JP3730147B2 - Ultrasonic diagnostic equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to image synthesis based on echo data obtained in a plurality of frames.
[0002]
[Prior art]
The ultrasonic diagnostic apparatus generates an ultrasonic image corresponding to the distribution of acoustic impedance in the subject. However, even in the same subject tissue, echoes with different intensities may be generated depending on the direction of the ultrasonic beam. For example, in the case where the tissue is composed of a fibrous material, the closer the orientation of the tissue fiber to the ultrasonic beam is to be parallel, the easier the ultrasonic wave penetrates the tissue and the echo intensity can be reduced.
[0003]
FIG. 4 is a schematic diagram for explaining this phenomenon. FIG. 4A shows that the ultrasonic beam is in the direction of the arrow 2 along the vertical direction of the drawing and that the scanning plane 4 of the ultrasonic beam is used. FIG. 3 shows a state in which a cross section of a blood vessel 6 that is an observation object is captured. FIG. 4B is an ultrasonic image obtained corresponding to FIG. 4A, and the black portion 8 indicates a portion having a high echo intensity. The blood vessel wall includes a fiber structure along its circumferential direction. Therefore, as shown in the figure, the echo intensity is strong in the upper and lower portions of the blood vessel wall that intersect at an angle close to a right angle with the ultrasonic beam. There is a problem in that the echo intensity becomes weak at the parallel side portions and the acoustic impedance distribution of the tissue is not accurately reflected.
[0004]
In order to solve this problem, conventionally, two ultrasonic images are formed by shifting the direction of the ultrasonic beam, and an image obtained by superimposing these two ultrasonic images is displayed. FIG. 5 and FIG. 6 are schematic diagrams for explaining ultrasonic image generation by this superposition synthesis. FIG. 5 is a schematic diagram illustrating scanning of an ultrasonic beam corresponding to two superimposed ultrasonic images. Each ultrasonic image is formed by moving the ultrasonic beam in the horizontal direction, but the scanning area 20 of the first frame shown in FIG. On the other hand, the scanning area 24 of the second frame shown in FIG. 4B is scanned with an inclined ultrasonic beam 26 transmitted obliquely downward to the right. FIG. 6 is a schematic diagram of the ultrasound image of the blood vessel shown in FIG. 4 (a), FIG. 6 (a) is an image obtained in the first frame shown in FIG. 5 (a), and FIG. FIG. 5B shows an image obtained by the second frame shown in FIG. 5B, and FIG. 6C shows an ultrasonic image obtained by superposing and combining the first frame and the second frame shown in FIGS. Yes. In the blood vessel images 30 and 32 obtained in the first frame and the second frame, the portions where the echo intensity is reduced when the ultrasonic beam is parallel to the tissue fiber are due to the difference in direction of the ultrasonic beams 22 and 26. Accordingly, the positions are shifted from each other. Therefore, in the blood vessel image 34 obtained by superposing and combining the blood vessel images 30 and 32 of the first frame and the second frame, the reduction in echo intensity due to the orientation of the tissue fibers is mitigated.
[0005]
[Problems to be solved by the invention]
FIG. 7 is a schematic diagram of an ultrasonic image for explaining the problems of the conventional technology. As shown in FIG. 5, the scanning area 20 of the first frame and the scanning area 24 of the second frame are shifted from each other, and when they are superimposed and combined, both scanning areas are completely overlapped as shown in FIG. Don't be. That is, the entire scanning region 40 including the scanning regions 20 and 24 is included only in the overlapping portion 42 where the scanning region 20 and the scanning region 24 overlap, the non-overlapping portion 44 included only in the scanning region 20, and the scanning region 24. It consists of a non-overlapping part 46. The non-overlapping parts 44 and 46 are images made up of pixel values of either the first frame or the second frame, whereas the overlapping part 42 adds and averages the pixel values of the first frame and the second frame. This is an image composed of values, and there is a problem in that the boundaries 50 and 52 between the non-overlapping portions 44 and 46 and the overlapping portion 42 are conspicuous, and the viewer may feel uncomfortable.
[0006]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an ultrasonic diagnostic apparatus capable of generating an ultrasonic tomographic image having a natural image quality without a conspicuous boundary of overlapping.
[0007]
[Means for Solving the Problems]
An ultrasonic diagnostic apparatus according to the present invention includes a transmission / reception unit that acquires echo data from a subject by scanning an ultrasonic beam, first echo data corresponding to a first scanning region, and a portion of the first scanning region. And superimposing the first echo data and the second echo data on the scanning control means for controlling the scanning by the transmitting / receiving means so as to obtain the second echo data corresponding to the overlapping second scanning area Image generating means for generating an ultrasonic tomographic image by combining the image generating means, wherein the image generating means includes the first echo data and the second echo at an overlapping portion of the first scanning area and the second scanning area. Data is weighted and added, and the weighting condition is gradually changed according to the distance from the boundary between the non-overlapping portion and the overlapping portion of the first scanning region and the second scanning region.
[0008]
According to the present invention, in the overlapping portion, an ultrasonic tomographic image is synthesized by performing a weighted average instead of a simple average of the first echo data and the second echo data. The weight is changed continuously or stepwise in relatively small steps depending on the distance from the boundary between the non-overlapping part and the overlapping part. Thereby, for example, in the vicinity of the boundary with the non-overlapping part consisting only of the first echo data among the overlapping parts, the weight of the first echo data is increased more than the second echo data, The difference in echo data is reduced, and the non-overlapping part and the overlapping part are smoothly connected.
[0009]
In another ultrasonic diagnostic apparatus according to the present invention, the image generating unit relates to weighted addition in the overlapping portion, and the non-overlapping portion adjacent to the boundary among the first echo data and the second echo data. The corresponding weight of one echo data is decreased as the distance from the boundary is increased, and conversely, the weight of the other echo data is increased.
[0010]
According to the present invention, the weight ratio between the first echo data and the second echo data of the overlapping portion is monotonously increased or decreased from the vicinity of the boundary of the overlapping portion toward the inner portion.
[0011]
In a preferred aspect of the present invention, the image generation means changes the weight within a predetermined width from the boundary of the overlapping portion.
[0012]
Another preferable aspect of the present invention is the ultrasonic diagnostic apparatus, wherein the image generation unit changes the weight over the entire overlapping portion.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings.
[0014]
[Embodiment 1]
This apparatus acquires the echo data of two frames by shifting the directions of the ultrasonic beams as described above, and displays an ultrasonic image obtained by superimposing these, and thereby, the tissue fibers in the blood vessel image or the like are displayed. This is intended to mitigate the drop in echo intensity due to orientation. For example, as shown in FIG. 5A, in the odd frame, echo data scanned by the ultrasonic beam 22 inclined obliquely to the lower left of a predetermined angle is generated, and in the even frame, FIG. As shown in FIG. 2, the scanning is performed by the ultrasonic beam 26 inclined obliquely downward to the right at a predetermined angle.
[0015]
FIG. 1 is a schematic block diagram of an ultrasonic diagnostic apparatus according to the present invention. In FIG. 1, a probe 60 is an ultrasonic probe that transmits ultrasonic pulses and receives echoes. The probe 60 has an array transducer, and the ultrasonic beam is scanned in the array direction and the direction of the ultrasound beam is changed by electronic control of the array transducer.
[0016]
The transmission circuit 62 outputs a transmission pulse delayed for each channel of the transducer array to the probe 60 according to control by a transmission / reception control circuit (not shown). The delay amount for each transducer is controlled so that the ultrasonic wave to be transmitted forms a beam, and is controlled according to the direction of the transmitted beam.
[0017]
On the other hand, the reception system includes a reception circuit 66, a DSC (Digital Scan Converter) 68, a frame memory 70, a weight determination unit 72, an arithmetic synthesis unit 74, and a display unit 76. Further, the weight determination unit 72 includes a left synthesis start point detection unit 80, a left synthesis weight calculation unit 82, a right synthesis end point detection unit 84, a right synthesis start point detection unit 86, a right synthesis weight calculation unit 88, an input switch 90, and a selector 92. It is configured to include.
[0018]
The receiving circuit 66 phasing-adds the received signals for each channel from the probe 60 according to control by the transmission / reception control circuit. The receiving circuit 66 converts the received signal from an analog signal to a digital signal, and outputs the received signal as an echo data string along the direction of the ultrasonic beam.
[0019]
The DSC 68 temporarily stores the echo data string along the ultrasonic beam output from the receiving circuit 66 in a built-in frame memory, and converts it into a signal corresponding to the scanning method of the display unit 76. In other words, the DSC 68 outputs a pixel value string along the horizontal scanning line.
[0020]
The frame memory 70 stores the echo data output from the DSC 68 for one frame.
[0021]
The weight determination unit 72 determines a parameter α related to the overlay synthesis of the odd frame and the even frame. Here, if the parameter α is defined as the weight of the echo data obtained from the scanning area 20 scanned with the ultrasonic beam tilted to the left, the echo obtained from the scanning area 24 scanned with the ultrasonic beam tilted to the right The weight of the data is given by (1-α). Detailed processing contents of the weight determination unit 72 will be described later.
[0022]
The arithmetic synthesis unit 74 uses the echo data of the most recent frame (referred to as the kth frame) stored in the DSC 68 and the echo data of the previous frame ((k−1) th frame) stored in the frame memory 70. Each is read out and synthesized by weighted addition based on the parameter α given from the weight determining unit 72 to generate an ultrasonic image signal.
[0023]
The display unit 76 displays an ultrasonic image on the screen based on the ultrasonic image signal output from the calculation / synthesis unit 74.
[0024]
Next, superposition synthesis by this apparatus will be described. FIG. 2 is a schematic diagram of an ultrasonic image for explaining the overlay synthesis of this apparatus. Similar to the prior art, the entire scanning area 40 including the scanning area 20 of the odd frame and the scanning area 24 of the even frame includes the overlapping portion 42 where the scanning area 20 and the scanning area 24 overlap, and the non-overlapping included only in the scanning area 20. It consists of a portion 44 and a non-overlapping portion 46 included only in the scanning region 24. In this apparatus, the overlapping portion 42 further includes a left composite region 100 having a horizontal width of a predetermined number of pixels from the boundary 50 with the non-overlapping portion 44 to the right and a predetermined number of pixels from the boundary 52 with the non-overlapping portion 46 to the left. Are divided into a right-side composite area 102 having a horizontal width and a central composite area 104 which is the remaining portion excluding them.
[0025]
The arithmetic synthesis unit 74 weights and adds echo data corresponding to each pixel read out sequentially from the DSC 68 and the frame memory 70 along the horizontal scanning line. Hereinafter, processing performed along the horizontal scanning line 110 will be described.
[0026]
The input switch 90 is configured so that the even frame echo data from the DSC 68 and the frame memory 70 is input to the left synthesis start point detection unit 80 and the odd frame echo data is input to the right synthesis end point detection unit 84. (Not shown). This is because the left composite area 100 is defined based on the left boundary of the scanning area 24 corresponding to even frames, and the right composite area 102 is defined based on the right boundary of the scanning areas 20 corresponding to odd frames. It is.
[0027]
Each pixel value on the horizontal scanning line 110 is read from the DSC 68 and the frame memory 70 in order from left to right along the horizontal scanning line 110. The left synthesis start point detection unit 80 compares the input pixel value of the even-numbered frame with a predetermined threshold value, and the corresponding pixel has a background area outside the scanning area 24 (for example, given a pixel value “0”) and the scanning area 24. And the pixel B at the left end of the left composite region 100 is detected. This pixel B becomes the start point of the left side synthesis in the horizontal scanning line 110 currently being processed, and the left side synthesis weight calculation unit 82 extends from here to the right end pixel C of the left side synthesis region 100 located to the right by a predetermined number of pixels m. α is calculated, and this is supplied to the calculation / synthesis unit 74 via the selector 92.
[0028]
The left composite weight calculation unit 82 determines α so that α = 1 in the pixel B and α = 0.5 in the pixel C, and changes between BCs in stages or in steps. For example, α can be determined so as to monotonously decrease between BCs by performing linear interpolation based on α at the pixels B and C.
[0029]
On the other hand, the right synthesis end point detection unit 84 compares the pixel value of the input odd frame with a predetermined threshold value, and the corresponding pixel is scanned with the background region outside the scanning region 20 (for example, the pixel value “0” is given). It is determined which of the region 20 belongs to, and the rightmost pixel E of the right composite region 102 is detected. This pixel E becomes the end point of the right-side composition in the horizontal scanning line 110 currently being processed. The right synthesis start point detection unit 86 calculates the position of the leftmost pixel D of the right synthesis area 102 that is located to the left by a predetermined number of pixels m from the pixel E. From this pixel D to pixel E, the right synthesis weight calculation unit 88 calculates the weight parameter α, which is supplied to the calculation synthesis unit 74 via the selector 92.
[0030]
The right composite weight calculation unit 88 determines α so that α = 0.5 in the pixel D and α = 0 in the pixel E, and changes between DEs in a stepwise or continuous step. For example, α can be determined so as to monotonously decrease between DEs by performing linear interpolation based on α at the pixel D and the pixel E.
[0031]
Until the right composite weight calculator 88 starts calculating α, the final α calculated by the left composite weight calculator 82 is held and used. That is, α = 0.5 is set between CDs belonging to the central composite area 104. The α can be held by the selector 92 or can be set by the calculation / synthesis unit 74.
[0032]
The arithmetic synthesis unit 74 does not perform weighted addition in the non-overlapping portions 44 and 46, and outputs odd frame echo data between ABs belonging to the non-overlapping portion 44, and even frame echo data between EFs belonging to the non-overlapping portion 46, respectively. It reads out from either the DSC 68 or the frame memory 70 and uses it as it is to generate an ultrasonic image signal. On the other hand, the arithmetic synthesis unit 74 weights and adds the echo data read from the DSC 68 and the frame memory 70 using the parameter α determined by the weight determination unit 72 between BEs belonging to the overlapping portion 42, and the addition result Is used to generate an ultrasonic image signal. Incidentally, if the echo data and the weighting parameters of the odd and even frames in a certain pixel belonging to the overlapping portion 42 are D _O , D _E and α, respectively, the calculation / synthesis unit 74 calculates the weighted addition value S corresponding to the pixel as follows. Calculate based on the formula.
[0033]
S = α · D _O + (1−α) · D _E
The above-described processing for one horizontal scanning line is performed for each horizontal scanning line, and one ultrasonic image is formed. As described above, the arithmetic synthesis unit 74 adds the odd frame and the even frame while changing the mutual weights in the left synthesis area 100 and the right synthesis area 102, so that the overlapping part 42 and the non-overlapping part adjacent thereto are added. 44 and 46 are smoothly connected, and an ultrasonic image in which the boundaries 50 and 52 are not conspicuous is obtained. Further, in the central synthesis region 104, odd frames and even frames formed by ultrasonic beams of different directions are synthesized with equal weights, and the reduction of echo intensity due to the orientation of tissue fibers such as blood vessels can be reduced. It is done.
[0034]
The input switching unit 90 is switched for each scanning period of one frame by the transmission circuit 62 and the receiving circuit 66, whereby one ultrasonic image is output from the arithmetic synthesis unit 74 for each scanning period. Is done. That is, when the frame memory 70 stores the (2k-1) th frame (that is, odd frame) and the DSC 68 stores the 2k frame (that is, even frame), the input switcher 90 detects the right side synthesis end point. In addition, the DSC 68 is connected to the unit 84 and the left composite start point detection unit 80, and one ultrasonic image is generated as described above. Then, when echo data for one new frame is obtained and the 2k frame (that is, even frame) is stored in the frame memory 70 and the (2k + 1) frame (that is, odd frame) is stored in the DSC 68, the input switcher 90 is switched, the frame memory 70 is connected to the left synthesis start point detection unit 80, and the DSC 68 is connected to the right synthesis end point detection unit 84, and the next one ultrasonic image is generated.
[0035]
A certain amount of time is required for the weight determination unit 72 to determine the parameter α. Correspondingly, the arithmetic synthesis unit 74 is configured to synchronize α given from the weight determination unit 72 with echo data read from the DSC 68 and the frame memory 70.
[0036]
[Embodiment 2]
The second embodiment of the present invention is an ultrasonic diagnostic apparatus in which the parameter α changes over the entire overlap region 42. The configuration of the weight determination unit is different from the apparatus of the first embodiment, but the other parts Basically have the same configuration. Hereinafter, the same parts as those of the first embodiment are denoted by the same reference numerals, and will be described with reference to FIGS. 1 and 2.
[0037]
When this apparatus generates an ultrasonic image signal along the horizontal scanning line 110 shown in FIG. 2, α is changed throughout the BEs belonging to the overlapping portion 42. FIG. 3 shows a weight determination unit 200 of the present apparatus, which replaces the weight determination unit 72 according to the first embodiment in FIG. The weight determination unit 200 includes a synthesis start point detection unit 202, a synthesis end point detection unit 204, a synthesis weight calculation unit 206, and an input switch 90.
[0038]
As in the first embodiment, when the scanning area 20 is scanned in the odd frame and the scanning area 24 is scanned in the even frame, the input switch 90 is configured to start the synthesis of the echo data of the even frame from the DSC 68 and the frame memory 70. Switching is performed so that the echo data of the odd frame is input to the detection unit 202 and input to the synthesis end point detection unit 204.
[0039]
Similar to the left synthesis start point detection unit 80, the synthesis start point detection unit 202 detects the pixel B on the horizontal scanning line 110 currently being processed. On the other hand, the synthesis end point detection unit 204 detects the pixel E in the same manner as the right side synthesis end point detection unit 84.
[0040]
The composite weight calculation unit 206 determines α to be α = 1 in the pixel B and α = 0 in the pixel E, and to change in a stepwise manner between BEs in a continuous or minute step. For example, α can be determined so as to monotonously decrease between BE by performing a linear interpolation calculation based on α in the pixel B and the pixel E.
[0041]
The arithmetic synthesis unit 74 generates an ultrasound image signal using the odd frame echo data between the ABs belonging to the non-overlapping portion 44 and the even frame echo data between the EFs belonging to the non-overlapping portion 46 as they are. On the other hand, the arithmetic synthesis unit 74 uses the parameter α determined by the weight determination unit 72 between BEs belonging to the overlapping portion 42 to synthesize an ultrasonic image signal by weighted addition with consecutive odd frames and even frames. Generate.
[0042]
In this apparatus, similarly to the apparatus of the first embodiment, the overlapping portion 42 and the non-overlapping portions 44 and 46 adjacent to the overlapping portion 42 are smoothly connected, and an ultrasonic image in which the boundaries 50 and 52 are not conspicuous is obtained. . In the overlapping portion 42, an odd frame and an even frame formed by ultrasonic beams of different directions are combined, and for example, a reduction in echo intensity due to the orientation of tissue fibers such as blood vessels can be mitigated.
[0043]
【The invention's effect】
For example, in order to mitigate a decrease in echo intensity due to the orientation of tissue fibers such as blood vessels, a plurality of scanning regions having overlapping portions and non-overlapping portions are superimposed and synthesized. According to the ultrasonic diagnostic apparatus, an ultrasonic image in which the boundary between the overlapping portion and the non-overlapping portion is not conspicuous is obtained, and the viewer's discomfort can be reduced.
[Brief description of the drawings]
FIG. 1 is a schematic block diagram of an ultrasonic diagnostic apparatus according to a first embodiment.
FIG. 2 is a schematic diagram of an ultrasonic image for explaining superposition synthesis by the ultrasonic diagnostic apparatus according to the present invention.
FIG. 3 is a schematic block diagram of a weight determination unit of an ultrasonic diagnostic apparatus according to a second embodiment.
FIG. 4 is a schematic diagram for explaining a decrease and decrease in echo intensity that may occur when the tissue is composed of a fibrous material.
FIG. 5 is a schematic diagram showing scanning of an ultrasonic beam corresponding to two ultrasonic images to be superimposed.
6 is a schematic diagram of an ultrasound image of a blood vessel obtained corresponding to each scanning region shown in FIG.
FIG. 7 is a schematic diagram of an ultrasonic image for explaining problems of the conventional technology.
[Explanation of symbols]
60 probe, 62 transmitter circuit, 66 receiver circuit, 68 DSC, 70 frame memory, 72,200 weight determination unit, 74 arithmetic synthesis unit, 76 display unit, 80 left synthesis start point detection unit, 82 left synthesis weight computation unit, 84 right side Synthesis end point detection unit, 86 Right side synthesis start point detection unit, 88 Right side synthesis weight calculation unit, 90 Input switching unit, 92 Selector, 202 Synthesis start point detection unit, 204 Synthesis end point detection unit, 206 Synthesis weight calculation unit

Claims (5)

A transmission / reception means for acquiring echo data from a subject by scanning an ultrasonic beam;
Control the scanning by the wave transmitting / receiving means so as to acquire first echo data corresponding to the first scanning area and second echo data corresponding to the second scanning area partially overlapping the first scanning area. Scanning control means for
Weight determining means for determining weighting conditions for superimposing and combining the first echo data and the second echo data based on pixel data sequentially read out along a horizontal scanning line;
Image generating means for generating an ultrasonic tomographic image by superposing and synthesizing the first echo data and the second echo data according to the determined weighting condition;
Have
In the overlapping portion between the first scanning region and the second scanning region, the first echo data and the second echo data are weighted and added, and the overlapping portion between the first scanning region and the second scanning region is overlapped with the overlapping portion. The weighting condition is gradually changed according to the distance from the boundary with the part.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The weight determination means compares pixel data corresponding to the second scanning area sequentially read along a horizontal scanning line in a processing direction from the first scanning area toward the second scanning area with a predetermined threshold value. Detecting the start point of the first synthesis region and gradually changing the weighting condition from the start point to a position advanced by a predetermined number of pixels in the processing direction along the horizontal scanning line;
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 2,
The weight determination unit detects an end point of the second synthesis region by comparing pixel data corresponding to the first scanning region sequentially read along the horizontal scanning line in the processing direction with a predetermined threshold, and the end point The weighting condition is gradually changed from a position along the horizontal scanning line to a position advanced by a predetermined number of pixels in a direction opposite to the processing direction.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 3.
The weight determination means relates to weighting conditions in the first synthesis region and the second synthesis region, and one echo data corresponding to the non-overlapping portion adjacent to the boundary among the first echo data and the second echo data. Decreases with increasing distance from the boundary, and conversely increases the weight of the echo data.
An ultrasonic diagnostic apparatus. The ultrasonic diagnostic apparatus according to claim 1,
The weight determination means relates to a weighting condition in the overlapping portion, and sets the weight of one echo data corresponding to the non-overlapping portion adjacent to the boundary among the first echo data and the second echo data from the boundary. Decreasing with increasing distance, conversely increasing the weight of the other echo data, changing the weight throughout the overlap,
An ultrasonic diagnostic apparatus.

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