Abstract:
The field of the invention relates to medical imaging systems, and more particularly to systems and methods for estimating the size and position of a stent or other medical device within a patient. In one embodiment, a medical imaging system includes an elongated tubular member having distal and proximal ends, configured to be inserted into a vessel of a patient, an imaging device coupled to the distal end of the elongated tubular member, and a console electrically coupled to the imaging device, wherein the console includes a computer-usable medium, electrically coupled to the imaging device, having a sequence of instructions which, when executed by a processor, causes said processor to execute a process including generating an image of the vessel, and overlay one or more shapes onto the image to provide a visual approximation of the size and position of a medical device to be applied within the patient.

Description:
RELATED APPLICATION 
     This is a continuation-in-part of application Ser. No. 11/069,206, filed on Feb. 28, 2005 now U.S. Pat. No. 7,892,177. 
    
    
     FIELD OF THE INVENTION 
     The field of the invention relates to medical imaging systems, and more particularly to systems and methods for estimating the size and position of a medical device to be applied within a patient. 
     BACKGROUND OF THE INVENTION 
     Intraluminal, intracavity, intravascular, and intracardiac treatments and diagnosis of medical conditions utilizing minimally invasive procedures are effective tools in many areas of medical practice. These procedures are typically performed using imaging and treatment catheters that are inserted percutaneously into the body and into an accessible vessel of the vascular system at a site remote from the vessel or organ to be diagnosed and/or treated, such as the femoral artery. The catheter is then advanced through the vessels of the vascular system to the region of the body to be treated. The catheter may be equipped with an imaging device, typically an ultrasound imaging device, which is used to locate and diagnose a diseased portion of the body, such as a stenosed region of an artery. For example, U.S. Pat. No. 5,368,035, issued to Hamm et al., the disclosure of which is incorporated herein by reference, describes a catheter having an intravascular ultrasound imaging transducer. 
       FIG. 1  shows an example of an imaging transducer assembly  1  known in the art. The imaging transducer  1  is typically within the lumen  10  of a guidewire (partially shown), having an outer tubular wall member  5 . To obtain an image of a blood vessel, the imaging transducer assembly  1  may be inserted into the vessel. The transducer assembly  1  may then rotate while simultaneously emitting energy pulses, e.g., ultrasound waves, at portions of the vessel from within the vessel and receiving echo or reflected signals. 
     Turning to  FIG. 2 , it is known in the art that an imaging console  20  having a display screen, a processor and associated graphics hardware (not shown) may be coupled with the imaging transducer assembly  1  to form a medical imaging system  30 . The imaging console  20  processes the received echo signals from the imaging transducer assembly  1  and forms images of the area being imaged. To form the images, the imaging console  20  draws multiple lines, known as “radial lines”, (not shown) on the display screen that each correspond to an angular position of the transducer assembly  1 . The processor of the imaging console  20  assigns brightness values to pixels of the lines based on magnitude levels of the echo signals received from the transducer assembly  1  at the angular positions corresponding to the lines. A drawing that includes a large number of these radial lines results in an image such as an intravascular ultrasound (IVUS) image (not shown). 
     It is further known in the art to continually capture frames of IVUS images while gradually withdrawing the transducer or catheter within a vessel. The resulting stack of frames may be stored and manipulated by the processor, and from these frames, a longitudinal image of the vessel may be generated. In other words, a visualization of the vessel in a plane containing the long axis of the vessel may be rendered, which allows the clinician to assess blockage at different locations along the length of the vessel. For example, U.S. Pat. No. 5,830,145, issued to Tenhoff, the disclosure of which is incorporated herein by reference, describes a system and method for generating longitudinal images of a region of a blood vessel. 
     The resulting longitudinal image may be used to diagnose abnormalities, such as blockage, within the vessel. A typical treatment known in the art for such abnormalities is the use of one or more stents in the region(s) of interest. Often times, determining the proper size (length and diameter) and position of the stent(s) to be applied within the patient is a “trial and error” type process, which may increase procedure time and risk to the patient. Accordingly, an improved system and method for delivering one or more stents would be desirable. 
     SUMMARY OF THE INVENTION 
     The field of the invention relates to medical imaging systems, and more particularly to systems and methods for estimating the size and position of a medical device to be applied within a patient. 
     In one embodiment, a medical imaging system includes an elongated tubular member having distal and proximal ends, configured to be inserted into a vessel of a patient, an imaging device coupled to the distal end of the elongated tubular member and configured to emit one or more energy pulses and receive one or more echo signals, and a console electrically coupled to the imaging device, wherein the console includes a computer-usable medium, electrically coupled to the imaging device, having a sequence of instructions which, when executed by a processor, causes said processor to execute a process including generating an image of the vessel, and providing a graphical representation of a stent or other medical device to be overlaid onto the image. In an exemplary embodiment, different shapes, e.g., a rectangle, may be overlaid onto the image to provide a visual approximation of the size and position of a medical device to be applied within the patient. 
     Other systems, methods, features and advantages of the invention will be or will become apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the accompanying claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to better appreciate how the above-recited and other advantages and objects of the inventions are obtained, a more particular description of the embodiments briefly described above will be rendered by reference to specific embodiments thereof, which are illustrated in the accompanying drawings. It should be noted that the components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views. However, like parts do not always have like reference numerals. Moreover, all illustrations are intended to convey concepts, where relative sizes, shapes and other detailed attributes may be illustrated schematically rather than literally or precisely. 
         FIG. 1  is a cross-sectional side view of an imaging transducer assembly known in the art; 
         FIG. 2  is a block diagram of a medical imaging system known in the art; 
         FIG. 3  depicts a human heart as a potential site for use of the method and apparatus disclosed herein; 
         FIG. 4  depicts an exploded view of a region of the coronary arteries having an IVUS catheter positioned in a region of interest; 
         FIG. 5  depicts a user interface for displaying a longitudinal medical image known in the art; 
         FIG. 6  depicts a user interface for displaying a longitudinal medical image in accordance with a preferred embodiment of the present invention. 
         FIG. 7  depicts a user interface in accordance with another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The methods and systems disclosed herein are applicable to medical imaging, such as ultrasound imaging, of vessels, such as the coronary arteries as depicted in  FIG. 3 , or to any body cavity where the image is to be obtained over a region. With reference to  FIG. 3 , heart  99  includes coronary arteries  98  which follow a tortuous path along the surface of the heart.  FIG. 4  shows an exploded view of curvature  97 , having an IVUS catheter  21  disposed within a region of interest therein. Catheter  21  has distal end  22  and a proximal end (not shown), and is generally designed in accordance with imaging catheters known in the art. The catheter thus includes an intraluminal ultrasound imaging system, such as that shown in FIG.  1 ., capable of obtaining echographic images of the surrounding of catheter tip  22 . The imaging system includes transducer  23  and its associated electronics for displaying an echographic data set, e.g., obtained by scanning transducer  23  over a 360-degree path  24  about distal tip  22  of catheter  21 , or by a sector scan which makes a 60 or 90 degree scan. In an alternative embodiment, transducer  23  is replaced by a phased array as disclosed in Griffith et al., U.S. Pat. No. 4,841,977. Further, other imaging devices may be used, instead of, or in addition to imaging transducers, such as light based apparatuses for obtaining images through optical coherence tomography (OCT). Image acquisition using OCT is described in Huang et al., “Optical Coherence Tomography,” Science, 254, Nov. 22, 1991, pp 1178-1181. A type of OCT imaging device, called an optical coherence domain reflectometer (OCDR) is disclosed in Swanson U.S. Pat. No. 5,321,501, which is incorporated herein by reference. The OCDR is capable of electronically performing two- and three-dimensional image scans over an extended longitudinal or depth range with sharp focus and high resolution and sensitivity over the range. 
     Scanning of the vessel interior is repeated many times during pull-back to obtain a plurality of echographic data sets taken at a sequence of positions  27  within vessel  98 . In one embodiment, each echographic data set obtained during pull-back comprises a transverse or cross-sectional (i.e., r-Θ) image of the vessel at the point of the image, as shown in  FIG. 4 . An example of a cross-sectional image  120  is shown in  FIG. 5 . By “stacking” these images, a longitudinal image  105 , i.e., an image along the longitudinal axis, or z axis, of the vessel may be generated, an example of which is also shown in  FIG. 5 . Such an image is known in the art as a “cut-plane” image. The longitudinal image  105  may be rotated along the z axis to display the image  105  at different angles, Θ, until desired features appear. 
     The longitudinal image  105  is typically generated by a software program, which may reside within the imaging console  20 , shown in  FIG. 2 . The software program displays the image on a display device (not shown) of the imaging console  20 . Turning to  FIG. 6 , the software program may include a user interface  100 . The user interface  100  includes a first window  110 , which displays a longitudinal image  105  of a vessel. As mentioned above, the longitudinal image  105  comprises of a plurality of r-Θ cross-sectional images obtained over time as the catheter  21  is being pulled back. Each of these r-Θ images may be regarded as frames  120 , and the longitudinal image  105  may be displayed as an animation sequence presenting each frame  120  sequentially. These frames  120  are typically generated at a rate of approximately 30 frames/sec, and the catheter  21  is typically pulled back at a speed of approximately one-half mm/sec. Thus, the frames  120  are typically displayed very close together. 
     The user interface  100  may include control elements that allow a user to control the display of the longitudinal image  105 . The control elements may include a playback element  130 , a stop playback element  140 , and an adjust cut-plane position element  125 , which allows a user to rotate the longitudinal image  105  along the z axis. Also included is a frame control  150  element that allows a user to scroll through the frames  120 , backwards and forwards, and select the display of a particular frame  120  within the sequence. The position of the user selected frame  120  within the sequence of the animation is known as the cursor position. The frame control  150  element includes a scrollbar button  155  that indicates the cursor position. The user interface  100  also includes a second window  180 , which displays the frame  120 , or cross-sectional image, corresponding to the cursor position. The control elements may be buttons, keys, sliders, scrollbars, virtual keys on a touch screen, or other user actuatable devices. 
     Generally, a clinician would analyze the image for abnormalities, and if an abnormality requiring one or more stents were discovered in the image, the clinician would visually estimate the length and position of the proper stent to be applied in the region of the abnormality. One approach to facilitate the estimation is to provide a graphical tool that allows a clinician to apply a graphical representation of a stent  160  over the longitudinal image  105  being analyzed. The clinician may be able to graphically adjust the size of the stent  160  to a desired size. One approach may be to drag a mouse pointer over a corner of the stent to adjust the size; however, stent sizes are typically pre-defined and pre-packaged by stent manufacturers, and thus the variety of different sizes may be limited. In such a case, it may be desirable to provide a graphical palette  165 , or a predefined library, of one or more pre-defined stents with their sizes and other characteristics in the user interface  100 . Because the library is predefined with the necessary dimensions and characteristics of each stent, the clinician may simply click on or otherwise select the desired stent within the palette  165  and drag the desired stent to a desired position on the longitudinal image  105  to determine if the selected stent is appropriate. One of ordinary skill in the art may appreciate that additional sizes, characteristics, or devices may be added to the palette  165  or library. 
     After the clinician has established a desired location, or position, on the longitudinal image  105  to place the stent  160 , the clinician may place bookmarks in the image to record the desired location (preferably, one bookmark on each end of the location). The bookmarks essentially record the particular frames  120  that define the desired location within the longitudinal image  105 . In addition, the graphical representation of the stent  160  may be transparent to maintain the visibility of the structure of the image  105 . Providing a clinician a graphical tool to simulate the length and position of a stent within the image  105  facilitates in the selection of the proper stent size and position prior to placing the actual stent, which are costly and permanent implants, within the area of interest. 
       FIG. 7  shows a user interface  100  with a graphical tool for simulating the dimensions and position of a medical device, e.g., stent, within the patient&#39;s body. In this exemplary embodiment, the graphical tool comprises a rectangle  220  overlaid onto the longitudinal image  105  in the first window  110  and a circle  210  overlaid onto the frame  120  in the second window  180 . Together, the rectangle  220  and the circle  210  define a cylinder in three-dimensional space with the rectangle  220  representing a longitudinal cross-section of the cylinder corresponding to the longitudinal image  105  and the circle  210  representing a radial cross-section of the cylinder corresponding to the frame  120 . In this embodiment, the rectangle  220  and the circle  210  may be used to approximate the size and position of a stent to be applied within the patient&#39;s body, in which the stent has a generally cylindrical shape. 
     In an example, the image  105  and the frame  120  may be images of a blood vessel where the stent is to be applied. In this example, the clinician may move the rectangle  220  within the image  105  and adjust the dimensions of the rectangle  220  to visually approximate the desired position and dimensions of the rectangle  220 . The clinician may move the rectangle  220  within the image  105 , e.g., by clicking on the rectangle  220  with a mouse or touch pad to select the rectangle  220  and dragging the rectangle  220  to the desired position within the image  105 . The clinician may adjust the dimensions of the rectangle  220  by clicking on a boundary of the rectangle  220  to select the boundary and dragging the boundary to adjust one or more dimensions of the rectangle  220 . The boundary may darken when selected to visually indicate that the boundary has been selected. For example, the clinician may click on a side boundary of the rectangle  220  and drag the side boundary to adjust the length of the rectangle  220 . 
     In an embodiment, the medical device being applied within the patient&#39;s body may only come in pre-defined dimensions. In this embodiment, the clinician may only adjust the dimensions of the rectangle  220  to one of a set of different dimensions corresponding to the pre-defined dimensions of the medical device. In an embodiment, the user interface may include a graphical palette  265  displaying a set of pre-defined rectangles that the clinician can apply to the image  105 , where each rectangle corresponds to one of the pre-defined dimensions of the medical device. In this embodiment, the clinician can select one of the rectangles in the graphical palette  265  with the selected rectangle being applied to the image  105 . 
     The clinician may also move the circle  210  within the frame  120  and adjust the dimensions of the circle  210  to visually approximate the desired position and dimensions of the circle  210 . The clinician may move the circle  210  within the frame  120 , e.g., by clicking on the circle with a mouse or touch pad to select the circle  210  and dragging the circle to the desired position within the frame  120 . In this embodiment, movements of the circle  210  within the frame  120  causes corresponding movements of the rectangle  220  within the image  105 . For example, moving the circle  210  upward within frame  120  causes the rectangle  220  to correspondingly move upward to track the movements of the circle  210 . Similarly, movements of the rectangle  220  within image  105  causes corresponding movements of the circle  210  within the frame  120 . The clinician may adjust the radius of the circle  210  by clicking on a boundary of the circle  210  to select the boundary and dragging the boundary to adjust the radius of the circle  210  to a desired radius. The boundary may darken when selected to visually indicate that the boundary has been selected. In this embodiment, changes in the dimensions of the circle  210  within frame  120  causes corresponding changes in the dimensions of the rectangle  220  within the image  105 . For example, expanding the radius of the circle  210  within frame  120  causes the height of the rectangle  220  to correspondingly increase. Similarly, changes in the dimensions of the rectangle  220  within image  105  causes corresponding changes in the dimensions of the circle  210  within the frame  120 . 
     Once the dimensions and positions of the circle  210  and the rectangle  220  are chosen, they provide an approximation of the size and position of the medical device to be applied within the patient&#39;s body. Although a circle and a rectangle were used in the exemplary embodiment, other shapes may also be used depending on the shape of the medical device to be applied within the patient. Also, different frames  120  may be displayed in the second window  180 , e.g., by moving the scrollbar button  155 , in which the position of the scrollbar button  155  corresponds to the frame currently displayed in the window  180 . In this embodiment, the circle  210  corresponds to the frame  120  currently displayed in the window  180 . Displaying different frames  120  in the second window  180  allows the clinician to visualize how the circle  210  fits within different radial cross-sectional images of the patient. 
     In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. For example, this invention is particularly suited for applications involving stents, but can be applicable for other medical devices. As a further example, each feature of one embodiment can be mixed and matched with other features shown in other embodiments. Additionally and obviously, features may be added or subtracted as desired. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.