distal end of the stenosis  108  (as shown in  FIG. 2 ) in some instances.  FIG. 3  also illustrates a plurality of suitable positions for measuring pressure proximal of the stenosis  108 . In that regard, positions  140 ,  142 ,  144 ,  146 , and  148  each represent a position that is suitable for monitoring the pressure proximal of the stenosis in some instances. In that regard, the positions  140 ,  142 ,  144 ,  146 , and  148  are positioned at varying distances from the proximal end of the stenosis  108  ranging from more than 20 cm down to about 5 mm or less. Generally, the proximal pressure measurement will be spaced from the proximal end of the stenosis. Accordingly, in some instances, the proximal pressure measurement is taken at a distance equal to or greater than an inner diameter of the lumen of the vessel from the proximal end of the stenosis. In the context of coronary artery pressure measurements, the proximal pressure measurement is generally taken at a position proximal of the stenosis and distal of the aorta, within a proximal portion of the vessel. However, in some particular instances of coronary artery pressure measurements, the proximal pressure measurement is taken from a location inside the aorta. In other instances, the proximal pressure measurement is taken at the root or ostium of the coronary artery. 
     In some embodiments, at least one of the instruments  130  and  132  is configured to monitor pressure within the vessel  100  while being moved through the lumen  106 . In some instances, instrument  130  is configured to be moved through the lumen  106  and across the stenosis  108 . In that regard, the instrument  130  is positioned distal of the stenosis  108  and moved proximally (i.e., pulled back) across the stenosis to a position proximal of the stenosis in some instances. In other instances, the instrument  130  is positioned proximal of the stenosis  108  and moved distally across the stenosis to a position distal of the stenosis. Movement of the instrument  130 , either proximally or distally, is controlled manually by medical personnel (e.g., hand of a surgeon) in some embodiments. In other embodiments, movement of the instrument  130 , either proximally or distally, is controlled automatically by a movement control device (e.g., a pullback device, such as the Trak Back® II Device available from Volcano Corporation). In that regard, the movement control device controls the movement of the instrument  130  at a selectable and known speed (e.g., 2.0 mm/s, 1.0 mm/s, 0.5 mm/s, 0.2 mm/s, etc.) in some instances. Movement of the instrument  130  through the vessel is continuous for each pullback or push through, in some instances. In other instances, the instrument  130  is moved step-wise through the vessel (i.e., repeatedly moved a fixed amount of distance and/or a fixed amount of time). Some aspects of the visual depictions discussed below are particularly suited for embodiments where at least one of the instruments  130  and  132  is moved through the lumen  106 . Further, in some particular instances, aspects of the visual depictions discussed below are particularly suited for embodiments where a single instrument is moved through the lumen  106 , with or without the presence of a second instrument. 
     In some instances, use of a single instrument has a benefit in that it avoids issues associated with variations in pressure measurements of one instrument relative to another over time, which is commonly referred to as drift. In that regard, a major source of drift in traditional Fractional Flow Reserve (FFR) measurements is divergence in the pressure reading of a guidewire relative to the pressure reading of a guide catheter. In that regard, because FFR is calculated as the ratio of the pressure measurement obtained by the guidewire to the pressure measurement obtained by the catheter, this divergence has an impact on the resulting FFR value. In contrast, where a single instrument is utilized to obtain pressure measurements as it is moved through the vessel, drift is negligible or non-existent. For example, in some instances, the single instrument is utilized to obtain relative changes in pressures as it is moved through the vessel such that the time period between pressure measurements is short enough to prevent any impact from any changes in pressure sensitivity of the instrument (e.g., less than 500 ms, less than 100 ms, less than 50 ms, less than 10 ms, less than 5 ms, less than 1 ms, or otherwise). 
     Referring now to  FIG. 4 , shown therein is a system  150  according to an embodiment of the present disclosure. In that regard,  FIG. 4  is a diagrammatic, schematic view of the system  150 . As shown, the system  150  includes an instrument  152 . In that regard, in some instances instrument  152  is suitable for use as at least one of instruments  130  and  132  discussed above. Accordingly, in some instances the instrument  152  includes features similar to those discussed above with respect to instruments  130  and  132  in some instances. In the illustrated embodiment, the instrument  152  is a guide wire having a distal portion  154  and a housing  156  positioned adjacent the distal portion. In that regard, the housing  156  is spaced approximately 3 cm from a distal tip of the instrument  152 . The housing  156  is configured to house one or more sensors, transducers, and/or other monitoring elements configured to obtain the diagnostic information about the vessel. In the illustrated embodiment, the housing  156  contains at least a pressure sensor configured to monitor a pressure within a lumen in which the instrument  152  is positioned. A shaft  158  extends proximally from the housing  156 . A torque device  160  is positioned over and coupled to a proximal portion of the shaft  158 . A proximal end portion  162  of the instrument  152  is coupled to a connector  164 . A cable  166  extends from connector  164  to a connector  168 . In some instances, connector  168  is configured to be plugged into an interface  170 . In that regard, interface  170  is a patient interface module (PIM) in some instances. In some instances, the cable  166  is replaced with a wireless connection. In that regard, it is understood that various communication pathways between the instrument  152  and the interface  170  may be utilized, including physical connections (including electrical, optical, and/or fluid connections), wireless connections, and/or combinations thereof. 
     The interface  170  is communicatively coupled to a computing device  172  via a connection  174 . Computing device  172  is generally representative of any device suitable for performing the processing and analysis techniques discussed within the present disclosure. In some embodiments, the computing device  172  includes a processor, random access memory, and a storage medium. In that regard, in some particular instances the computing device  172  is programmed to execute steps associated with the data acquisition and analysis described herein. Accordingly, it is understood that any steps related to data acquisition, data processing, instrument control, and/or other processing or control aspects of the present disclosure may be implemented by the computing device using corresponding instructions stored on or in a non-transitory computer readable medium accessible by the computing device. In some instances, the computing device  172  is a console device. In some particular instances, the computing device  172  is similar to the s5™ Imaging System or the s5i™ Imaging System, each available from Volcano Corporation. In some instances, the computing device  172  is portable (e.g., handheld, on a rolling cart, etc.). Further, it is understood that in some instances the computing device  172  comprises a plurality of computing devices. In that regard, it is particularly understood that the different processing and/or control aspects of the present disclosure may be implemented separately or within predefined groupings using a plurality of computing devices. Any divisions and/or combinations of the processing and/or control aspects described below across multiple computing devices are within the scope of the present disclosure. 
     Together, connector  164 , cable  166 , connector  168 , interface  170 , and connection  174  facilitate communication between the one or more sensors, transducers, and/or other monitoring elements of the instrument  152  and the computing device  172 . However, this communication pathway is exemplary in nature and should not be considered limiting in any way. In that regard, it is understood that any communication pathway between the instrument  152  and the computing device  172  may be utilized, including physical connections (including electrical, optical, and/or fluid connections), wireless connections, and/or combinations thereof. In that regard, it is understood that the connection  174  is wireless in some instances. In some instances, the connection  174  includes a communication link over a network (e.g., intranet, internet, telecommunications network, and/or other network). In that regard, it is understood that the computing device  172  is positioned remote from an operating area where the instrument  152  is being used in some instances. Having the connection  174  include a connection over a network can facilitate communication between the instrument  152  and the remote computing device  172  regardless of whether the computing device is in an adjacent room, an adjacent building, or in a different state/country. Further, it is understood that the communication pathway between the instrument  152  and the computing device  172  is a secure connection in some instances. Further still, it is understood that, in some instances, the data communicated over one or more portions of the communication pathway between the instrument  152  and the computing device  172  is encrypted. 
     The system  150  also includes an instrument  175 . In that regard, in some instances instrument  175  is suitable for use as at least one of instruments  130  and  132  discussed above. Accordingly, in some instances the instrument  175  includes features similar to those discussed above with respect to instruments  130  and  132  in some instances. In the illustrated embodiment, the instrument  175  is a catheter-type device. In that regard, the instrument  175  includes one or more sensors, transducers, and/or other monitoring elements adjacent a distal portion of the instrument configured to obtain the diagnostic information about the vessel. In the illustrated embodiment, the instrument  175  includes a pressure sensor configured to monitor a pressure within a lumen in which the instrument  175  is positioned. The instrument  175  is in communication with an interface  176  via connection  177 . In some instances, interface  176  is a hemodynamic monitoring system or other control device, such as Siemens AXIOM Sensis, Mennen Horizon XVu, and Philips Xper IM Physiomonitoring 5. In one particular embodiment, instrument  175  is a pressure-sensing catheter that includes fluid column extending along its length. In such an embodiment, interface  176  includes a hemostasis valve fluidly coupled to the fluid column of the catheter, a manifold fluidly coupled to the hemostasis valve, and tubing extending between the components as necessary to fluidly couple the components. In that regard, the fluid column of the catheter is in fluid communication with a pressure sensor via the valve, manifold, and tubing. In some instances, the pressure sensor is part of interface  176 . In other instances, the pressure sensor is a separate component positioned between the instrument  175  and the interface  176 . The interface  176  is communicatively coupled to the computing device  172  via a connection  178 . 
     Similar to the connections between instrument  152  and the computing device  172 , interface  176  and connections  177  and  178  facilitate communication between the one or more sensors, transducers, and/or other monitoring elements of the instrument  175  and the computing device  172 . However, this communication pathway is exemplary in nature and should not be considered limiting in any way. In that regard, it is understood that any communication pathway between the instrument  175  and the computing device  172  may be utilized, including physical connections (including electrical, optical, and/or fluid connections), wireless connections, and/or combinations thereof. In that regard, it is understood that the connection  178  is wireless in some instances. In some instances, the connection  178  includes a communication link over a network (e.g., intranet, internet, telecommunications network, and/or other network). In that regard, it is understood that the computing device  172  is positioned remote from an operating area where the instrument  175  is being used in some instances. Having the connection  178  include a connection over a network can facilitate communication between the instrument  175  and the remote computing device  172  regardless of whether the computing device is in an adjacent room, an adjacent building, or in a different state/country. Further, it is understood that the communication pathway between the instrument  175  and the computing device  172  is a secure connection in some instances. Further still, it is understood that, in some instances, the data communicated over one or more portions of the communication pathway between the instrument  175  and the computing device  172  is encrypted. 
     It is understood that one or more components of the system  150  are not included, are implemented in a different arrangement/order, and/or are replaced with an alternative device/mechanism in other embodiments of the present disclosure. For example, in some instances, the system  150  does not include interface  170  and/or interface  176 . In such instances, the connector  168  (or other similar connector in communication with instrument  152  or instrument  175 ) may plug into a port associated with computing device  172 . Alternatively, the instruments  152 ,  175  may communicate wirelessly with the computing device  172 . Generally speaking, the communication pathway between either or both of the instruments  152 ,  175  and the computing device  172  may have no intermediate nodes (i.e., a direct connection), one intermediate node between the instrument and the computing device, or a plurality of intermediate nodes between the instrument and the computing device. 
     Referring now to  FIGS. 5-8 , shown therein are various visual depictions of a vessel profile based on pressure measurements according to embodiments of the present disclosure. Referring more specifically to  FIG. 5 , shown therein is a visual representation  180  of a vessel. In that regard, visual representation  180  illustrates approximately a 112 mm segment of the vessel between points  182  and  184 . In that regard, point  182  is representative of a starting position of an instrument within the vessel while point  184  is representative of an ending position of the instrument within the vessel after movement of the instrument longitudinally along the lumen of the vessel. Accordingly, in the instance of a pullback of the instrument, point  182  is distal of point  184  within the vessel. On the other hand, in the instance where the instrument pushed through the vessel, point  182  is proximal of the point  184 . Regardless of the direction of movement of the instrument, the instrument will cross one or more lesions and/or stenosis of the vessel between the point  182  and the point  184 . In that regard, each of the visual depictions of  FIGS. 5-8  is configured to identify the one or more lesions and/or stenosis based on pressure measurements obtained from the instrument as the instrument is moved through the vessel. 
     Referring again to  FIG. 5 , visual representation  180  is a heat map that illustrates changes in pressure measurements obtained as the instrument is moved through the vessel. In that regard, in some instances the pressure measurements shown in the heat map are representative of a pressure differential between a fixed location within the vessel and the moving position of the instrument as the instrument is moved through the vessel. For example, in some instances a proximal pressure measurement is obtained at a fixed location within the vessel while the instrument is pulled back through the vessel from a first position distal of the position where the proximal pressure measurement is obtained to a second position more proximal than the first position (i.e., closer the fixed position of the distal pressure measurement). For clarity in understanding the concepts of the present disclosure, this arrangement will be utilized to describe many of the embodiments of the present disclosure. However, it is understood that the concepts are equally applicable to other arrangements. For example, in some instances, the instrument is pushed through the vessel from a first position distal of the proximal pressure measurement location to a second position further distal (i.e., further away from the fixed position of the proximal pressure measurement). In other instances, a distal pressure measurement is obtained at a fixed location within the vessel and the instrument is pulled back through the vessel from a first position proximal of the fixed location of the distal pressure measurement to a second position more proximal than the first position (i.e., further away from the fixed position of the distal pressure measurement). In still other instances, a distal pressure measurement is obtained at a fixed location within the vessel and the instrument is pushed through the vessel from a first position proximal of the fixed location of the distal pressure measurement to a second position less proximal than the first position (i.e., closer the fixed position of the distal pressure measurement). 
     The pressure differential between the two pressure measurements within the vessel (e.g., a fixed location pressure measurement and a moving pressure measurement) is calculated as a ratio of the two pressure measurements (e.g., the moving pressure measurement divided by the fixed location pressure measurement), in some instances. In some instances, the pressure differential is calculated for each heartbeat cycle of the patient. In that regard, the calculated pressure differential is the average pressure differential across a heartbeat cycle in some embodiments. For example, in some instances where a hyperemic agent is applied to the patient, the average pressure differential across the heartbeat cycle is utilized to calculate the pressure differential. In other embodiments, only a portion of the heartbeat cycle is utilized to calculate the pressure differential. The pressure differential is an average over the portion or diagnostic window of the heartbeat cycle, in some instances. In that regard, in some embodiments a diagnostic window is selected using one or more of the techniques described in U.S. patent application Ser. No. 13/460,296, filed Apr. 30, 2012 and titled “DEVICES, SYSTEMS, AND METHODS FOR ASSESSING A VESSEL,” which is hereby incorporated by reference in its entirety. As discussed therein, the diagnostic windows and associated techniques are particularly suitable for use without application of a hyperemic agent to the patient. In general, the diagnostic window for evaluating differential pressure across a stenosis without the use of a hyperemic agent is identified based on characteristics and/or components of one or more of proximal pressure measurements, distal pressure measurements, proximal velocity measurements, distal velocity measurements, ECG waveforms, and/or other identifiable and/or measurable aspects of vessel performance. In that regard, various signal processing and/or computational techniques can be applied to the characteristics and/or components of one or more of proximal pressure measurements, distal pressure measurements, proximal velocity measurements, distal velocity measurements, ECG waveforms, and/or other identifiable and/or measurable aspects of vessel performance to identify a suitable diagnostic window. 
     In some embodiments, the determination of the diagnostic window and/or the calculation of the pressure differential are performed in approximately real time or live to identify the section  212  and calculate the pressure differential. In that regard, calculating the pressure differential in “real time” or “live” within the context of the present disclosure is understood to encompass calculations that occur within 10 seconds of data acquisition. It is recognized, however, that often “real time” or “live” calculations are performed within 1 second of data acquisition. In some instances, the “real time” or “live” calculations are performed concurrent with data acquisition. In some instances the calculations are performed by a processor in the delays between data acquisitions. For example, if data is acquired from the pressure sensing devices for 1 ms every 5 ms, then in the 4 ms between data acquisitions the processor can perform the calculations. It is understood that these timings are for example only and that data acquisition rates, processing times, and/or other parameters surrounding the calculations will vary. In other embodiments, the pressure differential calculation is performed 10 or more seconds after data acquisition. For example, in some embodiments, the data utilized to identify the diagnostic window and/or calculate the pressure differential are stored for later analysis. 
     By comparing the calculated pressure differential to a threshold or predetermined value, a physician or other treating medical personnel can determine what, if any, treatment should be administered. In that regard, in some instances, a calculated pressure differential above a threshold value (e.g., 0.80 on a scale of 0.00 to 1.00) is indicative of a first treatment mode (e.g., no treatment, drug therapy, etc.), while a calculated pressure differential below the threshold value is indicative of a second, more invasive treatment mode (e.g., angioplasty, stent, etc.). In some instances, the threshold value is a fixed, preset value. In other instances, the threshold value is selected for a particular patient and/or a particular stenosis of a patient. In that regard, the threshold value for a particular patient may be based on one or more of empirical data, patient characteristics, patient history, physician preference, available treatment options, and/or other parameters. 
     In that regard, the coloring and/or other visually distinguishing aspect of the pressure differential measurements depicted in visual representation  180  of  FIG. 5  are configured based on the threshold value. For example, a first color (e.g., green, white, or otherwise) is utilized to represent values well above the threshold value (e.g., where the threshold value is 0.80 on a scale of 0.00 to 1.00, values above 0.90), a second color (e.g., yellow, gray, or otherwise) is utilized to represent values near but above the threshold value (e.g., where the threshold value is 0.80 on a scale of 0.00 to 1.00, values between 0.81 and 0.90), and a third color (e.g., red, black, or otherwise) is utilized to represent values equal to or below the threshold value (e.g., where the threshold value is 0.80 on a scale of 0.00 to 1.00, values of 0.80 and below). It is appreciated that any number of color combinations, scalings, categories, and/or other characteristics can be utilized to visually represent the relative value of the pressure differential to the threshold value. However, for the sake of brevity Applicants will not explicitly describe the numerous variations herein. 
     As shown in  FIG. 5 , the heat map of visual representation  180  utilizes a gray scale where lighter or whiter colors are representative of values above the threshold value, while darker or blacker colors are representative of values near or below the threshold value. In that regard, the heat map of visual representation  180  is based on a cumulative or total pressure differential, where the gray scale color selected for a particular point is determined based on the pressure differential between the instrument at that point being moved through the vessel and the stationary or fixed instrument. As shown, in the illustrated embodiment a transition point or area  186  of the vessel is positioned between a portion  188  of the vessel having pressure differential values above the threshold value and a portion  190  of the vessel having pressure differential values below the threshold value. In that regard, the transition point or area  186  is representative of a boundary of a lesion or stenosis of the vessel that results in an increased pressure differential, which is illustrated by the change in color of the visual representation  180 . As a result, the visual representation  180  can be utilized to both identify the location of the lesion or stenosis within the vessel and assess the severity of the lesion or stenosis. 
     Referring now to  FIG. 6 , shown therein is a visual representation  200  of a vessel profile based on the same pressure measurements as the visual representation  180  of  FIG. 5 . In that regard, the heat map of visual representation  200  also utilizes a gray scale where lighter or whiter colors are representative of values above a threshold value, while darker or blacker colors are representative of values near or below the threshold value. While the heat map of visual representation  180  was based on a cumulative or total pressure differential, the heat map of visual representation  200  is based on a localized pressure differential, where the gray scale color selected for a particular point is determined based on differences between the pressure differential of that point with one or more of the surrounding points. In that regard, the localized pressure differential is calculated as the difference between the immediately preceding point in some instances. For example, the localized pressure differential for point Pn is equal to the cumulative or total pressure differential for point Pn minus the total or cumulative pressure differential for point Pn−1. In other instances, the localized pressure differential is calculated as the difference between that point and a point a fixed amount of time (e.g., 10 ms, 5 ms, 2 ms, 1 ms, or otherwise) or distance (e.g., 10 mm, 5 mm, 2 mm, 1 mm, or otherwise) away from that point. By utilizing a localized pressure differential the location of significant changes in pressure differential values, which are often associated with the presence of a lesion or stenosis, can be identified. 
     For example, as shown in the illustrated embodiment of  FIG. 6 , a transition area  202  of the vessel having localized pressure differential values below the threshold is positioned between portions  204  and  206  of the vessel having pressure differential values above the threshold value. In that regard, the transition point or area  202  is representative of a lesion or stenosis of the vessel that results in a significant change in pressure differential, which is illustrated by the change in color of the visual representation  200 . As a result, the visual representation  200  can be utilized to both identify the location of the lesion or stenosis within the vessel and assess the severity of the lesion or stenosis. 
     Referring now to  FIG. 7 , shown therein is a visual representation  210  of a vessel profile based on the same pressure measurements as the visual representations  180  and  200  of  FIGS. 5 and 6 , respectively. In that regard,  FIG. 7  illustrates a plot  212  of the cumulative or total pressure differential between the instrument being moved through the vessel and an instrument at a stationary or fixed position within the vessel. By analyzing the shape of the plot  212  and, in particular, such characteristics as the pressure differential value relative to the threshold value, changes in the slope of the plot, and/or combinations thereof, the visual representation  210  can be utilized to both identify the location of the lesion or stenosis within the vessel and assess the severity of the lesion or stenosis. 
     Referring now to  FIG. 8 , shown therein is a visual representation  220  of a vessel profile based on the same pressure measurements as the visual representations  180 ,  200 , and  210  of  FIGS. 5, 6, and 7 , respectively. In that regard,  FIG. 8  illustrates a plot  222  that is based on differences between the pressure differential of a point with one or more of the surrounding points. In that regard, the values utilized for plot  222  are calculated as the difference between adjacent points in some instances. For example, the value for point Pn is equal to the cumulative or total pressure differential for point Pn minus the total or cumulative pressure differential for point Pn−1, in some instances. In other instances, the value utilized a particular point of plot  222  is calculated as the difference between the pressure differential for that point and another point a fixed amount of time (e.g., 10 ms, 5 ms, 2 ms, 1 ms, or otherwise) or distance (e.g., 10 mm, 5 mm, 2 mm, 1 mm, or otherwise) away from that point. In the illustrated embodiment, plot  222  is based upon the differences in pressure differential between points 2 mm apart from one another. Utilizing these relative and localized calculations of pressure differential, the location of significant changes in pressure differential values that are associated with the presence of a lesion or stenosis can be identified. 
     The plot  222  can be utilized to both identify the location of lesions or stenosis within the vessel as well as assess the severity of the identified lesions or stenosis. In the illustrated embodiment of  FIG. 8 , a region  224  of the plot  222  does not meet the threshold value indicated by line  226 . In that regard, it should be noted that in  FIG. 8 , the y-axis values of the visual representation  220  go from 1.0 at the origin to 0.0 at the top of the illustrated y-axis. Accordingly, region  224  represents a lesion or stenosis of the vessel that is adversely impacting fluid flow to a degree that requires treatment. Analysis of the plot  222  provides information about the vessel and/or its lesions or stenosis. For example, the plot  222  provides an indication of the length of the lesion or stenosis associated with region  224 . In that regard, the length of the lesion or stenosis is indicated by the length of the vessel segment having values less than the threshold value  226 . In the illustrated embodiment, the length of the vessel segment having values less than the threshold value  226  is approximately 17 mm. The length of the lesion or stenosis as indicated by the plot  222  is based entirely on physiologic measurements that are independent of lesion composition. 
     Further, the plot  222  provides an indication of the overall occlusive value of the vessel. In that regard, the total vessel occlusive value is determined by cumulative area under the plot  222  in some instance. In the illustrated embodiment, the total vessel occlusive value or area under the plot  222  is approximately 1.38. Similarly, the plot  222  also provides an indication of the occlusive value attributable to individual lesions or stenosis of the vessel. In that regard, the occlusive value attributable to a particular lesion or stenosis can similarly be calculated by determining the area under the plot  222  for a length of the vessel associated with the lesion or stenosis. For example, in the illustrated embodiment the lesion or stenosis associated with region  224  has an occlusive value or area under the plot  222  of approximately 0.67. Based on the total vessel occlusive value and the occlusive value attributable to a particular lesion or stenosis, a percentage of the total vessel occlusive value attributable to that particular lesion or stenosis can be calculated. In that regard, the ratio of the occlusive value attributable to the particular lesion or stenosis to the total occlusive value of the vessel provides the percentage of vessel occlusion attributable to that lesion or stenosis. The information regarding characteristics of the lesion or stenosis and/or the vessel as indicated by the plot  222  can be compared with or considered in addition to other representations of the lesion or stenosis and/or the vessel (e.g., IVUS (including virtual histology), OCT, ICE, Thermal, Infrared, flow, Doppler flow, and/or other vessel data-gathering modalities) to provide a more complete and/or accurate understanding of the vessel characteristics. For example, in some instances the information regarding characteristics of the lesion or stenosis and/or the vessel as indicated by the plot  222  are utilized to confirm information calculated or determined using one or more other vessel data-gathering modalities. 
     While the visual representations  180 ,  200 ,  210 , and  220  of  FIGS. 5, 6, 7, and 8  have been described separately. It is understood that a system may display any combination of these visual representations in series, simultaneously, and/or combinations thereof. In some instances, a system provides the user the ability to select which individual visual representation and/or combination of visual representations will be displayed. 
     Referring now to  FIGS. 9-14 , shown therein are aspects of evaluating a vessel according to embodiments of the present disclosure. In that regard,  FIG. 9  provides an angiographic image  300  of a vessel  302  having a plurality of lesions or stenoses. In the illustrated embodiment, four lesions/stenoses are labeled as “A”, “B”, “C”, and “D”. Referring now to  FIG. 10 , shown therein is a graph  310  mapping a pressure ratio value calculated using a diagnostic window in accordance with the present disclosure, which may be referred to as “iFR” in the drawings, relative to a distance as a first instrument is moved through a vessel relative to a second instrument, including across at least one stenosis of the vessel. In that regard, the second instrument is maintained in a position proximal of the at least one stenosis while the first instrument is moved from a position distal of the at least one stenosis to a position proximal of the at least one stenosis and adjacent the second instrument or vice versa (i.e., the first instrument is moved from a position proximal of the at least one stenosis and adjacent the second instrument to a position distal of the at least one stenosis). In the illustrated embodiment of  FIG. 10 , the relative position of the first instrument as depicted in plot  312  transitions from proximal to distal as the plot  312  extends from left to right. 
       FIG. 10  also provides a bar graph  320  that depicts the change in pressure ratio values as depicted in graph  310  over distance. In that regard, the larger bars represent greater changes in pressure ratio value over that distance, which can be indicative of a sever lesion or stenosis. As shown, the bar graph  320  has been annotated to identify regions  322 ,  324 ,  326 , and  328  that have notable changes in pressure ratio values. More specifically, the regions  322 ,  324 ,  326 , and  328  correspond with lesions/stenoses A, B, C, and D of vessel  302 , respectively. 
     Finally,  FIG. 10  also provides an intensity map visual representation  330  (similar to visual representation  180  of  FIG. 5 ) for the vessel  302  based on the pressure ratio values from graph  310 . More specifically, the intensity map  330  identifies a region  332  where the pressure ratio is below the threshold value. In the illustrated embodiment, the threshold pressure ratio value is 0.90. Accordingly, the portions of the intensity map  330  left of region  332  are colored or otherwise visualized to indicate that the pressure ratio is above the threshold value, while the portions of the intensity map within region  332  are colored or otherwise visualized to indicate that the pressure ratio is below the threshold value. In the illustrated embodiment, a green color is utilized to represent values above the threshold value, while a red color is utilized to represent values near or below the threshold value. 
     Referring now to  FIG. 11 , shown therein is an annotated angiographic image  340  of the vessel  302 . In that regard, the angiographic image  300  of  FIG. 9  has been annotated based on the pressure measurements obtained for vessel  302 . More specifically, based on the changes in the pressure ratio along the length of the vessel (e.g., as depicted in the bar graph  320  of  FIG. 10 ) corresponding visual indicators have been added to the angiographic image. In particular, in the illustrated embodiment colored circles have been added along the length of the vessel to provide a visual indication to the user of the amount of change in pressure ratio attributable to that portion of the vessel. In some implementations, the portions of the vessel having a change in pressure ratio less than a threshold value are colored or otherwise visualized to indicate that the change in pressure ratio is below the threshold value, while the portions of the vessel having a change in pressure ratio greater than the threshold value are colored or otherwise visualized to indicate that the change in pressure ratio is above the threshold value. In the illustrated embodiment, a green colored circle is utilized to represent values above the threshold value, while a red colored circle is utilized to represent values near or below the threshold value. 
     Referring now to  FIG. 12 , shown therein is an annotated angiographic image  350  of the vessel  302 . In that regard, the angiographic image  300  of  FIG. 9  has been annotated based on the pressure measurements obtained for vessel  302 . More specifically, based on the changes in the pressure ratio along the length of the vessel (e.g., as depicted in the bar graph  320  of  FIG. 10 ) corresponding visual indicators have been added to the angiographic image. In particular, in the illustrated embodiment dots have been added along the length of the vessel to provide a visual indication to the user of the amount of change in pressure ratio attributable to that portion of the vessel. More specifically, the greater the number of dots adjacent a portion of the vessel, the greater the change in pressure attributable to that portion of the vessel. In that regard, in some implementations the number of dots is directly correlated to values in bar graph  320  of  FIG. 10 . 
     It is understood that numerous other visualization techniques may be utilized to convey the information of the graphs  310 ,  320 , and/or  330  of  FIG. 10  in the context of an angiographic image or other image of the vessel (including both intravascular and extravascular imaging techniques, such as IVUS, OCT, ICE, CTA, etc.) to help the user evaluate the vessel. In that regard, while the examples of the present disclosure are provided with respect to angiographic images, it is understood that the concepts are equally applicable to other types of vessel imaging techniques, including intravascular and extravascular imaging. However, for the sake brevity the present disclosure will limit the examples to angiographic images. 
     In some instances an intensity map (such as described in the context of  FIGS. 5, 6 , and/or  10 ) is overlaid onto or adjacent to the vessel  302  as depicted in angiographic image such that the lesion specific contributions and/or cumulative effects of the lesions can be visualized in the context of the vessel itself. In that regard, it is understood that for any of the visualization techniques the pressure data can be related to the corresponding portions of the vessel  302  using co-registration techniques (such as those disclosed in U.S. Pat. No. 7,930,014, titled “VASCULAR IMAGE CO-REGISTRATION,” which are hereby incorporated by reference in their entirety), based on the known pullback speed/distance, based on a known starting point, based on a known ending point, and/or combinations thereof. Further, in some embodiments the angiographic image is annotated with the numerical values associated with the pressure ratios and/or changes in pressure ratios. In some instances, a threshold value is set by the user or system (e.g., a default setting) such that values above or below the threshold, as the case may be, are identified. In that regard, the identified values can be presented to the user in chart form, added to the angiographic or other image of the vessel in the appropriate location, and/or combinations thereof. Further still, in some embodiments a graph similar to graph  410  and/or graph  420  is overlaid onto the angiographic or other image of the vessel. In that regard, the graph is scaled and oriented (i.e., positioned, rotated, and/or mirror imaged) to align with the general or average pathway of the vessel as depicted on the angiographic or other image of the vessel. In some implementations, diagnostic information and/or data is correlated to vessel images using techniques similar to those described in U.S. Provisional Patent Application No. 61/747,480, titled “SPATIAL CORRELATION OF INTRAVASCULAR IMAGES AND PHYSIOLOGICAL FEATURES” and filed Dec. 31, 2012, which is hereby incorporated by reference in its entirety. 
     In some instances, a user is able to select what information should be included or excluded from the displayed image. In that regard, it should be noted that these visualization techniques related to conveying the pressure measurement data in the context of an angiographic or other image of the vessel can be utilized individually and in any combinations. For example, in some implementations a user is able to select what visualization mode(s) and/or portions thereof will be utilized and the system outputs the display accordingly. Further, in some implementations the user is able to manually annotate the displayed image to include notes and/or input one or more of the measured parameters. 
     Referring now  FIG. 13 , shown therein is a graph  360  that includes a plot  362  representative of simulated pressure ratio value calculations for a proposed treatment option for vessel  302  along with the plot  312  of the original pressure ratio value calculations. In that regard, the plot  362  is based upon removing the effects of lesion/stenosis C of vessel  302  based on a percutaneous coronary intervention (PCI), which may include angioplasty, stenting, and/or other suitable intervention to treat lesion/stenosis C of vessel  302 . In that regard,  FIG. 13  also provides a bar graph  370  that depicts the change in pressure ratio values that also removes the effects of lesion/stenosis C of vessel  302 . In particular, bar graph  370  is similar to bar graph  320  of  FIG. 10 , but the region  326  associated with lesion/stenosis C of bar graph  320  has been replaced with region  372  representative of lesion/stenosis C being treated. In particular, treated lesion/stenosis C is shown to cause no change in the pressure ratio. Finally,  FIG. 13  also provides an intensity map visual representation  380  for the vessel  302  based on the estimated pressure ratio values associated with the treatment of lesion/stenosis C. As shown, the proposed treatment of lesion/stenosis C causes estimated pressure ratio along the full length of the vessel  302  to be above the threshold value of 0.90. Thus, the entire intensity map is colored or otherwise visualized to indicate that the pressure ratio is above the threshold value as there are no portions below the threshold value. In the illustrated embodiment, a green color is utilized to represent values above the threshold value. 
     In addition to the graphical visualizations of the proposed treatment options as shown in  FIG. 13 , the proposed treatment options can also be visualized on the angiographic or other image of the vessel. For example,  FIG. 14  is an angiographic image of the vessel  302  annotated to include a proposed stent  392  across lesion/stenosis C. Further, it should be noted that the various other visualization techniques utilized to convey the information of the pressure measurements of the vessel  302  may also be applied to the estimated pressure measurements for the simulated treatment options, including various combinations of those visualization techniques as described above. 
     In some instances, the pre-treatment pressure measurement information, such as shown in  FIGS. 10-12 , is compared to corresponding post-treatment pressure measurement information. In that regard, the difference between the pre-treatment and post-treatment measurement information will indicate whether the treatment achieved the desired functional gain of allowing the blood to flow through the vessel. Likewise, the post-treatment pressure measurement information can be compared to the estimated pressure measurement information for the simulated treatment, such as shown in  FIG. 13 . In that regard, the differences between the estimated measurement information and the actual post-treatment measurement information will provide an indication of the accuracy of the estimated measurement information for the simulated treatment. In that regard, in some instances the differences between estimated measurement information and actual post-treatment measurements are stored by the system and utilized to modify future estimated measurement information for similar treatment options. In some instances, the system is configured to automatically link or coordinate the pressure data and corresponding vessel locations between the pre-treatment, simulated treatment, and/or post-treatment measurement information. In that regard, it is understood that the pressure data can be related to the corresponding portions of the vessel using co-registration techniques (such as those disclosed in U.S. Pat. No. 7,930,014, titled “VASCULAR IMAGE CO-REGISTRATION,” which is hereby incorporated by reference in their entirety), based on the known pullback speed/distance, based on a known starting point, based on a known ending point, and/or combinations thereof. 
     Referring now to  FIGS. 15-19 , shown therein are aspects of evaluating a vessel according to embodiments of the present disclosure. In that regard,  FIG. 15  provides an angiographic image  400  of a vessel  402  having a plurality of lesions or stenoses. In the illustrated embodiment, four lesions/stenoses are labeled as “E”, “F”, “G”, “H”, and “I”. 
     Referring now to  FIG. 16 , shown therein is a graph  410  mapping a pressure ratio value calculated using a diagnostic window in accordance with the present disclosure, which may be referred to as “iFR” in the drawings, relative to a distance as a first instrument is moved through a vessel relative to a second instrument, including across at least one stenosis of the vessel. In that regard, the second instrument is maintained in a position proximal of the at least one stenosis while the first instrument is moved from a position distal of the at least one stenosis to a position proximal of the at least one stenosis and adjacent the second instrument or vice versa (i.e., the first instrument is moved from a position proximal of the at least one stenosis and adjacent the second instrument to a position distal of the at least one stenosis). In the illustrated embodiment of  FIG. 16 , the relative position of the first instrument as depicted in plot  412  transitions from proximal to distal as the plot  412  extends from left to right.  FIG. 16  also provides a bar graph  420  that depicts the change in pressure ratio values as depicted in graph  410  over distance. In that regard, the larger bars represent greater changes in pressure ratio value over that distance, which can be indicative of a sever lesion or stenosis. As shown, the bar graph  420  has been annotated to identify regions  422 ,  424 ,  426 ,  428 , and  430  that have notable changes in pressure ratio values. More specifically, the regions  422 ,  424 ,  426 ,  428 , and  430  correspond with lesions/stenoses E, F, G, H, and I of vessel  402 , respectively. 
     Referring now to  FIG. 17 , shown therein is a three dimensional model  440  of the vessel  402  based on the pressure measurement information of  FIG. 16 . In that regard, the three dimensional model  440  has been colored or otherwise visualized based on the pressure measurements obtained for vessel  402 . More specifically, based on the changes in the pressure ratio along the length of the vessel (e.g., as depicted in the bar graph  420  of  FIG. 16 ) the corresponding portions of the three dimensional model  440  are colored accordingly. In that regard, in the illustrated embodiment the color of a particular portion of the three dimensional model  440  provides a visual indication to the user of the amount of change in pressure ratio attributable to that portion of the vessel. In some implementations, the portions of the vessel having a change in pressure ratio less than a threshold value are colored or otherwise visualized to indicate that the change in pressure ratio is below the threshold value, the portions of the vessel having a change in pressure ratio greater than the threshold value are colored or otherwise visualized to indicate that the change in pressure ratio is above the threshold value, and the portions of the vessel having a change in pressure ratio approximately equal to the threshold value are colored or otherwise visualized to indicate such. In the illustrated embodiment, blue colors are utilized to represent values above the threshold value, red colors are utilized to represent values below the threshold value, while orange, yellow, and green colors are utilized to represent values approximately equal to the threshold (e.g., orange for slightly below the threshold, yellow for equal to threshold, and green for slightly above the threshold). 
     Referring now to  FIG. 18 , shown therein is a three dimensional model  450  of the vessel  402  based on the pressure measurement information of  FIG. 16 . In that regard, the three dimensional model  450  has been colored or otherwise visualized based on the pressure measurements obtained for vessel  402 . More specifically, based on the changes in the pressure ratio along the length of the vessel (e.g., as depicted in the bar graph  420  of  FIG. 16 ) the corresponding portions of the three dimensional model  450  having significant changes in pressure are colored accordingly. In other words, hot spots indicative of functionally significant lesions/stenoses are highlighted by use of different colors or other visualization techniques. For example, in some instances the three dimension model  450  is colored or visualized in a similar manner to the visual representation of  FIG. 6 . In the illustrated embodiment of  FIG. 18 , two significant lesions/stenosis  452  and  454  are highlighted by the visualization of three dimensional model  450 . 
     It should be noted that the three dimensional models  440  and  450  of the vessel  402  may be based on data from one or more imaging techniques, including both intravascular and extravascular imaging techniques, such as angiography, CT scans, CTA, IVUS, OCT, ICE, and/or combinations thereof. Generally, any three dimensional modeling technique may be utilized and the corresponding measurement data applied thereto in accordance with the present disclosure. In that regard, in addition to and/or in lieu of the specific embodiments shown in  FIGS. 17 and 18 , any of the visualization techniques described above with respect to other imaging modalities may also be applied to the three dimensional models. In that regard, in some instances a user is able to select what information should be included or excluded from the displayed three dimensional model. In some implementations, the three dimensional model is displayed adjacent to a corresponding two dimensional depiction of the vessel. In that regard, the user may select both the type of depiction(s) (two dimensional (including imaging modality type) and/or three dimensional) along with what visualization mode(s) and/or portions thereof will be utilized. The system will output a corresponding display based on the user&#39;s preferences/selections and/or system defaults. 
     Referring now  FIG. 19 , shown therein is a graph  460  that includes a plot  462  representative of simulated pressure ratio value calculations for a proposed treatment option for vessel  402  along with the plot  412  of the original pressure ratio value calculations. In that regard, the plot  462  is based upon removing the effects of lesion/stenosis E of vessel  402  based on a percutaneous coronary intervention (PCI), which may include angioplasty, stenting, and/or other suitable intervention to treat lesion/stenosis E of vessel  402 . In that regard,  FIG. 19  also provides a bar graph  470  that depicts the change in pressure ratio values that also removes the effects of lesion/stenosis E of vessel  402 . In particular, bar graph  470  is similar to bar graph  420  of  FIG. 16 , but the region  422  associated with lesion/stenosis E of bar graph  420  has been replaced with region  472  representative of lesion/stenosis E being treated. In particular, treated lesion/stenosis E is shown to cause no change in the pressure ratio. Finally,  FIG. 19  also provides an intensity map visual representation  480  for the vessel  402  based on the estimated pressure ratio values associated with the treatment of lesion/stenosis E. As shown, the proposed treatment of lesion/stenosis E causes estimated pressure ratio along the full length of the vessel  402  to be above the threshold value of 0.90. Thus, the entire intensity map is colored or otherwise visualized to indicate that the pressure ratio is above the threshold value as there are no portions below the threshold value. In the illustrated embodiment of  FIG. 19 , a green color is utilized to represent values above the threshold value. 
     Persons skilled in the art will also recognize that the apparatus, systems, and methods described above can be modified in various ways. Accordingly, persons of ordinary skill in the art will appreciate that the embodiments encompassed by the present disclosure are not limited to the particular exemplary embodiments described above. In that regard, although illustrative embodiments have been shown and described, a wide range of modification, change, and substitution is contemplated in the foregoing disclosure. It is understood that such variations may be made to the foregoing without departing from the scope of the present disclosure. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the present disclosure.