Abstract:
An ultrasound diagnostic apparatus to improve picture quality of images by automatically adjusting image parameters, and a control method thereof are provided. The ultrasound diagnostic apparatus includes an image signal processor to perform envelope detection processing on ultrasound image data, and an image parameter processor to calculate a Time Gain Compensation (TGC) parameter from the envelope detection processed ultrasound image data, adjust the envelope detection processed ultrasound image data based on the TGC parameter, and calculate a Dynamic Range (DR) parameter from the envelope detection processed ultrasound image data adjusted based on the TGC parameter to apply the DR parameter to the envelope detection processed ultrasound image data.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from Korean Patent Application No. 10-2010-0117786, filed on Nov. 25, 2010 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Apparatuses and methods consistent with exemplary embodiments relate to an ultrasound diagnostic apparatus, and a control method thereof. 
     2. Description of the Related Art 
     An ultrasound diagnostic apparatus is one of important diagnostic systems which have a wide variety of applications. Especially, ultrasound systems are used extensively in the field of medicine due to the noninvasive and nondestructive nature with respect to an object. Recent high-performance ultrasound systems are used to generate two- or three-dimensional images of the interior of an object. 
     To observe an object, it is necessary to acquire an optimal ultrasound image which shows the object clearly. To this end, an ultrasound system adjusts image parameters such as gain, Dynamic Range (DR), and Time Gain Compensation (TGC) according to a setting value input by a user to adjust the brightness, resolution, contrast, etc. of an ultrasound image. 
     In a conventional ultrasound diagnostic apparatus, a user must directly fine-tune image parameters minutely in order to acquire an optimal ultrasound image, thereby causing fatigue and increasing time to acquire an ultrasound image due to a complicated control procedure. 
     SUMMARY 
     Exemplary embodiments provide an ultrasound diagnostic apparatus to improve picture quality of images by automatically adjusting image parameters, and a control method thereof. 
     In accordance with an aspect of an exemplary embodiment, there is provided an ultrasound diagnostic apparatus including an image signal processor to perform envelope detection processing upon ultrasound image data, and an image parameter processor to calculate a Time Gain Compensation (TGC) parameter from the envelope detection processed ultrasound image data, adjust the envelope detection processed ultrasound image data based on the TGC parameter, and calculate a Dynamic Range (DR) parameter from the envelope detection processed ultrasound image data adjusted based on the TGC parameter to apply the DR parameter to the envelope detection processed ultrasound image data. 
     The image parameter processor may include a TGC processor to calculate the TGC parameter, and the TGC processor may calculate a TGC curve for the envelope detection processed ultrasound image data and apply the TGC curve to the envelope detection processed ultrasound image data. 
     The TGC processor may calculate the TGC curve for the envelope detection processed ultrasound image data by accumulating the envelope detection processed ultrasound image data, dividing the accumulated envelope detection processed ultrasound image data into a prescribed number of blocks, performing linear fitting with respect to each block, and calculating a curve corresponding to an implicit function of a linear fitting curve derived by performing the linear fitting. 
     The TGC processor may adjust the linear fitting curve using a mean value of a discontinuous curve region so as to eliminate the discontinuous curve region when the discontinuous curve region is present on the linear fitting curve. 
     The TGC processor may determine the TGC curve by calculating a curve corresponding to an implicit function of the adjusted linear fitting curve. 
     The TGC processor may determine that the envelope detection processed ultrasound image data is noise if the envelope detection processed ultrasound image data to which the TGC curve is applied is less than a first reference after applying the TGC curve to the envelope detection processed ultrasound image data. 
     The TGC processor may lower a size of the envelope detection processed ultrasound image data by dividing the envelope detection processed ultrasound image data judged to be noise by a second reference value when the envelope detection processed ultrasound image data is judged to be noise. 
     The second reference value may be a TGC curve value multiplied by the envelope detection processed ultrasound image data judged to be noise or an arbitrary value predetermined during design. 
     The image parameter processor may include a DR processor to calculate a DR parameter, and the DR processor may calculate the DR parameter using a maximum value, a mean value, and a median value of the envelope detection processed ultrasound image data adjusted based on the TGC parameter. 
     The DR processor may determine a value obtained by subtracting a prescribed value from the maximum value of the envelope detection processed ultrasound image data as a high value and determine a value obtained by subtracting a prescribed value from the mean value of the envelope detection processed ultrasound image data as a low value. 
     The DR processor may adjust the DR parameter according to a difference between a mean value and a median value of the envelope detection processed ultrasound image data. 
     The DR processor may adjust the DR parameter by increasing the high value as the difference between the mean value and the median value is increased. 
     In accordance with an aspect of another exemplary embodiment, there is provided a control method of an ultrasound diagnostic apparatus including performing envelope detection processing upon ultrasound image data, extracting a TGC parameter from the envelope detection processed ultrasound image data, adjusting the envelope detection processed ultrasound image data based on the TGC parameter, and calculating a DR parameter from the envelope detection processed ultrasound image data adjusted based on the TGC parameter to apply the DR parameter to the envelope detection processed ultrasound image data. 
     The extraction of a TGC parameter may include accumulating the envelope detection processed ultrasound image data, dividing the accumulated envelope detection processed ultrasound image data into a prescribed number of blocks, performing linear fitting with respect to each block, and calculating a TGC curve corresponding to an implicit function of a linear fitting curve derived by performing the linear fitting. 
     The adjustment of the envelope detection processed ultrasound image data based on the TGC parameter may include applying the TGC curve to the envelope detection processed ultrasound image data. 
     The control method may further include determining that the envelope detection processed ultrasound image data is noise if the envelope detection processed ultrasound image data to which the TGC curve is applied is less than a first reference value after applying the TGC curve to the envelope detection processed ultrasound image data. 
     The control method may further include lowering a size of the envelope detection processed ultrasound image data by dividing the envelope detection processed ultrasound image data judged to be noise by a second reference value when the envelope detection processed ultrasound image data is judged to be noise. 
     The control method may further include adjusting the linear fitting curve using a mean value of a discontinuous curve region so as to eliminate the discontinuous curve region when the discontinuous curve region is present on the linear fitting curve. 
     The calculation of a DR parameter from the envelope detection processed ultrasound image data may include calculating the DR parameter using a maximum value, a mean value, and a median value of the envelope detection processed ultrasound image data adjusted based on the TGC parameter. 
     The calculation of a DR parameter may include determining a value obtained by subtracting a prescribed value from the maximum value of the envelope detection processed ultrasound image data as a high value and determining a value obtained by subtracting a prescribed value from the mean value of the envelope detection processed ultrasound image data as a low value. 
     The control method may further include adjusting the calculated DR parameter according to a difference between a mean value and a median value of the envelope detection processed ultrasound image data. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects will become apparent and more readily appreciated from the following description of the exemplary embodiments, taken in conjunction with the accompanying drawings of which: 
         FIG. 1  is a block diagram of an ultrasound diagnostic apparatus according to an exemplary embodiment; 
         FIG. 2  is a block diagram of an image parameter processor of an ultrasound diagnostic apparatus according to an exemplary embodiment; 
         FIG. 3  is a graph to describe a TGC parameter extraction method in an ultrasound diagnostic apparatus according to an exemplary embodiment; 
         FIG. 4  is a graph to describe a method of eliminating a discontinuous region of a linear fitting curve of the graph of  FIG. 3 ; 
         FIG. 5  is a graph illustrating a TGC curve corresponding to an implicit function of a continuous fitting curve shown in the graph of  FIG. 4 ; 
         FIG. 6  is a graph illustrating the application of a TGC curve to ultrasound image data; 
         FIG. 7  is a graph to describe a DR parameter extraction method in an ultrasound diagnostic apparatus according to an exemplary embodiment; 
         FIG. 8  is a control flow chart of a TGC curve extracting operation of an image parameter processor of an ultrasound diagnostic apparatus according to an exemplary embodiment; and 
         FIG. 9  is a control flow chart of a DR parameter calculating operation of an image parameter processor of an ultrasound diagnostic apparatus according to an exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. 
       FIG. 1  is a block diagram of an ultrasound diagnostic apparatus according to an exemplary embodiment. 
     An ultrasound diagnostic apparatus  1  may include a probe  10 , a beamformer  20 , an image signal processor  30 , a scan converter  40 , an image processor  50 , a video processor  60 , a display  70 , and an image parameter processor  80 . The image signal processor  30 , the image processor  50 , the video processor  60 , and the image parameter processor  80  may be integrated into at least one processor. 
     The probe  10  may include a plurality of one or two-dimensional transducers  11 . The probe  10  appropriately delays input times of pulses input to the respective transducers  11  to transmit a focused ultrasound beam to an object (not shown) along a transmission scan line. Ultrasound echo signals reflected from the object are input to the respective transducers  11  with different reception times and the respective transducers  11  generate the input ultrasound echo signals. 
     The beamformer  20  focuses the ultrasound echo signals transmitted by the respective transducers  11  of the probe on the object, and adds time delays to the ultrasound echo signals which are reflected from the object and input to the respective transducers  11  to focus the ultrasound echo signals. 
     The image signal processor  30 , for example a digital signal processor (DSP), performs envelope detection processing to detect the size of the ultrasound echo signals based on the ultrasound echo signals focused by the beamformer  20 , thereby forming ultrasound image data. That is, the image signal processor  30  forms the ultrasound image data based on location information of a plurality of points on each scan line and data obtained from the respective points. The ultrasound image data includes coordinates on an X-Y coordinate system of each point, angle information of each scan line with respect to a vertical scan line, and data obtained from each point. Performing the envelope detection processing upon a signal is disclosed in detail in U.S. Pat. No. 6,689,060, the disclosure of which is incorporated by reference. 
     The scan converter  40  scan-converts the ultrasound image data so that the ultrasound image data generated from the image signal processor  30  may be displayed on a display region of the display  70 . 
     The image processor  50  performs various types of image processing, for example B-mode and M-mode Doppler image processing, upon the scan-converted ultrasound image data generated by the scan converter  40  in order to display an ultrasound image in a form desired by a user on the display  70 . 
     The video processor  60  processes the scan-converted ultrasound image data so as to be displayed on the display  70  as an ultrasound image and transmits the processed ultrasound image data to the display  70 . 
     The display  70  displays the ultrasound image data generated from the video processor  60  as an ultrasound image. 
     The image parameter processor  80  includes a TGC processor  82 , a DR processor  84 , and an algebraic compression processor  86 . 
     The TGC processor  82  calculates a TGC parameter from the envelope-detection (ED) processed ultrasound image data generated from the image signal processor  30 . The function and operation of the TGC processor  82  will be described in detail later with reference to  FIG. 3 . 
     The DR processor  84  calculates a DR parameter from the ED processed ultrasound image data to which a TGC curve generated from the TGC processor  82  is applied. The DR parameter refers to an image parameter to adjust the contrast of an ultrasound image. The function and operation of the DR processor  84  will be described in detail later with reference to  FIG. 7 . 
     The algebraic compression processor  86  performs algebraic compression using a logarithmic function on the ED processed ultrasound image data. As a value of the DR parameter is increased, the slope of the logarithmic function is increased and thus the contrast of the ED processed ultrasound image data is increased. The algebraic compression processor  86  performs algebraic compression on the ED processed ultrasound image data to which the TGC parameter and the DR parameter are applied. 
       FIG. 2  is a block diagram of an image parameter processor of an ultrasound diagnostic apparatus according to an exemplary embodiment,  FIG. 3  is a graph to describe a TGC parameter extraction method in an ultrasound diagnostic apparatus according to an exemplary embodiment,  FIG. 4  is a graph to describe a method of eliminating a discontinuous region of a linear fitting curve of the graph of  FIG. 3 ,  FIG. 5  is a graph illustrating a TGC curve corresponding to an implicit function of a continuous fitting curve shown in the graph of  FIG. 4 ,  FIG. 6  is a graph illustrating the application of a TGC curve to ultrasound image data, and  FIG. 7  is a graph to describe a DR parameter extraction method in an ultrasound diagnostic apparatus according to an exemplary embodiment. 
     The image parameter processor  80  calculates a TGC parameter and a DR parameter upon receiving ED processed ultrasound image data from the image signal processor  30 , and applies the calculated parameters to the whole frame of the ED processed ultrasound image data. 
     The TGC processor  82  extracts the TGC parameter from the ED processed ultrasound image data. Hereinafter, a method for the TGC processor  82  to extract the TGC parameter will be described in detail. 
     Referring to  FIG. 3 , the TGC processor  82  accumulates the ED processed ultrasound image data in a horizontal direction. Here, the horizontal direction of the ED processed ultrasound image data is perpendicular to the depth direction of the ED processed ultrasound image data. In  FIG. 3 , the axis of abscissa denotes the depth of the ED processed ultrasound image data and the axis of ordinate denotes the size (that is, amplitude) of the ED processed ultrasound image data located in a horizontal direction at the same depth. The size of ED processed ultrasound image data is proportional to brightness. 
     The TGC processor  82  divides the accumulated ED processed ultrasound image data into a prescribed number of blocks. In  FIG. 3 , the accumulated ED processed ultrasound image data is divided into four blocks. 
     The TGC processor  82  performs linear fitting upon the amplitude of the ED processed ultrasound image data every block so as to recognize a trend in the amplitude of the ED processed ultrasound image data. Linear fitting of the amplitude of ED processed ultrasound image data corresponds to curve fitting of the ED process ultrasound image data. The TGC processor  82  may divide a non-linear curve of an input signal into a plurality of pieces to perform fitting by applying a piecewise linear function every piece and may generate a linear output according to the slope of a non-linear curve of each piece. Curve fitting of a signal is applying a piecewise linear function to the signal so as to recognize a trend in the signal. If the TGC processor  82  performs curve fitting on the ED processed ultrasound image data, a linear fitting curve is generated. 
     The TGC processor  82  eliminates discontinuous curve regions such as points A, B, and C shown in  FIG. 3 . The TGC processor  82  uses a mean value of a discontinuous curve region in order to eliminate a discontinuous curve region of a linear fitting curve. The TGC processor  82  adjusts the linear fitting curve using a mean value of a discontinuous curve region (that is, a median value of the amplitude of data) as a connecting point. 
     Referring to  FIG. 4 , it will be appreciated that a continuous fitting curve is obtained by connecting median values (or mean values) of the amplitudes of accumulated ED processed ultrasound image data at discontinuous points A, B, and C. Meanwhile, when a fitting curve is discontinuous, extracted ED processed ultrasound image data has a boundary. 
     Referring to  FIG. 5 , the TGC processor  82  extracts a TGC curve. The TGC processor  82  extracts a TGC curve corresponding to an implicit function of a continuous fitting curve. When a linear fitting curve calculated in a previous procedure is continuous, the TGC processor  82  extracts a curve corresponding to an implicit function of the linear fitting curve as a TGC curve. When a linear fitting curve calculated in a previous procedure is discontinuous, the TGC processor  82  extracts, as a TGC curve, a curve corresponding to an implicit function of a continuous fitting curve which has corrected the linear fitting curve using the above-described method. 
     The TGC processor  82  applies a TGC curve to the ED processed ultrasound image data. If the TGC curve is applied to the ED processed ultrasound image data, uniformity of the ED processed ultrasound image data may be increased. 
     Referring to  FIG. 6 , it may be appreciated that the amplitude of the ED processed ultrasound image data which is attenuated according to depth may be compensated by the application of the TGC curve to the ED processed ultrasound image data. 
     After the application of the TGC curve to the ED processed ultrasound image data, if the amplitude of the ED processed ultrasound image data is less than a preset first reference value, the TGC processor  82  determines that the ED processed ultrasound image data is noise. If the ED processed ultrasound image data to which the TGC curve is applied is judged to be noise, the TGC processor  82  lowers the amplitude of the ED processed ultrasound image data by dividing the ED processed ultrasound image data by a TGC value or by a preset second reference value. The preset second reference value is determined in consideration of the first reference value by a designer. 
     The DR processor  84  sets a DR parameter using the ED processed ultrasound image data to which the TGC curve is applied. Referring to  FIG. 7 , the DR processor  84  sets a DR parameter using a maximum value, a mean value, and a median value of the ED processed ultrasound image data to which the TGC curve is applied. 
     The maximum value of the ED processed ultrasound image data to which the TGC curve is applied indicates a value of the ED processed ultrasound image data having the largest pixel value. A mean value of the ED processed ultrasound image data to which the TGC curve is applied indicates a value calculated in consideration of the size of the ED processed ultrasound image data and the number of ED processed ultrasound image data (or pixels) having that size. For example, if the number of the ED processed ultrasound image data having a size of ‘a’ is 2 and if the number of data having a size of ‘b’ is 3, then the mean value of data is (a*2+b*3)/(2+3). A median value of the ED processed ultrasound image data to which the TGC curve is applied indicates a value corresponding to the middle of the largest value and the smallest value of the ED processed ultrasound image data. For example, if the largest value of the ED processed ultrasound image data is 100 and if the smallest value of the ED processed ultrasound image data is 0, then a median value of the EC processed ultrasound image data is 50. 
     As indicated in the following Equation 1, the DR processor  84  may determine, as a high value of a DR parameter, a value obtained by subtracting a prescribed value, for example 10 dB, from the maximum value of the ED processed ultrasound image data to which the TGC curve is applied. The DR processor  84  may determine, as a low value of a DR parameter, a value obtained by subtracting a prescribed value, for example 10 dB, from the mean value of the ED processed ultrasound image data to which the TGC curve is applied.
 
DR_high_offset=max−10 dB:high value
 
DR_low_offset=mean−10 dB:low value  [Equation 1]
 
     The DR processor  84  may correct a DR parameter considering the difference between the mean value of the ED processed ultrasound image data to which the TGC curve is applied and the median value of the ED processed ultrasound image data to which the TGC curve is applied. 
     The DR processor  84  determines that the bigger the difference between the mean value of the ED processed ultrasound image data to which the TGC curve is applied and the median value of the ED processed ultrasound image data to which the TGC curve is applied is, the more information of the ED processed ultrasound image data having a larger size includes. Accordingly, the DR processor  84  varies a DR parameter by increasing a high value of a DR determined by Equation 1. A varied degree of the high value of the DR is preset according to the difference between a mean value and a median value of data. For instance, if the difference between a mean value and a median value of data is 20 dB, a high value may be increased by 5 dB and if the difference therebetween is 30 dB, a high value may be increased by 8 dB. 
       FIG. 8  is a control flow chart to describe a TGC curve extracting operation of an image parameter processor of an ultrasound diagnostic apparatus according to an exemplary embodiment. 
     The TGC processor  82  acquires ED processed ultrasound image data from the image signal processor  30  in step  100 . The ED processed ultrasound image data may also be called an envelope signal. 
     The TGC processor  82  accumulates the ED processed ultrasound image data in a horizontal direction in step  110 . Namely, the TGC processor  82  accumulates a mean size of the ED processed ultrasound image data by detecting pixels existing at the same depth at each region of the ED processed ultrasound image data. 
     Next, the TGC processor  82  divides the accumulated ED processed ultrasound image data into a prescribed number of blocks in step  120 . 
     The TGC processor  82  performs linear fitting upon the amplitude of data every block in step  130 . Linear fitting of the amplitude of the ED processed ultrasound image data is applying a piecewise linear function to a signal so as to recognize a trend in the signal. If the TGC processor  82  performs the linear fitting upon the ED processed ultrasound image data, a linear fitting curve is generated. 
     The TGC processor  82  eliminates a discontinuous curve region of the linear fitting curve in step  140 . To eliminate the discontinuous curve region of the linear fitting curve, the TGC processor  82  uses a mean value of the discontinuous curve region. The TGC processor  82  corrects the linear fitting curve using a mean value of the discontinuous curve region (that is, a median value of the size of data) as a connecting point. 
     The TGC processor  82  extracts a TGC curve corresponding to an implicit function of the linear fitting curve in step  150 . 
       FIG. 9  is a control flow chart to describe a DR parameter calculating operation of an image parameter processor of an ultrasound diagnostic apparatus according to an exemplary embodiment. 
     The DR processor  84  acquires the ED processed ultrasound image data to which a TGC curve is applied from the TGC processor  82  in step  200 . 
     The DR processor  84  calculates a maximum value, a mean value, and a median value of the ED processed ultrasound image data to which the TGC curve is applied in step  210 . 
     The DR processor  84  determines, as a high value of a DR parameter, a value obtained by subtracting a prescribed value from the maximum value of the ED processed ultrasound image data to which the TGC curve is applied and determines, as a low value of the DR parameter, a value obtained by subtracting a prescribed value from the mean value of the ED processed ultrasound image data to which the TGC curve is applied in step  220 . 
     The DR processor  84  adjusts the DR parameter by increasing a high value of a DR determined according to the difference between the mean value of the ED processed ultrasound image data to which the TGC curve is applied and the median value of the ED processed ultrasound image data to which the TGC curve is applied in step  230 . 
     According to an aspect of an exemplary embodiment, since image parameters may be automatically adjusted, a user may diagnose ultrasound images more accurately and conveniently. 
     Although a few exemplary embodiments have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the inventive concept, the scope of which is defined in the claims and their equivalents.