JP3524222B2 - Ultrasound diagnostic equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic diagnostic apparatus, and more particularly to control of transmission / reception timing when a starting point of an ultrasonic beam to be rotationally scanned does not coincide with its rotation center (a center offset is present).

[0002]

2. Description of the Related Art In an ultrasonic diagnostic apparatus, an ultrasonic beam is scanned by scanning a transducer, thereby forming a two-dimensional scanning surface. Examples of the ultrasonic beam scanning method include radial scanning in which the ultrasonic beam is continuously rotated and sector scanning in which the ultrasonic beam is reciprocally scanned in an arc within a certain angle range. The scanning methods include mechanical scanning in which a transducer is mechanically scanned and electronic scanning in which ultrasonic transducers are scanned by switching control of a plurality of transducers.

When radial scanning or sector scanning is performed, echo data is sequentially acquired along the ultrasonic beam in each direction. Each echo data is specified by θ coordinate indicating the azimuth address of the ultrasonic beam and R coordinate indicating the distance from the starting point of the ultrasonic beam. On the other hand, each pixel address on the display screen is specified by the X coordinate and the Y coordinate according to the scanning line. Therefore, in order to display the echo data as an image, it is necessary to convert the echo data from the polar coordinate (R-θ coordinate) format to the rectangular coordinate (XY coordinate) format.

FIG. 6 shows the principle of coordinate conversion in a DSC (digital scan converter) provided in a conventional ultrasonic diagnostic apparatus. Received signal (echo data)
Is converted into a digital signal by an A / D converter, and the echo data is sequentially stored in the echo data memory 10 for each ultrasonic beam in each direction. On the echo data memory 10, the storage address of each echo data is specified by the θ address and the R address. On the other hand, in the display memory 12, the echo data is stored as an image of the display screen, that is, according to the X address and the Y address.

Therefore, when transferring the echo data from the echo data memory 10 to the display memory 12, R-θ
A coordinate conversion 16 from address to XY address is required. Methods of coordinate conversion in this case include a method of sequentially executing arithmetic expressions and a method of using a ROM table. As a method of reading / writing the echo data, a method of sequentially reading the echo data from the first address of the echo data memory 10, specifying a corresponding XY address, and writing to that address, or a writing side. Addresses are sequentially generated from the beginning of the XY address of the display memory 12, and an R-θ address corresponding to the XY address is obtained by coordinate conversion (reverse conversion), and echo data of the obtained R-θ address is obtained. Is read out and written in the corresponding address of the display memory 12. The latter method is disclosed in JP-A-6-105849. In any case, thereafter, the echo data is read from the display memory 12 and displayed on the display.

By the way, when the above-described radial scanning or sector scanning is performed, the ultrasonic wave transmitting / receiving surface of the transducer and the center of rotation of the transducer do not usually coincide with each other. That is, the starting point of each ultrasonic beam is in a state of being separated from the center of rotation (center offset state).

FIG. 7 shows a case where a plus side center offset occurs, and FIG. 8 shows a case where a minus side center offset occurs.

In the side view of FIG. 7 (A), an ultrasonic probe 18 is an ultrasonic probe that is inserted into a body cavity (for example, a blood vessel or an esophagus), and a transducer 20 is provided at the tip thereof. Are arranged. In this case, by rotating only the ultrasonic probe 18 itself or the transducer 20, the ultrasonic beam 21
Is rotationally scanned. Here, the wave transmission / reception surface of the vibrator 20 is separated from the center of rotation by a constant distance (center offset amount) T. The center offset amount varies depending on the thickness of the transducer based on the frequency of the ultrasonic wave used and the structure of the ultrasonic probe.

As shown in the schematic front view of FIG.
The rotation orbit 22 of the wave transmission / reception surface of the vibrator 20 is a circle having a radius T centered on the rotation center 24. That is, when viewed from the center of rotation 24, the starting point of the ultrasonic beam 21 is located in the front (plus side).

Further, in the side view of FIG. 8A, the ultrasonic probe 26 is an ultrasonic probe similar to the ultrasonic probe 18, but a so-called ultrasonic reflection method is adopted. Has been done. That is, the ultrasonic reflecting mirror 30 having a reflecting surface inclined at 45 degrees is arranged in front of the vibrator 28, and the ultrasonic beam 29 is rotated by rotating the ultrasonic probe 26 itself or the ultrasonic reflecting mirror 30. Is rotationally scanned. As shown in the schematic front view of FIG. 8B, in this case, the center offset amount is the distance between the virtual rotation track 31 of the radius T and the rotation center 32 when the ultrasonic reflector 30 is not provided. Is defined as That is, when viewed from the rotation center 32, the starting point of the ultrasonic beam 29 is located rearward (minus side).

Conventionally, when there is a minus or plus center offset as described above, when echo data is written to the echo data memory 10 in FIG.
At the position of address "0" in each azimuth direction, the first echo data from the vicinity of the wave transmission / reception surface of the transducer is always written. Then, when the echo data is read from the echo data memory 10 and the coordinate data is directly converted when the echo data is written to the display memory 12 to form an image, the origins of the respective directions do not match and the image is distorted. Will end up. Therefore, it is necessary to perform the coordinate conversion in consideration of the center offset amount. That is, as shown as an image on the display memory 12 in FIG.
For example, in the case of the plus center offset shown in FIG. 7, it is necessary to set a circle having a radius T as the center and perform coordinate conversion so that the origin addresses of the respective directions are aligned on the circle.
In addition, for example, data having a brightness value of 0 is written in a circle having a center radius T.

The above center offset correction is performed by referring to FIG.
It is not limited to the same radial scanning as shown in FIG. 9A, but is also necessary in the sector scanning of FIG.

In the conventional apparatus, an arithmetic expression for specifying the address of the echo data memory from the address of the display memory will be described for reference.

FIG. 10 shows the correspondence between display points (pixels) in a display image and sample points (echo data) obtained by transmitting and receiving ultrasonic waves.
As shown in FIG. 10, the address (x, y) of the display memory is now changed to the address (R,
In order to obtain the “R” address of θ), the following first equation is calculated.

[0015]

[Equation 1] Here, the above "D" corresponds to the conversion rate related to zooming, and indicates the ratio of the display matrix size (XY address unit) and the display depth (R address unit). Specifically, it is defined by the following second equation.

[0016]

[Equation 2] In the above second formula, “M” indicates the number of pixels of the image display matrix. In the above formula 1 and formula 2,
“OFS” indicates the center offset amount in units of R addresses, and is specifically defined by the following third formula. In the above second formula, "TSC" is the total number of samples of the ultrasonic beam to be displayed.

[0017]

[Equation 3] In the above third formula, “fs” indicates the sampling frequency of the received signal. “V” indicates the speed of sound of ultrasonic waves in the living body. “T” is the above center offset amount (m
m) is shown.

From the above first equation, it is understood that the R address changes nonlinearly with respect to the center offset amount.

[0019]

According to the method of performing coordinate conversion by sequentially executing the above-mentioned arithmetic expressions, the first method described above is used.
As can be understood from the equations to the third equation, since the center offset is treated as a parameter in the arithmetic expression, even if the ultrasonic probe is replaced and the center offset amount is different, the arithmetic operation is performed. Since it suffices to change the center offset condition in the formula, it is possible to relatively flexibly cope with such various kinds of condition changes.

However, since a complicated arithmetic structure is required, the cost of the apparatus is increased, and the calculation takes time, so that there is a problem that the frame rate is lowered and the real time property is lowered.

On the other hand, according to the method using the conversion table composed of the ROM or the like, only the result of the coordinate conversion needs to be extracted in advance, and the circuit configuration is simple and the cost of the device can be reduced. There is an advantage that can be achieved.

However, it is necessary to prepare a conversion table for each center offset amount of the usable ultrasonic probe, and it is also necessary to prepare a conversion table for each sampling rate that can be supplied to the A / D converter. That is, since it is necessary to prepare a conversion table for each combination of various conditions, it is difficult to flexibly respond to changes in various conditions, and in that sense, the cost of the device cannot be reduced. There is.

The present invention has been made in view of the above conventional problems, and an object thereof is to change the center offset amount of the ultrasonic probe or to change the sampling rate of the A / D converter. Also, it is an object of the present invention to provide an ultrasonic diagnostic apparatus that does not require switching of a conversion table or the like for coordinate conversion for that purpose.

Another object of the present invention is to provide an ultrasonic diagnostic apparatus capable of changing the display magnification with a simple structure.

[0025]

In order to achieve the above object, the present invention provides an ultrasonic probe in which an ultrasonic beam is rotationally scanned and an echo in which a received signal from the ultrasonic probe is stored. The writing of the reception signal to the echo data memory is controlled according to the data memory and the center offset amount between the rotation center of the ultrasonic beam and the start point of the ultrasonic beam corresponding to the transmitting / receiving surface of the transducer. Means,
Center offset correction type write control means for starting the writing of the received signal in each azimuth direction from the time corresponding to the center of rotation, and the echo data read from the echo data memory from the XY coordinate system from the XY coordinate system. A coordinate conversion means for coordinate conversion into a system, a display memory in which the echo data after the coordinate conversion is stored, and a display means for displaying the data read from the display memory are included. .

According to the above arrangement, the received signal from the ultrasonic probe is written in the echo data memory under the write control of the center offset correction type write control means.
In this case, the center offset correction type writing control means
The writing of the reception signal in each azimuth direction is started from the time corresponding to the center of rotation of the vibrator. That is, when the data is stored in the echo data memory, the data corresponding to the plus or minus center offset is added or deleted, so that it is not necessary to consider the center offset in the subsequent data processing. The echo data read from the echo data memory is written to the corresponding address in the display memory after coordinate conversion, but since it is not necessary to consider the center offset in the coordinate conversion, for example, change the center offset in the coordinate conversion table. No need to switch for. That is, basically, one coordinate conversion table can cope with various center offsets. Therefore, for example, many coordinate conversion ROMs
Since there is no need to prepare such as, the configuration can be simplified.

In a preferred aspect of the present invention, in the ultrasonic probe, a transducer is arranged in front of the center of rotation. In this case, the center offset correction type write control means starts writing the reception signal from a time point before the transmission time point and corresponding to the rotation center.

As the ultrasonic probe, for example, an ultrasonic probe having an oscillator that continuously rotates while facing the ultrasonic wave transmitting / receiving surface on the side opposite to the center of rotation is used. In this case, the ultrasonic probe radially scans the ultrasonic beam. Further, as the above-mentioned ultrasonic probe, an ultrasonic probe having an oscillator that is oscillated in an arc shape with the ultrasonic wave transmitting / receiving surface facing the opposite side of the rotation center is used. In this case, the ultrasonic probe is sector-scanned by the ultrasonic beam.

Further, in a preferred aspect of the present invention, in the ultrasonic probe, a transducer is arranged behind or behind the center of rotation. In this case, the center offset correction type write control means starts data writing from a time point after the transmission time point and corresponding to the rotation center.

As the ultrasonic probe, a transducer that emits ultrasonic waves along the central axis of the probe and an ultrasonic wave that is reflected from the transducer are reflected in a direction orthogonal to the central axis. And an ultrasonic reflector that bends the acoustic beam. In this case, the rotation center is set on the ultrasonic reflecting mirror and the ultrasonic beam is radially scanned.

As described above, the present invention is effective for a scanning method in which a center offset occurs such as radial scanning or sector scanning, and the center is adjusted only by adjusting the relationship between the transmission timing and the reception signal writing timing. The non-linear parameter in the coordinate transformation called offset can be eliminated.

In a preferred aspect of the present invention, the center offset correction type write control means includes a beam address counter for generating a θ address corresponding to the azimuth direction of the ultrasonic beam, and R of each data in each ultrasonic beam.
A means for generating an address, a sample counter for generating the R address with the rotation center as an address initial value, and a center offset correction for setting a sampling start time point corresponding to the rotation center according to the center offset amount. And a circuit.

Further, in a preferred aspect of the present invention, the received signal is provided in the preceding stage of the echo data memory.
An A / D conversion circuit that performs / D conversion and a sampling clock generator that supplies a sampling clock to the A / D conversion circuit are provided. Then, the sample counter counts the sampling clock from the sampling start time set by the center offset correction circuit.

In the above configuration, the beam address counter counts the pulse indicating the beam number output from the transmitting / receiving circuit and outputs the beam address data indicating the θ address to the echo data memory. The sample counter counts the sampling pulses of the A / D converter after the center offset correction circuit allows the start of sampling, and outputs the sample count data indicating the R address to the echo data memory.
The center offset correction circuit adjusts the timing of the transmission trigger pulse and the writing timing of the reception signal based on the center offset amount peculiar to the ultrasonic probe, that is, the reception signal is written from the time corresponding to the rotation center. Let

When the reception signal is written before the transmission of the ultrasonic wave, a signal having substantially no echo is sampled. Therefore, the data in the section corresponding to the center offset is preferably set. It is fixed to a constant value (for example, 0). This makes it easier to view the displayed ultrasonic image.

In a preferred aspect of the present invention, there is provided a clock frequency switch for changing the frequency of the sampling clock. Even though the sampling frequency of the A / D converter is changed in this way, the center offset correction circuit adjusts the write timing so as to eliminate the center offset, and the sample counter does not write after the write is permitted. Start sampling clock counting.

That is, according to the present invention, since the center offset correction is performed before the storage in the echo data memory, it is not necessary to switch the coordinate conversion calculation formula and the coordinate conversion table in response to the change of the sampling clock. .

In a preferred aspect of the present invention, the coordinate conversion means is composed of a coordinate conversion table storing a coordinate conversion calculation result when the center offset is 0.

Further, in a preferred aspect of the present invention, the coordinate conversion means has a plurality of coordinate conversion tables selected according to a display magnification, and the display magnification is changed by switching the coordinate conversion tables. That is, since the center offset correction is performed before storing in the echo data,
Regardless of such a center offset, the coordinate conversion table can be switched according to only the display magnification.

In a preferred aspect of the present invention, means for determining the center offset amount of the probe used is provided.

When the center offset is corrected, T in the above third equation becomes 0 and OFS becomes 0, and the OFS term of the first equation is erased. Further, since the OFS term in the second equation also becomes 0, the D term in the first equation is simplified. Here, since the D term is a term corresponding to the display magnification, it is understood that the display magnification can be independently changed regardless of the center offset, and even in that case, image distortion does not occur.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a preferred embodiment of the ultrasonic diagnostic apparatus according to the present invention, and FIG. 1 is a block diagram showing the overall structure thereof.

2 and 3 show the principle of the present invention. First, the principle will be described with reference to FIGS.

FIG. 2 shows an example of the ultrasonic probe in which the plus center offset shown in FIG. 7 is generated. That is, the transducer 40 has its transmitting / receiving surface on the side opposite to the rotation center 42. It is rotated and scanned toward. The wave transmission / reception surface of the oscillator 40 rotates about the rotation center 42, and thereby a rotation orbit 44 is formed. In the present invention, when such a plus center offset occurs, the sample window signal 48 is sent prior to the transmission trigger pulse 46 in order to start writing the received signal to the echo data memory from the time corresponding to the rotation center 42. I'm starting up. That is, although the transmission trigger pulse 46 is generated at the start point of the ultrasonic beam 50, the echo data is written prior to the transmission trigger pulse 46. Specifically, the data is written ahead by the period t. By doing so, the center offset correction is performed before storage in the echo data memory. The sample window signal 48 is generated by a write control unit, which will be described later, and it indicates a writing period in the echo data memory.

As shown in FIG. 2B, in the echo data memory 52, unlike the prior art, the echo data is written ahead of the position of the transducer surface by the period t, that is, the center of rotation. The echo data is written from the time point corresponding to. This writing is performed for each data corresponding to one ultrasonic beam 50. Since noise may be sampled during the period t, it is desirable to set the echo data within the period t to a predetermined value (for example, 0).

FIG. 3 shows an ultrasonic probe having a minus center offset as shown in FIG.
In FIG. 3A, the oscillator 54 is rotationally scanned about a rotation center 56, and the wave transmission / reception surface thereof forms a rotation orbit 57. In the case of such a minus center offset, according to the present invention, the sample window signal 60 is raised with a delay of a predetermined period t corresponding to the center offset from the transmission trigger pulse 58, so that the time from the time point corresponding to the rotation center 56 is increased. Echo data is being written. That is, in the case of such a minus center offset, the echo data within the period t is eliminated, and thereby the center offset is corrected. In this case, since echo data within the period t is duplicately captured in each azimuth direction, even if the echo data within the period is eliminated, the necessary image information is not substantially reduced. .

Therefore, as shown in FIG. 3 (B), in the echo data memory 62, the echo data is written from the time corresponding to the center of rotation, so that the echo is corrected with the center offset corrected. Data is written.

Next, the ultrasonic diagnostic apparatus of this embodiment will be described with reference to FIG.

The probe 64 performs mechanical radial scanning and sector scanning, and for example, the ultrasonic probe shown in FIGS. 7 and 8 is used. In the present embodiment, a probe in which an ultrasonic beam is mechanically scanned is used, but the present invention is applied to a probe in which an ultrasonic beam is electronically scanned and a center offset occurs. It is also possible to apply.

The transmission / reception circuit 66 supplies a transmission signal to the probe 64 and performs a predetermined process such as amplification on the reception signal from the probe 64 to A / D the reception signal.
Output to the converter 68. Here, the A / D converter 68 is
Based on the sampling clock 200 output from the sampling clock generator 69, the received signal is converted from an analog signal to a digital signal. The echo data memory 70 is the echo data memory 5 shown in FIG.
This corresponds to the echo data memory 62 shown in FIGS. 2 and 3 and stores the echo data after the center offset correction under the control of the write control unit 72 described in detail later. Each echo data is stored for each ultrasonic beam. Ultrasonic image data to be displayed is stored in the display memory 71. Specifically, the address of each echo data is converted by the action of the address conversion unit 74, and specifically, from polar coordinates to orthogonal coordinates. The echo data after being converted to is stored. here,
The address conversion unit 74 converts the XY address generated by the XY address generator 76 into an R-θ address and outputs it. The XY address generator 76 sequentially generates the first address to the last address in the display memory 71. Therefore, the address conversion unit 74 sequentially generates the R-θ address corresponding to the XY address generated by the XY address generator 76, from the first address to the last address of the display memory 71. The echo data stored at each address is sequentially read from the echo data memory 70. In the present embodiment, this address conversion unit 74
Is composed of a coordinate conversion table including a ROM and the like.

As described above, in the present embodiment, the address conversion is performed based on the display memory 71, but of course the coordinate conversion may be performed from the beginning based on the echo data memory 70. Further, in the present embodiment, the address conversion unit 74 is configured by the coordinate conversion table, but it may be configured by a calculation unit having a calculation formula.

The read control unit 78 controls the read of the echo data from the display memory 71. The read echo data is converted into an analog signal in the D / A converter 80 and then displayed. Then, the ultrasonic image is displayed on the display 82. As is clear from the above description, the center image correction is properly performed on the ultrasonic image, and the image is not distorted. By the way, when plus center offset correction is performed and circular data is added to the center, the center part is displayed with the brightness set to 0, for example. The echo data memory 70, the write control unit 72, the display memory 7
1, the address converter 74, the XY address generator 76, and the read controller 78 constitute a DSC.

In FIG. 1, the write control unit 72 is for setting the sampling period of the reception signal output from the A / D converter 68, as described above, and the write control unit 72 has a center offset. It has a correction circuit 84. The transmission / reception timing generator 86 outputs the timing pulse 202 for the above center offset correction.

Next, the specific structure of the write controller 72 shown in FIG. 1 will be described with reference to FIG.

In FIG. 4, the received signal is converted into a digital signal in the A / D converter 68 as described above and stored in the echo data memory 70 via the data buffer 88.

The beam counter 90 provided in the writing control unit 72 counts the timing pulse 202 output from the transmission / reception timing generator 69 as described above, and outputs the address signal corresponding to the θ address to the echo data memory 70. Is output to. As described above, the sample counter 92 counts the sampling clock 200 for the A / D converter 68 output from the sampling clock generator 86, and outputs the R address data as the count value. However, the operation of the sample counter 92 is such that the sample window signal 2
The sampling clock 200 is counted only while the sample window signal 206 is rising. Here, the sample window signal 206 is the center offset correction circuit 84.
Created by.

In the synchronizing circuit 94 provided in the center offset correcting circuit 84, the above-mentioned timing pulse 2 is supplied.
02 and the sampling clock 200 are input, and the timing pulse 202 is output at the timing synchronized with the sampling clock 200. That is, this synchronizing circuit 94 is provided in order to synchronize the transmission timing with the reception timing for sample correction. Timing pulse 2 output from the synchronization circuit 94
08 is input to the trigger delay counter 96, and specifically, is input to the load terminal (LD) of the trigger delay counter 96. When this timing pulse 208 is input, the trigger delay counter 96
Reads data corresponding to the center offset amount from the R-delay setting register 98. The R-delay setting register 98 includes an offset amount setting signal 21
0 is input, and this offset amount setting signal 210
A proper center offset amount is selected by.

In the trigger delay counter 96, when the data corresponding to the center offset amount is set by the R-delay setting register 98, counting of clock pulses output from the delay counter clock generator 100 is started, and the count value thereof is started. The pulse (RCO) is output at the time when is equal to the set value. The output pulse of the trigger delay counter 96 is sent to the flip-flop 104 or the pulse generator 106 via the switch 102. Here, the switch 102 is switched by the trigger switch setting register 108, and the trigger setting register 108 switches between so-called post trigger and pre-trigger. Specifically, in the case of the plus center offset shown in FIG. 2, the transmission trigger pulse 2
To start writing the received signal before 04,
Timing pulse 208 is provided to flip-flop 104, causing sample window signal 206 to rise. At the same time, in the case of this plus center offset, the output pulse of the trigger delay counter 96 is output to the pulse generator 106 by the action of the switching device 102. That is, the transmission trigger pulse 204 is output when the count of the trigger delay counter 96 is completed. In short, in the case of plus center offset,
As shown in FIG. 2, the sample window signal 206 is raised before the output of the transmission trigger pulse 204 by a time corresponding to the center offset amount. The sample window signal 206 is the EN of the sample counter 92.
It is input to the terminal and the write enable terminal (WRITE ENB) of the echo data memory 70. That is,
The sample window signal 206 sets the operation period of the sample counter and the writing period of the echo data. When the R address reaches the upper limit in the sample counter 92, an RCO pulse is output from the sample counter 92, which resets the flip-flop 104. This causes the sample window signal 206 to fall.

On the other hand, in the case of the minus center offset as shown in FIG. 3, the trigger switching setting register 108
By the action of, the switch 102 is switched, that is, the timing pulse 208 is sent to the pulse generator 106 and is output as the transmission trigger pulse 204. Further, the output pulse from the trigger delay counter 96 is supplied to the flip-flop 104, which is used to raise the sample window signal 206. That is, in the case of this minus center offset, the transmission trigger pulse 20
After 4 is output first, the sample window signal 206 is started up with a delay corresponding to the center offset amount, whereby the center offset correction is executed.

An offset amount setting signal 210 is input to the trigger switching setting register 108, that is, a post trigger or a pre-trigger is determined from the data indicated by the offset amount setting signal 210, and the switching device 102 is switched. ing.

The timing pulse 208 from the synchronizing circuit 94 is input to the flip-flop 110 in FIG. 4, and the output of the flip-flop 110 is raised by the input of this timing pulse 208, and the operation of the trigger delay counter 96 is started. Permissible. When the output of the flip-flop 110 is in the high state, the data buffer 88 functions as a gate circuit and the value of the data input to the echo data memory 70 becomes zero.
That is, the value of the echo data in the period corresponding to the center offset is forcibly set to 0. When an output pulse is output from the trigger delay counter 96, the flip-flop 110 is reset and the data buffer 88 is
The passage of the received signal from the A / D converter 68 is allowed.

The trigger delay counter 96 is composed of, for example, a 12-bit binary counter, that is, it counts from 1 to 4096. In order to improve the accuracy of center offset correction, it is necessary to set the frequency of the clock output from the delay counter clock generator 100 higher than the frequency of the sampling clock 200 output from the sampling clock generator 86. . Now, when the frequency of the clock input to the trigger delay counter 96 is 30 MHz and the center offset is +0.3 mm, sampling of echo data is started as shown in the following fourth equation. After that, the count value from the generation of the transmission trigger signal is 12 counts.

[0064]

[Equation 4] That is, by transmitting the ultrasonic beam with a delay of 12 counts from the start point of the data sampling, the echo data memory 70 can store the echo data with the center offset correction. That is, the same echo data mapping as in the case where the center offset is 0 is performed on the echo data memory 70.

Similarly to the above, when the frequency of the clock from the delay counter clock generator 100 is 30 MHz and the center offset amount is -1.2 mm, the echo is generated after the transmission trigger signal is generated. The count value until the start of data sampling is 47 counts as shown in the following fifth formula.

[0066]

[Equation 5] That is, by starting data sampling with a delay of 47 counts after transmitting the ultrasonic beam, it is possible to perform the center offset correction and write the echo data as described above.

According to such center offset correction, processing such as coordinate conversion can be performed in the echo data memory 70 and thereafter without any consideration of the center offset, and even in that case, geometric distortion can be prevented. No ultrasound image can be constructed.

Therefore, according to this embodiment, various applications are possible as shown in FIG. In FIG. 5, the same components as those shown in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 5, the clock frequency switch 12
0 is for switching the frequency of the sampling clock generated by the sampling clock generator 69, and the sampling frequency can be switched in multiple stages or continuously by the clock frequency switching unit 120. That is, the sampling frequency in the A / D converter 68 can be switched. However, even if such a sampling frequency is switched,
As is apparent from the configuration of FIG. 4 described above, the center offset correction circuit 84 is not affected by the change in the sampling clock frequency, so that the center offset correction can be properly performed. In this case, since the sample counter 92 counts the sampling clock output from the sampling clock generator 86 from the time when the sample window signal 206 rises, an appropriate R address is generated according to the change of the sampling clock frequency. Can be made. The frequency of the sampling clock is appropriately set according to the resolution of the image, the frame rate, and the like.

In the embodiment shown in FIG. 5, the offset amount setting signal 210 is supplied from the offset amount judging circuit 122 to the center offset correcting circuit 84. The offset amount determination circuit 122 uses the probe identification signal 125.
Based on the above, the center offset amount is judged whether it is positive or negative, and the judgment result is output to the center offset correction circuit 84. As shown in FIG. 4, in the center offset correction circuit 84, the R-delay setting register 98 outputs data corresponding to the offset amount based on the offset amount setting signal 210, while the trigger switching setting register 108 , The operation of the switch 102 is switched depending on whether the center offset is a positive center offset or a negative center offset.

Further, in the embodiment shown in FIG. 5, a plurality of coordinate conversion tables are built in the address conversion unit 123. Each coordinate conversion table corresponds to a display magnification different from each other, that is, an ultrasonic image can be displayed at a desired display magnification by selecting one of the coordinate conversion tables by the conversion table switching unit 124. Becomes In this case, a zooming signal is supplied to the conversion table switching unit 124, and an appropriate coordinate conversion table is selected via the conversion table switching unit 124 according to the zooming signal.

[0072]

As described above, according to the present invention, even if the center offset amount of the ultrasonic probe is different or the sampling rate of the A / D converter is changed,
Since it is not necessary to switch the conversion table or the like for coordinate conversion, it is possible to perform an appropriate center offset correction while simplifying the configuration of the device. Further, according to the present invention, the display magnification can be changed only by switching the coordinate conversion table.

[Brief description of drawings]

FIG. 1 is a block diagram showing an overall configuration of an ultrasonic diagnostic apparatus according to the present invention.

FIG. 2 is a principle explanatory diagram showing sampling of echo data when a plus center offset occurs.

FIG. 3 is a principle explanatory diagram showing sampling of echo data when a minus center offset occurs.

FIG. 4 is a circuit diagram showing a specific configuration of a write controller.

FIG. 5 is a block diagram showing an application example of the present embodiment.

FIG. 6 is a diagram for explaining conventional coordinate conversion.

FIG. 7 is a diagram showing a cause of a plus center offset.

FIG. 8 is a diagram showing a cause of a minus center offset.

FIG. 9 is a diagram showing the concept of radial scanning and sector scanning.

FIG. 10 is a diagram showing display points and sample points.

[Explanation of symbols]

64 probe, 70 echo data memory, 71 display memory, 72 write control unit, 74 address conversion unit,
76 XY address generator, 90 beam counter, 9
2 sample counter, 96 trigger delay counter, 200 sampling clock, 202 transmission / reception timing signal, 206 sample window signal, 204
Transmit trigger pulse.

Claims (12)

(57) [Claims] 1. An ultrasonic probe in which an ultrasonic beam is rotationally scanned, an echo data memory in which a received signal from the ultrasonic probe is stored, a rotation center of the ultrasonic beam and a transducer. Means for controlling writing of a reception signal to the echo data memory according to a center offset amount between the ultrasonic wave beam starting point corresponding to the transmission / reception surface and each direction from the time point corresponding to the rotation center. Center offset correction type write control means for starting writing of a reception signal in a direction, and coordinate conversion means for coordinate conversion of echo data read from the echo data memory from an R-θ coordinate system to an XY coordinate system. And a display memory for storing the echo data after the coordinate conversion, and a display unit for displaying the data read from the display memory. Ultrasonic diagnostic apparatus. 2. The apparatus according to claim 1, wherein in the ultrasonic probe, a transducer is arranged in front of the center of rotation, and the center offset correction type write control means is provided before a transmission time point. An ultrasonic diagnostic apparatus characterized in that writing of a received signal is started from a time point corresponding to the center of rotation. 3. The ultrasonic probe according to claim 2, wherein the ultrasonic probe has a vibrator that continuously rotates with its ultrasonic wave transmitting / receiving surface facing the side opposite to the rotation center. The ultrasonic diagnostic apparatus is characterized in that an ultrasonic beam is radially scanned in the probe. 4. The apparatus according to claim 2, wherein the ultrasonic probe has a vibrator that is oscillated in an arc shape with the ultrasonic wave transmitting / receiving surface facing the side opposite to the rotation center. An ultrasonic diagnostic apparatus is characterized in that an ultrasonic beam is sector-scanned by an ultrasonic probe. 5. The apparatus according to claim 1, wherein in the ultrasonic probe, a transducer is arranged at a position behind or behind the rotation center, and the center offset correction type write control means is provided. The ultrasonic diagnostic apparatus is characterized in that data writing is started at a time point after the transmission time point and corresponding to the center of rotation. 6. The apparatus according to claim 5, wherein the ultrasonic probe is configured to emit an ultrasonic wave along a central axis of the probe, and reflect an ultrasonic wave from the vibrator, An ultrasonic reflecting mirror that bends the ultrasonic beam in a direction orthogonal to the central axis, and the ultrasonic beam is radially scanned by setting the rotation center on the ultrasonic reflecting mirror. Sound wave diagnostic equipment. 7. The apparatus according to claim 1, wherein the center offset correction type writing control means generates a θ address corresponding to the azimuth direction of the ultrasonic beam, and a beam address counter for generating each data of each ultrasonic beam. A means for generating an R address, a sample counter for generating the R address using the rotation center as an address initial value, and a center offset for setting a sampling start time point corresponding to the rotation center according to the center offset amount. An ultrasonic diagnostic apparatus comprising: a correction circuit. 8. The apparatus according to claim 7, wherein an A / D conversion circuit, which is provided in a preceding stage of the echo data memory and A / D converts the received signal, and a sampling clock is supplied to the A / D conversion circuit. A sampling clock generator that supplies the sampling clock, and the sample counter counts the sampling clock from a sampling start time set by the center offset correction circuit. 9. The ultrasonic diagnostic apparatus according to claim 8, further comprising a clock frequency switch that changes a frequency of the sampling clock. 10. The apparatus according to claim 1, wherein the coordinate conversion means is composed of a coordinate conversion table storing a coordinate conversion calculation result when the center offset amount is 0. Diagnostic device. 11. The apparatus according to claim 10, wherein the coordinate conversion unit has a plurality of coordinate conversion tables selected according to a display magnification, and the display magnification is changed by switching the coordinate conversion tables. An ultrasonic diagnostic apparatus characterized by the above. 12. The ultrasonic diagnostic apparatus according to claim 1, further comprising means for determining a center offset amount of a used probe.