Guiding Medical Instruments During Medical Procedures

Techniques and technologies for guiding medical instruments during medical procedures using real-time imaging technologies are disclosed. A representative apparatus includes a medical instrument, an imaging system, a stage assembly, and a control system. The medical instrument includes an elongated portion configured to be inserted into a body portion and having an optical fiber that includes a tip portion that is extendable beyond a distal end of the elongated portion. The imaging system provides a sampling energy that is emitted from the tip portion. The stage assembly actuates the tip portion to perform scanning of one or more tissues with the sampling energy. The imaging system receives a reflected energy, providing a plurality of one-dimensional arrays of intensity values of the reflected energy. The control system analyzes the plurality of one-dimensional arrays of intensity values to determine a shape and a location of the target tissue, and displays information for guiding the medical instrument into engagement with the target tissue.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to techniques and technologies for guiding medical instruments during medical procedures using real-time imaging technologies.

BACKGROUND

Many medical procedures typically involve the insertion of a medical instrument into a patient. Insertion of a needle or a catheter into a vein or other lumen of the patient's body for the administration of medication or the collection of blood are representative examples of such routine medical procedures. Although such procedures are commonplace and indispensable, they nevertheless have an imperfect success rate even among experienced medical practitioners. Accordingly, techniques and technologies that improve the success rate of such ubiquitous medical procedures would provide substantial benefit.

SUMMARY

The present disclosure teaches techniques and technologies for guiding medical instruments during medical procedures using real-time imaging technologies.

Techniques and technologies in accordance with the present disclosure provide guidance for medical practitioners for guiding medical instruments during medical procedures using real-time imaging. Such guidance information may advantageously improve the performance of medical procedures by enabling such procedures to be performed more accurately, more reliably, and with less repetition in comparison with prior art techniques. Accordingly, techniques and technologies in accordance with the present disclosure may provide substantially improved satisfaction of medical practitioners and patients in comparison with prior art practices and procedures.

More specifically, in at least some implementations, an apparatus for guiding medical instruments during medical procedures comprises a medical instrument, an imaging system, a stage assembly, and a control system. The medical instrument may include an elongated portion configured to be inserted into a body portion of a patient and having an optical fiber disposed within the elongated portion. The optical fiber has a tip portion that is extendable beyond a distal end of the elongated portion. The imaging system is configured to provide a sampling energy into the optical fiber, the sampling energy being emitted from the tip portion along a sampling vector at a deflection angle with the longitudinal axis as the elongated portion is inserted into the body portion. The stage assembly may actuate the optical fiber and the tip portion to perform a scanning of one or more tissues with the sampling energy emitted from the tip portion. More specifically, the stage assembly is configured to rotate the tip portion about a scanning axis that is parallel with the longitudinal axis and to reciprocate the tip portion along the scanning axis that is parallel with the longitudinal axis with the tip portion proximate to and extended beyond the distal end of the elongated portion. The sampling energy is emitted from the tip portion in a scanning pattern. The imaging system receives a reflected energy that is reflected from the one or more tissues back through the optical fiber, providing a plurality of one-dimensional arrays of intensity values of the reflected energy at a plurality of distances along the sampling vector. The control system analyzes the plurality of one-dimensional arrays of intensity values of the reflected energy to determine a shape of a target tissue and a location of the target tissue, and displays information including one or more relative positions of the target tissue relative to the elongated portion of the medical instrument for guiding the medical instrument into engagement with the target tissue as the elongated portion is inserted into the body portion for performance of the medical procedure.

Similarly, in at least some implementations, a method for performing a medical procedure in accordance with the present disclosure includes: engaging a medical instrument with a body portion of a patient, the medical instrument including an elongated portion configured to be inserted into the body portion and having an optical fiber at least partially disposed within the elongated portion, the optical fiber having a tip portion that is extendable beyond a distal end of the elongated portion; actuating an imaging system that provides a sampling energy into the optical fiber, the sampling energy being emitted from the tip portion along a sampling vector at a deflection angle with the longitudinal axis into one or more tissues of the body portion as the elongated portion is inserted into the body portion, the one or more tissues including a target tissue; and actuating a stage assembly to move the tip portion to perform a scanning of the one or more tissues with the sampling energy emitted from the tip portion, the stage assembly rotating at least the tip portion about a scanning axis that is parallel with the longitudinal axis and reciprocating at least the tip portion along the scanning axis that is parallel with the longitudinal axis with the tip portion proximate to and extended beyond the distal end of the elongated portion, the sampling energy being emitted from the tip portion in a scanning pattern. The method further includes receiving a reflected energy that is reflected from the one or more tissues back through the optical fiber to the imaging system, the reflected energy providing a plurality of one-dimensional arrays of intensity values of the reflected energy at a plurality of distances along the sampling vector; analyzing the plurality of one-dimensional arrays of intensity values of the reflected energy to determine a shape of the target tissue and a location of the target tissue relative to the elongated portion of the medical instrument; and displaying information including one or more relative positions of the target tissue relative to the elongated portion of the medical instrument for guiding the medical instrument into engagement with the target tissue as the elongated portion is inserted into the body portion for performance of the medical procedure.

This summary is intended to provide an introduction of a few exemplary aspects of implementations in accordance with the present disclosure. It is not intended to provide an exhaustive explanation of all possible implementations, and should thus be construed as merely introductory, rather than limiting, of the following disclosure.

DETAILED DESCRIPTION

Techniques and technologies for guiding medical instruments during medical procedures using real-time imaging technologies will now be disclosed. In the following description, many specific details of certain implementations are described and shown in the accompanying figures. One skilled in the art will understand that the present disclosure may have other possible implementations, and that such other implementations may be practiced with or without some of the particular details set forth in the following description.

FIG. 1shows a schematic view of a system100for performing a medical procedure using real-time imaging in accordance with an embodiment of the present disclosure. In this embodiment, the system100includes a control system110operatively coupled to an imaging system120and a stage assembly130. The control system110includes a computing component112that transmits control signals via conductive leads114to control operation of the imaging system120and the stage assembly130. More specifically, the control system110may include logic in the form of software, firmware, hardware, or combinations thereof, that collects imaging data from the imaging system120and position data from the stage assembly130, and performs geometric reconstructions described below. In the embodiment shown inFIG. 1, the control system110includes one or more user input devices116(e.g. keyboard, mouse, etc.) to enable user operation of the system100, and a display device118for displaying one or more real-time images160for guiding medical instruments during medical procedures as described more fully below.

The system100further includes a first optical fiber122that extends from the imaging system120to the stage assembly130, and a second optical fiber132that extends within a sheath134to a handheld component140. The sheath134is preferably a flexible sheath that surrounds the second optical fiber132and enables a user (e.g. a nurse, medical practitioner, etc.) to move within the environment for positioning the handheld component140at one or more desired locations proximate to a body portion150of a patient (e.g. an arm). In the embodiment shown inFIG. 1, the handheld component140includes a needle142that is configured for insertion into the body portion150of the patient, such as for intravenous administration of a medication. The second optical fiber132is loosely captured within the sheath134and is free to translate along its longitudinal axis within the sheath134(as indicated by double arrow136) such that a tip138of the second optical fiber132may be extended through the handheld component140and beyond an end of the needle142, or may be retracted toward the handheld component140into the needle142.

The imaging system120may be any of a wide variety of suitable imaging systems. For example,FIG. 2shows a schematic view of the imaging system120in accordance with an embodiment of the present disclosure. In this embodiment, the imaging system120is based on optical coherence tomography. Optical coherence tomography (OCT) is a well-documented imaging modality that may use low-coherence interferometry to obtain three-dimensional, relatively high-resolution images of biological tissue at depths of a few millimeters. It will be appreciated that OCT systems may be configured in a variety of suitable configurations, and that the imaging system120shown inFIG. 2is simply one possible embodiment suitable for use with the system100.

In the embodiment shown inFIG. 2, the imaging system120includes a light source202that emits light204toward a deflector component206. Preferably, the light source202is a broad-spectrum light source in the near infrared or infrared band to enable optimal depth of penetration into human tissue. The deflector component206splits the incoming light204into a reference light208that is reflected toward a reference mirror210, and a sampling light212that is emitted out of the imaging system120into the first optical fiber122. The deflector component206may include one or more interferometers or optical interference systems that operate as described herein, such as a beam splitter, an isolator, a coupler, a circulator, a partially severed mirror with one or more holes therein, or any other suitable components.

As shown inFIG. 2, the reference light208is reflected by the reference mirror210back to the deflector component206. The sampling light212exits the imaging system120and transits via the stage assembly130and the second optical fiber132(shown inFIG. 1) toward a sample that is to be imaged, such a tissue of the body portion150of the patient. A portion of the sampling light212is reflected from the sample and returns to the imaging system120(via the second optical fiber132and the stage assembly130) as a reflected light214. Because the reflected light214and the reference light208have traveled different optical path lengths, the reflected light214and the reference light208combine (or re-combine) at the deflecting component206to generate a combined light216that includes an interference (or fringe) pattern that is received by a detection component218. The detection component218may include, for example, one or more photodiodes, photodetectors, multi-array cameras, or other suitable components. The detection component218senses the combined light216and transmits an imaging signal220that is output from the imaging system120to the control system110for further processing. Using known, well-established processing techniques (e.g. Fourier analysis, etc.), the control system110may process the imaging signal220output from the imaging system120into one or more images for display on the display device118, as described more fully below.

It should be appreciated that the imaging system120shown inFIG. 2is just one possible embodiment of an OCT-based imaging system that is suitable for use in the system100, and that numerous alternate embodiments may be conceived and employed. For example, suitable alternate embodiments of OCT-based imaging systems are described in U.S. Pat. No. 10,323,926 issued to Elmaanaoui et al., U.S. Pat. No. 9,593,935 issued to Osawa et al., U.S. Pat. No. 8,811,702 issued to Kurosaka et al.,In Vivo Endoscopic Optical Biopsy with Optical Coherence Tomographyby Guillermo et al., published in the journalScienceat vol. 276:2037-2039, and inHigh Resolution In Vivo Intra-Arterial Imaging With Optical Coherence Tomographyby Fujimoto et al., published in the journalHeart1999 at vol. 82:128-133, which publications are incorporated herein by reference.

Furthermore, it should be appreciated that alternate imaging systems other than OCT-based imaging systems may also be suitable for use in the system100. Imaging systems that employ other imaging modalities that collect a set of three-dimensional surface data in order to identify a cylindrical object may also be employed in accordance with the teachings of the present disclosure. More specifically, in at least some implementations, such alternate imaging systems may operate in accordance with the present disclosure by being capable of providing a one dimensional array of signal intensities along a vector in three dimensional space, originating from the tip138of the second optical fiber132and extending a suitable distance (e.g. a few millimeters) forward therefrom, as will be described more fully below.

Similarly, the stage assembly130may be any one of a wide variety of suitable assemblies. For example,FIG. 3shows a schematic view of the stage assembly130of the system100ofFIG. 1in accordance with an embodiment of the present disclosure. In this embodiment, the stage assembly130includes a fiber optic rotary joint (FORJ)302having a first portion304coupled to the first optical fiber122and a second portion306coupled to the second optical fiber132. The sampling light212emitted by the imaging system120enters the stage assembly130via the first optical fiber122, traverses through the fiber optic rotary joint302, and exits from the stage assembly130through the second optical fiber132. Similarly, the reflected light214that is reflected from the sample (e.g. a tissue of the body portion150of the patient) enters the stage assembly130via the second optical fiber132, traverses through the fiber optic rotary joint302, and exits from the stage assembly130through the first optical fiber122en route to the imaging system120.

As further shown inFIG. 3, a rotation stage motor308is operatively coupled to the second portion306of the fiber optic rotary joint302to cause rotation of the second portion306(and the second optical fiber132) relative to the first portion304. In addition, a translation stage motor310is operatively coupled to the fiber optic rotary joint302to cause translation of the fiber optic rotary joint302(and the second optical fiber132) in forward and rearward directions along a longitudinal axis315of the second optical fiber132(as indicated by double arrow136). At a first end of the second optical fiber132proximate to the stage assembly130, the longitudinal axis315of the second optical fiber132is at least approximately collinear (or coincident) with a longitudinal axis317of the FORJ302. A rotation encoder312monitors rotational position and rate of the second portion306(and the second optical fiber132), while a translation encoder314monitors translational position and rate of the second portion306(and the second optical fiber132). More specifically, in at least some implementations, the translation encoder may monitor the translation of the entire FORJ302and the second optical fiber132, as the second portion306has a rotational degree of freedom, but no translational degree of freedom, with respect to the first portion304. The control system110provides control signals to the stage assembly130to control the rotation stage and translation stage motors308,310, and the rotation and translation encoders312,314provide feedback to the control system110to achieve precise control of the rotational and translational movements of the tip138of the second optical fiber132(FIG. 1). In at least some implementations, the sheath134is not rotated or translated by the stage assembly130, but rather, the second optical fiber132is free to rotate and translate within the sheath134

More specifically, in at least some embodiments, the rotation stage motor308rotates the second portion306and the second optical fiber132at a fixed controllable rate, e.g. 10 Hz, around the axis of the second optical fiber132. The rotation encoder312tracks the angular position of the rotation stage motor308and sends a timestamped “index pulse” to the control system110at each full revolution. In addition, in at least some embodiments, the translation stage motor310moves the fiber optic rotary joint302(and the second optical fiber132) forward and backwards, parallel to the longitudinal axis of the second optical fiber132, reciprocating along a triangular waveform. The control system110may control the stage assembly130to controllably adjust the rate and range of translation of the tip138of the second optical fiber132to any suitable values. For example, in at least some implementations, the translation rate may have a value within a range of approximately 0.25 Hz to approximately 2.0 Hz, and the translation range may have a value within a range of approximately 2 millimeters to approximately 8 millimeters. In a particular embodiment, the stage assembly130translates the tip138of the second optical fiber132along a translation range of 6 mm at a rate of approximately 0.5 Hz. The translation encoder310sends continuous time stamped position information to the control system110. As noted above, the second optical fiber132passes through and moves within the sheath134, but note that the sheath134is not translated or rotated by the stage assembly130, and that, in at least some implementations, a proximal end of the sheath134remains fixed with respect to the stage assembly130.

FIG. 4shows a schematic view of the handheld component140of the system100ofFIG. 1in accordance with an embodiment of the present disclosure. The handheld component140is connected to the sheath134but is not directly connected to the second optical fiber132so that the handheld component140and the needle142are not affected by the rotational and translational motion of the second optical fiber132. As noted above, the second optical fiber132is configured to translate along the longitudinal axis315of the second optical fiber132(as indicated by double arrow136) such that the tip138of the second optical fiber132may be extended through the handheld component140and beyond the end of the needle142. At locations proximate to the tip138, in at least some implementations, the longitudinal axis315of the second optical fiber132is collinear (or coincides) with a longitudinal axis144of the needle142. Therefore, the stage assembly130rotates and translates the tip138of the second optical fiber132along the longitudinal axis144relative to the needle142. As further shown inFIG. 4, the tip138is configured so that the sampling light212traversing the second optical fiber132is emitted by the tip138at a deflection angle phi (or4) with respect to the longitudinal axis144of the needle142. For example, in at least some embodiments, the tip138contains a lens that deflects the sampling light212along the deflection angle phi.

Although the handheld component140is described herein as having the needle142for intravenous insertion into the body portion150of the patient, it should be appreciated that the handheld component140may have alternate configurations. For example, in alternate embodiments, the handheld component140may be a catheter that is configured for insertion into any suitable lumen or body portion.

The operations performed by the system100for guiding medical instruments during medical procedures using real-time imaging technologies may use a variety of suitable reference systems. For example,FIG. 5shows a coordinate system500associated with the handheld component140of the system100ofFIG. 1in accordance with an embodiment of the present disclosure. In this embodiment the coordinate system500is a three-dimensional (3D) cartesian coordinate system defined by the distal end of the needle142. Although the needle may move while the target remains stationary in practice, in at least some implementations, the coordinate system500may be defined such that the needle142remains stationary with respect to the coordinate system500and all else moves around it. The origin502lies on the longitudinal axis144(of the needle142and the approximately collinear second optical fiber132), with the z axis collinear to the longitudinal axis144and pointed distally, such that a distal-most point504of a needle bevel506lies in the xy plane (z=0). The y axis is defined pointing directly towards the distal-most point (or bevel tip)504, while the x axis is normal to y and z according to the right hand rule. For further simplification, the positive x direction is referred to as “right”, with positive y and positive z referred to as “down” and “forward” respectively.

In at least some implementations, the position of the second optical fiber132(and the tip138) may be defined using a mix of cartesian and radial coordinate conventions. First, the longitudinal axis144of the second optical fiber132is collinear to the axis of the needle142(i.e. z axis) as previously defined. Activity by the translation stage motor310of the stage assembly130will translate the tip138forward and back along the z axis, with the translation encoder314tracking the z value of the tip138. As noted above, the tip138will deflect the sampling light212along a light vector508transmitted from the tip138at the deflection angle phi with respect to the z axis (seeFIG. 4). In at least some embodiments, the deflection angle phi may be 60 degrees, although other suitable angles may be used. In at least some implementations, for example, the deflection angle phi may have a fixed value within a range of approximately 30 degrees to approximately 90 degrees.

Furthermore, the rotation motor308rotates a light vector of the sampling light212around the z axis by a rotation angle theta (or Θ). By convention, the rotation encoder312defines the rotation angle theta=0 when the exit vector (or light vector508) lies in the yz plane and the exit vector has a negative y component. In other words, when rotation angle theta=0, the light vector508points “up” as shown inFIG. 5. In at least some implementations, the rotation encoder312sends the aforementioned index pulse every time theta crosses 0 degrees, indicating one revolution of the second optical fiber132.

From the aforementioned values, the light vector508of the sampling light212emitted by the tip138of the second optical fiber132may be defined. The light vector508originates from a cartesian position (0,0,z0), with the value z0 controlled by the translation motor310and recorded by the translation encoder314. The light vector508always forms the deflection angle phi with the z axis that remains constant, and a projection of the light vector508in the xy plane makes the rotation angle theta with respect to the −y axis (seeFIG. 5). The imaging system120will measure signal intensity at several distances “r” along the length of the light vector508, with distances “r” ranging from 0 to a few millimeters in the case of OCT. Therefore, any measured position in space defined by the ordered triplet (r, theta,z0) can be resolved to a cartesian value (X,Y,Z).

Although for the sake of clarity, the foregoing discussion has described the tip138of the second optical fiber132as being located on the longitudinal axis144of the needle142, it will be appreciated that this is merely one possible implementation, and that in alternate implementations, the second optical fiber132and the tip138may be radially offset from the longitudinal axis144. For example, in at least some implementations, the second optical fiber132may be positioned along a sidewall of the needle142such that the tip138is offset from the longitudinal axis144by a predetermined radial distance. During data processing (analysis and imaging) operations described herein, such an offset of the tip138from the longitudinal axis144may be readily taken into account in the data reduction algorithms performed by the control system110. Thus, whenever the tip138of the second optical fiber132is described and shown in the accompanying figures as being located on the longitudinal axis144of the needle142, it will be appreciated that this is one possible implementation, and that in alternate implementations the tip138may be offset from the longitudinal axis144by a predetermined radial distance. In such alternate implementations, a more generalized description applies, wherein the tip138is rotated by the stage assembly130about a scanning axis that is parallel with the longitudinal axis144of the needle142, and is reciprocated by the stage assembly130along the scanning axis that is parallel with the longitudinal axis144of the needle142. In at least some implementations, as previously noted, the scanning axis is collinear with the longitudinal axis144of the needle142(or other elongated medical instrument).

FIG. 6shows a process600for performing a medical procedure using real-time imaging in accordance with an embodiment of the present disclosure. In this embodiment, the process600includes initiating a system (e.g. system100ofFIGS. 1-5) for guiding a medical instrument during a medical procedure using real-time imaging at610. More specifically, in at least some implementations, the initiating (at610) includes activating the imaging system120and the stage assembly130of the system100, such as by causing the control system110to transmit control signals to these components so that the tip138is rotated about the z axis, and the sampling light212provided by the imaging system120is emitted from the tip138, as shown inFIG. 5. In at least some implementations, the initiating (at610) does not include causing the stage assembly130to translate the tip138in a reciprocating manner, and the tip138may remain withdrawn into the needle142during the initiating (at610).

The process600further includes positioning a medical instrument proximate to a body portion of a patient at612. For example, in at least some implementations, the positioning of the medical instruction (at612) may include a healthcare provider positioning the handheld component140of the system100so that the needle142is proximate to an arm or other body portion150of the patient.

Next, the process600includes advancing the medical instrument into engagement with a body portion of the patient at613. In at least some implementations, the advancing (at613) includes advancing the handheld component140until the needle142starts to penetrate a skin surface of the body portion150of the patient. More specifically,FIG. 7shows the needle142of the handheld component140positioned in a first position700with respect to the body portion150of the patient. In the first position700, the needle142has penetrated the skin702of the body portion150.

As further shown inFIG. 6, the process600further includes performing scanning of the body portion150of the patient at614. For example, in at least some implementations, once the medical instrument has been advanced to a suitable position for scanning (e.g. the needle142has penetrated the skin702as shown inFIG. 7), the control system110may activate the translation motor310of the stage assembly130so that the tip138of the second optical fiber132is advanced beyond the bevel tip504of the needle142, and reciprocating translation is initiated, causing the tip138to both rotate and reciprocate as indicated by double arrow136ofFIG. 5. During the performing of the scanning (at614), the sampling light212emitted by the tip138of the second optical fiber132may impinge upon and penetrate the tissues of the body portion150such that a target vein704located below the skin702(FIG. 7) is at least partially illuminated by the sampling light212. The reflected light214may then be reflected from the target vein704and other tissues of the body portion150and returned along the second optical fiber132(and first optical fiber130) to the imaging system120. Accordingly, in at least some implementations, the scanning (at614) includes collecting and recording intensity data associated with the reflected light214that is reflected from the tissue(s) of the body portion150and returned to the imaging system120(and to the control system110), as described more fully below.

It will be appreciated that in alternate implementations, operations of the process600may be altered, combined, or performed in a different order. For example, the initiating of the rotation of the tip138by the stage assembly130, and the initiating of the imaging system120, may occur during the performing of the scanning (at614) rather than at the initiating of the system (at610). Thus, the operations described herein may be combined or performed in a different order without departing from the scope of the present disclosure.

In addition, it should be appreciated that a variety of suitable scanning procedures (at614) may be employed. For example, in at least some implementations, the rotation motor308rotates the second optical fiber132, and consequently the light vector508emitted from the tip138, along the rotation angle theta at a constant rate, while the translation motor310reciprocates the linear position of the tip138along the z axis (i.e. value z0) in a triangular waveform. This causes the light vector508(FIG. 5) of sampling light212to sweep a reciprocating helical pattern into the tissues in the region near the tip138and correspondingly near a tip of the medical instrument, such as the bevel506of the needle142shown inFIG. 5. The translation motion may be controllably adjusted (e.g. by the control system110) so that z0 tracks from z=0 to some suitable positive value. Similarly, the rotational velocity of the rotation motor308may be controllably adjusted such that the tip138performs several revolutions about the rotation angle theta for each leg of the translational motion of the tip138.

In addition, in at least some implementations, the imaging system120(and control system110) continuously captures a one-dimensional array (or “aLine”) of signal intensity at various distances r along the light vector508. Each aLine captured during rotation of the tip138at successive rotational angles theta corresponds to the same domain of r values, but will have different values for theta and z0 caused by the rotation and translation motors308,310. The control system110may collect aLines continuously, but may separate them into batches as the rotation encoder312transmits index pulses, with each index pulse corresponding to one revolution of the rotation motor308(or tip138). These batches are referred to as bScans. Each bScan may be rendered into an image, with each column in the image representing a single aLine. Each row in the image has the same r value, which is determined by OCT physics and does not change between aLines. Based on the timestamps of the incoming aLines, interpolated with the timestamps of the linear encoder data, each aLine is assigned a z0 value. Based on the timestamps of the incoming aLines, interpolated with the timestamps of the rotation encoder312index pulses, and assuming a constant rotational velocity of the rotation motor308, each column is assigned a theta value. Therefore, for any pixel in any bScan, values of (r, theta,z0) and corresponding voxels with cartesian coordinates (X,Y,Z) may be calculated.

For example,FIG. 8shows a representative image800acquired by the imaging system during a scanning operation (at614) in accordance with an embodiment of the present disclosure. More specifically, the representative image800shows a representative bScan of intensity data in a rasterized configuration. In this representative image800, the target vein (or blood vessel)704is represented by the relatively brighter (or “shark fin”) shape802. The position of the tip138is approximately along a top row of the image800. Scanning from top to bottom, an outer wall of the target vein (or blood vessel)704is approximately along a top edge of the relatively brighter shape802, while an interior lumen of the target vein (or blood vessel)704is along an underside of the shape802as the intensity fades to black.

Referring again toFIG. 6, the process600further includes analyzing imaging data (collected during scanning operations at614) to determine a cylindrical shape of the target tissue within the body portion of the patient at616. For example, in at least some implementations, the intensity data gathered in the form of bScans during the scanning operations (at614) are analyzed using the control system110to approximate the target vein704as a cylindrical shape in the region near the tip138in real-time during the performance of the medical procedure.

More specifically, using image processing techniques (discussed more fully below), each bScan is analyzed to identify the pixels that contain the “outer” surface of the target vein704(FIG. 7) (or other blood vessel or target structure) within the body portion150of the patient. These pixels may be assembled in list format and the (X,Y,Z) voxels are identified. As the system100collects multiple bScans, the system100may store a rolling list of voxels (e.g. in memory of the control system110) from a desired value “n” of bScans (e.g. n=5). In at least some implementations, each time the list may be updated by adding a new bScan and purging the oldest stored bScan, the processing techniques performed by the control system110may determine a cylinder geometry of the target vein704(or other target tissue) by inputting the ordered triplets, (e.g. starting at Equation 14, described more fully below). In addition, processing techniques performed by the control system110will calculate the parameters of the cylinder of the target vein704(or target tissue), including an axis and radius. In at least some implementations, the cylindrical shape of the target vein704may be defined (at616) using five parameters as follows. A central axis of the cylinder is defined as passing through the cartesian points (X0,Y0,0) and (X1,Y1,1), and the cylinder has a radius R.

Referring again toFIG. 6, the process600further includes displaying information for guiding the medical instrument with respect to the target tissue at618. For example, in at least some implementations, the displaying (at618) includes transmitting the calculated values of the five parameters (X0,Y0,X1,Y1,R) to a visualization program of the control system110that renders the cylindrical shape of the target vein704in a graphic display relative to the needle142of the handheld component140, and then displaying a real-time image160on the display device118of the control system110that assists the medical practitioner in guiding the needle142during performance of the medical procedure.

FIG. 9shows a first view900displayed by the display device118of the control system110during the medical procedure in accordance with an embodiment of the present disclosure. In at least some implementations, the first view900includes a displayed blood vessel902, which is a representation of the computed cylindrical shape of the vein704resulting from the analysis (at616) as the handheld component140is positioned at the first position700proximate to the vein704(FIG. 7). The first view900also includes a displayed needle910, which is a representation of the needle142(or other medical instrument).

As further shown inFIG. 9, the first view900may include a forward view904which shows the alignment of the bevel506and the bevel tip504, providing “roll” guidance to the user as to which way to roll (or rotate) the handheld component140(e.g. in degrees) to place the bevel tip504at the desired position (e.g. bevel tip504closest to the skin702of the body portion150, or bevel506up, etc.). In at least some implementations, the “roll” position of the medical instrument (e.g. needle142) may not be critical to the medical procedure such that the medical practitioner may keep the roll orientation relatively constant over the course of the medical procedure.

With continued reference toFIG. 9, a top view906may also be included which provides alignment guidance to the user, showing whether the needle142is aligned (in the xz plane) with the longitudinal axis of the vein704. The top view906may also provide distance to the vein704(e.g. in millimeters) and angular mis-alignment (e.g. in degrees). Similarly, a side view908may also be included which provides pitch alignment guidance to the user, showing the angle at which the needle142is oriented (in the yz plane) with respect to the vein704(e.g. in degrees). Thus, the guidance information provided by the first view900displayed to the medical practitioner (at618) may advantageously inform the medical procedure of whether the needle142(or other medical instrument) is properly aligned with the target tissue for performance of the medical procedure.

With continued reference toFIG. 6, the process600further includes determining whether an orientation adjustment of the medical instrument is needed at620. For example, the medical practitioner may assess the information shown in the first view900(FIG. 9) and decide that an adjustment is needed in one or more of the roll, align, or pitch orientations of the needle142.

If it is determined that an orientation adjustment is needed (at620), then the process600proceeds to adjusting a position of the medical instrument to improve alignment with the target tissue at622. For example, based on the first view900shown inFIG. 9, the medical practitioner may decide to adjust the alignment of the needle142(based on the top view906), but may choose not to adjust the roll or pitch orientations of the needle142. Alternately, the adjusting (at622) could include translation to fix roll, e.g., if the vessel is off to one side (on view904) but “crosses” in front of the needle according to view906, the practitioner may adjust (at622) by advancing the needle142until it is above the vessel704, then yaw to align, then pitch down. The process600then returns to scanning of the body portion (at614), and the operations614through620are then repeated.

FIG. 10shows a second view100displayed by the display device118of the control system110during the medical procedure in accordance with an embodiment of the present disclosure. Since the scanning (at614), analyzing (at616), and displaying (at618) operations may continue to be continuously performed during the orientation adjustment operation (at622), the second view100of the display device118may advantageously show the adjustments of the needle142as they are being made by the medical practitioner. Thus, in the second view100, the top view906shows that the needle142has been brought into proper alignment (in the the yz plane) with respect to the vein704

Once it is determined that no orientation adjustment is needed (at620, then the process600proceeds to incrementally advancing the medical instrument toward a desired position with respect to the target tissue at624. More specifically, the medical practitioner may slowly advance the needle142a relatively short distance (e.g. a millimeter) toward the vein704.

As further shown inFIG. 6, the process600may then determine whether a desired final position of the medical instrument has been achieved at626. For example, in at least some implementations, the medical practitioner decides whether the needle142has been sufficiently inserted into the vein704to perform the medical procedure (e.g. intravenous administration of medication). If it is determined that the desired final position of the medical instrument has not been achieved (at626), then the process600then returns to scanning of the body portion (at614), and the operations614through620are then repeated. In this way, the process600continuously performs scanning operations (at614), analyzing imaging data (at616), displaying guidance information (at618), determining whether orientation adjustments are needed (at620), performing orientation adjustments (at622), and incrementally advancing the medical instrument (at626), until the desired final position of the medical instrument is achieved (at626).

As the medical instrument is being successively advanced (at624) toward the target tissue, there may be a point at which contact with the target tissue is made. For example,FIG. 11shows the needle142of the handheld component140positioned in a second position1100such that the bevel506(and bevel tip504) have started entering the vein704of the body portion150of the patient in accordance with an embodiment of the present disclosure. In at least some implementations, when the needle142makes contact with the vein704, the control system110may retract the tip138of the second optical fiber132into the needle142so that the tip138does not extend beyond the bevel506(which may interfere with the bevel506entering the vein). With the tip138retracted into the needle142, imaging operations may be temporarily suspended until the bevel506of the needle142is fully disposed within the vein704. After a brief period, the tip138may then reextend beyond the bevel506and imaging operations may re-commence to confirm that penetration of the vein704is complete.

In at least some implementations, the guidance information displayed by the display device118of the control system110may change based on whether the medical instrument had made contact with the target tissue. For example, as a result of the needle142making contact with the vein704, the guidance information displayed by the display device118of the control system110may be adjusted (or augmented).FIG. 12shows a third view1200displayed by the display device118of the control system110during the medical procedure in accordance with an embodiment of the present disclosure. In this implementation, the third view130shows a circle1202representing a view along a longitudinal axis of the cylindrical vein704(or other target tissue), and a displayed needle bevel1204representing the location of the bevel506of the needle142relative to the vein704. The guidance information provided by the third view1200may inform the medical practitioner of the degree of insertion of the needle142into the target vein704(represented by circle1202) and assist in the decision whether the needle142has reached the desired position for performing the medical procedure.

In addition,FIG. 13shows the needle142of the handheld component140positioned in a third position1300such that the bevel506(and bevel tip504) have fully entered the vein704of the body portion150of the patient. Similarly,FIG. 14shows a fourth view1400displayed by the display device118of the control system110during the medical procedure. In this implementation, the fourth view1400shows the displayed needle bevel1204fully located within the circle1202representing the vein704(or other target tissue). It will be appreciated that the displayed needle bevel1204may change color (e.g. from red to green) once the needle bevel1204is fully within the target vein704, thereby providing an additional visual indication to the medical practitioner that the needle142has reached the desired position to perform the medical procedure. In addition, as shown inFIG. 14, a buffer region1206may be displayed (e.g. indicated by cross hatching, color, highlighting, etc.) within the interior perimeter of the circle1202representing the vein704to assist the medical practitioner in properly guiding the needle bevel1204to reduce or prevent unintentional contact with the inner surfaces of the vein704during the medical procedure.

FIG. 15shows a fifth view1500that may be displayed by the display device118of the control system110during the medical procedure. In this implementation, the fifth view1500shows the displayed needle bevel1204fully located within the circle1202representing the vein704(as described above and shown inFIG. 14). The fifth view1500also includes an actual OCT image1502that is being acquired by the imaging system120during the medical procedure, showing an intravenous (IV) catheter1504inserted into the vein704. Other features visible in the OCT image1502include a vessel wall1506and an interior lumen1508of the vein704. Also, the buffer region1206may be displayed (e.g. indicated by cross hatching, color, highlighting, etc.) within the interior perimeter of the vessel wall1506to assist the medical practitioner in properly guiding the medical instrument (i.e. catheter1504) to reduce or prevent unintentional contact with the vessel wall1506during the medical procedure. Finally, the fifth view1500also includes a displayed catheter1506(at lower left) disposed within the vein704.

Referring again toFIG. 6, upon determining that the medical instrument has reached the desired final position for performing the medical procedure (at626), the process600proceeds to performing the medical procedure with the medical instrument at the desired position at628. For example, the performing of the medical procedure (at628) may include intravenous administration of a medication via the needle142into the vein704. In at least some implementations, the control system110may signal the stage assemble130to withdraw the tip138of the second optical fiber132into a retracted position within the needle142during (or prior to) the performing of the medical procedure. After the medical procedure is performed (at628), the process600ends or continues to other operations at630.

Techniques and technologies in accordance with the present disclosure may advantageously provide guidance for medical practitioners for guiding medical instruments during medical procedures using real-time imaging. By employing technologies in accordance with the present disclosure, such guidance information may improve the performance of medical procedures by enabling such procedures to be performed more accurately and with less repetition in comparison with prior art techniques.

The preceding discussion has described various implementations of systems and processes in accordance with the present disclosure. It should be appreciated, however, that in alternate implementations, techniques and technologies in accordance with the present disclosure may involve additional details, operations, or activities than those discussed above. Therefore, the following discussion is intended to provide additional descriptive subject matter that may be employed in various further implementations in accordance with the present disclosure.

As noted above, in at least some implementations, an optical coherence tomography (OCT) probe may be used to provide real-time visual interactive guidance of a medical instrument (such as a needle) toward a target tissue (such as a blood vessel). In some implementations, real-time translation of discrete distance measurements from the OCT probe to the blood vessel, at specific inclinations to the needle axis, may be converted into quantitative information concerning the position, orientation, and size of the blood vessel, so as to provide real-time visual guidance to the user. For example, an OCT probe may be configured to emit a sequence of light pulses along a conical surface with a beam angle φ=60° relative to the needle axis and at equidistant azimuthal spacing δθ=0.5° about the axis, which may yield accurate distance measurements to points on the blood vessel. Several scans may be made, at successive extensions δz of the probe from the needle tip.

In at least some implementations, during analysis of imaging data to determine a cylindrical shape of the target tissue (at operation616ofFIG. 6), the blood vessel (or at least a local portion thereof) is modeled as a cylindrical surface, and since discrete point data determined by the OCT probe are of finite accuracy, a suitable fitting routine, such as a least-squares approach, may be applied to the point data to identify the cylinder and to suppress possible influence of measurement noise. A cylinder may be identified by its radius, its axis, and a point on the axis. The implicit equation f (x, y, z)=0 expressed in terms of these intuitive parameters, however, has a non-linear dependence on these parameters. The use of an iterative solution procedure may in some cases be incompatible with real-time computation, or may fail to converge when suitable starting approximations cannot be determined a priori.

In at least some implementations, an approach may avoid such problems by performing a least-squares fit of the data points to a general quadric surface, resulting in a linear system of equations for the unknown coefficients. These coefficients may be regarded as the elements of a symmetric 4 by 4 matrix, and an analysis of the eigenvalues and eigenvectors of the symmetric matrix allows a “best” cylinder fit to be identified in a relatively efficient and reliable manner. Additional details of various techniques for fitting quadric surfaces to data points determined during scanning operations is provided below, however, it may be noted that in alternate implementations, quadric fitting is not used to determine the shape of the target tissue.

In the preceeding discussion, the imaging system120shown inFIG. 2was described as an OCT-based imaging system. In at least some implementations, a broad-spectrum light source in the near infrared or infrared band is used to optimize depth of penetration into the tissues of the patient, with the light being transmitted from the end of a fiber optic line. Although a large amount of the light is lost by absorption or scattering, a fraction of the emitted light (e.g. 10−6to 10−9) may be scattered by a tissue feature, and returns back along the fiber to an interferometer that uses coherent detection (constructive/destructive interference of transmitted and returned signals) to obtain image resolution <10 μm over depths of 1-2 mm.

Because the round-trip time-of-flight of the light may be too short to measure accurately, the data are transformed into the distance or the frequency domain. An early OCT implementation, known as Time Domain (TD) OCT, was based on interference of signals from a sample and a reference arm mirror. The need for rapid, accurate, and repeatable mirror movement may undesirably limit the resolution achievable through such a TD OCT. Accordingly, a more recent Fourier Domain (FD) technology known as a Swept Source (SS) OCT may be employed to achieve substantial improvements in signal acquisition rates and signal-to-noise ratios.

In at least some implementations, an SS OCT may utilize a chirped (i.e. rapid wavelength swept) laser light source and Fast Fourier Transform (FFT) analysis to transform the data from amplitude vs. frequency to intensity vs. depth. Alternately, Spectral Domain (SD) OCT (which is another FD OCT variant) may provide substantial improvements in both sampling rates and signal-to-noise ratio over TD OCT.

It should be appreciated that, regardless of method, the OCT system may provide a one-dimensional array of tissue reflectivity as a function of incremental depth. As noted above, such an array may be referred to as an “A-line.” Multiple A-lines can be aggregated as a “B-scan” defining a raster scan in either Cartesian (x, y) or polar (r, θ) coordinates. In addition, in some implementations, A-lines may also be assembled left-to-right as a function of time, yielding a “waterfall” diagram representing reflectivity along a particular vector (light vector508ofFIG. 5) in the tissue as a function of depth and time. The waterfall format may be useful in studying temporal variations. In the implementation described above, the OCT probe (tip138) is rotated as a function of time, and angle data is reconstructed from time stamps. The B-scan indices may then be interpreted as polar coordinates to create a “radar” plot.

Various known signal processing methods can be applied to the A-lines or B-scans to generate images of the tissues, or to extract information useful for diagnostic or procedural purposes. For guiding a needle during a medical procedure, for example, the goal is to identify the instantaneous position and orientation of a blood vessel (or other target tissue) relative to the needle tip. In at least some implementations, this may be accomplished by surface reconstruction in B-Scan space. Real-time collection and interpretation of OCT data for navigation and therapeutic purposes, and including methods for steering the needle to the blood vessel. It should be appreciated that contemporary OCT is most frequently used in a post-processing workflow such that the imaging data is collected and then later analyzed off-line for presentation in a non-real-time manner in a diagnostic context.

Importantly, although one or more algorithms for identifying a blood vessel are described herein based on OCT, such algorithms are not necessarily restricted to implementations with OCT-based imaging systems. Any suitable imaging modalities that can reconstruct a list of surface detection events may benefit from the one or more algorithms disclosed herein (assuming adequate resolution).

Additional description of techniques for analyzing imaging data to identify a target tissue (such a blood vessel) may further include a discussion of general quadric surfaces. The data generated by the OCT probe correspond to a discrete sampling of points on an intersection curve of an indeterminate cylinder (the blood vessel) with a known cone of sampling light. In at least some implementations, the problem is to determine the position, orientation, and radius of the cylinder from these data points. Cones and cylinders are special instances of a family of algebraic surfaces of degree 2, commonly known as the quadric surfaces. The characterization of quadric surfaces is a well-known topic in algebraic geometry. The implicit equation of a general quadric may be specified in terms of a symmetric 4×4 matrix through the expression

Expanding the matrix product gives the following Equation (1):

The eigenvectors of the upper-left 3×3 sub-matrix

determine the principal axes of the quadric surface. The eigenvalues are the roots ξ of the characteristic equation

with coefficients

Since the matrix (2) is symmetric, its eigenvalues are all real. The quantities β, γ, δ—together with the determinant

of the 4×4 matrix—are invariants of the quadric surface, which is to say they remain unchanged under a motion (translation/rotation) of the surface.

Hereinafter, the terms “cylinder” and “cone” will be understood as referring to right circular cylinders and cones, whose sections by any plane orthogonal to their axes is a circle. The cones and cylinders are ruled quadric surfaces, generated by a one-parameter family of lines. For a cone, these lines pass through a fixed point (the vertex) (or the tip138described above), and maintain a constant angle with a fixed line (the axis). For a cylinder, the lines are parallel to and equidistant from a fixed line (the axis). A cylinder may be regarded as a special instance of a cone, with a point at infinity as the vertex, and we refer to the set of all cones and cylinders as generalized cones. The generalized cones are singular quadrics, distinguished by the condition Δ=0. In terms of the other invariants, a cone is identified by the condition δ≠0, and a cylinder is identified by δ=0, γ≠0. These conditions identify all (not just right circular) cones and cylinders.

With δ=0≠γ equation (3) reduces, on factoring out the root ξ=0, to

and a right circular cylinder is identified by the condition, β2−4 γ=0, that this quadratic equation should have a double root—namely, ξ=½ β.

A cylinder of general position and orientation may be specified by its radius r, a point p*=(x*, y*, z*) on its axis, and a unit vector a=(λ, μ, ν) satisfying

that defines the axis orientation. The implicit equation of the cylinder may be written explicitly in terms of these geometrical parameters as described below. Specifically, the position of a general point p=(x, y, z) relative to p*can be resolved into components parallel and perpendicular to the axis a as

The equation of the cylinder is then determined from the condition that the perpendicular distance of p from the axis is r, and this reduces to

Equation (7) may be re-expressed in terms of the coordinates of p, and making use of Equation (6), we obtain the implicit equation

Note that this equation is invariant upon replacing (x*, y*, z*) by (x*, y*, z*)+α (λ, μ, ν) for any α—i.e., it does not depend on the choice of the point p*on the cylinder axis. In the present context, we may assume that z*=0 (this is valid if ν≠0, i.e., the cylinder axis is not parallel to the (x, y) plane).

The form (8) corresponds to coefficients in the general quadric equation specified by

where it is understood that the constraint (6) also holds.

In principle, a quadric surface can be uniquely determined from 9 points lying in “general position” on it, since equation (1) depends on 10 coefficients, and the surface is unchanged upon dividing (1) by any non-zero coefficient. However, since the 9 points must be exactly specified, and verifying that they are in “general position” is non-trivial, this approach is impractical.

In at least some implementations, given N data points pi=(xi, yi, zi), i=1, . . . , N on the intersection of a known cone and a cylinder, we wish to determine the cylinder. Since the data will be subject to measurement noise, a least-squares fitting scheme is desirable to suppress the influence of the noise. The least-squares fit may be based on either the general quadric surface equation (1), or the equation (8) expressed in terms of the cylinder geometrical parameters.

Equation (8) explicitly determines a cylinder in terms of the geometrical parameters p*, a, r. However, the dependence upon these parameters is not linear, and the least-squares fit will incur a constrained system of non-linear equations. A computationally-intensive iterative method is required to solve this system, and without a reliable scheme for choosing “good” starting values it will not be sufficiently robust for real-time implementation.

Equation (1), on the other hand, is linear in the coefficients a, b, c, . . . and the least-squares fit incurs a system of linear equations for these unknowns, that has a unique solution (if the matrix defined by equations (13)-(15) below is non-singular). Since the general quadric equation (1) does not explicitly determine the least-squares fit surface as a cylinder, the geometry parameters p*, a, r of the “nearest” true cylinder must be extracted from the computed coefficients a, b, c, . . . , as described in Section 6.

In view of the above considerations, equation (1) will be employed in the least-squares surface fit. As observed above, the OCT scan identifies points on the intersection curve of a known cone with the unknown cylinder. This amounts to a one-dimensional sampling of a two-dimensional surface that is, in general, insufficient to uniquely identify the surface. Two or more scans, at different extensions δz of the probe along the needle axis, are required.

This may be seen as follows. The intersection of two quadric surfaces q0(x, y, z)=0 and q1(x, y, z)=0 is, in general, an irreducible quartic space curve, which is to say it may degenerate into a collection of simpler curves (lines, conics, and cubics) whose degrees sum to 4. There are infinitely many pairs of quadric surfaces that possess the same intersection curve C as q0(x, y, z)=0 and q1(x, y, z)=0. Any two members of the pencil of quadrics defined by

corresponding to distinct τ values possess the same intersection curve C as q0(x, y, z)=0 and q1(x, y, z)=0. Thus, given one of two quadrics, it is not possible to uniquely identify the other from their intersection curve.

In the present context, one quadric is a known cone, and we can exploit the additional information that the unknown quadric is a cylinder. Suppose Q0and Q1are symmetric 4×4 matrices with elements a0, b0, . . . and a1, b1, . . . , specifying two quadric surfaces. Then the determinantal equation

is of degree 4, and its (real) roots identify the generalized cones of the pencil defined by Q0 and Q1. The quartic polynomial p(τ) is called the discriminant of the pencil of quadrics. In the generic case, in which the roots of p(τ) are distinct, the intersection C is a non-singular quartic space curve.

To verify that a cylinder Q1constructed from a known intersection curve C with a known cone Q0is unique, we must determine the real roots of the discriminant p(τ) of the pencil defined by Q0and Q1, and check that none of the quadrics corresponding to these roots (other than τ=1) is a cylinder. One known method (known as Ferrari's method) provides a closed-form solution for all the roots of p(τ). This uniqueness test can only be performed a posteriori, i.e., after Q1 has been constructed. However, using multiple scans at successive extensions δz of the OCT probe eliminates the need to perform this test.

Equation (1) may be divided by any non-zero coefficient without influencing the quadric surface it defines. In the present context, we may divide through by d, which corresponds to the choice d=1 in (1). This is permissible if the surface q(x, y, z)=0 does not pass through the origin, which is true since the origin is defined to be the apex of the cone (i.e., the position of the sensor) and the sensor does not encroach on the cylinder.

In at least some implementations, a coordinate system is adopted in which the needle axis is identified with the z-axis, and for zero extension the OCT probe is located at z=0. The known parameters and available data are the cone beam angle φ (deflection angle φ of the light vector508) about the z-axis, the measured distances ρifrom the probe to the blood vessel surface, and the associated azimuthal angles θion the cone and probe extensions δzifor each measured point, i=1, . . . , N. For the least-squares fit, the data are converted to Cartesian coordinates according to

With d=1, the remaining unknown 9 coefficients a, b, c, f, g, h, l, m, n in (1) are determined by minimizing the expression

Setting the partial derivatives of E with respect to these coefficients equal to zero results in a linear system of equations of the form

where v=[a b c f g h l m n]Tand, on introducing the basis functions

the elements of the matrix M and right-hand side vector r can be expressed in terms of the data points (xi, yi, zi) as

The linear system (13) has a unique solution when M is non-singular, which can be efficiently computed by Gaussian elimination.

Techniques for determining the cylinder geometry parameters will now be described. Once the vales a, b, c, f, g, h, l, m, n have been computed, we must obtain the cylinder geometrical parameters p*, a, r from them. The principal axes of the quadric surface are identified by the eigenvectors (vx, vy, vz) of the 3×3 matrix (2)—i.e., by the solutions of the equation

where the eigenvalues ξ are the roots of the characteristic equation (3) with the coefficients (4)-(5). As noted above, for an exact right circular cylinder ξ=0 is one eigenvalue (with no valid associated eigenvector), and ξ=2 β is a double eigenvalue, with which we may associate two linearly-independent eigenvectors. The latter eigenvectors span a diametral plane of the cylinder, orthogonal to its axis. Hence, the three row vectors of the 3×3 matrix in (17) must be parallel (or anti-parallel) to the cylinder axis.

If the coefficients a, b, c, f, g, h are determined from a least-squares fit to noisy data, they will not exactly define a right circular cylinder, and the row vectors of the 3×3 matrix in (17) will not be precisely parallel or antiparallel. To estimate the cylinder axis, we form the three unit vectors

taking u1as a reference, we reverse u2if u1·u2<0 and u3if u1·u3<0. The cylinder axis a is then estimated as the centroid of these unit vectors, namely

Consider next the determination of the point p*=(x*, y*, z*) on the axis. As previously noted, we may assume that z*=0 if the cylinder axis is not parallel to the (x, y) plane. With d=1, the restriction of (1) to the plane z=0 identifies a conic curve specified by the equation

Provided that ab−f2≠0, this defines a central conic, and its center identifies the intersection of the cylinder axis with the (x, y) plane. The center can be determined by identifying the shift (x, y) (x+x*, y+y*) of the origin that will eliminate the terms of (19) linear in x and y. One can easily verify that

The final parameter to be determined is the cylinder radius r. Knowing the cylinder axis a and a point p* on it, a robust approach is to compute r as the root-mean-square distance of the N data points pi=(xi, yi, zi) from the cylinder axis. Thus, based on equation (7), the radius is estimated as

For a quadric surface defined by equation (1) that is a true right circular cylinder, and exact data points p1, . . . , pN, the above procedure can precisely identify its geometry parameters. First, with the eigenvalue ξ=½ (a+b+c), the rows of the of the 3×3 matrix in (17) will be precisely linearly dependent, and unitizing any of them will exactly determine the axis vector a. Moreover, the point p*=(x*, y*, z*) on the axis with z*=0 is precisely identified by (20). Finally, any exact point pion the cylinder will suffice to determine the radius as r=|(pi−p*)×a|.

Solution reliability of the foregoing technologies and algorithms will now be discussed. For the vector norm

the subordinate norm of the 9×9 matrix M in (13) may be specified as

and the p-norm condition number Cp(M) of M is defined by

If a perturbation δr is imposed on the right-hand-side vector r in (13), that incurs a corresponding perturbation δv in the solution vector v, the relative errors

satisfy

The bound (22) is sharp, i.e., it holds with equality for some perturbation δr. In the cases p=1 and ∞, ∥M∥pis the greatest of the column and row sums of absolute values of the matrix elements, respectively. Since M and M−1are symmetric, ∥M∥1=∥M∥∞, ∥M−1∥1=∥M−1∥∞, so C1(M)=C∞(M), and we may simply write C(M). The condition number gives a (worst-case) indication of the influence of round-off error amplification when the system (13) is solved using floating-point arithmetic.

In the present context, a different source of inaccuracy may be dominant when solving (13). Namely, the elements (15) and (16) of both the matrix M and right-hand side vector r are not known exactly, since they are computed from the basis functions (14) evaluated at the data points (xi, yi, zi), whose precision is limited by the accuracy of the OCT distance measurements ρi.

To assess the influence of the finite accuracy of the distances ρi, they are assumed to have Gaussian (normal) distributions [14] of the form

where it is assumed that the nominal distance measurements are reasonable estimates of their individual meansρi, and the same standard deviation σ=0.0005 mm holds for each measurement—this corresponds to ˜68% of the measured distances ρibeing within ±0.0005 mm ofρi. In at least some implementations, a Monte Carlo experiment may be performed in which each individual ρiis randomly perturbed to a new value {tilde over (ρ)}iin accordance with the probability distribution (23). New point coordinates ({tilde over (x)}i, {tilde over (y)}i, {tilde over (z)}i) are then computed from the {tilde over (ρ)}ivalues using (12), and the corresponding matrix elements {tilde over (M)}jkand right-hand-side values {tilde over (r)}jare obtained from (15) and (16). Solving the resulting linear system {tilde over (M)}{tilde over (v)}={tilde over (r)}, for the resulting perturbed coefficients {tilde over (v)}=[ã {tilde over (b)} {tilde over (c)} {tilde over (f)} {tilde over (g)} {tilde over (h)} {tilde over (l)} {tilde over (m)} ñ]T, we define their relative error as

The Monte Carlo experiment may be repeated several times, with different random samplings of the distributions (23), to assess the overall consistency and range of variation in the ϵvvalues obtained. Examples described below confirm that this approach offers a favorable assessment of the accuracy of the computed quadric surface coefficients.

Three examples will now be described that demonstrate the effectiveness of implementations of the above-described techniques and technologies in accordance with the present disclosure. More specifically, the following examples describe results obtained from an implementations of the methodology in the C programming language on representative test data sets (all dimensions are in mm). In the conversion (12) of the “raw” OCT probe data to Cartesian coordinates, the cone beam angle (deflection angle of light vector508ofFIG. 5) is φ=60° and the scans are made at azimuthal angle increments δθ=0.5° for each fixed probe extension δz.

In a first representative example in accordance with the present disclosure, the cylinder has radius r=0.75, and the axis is specified by the point p*=(x*, y*, z*)=(1.0, 4.0, 0.0) and the unit vector a=(λ, μ, ν)=(−0.17364818, −0.33682409, 0.92541658). Scans are made at three successive extensions δz, the distances ρ to the cylinder being detected at the angular increment δθ beginning at θ0, for a total of n points per scan as follows:δz=0.0, θ0=−2.0°, n=52;δz=1.0, θ0=−5.0°, n=57;δz=2.0, θ0=−9.0°, n=65.

The total number of points is N=174. Table 1 compares the exact cylinder coefficients, computed from (9)-(11) and divided by d, with the least-squares fit values. From (18) we obtain a=(−0.17503840, −0.33666708, 0.92521178) as the estimated cylinder axis, which makes an angle 0.081015° with the exact axis (−0.17364818, −0.33682409, 0.92541658). The axis point p*, determined from (20) has coordinates (x*, y*)=(1.00064338, 4.00260039), as compared to the exact point (1.0, 4.0). Finally, the cylinder radius computed from (21) is r=0.746531, whereas the exact value is r=0.750000. From the computed coefficients we have values γ=0.00499410, δ=0.00000022 of the invariants (4), in relatively good agreement with the conditions γ=0=δ identifying a cylinder.FIG. 16shows a first computed cylinder1600based on a first scanning pattern1602in accordance with the first example simulation described above.

TABLE 1Comparison of exact and least-squaresfit coefficients for Example 1.exactleast-squaresa0.068665440.06847202b0.062768000.06266601c0.010167220.01015567f−0.00414103−0.00413862g0.022068650.02197726h0.011377390.01133276l−0.05210131−0.05195083m−0.24693097−0.24668571n−0.09965198−0.09946885d1.000000001.00000000

The condition number of the matrix M in this example is C(M)=1.81×106. The Monte Carlo accuracy assessment (described in Section 7) was run 100 times with different random numbers satisfying the Gaussian distribution (23), resulting in values of the fractional error ϵvin the computed coefficients ranging between 0.000096 and 0.001095, with a mean value 0.000508.

Overall, the least-squares fitting procedure and the parameter estimation scheme discussed above provide a remarkably accurate estimation of the cylinder geometry, despite the relatively low precision of the measurement data. To demonstrate that the accuracy of the data is the only factor limiting the precision with which the cylinder can be identified, the computation was repeated with ρ values computed in double-precision arithmetic, in lieu of the values with 3 decimal place accuracy used above. This resulted in an angular deviation between the estimated and exact axes of only 0.0000008538°, and (x*, y*)=(1.000000000029, 4.000000000119), r=0.749999999795 for the coordinates of the axis point p*and the cylinder radius r.

In a second representative example in accordance with the present disclosure, the cylinder geometry parameters were set to (x*, y*)=(1.0, 4.0), a=(0.64278761, 0.26200263, 0.71984631), and r=1.5. Three scans were made, corresponding to the valuesδz=0.0, θ0=−15.5°, n=106;δz=1.0, θ0=−20.5°, n=119;δz=2.0, θ0=−26.5°, n=134.

The total number of points is N=359. Table 2 compares the exact cylinder coefficients, computed from (9)-(11) and divided by d, with the least-squares fit values. From (18) we obtain a=(−0.18374332, −0.32542690, 0.92754284) as the estimated cylinder axis, which makes an angle 0.880816° with the exact axis (−0.17364818, −0.33682409, 0.92541658). The axis point p*, determined from (20) has coordinates (x*, y*)=(0.99717264, 3.98746160), as compared to the exact point (1.0, 4.0). Finally, the cylinder radius computed from (21) is r=1.522544, whereas the exact value is r=1.500000. From the computed coefficients we have values γ=0.00641154, δ=0.00000007 of the invariants (4), as compared to the exact conditions γ≠0=δ defining a cylinder.FIG. 17shows a second computed cylinder1700based on a second scanning pattern1702in accordance with the first example simulation described above.

The condition number of the least-squares matrix in this case is C(M)=1.65×105. The Monte Carlo accuracy assessment was run 100 times with different random numbers satisfying the Gaussian distribution (23), yielding values of the fractional error ϵvin the computed coefficients between 0.000068 and 0.000738, with a mean value 0.000303.

When the computation is repeated with double-precision ρ values, in lieu of the values with 3 decimal place accuracy used above, we obtain an angular deviation between the estimated and exact axes of 0.0000000000°, and (x*, y*)=(0.999999999997, 3.999999999988), r=1.500000000018 for the coordinates of the axis point p*and the cylinder radius r.

TABLE 2Comparison of exact and least-squaresfit coefficients for Example 2.exactleast-squaresa0.077982430.07709279b0.071284790.07145285c0.011546780.01150307f−0.00470292−0.00441349g0.025063070.02517422h0.012921160.01287786l−0.05917077−0.05927620m−0.28043625−0.28051450n−0.11317344−0.11327718d1.000000001.00000000

In a third representative example in accordance with the present disclosure, the cylinder geometry parameter are (x*, y*)=(1.0, 4.0), a=(0.64278761, 0.26200263, 0.71984631), and r=0.5. Three scans were made, corresponding to the valuesδz=0.0, θ0=−24.5°, n=48;δz=1.0, θ0=−42.0°, n=53;δz=2.0, θ0=−59.0°, n=52.

The total number of points is N=153. Table 3 compares the exact cylinder coefficients, computed from (9)-(11) and divided by d, with the least-squares fit values. From (18) we obtain a=(−0.64386222, −0.25900228, 0.71997171) as the estimated cylinder axis, which makes an angle 0.182742° with the exact axis (−0.64278761, −0.26200263, 0.71984631). The axis point p*, determined from (20) has coordinates (x*, y*)=(1.00228517, 4.00163039), as compared to the exact point (1.0, 4.0). Finally, the cylinder radius computed from (21) is r=0.507851, whereas the exact value is r=0.500000. From the computed coefficients we have values γ=0.00514512, δ=0.00000002 of the invariants (4), in fair agreement with the conditions γ=0=6 characterizing a cylinder.FIG. 18shows a third computed cylinder1800based on a third scanning pattern1802in accordance with the first example simulation described above.

TABLE 3Comparison of exact and least-squaresfit coefficients for Example 3.exactleast-squaresa0.042244300.04195657b0.067046370.06700938c0.034685360.03449726f−0.01212365−0.01213370g0.013577060.01356661h0.033309450.03307726l0.006250290.00650214m−0.25606182−0.25598535n−0.08761768−0.08742876d1.000000001.00000000

The condition number of the least-squares matrix M in this example is C(M)=1.20×107. Using 100 runs of the Monte Carlo accuracy assessment with different random numbers that satisfy the Gaussian distribution (23), values of the fractional error Ev in the computed coefficients between 0.000110 and 0.001457 were obtained, with a mean value 0.000557. As in the preceding examples, essentially exact cylinder geometry parameters were obtained when the computation was repeated with double-precision ρ values.

The suitability of the techniques and technologies described herein for real-time implementation will now be described. In at least some implementations, using a modest 1.1 GHz processor, the execution times for identification of the cylinder from the point coordinate data in the three examples described above were 0.27 ms, 405 ms, and 0.24 ms, respectively. Since these examples used N=174, 359, and 153 points, these execution times are consistent with a linear dependence on N, and constitute only a modest fraction of the overall effort required for real-time implementation.

In at least some implementations, the OCT probe tip (tip138) may emit light pulses of 40 μs duration every 50 μs, inclined at 60° to the probe axis (axis144ofFIG. 5). Within the viewing range, reflection intensity data may be acquired along each pulse, up to a few mm from the probe tip. The probe may rotate along its axis at a 10 Hz rate, and its tip may execute a reciprocating motion along the probe axis at a speed 10 mm/s. These motions result in a helical scanning pattern on the target surface.

In at least some implementations, tor a signal of width 30° the probe may require just under 10 ms to trace a scan curve, with sequential scans at 100 ms apart. Further computations may be needed to convert the raw OCT data into point coordinates, and a target computation time of 100-200 ms per image frame is anticipated. A “rolling” solution to frame updating may also be used, in which overlapping sequences of scans are used to provide a higher image refresh frequency.

Accordingly, techniques and technologies in accordance with the present disclosure may advantageously perform real-time identification of the position, orientation, and size of blood vessels or other desirable target tissues, based on discrete distance measurements from an imaging apparatus. In at least some implementations, the techniques and technologies disclosed herein are sufficiently fast and robust to provide real-time guidance to medical practitioners during medical procedures (e.g. providing needle guidance for venipuncture procedures) through a visual display.

Moreover, modelling a blood vessel (or other target tissues) as a right circular cylinder, techniques and technologies in accordance with the present disclosure may first perform a least-squares fit to the imaging data (e.g. OCT data), in terms of a general quadric surface represented by a symmetric 4×4 matrix. Analysis of the structure of this matrix then allows the right circular cylinder “closest” to the general quadric to be identified. This avoids the need for iterative non-linear surface fitting, which can be computationally demanding, and lacks robustness when identification of a good starting approximation is not available.

Examples described above show that the cylinder identification procedure in accordance with the present disclosure is fast, with a computing time that grows only linearly with the total number N of data points, and the cylinder geometry parameters may be identified with a high degree of robustness. The techniques and technologies in accordance with the present disclosure may therefore be readily adaptable to identification of other simple morphologies, such as general quadrics or toroidal surfaces. Accordingly, techniques and technologies in accordance with the present disclosure may offer significant advantages to medical practitioners for guiding medical instruments during medical procedures using real-time imaging technologies.

In some implementations, one or more aspects of the above-described processes for guiding medical instruments during medical procedures using real-time imaging technologies may be at least partially implemented using a computing device (e.g. the control system110, etc.). For example,FIG. 19is a schematic view of an exemplary computing device1900configured to operate in accordance with implementations of the present disclosure. As described below, the computing device1900can be configured to perform one or more of the functions and operations associated with one or more of the techniques and technologies disclosed herein.

As shown inFIG. 19, in some implementations, the computing device1900may include one or more processors (or processing units)1902, special purpose circuitry1982, a memory1904, and a bus1906that couples various system components, including the memory1904, to the one or more processors1902and special purpose circuitry1982. The bus1906represents one or more of any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures. In this implementation, the memory1904includes read only memory (ROM)1908and random access memory (RAM)1910. A basic input/output system (BIOS)1912, containing the basic routines that help to transfer information between elements within the computing device1900, such as during start-up, is stored in ROM1908.

The exemplary computing device1900further includes a hard disk drive1914for reading from and writing to a hard disk (not shown), and is connected to the bus1906via a hard disk drive interface1916(e.g., a SCSI, ATA, or other type of interface). A magnetic disk drive1918for reading from and writing to a removable magnetic disk1920, is connected to the system bus1906via a magnetic disk drive interface1922. Similarly, an optical disk drive1924for reading from or writing to a removable optical disk1926such as a CD ROM, DVD, or other optical media, connected to the bus1906via an optical drive interface1928. The drives and their associated computer-readable media provide nonvolatile storage of computer readable instructions, data structures, program modules and other data for the computing device1900. Although the exemplary computing device1900described herein employs a hard disk, a removable magnetic disk1920and a removable optical disk1926, it should be appreciated by those skilled in the art that other types of computer readable media which can store data that is accessible by a computer, such as magnetic cassettes, flash memory cards, digital video disks, random access memories (RAMs) read only memories (ROM), and the like, may also be used.

As further shown inFIG. 19, a number of program modules may be stored on the memory1904(e.g. the ROM1908or the RAM1910) including an operating system1930, one or more application programs1932, other program modules1934, and program data1936. Alternately, these program modules may be stored on other computer-readable media, including the hard disk, the magnetic disk1920, or the optical disk1926. For purposes of illustration, programs and other executable program components, such as the operating system1930, are illustrated inFIG. 19as discrete blocks, although it is recognized that such programs and components reside at various times in different storage components of the computing device1900, and may be executed by the processor(s)1902or the special purpose circuitry1982of the computing device1900.

A user may enter commands and information into the computing device1900through input devices such as a keyboard1938and a pointing device1940. Other input devices (not shown) may include a microphone, joystick, game pad, satellite dish, scanner, or the like. These and other input devices are connected to the processing unit1902and special purpose circuitry1982through an interface1942that is coupled to the system bus1906. A monitor1944or other type of display device is also connected to the bus1906via an interface, such as a video adapter1946. In addition to the monitor, the computing device1900may also include other peripheral output devices (not shown) such as speakers and printers.

The computing device1900may operate in a networked environment using logical connections to one or more remote computers (or servers)1958. Such remote computers (or servers)1958may be a personal computer, a server, a router, a network PC, a peer device or other common network node, (or the automated microscopy assembly110ofFIG. 1) and may include many or all of the elements described above relative to computing device1900. The logical connections depicted inFIG. 19may include one or more of a local area network (LAN)1948and a wide area network (WAN)1950. Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets, and the Internet. In this embodiment, the computing device1900also includes one or more broadcast tuners1956. The broadcast tuner1956may receive broadcast signals directly (e.g., analog or digital cable transmissions fed directly into the tuner1956) or via a reception device (e.g., via an antenna, a satellite dish, etc.).

When used in a LAN networking environment, the computing device1900may be connected to the local network1948through a network interface (or adapter)1952. When used in a WAN networking environment, the computing device1900typically includes a modem1954or other means for establishing communications over the wide area network1950, such as the Internet. The modem1954, which may be internal or external, may be connected to the bus1906via the serial port interface1942. Similarly, the computing device1900may exchange (send or receive) wireless signals1953with one or more remote computers (or servers)1958, (or with the automated microscopy assembly110ofFIG. 1), using a wireless interface1955coupled to a wireless communicator1957(e.g., an antenna, a satellite dish, a transmitter, a receiver, a transceiver, a photoreceptor, a photodiode, an emitter, a receptor, etc.).

In a networked environment, program modules depicted relative to the computing device1900, or portions thereof, may be stored in the memory1904, or in a remote memory storage device. The program modules may be implemented using software, hardware, firmware, or any suitable combinations thereof. In cooperation with the other components of the computing device1900, such as the processing unit1902or the special purpose circuitry1982, the program modules may be operable to perform one or more implementations or aspects of processes in accordance with the present disclosure.

Generally, application programs and program modules executed on the computing device1900may include routines, programs, objects, components, data structures, etc., for performing any tasks necessary for the successful implementation of the techniques and technologies for guiding medical instruments during medical procedures using real-time imaging technologies in accordance with the present disclosure. These program modules and the like may be executed as native code or may be downloaded and executed, such as in a virtual machine or other just-in-time compilation execution environments. Typically, the functionality of the program modules may be combined or distributed as desired in various implementations.

In view of the disclosure of techniques and technologies for guiding medical instruments during medical procedures using real-time imaging technologies as disclosed herein, a few representative embodiments are summarized below. It should be appreciated that the representative embodiments described herein are not intended to be exhaustive of all possible embodiments, and that additional embodiments may be readily conceived from the disclosure of techniques and technologies provided herein.

For example, in at least some implementations, a method for performing a medical procedure includes engaging a medical instrument with a body portion of a patient, the medical instrument including an elongated portion configured to be inserted into the body portion and having an optical fiber at least partially disposed within the elongated portion, the optical fiber having a tip portion that is extendable beyond a distal end of the elongated portion; actuating an imaging system that provides a sampling energy into the optical fiber, the sampling energy being emitted from the tip portion along a sampling vector at a deflection angle with the longitudinal axis into one or more tissues of the body portion as the elongated portion is inserted into the body portion, the one or more tissues including a target tissue; and actuating a stage assembly to move the tip portion to perform a scanning of the one or more tissues with the sampling energy emitted from the tip portion, the stage assembly rotating at least the tip portion about a scanning axis that is parallel with the longitudinal axis and reciprocating at least the tip portion along the scanning axis that is parallel with the longitudinal axis with the tip portion proximate to and extended beyond the distal end of the elongated portion, the sampling energy being emitted from the tip portion in a scanning pattern. The method further includes receiving a reflected energy that is reflected from the one or more tissues back through the optical fiber to the imaging system, the reflected energy providing a plurality of one-dimensional arrays of intensity values of the reflected energy at a plurality of distances along the sampling vector; analyzing the plurality of one-dimensional arrays of intensity values of the reflected energy to determine a shape of the target tissue and a location of the target tissue relative to the elongated portion of the medical instrument; and displaying information including one or more relative positions of the target tissue relative to the elongated portion of the medical instrument for guiding the medical instrument into engagement with the target tissue as the elongated portion is inserted into the body portion for performance of the medical procedure.

In further implementations, the method further comprises advancing the distal end of the elongated portion toward the target tissue; and wherein the receiving of the reflected energy, the analyzing of the reflected energy, and the displaying of the information for guiding the medical instrument into engagement with the target tissue are continuously performed in approximately real-time during the advancing of the distal end of the elongated portion toward the target tissue.

In at least some implementations, the analyzing the plurality of one-dimensional arrays of intensity values of the reflected energy to determine a shape of a target tissue and a location of the target tissue relative to the elongated portion of the medical instrument comprises approximating a shape of the target tissue as a cylinder, including determining an axis, a radius, and at least one point on the axis of the cylinder. In still other implementations, the analyzing the plurality of one-dimensional arrays of intensity values of the reflected energy to determine a shape of a target tissue and a location of the target tissue relative to the elongated portion of the medical instrument comprises determining a shape of the target tissue as a quadric surface and performing a least-squares fit of the intensity values onto the quadric surface.

Moreover, in at least some implementations, the scanning pattern includes a conical scanning pattern, and wherein analyzing the plurality of one-dimensional arrays of intensity values comprises analyzing the plurality of one-dimensional arrays of intensity values to determine an intersection of a cylindrical target tissue with the conical scanning pattern. In further implementations, the scanning pattern includes a helical scanning pattern, and wherein analyzing the plurality of one-dimensional arrays of intensity values comprises analyzing the plurality of one-dimensional arrays of intensity values to determine an intersection of a cylindrical target tissue with the helical scanning pattern.

In further implementations, the method further comprises, when the distal end of the elongated portion contacts the target tissue, retracting the tip portion of the optical fiber into the distal end and at least temporarily suspending at least the reciprocating of the tip portion along the longitudinal axis until the distal end of the elongated portion penetrates an outer wall of the target tissue.

In at least some implementations, the imaging system comprises an optical coherence tomography system, and wherein the sampling energy comprises a broad-spectrum light including at least one of near infrared or infrared light. Similarly, in at least some implementations, the elongated portion of the medical instrument comprises at least one of a needle or a catheter, and wherein the medical procedure includes a venipuncture or a catheterization. In at least some particular implementations, the scanning axis is collinear with the longitudinal axis of the elongated portion, the deflection angle is sixty degrees, and wherein the stage assembly rotates the tip portion at 0.5 Hz and reciprocates the tip portion along a translation range of 6 mm. Similarly, in at least some particular implementations, displaying information including one or more relative positions of the target tissue relative to the elongated portion of the medical instrument comprises displaying visual image information including one or more of a roll position view, an alignment position view, and a pitch position view.

Furthermore, in at least some implementations, an apparatus for performing a medical procedure, comprising: a medical instrument including an elongated portion configured to be inserted into a body portion of a patient and having an optical fiber at least partially disposed within the elongated portion, the optical fiber having a tip portion that is extendable beyond a distal end of the elongated portion; an imaging system configured to provides a sampling energy into the optical fiber, the sampling energy being emitted from the tip portion along a sampling vector at a deflection angle with the longitudinal axis into one or more tissues of the body portion as the elongated portion is inserted into the body portion; and a stage assembly to actuate the tip portion to perform a scanning of the one or more tissues with the sampling energy emitted from the tip portion, the stage assembly being configured to rotate at least the tip portion about a scanning axis that is parallel with the longitudinal axis and to reciprocate at least the tip portion along the scanning axis that is parallel with the longitudinal axis with the tip portion proximate to and extended beyond the distal end of the elongated portion, the sampling energy being emitted from the tip portion in a scanning pattern. The imaging system may be further configured to receive a reflected energy that is reflected from the one or more tissues back through the optical fiber, the reflected energy providing a plurality of one-dimensional arrays of intensity values of the reflected energy at a plurality of distances along the sampling vector. The apparatus further comprises a control system configured to analyze the plurality of one-dimensional arrays of intensity values of the reflected energy to determine a shape of a target tissue and a location of the target tissue relative to the elongated portion of the medical instrument, and display information including one or more relative positions of the target tissue relative to the elongated portion of the medical instrument for guiding the medical instrument into engagement with the target tissue as the elongated portion is inserted into the body portion for performance of the medical procedure.

In at least some implementations, the imaging system is configured to continuously receive the reflected energy, and the control system is configured to continuously analyze the reflected energy and display the information for guiding the medical instrument into engagement with the target tissue in approximately real-time during advancement of the distal end of the elongated portion toward the target tissue during the medical procedure.

Similarly, in at least some implementations, the control system is configured to analyze the plurality of one-dimensional arrays of intensity values of the reflected energy, including determining an axis, a radius, and at least one point on the axis of a cylindrical shape of the target tissue. In still other implementations, the control system is configured to analyze the plurality of one-dimensional arrays of intensity values of the reflected energy, including determining a shape of the target tissue as a quadric surface and performing a least-squares fit of the intensity values onto the quadric surface. In further implementations, the control system is configured to determine that the distal end of the elongated portion had contacted the target tissue, and to control the stage assembly to retract the tip portion of the optical fiber into the distal end and at least temporarily suspend at least the reciprocating of the tip portion along the longitudinal axis until the distal end of the elongated portion has penetrated an outer wall of the target tissue. And in further implementations, the scanning axis is collinear with the longitudinal axis of the elongated portion, and the imaging system comprises an optical coherence tomography system, and wherein the sampling energy comprises a broad-spectrum light including at least one of near infrared or infrared light.

In addition, in at least some implementations, a system for performing a medical procedure comprises one or more processors, and one or more memory devices operatively coupled to the one or more processors and bearing one or more instructions that, when executed by the one or more processors, perform operations including: actuating an imaging system to provide a sampling energy when a medical instrument is engaged with a body portion of a patient, the medical instrument including an elongated portion configured to be inserted into the body portion and having an optical fiber at least partially disposed within the elongated portion, the optical fiber having a tip portion that is extendable beyond a distal end of the elongated portion, the sampling energy being provided into the optical fiber and emitted from the tip portion along a sampling vector at a deflection angle with the longitudinal axis into one or more tissues of the body portion as the elongated portion is inserted into the body portion; actuating a stage assembly to move the tip portion to perform a scanning of the one or more tissues with the sampling energy emitted from the tip portion, the stage assembly rotating at least the tip portion about a scanning axis that is parallel with the longitudinal axis and reciprocating at least the tip portion along the scanning axis that is parallel with the longitudinal axis with the tip portion proximate to and extended beyond the distal end of the elongated portion, the sampling energy being emitted from the tip portion in a scanning pattern; receiving a reflected energy that is reflected from the one or more tissues back through the optical fiber to the imaging system, the reflected energy providing a plurality of one-dimensional arrays of intensity values of the reflected energy at a plurality of distances along the sampling vector; analyzing the plurality of one-dimensional arrays of intensity values of the reflected energy to determine a shape of a target tissue and a location of the target tissue relative to the elongated portion of the medical instrument; and displaying information including one or more relative positions of the target tissue relative to the elongated portion of the medical instrument for guiding the medical instrument into engagement with the target tissue as the elongated portion is inserted into the body portion for performance of the medical procedure.

In at least some implementations, the operations comprise analyzing the plurality of one-dimensional arrays of intensity values of the reflected energy, including determining an axis, a radius, and at least one point on the axis of a cylindrical shape of the target tissue. And in still other implementations, the operations comprise analyzing the plurality of one-dimensional arrays of intensity values of the reflected energy, including determining a shape of the target tissue as a quadric surface and performing a least-squares fit of the intensity values onto the quadric surface.

In the foregoing description, many specific details of certain implementations are described and shown in the accompanying figures. One skilled in the art will understand that the present disclosure may have other possible implementations, and that such other implementations may be practiced with or without some of the particular details set forth in the foregoing description. In addition, it will be appreciated that although various aspects may be described in a particular order, or with respect to certain figures or certain embodiments, it should be appreciated that such aspects may be variously combined or re-ordered to create alternate implementations that remain consistent with the scope of the present disclosure and the claims set forth below.

It should be appreciated that the particular embodiments of processes described herein are merely particular implementations of the present disclosure, and that the present disclosure is not limited to the particular implementations described herein and shown in the accompanying figures. In addition, in alternate implementations, certain acts need not be performed in the order described, and may be modified or combined, and/or may be omitted entirely, depending on the circumstances. Moreover, in various implementations, the acts described may be implemented by a computer, controller, processor, programmable device, or any other suitable device, and may be based on instructions stored on one or more computer-readable media or otherwise stored or programmed into such devices. In the event that computer-readable media are used, the computer-readable media can be any available media that can be accessed by a device to implement the instructions stored thereon.

Various methods, systems, and techniques have been described herein in the general context of computer-executable instructions, such as program modules, executed by one or more processors or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types. Typically, the functionality of the program modules may be combined or distributed as desired in various alternate embodiments. In addition, embodiments of these methods, systems, and techniques may be stored on or transmitted across some form of computer readable media.

The foregoing examples are meant to be illustrative only, and omission of an example here should not be construed as intentional or intentionally disavowing subject matter. The scope of the invention set forth herein is defined solely by the following claims at the end of this application.

In a general sense, those skilled in the art will recognize that the various aspects described herein which can be implemented, individually and/or collectively, by a wide range of hardware, software, firmware, and/or any combination thereof. Those having skill in the art will recognize that the subject matter described herein may be implemented in an analog or digital fashion or some combination thereof.

Throughout this application, examples and lists are given, and these examples and/or lists may be delineated with parentheses, commas, the abbreviation “e.g.,” or some combination thereof. Unless explicitly otherwise stated, these examples and lists are merely exemplary and are non-exhaustive. In most cases, it would be prohibitive to list every example and every combination. Thus, smaller, illustrative lists and examples are used, with focus on imparting understanding of the claim terms rather than limiting the scope of such terms.

Although one or more users maybe shown and/or described herein, and other places, as a single illustrated figure, those skilled in the art will appreciate that one or more users may be representative of one or more human users, robotic users (e.g., computational entity), and/or substantially any combination thereof (e.g., a user may be assisted by one or more robotic agents) unless context dictates otherwise. Those skilled in the art will appreciate that, in general, the same may be said of “sender” and/or other entity-oriented terms as such terms are used herein unless context dictates otherwise.

While particular aspects of the present subject matter described herein have been shown and described, it will be apparent to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from the subject matter described herein and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of the subject matter described herein. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.).

Throughout this application, the terms “in an embodiment,” “in at least some embodiments,” “in one embodiment,” “in some embodiments,” “in several embodiments,” “in at least one embodiment,” “in various embodiments,” and the like, may be used. Each of these terms, and all such similar terms should be construed as “in at least one embodiment, and possibly but not necessarily all embodiments,” unless explicitly stated otherwise. Specifically, unless explicitly stated otherwise, the intent of phrases like these is to provide non-exclusive and non-limiting examples of implementations of the invention. The mere statement that one, some, or may embodiments include one or more things or have one or more features, does not imply that all embodiments include one or more things or have one or more features, but also does not imply that such embodiments must exist. It is a mere indicator of an example and should not be interpreted otherwise, unless explicitly stated as such.

Throughout this application, the terms “in an implementation,” “in at least some implementations,” “in one implementation,” “in some implementations,” “in several implementations,” “in at least one implementation,” “in various implementations,” and the like, may be used. Each of these terms, and all such similar terms should be construed as “in at least one implementation, and possibly but not necessarily all implementations,” unless explicitly stated otherwise. Specifically, unless explicitly stated otherwise, the intent of phrases like these is to provide non-exclusive and non-limiting examples of implementations of the invention. The mere statement that one, some, or may implementations include one or more things or have one or more features, does not imply that all implementations include one or more things or have one or more features, but also does not imply that such implementations must exist. It is a mere indicator of an example and should not be interpreted otherwise, unless explicitly stated as such.