JP5225158B2 - Ultrasonic diagnostic equipment - Google Patents

Description

  The present invention relates to an ultrasonic diagnostic apparatus that obtains and displays a tomographic image of a diagnostic region in a subject using ultrasonic waves, and in particular, from each set of RF signal frame data arranged in time series, The present invention relates to an ultrasonic diagnostic apparatus capable of calculating a strain and elastic modulus of a point and displaying it as an elastic image quantitatively indicating the hardness or softness of a living tissue.

  A conventional general ultrasonic diagnostic apparatus includes an ultrasonic transmission / reception unit for transmitting and receiving ultrasonic waves to a subject, and a tomographic image in the subject including a moving tissue using a reflected echo signal from the ultrasonic transmission / reception unit. A tomographic scanning unit that repeatedly obtains data at a predetermined cycle and an image display unit that displays time-series tomographic image data obtained by the tomographic scanning unit are provided. The structure of the living tissue inside the subject is displayed as, for example, a B mode image.

  On the other hand, recently, using this ultrasonic apparatus, the elastic modulus of a living tissue at a diagnostic site is measured and displayed as an elastic modulus image. Examples of such an ultrasonic device include those described in Patent Document 1 or Patent Document 2.

JP-A-5-317313 JP 2000-60853 A

  Recently, an external force is applied artificially from the body surface of the subject with a pressurization device or an ultrasonic probe, and ultrasonic reception is performed between two adjacent frames (two consecutive frames) that change in time series in that state. A technique has been used in which a correlation is calculated between signals, a displacement at each point is obtained, a distortion is measured by spatially differentiating the displacement, and this distortion data is imaged. In addition, a technique for imaging elastic modulus data represented by Young's modulus of living tissue based on stress distribution and strain data due to external force has become realistic. According to the elastic image created based on such strain and elastic modulus data (hereinafter referred to as elastic frame data), the hardness and softness of the living tissue can be measured and displayed.

  However, the elastic frame data imaging process by such a conventional ultrasonic diagnostic apparatus is a correlation calculation between adjacent RF signal frame data acquired in time series during a series of pressurization or decompression operations. Therefore, the amount of pressurization or decompression given in the time interval between the RF signal frame data composing the set of these multiple RF signal frame data is suitable for rendering elastic image data. When the amount of pressurization or the amount of depressurization (generally about 1%) has not been sufficiently reached, there is a problem that it is difficult to appropriately draw an elastic image based on elastic frame data.

  In addition, during the course of a series of pressurization or depressurization operations, even if the speed at the time of pressurization or depressurization is constant over time, the subject subject can be evenly pressurized in the vertical direction. It is not always the time phase. There may be a time phase caused by pressurizing or depressurizing the object in an oblique direction and / or unevenly, that is, a time phase in which the temporal change of the stress distribution in the object is discontinuous. In such a time phase, a coordinate region with a discontinuous jump in the temporal change in the stress distribution occurs in a series of elastic frame data (strain data) in the time axis direction. Therefore, there is a problem that the image diagnosis becomes difficult because the image includes a region having discontinuous jumps as noise.

  In view of the above-described points, the object of the present invention is to effectively visualize a difference in elasticity as an image in an elastic image diagnosis and stably image even at any time phase with a high S / N ratio. An object of the present invention is to provide an ultrasonic diagnostic apparatus capable of performing the above.

  As a result, the frame interval between the past and present RF signal frame data can be made sufficiently large, and an elastic image based on the elastic frame data can be appropriately rendered. This is particularly useful in ultrasonic testing where the physical or physical limitations of the subject prevent the pressurization or depressurization speed from being increased sufficiently during a series of pressurization or depressurization operations. .

  According to the present invention, an elastic image can be stably depicted with high resolution at an arbitrary time, and at the same time, a means for visually expressing a palpation response attempted by a doctor as a moving image has been realized. It is possible to provide a clinically useful ultrasonic apparatus that retains the real-time property and simplicity of ultrasonic diagnosis.

1 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. The figure which shows one Example of the RF signal frame data selection part of FIG. The figure which shows another Example of the RF signal frame data selection part of FIG. The figure which shows an example of the method of attaching a pressure measurement part (pressure sensor) to an ultrasonic probe, and measuring the pressure between the head of a probe, and a test object. The figure which shows one Example of operation | movement of the elasticity data processing part of FIG. The figure which shows another Example of operation | movement of the elasticity data processing part of FIG. FIG. 7 is a diagram illustrating a relationship before and after logarithmic conversion of elastic frame data in the elastic data processing unit of FIG. FIG. 7 is a diagram showing an example of converting elastic frame data by combining a plurality of functions in the elastic data processing unit of FIG. The figure which shows another Example of operation | movement of the elasticity data processing part of FIG. The figure which shows an example of the relationship between the time change of a pressurization / pressure reduction speed, and the acquisition timing of RF signal. The figure which shows the time fluctuation | variation of the elasticity image luminance distribution when the upper limit and lower limit of elastic frame data are fixed and set. FIG. 10 is a diagram showing temporal variation of an elasticity image luminance distribution when an upper limit value and a lower limit value of elasticity frame data are appropriately set under statistically common conditions in the elasticity data processing unit of FIG. The figure which shows an example of the operation | movement which the RF signal frame data selection part and the elasticity data processing part cooperated.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of an ultrasonic diagnostic apparatus according to the present invention. This ultrasonic diagnostic apparatus is capable of obtaining a tomographic image of a diagnostic region of the subject 100 using ultrasonic waves and displaying an elastic image representing the hardness or softness of a living tissue. As shown in FIG. 1, this ultrasonic diagnostic apparatus includes an ultrasonic probe 101, a transmission circuit 102, a reception circuit 103, a phasing addition circuit 104, a signal processing unit 105, and a black and white scan converter 106. An image display 107, an RF signal frame data selection unit 108, a displacement measurement unit 109, a pressure measurement unit 110, a strain and elastic modulus calculation unit 111, an elastic data processing unit 112, and a color scan converter 113 The switching adder 114 is provided.

  The ultrasonic probe 101, the transmission circuit 102, the reception circuit 103, the phasing addition circuit 104, and the signal processing unit 105 constitute an ultrasonic transmission / reception means. This ultrasonic transmission / reception means obtains a single tomographic image by causing the ultrasonic probe 101 to scan an ultrasonic beam in a certain direction within the body of the subject. The ultrasonic probe 101 is formed by arranging a large number of transducers in a strip shape, and performs mechanical or electronic beam scanning to transmit and receive ultrasonic waves to a subject. Although not shown in the figure, a transducer for receiving reflected echoes is incorporated in the ultrasonic wave generation source. Each vibrator generally has a function of converting an input pulse wave or continuous wave transmission signal into an ultrasonic wave and emitting it, and receiving an ultrasonic wave reflected from the inside of the subject to receive an electric signal. It is formed with the function of converting to and outputting.

  The transmission circuit 102 generates a transmission pulse for generating the ultrasonic wave by driving the ultrasonic probe 101, and determines the convergence point of the ultrasonic wave transmitted by the built-in transmission phasing and adding circuit. It is set to a certain depth. The receiving circuit 103 amplifies the reflected echo signal received by the ultrasonic probe 101 with a predetermined gain. A number of received signals corresponding to the number of amplified transducers are input to the phasing and adding circuit 104 as independent received signals. The phasing and adding circuit 104 inputs the received signal amplified by the receiving circuit 103, controls the phase thereof, and forms an ultrasonic beam at one point or a plurality of convergence points. The signal processing unit 105 inputs the received signal from the phasing addition circuit 104 and performs various signal processing such as gain correction, log compression, detection, contour enhancement, and filter processing.

  The black and white scan converter 106 acquires the RF signal frame data in the subject 100 including the moving tissue in the ultrasonic cycle using the reflected echo signal output from the signal processing unit 105 of the ultrasonic transmission / reception means described above. The signal frame data is displayed on the image display 107 through the switching adder 114. Accordingly, the black and white scan converter 106 is a tomographic scanning means for sequentially reading RF signal frame data in a television system cycle and a means for controlling the system, for example, a reflected echo signal from the signal processing unit 105 is converted into a digital signal. An A / D converter that converts the data, a plurality of frame memories that store tomographic image data digitized by the A / D converter in time series, a controller that controls these operations, and the like. The

  The image display 107 displays time-series tomographic image data obtained by the black and white scan converter 106, and converts the image data output from the black and white scan converter 106 through the switching adder 114 into an analog signal. It comprises a D / A converter and a color television monitor that receives an analog video signal from the D / A converter and displays it as an image.

  In this embodiment, an RF signal frame data selection unit 108 and a displacement measurement unit 109 are provided branched from the output side of the phasing addition circuit 104, and a pressure measurement unit 110 is provided in parallel therewith. . A strain and elastic modulus calculation unit 111, an elastic data processing unit 112, and a color scan converter 113 are provided following the displacement measurement unit 109 and the pressure measurement unit 110. The output side of the color scan converter 113 and the black and white scan converter 116 Is provided with a switching adder 114.

The operation of the RF signal frame data selection unit 108 according to this embodiment will be described with reference to FIG. FIG. 2 is a diagram illustrating an example of the RF signal frame data selection unit in FIG. The RF signal frame data selection unit 108 arbitrarily selects the number of frames going back in the past (the number of frame intervals with the current frame data) as one RF signal frame data serving as a reference for displacement measurement. That is, the RF signal frame data selection unit 108 sequentially secures in the frame memory 1081 the RF signal frame data sequentially output from the phasing addition circuit 104 over time at the frame rate of the ultrasonic diagnostic apparatus. The RF signal frame data selection unit 108 uses what is currently reserved in the frame memory 1081 as RF signal frame data Q. The RF signal frame data selection unit 108 temporally stores past RF signal frame data Q- 1, Q- 2, Q- 3,..., Q- M according to a control command from the control unit 200 of the ultrasonic diagnostic apparatus. One RF signal frame data is selected from the above, and it is temporarily stored in the RF signal frame data selection circuit 1082 as RF signal frame data R. The RF signal frame data selection unit 108 measures the displacement of the latest RF signal frame data Q stored in the frame memory 1081 and the RF signal frame data R stored in the RF signal frame data selection circuit 1082 in parallel. Output to the unit 109.

That is, the RF signal frame data selection unit 108 first temporally converts the current RF signal frame data Q as the past RF signal frame data R constituting a set of RF signal frame data to be sent to the displacement measurement unit 109. Not only adjacent RF signal frame data Q- 1, but also RF signal frame data Q- M in which M frames (M = 1, 2, 3, ...) are thinned out as past RF signal frame data R is arbitrarily selected Is something that can be done. It should be noted that the frame interval number M (M = 1, 2, 3,...) Thinned out can be arbitrarily set / changed by the user interface of the ultrasonic diagnostic apparatus.

FIG. 3 is a diagram illustrating another embodiment of the RF signal frame data selection unit of FIG. The RF signal frame data selection unit 108 in FIG. 3 secures the RF signal frame data P acquired in a past time phase P in the frame memory 1081 in accordance with a control command from the control unit 200 of the ultrasonic diagnostic apparatus. The RF signal frame data selection circuit 1082 always refers to the RF signal frame data P secured in the frame memory 1081 as past RF signal frame data in an arbitrary time phase without updating. Therefore, the displacement measuring unit 109 receives a set of RF signal frame data composed of the currently secured RF signal frame data Q and RF signal frame data P. Settings such as whether to adopt the function shown in Fig. 3 and what timing to acquire the RF signal frame data P when it is adopted can be arbitrarily switched, set, and changed by the user interface of the ultrasound diagnostic apparatus. It is like that.

Multiple RF signal frames acquired during a series of pressurization or depressurization operations when the interval between past and present RF signal frame data Q and P constituting a set of RF signal frame data is limited to adjacent frames The pressurization amount or decompression amount given in the time interval between the RF signal frame data constituting the data set is sufficient for the pressurization amount or decompression amount (generally about 1%) suitable for rendering the elastic image data. You may not be able to reach it. On the other hand, by configuring the RF signal frame data selection unit as shown in FIGS. 2 and 3, the frame interval between the past and current RF signal frame data can be sufficiently increased, and the elastic frame It is possible to appropriately draw an elastic image based on data. This is particularly useful in ultrasonic testing where the physical or physical limitations of the subject prevent the pressurization or depressurization speed from being increased sufficiently during a series of pressurization or depressurization operations. .

  The displacement measuring unit 109 performs one-dimensional or two-dimensional correlation processing based on a set of RF signal frame data selected by the RF signal frame data selecting unit 108, and a displacement or movement vector ( Measuring the direction and magnitude of the displacement). As a method for detecting the movement vector, for example, there are a block matching method and a gradient method as described in Patent Document 1. The block matching method divides an image into blocks of N × N pixels, for example, searches the previous frame for the block closest to the block of interest in the current frame, and performs predictive coding with reference to this block Is.

  The pressure measurement unit 110 measures or estimates the pressure in the body cavity of the diagnosis site of the subject 100. This ultrasonic diagnostic apparatus performs transmission / reception of ultrasonic waves under the control of the control unit 200 using the ultrasonic probe 101 provided in the probe head 1011, while adding to the probe provided in the probe head 1011. A method is adopted in which pressure is applied or reduced by the pressure device 115 to give a stress distribution in the body cavity of the diagnosis site of the subject 100. In this method, in order to measure how much pressure is applied between the probe head 1011 and the subject 100, for example, as shown in FIG. 4, a pressure for detecting the pressure applied to the rod-shaped member is detected. The sensor 1012 is attached to the side surface of the probe head 1011, the pressure between the probe head 1011 and the subject 100 is measured at an arbitrary time phase, and the measured pressure value is sent to the strain and elastic modulus calculation unit 111. It is supposed to be. In FIG. 4, the pressurizer 115 that pressurizes and depressurizes the probe head 1011 is omitted.

  The strain and elastic modulus calculation unit 111 calculates the distortion and elastic modulus of each point on the tomogram based on the movement amount (displacement) and the pressure output from the displacement measurement unit 109 and the pressure measurement unit 110, respectively. Alternatively, elastic modulus numerical data (elastic frame data) is generated and output to the elastic data processing unit 112. The calculation of the strain performed by the strain and elastic modulus calculation unit 111 is calculated, for example, without requiring pressure data and spatially differentiating the displacement. The calculation of the Young's modulus, which is one of the elastic moduli, is calculated by dividing the change in pressure by the change in moving amount.

  FIG. 5 is a diagram illustrating an example of the operation of the elasticity data processing unit of FIG. The elastic data processing unit 112 sequentially secures the elastic frame data X sequentially input from the strain and elastic modulus calculation unit 111 with time in the frame memory 1121. The elastic data processing unit 112 sets the elastic frame data currently secured in the frame memory 1121 as the elastic frame data N. Therefore, the elastic frame data is stored in the frame memory 1121 over time in the order of N, N-1, N-2,. In accordance with a control command from the control unit 200 of the ultrasonic diagnostic apparatus, the addition average processing circuit 1122 stores elastic frame data for M frames in order from the closest elastic frame data secured in the frame memory 1121 to the present time. Select. The averaging circuit 1122 is based on the current elastic frame data N selected from the frame memory 1121 and the elastic frame data N-1, N-2,. Addition averaging processing of the same coordinate data points is performed. The elastic frame data obtained by this averaging process is sent to the color scan converter 113 as the current elastic frame data Y. Note that the number M of past elastic frame data selected in the elastic frame data addition averaging process and the adoption of the elastic frame data addition averaging processing function can be arbitrarily set / changed in the user interface of the ultrasonic diagnostic apparatus. It is like that.

ここで、指標i，jは、各フレームデータの座標を表す。
一連の加圧もしくは減圧操作の過程の間に、加圧もしくは減圧の速度が時間的に一定であっても、対象を垂直方向に均等に加圧できている時相ばかりあるとは限らず、斜め方向に不均等に加圧もしくは減圧してしまう時相が生じ、対象物内の応力分布の時間的変化を不連続にしてしまう時相が生じ得る。演算された弾性フレームデータをそのままカラースキャンコンバータ113に送出した場合、このような時相においては、時間軸方向の1連の弾性フレームデータ(歪みデータ)の中に応力分布の時間的変化に不連続な飛びのある座標領域が生じるため、弾性画像としても、時間的に不連続な飛びのある領域をノイズとして含む映像となり画像診断を困難なものとすることがある。この実施の形態による弾性データ処理部における加算平均処理回路1122は、時間軸方向の弾性フレームデータの間での加算平均処理を行うことにより、時間的に不連続な飛びのある領域を連続的になるように緩和することができ、これによってノイズを低減することができる。 The above operation can be expressed by the following formula.

Here, the indices i and j represent the coordinates of each frame data.
Even if the pressurization or decompression speed is constant over time during a series of pressurization or decompression operations, there is not always a time phase in which the subject can be evenly pressurized in the vertical direction. A time phase in which pressure is applied or reduced in an uneven manner in an oblique direction is generated, and a time phase in which a temporal change in stress distribution in the object is discontinuous may occur. When the calculated elastic frame data is sent to the color scan converter 113 as it is, in such a time phase, the time series of elastic frame data (strain data) in the time axis direction is not affected by temporal changes in the stress distribution. Since coordinate regions with continuous jumps are generated, even an elastic image may be an image including a temporally discontinuous jump region as noise, which may make image diagnosis difficult. The addition average processing circuit 1122 in the elastic data processing unit according to this embodiment performs an addition averaging process between the elastic frame data in the time axis direction, thereby continuously generating regions with temporally discontinuous jumps. So that the noise can be reduced.

ここで、指標i，jは、各フレームデータの座標を表し、また、上記A，B，Cはそれぞれある定数を示す。特に、上式における定数A、B、Cの値の組合せと圧縮処理機能の採否は、超音波診断装置のユーザーインターフェイスにおいて任意に設定・変更できるようになっている。 FIG. 6 is a diagram showing another embodiment of the operation of the elasticity data processing unit of FIG. The elastic data processing unit 112 of this embodiment performs logarithmic transformation on input elastic frame data. The elastic data processing unit 112 secures the elastic frame data X output one after another from the strain and elastic modulus calculation unit 111 in the frame memory 1123, and the compression processing circuit 1124 uses the control unit 200 of the ultrasonic diagnostic apparatus. The logarithmic conversion of the data is performed according to the correspondence between the elastic frame data reflecting the instruction of the control command from the elastic image data, and the converted elastic frame data is sent to the color scan converter 113 as the elastic frame data Y. To do. The logarithmic processing performed by the elastic data processing unit 112 in FIG. 6 is expressed as (elastic frame data X) i, j, and output elastic frame data as (elastic frame data Y) i, j. Is represented by the following equation.

Here, the indices i and j represent the coordinates of each frame data, and the above A, B, and C represent certain constants. In particular, the combination of the values of the constants A, B, and C in the above formula and the adoption of the compression processing function can be arbitrarily set / changed in the user interface of the ultrasonic diagnostic apparatus.

  In particular, in image diagnosis using an elastic image, there is a great significance in clearly detecting a curable part suspected of being a cancer tissue, and it is important that a hard region can be highlighted and drawn. As a property of living tissue, for example, in the mammary gland region, there is a report that the difference in hardness between adipose tissue and cancer tissue is several tens of times (T.A.Krouskopet al, Ultrasonic Imaging, 1998). However, in the elastic imaging of the elastic frame data in the hue information conversion means or the monochrome luminance information conversion means by the existing ultrasonic diagnostic apparatus, each value of the elastic frame data and each value of the elastic image data have a linear relationship. Therefore, when the difference in the hardness of these tissues is depicted on the same elastic image, no matter which area of the elastic frame data is selected as the imaging area, the hardness between the soft area and the hard area is 2 The spatial change process can be depicted only in a linear relationship, and it is difficult to grasp the hard region as an outline of the hardened portion. In other words, only two areas, an extremely soft area and an extremely hard area, are projected and drawn, and it becomes a binarized image, and the process of changing the large hardness from the soft area to the hard area is displayed as hue information. Or it was difficult to express appropriately as monochrome luminance information. Therefore, it may be difficult to determine the size of the cured cancer tissue as an elastic image diagnosis, but by using the compression processing circuit 1124 in the elastic data processing unit 112 as in the above-described embodiment, As shown in FIG. 7, in the input elastic frame data, the process of changing the coordinate space value of the region having a small value (the region of the hard portion) becomes sensitive elastic frame data, and the region having a large value ( The change process of the coordinate space value of the soft area is insensitive elastic frame data, and when elastic image data is generated based on the elastic frame data output from the elastic data processing unit 112, the hard area is emphasized. Thus, it becomes easy to grasp the outline of the hardened portion.

  As the data conversion processing performed by the compression processing circuit 1124 of the elastic data processing unit 112 in FIG. 6, logarithmic conversion has been described as an example, but compression processing is performed using another conversion function having characteristics that achieve the above-described purpose. May be performed. For example, Y = A × (1−Exp (−B × X)) or the like may be used with A and B as constants. Also, several types of conversion functions may be prepared so that they can be arbitrarily set / changed on the user interface of the ultrasonic diagnostic apparatus. Further, for example, one conversion function may be configured by a plurality of curves as shown in FIG. In the function of FIG. 8, the intersection A may be arbitrarily set / changed up / down / left / right.

  FIG. 9 is a diagram showing still another embodiment of the operation of the elasticity data processing unit of FIG. The elasticity data processing unit 112 in FIG. 9 performs statistical processing on input elasticity frame data. In other words, the elastic data processing unit 112 in FIG. 9 secures the elastic frame data X output one after another from the strain and elastic modulus calculation unit 111 in the frame memory 1123 of the elastic data processing unit 112. The statistical processing circuit 1125 of the elastic data processing unit 112 performs the statistical processing of the elastic frame data in the coordinate region of the elastic frame data reflecting the instruction of the control command (statistical processing region information 1126) from the control unit 200 of the ultrasonic diagnostic apparatus. The upper limit value and the lower limit value of the elastic frame data selected as the range to be converted into the image data when the elastic image data is generated are determined based on the statistical feature value as a result, and the elastic frame The data Y, the upper limit value, and the lower limit value are sent to the color scan converter 113.

ただし、上式におけるΣは、超音波診断装置の制御部200からの制御命令である統計処理領域情報1126を反映した弾性フレームデータの座標領域におけるデータ要素の和を表す。 As the statistical feature quantity in the statistical processing circuit 1125 of FIG. 9, for example, an average value and a variance value may be obtained. When the input elastic frame data is represented as (elastic frame data X) i, j, the average value and The variance value is expressed by the following formula.

However, Σ in the above equation represents the sum of data elements in the coordinate region of the elastic frame data reflecting the statistical processing region information 1126 which is a control command from the control unit 200 of the ultrasonic diagnostic apparatus.

In addition, as the upper limit value and lower limit value of the elastic frame data to be selected as a range to be converted into image data when generating elastic image data,
(Upper limit value) = (Average value) + (Constant D) x (Dispersion value)
{Or (upper limit) = (constant D ') x (average value)}
(Lower limit value) = (Average value)-(Constant E) x (Dispersion value)
{Or (lower limit) = (constant E ') x (average value)}
The obtained upper limit value and lower limit value may be sent to the color scan converter 113. Further, the constant D or D ′ and E or E ′ may be arbitrarily set / changed in the user interface of the ultrasonic diagnostic apparatus. Further, only one of the upper limit value and the lower limit value may be set by the above equation, and the other may be set to a fixed value that does not reflect the statistical characteristics of the elastic frame data. For example, the lower limit value may be fixed at a distortion amount of 0%, and the upper limit value may be set as an average value + 2 × dispersion value.

  FIG. 10 is a diagram illustrating an example of the relationship between the temporal change in the pressurization / decompression rate and the acquisition timing of the RF signal. As is clear from FIG. 10, the elasticity calculated by the combination of the RF signal frame data S1 and the RF signal frame data S2 when the pressurization or decompression speed V fluctuates during a series of pressurization or decompression operations. E1 is the frame data, E2 is the elastic frame data calculated by the set of RF signal frame data S2 and RF signal frame data S3, and the elastic frame is calculated by the set of RF signal frame data S3 and RF signal frame data S4 The data is E3, the elastic frame data calculated by the combination of the RF signal frame data S4 and the RF signal frame data S5 is E4, and the statistical distribution (histogram) of the same coordinate area of each elastic frame data E1 to E4 is If the axis is the number of data elements and the horizontal axis is the amount of distortion, the pattern is drawn on the same scale as shown in FIG.

  As shown in FIG. 11, the elastic frame data E1 to E4 in the same region in the series of elastic frame data acquired in time series fluctuate with time. That is, if the pressure or pressure reduction speed fluctuates during a series of pressurization or decompression operations, the elasticity frame data in the same region in the series of elasticity frame data acquired in time series varies with time. It means to do. Elastic image conversion of elastic frame data in hue information conversion means or monochrome luminance information conversion means by a conventional ultrasonic diagnostic apparatus corresponds to each value of elastic frame data and each value of elastic image data being fixed one-to-one. Yes. For example, by using the upper and lower limits when optimized with the elastic frame data E2 as shown in FIG. 11, the upper and lower limits of the elastic frame data E1 to E4 in an arbitrary time phase are fixed, and the elastic image Data is being generated. In this case, in the time phase of the elastic frame data E3, a region where a relatively large strain is calculated becomes the over-saturated elastic image data EP3. Conversely, in the time phase of the elastic frame data E1, a relatively small strain is present. The calculated region becomes under-saturated elastic image data EP1, and it is possible to generate elastic image data EP2 with optimized gradation, at any time phase, as in the time phase when elastic frame data E2 was acquired. Not exclusively.

  As described above, the elastic imaging of the elastic frame data in the color scan converter by the conventional ultrasonic diagnostic apparatus is performed in the series of elastic image data acquired in time series according to the change in the pressurization or decompression speed. This makes the image diagnosis difficult because the image has a black and white luminance or hue variation in the same area. That is, in all time phases, the fixed correspondence relationship does not always optimize the contrast of the elastic image. In the statistical processing circuit in the elastic data processing unit according to this embodiment, when the pressurization or decompression speed V fluctuates during a series of pressurization or decompression operation processes as shown in FIG. , The elastic frame data is subjected to statistical processing, and an upper limit value and a lower limit value are set based on the statistical feature amount. For example, as shown in FIG. 12, (average value) ± (constant D) × (dispersion value) is calculated for elastic frame data of an arbitrary time phase. Here, the constant D is a common value in an arbitrary time phase.

  Statistically common upper and lower limits of elastic frame data in an arbitrary time phase obtained in this way are sent to the color scan converter, and elastic image data is generated in the range of the upper and lower limits. As a result, it is possible to generate elastic image data in which the elastic frame data elements are efficiently gradated in an arbitrary time phase as shown in FIG. According to the statistical processing circuit in the elastic data processing unit according to this embodiment, even when the pressurization or decompression speed fluctuates, the black and white luminance of the same region in the series of elastic image data acquired in time series or The variation in hue can be suppressed, and a temporally stable video can be provided, thereby making it easy to perform image diagnosis. That is, the ratio of the number of oversaturated pixels and the number of undersaturated pixels in the elastic image data can be normalized to a constant distribution curve in any time phase, and fluctuations in black and white luminance or hue are suppressed. You can get a video.

  In the above-described embodiment, as one operation of the RF signal frame data selection unit, a set of RF signal frame data is selected, and the number of frame intervals between the one set of RF signal frame data is variable. In addition, as an example of the operation in the elastic data processing unit, the case where the statistical processing circuit provided in the elastic data processing unit performs the statistical processing of the elastic frame data has been described. Next, a case where the RF signal frame data selection unit and the elasticity data processing unit operate in cooperation will be described.

  FIG. 13 is a diagram illustrating an example of an operation in which the RF signal frame data selection unit and the elasticity data processing unit cooperate with each other. First, in the RF signal frame data selection unit 108, information on the number of frame intervals (a current frame interval number information 131) between a set of RF signal frame data adopted when generating the current elastic frame data The data is sent to the frame interval optimization circuit 1127 of the data processing unit 112. Further, the statistical processing circuit 1125 of the elastic data processing unit 112 performs statistical processing of the current elastic frame data, and sends the information of the statistical feature amount as a result to the frame interval optimization circuit 1127. The frame interval optimization circuit 1127 is based on the current frame interval number information 131 output from the RF signal frame data selection circuit 1082 and the statistical feature value information of the current elastic frame data output from the statistical processing circuit 1125. Calculating the optimum number of frame intervals as the number of frame intervals between a set of RF signal frame data to be adopted when the next elastic frame data is generated, The next frame interval number information 132 is fed back to the frame data selection circuit 1082. The RF signal frame data selection circuit 1082 is adopted when the next elastic frame data is generated based on the optimum number of frame intervals (next frame interval number information 132) output from the frame interval optimization circuit 1127. Sets the number of frame intervals between a set of RF signal frame data.

このようにして求められた最適なフレーム間隔数に最も近い自然数が次回の弾性フレームデータを生成する1組のRF信号フレームデータのフレーム間隔数の情報(次回フレーム間隔数情報132)として、RF信号フレーム選択回路1082に送出される。例えば、定数Aとして「1」を設定した場合、次回の弾性フレームデータにおける歪み量として約1％近くのものが得られるものと予測されるフレーム間隔数がRF信号フレーム選択部に送出されることになる。 An example of the operation of the frame interval optimization circuit 1127 will be described below. The number of frame intervals of the set of RF signal frame data that generates the elastic frame data for this time (the number of frame intervals for this time) and the statistical processing result of the elastic frame data for this time, the average distortion amount is the frame interval optimization circuit. The optimum number of frame intervals, which is input to 1127 and obtained when the constant A is in the range of 0.5 to 2.5, is obtained by the following equation.

The natural number closest to the optimum frame interval number obtained in this way is the RF signal as the frame interval number information (next frame interval number information 132) of one set of RF signal frame data that generates the next elastic frame data. It is sent to the frame selection circuit 1082. For example, when “1” is set as the constant A, the number of frame intervals that is expected to obtain a distortion amount of about 1% in the next elastic frame data is sent to the RF signal frame selector. become.

  The contrast resolution of hard and soft areas in diagnostic imaging using elastic images is largely dependent on the amount of pressure applied or reduced in the time interval between the acquisition of a set of RF signal frame data. As a result, it is said that an elastic image having the highest contrast resolution can be obtained in a range of a pressurization amount or a decompression amount that can give a strain amount of about 0.5% to 2.5%. When the RF signal frame data selection unit 108 and the frame interval optimization circuit 1127 of the elastic data processing unit 112 are configured in cooperation as in the embodiment shown in FIG. Even in the process of deviating greatly, instantaneously large or small, pressurized or depressurized, it can respond instantly by optimizing the number of frame intervals between a set of RF signal frame data, and contrast An elastic image with high resolution can be rendered stably in time.

  The color scan converter 113 is a combination of the elastic frame data output from the elastic data processing unit 112 and the command output from the control unit 200 of the ultrasonic diagnostic apparatus or the elastic frame data output from the elastic data processing unit 112. Hue information conversion means for inputting an upper limit value and a lower limit value as the tonal selection range and providing hue information such as red, green, and blue as elastic image data from the elastic frame data is provided. This hue information conversion means converts, for example, an area where a large distortion is measured in the elastic frame data output from the elastic data processing unit 112 into a red code in the elastic image data, and conversely, the distortion is measured with a small distortion. The area is converted into a blue code in the elastic image data. Further, the color scan converter 113 may be configured by the above-described black and white scan converter 106. In this case, the luminance is increased in the elastic image data in the region where the distortion is measured, and conversely, the luminance is decreased in the elastic image data in the region where the distortion is measured. In addition, the RF signal frame data selection unit 108 and an elastic data processing unit configured by combining a plurality of elastic data processing units each acting differently as shown in FIG. 5, FIG. 6, FIG. 9 or FIG. Elastic image data may be generated using the color scan converter 113.

  Further, the switching adder 114 inputs black and white tomographic image data from the black and white scan converter 106 and color elastic image data from the color scan converter 113, and serves as means for adding or switching both images. Only tomographic image data or color elastic image data is output, or both image data are added and synthesized and output. For example, as described in Patent Document 2, a black and white tomographic image and a black or white elastic image by a color or black and white scan converter may be displayed simultaneously in a two-screen display. The image data output from the switching adder 114 is output to the image display 107.

  Next, the operation of the ultrasonic diagnostic apparatus configured as shown in FIG. 1 will be described. First, a high voltage electric pulse is applied to the ultrasonic probe 101 in contact with the body surface of the subject 100 by the transmission circuit 102 to emit an ultrasonic wave, and the reflected echo signal from the diagnostic site is ultrasonically probed. Received by child 101. This received signal is input to the receiving circuit 103 and preamplified, and then input to the phasing and adding circuit 104. The received signal whose phase is adjusted by the phasing / adding circuit 104 is subjected to signal processing such as compression / detection by the next signal processing unit 105 and then input to the monochrome scan converter 106. In the monochrome scan converter 106, the received signal is A / D converted and stored in a plurality of internal frame memories as a plurality of time-sequential tomographic image data.

  Next, among the RF signal frame data stored in the RF signal frame data selection unit 108, a plurality of RF signal frame data that are continuous in time series are selected and output to the displacement measurement unit 109 for one-dimensional or two-dimensional Displacement distribution is obtained. The displacement distribution is calculated by the block matching method, for example, as the above-described movement vector detection method. Needless to say, this method need not be particularly used, but it is generally used for the same two image data. The displacement may be calculated by calculating the autocorrelation in the region.

  On the other hand, the pressure measurement unit 110 measures the pressure applied to the body surface by the pressure sensor 1012 and holds the measurement signal. The measurement signals of displacement ΔL and pressure ΔP output from the displacement measurement unit 109 and the pressure measurement unit 110 are input to the strain and elastic modulus calculation unit 111, and the strain is obtained by spatially differentiating ΔL (ΔL / ΔX). Calculated. In particular, among the elastic modulus, Young's modulus Ym is calculated by the following equation.

Ym = (ΔP) / (ΔL / L)
The elastic modulus at each point is obtained from the elastic modulus Ym thus obtained, and two-dimensional elastic image data is continuously obtained.

  The elastic frame data obtained in this way is input to the color scan converter 113 or the monochrome scan converter 106, and is converted into hue information or monochrome luminance information. Thereafter, the black and white tomographic image and the color elastic image are added and synthesized via the switching adder 114, or sent to the image display 107 without adding the black and white tomographic image and the black and white elastic image to display one image. A black and white tomographic image and a color elastic image are superimposed and displayed on the screen. Alternatively, the black and white tomographic image and the black and white elastic image may be displayed simultaneously on the same screen. Further, the black and white tomographic image is not limited to a general B image, and a tissue harmonic tomographic image that selects and visualizes a harmonic component of a received signal may be used. Similarly, a tissue Doppler image may be displayed instead of the black and white tomographic image, and other images displayed on the two screens may be selected by various combinations.

  The above-described elastic image formation has been described with respect to the case where elastic image data is generated after obtaining the strain or Young's modulus Ym of the living tissue. However, the present invention is not limited to this. The elastic modulus may be calculated using other parameters such as the parameter β, the piezoelastic coefficient Ep, and the incremental elastic coefficient Einc. (See Patent Document 1).

  In the embodiment shown in FIG. 1, the case where the ultrasonic probe is brought into contact with the body surface of the subject has been described. However, the present invention is not limited to this, and the transesophageal probe or the intravascular probe is used. The same applies to the case where a child is used. According to this embodiment, high reliability and stability of the ultrasonic diagnostic apparatus can be realized.

  100 test object, 101 ultrasonic probe, 1011 probe head, 1012 pressure sensor, 102 transmission circuit, 103 reception circuit, 104 phasing addition circuit, 105 signal processing unit, 106 monochrome scan converter, 107 image display , 108 RF signal frame data selection unit, 1081 frame memory, 1082 RF signal frame selection circuit, 109 displacement measurement unit, 110 pressure measurement unit, 111 strain and elastic modulus calculation unit, 112 elasticity data processing unit, 1121 frame memory, 1122 addition Average processing circuit, 1123 frame memory, 1124 compression processing circuit, 1125 statistical processing circuit, 1126 statistical processing area information, 1127 frame interval optimization circuit, 113 color scan converter, 114 switching adder, 115 pressurizer, 131 current frame interval Information, 132 Next frame interval number information, 200 Ultrasonic device control unit, 14 Displacement / strain conversion circuit, 15 Weaving strain distribution data, 16 Ultrasonic tomographic image probe Location memory, 17 strain elasticity image probe position memory, 18 image processing unit, 19 alignment circuit, 20 superimposed image data, 28 xyz stage, 29 xyz stage controller, 30 a threshold setting and determination unit

Claims (4)

An ultrasonic probe including a transducer that generates ultrasonic waves on a subject;
Ultrasonic transmission / reception means for transmitting / receiving ultrasonic waves;
Phasing and adding means for generating RF signal frame data based on the received ultrasound;
Storage means for sequentially storing a plurality of the RF signal frame data acquired in time series during a series of pressurization or decompression processes;
RF signal frame data selection means for making the frame interval between the latest RF signal frame data stored in the storage means and the past RF signal frame data variable to select,
Elastic data processing means for generating elastic frame data representing strain or elastic modulus based on a set of RF signal frame data selected by the RF signal frame data selecting means, and generating an elastic image;
Image display means for displaying the elastic image;
The ultrasonic diagnostic apparatus characterized in that the RF signal frame data selection means selects the frame interval based on information on a statistical feature amount of the elastic frame data.   The elasticity data processing means performs an addition averaging process between the same coordinate data points between the latest elasticity frame data and the elasticity frame data of several frames in the past, and the elasticity frame data after the addition averaging process 2. The ultrasonic diagnostic apparatus according to claim 1, further comprising addition averaging processing means for outputting as elastic frame data. The elastic data processing means compresses the generated elastic frame data in accordance with a compression method using logarithmic transformation, and the compression method and its adoption can be arbitrarily set / changed by a user interface. The ultrasonic diagnostic apparatus according to claim 1.   Signal processing means for generating tomographic frame data based on the acquired time-series RF signal frame data, and tomographic image conversion means for converting the time-series tomographic frame data generated by the signal processing means into a tomographic image The ultrasonic diagnostic apparatus according to claim 1, further comprising at least one of the tomographic image and the elasticity image.

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