Apparatus and method for image guided accuracy verification

[0001] This application is a continuation of U.S. patent application Ser. No. 11/224,028, filed on Sep. 13, 2005, now abandoned which is incorporated herein by reference.

[0002] The invention relates generally to a medical device and particularly to an apparatus and method associated with image guided medical procedures.

[0003] Image guided surgery (IGS), also known as image guided intervention (IGI), enhances a physician's ability to locate instruments within anatomy during a medical procedure. IGS can include 2-dimensional (2-D) and 3-dimensional (3-D) applications.

[0004] Existing imaging modalities can capture the movement of dynamic anatomy. Such modalities include electrocardiogram (ECG)-gated or respiratory-gated magnetic resonance imaging (MRI) devices, ECG-gated or respiratory-gated computer tomography (CT) devices, and cinematography (CINE) fluoroscopy. The dynamic imaging modalities can capture the movement of anatomy over a periodic cycle of that movement by sampling the anatomy at several instants during its characteristic movement and then creating a set of image frames or volumes.

[0005] A need exists for an apparatus that can be used with such imaging devices to capture pre-procedural images of a targeted anatomical body and use those images intra-procedurally to help guide a physician to the correct location of the anatomical body during a medical procedure.

[0006] A method includes receiving during a first time interval image data associated with an image of a dynamic body. The image data includes an indication of a position of a first marker on a garment coupled to the dynamic body and a position of a second marker on the garment. The first marker is coupled to the garment at a first location. The second marker is coupled to the garment at a second location. A distance between the position of the first marker and the position of the second marker is determined. During a second time interval after the first time interval, data associated with a position of a first localization element coupled to the garment at the first location and data associated with a position of a second localization element coupled to the garment at the second location are received. A distance between the first localization element and the second localization element based on the data associated with the position of the first localization element and the position of the second localization element is determined. A difference is calculated between the distance between the first marker and the second marker during the first time interval and the distance between the first localization element and the second localization element during the second time interval.

[0016] An apparatus according to an embodiment of the invention includes a garment and two or more markers coupled to the garment. The apparatus can also include two or more localization elements coupled to the garment proximate the markers. The apparatus is configured to be coupled to a dynamic body, such as selected dynamic anatomy of a patient. Dynamic anatomy can be, for example, any anatomy that moves during its normal function (e.g., the heart, lungs, kidneys, liver and blood vessels). A processor, such as a computer, is configured to receive image data associated with the dynamic body taken during a pre-surgical or pre-procedural first time interval. The image data can include an indication of a position of each of the markers for multiple instants in time during the first time interval. The processor can also receive position data associated with the localization elements during a second time interval in which a surgical procedure or other medical procedure is being performed. The processor can use the position data received from the localization elements to determine a distance between the elements for a given instant in time during the second time interval. The processor can also use the image data to determine the distance between the markers for a given instant in time during the first time interval. The processor can then find a match between an image where the distance between the markers at a given instant in time during the first time interval is the same as the distance between the elements associated with those markers at a given instant in time during the medical procedure, or second time interval.

[0017] A physician or other healthcare professional can use the images selected by the processor during a medical procedure performed during the second time interval. For example, when a medical procedure is performed on a targeted anatomy of a patient, such as a heart, the physician may not be able to utilize an imaging device during the medical procedure to guide him to the targeted area within the patient. A garment according to an embodiment of the invention can be positioned or coupled to the patient proximate the targeted anatomy prior to the medical procedure, and pre-procedural images can be taken of the targeted area during a first time interval. Markers or fiducials coupled to the garment can be viewed with the image data, which can include an indication of the position of the markers during a given path of motion of the targeted anatomy (e.g., the heart) during the first time interval. Such motion can be due, for example, to inspiration (i.e., inhaling) and expiration (i.e., exhaling) of the patient, or due to the heart beating. During a medical procedure, performed during a second time interval, such as a procedure on a heart, the processor receives data from the localization elements associated with a position of the elements at a given instant in time during the medical procedure (or second time interval). The distance between selected pairs of markers can be determined from the image data and the distance between corresponding selected pairs of localization elements can be determined based on the element data for given instants in time.

[0018] Because the localization elements are coupled to the garment proximate the location of the markers, the distance between a selected pair of elements can be used to determine an intra-procedural distance between the pair of corresponding markers to which the localization elements are coupled. An image from the pre-procedural image data taken during the first time interval can then be selected where the distance between the pair of selected markers in that image corresponds with or closely approximates the same distance determined using the localization elements at a given instant in time during the second time interval. This process can be done continuously during the medical procedure, producing simulated real-time, intra-procedural images illustrating the orientation and shape of the targeted anatomy as a catheter or similar structure is navigated to the targeted anatomy. Thus, during the medical procedure, the physician can view selected image(s) of the targeted anatomy that correspond to and simulate real-time movement of the anatomy. In addition, during a medical procedure being performed during the second time interval, such as navigating a catheter to a targeted anatomy, the location(s) of an electromagnetic coil coupled to the catheter during the second time interval can be superimposed on an image of a catheter. The superimposed image(s) of the catheter can then be superimposed on the selected image(s) from the first time interval, providing simulated real time images of the catheter location relative to the targeted anatomy. This process and other related methods are described in pending U.S. patent application Ser. No. 10/273,598, entitled Methods, Apparatuses, and Systems Useful in Conducting Image Guided Interventions, filed Nov. 8, 2003, the entire disclosure of which is incorporated herein by reference.

[0019] FIGS. 1 and 2 are schematic illustrations of devices that can be used to perform various procedures described herein. As shown in FIG. 1, an apparatus 10 includes a garment 20. The garment 20 can be coupled to a dynamic body B. The dynamic body B can be, for example, a selected dynamic portion of the anatomy of a patient. The garment 20 can be a variety of different shapes and sizes. For example, in one embodiment the garment 20 is a tubular or sleeve configuration (see FIG. 5) and can fit, for example, around the torso of a patient, or around the upper chest surrounding, for example, the patient's heart. The garment 20 can be a continuous tubular configuration or a partial tubular configuration. For example, the garment 20 may be substantially planar prior to coupling to the dynamic body and then wrapped around the dynamic body and coupled to the dynamic body using an attachment, such as straps, hook and pile fastener, snaps, or any other suitable coupling method. In the case of a continuous tubular shape, the garment 20 may be held in position on the dynamic body through friction fit, or due to the garment being stretchable such that it conforms to the dynamic body. In another embodiment, the garment 20 is substantially planar, such as in the form of a patch that can be disposed at a variety of locations on a patient's body. Such a garment 20 can be coupled to the dynamic body with adhesive, straps, hook and pile, snaps, or any other suitable coupling method.

[0020] In some embodiments, the garment 20 is configured as a shirt to be worn by a patient. In some embodiments, the garment 20 is configured to be worn similar to a pair of pants. In still other embodiments, a garment is configured as an undergarment to be worn by a patient. For example, a garment can be configured as an undergarment to be worn on the upper torso of the patient (e.g., a brassiere). These configurations may allow, for example, placement of markers at varying angles relative to the targeted anatomy of the patient.

[0021] The garment 20 can be constructed with a variety of different materials, such as fabric, plastic, and rubber and can be flexible, stretchable and/or rigid. In some embodiments, the garment 20 is configured to constrict movement of the dynamic body B. For example, the garment 20 can be constructed in a tubular configuration with a stretchable material that when coupled to the patient's body, constricts at least a portion of the patient's movement through inhaling and exhaling or movement caused by the heart beating.

[0022] Two or more markers or fiducials 22 are coupled to the garment 20 at selected locations as shown in FIG. 1. The markers 22 are constructed of a material that can be viewed on an image, such as an X-ray. The markers 22 can be, for example, radiopaque, and can be coupled to the garment 20 using any known methods of coupling such devices. FIGS. 1 and 2 illustrate the apparatus 10 having four markers 22, but any number of two or more markers can be used.

[0023] An imaging device 40 can be used to take images of the dynamic body B while the garment 20 is coupled to the dynamic body B, pre-procedurally during a first time interval. As stated above, the markers 22 are visible on the images and can provide an indication of a position of each of the markers 22 during the first time interval. The position of the markers 22 at given instants in time through a path of motion of the dynamic body B can be illustrated with the images. The imaging device 40 can be, for example, a computed tomography (CT) device (e.g., respiratory-gated CT device, ECG-gated CT device), a magnetic resonance imaging (MRI) device (e.g., respiratory-gated MRI device, ECG-gated MRI device), an X-ray device, or any other suitable medical imaging device. In one embodiment, the imaging device 40 is a computed tomography-positron emission tomography device that produces a fused computed tomography-positron emission tomography image dataset. The imaging device 40 can be in communication with a processor 30 and send, transfer, copy and/or provide image data taken during the first time interval associated with the dynamic body B to the processor 30.

[0024] The processor 30 includes a processor-readable medium storing code representing instructions to cause the processor 30 to perform a process. The processor 30 can be, for example, a commercially available personal computer, or a less complex computing or processing device that is dedicated to performing one or more specific tasks. For example, the processor 30 can be a terminal dedicated to providing an interactive graphical user interface (GUI). The processor 30, according to one or more embodiments of the invention, can be a commercially available microprocessor. Alternatively, the processor 30 can be an application-specific integrated circuit (ASIC) or a combination of ASICs, which are designed to achieve one or more specific functions, or enable one or more specific devices or applications. In yet another embodiment, the processor 30 can be an analog or digital circuit, or a combination of multiple circuits.

[0025] The processor 30 can include a memory component 32. The memory component 32 can include one or more types of memory. For example, the memory component 32 can include a read only memory (ROM) component and a random access memory (RAM) component. The memory component can also include other types of memory that are suitable for storing data in a form retrievable by the processor 30. For example, electronically programmable read only memory (EPROM), erasable electronically programmable read only memory (EEPROM), flash memory, as well as other suitable forms of memory can be included within the memory component. The processor 30 can also include a variety of other components, such as for example, co-processors, graphic processors, etc., depending upon the desired functionality of the code.

[0026] The processor 30 can store data in the memory component 32 or retrieve data previously stored in the memory component 32. The components of the processor 30 can communicate with devices external to the processor 30 by way of an input/output (I/O) component (not shown). According to one or more embodiments of the invention, the I/O component can include a variety of suitable communication interfaces. For example, the I/O component can include, for example, wired connections, such as standard serial ports, parallel ports, universal serial bus (USB) ports, S-video ports, local area network (LAN) ports, small computer system interface (SCCI) ports, and so forth. Additionally, the I/O component can include, for example, wireless connections, such as infrared ports, optical ports, Bluetooth® wireless ports, wireless LAN ports, or the like.

[0027] The processor 30 can be connected to a network, which may be any form of interconnecting network including an intranet, such as a local or wide area network, or an extranet, such as the World Wide Web or the Internet. The network can be physically implemented on a wireless or wired network, on leased or dedicated lines, including a virtual private network (VPN).

[0028] As stated above, the processor 30 can receive image data from the imaging device 40. The processor 30 can identify the position of selected markers 22 within the image data or voxel space using various segmentation techniques, such as Hounsfield unit thresholding, convolution, connected component, or other combinatory image processing and segmentation techniques. The processor 30 can determine a distance and direction between the position of any two markers 22 during multiple instants in time during the first time interval, and store the image data, as well as the position and distance data, within the memory component 32. Multiple images can be produced providing a visual image at multiple instants in time through the path of motion of the dynamic body. The processor 30 can also include a receiving device or localization device 34, which is described in more detail below.

[0029] As shown in FIG. 2, two or more localization elements 24 are coupled to the garment 20 proximate the locations of the markers 22 for use during a medical procedure to be performed during a second time interval. The localization elements 24 can be, for example, electromagnetic coils, infrared light emitting diodes, and/or optical passive reflective markers. The markers 22 can include plastic or non-ferrous fixtures or dovetails or other suitable connectors used to couple the localization elements 24 to the markers 22. A medical procedure can then be performed with the garment 20 coupled to the dynamic body B at the same location as during the first time interval when the pre-procedural images were taken. During the medical procedure, the localization elements 24 are in communication or coupled to the localization device 34 included within processor 30. The localization device 34 can be, for example, an analog to digital converter that measures voltages induced onto localization coils in the field; creates a digital voltage reading; and maps that voltage reading to a metric positional measurement based on a characterized volume of voltages to millimeters from a fixed field emitter. Position data associated with the elements 24 can be transmitted or sent to the localization device 34 continuously during the medical procedure during the second time interval. Thus, the position of the localization elements 24 can be captured at given instants in time during the second time interval. Because the localization elements 24 are coupled to the garment 20 proximate the markers 22, the localization device 34 can use the position data of the elements 24 to deduce coordinates or positions associated with the markers 22 intra-procedurally during the second time interval. The distance between one or more selected pairs of localization elements 24 (and corresponding markers 22) can then be determined and various algorithms can be used to analyze and compare the distance between selected elements 24 at given instants in time, to the distances between and orientation among corresponding markers 22 observed in the pre-operative images.

[0030] An image can then be selected from the pre-operative images taken during the first time interval that indicates a distance between corresponding markers 22 at a given instant in time, that most closely approximates or matches the distance between the selected elements 24. The process of comparing the distances is described in more detail below. Thus, the apparatus 10 and processor 30 can be used to provide images corresponding to the actual movement of the targeted anatomy during the medical procedure being performed during the second time interval. The images illustrate the orientation and shape of the targeted anatomy during a path of motion of the anatomy, for example, during inhaling and exhaling.

[0031] FIG. 3 illustrates an example set of distances or vectors d1 through d6 between a set of markers 122, labeled m1 through m9 that are disposed at spaced locations on a garment 120. As described above, pre-procedure images can be taken of a dynamic body for which the garment 120 is to be coupled during a first time interval. The distances between the markers can be determined for multiple instants in time through the path of motion of the dynamic body. Then, during a medical procedure, performed during a second time interval, localization elements (not shown in FIG. 3) coupled proximate to the location of markers 122 can provide position data for the elements to a localization device (not shown in FIG. 3). The localization device can use the position data to determine distances or vectors between the elements for multiple instants in time during the medical procedure or second time interval.

[0032] FIG. 4A shows an example of distance or vector data from the localization device. Vectors a1 through a6 represent distance data for one instant in time and vectors n1 through n6 for another instant in time, during a time interval from a to n. As previously described, the vector data can be used to select an image from the pre-procedural images that includes distances between the markers m1 through m9 that correspond to or closely approximate the distances a1 through a6 for time a, for example, between the localization elements. The same process can be performed for the vectors n1 through n6 captured during time n.

[0033] One method of selecting the appropriate image from the pre-procedural images is to execute an algorithm that can sum all of the distances a1 through a6 and then search for and match this sum to an image containing a sum of all of the distances d1 through d6 obtained pre-procedurally from the image data that is equal to the sum of the distances a1 through a6. When the difference between these sums is equal to zero, the relative position and orientation of the anatomy or dynamic body D during the medical procedure will substantially match the position and orientation of the anatomy in the particular image. The image associated with distances d1 through d6 that match or closely approximate the distances a1 through a6 can then be selected and displayed. For example, FIG. 4B illustrates examples of pre-procedural images, Image a and Image n, of a dynamic body D that correspond to the distances a1 through a6 and n1 through n6, respectively. An example of an algorithm for determining a match is as follows:

[0034] Does Σa_i=Σd_i (i=1 to 6 in this example) OR

[0035] Does Σ(a_i−d_i)=0 (i=1 to 6 in this example).

[0036] If yes to either of these, then the image is a match to the vector or distance data obtained during the medical procedure.

[0037] FIG. 5 illustrates an apparatus 210 according to an embodiment of the invention. The apparatus 210 includes a tubular shaped garment 220 that can be constructed with a flexible and/or stretchable material. The garment 220 can be positioned over a portion of a patient's body, such as around the upper or lower torso of the patient. The stretchability of the garment 220 allows the garment 220 to at least partially constrict some of the movement of the portion of the body for which it is coupled. The apparatus 210 further includes multiple markers or fiducials 222 coupled to the garment 220 at spaced locations. A plurality of localization elements 224 are removably coupled proximate to the locations of markers 222, such that during a first time interval as described above, images can be taken without the elements 224 being coupled to the garment 220. The localization elements need not be removably coupled. For example, the elements can be fixedly coupled to the garment. In addition, the elements can be coupled to the garment during the pre-procedure imaging.

[0038] FIG. 6 is a graphical illustration indicating how the apparatus 210 (shown without localization elements 224) can move and change orientation and shape during movement of a dynamic body, such as a mammalian body M. The graph is one example of how the lung volume can change during inhalation (inspiration) and exhalation (expiration) of the mammalian body M. The corresponding changes in shape and orientation of the apparatus 210 during inhalation and exhalation are also illustrated. The six markers 222 shown in FIG. 5 are labeled a, b, c, d, e, and f. As described above, images of the apparatus 110 can be taken during a first time interval. The images can include an indication of relative position of each of the markers 222, that is the markers 222 are visible in the images, and the position of each marker 222 can then be observed over a period of time. A distance between any two markers 222 can then be determined for any given instant of time during the first time interval. For example, a distance X between markers a and b is illustrated, and a distance Y between markers b and f is illustrated. These distances can be determined for any given instant in time during the first time interval from an associated image that illustrates the position and orientation of the markers 222. As illustrated, during expiration of the mammalian body M at times indicated as A and C, the distance X is smaller than during inspiration of the mammalian body M, at the time indicated as B. Likewise, the distance Y is greater during inspiration than during expiration. The distance between any pair of markers 222 can be determined and used in the processes described herein. Thus, the above embodiments are merely examples of possible pair selections. For example, a distance between a position of marker e and a position of marker b may be determined. In addition, multiple pairs or only one pair may be selected for a given procedure.

[0039] FIG. 7 is a flowchart illustrating a method according to an embodiment of the invention. A method 50 includes at step 52 receiving image data during a pre-procedural or first time interval. As discussed above, images are taken of a dynamic body using an appropriate imaging modality (e.g., CT Scan, MRI, etc.). The image data is associated with one or more images taken of a garment (as described herein) coupled to a dynamic body, where the garment includes two or more markers coupled thereto. In other words, the image data of the dynamic body is correlated with image data related to the garment. The one or more images can be taken using a variety of different imaging modalities as described previously. The image data can include an indication of a position of a first marker and an indication of a position of a second marker, as illustrated at step 54. The image data can include position data for multiple positions of the markers during a range or path of motion of the dynamic body over a selected time interval. As described above, the image data can include position data associated with multiple markers, however, only two are described here for simplicity. A distance between the position of the first marker and the position of the second marker can be determined for multiple instants in time during the first time interval, at step 56. As also described above, the determination can include determining the distance based on the observable distance between the markers on a given image. The image data, including all of the images received during the first time interval, the position, and the distance data can be stored in a memory and/or recorded at step 58.

[0040] Then at step 60, during a second time interval, while performing a medical procedure on the patient with the garment positioned on the patient at substantially the same location, position data can be received for a first localization element and a second localization element. The localization elements can be coupled to the garment proximate the locations of the markers, such that the position data associated with the elements can be used to determine the relative position of the markers in real-time during the medical procedure. The position data of the elements can be stored and/or recorded at step 62.

[0041] A distance between the first and second localization elements can be determined at step 64. Although only two localization elements are described, as with the markers, position data associated with more than two localization elements can be received and the distances between the additional elements can be determined.

[0042] The next step is to determine which image from the one or more images taken during the first time interval represents the relative position and/or orientation of the dynamic body at a given instant in time during the second time interval or during the medical procedure. To determine this, at step 66, the distance between the positions of the first and second localization elements at a given instant in time during the second time interval are compared to the distance(s) determined in step 56 between the positions of the first and second markers obtained with the image data during the first time interval.

[0043] An image can be selected from the first time interval that best represents the same position and orientation of the dynamic body at a given instant in time during the medical procedure. To do this, the difference between the distance between a given pair of localization elements during the second time interval is used to select the image that contains the same distance between the same given pair of markers from the image data received during the first time interval. This can be accomplished, for example, by executing an algorithm to perform the calculations. When there are multiple pairs of markers and localization elements, the algorithm can sum the distances between all of the selected pairs of elements for a given instant in time during the second time interval and sum the distances between all of the associated selected pairs of markers for each instant in time during the first time interval when the pre-procedural image data was received.

[0044] When an image is found that provides the sum of distances for the selected pairs of markers that is substantially the same as the sum of the distances between the localization elements during the second time interval, then that image is selected at step 68. The selected image can then be displayed at step 70. The physician can then observe the image during the medical procedure on a targeted portion of the dynamic body. Thus, during the medical procedure, the above process can be continuously executed such that multiple images are displayed and images corresponding to real-time positions of the dynamic body can be viewed.

[0045] While various embodiments of the invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of the invention should not be limited by any of the above-described embodiments, but should be defined only in accordance with the following claims and their equivalents.

[0046] The previous description of the embodiments is provided to enable any person skilled in the art to make or use the invention. While the invention has been particularly shown and described with reference to embodiments thereof, it will be understood by those skilled in art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. For example, the garment, markers and localization elements can be constructed from any suitable material, and can be a variety of different shapes and sizes, not necessarily specifically illustrated, while still remaining within the scope of the invention.