Patent Publication Number: US-2012041311-A1

Title: Automated three dimensional acoustic imaging for medical procedure guidance

Description:
This invention pertains to acoustic imaging apparatuses and methods, and more particularly to an acoustic imaging apparatus and method with automatic three dimensional imaging for medical procedure guidance. 
     Acoustic waves (including, specifically, ultrasound) are useful in many scientific or technical fields, such as in medical diagnosis and medical procedures, non-destructive control of mechanical parts and underwater imaging, etc. Acoustic waves allow diagnoses and visualizations which are complementary to optical observations, because acoustic waves can travel in media that are not transparent to electromagnetic waves. 
     In one application, acoustic waves are employed by a medical practitioner in the course of performing a medical procedure. In particular, an acoustic imaging apparatus is employed to provide images of a volume of interest to the medical practitioner to facilitate successful performance of the medical procedure. In particular, acoustic images can be employed by the medical practitioner to guide a procedural device toward a target area where the procedural device is to be employed. 
     One example of such an application is a nerve block procedure. In this case, the medical practitioner guides an anesthesia needle toward a nerve where the blocking agent is to be injected. Other examples include procedures involving a radiofrequency ablation (RFA) needle, a biopsy needle, cyst drainage, catheter placement, line placement, etc. 
     For such acoustic imaging procedural guidance, it is desirable to allow the practitioner to see the procedural device and easily visualize its location, orientation, and trajectory with respect to a target area where the device is to be employed. In conventional arrangements this is not always possible because the procedural device may not be precisely aligned with the scan plane of the acoustic transducer and in this case, it cannot be imaged. Additional complications in visualizing the procedure device can occur when a device like a needle bends or deflects as it is being inserted. 
     Other medical procedures can suffer from similar problems in the employment of acoustic imaging during the procedure. 
     Accordingly, it would be desirable to provide an acoustic imaging apparatus that can more easily allow a medical practitioner to visualize the location, orientation, and trajectory of a procedural device with respect to a target area where the device is to be employed. 
     In one aspect of the invention, an acoustic imaging apparatus comprises: an acoustic signal processor adapted to process an acoustic signal that is scanned to interrogate a volume of interest and is received by an acoustic transducer; a display device for displaying images in response to the processed acoustic signal; a control device that is adapted to allow a user to control at least one operating parameter of the acoustic imaging apparatus; and a processor configured to determine a location of a procedural device within the interrogated volume from the processed acoustic signal, wherein acoustic imaging apparatus is configured to display on the display device a first view of a first plane perpendicular to an orientation of the procedural device. 
     In another aspect of the invention, a method of three dimensional acoustic imaging for medical procedure guidance comprises: receiving an acoustic signal that is scanned to interrogate a volume of interest; determining a location of a procedural device within the interrogated volume from the acoustic signal; and displaying on a display device a first view of a first plane perpendicular to an orientation of the procedural device. 
     In yet another aspect of the invention, a second view of a second plane perpendicular to the first plane is also displayed. 
     In a further aspect of the invention, a third view of a third plane perpendicular to the first and second planes is also displayed. 
    
    
     
         FIG. 1  is a block diagram of an acoustic imaging device. 
         FIG. 2  illustrates an exemplary arrangement of three planes with respect to a procedural device and a body part toward which the procedural device is being directed. 
         FIG. 3A  illustrates a display of the three planes shown in  FIG. 2  according to a first example. 
         FIG. 3B  illustrates a display of the three planes shown in  FIG. 2  according to a second example. 
         FIG. 4  illustrates a flowchart of a method of three dimensional acoustic imaging for medical procedure guidance. 
     
    
    
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided as teaching examples of the invention. 
       FIG. 1  is a high level functional block diagram of an acoustic imaging device  100 . As will be appreciated by those skilled in the art, the various “parts” shown in  FIG. 1  may be physically implemented using a software-controlled microprocessor, hard-wired logic circuits, or a combination thereof. Also, while the parts are functionally segregated in  FIG. 1  for explanation purposes, they may be combined in various ways in any physical implementation. 
     Acoustic imaging device  100  includes an acoustic (e.g., ultrasound) transducer  110 , an acoustic (e.g., ultrasound) signal processor  120 , a display device  130 , a processor  140 , memory  150 , and a control device  160 . 
     In acoustic imaging device  100 , acoustic signal processor  120 , processor  140 , and memory  150  are provided in a common housing  105 . However, display device  130  may be provided in the same housing  105  as acoustic signal processor  120 , processor  140 , and memory  150 . Furthermore, in some embodiments, housing  105  may include all of part of control device  160 . Other configurations are possible. 
     Acoustic transducer  110  is adapted, at a minimum, to receive an acoustic signal. In one embodiment, acoustic transducer  110  is adapted to transmit an acoustic signal and to receive an acoustic “echo” produced by the transmitted acoustic signal. In another embodiment, acoustic transducer  110  receives an acoustic signal that has been transmitted or scanned by a separate device. Beneficially acoustic transducer  110  receives an acoustic signal that interrogates a three-dimensional volume of interest. In one embodiment, acoustic transducer  110  may include a two-dimensional acoustic transducer array that interrogates a three dimensional volume. In another embodiment, acoustic transducer  110  may include a one-dimensional acoustic transducer array that interrogates a scan plane at any one instant, and may be mechanically “wobbled” or electronically steered in a direction perpendicular to the scan plane to interrogate a three-dimensional volume of interest. 
     In one embodiment, acoustic imaging device  100  may be provided without an integral acoustic transducer  110 , and instead may be adapted to operate with one or more varieties of acoustic transducers which may be provided separately. 
     Acoustic (e.g., ultrasound) signal processor  120  processes a received acoustic signal to generate data pertaining to a volume from which the acoustic signal is received. 
     Processor  140  is configured to execute one or more software algorithms in conjunction with memory  150  to provide functionality for acoustic imaging apparatus  100 . In one embodiment, processor executes a software algorithm to provide a graphical user interface to a user via display device  130 . Beneficially, processor  140  includes its own memory (e.g., nonvolatile memory) for storing executable software code that allows it to perform various functions of acoustic imaging apparatus  100 . Alternatively, the executable code may be stored in designated memory locations within memory  150 . Memory  150  also may store data in response to the processor  140 . 
     Control device  160  provides a means for a user to interact with and control acoustic imaging apparatus  100 . 
     Although acoustic imaging device  100  is illustrated in  FIG. 1  as including processor  140  and a separate acoustic signal processor  120 , in general, processor  140  and acoustic signal processor  120  may comprise any combination of hardware, firmware, and software. In particular, in one embodiment the operations of processor  140  and acoustic signal processor  120  may be performed by a single central processing unit (CPU). Many variations are possible consistent with the acoustic imaging device disclosed herein. 
     In one embodiment, processor  140  is configured to execute a software algorithm that provides, in conjunction with display device  130 , a graphical user interface to a user of acoustic imaging apparatus  100 . 
     Input/output port(s)  180  facilitate communications between processor  140  and other devices. Input/output port(s)  180  may include one or more USB ports, Firewire ports, Bluetooth ports, wireless Ethernet ports, custom designed interface ports, etc. In one embodiment, processor  140  receives one or more control signals from control device  160  via an input/output port  180 . 
     Acoustic imaging apparatus  100  will now be explained in terms of an operation thereof. In particular, an exemplary operation of acoustic imaging apparatus  100  in conjunction with a nerve block procedure will now be explained. 
     Initially, a user (e.g., an anesthesiologist or an anesthesiologist&#39;s assistant) adjusts acoustic imaging apparatus  100  to interrogate a volume of interest within the patient&#39;s body. In particular, if a procedural device (e.g., a needle) is to be injected into a patient&#39;s nerve, the user adjusts acoustic transducer  110  to scan an acoustic signal through a volume of the patient&#39;s body that includes the part of the body (e.g., a nerve) where the needle is to be injected. In an embodiment where acoustic transducer  110  includes a 2D transducer array, it outputs 3D image volume data. In an embodiment where acoustic transducer  110  includes a 1D transducer array, at each instant in time acoustic transducer  110  outputs 2D image data representing a thin (e.g., 1 mm thick) slice of the volume of interest. In that case, the 1D array may be scanned or “wobbled” to generate volumetric data for an entire volume of interest in a fixed time interval. 
     Acoustic imaging apparatus  100  processes the received acoustic signal and identifies the procedural device (e.g., a needle) and its current location and orientation. Beneficially, acoustic imaging apparatus  100  may determine the trajectory of the procedural device. 
     In one embodiment, processor  140  executes a feature recognition algorithm to determine the location of the procedural device (e.g., a needle). Beneficially, the entire extent of an area occupied by the procedural device is determined. The feature recognition algorithm may employ one or more known features of the procedural device, including its shape (e.g., linear), its length, its width, etc. These features may be pre-stored in memory  150  of acoustic imaging apparatus  100  and/or may be stored in acoustic imaging apparatus  100  by a user in response to an algorithm executed by processor  140  and control device  160 . In one embodiment at least a portion of the procedural device (e.g., the tip of the needle) may be coated with an ecogenic material that facilitates its recognition. 
     In another embodiment, acoustic imaging apparatus  100  generates and displays one or more images of the scanned volume to a user. The user may then employ control device  160  to manually identify the procedural device within the displayed image(s). For example, the user may manipulate a trackball or mouse to outline or otherwise to demarcate the boundaries of the procedural device in the displayed image(s). Processor  140  receives the user&#39;s input and determines the location of the procedural device. Again, in one embodiment at least a portion of the procedural device (e.g., the tip of the needle) may be coated with an ecogenic material that facilitates its recognition. 
     Then, in one embodiment, acoustic imaging apparatus  100  determines a first plane perpendicular to an orientation of the procedural device. For example, when the procedural device is a needle, then acoustic imaging apparatus  100  may determine the first plane as the plane that is perpendicular to a line extending through the length (long dimension) of the body of the needle at the tip of the needle. In another arrangement, acoustic imaging apparatus  100  may determine the first plane as the plane that is perpendicular to the trajectory of the procedural device at the periphery of the procedural device (e.g., the trajectory at the tip of the needle). 
     Then, in one embodiment, acoustic imaging apparatus  100  determines a second plane that is perpendicular to the first plane. Beneficially, the second plane may be selected such that it extends in parallel to a direction along with a body part of interest (e.g., a nerve) extends. However, other orientations of the second plane are possible. Indeed, in a beneficial embodiment, acoustic imaging apparatus  100  allows a user to select or change the second plane. After the first and second planes are determined, there is only one third plane which is perpendicular to both the first and second planes, and so the third plane can be determined from the first and second planes. 
     Acoustic imaging apparatus  100  then displays some or all of the first, second, and third planes via display device  130 . 
     This can be better understood by reference to  FIG. 2  which illustrates an exemplary arrangement of three planes with respect to a procedural device (e.g., a needle)  10  and a body part (e.g., a nerve)  20  toward which the procedural device is being directed. As seen in  FIG. 2 , a first plane  210  is perpendicular to an orientation of procedural device  10  (e.g., a needle) along the trajectory direction D. Second plane  220  is perpendicular to first plane  210  and extends in parallel to a direction along with nerve  20  extends. Third plane  230  is perpendicular to both the first and second planes  210  and  220  and cuts through a cross section of nerve  20 . 
       FIG. 3A  illustrates a display of the three planes shown in  FIG. 2  according to a first example. The display shown in  FIG. 3A  may be displayed by display device  130  of acoustic imaging apparatus  100 . Image  310  illustrates a two-dimensional view of first plane  210 , image  320  illustrates a two-dimensional view of second plane  220 , and image  330  illustrates a two-dimensional view of third plane  230  of  FIG. 2 . As noted above, in some embodiments acoustic imaging apparatus  100  may display less than all three of these planes. 
     In the example illustrated in  FIG. 3A , the trajectory of needle  10  is offset slightly from nerve  20  so that its current trajectory will cause it to miss nerve  20 . By means of this display, a user can easily recognize the problem and adjust the trajectory of the needle  10  so that it will intercept the nerve  20  at the desired location and angle. 
       FIG. 3B  illustrates a display of the three planes shown in  FIG. 2  according to a second example. As in  FIG. 3A , in  FIG. 3B  image  310  illustrates a two-dimensional view of first plane  210 , image  320  illustrates a two-dimensional view of second plane  220 , and image  330  illustrates a two-dimensional view of third plane  230  of  FIG. 2 . Again, as noted above, in some embodiments acoustic imaging apparatus  100  may display less than all three of these planes. 
     In the example illustrated in  FIG. 3B , the trajectory of needle  10  is such that it will penetrate nerve  20 . By means of this display, a user can easily guide the needle  10  so that it will intercept the nerve  20  at the desired location and angle. 
       FIG. 4  illustrates a flowchart of a method of three dimensional acoustic imaging for medical procedure guidance by an acoustic imaging apparatus, such as acoustic imaging apparatus  100  of  FIG. 1 . 
     In a first step  410 , an acoustic signal that interrogates a volume of interest is received by an acoustic transducer. 
     In a step  420 , it is determined whether or not a user has selected a view to be displayed by the acoustic imaging apparatus. If so, then the process proceeds to step  460  as discussed below. Otherwise, the process proceeds to step  430 . 
     In step  430  the acoustic imaging apparatus determines the location of a procedural device within the interrogated volume of interest. As described above, this can be done automatically using feature recognition and predetermined characteristics of the procedural device which may be stored in the acoustic imaging apparatus or entered into memory in the acoustic imaging apparatus by a user. Alternatively, the location of a procedural device can be determined with user assistance in identifying the procedural device within a displayed image. 
     In a step  440  the acoustic imaging apparatus determines a first plane that is perpendicular to an orientation of the procedural device. For example when the procedural device is a needle, then the acoustic imaging apparatus may determine a plane that is perpendicular to a line extending along the body of the needle at the tip of the needle. In another arrangement, the acoustic imaging apparatus may determine the first plane as the plane that is perpendicular to the trajectory of the procedural device at the periphery of the procedural device. 
     In an optional step  450 , the acoustic imaging apparatus determines second and/or third planes that are perpendicular to the first plane. Beneficially, the second plane may be selected such that it extends in parallel to a direction along with a body part of interest (e.g., a nerve) extends. However, other orientations of the second plane are possible. After the first and second planes are determined, there is only one third plane which is perpendicular to both the first and second planes, and so the third plane can be determined from the first and second planes. In a case where only the first plane is to be displayed, in some embodiments step  450  may be omitted. 
     Where the user has selected a view to be displayed in step  420 , then in a step  460  the acoustic imaging apparatus determines planes to be displayed for the user selected view. In one arrangement, the acoustic imaging apparatus determines the first plane that is perpendicular to an orientation of the procedural device, and the user then selects a desired second plane in step  420  that is perpendicular to the first plane. Alternatively, the user may select any of all of the plane(s) to be displayed. 
     In a step  470 , the acoustic imaging apparatus  100  displays some or all of the first, second, and third planes to a user. 
     The process repeats so that the views of the planes are continuously updated as the procedural device is moved. In one embodiment, the plane views may be updated more than five times per second. In another embodiment, plane views may be updated more than 20 times per second, and beneficially, 30 times per second. 
     While preferred embodiments are disclosed herein, many variations are possible which remain within the concept and scope of the invention. For example, while for ease of explanation the examples described above have focused primarily on the application of regional anesthesiology, the devices and methods disclosed above may be applied to a variety of different contexts and medical procedures, including but not limited to procedures involving vascular access, RF ablation, biopsy procedures, etc. Such variations would become clear to one of ordinary skill in the art after inspection of the specification, drawings and claims herein. The invention therefore is not to be restricted except within the spirit and scope of the appended claims.