Abstract:
A method and system are provided for displaying a measurement associated with an anatomical feature. The method includes determining, from ultrasound data, a measurement of such feature and assigning a color based on a comparison between the measurement and reference data of such feature. The feature may be, for example, an artery and the measurement the intima media thickness of the artery. In such example, the method and apparatus display vessel wall thickness from ultrasound imaging data and includes determining from the ultrasound imaging data, intima media thickness along the vessel wall and assigning a color based on the intima media thickness determined and a reference intima media thickness.

Description:
TECHNICAL FIELD  
       [0001]     This invention relates generally to displaying a measurement associated with an anatomical feature, and more particularly to ultrasound imaging used to display a measurement associated with an anatomical feature such as, for example, vessel wall thickness.  
       BACKGROUND  
       [0002]     As is known in the art, Intima Media Thickness (IMT) is a measurement of the distance between the lumen-intima (LI) boundary and the media-adventia (MA) boundary of a vessel. Measurement of IMT is an emerging application that is growing in interest and importance to the clinical community. It has been demonstrated as an independent predictor of transient cerebral ischemia, stroke, and coronary events. However, most ultrasound systems that provide an IMT measurement simply provide a measurement, or at best feed that measurement back into risk assessment. So even if an automated measurement is supplied instead of a manual measurement, the resulting numbers must be interpreted in order to perform an assessment of the patient&#39;s vascular health.  
         [0003]     One technique used to measure IMT is with ultrasound imaging. More particularly, ultrasound imaging data is used to ascertain the LI and MA boundaries (either automatically detected or manually placed), calculate the thickness, and then provide one or more of the following results: the average IMT; the maximum IMT; a graph of the patient&#39;s average and/or maximum IMT vs. general population statistics. A risk assessment is made by replacing the patient&#39;s chronological age with a vascular age based on how the patient&#39;s average IMT relates to the general population statistics. One problem with such method is that all of the results are numeric values that require interpretation. There is no quick visual reference that allows you to easily assess vascular health.  
       SUMMARY  
       [0004]     In accordance with the present invention, a method and system are provided for displaying a measurement associated with an anatomical feature. The method includes determining, from ultrasound data, a measurement of such feature and assigning a color based on a comparison between the measurement and reference data of such feature.  
         [0005]     In one embodiment, the reference data includes population statistics.  
         [0006]     In one embodiment, the reference data is a function of prior determined data of the feature.  
         [0007]     In accordance with another embodiment, a method is provided for displaying vessel wall thickness from ultrasound imaging data. The method includes determining from the ultrasound imaging data IMT along the vessel wall and assigning a color is based on the IMT measurement and a reference IMT.  
         [0008]     In one embodiment the reference IMT is a function of population statistics.  
         [0009]     In one embodiment, a single color is assigned to the entire vessel wall based on the average IMT determination and the reference IMT.  
         [0010]     In one embodiment, a single color is assigned to the entire vessel wall based on the maximum determined IMT and the reference IMT.  
         [0011]     In one embodiment the IMT is determined at each of a plurality of different locations along the vessel wall. The method includes assigning at each one of the different locations along the vessel wall a color based on the IMT determination at each one of the different locations.  
         [0012]     In one embodiment the reference IMT is a function of a prior IMT determination.  
         [0013]     In one embodiment the reference IMT is a function of a prior IMT determination and the time duration between the determined IMT and the prior IMT determination.  
         [0014]     In one embodiment a method is provided for displaying vessel wall thickness from ultrasound imaging data. The method includes generating LI and MA boundaries for the vessel wall; using such ultrasound imaging data; measuring from the generated LI and MA boundaries an IMT along the vessel wall; and assigning a color based on the IMT measurement and the reference IMT.  
         [0015]     In one embodiment, a method is provided for displaying vessel wall thickness from ultrasound imaging data taken on a patient. The method includes obtaining demographic information of the patient; obtaining an ultrasound image of the vessel of the patient; determining from the obtained image the IMT of the vessel; comparing the determined IMT with data of IMT for people having substantially similar demographics as the obtained patient demographic information; selecting a color to apply to for displaying the vessel based on the comparison; and generating an image of the patient&#39;s vessel with a wall of the vessel image having the selected color.  
         [0016]     In one embodiment, an ultrasound system is provided for displaying vessel wall thickness from ultrasound imaging data taken on a patient. The system includes a transducer for obtaining an ultrasound image of the vessel of the patient. The system includes a processor for: determining from the obtained image the IMT of the vessel; comparing the determined IMT with data of IMT for people having substantially similar demographics as the obtained patient demographic information; selecting a color to apply to for displaying a wall of the vessel based on the comparison; and generating an image of the patient&#39;s vessel; with the wall of the vessel image having the selected color.  
         [0017]     Thus, in accordance with the invention, a method and system are provided for generating LI and MA boundaries for the vessel wall. This may be an automated procedure or a manual procedure. Next the method measures the IMT at each location along the vessel wall. At each location along the vessel wall, a color is assigned based on how the local IMT measurement relates to the general population statistics. For example, the process might assign a green color if the IMT measurement is normal, yellow if it is high, and red if it is very high. Next, the method displays the IMT measurement and then fills in the vessel wall by alpha-blending the color assigned at each location in the image. This will highlight the vessel wall and display a color at each location that clearly identifies if the IMT measurement at that location is normal, high, or very high.  
         [0018]     This invention thereby provides a technique for displaying a vessel wall thickness measurement such as IMT to provide a clear visual indication of the patient&#39;s vascular health. It does this by shading the area in the image representing the vessel wall thickness using a color map that relates the thickness represented in the image with data from the general population. This gives immediate visual feedback of how the patient&#39;s vessel wall thickness relates to the general population. Thus, in addition to providing all of the same measurements as the old methods, this invention allows a quick visual assessment of this particular risk factor. Areas of the vessel wall that have more thickening than is expected in the general population are clearly identified by color on the image, side by side with the actual numeric measurement of IMT.  
         [0019]     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0020]      FIG. 1  is a sketch of ultrasound apparatus for displaying vessel wall thickness from ultrasound imaging data taken on a patient according to the invention;  
         [0021]      FIG. 2  is a block diagram of processing equipment used to the apparatus of  FIG. 1  to display vessel wall thickness from ultrasound imaging data taken on a patient according to the invention;  
         [0022]      FIG. 3  is a flow diagram of a process used by the apparatus of  FIG. 1  for displaying vessel wall thickness from ultrasound imaging data taken on a patient according to the invention;  
         [0023]      FIG. 4  is a sketch of an image of a segment of the vessel of the patient obtained with the apparatus of  FIG. 1  prior to having a wall thereof displayed with a color selected in accordance with the invention;  
         [0024]      FIG. 4A  is a sketch of an image of a segment of the vessel of the patient obtained with the apparatus of  FIG. 1  after having a wall thereof displayed with a color selected in accordance with the invention; and  
         [0025]      FIG. 4B  is a sketch of an image of a segment of the vessel of a different patient obtained with the apparatus of  FIG. 1  after having a wall thereof displayed with a color selected in accordance with the invention. 
     
    
       [0026]     Like reference symbols in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0027]      FIG. 1  shows an imaging system  10 , here an ultrasound imaging system for medical diagnostics. The system  10  includes a positionable, here handheld, image processing ultrasound device, here a transducer  12  and a multi-use display device, or operator interface or workstation  14 . The handheld transducer  12  obtains ultrasound data and formats the ultrasound data for transmission to the workstation  14 , here via a cable  16 .  
         [0028]     The handheld transducer  12  includes conventional ultrasound circuitry, not shown. Thus, the ultrasound circuitry includes, in the frontal portion thereof an array of ultrasonic elements  19 ,  FIG. 2 , which transmit and receive ultrasonic energy for imaging an anatomical feature, here for example, a blood vessel of patient  15 , here the carotid artery, not shown, of the patient  15 . The elements  19  in the frontal portion fed to a display  22  of the workstation  14  ( FIG. 1 ) serially through: a processor  21 , shown in  FIG. 2 . Thus, the processor  21  includes beamforming network  24  fed by the transducer  12 , an echo processor  26 , a scan converter  28 , and an image processor  31  in a conventional manner. The beamforming network  24 , echo processor  26 , scan converter  28 , image processor  31  and display  22  are controlled by a central processing unit (CPU)  32  coupled to a random access memory RAM  37 . The CPU  32  operates in accordance with program instructions stored in a ROM  34 , or in RAM  37 , or in flash memory not shown, or on a hard drive device, not shown. A memory  36 , here an erasable, or other type of programmable semiconductor memory, here a read only memory (ROM) is provided for storing a computer, here microprocessor, executable program, for operating the CPU  32 . Further, the RAM  37  stores, after being read from the hard drive, not shown, a table of reference data, to be described in more detail.  
         [0029]     Thus, the ultrasound processor  21  ( FIG. 2 ) scan converts data associated with the radial scan pattern to generate ultrasound image data in a video format (e.g. Cartesian coordinate format). Thus, as noted briefly above, the processor  21  includes the array of transmitting/receiving elements  19 , here an array of piezoelectric crystals that deliver ultrasonic energy into a patient and receive ultrasonic echoes from the patient. Electrical signals representative of the echoes produced by the transducer  12  are delivered to the beamforming network  24  where they are selectively combined to produce an indication of the echo intensity along a particular direction or beam in the patient. The data produced by the beamforming network  24  is fed to the echo processor  26  that calculates echo intensity at each position along a beam and may calculate a Doppler shift of the echoes received along a particular beam. Data from the echo processor  26  is fed to a scan converter  28  that converts the data into a form that can be readily displayed on a video monitor  22 .  
         [0030]     The data produced by the scan converter  28  is stored in an the RAM  37  where an additional processing, such as adding color in a manner to be described, is performed prior to displaying the images on the video monitor, here display  22 . Controlling the operation of the above-referenced parts are one or more central processing units, here collectively indicated by the CPU  32 .  
         [0031]     Referring now to  FIG. 3 , a flow diagram of the process used to display vessel wall thickness of a blood vessel, here the carotid artery, of the patient  15 ,  FIG. 1 , is shown. The process is stored as a computer program in stored in a ROM  34 , or in RAM  37 . The process begins by the sonographer, not shown, inputting onto one of the memories  36  or  37 ,  FIG. 2 , demographic data, i.e., age and sex, of the patient  15  ( FIG. 1 ), Step  300 . Next, an ultrasound image of a desired region of the patient&#39;s vessel is obtained, an exemplary image of such desired region of the carotid artery  100  being shown in  FIG. 4 , Step  302 . Note the walls of the artery  100  are indicated by the numerical designation  100   a,    100   b,  and the channel for blood flow is designated by numerical designation  100   c.  The ultrasound data of such desired region of the carotid artery  100  is stored in RAM  37 .  
         [0032]     Next, referring again to  FIG. 3 , the processor  21  uses the ultrasound data stored in RAM  37  and processes such data to generate LI and MA boundaries for the vessel wall and from the generated LI and MA boundaries determines an IMT at one selected location along the vessel wall, for example location  104   a  along wall  100   a,    FIG. 4 , Step  304 .  FIG. 3 .  
         [0033]     Next, the process compares the IMT obtained for location  104   a  with data with reference data, here, in this example, data from a segment of the population statistics  306  stored, as noted above, in one of the memories  36 ,  37 , having the same or similar demographic data, e.g., age and sex, as the patient being examined, Step  308 .  
         [0034]     The processor  21  next selects a color to apply to location  104   a  based on how the obtained IMT compares with the segment of the population statistics. For example, here the color red is selected if the IMT is much larger than the IMT of the population segment, the color green is selected if the IMT is lower than the IMT of the population segment, and the color yellow is selected if the IMT moderately above average for the IMT of the population segment, Step  310 .  
         [0035]     The process then determines if all locations  104   b  through  104   n  have been compared, Step  312 . If not, the process selects the next location, for example, location  104   b.  When all locations  104   a  through  104   n  have been compared, the processor generates a new ultrasound image on display  22 ,  FIG. 1 , by applying the selected colors as an overlay to each of the vessel locations in the original ultrasound image, Step  304 , as shown in  FIGS. 4A and 4B , where in this example,  FIG. 4A  shows the color  106   r  of red along wall  100   a  and  FIG. 4B  shows the color  106   g  of green along wall  100   a.  It is noted that the sonographer or radiologist can easily detect by the colors displayed on display  22  that the patient having the sonogram in  FIG. 4B  has an abnormally high IMT whereas the patent with the having the sonogram in  FIG. 4A  has an acceptable IMT.  
         [0036]     Embodiments of the present invention can also be applied to anatomical features other than the IMT. For example, the embodiments of the invention can be applied to the measurement of the length of a fetal femur, the circumference of a fetal abdomen or head, or the fetal biparietal diameter. The invention can also be applied to a measurement of the length, area, or volume of a kidney, tumor, or other anatomical feature. Other embodiments can be applied to a change or a periodic change in an area or volume, such as the cardiac left ventricular ejection fraction, or to a quantity derived from such a measurement, such as the cardiac output. In each case, a color overlay can be applied to the region of the anatomical feature, or to the numerical display of the measurement, or to an artificial rendering of the object, such as colorizing the vessel wall that is displayed with a “vessel fly-through” display. The color can be based on population statistics, the subject&#39;s age, weight, or other clinical risk factors (such as diabetes or history of smoking), one or more previous measurements, or other pre-determined criteria. Thus, the color may indicate that the size of an object is better, similar, or worse than at the time of a previous measurement. Alternatively, the color may indicate that the size of the object is normal, abnormal, healthy, diseased, or at elevated risk of future disease.  
         [0037]     In addition to quickly conveying information to the clinician, the colorization may help to improve communication with the patient. Comments such as “the red region indicates diseased or ‘at risk’ endothelium”, or “the green on the tumor indicates that it is shrinking in size from your previous exam” may help patients to better understand the clinical implications of the pictures that they are shown. This may help improve patient compliance with proposed treatment.  
         [0038]     A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, a single color may be assigned to the entire vessel wall based on the average IMT determination and the reference IMT. Alternatively, a single color is assigned to the entire vessel wall based on the maximum determined IMT and the reference IMT. Further, the reference data may be a function of a prior IMT determination on the same patient to assess changes in the patients IMT over time. Thus, in such embodiment the reference IMT is a function of a prior IMT determination and the time duration between the current IMT determination and the prior IMT determination. Further, the measurement may be a distance, an area, a volume, a displacement, a velocity, a strain, a strain rate, or an accelerate rate. Still further, the measurement may be obtained manually (with a user interface) or automatically, or a combination thereof. Also, the database may have data manually enter by a physician of the thresholds that are of clinical interest to him, based on his own judgment and may represent healthy/deceased boundaries, for example. Accordingly, other embodiments are within the scope of the following claims.