Method and system for positioning a device in a tubular organ

[0001] The present invention relates to methods of positioning a device in a tubular organ of the body.

[0002] Interventional radiology procedures are becoming increasingly important in the treatment of physiological abnormalities such as lumen stenosis or aneurysm. For example, in order to treat a stenotic coronary artery, it is often required to inflate a balloon, apply an atherectomy or thrombectomy device and place a stent (prosthesis) at a diseased artery site. The intravascular device (balloon, stent, atherectomy or thrombectomy device, for example) is usually mounted onto a guide wire and brought to the vessel to be treated using the guide wire and a catheter. When the catheter tip has reached the arterial region to be treated, the guide wire is extended from the catheter tip and is used to position the device inside the artery. Once the device is positioned within the artery and deployed, repositioning of the device is either impossible or may significantly increase the risk of injury to the artery and can result in total blockage to the treated artery.

[0003] Accurate positioning of the intravascular device at a specific site within an artery is essential for successful treatment. Improper positioning of a stent at the diseased site within the artery, or use of a longer stent than is actually required in order to compensate for inaccurate positioning, may significantly increase the chance for subsequent renarrowing of the artery. Moreover, in atherectomy procedures, inaccurate positioning and deployment of the device in the artery may cause a fatal thrombosis. Therefore, accurate determination of the location of an intravascular device in an artery is vital during any interventional therapeutic procedure.

[0004] The location of a catheter tip or intravascular device with reference to surrounding arterial anatomy is monitored by X-ray fluoroscopy. An angiographer releases a contrast material, such as iodine solution, from the catheter tip. The contrast material is carried from the catheter tip by the blood flow, and an X-ray image of the arterial anatomy in the vicinity of the catheter tip is obtained. Based upon the obtained X-ray image, the catheter is advanced until the desired arterial anatomy is reached. Then, the guide wire is extended from the catheter tip and brought to the diseased artery using fluoroscopy and short injections of contrast material. Usually, in order to treat the artery, the tip of the guide wire should pass through the diseased region to the distal end of the diseased region. Subsequently, an intravascular device is extended over the guide wire and brought to the diseased arterial region. Monitoring the location of the device inside the artery is performed by following the movement of two radio-opaque markers slidable along the guide wire that flank the device. The markers indicate the position of the device in reference to the guide wire in conjunction with short injections of contrast material. Typically, prior art methods require that the device be introduced stepwise into the organ and at each step the device and organ imaged so as to show the instantaneous position of the device relative to the organ. This is repeated as required until the device is positioned at the desired location. Such an approach requires that a contrast material be released into the organ in order for the organ to be imaged together with the device. Since many images may be required, the total amount of contrast material released into the blood may be quite large and harmful to the patient. Moreover, determining the location of the device in an artery in relation to the region to be treated is often inaccurate by this method. The main reason for this may be attributed to the fact that assessment of the morphology and length of disease in the artery is strongly dependent on the perspective from which the artery is viewed.

[0005] WO 96/25881 entitled Method for ultrasound guidance during clinical procedures published Aug. 29, 1996 describes a method using external ultrasound modality to derive angiography 3D reconstruction. External ultrasound modality cannot be applied for some organs, such as coronary arteries, which are an important implementation field for our invention.

[0006] Essentially, this reference describes a method for guiding a tool to reach an organ without intersecting other organs. It does not relate to navigation of a tool located inside a tubular organ to a pre-defined position within the tubular organ.

[0007] WO 01/58359 entitled Ultrasonic Images was published Aug. 16, 2001 i.e. after the international filing date of the present application and discloses an ultrasound imaging system that superimposes sectional views created from volumetric ultrasound data and the location data for an intervention device, such as a catheter. The position of an interventional medical device may be shown, in one or more views, relative to organs and tissues within a body as the interventional device is moved. The interventional device positional data is updated continuously and is superimposed on tissue images that may be updated less frequently, resulting in real-time or near real-time images of the interventional device relative to the tissues. The superimposed images permits medical personnel to perform procedures such as angiograms with minimal or no exposures of patients to x-rays and contrasting dye.

[0008] WO 99/13432 entitled Apparatus and method for determining three-dimensional representations of tortuous vessels published Mar. 18, 1999 discloses a method for three dimensional reconstruction of vessels. It does not teach how to use such a method to navigate a tool located side a tubular organ to a pre-defined position within the tubular organ.

[0009] It would therefore be desirable to provide a method and system for navigating a tool located inside a tubular organ to a predefined position within the tubular organ. It would be particularly advantageous to provide such a method and system where re-imaging of the organ for each incremental advance of the device in the organ is avoided.

[0010] The present invention provides a method and system for positioning a device located inside a tubular organ such as an artery, a blood vessel, or a urethra. The device encompasses, for example, intravascular devices, such as, catheters, balloons, stents, atherectomy and thrombectomy devices.

[0011] In accordance with the invention, positioning of the device in a tubular organ, such as an artery is performed utilizing a three-dimensional computer reconstruction of the organ. In the case of an artery, a three-dimensional reconstruction of the artery may be displayed on a monitor screen from any selected perspective. This allows a diseased artery, for example, to be viewed in the reconstruction from a perspective that is optimal for assessing the morphology and the length of disease in the artery. This in turn permits accurate determination of a location where an intravascular device should be deployed. A three-dimensional reconstruction of an artery may be obtained for example, as disclosed in Applicant's WO 01/85030 entitled System and Method for Three-Dimensional Reconstruction of an Artery published on Nov. 15, 2001. The reconstruction is displayed on a monitor screen, and the location where the device is to be deployed is determined and marked in the reconstruction taking into consideration the abnormality characteristics, the nominal dimensions of the device and its dimensions after deployment.

[0012] The device is mounted on a guide wire and is brought to the desired arterial region by a catheter, as is known in the art. Then, the guide wire is extended from the catheter tip and is used to navigate inside the arterial anatomy until the target artery has been reached.

[0013] In accordance with one embodiment of the invention, the device is inserted into the artery along the guide wire and an X-ray image of the artery, the guide wire and the device is obtained. The location of the device in the artery is determined by following the movement of two radio-opaque markers along the guide wire as the device moves along the guide wire. Then, a two-dimensional projection of the reconstruction, including the region marked for deployment, is obtained from the same perspective as the image, and superimposed onto the image. The superimposition thus shows simultaneously the device and the region of the artery marked in the reconstruction for deployment of the device. The device is advanced in the artery based upon a comparison of the present location of the device in the artery and the location of the marked region. A new image is then obtained of the device, and a superimposition of the reconstruction with the marked arterial region is obtained from the same perspective of the new image. Based upon a comparison of the new location of the device in the artery and the location of the marked region, the device is advanced towards the desired region. This process is repeated until the device appears in an image in the region of the artery marked in the reconstruction for deployment.

[0014] In accordance with another embodiment of the invention, two or more images of the artery are obtained and a three dimensional computer reconstruction of the artery is generated from the images. The location at which the device is to be deployed is then determined and marked in the reconstruction taking into consideration the abnormality characteristics, the nominal dimensions of the device and its dimensions after deployment. Contrast material is released from the catheter tip and an image of the artery to be treated and the device carried over a guide wire is obtained, preferably from the perspective of one of the images used to generate the computer reconstruction. The location of the device in the artery is determined by following the movement of two radio-opaque markers along the guide wire as the device moves along the guide wire. Then the position of the device in the is marked in the reconstruction and compared to the desired location as indicated in the reconstruction. If the device is at the desired location, then the process terminates. Otherwise, the device is advanced in the artery towards the desired location and a new fluoroscopic image of the device and the guide wire is then obtained from the same perspective without releasing contrast material from the catheter tip. The new location of the device in the artery is then determined from the position of the two radio-opaque markers and is then updated in the reconstruction. This process is repeated until the device is positioned in the desired location.

[0015] Thus, in one aspect the invention provides a method for positioning a device located inside a tubular organ, t a desired location inside the tubular organ, the method characterised by:

[0016] a) obtaining a three-dimensional reconstruction of the tubular organ;

[0017] b) marking in the reconstruction the desired location at which the device is to be located;

[0018] c) obtaining a two dimensional X-ray image of the intravascular device from a known perspective; and

[0019] d) using the three-dimensional reconstruction of the tubular organ in combination with the two-dimensional X-ray image of the device to position the device at said desired location inside the tubular organ.

[0020] The invention further provides a system for positioning an intravascular device located inside a tubular organ at a desired location in the tubular organ, the system comprising;

[0021] an X-ray imaging system for imaging the intravascular device from a known perspective so as to produce a two-dimensional X-ray image of the intravascular device,

[0022] a processor coupled to the X-ray imaging system and configured to project a three-dimensional reconstruction of the tubular organ on to a plane from said known perspective of the two-dimensional X-ray image of the intravascular device so as to form superimposition of either the three-dimensional reconstruction on to the two-dimensional X-ray image of the intravascular device or of the two-dimensional X-ray image of the intravascular device on to the three-dimensional reconstruction; and

[0023] a display displaying the superimposition.

[0024] The invention additionally provides a method for positioning a device located inside a tubular organ, at a desired location in the tubular organ, the method comprising:

[0025] a) generating a three-dimensional reconstruction of the tubular organ based upon first and second images of the tabular organ derived from respective first and second different perspectives;

[0026] b) marking the desired location in the reconstruction;

[0027] c) inserting the device into the tubular organ;

[0028] d) obtaining a composite image of the device and the tubular organ, the composite image being obtained from said first perspective;

[0029] e) computing and presenting in the reconstruction the location of the device in the tubular organ;

[0030] f) if the device is not located at the desired location, then:

[0031] i) repositioning the device in the tubular organ;

[0032] ii) obtaining an image of the device from said first perspective; and

[0033] iii) repeating e) and f) as required until the device is located at the desired location.

[0034] In order to understand the invention and to see how it may be carried out in practice, a preferred embodiment will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0035] FIG. 1 shows a system for positioning a device in an artery according to one embodiment of the invention;

[0036] FIG. 2 shows a device being navigated through an arterial system;

[0037] FIG. 3 shows a flow chart diagram for positioning a device in an artery in accordance with one embodiment of the invention; and

[0038] FIG. 4 shows a flow chart diagram for positioning a device in an artery in accordance with another embodiment of the invention.

[0039] Referring first to FIG. 1, shown is a system for positioning a catheter or intravascular device at a desired location within an artery in accordance with one embodiment of the invention. The system comprises a table 102 upon which a patient 103 lies. An X-ray source 104 is located under the table 102 for projecting X-rays through the patient 103 to an X-rays camera 105 located above the table 102, diametrically opposite the X-rays source 104. The X-ray camera 105 generates video signals 108 representing one or more X-ray images of the patient 103. The video signals 108 are stored in a memory 110 of a processor 115. Images captured by the X-ray camera 105 may be viewed on a monitor 120 either in real-time or after being retrieved from the memory 110.

[0040] FIG. 2 shows a catheter 200 the tip 205 of which bas been positioned at an aperture 212 of an artery 210 that is part of an arterial tree 215 of the patient 103. The catheter 200 may be used to deliver an intravascular device 218 mounted on a guide wire 216 to a desired location 219 within the artery 210. The catheter 200 is connected to a reservoir 220 containing a radio-opaque liquid 221 such as an iodine solution that is conducted from the reservoir 220 to the catheter tip 205 and released from the catheter tip 205 as required by depressing a piston 222. When contrast material 221 is released from the catheter tip 205, an image is obtained of the arterial tree in the vicinity 235 of the catheter tip 205 by the X-ray camera 105. Based upon the obtained image, the catheter tip is brought to the arterial system 215, which contains the artery to be treated 210. Then, the guide wire 216 is extended from the catheter tip 205 and brought to the diseased region within an artery 219 using fluoroscopy and short injections of contrast material. After positioning of the guide wire 216 within the artery 210, the device 218 is inserted into the artery 210 towards the desired region to be treated 219 along the guide wire 216.

[0041] FIG. 3 is a flow chart showing the principal steps for navigating the device 218 to the desired location 219 in accordance with one embodiment of the invention. In step 300, two or more images of the artery are obtained. Then, a three-dimensional computer reconstruction of the artery is generated from the images (step 305). Subsequently, taking into consideration the abnormality characteristics (for example, stenosis), the location where the device 218 is to be deployed is determined and marked in the reconstruction, and the nominal dimensions and its dimensions after deployment of the appropriate device are determined (step 310). In step 320, the contrast material 221 is released from the tip 205 of the catheter 200 and an image is obtained showing the position of the device 218 along the guide wire 216 as indicated by two radio-opaque markers flanking the device 218 on the guide wire, and the anatomy of the artery to be treated 208. In step 330, the reconstruction of the artery with the marked region of interest is projected onto a plane from the same perspective as the image, and superimposed onto the image. The superimposition thus shows simultaneously the device 218 and the region 210 of the artery marked in the reconstruction for deployment of the device. Then, the present position of the device 218 is compared to the desired location 219 as indicated in the superimposition (step 340). If the device 218 is at the desired location, then the process terminates (step 350). If no, the device 218 is advanced in the artery towards the desired location step 360). Then, a new image of the device 218 is obtained (step 370) and the process returns to step 340.

[0042] FIG. 4 is a flow chart showing the principal steps for navigating the device 218 to a desired location within the artery 219 in accordance with another embodiment of the invention. In step 400, two or more images of the artery 210 are obtained. Then, a three-dimensional computer reconstruction of the artery is generated from the images (step 405). Then, the location at which the device is to be deployed is determined and marked in the reconstruction based upon the abnormality characteristics, the nominal dimensions of the device and its dimensions after deployment (step 410). In step 420, the contrast material 221 is released from the tip 205 of the catheter 200 and an image of the artery to be treated 208 and the device 218 carried over a guide wire 216 is obtained from the perspective of one of the images used to generate the computer reconstruction. In step 430, the position of the device in the artery is determined from the position of two radio-opaque markers flanking the device on the guide wire, and marked in the reconstruction. Then, the position of the device 218 is in the reconstruction is compared to the desired location 219 as indicated in the reconstruction (step 440). If the device 218 is at the desired location, then the process terminates (step 450). If not, the device 218 is advanced in the artery towards the desired location (460). A new fluoroscopic image of the device 218 and the guide 216 is then obtained from the same perspective without releasing contrast material from the catheter tip (step 470). The new location of the device in the artery is then in determined based upon following the two radio-opaque markers which represent its position along the guide wire and is then updated in the reconstruction and the process returns to step 440.

[0043] It will also be understood that the system according to the invention may be a suitably programmed computer. Likewise, the invention contemplates a computer program being readable by a computer for executing the method of the invention. The invention further contemplates a machine readable memory tangibly embodying a program of instructions executable by the machine for executing the method of the invention.