WO2007131177A2

WO2007131177A2 - Method and apparatus for visualization of a flexible body

Info

Publication number: WO2007131177A2
Application number: PCT/US2007/068258
Authority: WO
Inventors: Eigil Samset
Original assignee: The Brigham & Women's Hospital, Inc.
Priority date: 2006-05-04
Filing date: 2007-05-04
Publication date: 2007-11-15
Also published as: WO2007131177A3

Abstract

A plurality of sensors (110) are disposed at least adjacent to portions of a flexible body (100) such as a catheter or endoscope that can be inserted into a cavity (123). Each sensor (110) is capable of sensing at least five degrees of freedom for the point of the flexible body (100) to which it is attached. A computing device (115) operatively connected to the plurality of tracking sensors (110) receives signals from the sensors (110) such that the computing device (115) may determine a shape and/or visualization (130) of the flexible body (100) and overlay it with various images of at least a portion of the cavity (123). The sensed portions of the flexible body (100) may be used to automatically determine the portions of the cavity (123) to image.

Description

METHOD AND APPARATUS FOR VISUALIZATION OF A FLEXIBLE BODY

Related Applications

[0001] This application claims the benefit of U.S. Provisional Application No.

60/746,435, filed May 4, 2006, the contents of which are fully incorporated herein by this reference.

Technical Field

[0002] This invention relates generally to the visualization of objects within a body and more specifically to visualization of a catheter or other flexible body within a living body.

Background

[0003] Many imaging techniques are known, and the development of ever-improving imaging techniques has been of tremendous benefits to the medical field. Improved medical imaging has led to advancements in diagnostic techniques as well as in the application of therapy or other treatments. Those in the medical profession increasingly use these imaging techniques to assist diagnosis and navigation within the body to aid the placement of catheters or other diagnosis or therapy delivering systems.

[0004] It is known to image or visualize catheters via fluoroscopic x-ray imaging, where the catheter body can be seen in the images as a radio-opaque shape. Some techniques have also been developed to let a catheter appear bright under MRI imaging. Catheter visualization without imaging can be useful to reduce x-ray exposure or where the catheter cannot readily be depicted with an imaging device. Such visualization can be achieved by embedding small tracking sensors inside the catheter. Existing solutions include placing a single six (6) degree of freedom ("DOF") sensor in the tip of the catheter (which does not give a visualization of the catheter trajectory or shape). Another known solution includes positioning a plurality of 3 DOF sensors along the catheter. By using multiple sensors, the shape of the catheter can be visualized by connecting the measured positions of the individual sensors with line segments or splines. This connecting of points represents an interpolation or estimation from the sparsely sampled points (where the sensors are placed) along the flexible body and gives a rough approximation of the shape and placement of the catheter. Changing certain characteristics of the catheter, however, leads to widely varying error in the approximation of the catheter, which in turn diminishes the usefulness of such visualization.

Brief Description of the Drawings

[0005] The above needs are at least partially met through provision of the method and apparatus for visualization of a flexible body described in the following detailed description, particularly when studied in conjunction with the drawings, wherein:

[0006] FIG. 1 comprises a perspective view of an imaging system as applied to a human patient as configured in accordance with various embodiments of the invention;

[0007] FIG. 2 comprises a perspective view of a flexible body as configured in accordance with various embodiments of the invention;

[0008] FIG. 3 A comprises a perspective view of an example sensor;

[0009] FIG. 3B comprises a side view of an example sensor;

[0010] FIG. 4 comprises a block diagram of an imaging system configured in accordance with various embodiments of the invention;

[0011] FIGS. 5A, 5B, and 5C comprise comparisons of a simulated flexible body position as compared to the results of three methods for simulating the flexible body's position;

[0012] FIG. 6 comprises a flow diagram of sensing a location of a flexible body as configured in accordance with various embodiments of the invention;

[0013] FIGS. 7A, 7B, and 7C comprise example visualizations of a flexible body and cavity as configured in accordance with various embodiments of the invention;

[0014] FIG. 8 comprises example visualizations of a flexible body and anatomy as configured in accordance with various embodiments of the invention;

[0015] FIG. 9 comprises an example imaging system configured in accordance with various embodiments of the invention;

[0016] FIG. 10 comprises an example imaging system configured in accordance with various embodiments of the invention. [0017] Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein.

Detailed Description of the Preferred Embodiment(s)

[0018] The above needs are at least partially met through provision of the method and apparatus for visualization of a flexible body. Generally speaking, a flexible body such as a catheter or endoscope is inserted into a cavity, typically a body cavity of a patient. A plurality of sensors are disposed at least adjacent to portions of the flexible body. Typically, the sensors are embedded inside the flexible body. For flexible devices with working channels, the sensors may be placed inside one working channel. Each sensor is capable of sensing at least five degrees of freedom for the point of the flexible body to which it is attached. A computing device operably connected to the plurality of tracking sensors receives signals from the sensors such that the computing device may determine a shape and/or visualization of the flexible body with reduced error. The visualization can then be combined with images of the cavity to provide substantially accurate images of the placement of the flexible body in the cavity. By another approach, the information from the tracking sensors can be used to determine where or what portions of the cavity should be imaged.

[0019] More particularly, in one such application, one may provide a visualization of a catheter (or other flexible body/spline) based on embedded tracking sensors. The tracking sensors may sense 5 DOF or 6 DOF. The measured positions of the sensed portions of the flexible body are interpolated using a known mathematical description called a cubic spline. A cubic spline is continuous in its Oth, 1st, and 2nd derivate. Although the shape of a catheter and/or endoscope can be detected and visualized using 3 DOF sensors, if 3 DOF sensors are used, the 1st and 2nd derivate have to be estimated thereby introducing error to the visualization. In this case, changing the direction of a catheter through a control point (while keeping the position constant) can lead to significant changes and error in the estimated shape of the flexible body. When using a 5 DOF or a 6 DOF sensor, the direction (the 1st derivate unit tangential vector) can be measured without estimation. Therefore, extra information is available about the direction of the catheter when passing through a control point or sensor. This extra information provides a more accurate visualization of the flexible body that can then be displayed. Moreover, the length of the 1st derivate tangential vector can also be accurately estimated, using a priori or known information about the configuration of the sensor assembly within the catheter (e.g., the distance between each sensor element).

[0020] These and other benefits may become clearer upon making a thorough review and study of the following detailed description. Referring now to the drawings, and in particular to FIG. 1, an apparatus includes a flexible body 100 with a plurality of sensors 110 disposed at least adjacent to portions of the flexible body 100 to sense a position and an orientation of the portions of the flexible body 100 with at least five degrees of freedom. The plurality of sensors 110 are configured to be operatively connected to a computing device 115 such that signals from the sensors 110 are received by the computing device 115 whereby the computing device 115 may determine a visualization of the flexible body 110.

[0021] An imaging device 120 may be disposed relative to a cavity 123 to provide imaging data for the cavity 123 in which the flexible body 100 can be disposed. The imaging device 120 can be a magnetic resonance imaging ("MRI") device, a computed tomography ("CT" or "CAT") device, an ultrasound scanner, and/or an x-ray system although other imaging devices may be used. A visual output device 125 may be operatively coupled to the computing device 115 and the imaging device 120 wherein the visual output device 125 displays images 130 of at least one of the cavity 123 and the flexible body 100.

[0022] With reference to FIG. 2, an example flexible body 100 includes four sensors

110 embedded therein. The flexible body 100 may comprise many forms. For example, a catheter is a flexible body used in several medical procedures where the catheter moves within various body cavities. Another example includes a flexible endoscope. Yet another example includes a flexible ultrasound probe. Another example is a flexible robot or other type of flexible manipulator or device. The flexible body 100 includes a plurality of sensors 110 such that the sensors 110 help determine the location and orientation of the portion of the flexible body 100 to which each sensor 110 is anchored. The sensors 110 are disposed along the length of the flexible body 100 from a distal end 205 to a proximal end 210. The number of sensors 110 disposed along the flexible body 100 can vary although two to four sensors 110 are adequate for many applications. Each sensor 110 typically has wires extending along the length of the flexible body 100 toward the proximal end 210 whereupon the wires provide coupling to electronics, including a computing device 115, to receive the signals from the sensors 110. It is contemplated that wireless coupling between the sensors 110 and the electronics may be applied.

[0023] With reference to FIGS. 3A and 3B, two example sensors will be described.

The first example sensor 301 is an orthogonal micro-coil, with three wire coils 305, 310, and 315 disposed in a mutually orthogonal arrangement and capable of sensing 6 DOF, although any sensor capable of sensing in at least 5 DOF may be used such as a sensor with two orthogonal coils. The second example sensor 302 is a different orthogonal arrangement of wire coils 335, 340, and 345. Typically, several turns of wire are used for each coil to provide sufficient sensitivity to an applied magnetic field. Accordingly, the second example sensor 302 may be used in applications requiring a reduced profile. The configuration of the orthogonal sensors may vary, and signal processing and calibration can compensate for imperfections in the coils' orthogonal alignment.

[0024] Generally speaking, each wire coil of a sensor generates a current when exposed to a time-varying magnetic field, such as the field-generator of an electro-magnetic tracking system or the imaging gradient magnetic fields of an MRI scanner. The currents created by application of a known magnetic field can be measured and analyzed to determine the location and orientation of each sensor 110. Typically, wires 320 extend from the wire coils along the length of the flexible body 100 to operatively connect to electronics that sense the currents generated by the coils. Because the currents created in the coils are dependant on the orientation of the coils relative to the known applied magnetic field, the currents can be analyzed to determine the coils' positioning and orientation in the magnetic field. It is contemplated that other types of remote position sensing using similar or different sensors and/or signal generators may be used.

[0025] The sensed positioning and orientation information can then be used to provide a visualization of the flexible body 100. The coordinate system of the tracking system for the flexible body 100 will typically be different from the coordinate system of the imaging system 120. In the case of interventional MRI-guided procedures, an inherit static relationship often exists between the two coordinate systems because they are measured using the same magnetic gradient fields. In other applications, a registration or calibration step may be necessary. To perform registration, a set of corresponding points in the two coordinate systems (landmarks or fiducials) may be identified, and the relationship between the coordinate systems can be computed using algorithms known in the art such as singular value decompositions. Instead of fiducials, two point-clouds may be measured in both coordinate systems, and the relationship of the point-clouds may be computed using an algorithm known in the art such as the iterative closest point algorithm. If there is a static, but unknown, relationship between the imaging and tracking coordinate systems, a one-time calibration procedure, similar to the registration procedure, may be performed. The resulting transformation between the coordinate systems will be applied in the visualization to ensure that the images and the estimated trajectory of the flexible body are spatially aligned. Those skilled in the art will appreciate that the above-described processes are readily enabled using any of a wide variety of available and/or readily configured platforms, including partially or wholly programmable platforms as are known in the art or dedicated purpose platforms as may be desired for some applications.

[0026] An example approach to arranging the electronics for the system is described with reference to FIG. 4. The system 400 includes a tracking system 410 operatively connected to the sensors 110 to receive the signals from the sensors 110. One example tracking system 410 is the Endoscout system available from Robin Medical Inc. in Baltimore, Maryland. The tracking system 410 calculates the position information from the sensors' 110 signals. The tracking system 410 is operatively connected to a scanning system control 420 for an MRI scanning system 120. The scanning system control 420 controls the MRI scanning system 120 including controlling the cavity areas scanned by the system. The scanning system control 420 uses the tracking data from the tracking system 410 to automatically determine where to scan such that scanning may proceed in near or at real-time along with the movement of the flexible body 100 in the cavity 123. In other approaches, the scanning system 120 may be an x-ray imaging or CT imaging device where a user manually controls the imaging device after viewing a visualization of the flexible body 100. In such an approach, the scanning system control 420 may be disassociated from the other elements of FIG. 4 but for the scanning system 120.

[0027] In the example of FIG. 4, the scanning system control 420 and scanning system

120 are also operatively connected to a reconstruction system 430. The reconstruction system 430 takes the imaging data from the scanning system 120 and processes it according to the view information received from the scanning system control 420 or directly entered by a user to create an image for a user. The view information can be taken from the tracking system 410 data or determined by a user.

[0028] The visualization system 440 is operatively connected to the reconstruction system 430, scanning system control 420, and the tracking system 410 such that the visualization system 440 can create visualizations of the imaged body and the flexible body 100. In other words, the visualization system 440 can take information from the reconstruction system 430, scanning system control 420, and the tracking system 410 so as to create a visualization of the flexible body 100 and/or combine the flexible body visualization with images of the cavity 123 from the scanning system 120. The visualization system 440 can provide the visualization to a display 125 for viewing by a user. Although in this example, each element comprises a separate machine, computer, or device, it is contemplated that one or more of the elements can be enabled and realized via a shared platform such as the computing device 115. It will also be understood that such a shared platform may comprise a wholly or at least partially programmable platform as are known in the art.

[0029] An example simulation of calculating the position of the flexible body 100 using a cubic spline function is described below. In this case, the flexible body 100 comprises a deflectable electro physiological catheter with three sensors 110 that each sense six DOF. The sensors 110 according to this simulation have outer dimensions of 1.2 millimeters (about 0.047 inches) by 5 millimeters (less than 0.2 inches) and are separated by 50 millimeters (less than 2 inches) and 150 millimeters (about 5.9 inches) along the flexible body 100. [0030] It is assumed that the catheter can be described as a tubular structure connecting a collection of points. Each sensor 110 constitutes one such point, while the points along the catheter between the sensors 110 will be estimated. The sensor 110 positions are called control points (or knots) and denoted according to the following formula:

P₁ = (X₁ ^ z₁ ) .

In this case, i is either 1, 2, or 3 (mathematically represented as z^' e [l,3]) because three sensors 110 are used, although other numbers of sensors can be used as seen, for example, in FIG. 2 at Pi, P₂, P₃, and P₄. The points along the catheter between the sensors 110 are interpolated using a smooth parametric curve having the equation:

P(s) = (x(s),y(s),z(s)) where s varies between zero and one. Thus, the goal is to find the smooth functions x(s), y(s), and z(s) so that:

P(O) = (X(O), ^(0), z(0)) = {x_l ,y,,z_l) = P_l

and

P(Y) = (X(Y), y(l), z(l)) = (x_/+1 , y_l+l , Z₁₊₁ ) = P_l+i .

The vector of the tangent to the curve ("the tangent vector") (as demonstrated, for example, in FIG. 2 at Di, D₂, D₃, and D₄) through a control point P, is given by the equation:

_ ( dx dy dz \ V as as as J

In this case, the direction of the tangent vector is known from the measurement of the sensors 110 or tracking coils.

[0031] A cubic interpolating spline is a mathematical function that uses piecewise polynomial functions that pass through control points. In this example, the control points are the portions of the catheter (P₁) to which the sensors 110 are attached. The cubic spline can be expressed as a weighted sum of four basis functions. In this example, the Hermite interpolation basis functions h,(s), which are known in the mathematical arts, are used such that the interpolation function can be expressed as: P(s) = s - h - C = [s^{3 i}]-

[0032] Although the direction vectors D₁ and Di₊i are known from the sensors 110, the lengths of these vectors are not known. The distances between the sensors 110 on the catheter are known, however, and can be used to estimate the lengths of these vectors. It is assumed that a good estimate for the length of D₁ can be given by adjusting D₁ such that the following estimation equation can be used:

where L₁ is the length between the sensors 110 at positions P₁ and P₁₊₁ measured along the catheter. This equation is then solved numerically. By estimating the length of the vectors using this equation, additional accuracy is provided as compared to performing the method by assuming a given length.

[0033] This method was validated by comparing the method against two other methods of estimating the catheter's position. The comparison is shown in FIGS. 5A, 5B, and 5C where the solid line 510 represents the catheter, and the broken lines represent the estimated positions as derived from three different methods. In FIG. 5A, the estimated catheter represented in a broken line 520 was computed using an estimation method called a Cardinal spline. In FIG. 5B, the estimated catheter represented in a broken line 530 was computed using the above described estimation method except that fixed lengths for the tangential vectors were used at each point instead of the above estimation equation for D₁. In FIG. 5C, the estimated catheter represented in an x-designated broken line 540 was computed using the above described estimation method.

[0034] In certain applications, however, it is impractical to place a sensor 110 at the far distal end 205 of the flexible body 100. In such applications, it is possible to extend the above calculation to estimate the position of the distal end 205 that extends beyond the location of the last sensor 110. An example approach to this approximation includes extending the calculation of P, beyond the last sensor. For instance and with reference to FIG. 2, the distance Li between the last sensor 110 at Pi and the distal end 205 of the flexible body 100 is known. Using this distance, therefore, the above calculations can be applied to estimate the position of the distal end 205 of the flexible body 100 by estimating the points between Pi and the distal end 205. Such estimations are generally more accurate for stiffer flexible bodies such as a biopsy catheter as opposed to less stiff flexible bodies that tend to flex more when in use.

[0035] With reference to FIG. 6, a method 600 of sensing a flexible body 100 will be described. A flexible body 100 with a plurality of sensors 110 is inserted 610 into a cavity 123, wherein each sensor 110 is disposed at least adjacent to a portion of the flexible body 100. At least five degrees of freedom are sensed 620 for the portions of the flexible body 100 using the plurality of sensors 110. Then, a position for the flexible body 100 is calculated 630 based at least in part on the sensed at least five degrees of freedom for the portions of the flexible body 100. A cubic spline may be used 640 for calculating the position for the flexible body 100. A distance (shown, for example, as "L₁" in FIG. 2) between the sensors 110 along the flexible body 100 may be used 650 to determine certain of the parameters of the cubic spline. Other mathematical models of the flexible body may also be employed such as a mechanical model of the flexible body that uses a set of partial differential equations taking into account mechanical properties of the flexible body such as stiffness, torquability, and other properties. Using the calculation, then, a visualization of the flexible body 100 may be provided 660.

[0036] According to various approaches, the visualization of the flexible body can be done in any of several modes including as a three-dimensional rendered volume of the flexible body 100 within the cavity 123, as a plurality of two-dimensional projections of the flexible body 100 within the cavity 123, and/or as a surface model of at least a portion of the cavity 123 with a projection of an estimated flexible body 100 trajectory. The imaging device 120 can image at least a portion of the probed cavity 123. By registering the imaged cavity 123 with the sensors 110, the visual output device 125 (for example, a monitor or any other suitable visual display) can show a three dimensional rendered volume or surface model of a patient's anatomy augmented by the estimated catheter placement and/or trajectory. A two dimensional cross section (e.g., by MRI or CT scanning) can also be shown with the catheter projected into the scan plane using an orthogonal projection. A fluoroscopic x-ray image may also be shown with a projection of the catheter spatially registered and overlaid with the x-ray image. An MRI or CT image of the cavity 123 may be done prior to, during, or after placement of the flexible body 100 within the cavity 123. Thus, the visualization of the flexible body 100 may be superimposed over imaging data that may have been acquired prior to the placement of the flexible body 100 within the cavity 123. Alternatively, the imaging data may be acquired while the flexible body 100 is within the cavity 123.

[0037] More specifically, the visualization may be shown on a display 125 that may be provided showing at least a portion of the cavity 123 in which the flexible body 100 can be disposed. For instance, the visualization of the cavity 123 may be at least one of a three dimensional rendered volume and/or a three dimensional surface model as calculated from the positioning information. By another approach, the visualization may be provided as a plurality of two dimensional projections. By yet another approach, the visualization may be of the flexible body 100 as projected into a scan plane of at least a portion of the cavity 123 in which the flexible body 100 can be disposed using an orthogonal projection. By still another approach, the visualization may be of the flexible body 100 as a projected into a plane corresponding to an image of the cavity 123 from an x-ray imaging system. By one other approach, the visualization of the flexible body 100 may be overlaid on a projection image of at least a portion of a cavity in which the flexible body 100 can be disposed using an orthogonal projection or a perspective projection. Those skilled in the art will appreciate that the above-described processes are readily enabled using any of a wide variety of available and/or readily configured platforms, including partially or wholly programmable platforms as are known in the art or dedicated purpose platforms as may be desired for some applications.

[0038] An example visualization as prepared according one approach of the disclosure will now be described. Two sensors were embedded into a catheter with 4 centimeter (about 1.57 inch) spacing between the sensors. Each sensor included three orthogonal micro-coils and was 6.0 millimeters (about 0.24 inch) long with a diameter of 1.2 centimeters (about 0.47 inch). A plastic vascular phantom was filled with water and positioned within a Signa Excite 1.5T MRI scanner (available from GE Healthcare, Milwaukee, Wisconsin, USA). Images of the entire volume of the phantom were acquired. The sensors were then advanced through the water-filled aorta of the phantom. Steady state free precision ("SSFP") images centered at the sensor location were acquired at five frames per second using the "realtime" feature of the MRI scanner. On a separate workstation, software communicating with both the sensor tracking hardware and the MRI scanner performed image reconstruction and visualization, superimposing on the volume rendering of the tubing the catheter trajectory.

[0039] Example images that can be created using the above approach are shown in

FIGS. 7A, 7B, and 1C. FIGS. 7A through 7C show two dimensional slices of a vascular system 710 with a catheter 720 disposed therein. In FIG. 7A, a sagittal cross-section 730 of the vascular system 710 as may be created from MRI scan data includes a projection 740 (shown in a broken line) of the catheter 720 into the two dimensional slice 730. FIG. 7B depicts a coronal cross-section 750 of a portion of the vascular system 710 oriented substantially parallel to the page. A projection 755 (shown in a broken line) of the catheter 720 shows the position and shape of the catheter 720 in the vascular system 710. FIG. 7C depicts an axial cross-section 760 of a portion of the vascular system 710, with this slice oriented substantially perpendicular to the page. A projection 765 (shown in a broken line) of the catheter 720 shows the position and shape of the catheter 720 in the vascular system 710 according to this two dimensional view.

[0040] Additional example images showing a plurality of two dimensional slices or views of a chest with the flexible body projection will be described with reference to FIG. 8. Image 810 is a representation of a two dimensional slice comprising an axial chest view 812 through an atrium 814 and ventricle 816 with a projection of a catheter visualization 818 overlaying the axial chest image 810 and view 812. Image 820 is a representation of a two dimensional slice comprising a sagittal chest view 822 showing the chest 824 and liver 826 with a projection of a catheter visualization 828 overlaying the image 820 and view 822. Image 830 is a representation of a two dimensional slice comprising a coronal chest view 832 showing the atrium 834, ventricle 835, and lungs 836 with a projection of a catheter visualization 838 overlaying the image 830 and view 832. The views 812, 822, and 832 are derived from MRI scanning data.

[0041] Another approach to the system will be described with reference to FIG. 9. In this example, the imaging system is an x-ray imaging device including an x-ray C-arm 910. A patient lays on a patient table 915 with the area of interest disposed relative to the magnetic field generators 920. The magnetic field generators 920 create the magnetic field that generates a measurable current in the sensor coils in the flexible body 100. Thus, when the flexible body 100 enters the area of interest, which is disposed relative to the magnetic field generators 920, the sensors can create the signals necessary to derive the visualization 930 of the flexible body 100 on the display 940. One example of a tracking system that includes the field generators 920 is a component of the Carto System available from BioSense (Haifa, Israel).

[0042] Yet another example approach to the system will be described with reference to

FIG. 10. In this case, an endoscopic camera 1010 includes sensors embedded in the endoscope portion disposed in the patient. A magnetic field generator 1020 is disposed relative to the area of interest in which the endoscope is placed. Thus, when the endoscope enters the area of interest, the sensors in the endoscope can create the signals necessary to derive the visualization 1030 of the endoscope projected into the three dimensional visualization 1035 of the area of interest shown on the display 1040. The display 1040 may also include the endoscopic image 1050 derived from the camera and two dimensional cross sectional images 1060 of the area as may be derived from another imaging method.

[0043] So configured, the real-time images depicted by any of the various example visualizations discussed above may be substituted for or accompanied by the a higher resolution grey scale image data or segmented structures that cannot be acquired in real-time (e.g., coronary arteries and veins in a cardiac application) or image data acquired with a different modality than the one being used during the procedure. Moreover, functional data (e.g. , strain maps, conduction delay data, perfusion data) can be superimposed for navigation. For example, the near real-time images can show the effects of a cardiac intervention and demonstrate when the pre-procedural data is invalidated due to internal or bulk movement or changes due to the intervention, which can signal the need for an update.

[0044] Given the system flexibility as discussed above, various embodiments of a scanning system in accordance with this disclosure may be applied in several settings. Cardiac intervention has been described and, in particular, application to cardiac ablation of arrhythmias is contemplated. For instance, MRI-guided cardiac ablation is contemplated as an application for certain embodiments. Another application includes improving conventional x-ray guided vascular interventions, within cardiac interventions, neurovascular interventions or other x-ray guided procedures. In such applications, the flexible body may be tracked and imaged to assist the medical professional in performing such procedures. A further application includes combining the flexible body visualization with ultrasound images.

[0045] Those skilled in the art will recognize that a wide variety of modifications, alterations, and combinations can be made with respect to the above described embodiments without departing from the spirit and scope of the invention. For instance, other mathematical operations may be employed, including for example finite element modeling or other kinds of physical modeling of the flexible body. Such modifications, alterations, and combinations are to be viewed as being within the ambit of the inventive concept.

Claims

I claim:

1. An apparatus comprising: a flexible body; a plurality of sensors disposed at least adjacent to portions of the flexible body to sense a position and an orientation of the portions of the flexible body with least five degrees of freedom;

- the plurality of sensors configured to be operatively connected to a computing device such that signals from the sensors are received by the computing device such that the computing device may determine a visualization of the flexible body.

2. The apparatus of claim 1 further comprising an imaging device disposed relative to the cavity in which the flexible body can be disposed.

3. The apparatus of claim 2 wherein the imaging output device is one of the group comprising: an MRI device, a CT scanning device, an ultrasound scanner, and an x-ray system.

4. The apparatus of claim 2 further comprising a visual output device operatively coupled to the computing device wherein the visual output device displays images of at least one of the cavity and the flexible body.

5. The apparatus of claim 4 further comprising an operative coupling between the computing device and the imaging device.

6. The apparatus of claim 1 wherein the visualization is at least one taken from the group comprising: a three-dimensional rendered volume of the flexible body within the cavity; a plurality of two-dimensional projections of the flexible body within the cavity; and a surface model of at least a portion of the cavity with a projection of an estimated flexible body trajectory.

7. The apparatus of claim 1 wherein the visualization of the flexible body is derived at least in part by the computing device's applying a cubic spline to information derived from the signals from the sensors.

8. A method comprising: inserting a flexible body with a plurality of sensors, each sensor disposed at least adjacent to a portion of the flexible body, into a cavity; sensing at least five degrees of freedom for portions of the flexible body using the plurality of sensors.

9. The method of claim 8 further comprising calculating a shape for the flexible body based at least in part on the sensed at least five degrees of freedom for the portions of the flexible body.

10. The method of claim 9 further comprising using a cubic spline for calculating the shape for the flexible body based at least in part on the sensed at least five degrees of freedom for the portions of the flexible body.

11. The method of claim 10 further comprising using information about a distance between the sensors to determine parameters of the cubic spline functions.

12. The method of claim 8 further comprising providing a visualization of the flexible body in three dimensions.

13. The method of claim 12 wherein providing the visualization of the flexible body in three dimensions further comprises providing a display showing at least a portion of a cavity in which the flexible body can be disposed as at least one of a group comprising a three dimensional rendered volume and a three dimensional surface model.

14. The method of claim 8 further comprising providing a visualization of the flexible body in a plurality of two dimensional projections.

15. The method of claim 8 further comprising providing a visualization of the flexible body as projected into a scan plane of at least a portion of the a cavity in which the flexible body can be disposed using an orthogonal projection.

16. The method of claim 8 further comprising providing a visualization of the flexible body as a projected into a plane corresponding to an image from an x-ray imaging system.

17. The method of claim 8 further comprising providing a visualization of the flexible body overlaid on a projection image of at least a portion of a cavity in which the flexible body can be disposed using at least one of a group comprising an orthogonal projection or a perspective projection.