Ultrasonic imaging apparatus indicating dispersion of characteristic parameter of medium

Abstract: An ultrasonic imaging apparatus for obtaining a two-dimensional distribution of a predetermined characteristic parameter of a medium of the ultrasound at various points in a plane. The apparatus contains a unit (37) for designating a region of interest in said plane, and a unit (32, 33, 34, 35, 36) for obtaining and indicating statistical information on a dispersing characteristic of said predetermined characteristic parameter of the medium at the various points in the region of interest of said plane. In addition, the apparatus contains a unit (32, 33, 34, 35, 36) for obtaining and indicating a recent history of the dispersing characteristics during the operation of obtaining the two-dimensional distributions which are most recently carried out. Further, the apparatus contains a unit (39) for obtaining and indicating the plane for which the minimum standard deviation is obtained, and a unit (31, 36) for indicating the two-dimensional distribution for the plane.

Description: The present invention relates to an ultrasonic imaging apparatus which functions to display an image (representation) of a two-dimensional distribution of a tissue characterization parameter of a tissue, for example an ultrasonic attenuation coefficient, in a realtime mode. In the field of the ultrasonic diagnosis, such two-dimensional distributions of tissue characterization parameters, for example an ultrasonic attenuation coefficient, an ultrasonic reflection coefficient, and an elasticity parameter, are used to diagnose a condition of the tissue. For example, the value of the ultrasonic attenuation coefficient of tissue of a liver suffering from hepatitis is small compared with a normal tissue, and the value of the ultrasonic attenuation coefficient of a fatty liver is large compared with a normal tissue. Since high accuracy is required in ultrasonic diagnosis, the tissue characterization parameters must be determined precisely. One type of conventional ultrasonic imaging apparatus which functions to display an image of a two-dimensional distribution of a tissue characterization parameter of a tissue in a realtime mode is disclosed in the Japanese Unexamined Patent Publication No.62-109553, U.S.Patent No.4,836,210 of Shiba et al, dated June 6, 1989, and in EP-A-0154869. In such ultrasonic imaging apparatuses, a pulsed ultrasound beam is generated and injected into a tissue in a certain direction, and ultrasound which is reflected at various depths of the tissue in the same direction is detected. The direction of the pulsed ultrasound is varied (scanned) so that a plane is scanned by the pulsed ultrasound during one plane scan cycle. Thus, a two-dimensional distribution of the tissue characterization parameter in the plane (cross section of the tissue) is obtained. The above injection and detection of the ultrasound is carried out by means of an ultrasonic transducer array. The operator (doctor) applies a probe containing the transducer array to the skin of a human body to diagnose the condition of the tissue under the skin. However, the obtained values of the above tissue characterization parameters fluctuate due to subtle movements of the probe or the tissue which is subject to the diagnosis. Further, for example, the values of the ultrasonic attenuation coefficient, which are obtained as above, vary greatly when a structure which is different from the tissue which is to be diagnosed, e.g. a vascular tract, exists in the scanned cross-section. Generally, it is considered that the obtained values of the tissue characterization parameters are significant only when the obtained values are stable. Thus, generally, the values of the tissue characterization parameters must be obtained on a cross section of the tissue where the obtained values are stable. Nevertheless, conventionally, it is difficult for the operator to determine whether or not an obtained value of a tissue characterization parameter is stable. Therefore, in conventional ultrasonic imaging apparatuses, the credibility of the obtained values of the tissue characterization parameters is low. To address this problem, US 4817015 discloses ultrasonic imaging apparatus which may be considered to comprise: ultrasonic pulse generating means for emitting a predetermined sequence of ultrasonic pulses into a medium to be examined, the pulses of the sequence being emitted along respective differently-directed emission paths in a predetermined plane so that over the course of the said sequence a working area of the predetermined plane is scanned within the said medium; ultrasonic detection means arranged for detecting reflections of each such emitted pulse back along the emission path thereof; two-dimensional distribution obtaining means, connected for measuring the time interval between the emission of each such pulse and the detection by the ultrasonic detection means of each such reflection of that pulse, so as to determine the distances from the detection means of points in the said working area at which such reflections occur, and operable to employ the determined distances to produce a two-dimensional representation of the distribution, throughout the said working area, of the respective values of a predetermined characteristic parameter of the medium at the said points; region of interest designating means, selectively controllable to define a restricted region of interest in the said working area; and statistical information obtaining means operable to obtain, based on the parameter values of all such points in the said region of interest, statistical information relating to the dispersion of those values in that region; the apparatus being operable repetitively to scan the working area a plural number of times in succession so as to produce a succession of such representations and to obtain for each representation corresponding such statistical information relating to the dispersion in the region of interest. The statistical information obtaining means in this apparatus are employed as a texture discriminator for detecting a semi-periodic array of specular scatterers at some spacing d resolvable by the ultrasonic imaging apparatus but not detectable in the image by a human observer due to image texture noise. As statistical information, a square b of the mean of the intensities of parameter values at points in the region of interest, a variance t of those intensitites, a measure d of average spacing of periodic and semi-periodic arrays of specular scatterers, and a variation p of backscattered intensities are obtained so as to classify the region of interest. The statistical information is obtained "on-line", the displayed image being updated continuously every video frame, and values of the statistical information, which are simply displayed by the side of the image in numerical form, are updated at a rate of approximately once every three video frames. Ultrasonic imaging apparatus embodying the present invention is characterised by two-dimensional distribution storing means for storing a plurality of the successively-produced representations, and by statistical information storing means for storing the said corresponding statistical information for each representation of the said plurality. Such ultrasonic imaging apparatus can enable an operator to easily determine stability of the tissue characterization parameter values which are obtained from the apparatus. With such ultrasonic imaging apparatus an operator can easily identify the representation, from amongst a plurality of representations for which values of the tissue characterization parameter have been most recently obtained, which has the most stable tissue characterization parameter values. Reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a block diagram showing an ultrasonic imaging apparatus embodying the present invention; Figure 2 is a block diagram showing an example construction of a parameter calculation circuit 100 in the Fig. 1 apparatus; Figure 3 is a block diagram showing a construction of further circuitry of the Fig. 1 apparatus; Figure 4 is a block diagram showing an example construction of a frequency distribution obtaining circuit 33 in the Fig. 3 circuitry; Figure 5 is a histogram, showing a frequency distribution of values of a tissue characterization parameter in a region of interest, produced by the Fig. 4 circuit; Figure 6 is a diagram showing an example display, produced by the Figure 1 apparatus, of a two-dimensional representation of the distribution of detected values of a tissue characterization parameter and a representation of a designated region of interest; Figure 7 is a diagram showing an example display, produced by the Figure 1 apparatus, of a recent history of the average of detected values of a tissue characterization parameter in a region of interest; Figure 8 is a diagram showing an example display, produced by the Figure 1 apparatus, of a recent history of the standard deviation of detected values of a tissue characterization parameter in a region of interest; Figure 9 is a diagram showing an example display, produced by the Figure 1 apparatus, of a recent history of the skewness of a frequency distribution of detected values of the tissue characterization parameter in a region of interest; Figure 10 is a diagram showing an example display, produced by the Figure 1 apparatus, of a recent history of the kurtosis of a frequency distribution of detected values of the tissue characterization parameter in a region of interest; Figure 11 is a diagram showing an example display, produced by the Figure 1 apparatus, of a recent history of the frequency distribution of detected values of a tissue characterization parameter in a region of interest; Figure 12 is a diagram showing an example display produced by the Figure 1 apparatus during an operation of designating a representation (frame) performed by an operator using a cursor; Figure 13 is a diagram showing an example display produced by the Figure 1 apparatus when performing an operation of identifying a representation (frame) having the minimum standard deviation among a plurality of representations which have been most recently produced by the apparatus; and Figure 14 is a diagram of an example display, produced by the Figure 1 apparatus, showing a frequency distribution of values of a tissue characterization parameter in a current representation (frame), and also showing superimposed thereon a frequency distribution of values of the tissue characterization parameter in the representation having the minimum standard deviation. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 Figure 1 is a block diaaram showina one constructionof ultrasonic imaging apparatus embodying the present invention. In Fig. 1, reference numeral 1 denotes an ultrasonic transducer array, 2 1 , 2 2 , 2 3 , ··· 2 n and 6 1 , 6 2 , 6 3 , ··· 6n each denote an amplifier, 3 1 , 3 2 , 3 3 , ··· 3 n and 7 1 , 7 2 , 7 3 , ... 7 n each denote a delay circuit, 4 denotes a pulse generator, 5 denotes a timing generator, 8 denotes a summing amplifier, 9 denotes a LOG amplifier, 9' denotes a time gain control circuit, 10 denotes a detector, 11 denotes a low pass filter, 12 denotes an analog to digital converter, 100 denotes a parameter calculation circuit, 200 denotes a characteristic portion of the embodiment of the present invention, and 300 denotes a display unit. The timing generator 5 generates a timing signal at a constant rate, and the pulse generator 4 generates a pulse signal to generate an ultrasound pulse. Each delay circuit 3 i and 7 i (i=1, 2, ··· n) is connected in series to a corresponding one of the amplifiers 2 i and 6 i (i=1, 2, ··· n). The pulse signal is input in parallel to the respective series connections of the delay circuits 3 i (i=1, 2, ··· n) and the amplifiers 2 i (i=1, 2, ··· n). The ultrasonic transducer array 1 comprises a plurality of transducer elements. Each transducer element comprises a piezo-electric element which converts an electric signal to a mechanical deformation to generate an ultrasound, and generates an electric signal when the element receives an ultrasound. The transducer array 1 is manually applied to a skin over a region of tissue of the human body in which a doctor is interested, to diagnose the region. The respective outputs of the amplifiers 2 i are respectively applied to the plurality of transducer elements of the ultrasonic transducer array 1. Delay times in the above delay circuits 3 i (i=1, 2, ··· n) are controlled so that the ultrasound signals generated respectively by the above transducer elements are synthesized to form an ultrasound beam (emitted pulse) directed in a certain direction for each cycle of the output of the ultrasound, and the direction is moved to scan a working area of a cross-section (predetermined plane) of the tissue over the course of each scanning cycle. The electric signals which are output from the plurality of transducer elements are respectively input in parallel into the series connections of the delay circuits 7 i (i=1, 2, ··· n) and the amplifiers 6 i (i=1, 2, ··· n). The outputs of the series connections of the delay circuits 7 i (i=1, 2, ··· n) and the amplifiers 6 i (i=1, 2, ··· n) are summed in the summing amplifier 8 and the resulting summed signal is applied to the LOG amplifier 9. Delay times in the above delay circuits 7 i (i=1, 2, ··· n) are controlled so that the summed signal corresponds to ultrasound which is received by the transducer array 1 in the same direction in which the ultrasound beam is being generated by the transducer array 1, and the direction is moved to scan a cross section of the tissue for each scanning cycle, synchronized with the above scanning operation by the delay circuits 3 i (i=1, 2, ··· n). The LOG amplifier 9 amplifies the summed signal. The gain of the LOG amplifier 9 is controlled by the time gain control circuit 9' so that the gain of the LOG amplifier 9 is increased, in accordance with a logarithmic law, with time that has elapsed since the instant at which the emitted pulse of ultrasound was generated by the transducer array 1. The output of the LOG amplifier 9 is applied in parallel to the detector 10 and the parameter calculation circuit 100. The envelope of the above output of the LOG amplifier 9 is detected in the detector 10, and the detected signal is input into the low pass filter 11. The output of the low pass filter 11 corresponds to ultrasonographic image data. The output of the low pass filter 11 is converted to a digital form by the analog to digital converter 12. The digital data is supplied to the characteristic portion 200. Parameter Calculation Circuit (Fig. 2) Figure 2 is a block diagram showing a construction of an example of the parameter calculation circuit 100 in Fig. 1. In Fig. 2, reference numeral 54 denotes a gradient calculation circuit, 55 denotes a center frequency detector, 56 denotes a divider, and 57 denotes a multiplier. The gradient calculation circuit 54 obtains a gradient of an envelope of the above output of the LOG amplifier 9 in a digital form, and the center frequency detector 55 detects a center frequency of the output of the LOG amplifier 9 in a digital form. The divider 56 divides the output of the gradient calculation circuit 54 by the output of the center frequency detector 55, and the multiplier 57 multiplies the output of the divider 56 by a constant -1/2c to obtain the ultrasonic attenuation coefficient. The obtained ultrasonic attenuation coefficient is supplied to the above characteristic portion 200. A detailed description of a suitable construction for obtaining the ultrasonic attenuation coefficient is disclosed in the Japanese Unexamined Patent Publication No. 62-109553. The parameter calculation circuit 100 may alternatively have a different construction, suitable for obtaining an ultrasonic reflection coefficient, or another elasticity parameter. These constructions for obtaining the ultrasonic reflection coefficient and the other elasticity parameters are conventionally known. Characteristic Portion (Fig. 3 ) Figure 3 is a block diagram showing a construction of the characteristic portion of the embodiment of the present invention. In Fig. 3, reference numeral 31 denotes a frame memory for storing a two-dimensional representation of the distribution of a tissue characterization parameter, 32 denotes a statistic calculation circuit, 33 denotes a frequency distribution obtaining circuit, 34 denotes a scroll memory, 35 denotes a memory, 36 denotes a digital scan converter, 37 denotes a region of interest designation circuit, 38 denotes a frame designation circuit, 39 denotes a minimum dispersion frame obtaining circuit, 40 denotes a freeze control circuit, 41 denotes a frame memory for ultrasonographic image data, and 42 denotes a CRT. The above-mentioned digital ultrasonographic image data is stored in the frame memory 41, and the above-mentioned digital tissue characterization parameter distribution data is stored in the frame memory 31. These frame memories each hold the data of a plurality of frames which have been most recently scanned (observed). The statistic calculation circuit 32 obtains statistical information (a statistical measure) relating to the dispersion (dispersing characteristic) of the respective characteristic parameter values of the tissue at the various points in a restricted region of interest of the working area of of each cross section (two-dimensional representation). The region of interest is designated by the region of interest designation circuit 37 as explained later. Statistic Information The statistical measure of dispersion is, for example, a standard deviation of the values of the tissue characterization parameter which were obtained in the parameter calculation circuit 100 within the region of interest in each cross section, a skewness of a frequency distribution of the values of the tissue characterization parameter which were obtained in the parameter calculation circuit 100 within the region of interest in each cross section, or the kurtosis of a frequency distribution of the values of the tissue characterization parameter which were obtained in the parameter calculation circuit 100 within the region of interest in each cross section. The values of the tissue characterization parameter in the region of interest are denoted by X i (i=1,2, ··· N), where N denotes the total number of obtained values in the region of interest. The statistical measure of dispersion is calculated by the statistic calculation circuit 32 as follows: An average m of the values of the tissue characterization parameter which were obtained in the parameter calculation circuit 100 within the region of interest in each cross section, is obtained by the following equation (1). The variance σ 2 is obtained by the following equation (2). The standard deviation a is obtained by the following equation (3). σ = √σ 2 The third order center moment µ 3 is obtained as the following equation (4). The fourth order center moment µ 4 is obtained by the following equation (5). The skewness S of the frequency distribution of the values of the tissue characterization parameter in the region of interest indicates asymmetry of the frequency distribution, and is obtained by the following equation (6). S=µ 3 /σ 3 The kurtosis K of the frequency distribution of the values of the tissue characterization parameter in the region of interest indicates flatness of the frequency distribution, and is obtained by the following equation (7). K=µ 4 /σ 4 -3 The results of the statistic calculations as above are input into the scroll memory 34 for each frame or two-dimensional representation (cross section). The scroll memory 34 stores the statistic information for a predetermined number of frames which are most recently observed. Frequency Distribution Obtaining Circuit (Fig. 4) The frequency distribution obtaining circuit 33 obtains a frequency distribution of the values of the tissue characterization parameter in the region of interest in each two-dimensional representation (cross section). Figure 4 is a block diagram showing a construction of the frequency distribution obtaining circuit 33 in Fig. 3. In Fig. 4, reference numeral 50 denotes a decoder, and 51 1 , 51 2 , 51 3 , ··· 51 n each denote an accumulator. The values of the tissue characterization parameter are sorted into a plurality of ranks (ranges of the values) to obtain a histogram of the frequency distribution, an example of which is shown in Figure 5. The accumulators 51 1 , 51 2 , 51 3 , ··· 51 n are provided for the respective ranks. The decoder 50 receives respective values of the tissue characterization parameter which are stored in the frame memory 31. The decoder 50 has a plurality of outputs corresponding to the plurality of ranks to realize the function of the sorting. One of the outputs of the decoder 50, corresponding to one of the ranks into which the received value is to be sorted, becomes active when the enable signal is active. The enable signal is generated by the region of interest designation circuit 37, and is made active when values of the tissue characterization parameter in the region of interest are output from the frame memory 31. A reset signal is applied to the plurality of accumulators 51 1 , 51 2 , 51 3 , ··· 51 n when the accumulators should be reset. The accumulation is carried out for example, for each scanning cycle (each cross section), or for a predetermined number of successive scanning cycles. Figure 5 is an example histogram showing a frequency distribution of values of the tissue characterization parameter in the region of interest. The above obtained frequency distribution is input into the memory 35 for each frame (cross section). The memory 35 stores the data of the frequency distributions for a predetermined number of frames which are most recently observed. Fig. 6 Figure 6 is a diagram showing an example of the display of the two-dimensional distribution of detected values of a tissue characterization parameter and an indication of the designated region of interest. Viewing the display, the operator can designate a desired region of interest, for example, by a pointing device. The region of interest designation circuit 37 controls the operation reading the values of the tissue characterization parameter from the frame memory 31 and the operation writing the values into the statistic calculation circuit 32 and the frequency distribution obtaining circuit 33 by supplying corresponding addresses and reading and writing signals. The technique of designating a region of interest is well-known. Indication of History of Statistics (Figs. 3, 7, 8, 9, and 10) In a display mode, a recent history of one or more of the aforementioned types of statistic measure of dispersion over a predetermined number of successive frames (ending with the current frame) is indicated in a real time mode as shown in Figs. 8 to 11. In addition to the measure(s) of dispersion the apparatus may also display, as shown in Fig. 7, a recent history of an average of the parameter values in the region of interest over a predetermined number of successive frames. The history data to be displayed is supplied from the scroll memory 34 and the memory 35. In the display mode, each item of statistic information in the history may be calculated for a predetermined number of successive frames instead of one frame. Figure 7 is a diagram showing an example indication of a recent history of an average of the detected values of a tissue characterization parameter in a region of interest, Figure 8 is a diagram showing an example indication of a recent history of a standard deviation of a frequency distribution of detected values of a tissue characterization parameter in a region of interest, Figure 9 is a diagram showing an example indication of a recent history of the skewness of a frequency distribution of detected values of the tissue characterization parameter in a region of interest, Figure 10 is a diagram showing an example indication of a recent history of the kurtosis of a frequency distribution of detected values of the tissue characterization parameter in a region of interest, and Figure 11 is a diagram showing an example indication of a recent history of the frequency distribution of detected values of a tissue characterization parameter in a region of interest. In Fig. 11, the lines for the frequency distributions of the different frames may be represented by different respective types of lines for example by using different colors. The operator can view the display while manipulating the probe. Therefore, for example, the operator can recognize whether or not a most recently variation in a position of the probe gives a better (more stable and credible) result, and can avoid making use of unstable data based on the above history indications. Freeze Control and Frame Designation (Figs. 3 and 12 ) When the operator finds in the above history indication that credible data has been obtained, the operator can freeze the operation of updating (renewing) the contents of the scroll memory 34 and the memory 35, and thus, can freeze the history indication. The freezing operation can be carried out through the freeze control circuit 40. When the freeze control circuit 40 receives a command to effect the freeze operation, the freeze control circuit 40 supplies a freeze control signal to the frame memories 31 and 41, the scroll memory 34, and the memory 35 to freeze these elements, as shown in Fig. 3. Fiaure 12 is a diaqram showing an example display in an operation of designating a frame, performed by an operator using a cursor. As shown in Fig. 12, the operator can designate one of the frames for which the history of the statistic information is indicated, based on the indication, by moving a cursor to the frame in the history indication using a pointing device (not shown). This operation is realized out by means of the frame designation circuit 38. Responding to the designation by the operator, the frame designation circuit 38 can control the frame memories 31 and 41, the scroll memory 34, and the memory 35, so that these memories output contents thereof regarding the designated frame, to the digital scan converter 36. Further, the frame designation circuit 38 can send the information on the designated frame to the digital scan converter 36 so that the above cursor indication is realized. Further, the aforementioned region of interest designation circuit 37 can be operated again to reobtain statistic information on the dispersing characteristic of the predetermined characteristic parameter in a region of interest which is different from the reqion of interest which was first designated. By redesignating the new region of interest, by means of the region of interest designation circuit 37,after freezing the above memories in Fig. 3, the above statistical information can be obtained by using the frozen data of the tissue characterization parameter, and operating the statistic calculation circuit 32 and/or the frequency distribution obtaining circuit 33. Calculation of Most Stable Frame (Figs. 3, 13, and 14) The most stable frame among a plurality of frames which have been most recently observed, can be automatically obtained by using the recent history data of the statistic information. The minimum dispersion frame obtaining circuit 39 determines the frame having the minimum standard deviation. Although not shown, the minimum dispersion frame obtaining circuit 39 may comprise registers for holding the frame number of the frame found so far to have the minimum standard deviation, and for holding the minimum standard deviation found so far, and a comparator for comparing a standard deviation of a current frame with the held standard deviation. the minimum dispersion frame obtaining circuit 39 replaces the held frame number and the standard deviation with the current frame number and the standard deviation of the current frame when the current standard deviation is not larger than the held standard deviation. When a command to indicate the frame of the minimum standard deviation which is determined by the minimum dispersion frame obtaining circuit 39 is input, the minimum dispersion frame obtaining circuit 39 sends a marker indication data to the digital scan converter 36. The marker indication data indicates how many frames before the current frame the frame having the minimum standard deviation is. When the aforementioned control circuit of the digital scan converter 36 receives the marker indication data, a marker indication is shown superimposed on the above history indication of the statistic information. Figure 13 is a diagram showing an example indication of a frame found to have the minimum standard deviation among a plurality of frames which has been most recently observed. Further, a histogram indicating a frequency distribution of the values of the tissue characterization parameter in a current frame can be displayed superimposed on another histogram indicating a frequency distribution of the values of the tissue characterization parameter in the above-mentioned frame having the minimum standard deviation, as shown in Fig. 14. This form of display is realized by controlling the memory 35 by means of the frame designation circuit 38 by another output of the minimum dispersion frame obtaining circuit 39. The output of the minimum dispersion frame obtaining circuit 39 includes information of the frame having the minimum standard deviation. When the frame designation circuit 38 receives the above output, the frame designation circuit 38 can control the frame memories 31 and 41, the scroll memory 34, and the memory 35, so that these memories output contents thereof regarding the frame of the minimum standard deviation, to the digital scan converter 36. Otherwise, using the function of the minimum dispersion frame obtaining circuit 39, it is possible to set the ultrasonic imaging apparatus of Fig. 1 so that the apparatus automatically indicates the image of the ultrasonograph and the two-dimensional distribution image (representation) of the tissue characterization parameter of the frame of the minimum standard deviation by controlling the frame memories 31 and 41 through the frame designation circuit 38. Although not shown, all the above operations in the embodiment can be realized by either a hardware logic circuit or by software in a microcomputer.

Claims: Ultrasonic imaging apparatus including: ultrasonic pulse generating means (1-5) for emitting a predetermined sequence of ultrasonic pulses into a medium to be examined, the pulses of the sequence being emitted along respective differently-directed emission paths in a predetermined plane so that over the course of the said sequence a working area of the predetermined plane is scanned within the said medium; ultrasonic detection means (1, 3, 6-9) arranged for detecting reflections of each such emitted pulse back along the emission path thereof; two-dimensional distribution obtaining means (100, 41), connected for measuring the time interval between the emission of each such pulse and the detection by the ultrasonic detection means of each such reflection of that pulse, so as to determine the distances from the detection means of points in the said working area at which such reflections occur, and operable to employ the determined distances to produce a two-dimensional representation of the distribution, throughout the said working area, of the respective values of a predetermined characteristic parameter of the medium at the said points; region of interest designating means (37), selectively controllable to define a restricted region of interest in the said working area; and statistical information obtaining means (32,33) operable to obtain, based on the parameter values of all such points in the said region of interest, statistical information relating to the dispersion of those values in that region; the apparatus being operable repetitively to scan the working area a plural number of times in succession so as to produce a succession of such representations and to obtain, for each representation, corresponding such statistical information relating to the parameter-value dispersion in the region of interest; characterised by two-dimensional distribution storing means (31) for storing a plurality of the successively-produced representations, and by statistical information storing means (34,35) for storing the said corresponding statistical information for each representation of the said plurality. Ultrasonic imaging apparatus as claimed in claim 1, further comprising stored distribution indicating means (36, 38) for displaying one of the said two-dimensional representations stored in the said two-dimensional distribution storing means (31). Ultrasonic imaging apparatus as claimed in claim 1 or 2, wherein the said two-dimensional representations stored by the two-dimensional distribution storing means (31) are the representations produced most recently by the two-dimensional distribution obtaining means (100, 41). Ultrasonic imaging apparatus as claimed in claim 1, 2 or 3, further comprising stored statistical information indicating means (36, 42) for displaying the statistical information stored in the said statistical information storing means (34, 35). Ultrasonic imaging apparatus as claimed in any preceding claim, further comprising storage freezing means (40) for freezing an operation of updating the said statistical information storing means (34, 35) and the said two-dimensional distribution storing means (31). Ultrasonic imaging apparatus as claimed in claim 5, further comprising frozen plane designating means (38) operable, after the said statistical information storing means (34, 35) and the said two-dimensional distribution storing means (31) have been frozen, to designate one of the representations stored in the said two-dimensional distribution storing means (31). Ultrasonic imaging apparatus as claimed in claim 6, further comprising designated information indicating means (34, 35, 36) for displaying the two-dimensional representation designated by the said frozen plane designating means (38) and for displaying the said statistical information corresponding to that designated representation. Ultrasonic imaging apparatus as claimed in any preceding claim, further comprising: plane designating means (38) for designating one of the representations stored in the said two-dimensional distribution storing means (31); and history information indicating means (34, 35, 36) for displaying a recent history of the said statistical information, starting with the statistical information for the most-recently-produced representation and ending with the statistical information for the representation designated by the said plane designating means (38). Ultrasonic imaging apparatus according to any preceding claim, further comprising: region of interest redesignating means (37), selectively controllable to define a further region of interest, in the said working area, different from the selected region of interest defined by the said region of interest designating means; and statistical information reobtaining means (32) for obtaining statistical information relating to the dispersion of the parameter values in the said further region of interest. Ultrasonic imaging apparatus according to any preceding claim, wherein the said statistical information includes a statistical measure of the standard deviation of the parameter values of the points in the region of interest. Ultrasonic imaging apparatus according to any preceding claim, wherein the said statistical information includes a statistical measure of the skewness of a frequency distribution of the said parameter values of the points in the region of interest. Ultrasonic imaging apparatus as claimed in any preceding claim, wherein the said statistical information includes a statistical measure of the kurtosis of a frequency distribution of the parameter values of the points in the region of interest. Ultrasonic imaging apparatus according to any one of claims 10 to 12, wherein the statistical measures corresponding respectively to the different representations of the said plurality are displayed simultaneously. Ultrasonic imaging apparatus according to any precedinq claim, wherein the statistical information obtaining means (32, 33) further include frequency distribution obtaining means (33) operable to process the parameter values of the points in the said selected region of interest to obtain a frequency distribution of those values in the region of interest of the representation concerned. Ultrasonic imaging apparatus according to claim 14, wherein the said frequency distributions corresponding respectively to two or more representations are displayed simultaneously. Ultrasonic imaging apparatus as claimed in any preceding claim, wherein the said statistical information obtaining means (32, 33) are also operable to calculate, for each two-dimensional representation, an average of the parameter values of the points in the region of interest. Ultrasonic imaging apparatus as claimed in claim 10, further comprising: minimum standard deviation plane determining means (39) for determining, from the respective statistical measures of standard deviation for the representations of the said plurality, which one of those representations has the minimum standard deviation of the parameter values of the points in the region of interest; and minimum standard deviation plane indicating means (39, 34, 36) for displaying information identifying the representation determined by the minimum standard deviation plane determining means (39) to have the minimum standard deviation. Ultrasonic imaging apparatus as claimed in claim 17, further comprising two-dimensional distribution indicating means (36, 42) for displaying the representation determined by the said minimum standard deviation plane determining means (39) to have the minimum standard deviation. Ultrasonic imaging apparatus as claimed in claim 17 or 18, when read as appended to claim 15, wherein a histogram indicating the said frequency distribution corresponding to the most-recently-produced representation is displayed superimposed on another histogram indicating the said frequency distribution corresponding to the representation determined by the minimum standard deviation plane determining means (39) to have the minimum standard deviation.

Inventors: AMEMIYA SHINICHI, MURAKAMI KEIICHI, SHIBA AKIRA, SHIMURA TAKAKI, YAMADA ISAMU, AMEMIYA, SHINICHI, MURAKAMI, KEIICHI, SHIBA, AKIRA, SHIMURA, TAKAKI, YAMADA, ISAMU
Applicants: FUJITSU LTD, FUJITSU LIMITED
Application year: 1991
Main classification: G01S7
IPC codes: G01S7, G01N29, A61B8