Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
  • A61B1/31—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor for the rectum, e.g. proctoscopes, sigmoidoscopes, colonoscopes
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B1/00—Instruments for performing medical examinations of the interior of cavities or tubes of the body by visual or photographical inspection, e.g. endoscopes; Illuminating arrangements therefor
  • A61B1/00002—Operational features of endoscopes
  • A61B1/00043—Operational features of endoscopes provided with output arrangements
  • A61B1/00045—Display arrangement
  • A61B1/0005—Display arrangement combining images e.g. side-by-side, superimposed or tiled
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/06—Devices, other than using radiation, for detecting or locating foreign bodies ; determining position of probes within or on the body of the patient
  • A61B5/061—Determining position of a probe within the body employing means separate from the probe, e.g. sensing internal probe position employing impedance electrodes on the surface of the body
  • A61B5/064—Determining position of a probe within the body employing means separate from the probe, e.g. sensing internal probe position employing impedance electrodes on the surface of the body using markers
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/42—Detecting, measuring or recording for evaluating the gastrointestinal, the endocrine or the exocrine systems
  • A61B5/4222—Evaluating particular parts, e.g. particular organs
  • A61B5/4255—Intestines, colon or appendix
• • G—PHYSICS
  • G06—COMPUTING; CALCULATING OR COUNTING
  • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
  • G06T11/00—2D [Two Dimensional] image generation
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
  • A61B5/00—Measuring for diagnostic purposes; Identification of persons
  • A61B5/06—Devices, other than using radiation, for detecting or locating foreign bodies ; determining position of probes within or on the body of the patient
  • A61B5/061—Determining position of a probe within the body employing means separate from the probe, e.g. sensing internal probe position employing impedance electrodes on the surface of the body
  • A61B5/062—Determining position of a probe within the body employing means separate from the probe, e.g. sensing internal probe position employing impedance electrodes on the surface of the body using magnetic field

Definitions

• the invention relates generally to colonoscopy procedures and apparatus.
• the invention is a method and apparatus for tracking and evaluating a colonoscopy procedure and for providing a display representative of the visualization and evaluation in real time during the procedure.
• Colonoscopy is the most prevalent screening tool for colorectal cancer. Its effectiveness, however, is subject to the degree to which the entire colon is visualized during an exam. There are several factors that may contribute to incomplete viewing of the entire colonic wall. These include particulate matter in the colon, subject discomfort/motion, physician attention, the speed at which the endoscope is withdrawn, and complex colonic morphology. There is, therefore, a continuing need for methods and apparatus for enhancing the visualization of the colon during colonoscopy.
• the invention is a system for evaluating a colonoscopy procedure performed using an endoscope.
• One embodiment of the invention includes a tracking input, a video input, a processor and a display output.
• the tracking input receives position data representative of the location and/or orientation of the endoscope within the patient's colon during the procedure.
• the video input receives video data from the endoscope during the procedure.
• the processor is coupled to the tracking input and video input, and generates visualization metrics as a function of the video data and evaluation display information representative of the visualization metrics at associated colon locations as a function of the visualization metrics and the position data.
• the display output is coupled to the processor to output the evaluation display information.
• Figure 1 is diagram of a colonoscopy tracking and evaluation system in accordance with one embodiment of the invention.
• Figure 2 is a diagram of one embodiment of the image and signal processing that can be performed by the system shown in Figure 1.
• Figure 3 is an illustration of one embodiment of the colon model reconstruction that can be performed by the system shown in Figure 1.
• Figure 4 is an illustration of images processed by the system shown in
• Figure 1 for evaluation of sharpness and blur.
• Figure 5 is an illustration of a video image within a colon that can be produced by the system shown in Figure 1 , with identified stool highlighted in color.
• Figure 6 is an illustration of a video image within a colon that can be produced by the system shown in Figure 1, with the image divided into regions.
• Figure 7 is an illustration of an endoscope in accordance with the system shown in Figure 1 within a colon, showing a range of fields of view.
• Figure 8 is an illustration of a colon and endoscope viewing vectors with respect to the endoscope centerline and endoscope path.
• Figures 9 A and B are illustrations of a tracker in an endoscope, the system and an interface in accordance with one embodiment of the invention.
• Figure 10 is an illustration of one embodiment of a display that can be generated by the system shown in Figure 1.
• Figure 11 is one embodiment of an image of a colon that can be generated by the system shown in Figure 1.
• Enhanced colonoscopy in accordance with one embodiment of the invention includes the combination of magnetic or other tracking technology, video data from the colonoscope, and signal processing software.
• the use of enhanced colonoscopy identifies regions of the colon that may have been missed or inadequately viewed during an exam.
• the addition of data from a preceding CT colography scan (if one was performed) is incorporated in other embodiments, and would provide additional benefit when available. Any pre-acquired data can be used for this purpose, including CT, MR or Nuclear Medicine scan to provide structural information (e.g., the shape of the colon) or functional information (e.g., potential lesions).
• FIG. 1 is a diagram of the acquisition system.
• the illustrated embodiment of guidance system 20 has 4 inputs and one output. One input is from the scope tracker(s) 22.
• the trackers 22 may be introduced through the access port of the endoscope 24 to the tip of the scope, integrated into the scope, or attached via a large "condom" type of sleeve over the scope (not shown).
• Another input is from a patient reference tracker 26 that is taped to the patient 29.
• a magnetic reference 28 is attached to the patient table 30 in close proximity to the patient in order to generate a magnetic field signal which the tracker system uses to determine the position of the scope 24 and patient 29 via reference tracker 26 during the procedure.
• An endoscope video cable 32 is connected from the output of the standard colonoscopy system 34 to a digitizer card located in the guidance system 20.
• the guidance system 20 processes the data in real-time (or with sufficiently low latency to provide timely information) and generates a processed video data stream which is connected to a standard LCD TV 36 or other display found in most (if not all) colonoscopy suites. Other embodiments (not shown) use alternative tracking technologies including mechanical tracing (e.g., shape tape) and imaging (e.g., fluoroscopy). [0017]
• the endoscopist conducts the colonoscopy in a routine manner using the standard LCD TV 36.
• the guidance system 20 can record and process both the scope position and video data and generate a visualization which will approximately represent the colon in 3D and provide feedback about regions of the colon which have been missed or poorly viewed.
• the display can be generated in real time or otherwise sufficiently fast to enable the endoscopist to utilize the information from the display without disturbing normal examination routine.
• Other display approaches that provide the visualization information described herein can be used in other embodiments of the invention.
• Figure 2 is a flow chart of one embodiment of the image and signal processing approaches that can be used with the invention. Other embodiments can use other approaches.
• scopet a sampled 3D position (x, y, z) from scope at time t —
• the set of patient-corrected scope position points may require filtering to reduce noise depending on the quality of the tracked data. Both linear and non-linear filtering methods can be used alone or in combination depending on the type of noise present.
• Linear filtering can be used to uniformly remove high frequency noise
• a moving average filter of size N may be implemented as:
• Non-linear filtering can be used to remove spurious noise from the data in which single samples are well-outside of specification. For example,
• the purpose of reconstruction is to use the collected points to generate an approximate model of the colon based on the position of the scope during an exam. This is illustrated in Figure 3.
• the method generates a centerline of the colon ( ⁇ C ⁇ ) which is needed in subsequent processing.
• the centerline can be created from a pre-defined model or a model can be created from a pre-defined centerline.
• the centerline When using a pre-defined centerline, the centerline, ⁇ C ⁇ , can be approximated from the sampled scope positional data.
• ⁇ C ⁇ can be approximated from the sampled scope positional data.
• Spline-fitting Splines may be used to reduce the number of points in ⁇ P ⁇ while smoothing as well.
• Statistical centerline calculation In this approach, the center-line is calculated from a statistical volume created from ⁇ P ⁇ .
• One such approach to create a statistical volume is through a parzen windows function
• the resulting volume provides a likelihood map of the location of the interior of the colon.
• the map can be thresholded to generate a mask of where the scope has traveled, defining the interior of the colon.
• a shortest path method can be used to generate the centerline from the mask.
• a model can be generated, for example, by extruding a primative shape along the points in ⁇ C ⁇ .
• the primative is defined as a discrete set of ordered points at a fixed radius (r) which describe a circle
• the model of the colon can be fit to the tracking data.
• the pre-defined model is deformed to fit the tracker data.
• the virtual model can be "pliable" in the virtual sense such that it can be stretched or twisted to fit the tracker data.
• Either a patient-specific virtual model or a generic anatomic virtual model can be used to register the tracker data.
• This fitting task would initialize the pre-determined model (and its corresponding centerline ⁇ C ⁇ ) - which can be derived from pre-existing generic data or the patient's image data - in the space of ⁇ P ⁇ .
• the task to align the pre-defined model with the positional data ⁇ P ⁇ can be achieved with several methods including, landmark and surface fitting.
• anatomical landmarks such as the appendiceal orifice and ileocecal valve in the cecum, the hepatic flexure, the triangular appearance of the trans-verse colon, the splenic flexure, and the anal verge at the lower border of the rectum can be used to align specific points (Pt) from ⁇ P ⁇ with corresponding points in the model.
• the pre-determined model can be deformed (with or without constraints) such that it maximizes the number of P t from ⁇ P ⁇ which fall within the interior of the model.
• the tracker data can be used to compute an approximation of the centerline of the colon.
• a generic surface can be created with a circular cross section having a fixed radius. While these approaches may not specifically reconstruct the exact true geometry of the colon, the true surface geometry is not required for guiding the procedure in accordance with the invention.
• Any of a number of image quality metrics can be determined from the video data. These include intensity, sharpness, color, texture, shape, reflections, graininess, speckle, etc. To realize real-time processing with the system, metrics can be approximated or sparsely sampled for computational efficiency. Intensity, for example, may serve as a useful metric of quality - darker regional intensity is a lower quality region whereas higher regional intensity is better image data.
• Regional intensity for example, may serve as a useful metric of quality - darker regional intensity is a lower quality region whereas higher regional intensity is better image data.
• ROIs regions of interest
• each video image can also be partitioned into nine regions a-i as shown in Figure 6.
• Each region is evaluated based on image intensity using the assumption that the far field is darker than the near field. Together, the intensity regions can be used to determine the direction of viewing along with depth of viewing. For example, if regions a, b, & c, are dark while regions g, h, & i, are bright, it suggests that the camera is pointed right with a, b, & c, in the far field.
• each region will map the processed data to centerline points at the tip of the scope (near field), a small distance out (middle field), or a long distance away (far field). It is expected that most of the data at the near and far field will be of lower quality.
• Figure 7 shows the near, middle, and far fields, associated with their corresponding centerline positions.
• the fusion of the model, original data, and results of the video data constitute the parametric mapping component.
• the tracker data is normalized to the centerline of the colon to generate "standard views" from the scope. The benefit is that if the same section is viewed multiple times from different angles, the corresponding "standard view" will be the same.
• the patient tracker position can be subtracted from the endoscope tracker position to ensure that any gross patient motion is not characterized as endoscope motion. Since the magnetic reference is attached to the table, table motion is effectively eliminated because the table position relative to the magnetic reference will not change.
• Each endoscope tracker point can be mapped to the pre-defined centerline by determining the closest centerline point to the vector defined by the tracker data. Accordingly, if the endoscope doesn't move, but looks to sides such as left or right, then all the acquired video frames will be associated with the same centerline point, but at different viewing angles.
• mapping is as follows in one embodiment of the invention, although other approaches can be used.
• Each point of the originally sampled points (P ⁇ ) is projected to a point along the centerline ( ⁇ C ⁇ ). This is calculated as the point on the centerline which is the minimum distance to each P t .
• Figure 8 illustrates this step.
• the metrics may be aggregated together:
• ⁇ S ⁇ % tu ⁇ tn /; ⁇ (t'(IM t at q t )
• the aggregate function may be an average, max, min, median, or other functions.
• the ⁇ IM ⁇ set is then used to color onto the surface of the M at each vertex.
• FIG. 11 is an example of a colon image generated by the method and system of the invention, with red areas showing regions of low-quality images, green areas showing regions of high-quality images, and blue areas showing regions of the colon with no visual confirmation of viewing based on the video.
• the intensity of the color patches can be used to indicate the number of frames viewed at that position in the colon.
• sub-regional analyses can display the color patches radially distributed around the centerline position.
• the virtual model may be built using any subset of sample points, however, it is advantageous in some embodiments to build the model during insertion and used to guide during removal.
• Figure 10 is an illustration of a display that can be presented on the LCD TV. During review of the virtual model, previously acquired video frames can also be displayed for review.
• the system is implemented on a mobile cart which can be brought into a procedure room prior to the start of a colonoscopy. Other versions can be fully integrated into the procedure room.
• Figure 9 shows one embodiment of the tracker in an endoscope, the entire system, and the interface.
• the computational component is a multi-core computer (e.g., Quad-core Dell computer) with large amounts of memory and disk.
• a medium-ranged magnetic tracker e.g., Ascension Technologies MicroBird tracker
• the transmitter is attached to a stand which is attached to the patient table during a procedure.
• the system contains a high end video capture card (e.g., EPIX systems) which acquires all of the data from the colonoscopy system.
• the tracking sensors on the scope can be hardwired or made wireless. There can be one or more sensors along the shaft of the scope. Multiple sensors along the shaft of the scope can be used to detecting "looping" of the scope/bowels during insertion.
• the sensors can be attached/embedded within a sleeve or condom to retrofit the sensors to any current scope.
• the software is a multi-threaded application which simultaneously acquires both the tracker data and video data in real-time.
• the data is processed in real-time and drawn to the screen.
• the same display is also sent to the LCD TV in the procedure room.
• the invention can be performed using segmental analysis. In this embodiment, the colon will be divided into segments.
• These segments can include, but not be limited to, the cecum, proximal to mid ascending colon, mid ascending to hepatic flexure, hepatic flexure, proximal to mid transverse colon, mid transverse to splenic flexure, splenic flexure, proximal descending to mid descending, mid descending to proximal sigmoid, sigmoid, and rectum.
• Each segment can be visualized at least twice and the data images analyzed and compared to determine the degree of visualization. For example a concordance between sweeps 1 and 2 of 100% can be interpreted as to mean that 100% of the mucosa was visualized, while a lower level of concordance may indicate ever decreasing visualization rates.
• These data sets will be computed in real time or near- to-real time and the information provided in a variety of means, including visual and/or auditory in order to inform the proceduralist of the results and aid in decision making regarding adequate visualization of the mucosa.
• Prior exam data can be incorporated into other embodiments of the invention.
• prior examination data from two sources can be used.
• One source of prior data is pooled data from multiple endoscopists. This data could provide a statistical likelihood and 95% CI (confidence interval) that the mucosa in a given segment of the colon has been visualized with blur free images.
• Data used to provide this instrument could include examinations where mucosal surface visualized has been verified by more than one examiner, or by correlation with another technology such as CT colonography.
• Other relevant data that might modify the likelihood can include the speed of withdrawal, the specific anatomic segment (variable likelihood in different segments), the number of times the segment has been traversed, etc.
• the second source of prior data is examinations from the specific endoscopist.
• Endoscopist specific modifiers of the likelihood of complete mucosal visualization could include the speed of withdrawal, and perhaps even some seemingly unrelated factors like the specific endoscopist's overall polyp detection rate, etc. (i.e. some endoscopists might need more of an accuracy handicap than others).
• Relevance feedback can also be incorporated into the invention.
• information provided by the computer system is tailored to be non-disruptive yet compulsive in indicating the extent and quality of visualization within a temporal and/or spatial block. This is achieved through a relevance feedback framework wherein the system gauges the efficacy of its extent/quality cues as a function of the endoscopist's subsequent response and uses this information to iteratively achieve an improved cueing subsequently.
• the system provides extent/quality cues to the recently visualized segment and objectively interprets the subsequent actions of the endoscopist as to whether, and to what degree, the cues are relevant or irrelevant to the exam.
• the system then learns to adapt its assumed notion of quality and or coverage to that of the endoscopist.
• the feedback operates in both greedy and cooperative user modes. In the greedy mode, the system provides feedback for every recently visualized region. In the cooperative user mode wherein a segment is repeatedly visualized in multiple sweeps, the feedback progressively learns, unlearns and relearns its judgment.
• Computational strategy for achieving relevance feedback involves "active learning” or “selective sampling” of extent/quality-sensitive features, in-order to achieve the maximal information gain, or minimized entropy/uncertainty in decision-making.
• Active learning provides accumulation, stratification and mapping of knowledge during examination from time to time, segment to segment, endoscopist to endoscopist and from patient to patient. Resultant mapping learned across the spectrum can potentially minimize intra-exam relevance feedback loops which might translate into an optimal examination.
• An accelerometer can also be incorporated into embodiments of the invention described herein.
• An accelerometer embedded at or near the tip of the colonoscope will provide feedback regarding the motion of the scope.
• the "forward” and “backward” motion of the scope provides useful information about the action of the endoscopist.
• "Forward” actions in most but not all cases) are used during insertion to feed the scope through the colon;
• "backward” motion in most cases but not all) is the removal of the scope and is often associated with viewing of the colon.
• the path of the scope path may be constructed during insertion only, whereas image analysis may occur during removal.
• multiple forward and back motions may indicate direct interrogation of folds or other motions which would confound the automated analysis; this could be determined from the accelerometer data.
• Additional accelerometers can be populated along the length of the scope.
• the combination of accelerometers can be used to infer some features of the shape of the scope.
• multiple adjacent sensors could be used to detect looping of the scope.
• the repeated capture of multiple accelerometers can be used to reconstruct the path of the entire scope.
• An inertial navigation system generally a 6 DOF (degree of freedom) measurement device containing accelerometers and gyroscopes — can also provide local motion estimates and be combined with other INS devices to infer features of the entire scope including the shape of the scope.
• INS inertial navigation system
• a stereoscopic view/laser range finder can be incorporated into the invention. Reconstruction of the local 3D geometry can be achieved through several different methods. A combination of stereo views and image processing (texture/feature alignment) can be used to reconstruct the 3D geometry from a scene. Stereo optics can, for example, be incorporated into the colonscope. Alternatively, a specialty lens could be attached to the tip of a scope to achieve a stereoscopic view.
• a visible light filter can be swept across the scene to reconstruct the 3D surface (in a manner similar to laser surface scanners and/or laser range finders).
• a combination of multiple views from a tracked camera can also be used to reconstruct the interior surface of the colon.
• the reconstructed 3D surface can be used to detect disease such as polyps (based on curvature), evaluate normal, abnormal, and extent of folding of the colon wall, and precisely measure lesion size.
• Insufflation can also be used in connection with the invention. Poor insufflation of the colon results in poor viewing of the colon wall (particularly behind folds). Automatically determining the sufficient insufflation is an important process to incorporate in the system. Using a 3D surface reconstruction system the uniformity of the colon wall can be used as a metric for proper insufflation. The extent of folds can also be estimated from the video data. Specifically, local image features such as the intensity gradient can be used to determine the shape and extent of folds within the field of view. Finding a large number of image gradients located in close proximity suggests a fold in the colon wall. Alternatively, by varying the insufflation pressure slightly, the changes in image features (such as gradients) can provide an estimate of fold locations and extent of folds.

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• 2009
  • 2009-11-23 EP EP09828347.6A patent/EP2358259A4/en not_active Withdrawn
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  • 2009-11-23 JP JP2011537686A patent/JP2012509715A/ja active Pending
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