Abstract:
An ultrasonic image scanning system for scanning an organic object includes a container for containing a coupling medium for transmitting an ultrasonic signal to the organic object disposed therein whereby a simultaneous multiple direction scanning process may be carried out without physically contacting the organic object. The ultrasonic image scanning system further includes ultrasound transducers for transmitting the ultrasonic signal to the organic object through the coupling medium without asserting an image deforming pressure to the organic object. These transducers distributed substantially around a two-dimensional perimeter of the container and substantially at symmetrical angular positions at approximately equal divisions of 360 degrees over a two-dimensional perimeter of the container. The transducers are further movable over a vertical direction alone sidewalls of the container for a real time three dimensional (3D) image data acquisition. The container further includes sidewalls covered with a baffle layer for reducing an acoustic reverberation.

Description:
This application is a Formal application and claims a Priority Filing Date of Mar. 3, 2005 benefited from a previously filed Application 60/658,889 filed previously by the inventor of this patent application. 

   FIELD OF THE INVENTION 
   This invention generally relates to system and method for carrying out a medical imaging process. More particularly, this invention relates to an ultrasonic imaging apparatus and method for tissue scanning to improve the accuracy and early detection of breast cancer through the image scanning and analyses processes. 
   BACKGROUND OF THE INVENTION 
   Even though an early detection of cancer tissues through image scanning is very desirable to greatly improve the curing rates and also the general technologies for image scanning have made significant advancements, there are still technical difficulties and limitations faced by application of ultrasonic imaging for real time three dimensional (3D) breast scanning. Specifically, the accuracy of measurements is still not reliable due to several factors as will be further discussed below. 
   The mammogram scan is a preferred technique for screening of breast cancer according to the United State governmental health policy. This is mainly because of a relatively low cost and high efficiency to perform the mammogram scans. However, the accuracy of mammogram results is still questionable for women with dense breasts. Conventionally, ultrasound imaging can be used for the breast cancer screening application. U.S. Pat. No. 6,117,080, “Ultrasonic imaging apparatus and method for breast cancer diagnosis with the use of volume rendering”, (the &#39;080 patent) describes one conventional system and method for ultrasound imaging for breast cancer screening. However, conventional ultrasound imaging is merely suitable as a complementary solution for breast cancer screening. This limitation is due to the fact that the result of ultrasound imaging is strongly dependent on the skill of the person conducting the scanning. Therefore, the data and the diagnostic results are not consistently reliable. 
   In a conventional ultrasound imaging for breast cancer screening, as described in the &#39;080 patent, the breast is scanned by sliding the scanhead over the surface of the breast. The scanhead needs to be held in a constant vertical orientation so that the images are acquired from substantially parallel scan planes. Due to the variation in breast tissue thickness across the breast, the scanhead will generally move in a slight arc in the y direction as that shown in  FIG. 1A  according to the &#39;080 patent&#39;s coordinate system, as the scanhead moves across the breast surface. Further, when the clinician is performing the scanning, the process maintains a constant acoustic contact with the breast and that asserts a certain amount of pressure as the scanhead moves. The constant pressure thus slightly compresses the breast tissue beneath the scanhead that leads to degradation of the accuracy and quality of data obtained from the ultrasonic image scans. The &#39;080 patent suggested a scanning of the breast by freehand in which the user has to move the scanhead at a constant rate so that the image planes are separated in the z dimension by a substantially uniform separation which requires a few trials with slow scanhead movement and more rapid scanhead movement so the user can arrive at a scanning speed which will produce the best images. This level of skill requires significant training and practice thus limit the usefulness and acceptance of data obtained from the full breast scanning due to concerns of variations of the scanning process that may heavily depend on the skill level of an image scan operator. 
   The &#39;080 patent further suggested that the arc in the y direction mentioned above can be minimized with the breast flattened out somewhat when the patient is reclining and with a water bag in between the scanhead and the breast tissue which conforms to the contours of the breast and provides good acoustic coupling between a scanning surface and the breast. This method is time consuming and does not give a consistent result and is limiting in other ways. For example, the water bag is suitable only for scanning in a down direction. Therefore, any scanning that is desired in other directions for tomography would need to take place without the water bag. However, because the water bag compresses the breast, the scans that are performed with and without the water bag would not match well. 
   As shown in  FIG. 1B , the &#39;080 patent also suggested an external devices attached to the scanhead to assist in determining scanhead position during a scan. A linear movement-sensing device is mounted on the scanning surface of the scanning aid and the linear sensor in the housing provides signals indicative of the position of the scanhead by means of a cable, which connects to the ultrasound system through a connector. This method again does not addressing the problem of unreliable data obtained in a scan process that requires the scan head to have multi-dimensional movement during the scan. 
   For these reasons, a need still exists for those of ordinary skill in the art to provide an improved method and system for medical imaging. Specifically, it is desirable that the scanning system and methods are carried out without asserting pressure onto the scanning object such that more accurate scan measurements can be obtained. It is further desirable that the scan process is automated and standardized for 3D volume data acquisition such that human operations and potential errors and variations can be minimized. 
   SUMMARY OF THE INVENTION 
   It is an object of the present invention to provide a body object scanning system by applying an ultrasonic scanning device transmitting an ultrasonic waves through a coupling medium and to receive a reflection from the body object for processing and constructing a complete three dimensional image of the body object. The accuracy of the scanning and image construction are improved because there are no direct physical contact with the body object and there is no pressure asserted to the scanning object. 
   In another aspect, the present invention provides an ultrasonic image scanning with automatic scanning process not depending on human skill whereby standardized processes may be implemented to obtain reliable and consistent image scanning data to more accurately process and determine whether there are physical abnormalities of the scanning body object. 
   In yet another aspect, the present invention further provides an ultrasonic imaging scanning system that includes array of ultrasonic sensors whereby physical movement of the sensing system is not required in the 360 degree viewing of the 2D image to further simplify the scanning processes and to improve the accuracy of the scanning results. 
   In yet another aspect, the present invention provides a method of demultiplexing and multiplexing the ultrasonic image scanning processes from different viewing angle by alternately turning on the scanning sensors according to a time demultiplexed sequence and multiplexing the signals measured from the array of sensors for transmitting and processing the multiplexed signals to construct a three dimensional scan image of a body object. Improvement of accuracy is achieved by implementing signal processing algorithms in managing and processing these images from 360 degrees of viewing angles in X-Y dimension and different positions in Z axis. 
   These and other objects and advantages of the present invention will no doubt become obvious to those of ordinary skill in the art after having read the following detailed description of the preferred embodiment, which is illustrated in the various drawing figures. 

   
     BRIEF DESCRIPTION OF FIGURES 
     The present invention is described in detail below with reference to the following Figures. 
       FIGS. 1A and 1B  are perspective views for illustration a prior art scanning system disclosed in a prior art patent. 
       FIG. 2  is a side cross sectional diagram of an ultrasonic scanning system of this invention. 
       FIG. 3  is a functional block diagram for showing the functions carried out by the ultrasonic image scanning system of  FIG. 2 . 
       FIG. 4  is a linear diagram for showing arrangement of MLA elements to channel bus connections. 
       FIG. 5  is a linear diagram for showing arrangement of MLA (Multiplexed Linear Array) elements to channel bus connections. 
       FIG. 6  is a top view of a module covered with baffle. 
       FIG. 7  is a side cross sectional view of container implemented with a stepping motor for vertically moving a scanning sensor along screw rods. 
       FIG. 8  is a top view of slices for showing a composite image of data acquisition during the scan process. 
       FIG. 9  illustrates a calibration pattern. 
       FIG. 10  is a connection diagram for transducers connected to multiplexed for transmitting multiplexed scanning measurement signals to signal processing controller. 
       FIG. 11  is a table for showing an example of probe input to HV Mux output connection implemented in a specific embodiment. 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   Among some embodiments of the present invention are a system and a method capable of performing full breast ultrasound scanning in a relatively inexpensive way. Among some embodiments of the present invention are a 3-dimensional Computer Aided Diagnostic (CAD) software package that detects breast cancer on a screening basis. 
   Medical imaging systems are known. For example, ultrasound imaging is discussed in the &#39;080 patent and in U.S. Pat. No. 6,248,071, which are hereby incorporated by reference in its entirety for all purposes in this patent application. 
   The description and the drawings of the present document describe examples of embodiment(s) of the present invention and also describe some exemplary optional feature(s) and/or alternative embodiment(s). It will be understood that the embodiments described are for the purpose of illustration and are not intended to limit the invention specifically to those embodiments. Rather, the invention is intended to cover all that is included within the spirit and scope of the invention, including alternatives, variations, modifications, equivalents, and the like. 
     FIG. 2  is a schematic block diagram that shows a three-dimensional (3D) full breast scanning image acquisition system as an embodiment of the present invention. A breast  110  is within or at least substantially within a container  120 . The container  120  is filled with liquid, preferably de-bubbled water. An ultrasound probe  125  is disposed in or around the container  120 . The ultrasonic probe  125  is preferably an omni-directional high frequency ultrasound probe. In an exemplary embodiment as shown, the ultrasonic probe  125  is controllable to move in the container, for example, along a vertical direction of the container  120  in a linear up and down direction. The image scanning signals when collected by the probe  125  is then transmitted through a cable  130  to an ultrasound system  140  to carry out image display and data collection and analysis functions. As shown in  FIG. 2 , the ultrasonic probe  125  has a ring shape to move up and down in the container  120  that has a cylindrical shape. 
   In an alternate embodiment, the interior of the container  120  is lined with a plurality of probe elements. With sufficiently number of probe elements, a physical movement of the probe is not necessary, and it is only necessary to switch on the appropriate probe elements. The omni-directional probe, i.e., transducers, preferably is configured with sufficient probe elements, and/or sufficient mobility of the probe elements that the omni-directional probe can acquire the breast image in 360 degrees. 
     FIG. 3  shows the movement of the omni-vision transducer as the ultrasonic probe  125  moves along a vertical direction  115 . The data of scanning image is transmitted through the cable  130  to the ultrasound system  140 . The ultrasound system  140  first carries out a 2D composite image construction, and then the 3D volume rendering process  145  of the three-dimensional image signals followed by performing a full breast CAD process  150  to construct a data array for representing the three dimensional image data. The image scanning results are displayed for diagnosis and as output data for further processes and analyses ( 160 ). 
   In contrast to the conventional freehand and water-bag acoustic scanning approaches, the system as shown above provides an acoustic probe to scan a subject body part from different positions without varying the pressure applied to the subject body part. Furthermore, the probe is now enabled to simultaneously scan the subject body part from non-parallel directions without varying the pressure applied to the subject body part. 
   The water in the container  120  serves the function as an acoustic coupling between the scanning surface and the breast. The water is preferably de-bubbled water. The water is automatically filled and drained from the container via conduits (not shown). The container is kept hygienic with regular disinfection, and the container may be configured to automatically dispense disinfection agents via a conduit. In one embodiment, the movement of the probe is linear only, without rotation, for the sake of simplicity and reliability. In one embodiment, multiple containers and probes are provided to accommodate different sizes of breasts. Preferably, a wire target of known configuration is provided to the end user to place within the container to provide a test pattern so that the system can calibrate itself for the scan converter algorithm. There is a baffle around each transducer to absorb energy, which may cause acoustic reverberation. The system may be configured to have, for example:
         40 mm probe FOV (Field Of View) and 7.5 MHz or higher   128 or 64 elements,   12-20 module per circumference,   20 cm diameter maximum for the acquisition window,   30 cm height,
 
Depending on design choice and depending on application other elements or configuration of similar designs may be also be implemented. The calibration is for the scan converter (R-Theta to Rectangular) algorithm to map all the images from different angles into a circular image. The above numbers represent exemplary implementation of the transducer for each multiplexed module.
       

   Preferably, a scan controller implemented in a computer, e.g., the ultrasound system  140  that includes a scan controller, automatically controls the image scan and data acquisition processes. By properly setting up the control processes, standard types and amount of signals and data are generated and acquired through the image scanning processes. The results of image scanning would then not depend on the level of skill of an image scanner operator and human errors can also be minimized. The speed and cost of carrying out such scanning process is also significantly reduced while more reliable and accurate diagnosis can be provided by consistently using standardized scanning configurations and data analysis processes carried out by highly accurate CAD and image processing systems for detail review by radiologist. The 3D volume image provides a consistent basis for correlation and comparison over a duration of time to track whether there are changes in the scanned image over time. 
   Referring to  FIGS. 2 and 3  again, the ultrasound system  140  may be implemented as a sonogram system that includes a computer-controlled acoustic probe  125 . The acoustic probe  125  scans the subject body part from different positions without varying the pressure applied to the subject body part and preferably from different non-parallel directions without physically touching the subject body part. The de-bubbled water serves the function as coupling medium for transmitting acoustic waves for receiving a scanning image signals back from the subject body part. The scanning image signals are then received and stored based on the positions of the probes and the timing sequence of these signals for rendering a volumetric configuration for the scanned body part by applying appropriate tomography techniques. 
   For actual implementations, the ultrasonic probes may utilize probe technology with fine AWG cable. An HV 20220 or Hitachi 3290 chip or the like may be used. A card-bus connector (68 pin) or the like may be used. Reverb cancellation is preferably included according to any competent technique, for example, any competent conventional reverb cancellation technique. The card-bus connector provides the multi-wire connection in between the probe module. After many single angle probe modules are linked together, it forms a complete 2D circulator probe. The final outputs are brought to the ultrasound system  140  through fine gauge wire cable (e.g. AWG 36). The HV20220 is a high voltage semiconductor multiplex switch. It is used in the single probe module to provide the real time signal routing. When the acoustic wave travels in the water, it may bounce back and forth in the media. The baffle serves the purpose of muting this secondary reflection artifact. The controller may also include a CAD capability for processing three-dimensional data to obtain accurate compound tomographic image. 
   Referring to  FIG. 4  for the configuration of the ultrasonic probes implemented with omni-vision transducer arranged according to the MLA configuration to multiplex the element (&gt;2048) bus to the channel (64) bus. Omni-vision allows the image to be acquired at 360 degree in real time. The MLA provides the signal routing from each individual transducer module to the ultrasound system. In a specific embodiment, there are 2048 elements arranged in a circle, and the HV multiplexer  170  is configured in a way that the output from every sixty-four transducer elements  175  are multiplexed together. In each individual probe module, there is an array of transducers with High Voltage Multiplexer. The array further consists of 64-128 elements of piezo-transducer in one substrate in order to form a focus beam electronically. Each MUX  170  has a separate control bit to turn the HV switch on/off. In the beginning after the system reset all these HV switches, logic high will be shifted into the HV MUX control register to connect the selected element to the output until all 64 elements are turned on, thereafter, it will slide the element until it reaches the end of the first group of 128 elements. Then the transducer element  175  switches to the next group and repeat the same procedures. Referring to  FIG. 5 , each group of transducers supported on a printed circuit board module  180  has a width of 40 mm. The circumference is sixty-four centimeters, i.e., about twenty centimeter diameters, to accommodate sixteen transducer groups supported on the PCB  180 . Each printed circuit board (PCB) module  180  has one hundred and twenty-eight (128) element transducers  175  and HV multiplexer  170 . Inter-module connection can be a flex cable with miniature high-density (&gt;68) card bus connector, or a circular PCB at the bottom, or even a direct connection in between PCB. The Ultrasound system will treat the omni-vision circular probe as a circular MLA with 2048 elements in sixteen (16) groups. 
   Instead of the MLA configuration as described above, an alternate embodiment is to place the 2048 probe elements in a uniform circular arrangement, instead of 16 modules at 16 different angles, for acquiring each image vector in a constant arc distance and reconstruct the image. Additional efforts would be required to build and align these individually placed probe elements. The acoustic energy probably would be concentrated around the center location and may cause the energy intensity to exceed the governmental regulatory limits, e.g., FDA limit. The image density vectors may not uniformly distributed with higher density distributed in the center and much lower density distribute on the edges and that may affect the image quality due to these non-uniform distributions of image density vectors. A further limitation for such configuration is that it cannot compound the image with different speckle distribution since the speckle changes when the image vector is acquired from different angle. However, since this embodiment has the advantage that the configuration appears simple and easy to implement conceptually, it is also included as one of exemplary embodiments in this invention as well. Further investigations and analyses and future technological developments may prove this configuration to be a preferred implementation for particular applications. 
   Another configuration for implementing this invention is to apply one module, or several modules as ultrasonic probes for transmitting ultrasound waves to the scanned body object for receiving the feedback signals to construct a probing image. The motor is applied to drive the probing module or modules to circularly move around the container to acquire the image by collecting data from an image scan with the ultrasound probes placed around three hundred and sixty degrees. Such operation may require longer period of time than the distributed scanning probe configuration as described above. Another concern of high-speed motion of the ultrasound probes in the container is the generation of bubbles that may affect the accuracy of the image scanning. The circular move around the peripheral edge of the container also leads to more complicate cable arrangements. Furthermore, alignment and angular calibration operations of the scanning probes may be necessary when multiple shots in different angles are likely to produce overlapping and compound images. 
     FIG. 6  shows the areas  185  on a PCB other than the transducer  175 . For the purpose of absorbing the acoustic energy to prevent reverb echo, the areas between the transducers are covered with rubber baffle formed with an irregular shape. 
     FIG. 7  illustrates that the whole transducer  125  can be moved up and down with a stepping motor  190  supporting the movements with screw rods  195 . There is preferably no rotation involved. The movements of the transducer  125  can be controlled by a controller included in the ultrasound system  140  implemented with a software that sets a maximum displacement. The maximum displacement may also be based on the length of the subject body image for scanning. When there is no echo according to the reflected signals from the whole image, it is determined that the probe  125  has moved to the end of the tissue volume  110 . The control of the stage motor  190  is through the RS232 or USB port or other similar or equivalent connecting ports from a host personal computer that may be implemented in the ultrasound system  140 . 
   Referring to  FIG. 8  for the divisions as slices  200  of the image data acquired from the transducers distributed over a circumference covering multiple rectangular areas wherein each set of transducers are receiving signals from a different angle. With the acquisition of the same image area from different angles, a composite image is formed as the tomography using image processing techniques similar to MRI image processing. With the motor movement, a volume image can be acquired for the 3D viewing. For a 20 cm diameter image slice, each segment image only needs to process of a length of 10 cm. An array probe can be utilized that is competent for such penetration; for example, a 7.5 MHz linear array transducer module may be used. For the image acquired from each module, the system may perform a scan conversion with different angles and compound the images together. Referring to  FIG. 9 , for the purpose of assuring the images are aligned properly, there is a wire pattern phantom used to calibrate during the image installation. A phantom is any dummy target to simulate the echo reflected from scanned object according to transmission of ultrasound waves. The wire targets are in a fixture for calibration as described above. The purpose of such calibration is mainly for adjusting the geometric error due to the assembly of the 16 probe modules when operated together during the process of a scan conversion. 
   A CAD system and methods are incorporated that characterize the features of the disease and make a best estimation to guide the radiologist in the radiologist&#39;s review. A 3D volume rendering display can be shown on the screen to help the doctor make the doctor&#39;s review. The CAD usually starts from volume rendering the 3D data sets of image, and display the 3D image on the screen. The user can rotate the image in any angle, set the different opacities of the object to identify the suspicious lesion. An advanced CAD algorithm can analyze the image with the cancer features, for instance, the smoothness of the lesion boarder, the shadow behind the lesion, etc. Such kind of information can help, not to replace, the radiologist in making the decision. The surgeon can also have an idea on the 3D tumor before the operation, and the oncologist can trace the tumor size during the treatment. 
   Referring to  FIG. 10  for an implementation of the omni-directional probe HV MUX connection. There are 2048 transducer elements of Omni-vision probe multiplexed in such a way that 64 (or less) consecutive elements are allowed for selection at any one time. Each time an aperture of image scanning is decided, control data are clocked into the shift register of the HV Mux Ics (Hitachi HVmux3290), after transferring 64 bits ‘1’, the system will start to clock in ‘0’ for each line increment until it reaches to the end of the group, and the setting moves to the next group. At the output of the HV Mux, module  1  to  16 , element number  1  and  65  are connected together and become CH0, that is equal to element  1 . Likewise, module  1  to  16 , element number  2  and  66  are connected together and become CH1 and so forth. 
   An example Probe Input to HV Mux output connection for an embodiment is shown in  FIG. 11 . The arrangement of this connection allows the invented probe device to be compatible with the conventional ultrasound system therefore, the scan conversion algorithm and the hardware platform can be adapted for this purpose. 
   Again, it is to be understood that the embodiments described are for the purpose of illustration and are not intended to limit the invention specifically to those embodiments. For example, although the subject body part (e.g., breast) is shown as being immersed into an open container from the top, the container can also be placed onto a subject body part from any other direction. For example, the container can be placed onto a subject body part, and the container can have a conformal lip that conforms to the body part, and a seal can be made against the body part using any competent sealant, and then the container may be filled. Or, the container may be closed on its one otherwise-open end by a thin, flexible membrane, and the membrane can make contact with, and conform to the contours of, the subject body part, perhaps aided by an acoustic couplant to assure good acoustic coupling. Still other variations are within the scope of the present invention.