WO2006137063A2

WO2006137063A2 - Method and apparatus for determining the orienattion of a device within a tubular lumen

Info

Publication number: WO2006137063A2
Application number: PCT/IL2006/000722
Authority: WO
Inventors: Moshe Klaiman; Tsuriel Assis; Michael Zarkh
Original assignee: Paieon Inc.
Priority date: 2005-06-23
Filing date: 2006-06-21
Publication date: 2006-12-28
Also published as: WO2006137063A3; IL169380A0

Abstract

An enhancement for a device intended to be inserted into a tubular lumen projected with an imaging device, the enhancement comprises the twisting of two wires around at least part of the device, the wires being radiopaque in relation to the imaging device. The wires are twisted in parallel to and with a phase difference between each other. The projections of the wires look like two waves symmetric with each other and intersecting ach other at multiple points. The ratio of the following distances: the beginning point of a wire and an intersection point of the two wires; and the distance between two consecutive intersections, determine the radial orientation of the device. The inverse cosine of the ratio of the distance between two consecutive intersection points in an image, and the same distance on a perpendicular projection image, determines the projection angle of the device and hence the lumen.

Description

METHOD AND APPARATUS FOR DETERMINING THE ORIENATTION OF A DEVICE WITHIN A TUBULAR LUMEN

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The present invention relates to medical devices in general and to a method and apparatus for determining the radial orientation and projection angle of a device in particular.

DISCUSSION OF THE RELATED ART

Invasive medical procedures often include the insertion of devices into tubular lumens of a body imaged by an imaging device. The tubular lumen can be a body part such as a blood vessel, the intestines, the urethra or the like, and the device can be any auxiliary, diagnostic or therapeutic device, such as a guide wire, a catheter, a cannula, a stent, an intra vascular ultra sonic transducer, or any other device. Most commonly, devices are carried at the proximal end of a guide wire, which transports them to the required site. Some of these devices are radially asymmetrical, meaning that they have to be positioned at a predetermined radial orientation, and not at any other orientation. For example, a stent intended to be placed at an area of bifurcation, is usually activated along the main artery and one of the bifurcated arteries. Such stent, however, must have an opening around the bifurcation point, the opening directed at the other bifurcated artery, so as to allow uninterrupted blood flow. The need to determine and adjust the radial orientation of a device arises also when a guide wire should bypass an area which carries stenosis on part of the perimeter, so that the lumen is not symmetric at that area and the guide wire should make a detour to pass the stenosis. Most of the procedures are carried out using x-ray imaging devices to localize the medical devices. X-ray imaging devices produce two-dimensional projections of the radiopaque parts of the medical devices, usually radiopaque marker tips carried on the device. The radiopaque markers as seen in the two-dimensional x-ray projections can not provide the orientation of transparent parts of the devices, or of devices with symmetric projection.

Yet another related problem concerns the need to evaluate the foreshortening factor which affects the seeming length of the artery and/or the device, due to the projection angle created between the main direction of the x-ray transducer and the tubular organ, being different than a straight angle. Knowing the projection angle relatively to the artery is crucial for determining the longitudinal position of the device and navigating the device within the arteries. Currently known techniques and devices solve either of these problems, the radial orientation and the foreshortening factor, but not both of them.

There is therefore a need in the art for a method and apparatus that will enable the simultaneous determination of the radial orientation and the foreshortening of an intra-lumen device. The apparatus and method should enable efficient tracking of the required parameters, in order to enable real-time navigation. The method should be applicable to all types of intra lumen devices, including guide wires, catheters, stents, industrial devices and the like. Yet another requirement is that the method would be clear and intuitive to use for the user, usually a physician. Additionally, the apparatus and method should be inexpensive, since many of the devices are implantable and therefore non reusable. Although the need for the apparatus and method is presented for the medical field, it exists in other fields as well, such as an industrial system wherein an object is inserted into a lumen within a body imaged by an imaging device, the object is to be tracked within the lumen, both radially and longitudinally by a projecting imaging device. The method should be applicable to fields other than medical with minimal enhancements. SUMMARY OF THE PRESENT INVENTION

It is an object of the present invention to provide a novel apparatus, methods and enhancement for devices, to enable the determination of radial orientation and projection angle of the device. One aspect of the present invention relates to an enhancement for a device intended to be inserted into a tubular lumen within a body, the body being imaged by an imaging device, the enhancement comprising at least two wires twisted around at least one part of the device, and the wires being radiopaque in relation to the imaging device. The at least two wires can have different radiopaque patterns or different radiopaque degrees. The wires can further be twisted substantially in parallel to each other, with a phase difference. The phase difference can be 180 degrees. Within the enhancement, the at least two wires can encircle the device along its full longitudinal dimension. Alternatively, at least one part of the longitudinal dimension of the device is encircled by at least two wires, and at least one part of the longitudinal dimension of the device is not encircled. In yet another alternative, at least one of the at least two wires comprises an at least one orientation marker. The imaging device can be x-ray, the device can be a guide wire, a stent, a catheter tip, or other devices. The lumen can be a blood vessel, a urethra, an intestine or other tubular lumens.

Another aspect of the invention relates to an apparatus for determining the radial orientation and the projection angle of a device, wherein the device is inserted into a tubular lumen within a body, the body being imaged by an imaging device, the device comprising at least two wires twisted around at least one part of the device with a phase difference of about 180 degrees, the wires having a projection on an image generated by the imaging device, the apparatus comprising the components of: an initial parameters obtaining component for obtaining the parameters of the device; a radial orientation obtaining component for obtaining the radial orientation of the device; and a projection angle obtaining component for obtaining the projection angle of the image. Within the apparatus, the at least two wires can have different radiopaque patterns or different radiopaque degrees. The at least two wires are twisted substantially in 'el to each other, with a phase difference. The phase difference can be about 180 degrees. Within the apparatus, the at least two wires can encircle the device along its full longitudinal dimension. Alternatively, at least one part of the longitudinal dimension of the device is encircled by at least two wires, and at least one part of the longitudinal dimension of the device is not encircled. In yet another alternative, at least one of the at least two wires comprises an at least one orientation marker. Within the apparatus, the imaging device can be an x-ray, the device can be a guide wire, a stent, a catheter tip or other devices. The lumen can be a blood vessel, a urethra an intestine or other tubular lumens Another aspect of the disclosed invention relates to a method for determining the radial orientation of a device, wherein the device is inserted into a tubular lumen of a body, the body being imaged by an imaging device, the device comprising at least two wires twisted in a phase difference of 180 degrees around at least one part of the device, the wires having a projection on an image generated by the imaging device, the projection of the wires having at least two intersection points on the image, and each wire having a beginning point on the image, the method comprising the steps of: determining a first distance measured on the image, between the beginning point of one of the wires and an intersection point between the wires, wherein the intersection point is the closest to the beginning point of the wires; determining a second distance measured on the image, between two consecutive intersection points; and determining the radial orientation of the device in degrees, as the ratio between the first distance and the second distance, multiplied by about 180.

Yet another aspect of the invention relates to a method for determining a projection angle between a device imaged by an imaging device using a projection direction, and the projection direction, wherein the device is inserted into a tubular lumen, the device comprising at least two wires twisted in a phase difference of about 180 degrees around at least one part of the device, the wires having a projection on a first image and on a second image, the first image generated by the imaging device using a perpendicular projection angle, the projection of the wires having at least two intersection points on the first image and on the second image, the method comprising the steps of: determining a first distance measured on the first image between two consecutive intersections; determining a second distance measured on the second image between two consecutive intersections on the second image; and determining the projection angle of the second image as the inverse cosine of the ratio between the second distance and the first distance.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which: Fig. 1 is a schematic illustration of a typical environment in which a preferred embodiment the present invention is used;

Fig. 2A is an illustration of two helical wires, in accordance with the present invention;

Fig. 2B is an illustration of the projection of the wires of Fig. 2A, in accordance with the present invention;

Fig. 3A is an illustration of three different radial orientations of two wires, in accordance with the present invention;

Fig. 3B is a flow chart of the main steps in determining the radial orientation of a device, in accordance with the present invention; Fig. 3C is a flow chart of the main steps in determining the projection angle of a device, in accordance with the present invention;

Fig. 4 demonstrates the considerations in choosing the density of the windings of the wires, in accordance with the present invention;

Fig. 5 is a flow chart of the main steps of the method, in accordance with the present invention; and

Fig. 6 shows a block diagram of the main computational components, in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention overcomes the disadvantages of the prior art by providing a novel method and device for enabling a user inserting a device into a lumen of a body, the body being imaged by an imaging device, such as an x-ray, to determine the radial orientation of the device, as well as the foreshortening of the device which enables the determination of the angle between the device and the main projection direction of the x-ray source. Determining the projection angle is together with the direction of the device enables the location and tracking of the device. The proposed invention comprises two thin helical radiopaque wires twisted around the device, the two wires being twisted at a phase difference of 180°, i.e., at eveiy cross section of the device perpendicularly to the advancement direction of the device within the lumen, the contact points of the wires are at the two endpoints of a diameter of the lumen. The projection of the two wires generally looks like two waves symmetric with respect to each other, so that they intersect every 180°. The distance between two intersection points of the two waves measured on an image, relatively to the distance measured on an image taken with a perpendicular projection direction, enables to determine the angle of the device relatively to the projection angle. The location of the intersection points after rotation, relatively to the location prior to the rotation, provides the radial orientation. The wires should be thin, preferably in the range of 0.05-0.5 mm, so as not to reduce the mobility of the device within the lumen, and are preferably twisted around the device along its entire longitudinal dimension. However, the number of windings depends on a number of factors, such as the diameter of the device and the type and resolution of the imaging device. Fewer helical windings, caused by widely spaced windings will generate a larger and therefore less distinct intersection area, since the helical lines will be closer to each other over a larger area around the intersection point relatively to closely packed windings. However, closely packed windings introduce resolution difficulties. The optimal windings number and density is set according to the imaging device and characteristics of the inserted device. The issue of windings number is further elaborated in association with Fig. 4 below. In another embodiment, the longitudinal dimension of the device is divided into segments, wherein one or more segments are wrapped with wires, and other segments are not. In yet another preferred embodiment, the wires cany orientation markers for easy orientation when only part of the device is seen in an image.

Referring now to Fig. 1 that shows an exemplary environment in which the proposed devices and methods are implemented, The presented example is from the medical domain, but the invention can be used in other environments in which a device is inserted into a lumen, and there exists a need to track the radial as well as the spatial orientation of the device, using two-dimensional projections. In the present non-limiting example, the environment is a cardiologic department of a health care institute. A patient 4, known or suspected to suffer from a coronary arteries problem, or another problem related to blood vessels, goes through a catheterization procedure. The catheter possibly carries a device, such as a stent to be implanted within the patient's artery system. During the catheterization, a catheter carried by a guide wire 8 is inserted into the patient's arteries. An X-ray device 12 is located above the operation bed for projecting patient 4 with x-rays. Device 12 generates video signals or digital images for example in DICOM format representing one or more X-ray images of patient 4. The video signals or digital images are stored or presented in catheterization workstation 15. The signals or images are further transferred to workstation 16 which performs the computational tasks related to the disclosed invention and presents the results, or transfers the results to another device, for example a system controlling the catheterization process (not shown). Workstations 15 or 16 are preferably computing platforms, such as a personal computer, a mainframe computer, or any other type of computing platform that is provisioned with a memory device, a CPU or microprocessor device, and several I/O ports (not shown). Alternatively, workstations 15 or 16 can be a DSP chip, an ASIC device storing the commands and data necessaiy to execute the methods of the present invention, or the like. Workstations 15 or 16 can farther include a storage device (not shown), storing the relevant orientation determination applications. The applications are sets of logically inter-related computer programs and associated data structures that interact to determine the orientation of a device in an x-ray sequence.

Referring now to Fig.2A, which shows a preferred embodiment of the disclosed invention. Fig. 2A shows two helical wires 104 and 108, which are twisted around and attached to a device, such as a guide wire, a catheter, a stent or the like. Helical wires 104 and 108 are twisted around the device in a phase difference of 180°, i.e. the wires intersect every cross section of the device, which is perpendicular to the advancement direction of the device within the lumen, at the end points of a diameter going through the device. In addition, the wires have different radiopaque patterns. For example, helical wire 104 is made of continuous opaque material, such as metal, while helical wire 108 is made of alternating segments of radiopaque and x-ray transparent materials. Another alternative is that he two helicals have different degrees of opacity. It will be appreciated by persons skilled in the art that other methods for telling apart the two wires may exist.

Referring now to Fig. 2B, showing a projection of the wires taken at the direction shown by arrow 112. Wave 124 is the projection of helical wire 104 and wave 128 is the projection of helical wire 108. The difference in the radiopaque structure between wire 104 and wire 108 enables to differentiate between two projections that would have looked identical if the wires were identical, but represent two 180° apart radial orientations of the device. Assuming the helical are 180° apart, the corresponding equations describing the helicals are: HelicaR - {cos,(s),ύn(s), λS) Helical! = (cos(s + π), sin(s + π), λS)

Wherein s is the radial angle, and λ is the longitudinal distance of one winding in the main advancement direction of the device. Perpendicular projection, in parallel to the Y axis of the helicals, provides the curvature equations: HeIiCaIl = (sm(s)_t λS) Helical! = (sm^' (s + π),λS) Referring now to Fig. 3A, showing three perpendicular projections of two helical wires twisted around a device inside a lumen, when the device is in three different radial orientations, 220, 240 and 260. It is well known in the art of image processing how to detect lines, and especially intersection points between lines. Therefore, it can be assumed that the lines representing the helical wires are distinguished from the environment. For clarity purposes, there is no longitudinal difference in the longitudinal position of the device between projections 220, 240 and 260, in Fig. 3A, so that at all projections the wires are bounded between line 200 and line 201 which are the projections of cross sections of the lumen. Considering the cross section projected as line 202, at orientation 220 the wires are maximally distanced, intersecting the cross section at points 212 and 216; at orientation 260, which represents a radial orientation of 90° relatively to orientation 220, the intersection points unite at 236, generating point 241 ; orientation 240 represents an intermediate radial orientation, between orientation 220 and orientation 260. Distances 220, 232 and point 236, represent respectively the distances between intersection points 212 and 216 at orientation 220 the distances between intersection points 224 and 228 at orientation 240, and the zero distance of point 236 at orientation 260.

Referring now to Fig. 3 B showing the main steps in determining the radial orientation of the device. At step 280, the longitudinal distance measured from the beginning point of any of the projections of the wires to the first intersection, for example the distance between line 201 and line 202 in relation to orientation 260 of Fig. 3, referred to as I₁ is obtained. At step 284, the distance between two consecutive intersections, for example distance 250 in relation to orientation 260, referred to as Lptp is obtained. At step 288, the radial orientation is obtained using the formula: RadialOrientationAngle = 180 * L₁ 1 L_plp or: RadialOrientationAngle = 180 * I₁ / L_pφ + 180 .

It will be appreciated by persons skilled in the art that the phase difference between the two helical wires is not limited to 180°, but any predetermined phase difference can provide the same results, as long as the computations take into account the phase difference.

Referring now to Fig. 3C showing the steps in determining the radial orientation of the device which causes the foreshortening caused by the projection angle being non-perpendicular to the lumen. At step 294, the distance between two consecutive intersections in a perpendicular projection, referred to as S tan dordL is obtained. At step 298 the distance between two intersections in the projected image, such as distance 204 on projection 220, referred to as MeasiiredL is obtained. At step 298, the projection angle is determined using the formula: LiimenAngle = cos^"1 (MeasiiredL I S ^'tan dardL) . Referring now to Fig. 4, which shows the considerations in choosing the density of the helical windings along the device. Projections 304 and 308 show the same number of windings, but with different densities. Therefore, along a given length, such as 312, there is exactly one winding on projection 304 and over 1.5 windings on projection 308. Therefore, the resolution in projection 304 is inferior to the resolution provided by projection 308. However, locating the exact intersection point is much easier in projection 304 then in projection 308, as can be seen in comparing area 316 of projection 304 and area 320 of projection 308.

Referring now to Fig. 5 showing the main steps of the method of the disclosed invention. At step 400 the parameters of the device and the helical wires are determined. The parameters must include the diameter of the device, the longitudinal distance along the main advancement axis of the device, between the beginning of two consecutive wrapping of each wire around the device, and the phase difference between the two wires. At step 404 the system is calibrated to obtain the proportions and perspectives of the imaging equipment. An important part of the calibration is obtaining the size between two consecutive intersections, as appears in an image generated by a projection perpendicular to the lumen, At step 308 images presenting projections of the device and the wires are obtained, and analyzed at steps 412 and 416. At step 412 the radial orientation of the device is obtained, as detailed in association with fig. 3B above. At step 416 the projection angle of the lumen, and hence the device is obtained, as detailed in association with Fig. 3 C above.

Referring now to Fig. 6, showing the main computational components in accordance with the disclosed invention. The components comprise an initial parameters obtaining component 500, for obtaining the parameters of the device, such as the perimeter, the distance between two consecutive windings of the helical wires, the characteristics of the imaging device and the like. Calibration component 504 performs the calibration of the system, including generating and analyzing an image taken at a perpendicular angle to a device. Radial orientation obtaining component 508 determines the radial orientation of the device and hence the lumen at a specific image, as detailed in association with Fig. 3B above, and projection angle obtaining component 512 determines the specific imaging angle used to obtain a specific image, as detailed in association with Fig. 3 C above. Since the wires provide a highly distinct shape, their projections can be used in tasks associated with controlling, locating and tracking devices. Therefore, the disclosed invention can be used in conjunction with two-dimensional or three- dimensional models of the relevant body areas, including the lumens. Such model may be used for planning an insertion trajectory for the device, and the disclosed method can be used for controlling the longitudinal and radial orientations of the device. Alternatively, determining the orientation of the device can be used for accurate superposition and registration tasks, by assisting in merging the x-ray image containing the devices with the pre-acquired model.

In addition, the disclosed method can be used for determining the exact calibration, including the scaling parameter (pixel to mm ratio), and the required projection angle for the session.

The disclosed methods are efficient, since the projections of the helical wires and even more so their intersection points, are highly distinct in images, and can be tracked with known image processing techniques with high degree of reliability. Therefore, it is possible to use the method in real time during an operation, but also offline, for subsequent analysis.

The physical devices involved with the invention, i.e., the helical wires are simple and inexpensive and attaching them to a device should not limit the mobility of the device within the lumen. It will be appreciated by persons skilled in the art that other wire structures or number of wires can be used. The helical wires are preferably wrapped all along the device. However, especially for long devices such as guide wires, there can be segments along the device around which wires are twisted, and other segments along which wires re not twisted. In another preferred embodiments, there are orientation markers, preferably at diametrically opposite points of the device, of distinct opacity or shape, which enable a user to project and relate only to a part of the helicals other than their beginning.

Alternatively, other wrapping markings around the device can provide similar results, with minor computational changes. It will also be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined only by the claims which follow.

Claims

CLAIMS What is claimed is:

1. An enhancement for a device intended to be inserted into a tubular lumen within a body, the body being imaged by an imaging device, the enhancement comprising at least two wires twisted around at least one part of the device, the wires being radiopaque in relation to the imaging device.

2. The enhancement of claim 1 wherein the at least two wires have different radiopaque patterns or different radiopaque degrees.

3. The enhancement of claim 1 wherein the at least two wires are twisted substantially in parallel to each other.

4. The enhancement of claim 3 wherein the at least two wires are twisted with a phase difference.

5. The enhancement of claim 4 wherein the phase difference is about 180 degrees.

6. The enhancement of claim 1 wherein the at least two wires encircle the device along its full longitudinal dimension.

7. The enhancement of claim 1 wherein at least one part of the longitudinal dimension of the device is encircled by at least two wires, and at least one part of the longitudinal dimension of the device is not encircled.

8. The enhancement of claim 1 wherein at least one of the at least two wires comprises an at least one orientation marker.

9. The enhancement of claim 1 wherein the imaging device is an x-ray.

10. The enhancement of claim 1 wherein the device is a guide wire.

1 1. The enhancement of claim 1 wherein the device is a stent.

12. The enhancement of claim 1 wherein the device is a catheter tip.

13. The enhancement of claim 1 wherein the tubular lumen is a blood vessel.

14. The enhancement of claim 1 wherein the tubular lumen is a urethra.

15. The enhancement of claim 1 wherein the tubular lumen is an intestine.

16. An apparatus for determining the radial orientation and the projection angle of a device, wherein the device is inserted into a tubular lumen within a body, the body being imaged by an imaging device, the device comprising at least two wires twisted around at least one part of the device with a phase difference of about 180 degrees, the wires having a projection on an image generated by the imaging device, the apparatus comprising the components of: an initial parameters obtaining component for obtaining the parameters of the device; a radial orientation obtaining component for obtaining the radial orientation of the device; and a projection angle obtaining component for obtaining the projection angle of the image.

17. The apparatus of claim 16 wherein the at least two wires have different radiopaque patterns or different radiopaque degrees.

18. The apparatus of claim 16 wherein the at least two wires are twisted substantially in parallel to each other.

19. The apparatus of claim 18 wherein the at least two wires are twisted with a phase difference.

20. The apparatus of claim 19 wherein the phase difference is about 180 degrees.

21. The apparatus of claim 16 wherein the at least two wires encircle the device along its full longitudinal dimension.

22. The apparatus of claim 16 wherein at least one part of the longitudinal dimension of the device is encircled by at least two wires, and at least one part of the longitudinal dimension of the device is not encircled.

23. The apparatus of claim 16 wherein at least one of the at least two wires comprises an at least one orientation marker.

24. The apparatus of claim 16 wherein the imaging device is an x-ray.

25. The apparatus of claim 16 wherein the device is a guide wire.

26. The apparatus of claim 16 wherein the device is a stent.

27. The apparatus of claim 16 wherein the device is a catheter tip.

28. The apparatus of claim 16 wherein the tubular lumen is a blood vessel.

29. The apparatus of claim 16 wherein the tubular lumen is a urethra.

30. The apparatus of claim 16 wherein the tubular lumen is an intestine.

31. A method for determining the radial orientation of a device, wherein the device is inserted into a tubular lumen of a body, the body being imaged by an imaging device, the device comprising at least two wires twisted in a phase difference of 180 degrees around at least one part of the device, the wires having a projection on an image generated by the imaging device, the projection of the wires having at least two intersection points on the image, and each wire having a beginning point on the image, the method comprising the steps of: determining a first distance measured on the image, between the beginning point of one of the wires and an intersection point between the wires, wherein the intersection point is the closest to the beginning point of the wires; determining a second distance measured on the image, between two consecutive intersection points; and determining the radial orientation of the device in degrees, as the ratio between the first distance and the second distance, multiplied by about 180.

32. A method for determining a projection angle between a device imaged by an imaging device using a projection direction, and the projection direction, wherein the device is inserted into a tubular lumen, the device comprising at least two wires twisted in a phase difference of about 180 degrees around at least one part of the device, the wires having a projection on a first image and on a second image, the first image generated by the imaging device using a perpendicular projection angle, the projection of the wires having at least two intersection points on the first image and on the second image, the method comprising the steps of: determining a first distance measured on the first image between two consecutive intersections; determining a second distance measured on the second image between two consecutive intersections on the second image; and determining the projection angle of the second image as the inverse cosine of the ratio between the second distance and the first distance.