JPH0542138A - Ultrasonic diagnostic device and its calibrating method - Google Patents

Abstract

PURPOSE:To realize a higher picture quality by correcting an error component caused by factors such as the aperture of a vibrator array probe, a focal distance, a frequency, depth, an ultrasonic attenuation characteristic in a living body, etc. CONSTITUTION:By using an array probe 1 used actually, and a phantom fobtained by mixing finely scattered bodies uniformly into a substance having an attenuation characteristic being equivalent to a living body tissue, the distribution of a propagation time of an echo signal reflected from a finely scattered body group is measured, and calibration data is generated in advance, and stored in advance in a memory 21. By using the correction data of the memory 21, measured data is corrected by a delay quantity correcting device 24.

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 for correcting the phase distortion of an ultrasonic pulse due to non-uniformity of sound velocity in a subject.

[0002]

2. Description of the Related Art In a conventional ultrasonic diagnostic apparatus, an ultrasonic echo detected by focusing a transmitted ultrasonic pulse on a certain region in a subject using a probe in which a large number of transducers are arranged in an array. Ultrasonic images are reconstructed based on signals and displayed on a display.

Here, various tissues exist in the body, and the sonic speeds of these tissues with respect to ultrasonic waves are not uniform. For this reason, the ultrasonic pulse has a phase distortion based on the non-uniformity of the sound velocity in the body, which deteriorates the image quality. Therefore, it is necessary to correct this phase distortion.

For this reason, conventionally, the ultrasonic pulse transmitted from the probe is concentrated in a certain area in the subject, and the ultrasonic echo signal, which is a reflected wave from the minute scatterer group in the vicinity, is transmitted to each transducer in the receiving port. Then, the cross-correlation function is calculated by the signal between at least two transducers of the receiving transducer group, and the phase distortion in the propagation time of the ultrasonic pulse due to the non-uniformity of the sound velocity in the subject is detected. A method for correcting this has been performed (Japanese Patent Laid-Open No. 63-51846).

[0005]

In the above-mentioned conventional apparatus,
By the cross-correlation function calculation using the reflection signals from a large number of minute scatterers, the data of the distortion of the propagation time of the ultrasonic pulse due to the non-uniformity of the sound velocity in the subject is obtained. However, the data thus obtained has an error depending on the shape of the ultrasonic transmission beam used for the data collection.

The shape of the transmission beam depends on many factors such as the aperture, focal length, frequency, depth (distance from the aperture) of the transducer array probe used to form it, and ultrasonic attenuation characteristics in the living body. It is difficult to keep these factors constant, changing. Therefore, in order to obtain the above-described propagation time distortion data with higher accuracy, it is necessary to correct the error component that changes due to the many factors described above, but this point was not taken into consideration in the prior art.

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide actual measurement conditions such as the aperture of the transducer array probe, the focal length, the frequency, the depth, and the ultrasonic attenuation characteristic in the living body. It is intended to correct the error caused by the above and always obtain the distortion data of the propagation time with high accuracy so that a high-quality ultrasonic image can be obtained as a result.

[0008]

Therefore, in the present invention, the transmitted ultrasonic pulse is focused on a certain region in the subject, and the ultrasonic echo signal reflected from the minute scatterer group in the vicinity thereof is received in the receiving aperture. In the ultrasonic diagnostic equipment that observes each transducer and corrects it by detecting the arrival time of the ultrasonic echo signal to each transducer, calibration data corresponding to each transducer is set. A processing means for subtracting the corresponding calibration data from the arrival time actually detected for each transducer is added.

As a method of creating the above-mentioned calibration data, a transducer array mounted in an ultrasonic diagnostic apparatus is applied to a phantom in which a minute scatterer is almost uniformly mixed in a substance having an attenuation characteristic equivalent to that of living tissue. While focusing the transmission ultrasonic pulse to a certain area in the phantom using a probe, the distribution of the propagation time of the ultrasonic echo signal reflected from the microscatterer group in the vicinity is measured, and based on the measurement data. Then, the calibration data is created.

[0010]

In FIG. 1, reference numeral 30 indicates a transducer array probe. As shown, the entire array is used as a receiving array, and the array from the center is used as a transmitting array. Further, 31 is a phantom made of agar or the like having an attenuation equivalent to that of a living tissue, and is a uniform phantom in which fine powder (fine scatterer group 32) such as graphite is evenly mixed and has no structure inside. , The phantom in which the reflector is not the minute scatterer group 32 but the point reflector 33 will be described.

The array probe 30 is used to focus the transmitted ultrasonic pulse on a certain region in the phantom containing only the microscatterer group 32, and the propagation of the ultrasonic pulse reflected from the microscatterer group 32 in the vicinity thereof. When the time distribution is measured, the distribution shown by the solid line in FIG. 1 is obtained. Similarly, when the measurement is performed by using the phantom including only the point reflector 33 limited to a certain position, the distribution of the propagation time of the ultrasonic pulse is as shown by the dotted line in FIG.

As shown in FIG. 1, the reflector is a group of minute scatterers 32.
And the case of the point reflector 33 have different distributions of the detected propagation time on the aperture. Furthermore, the group of minute scatterers 3
In the measurement by 2, the point reflector 33 is placed at the center position.
The difference in the distribution of the propagation time from that of the point reflector is different depending on the shape of the transmission beam, and the sharper the transmission beam is, the closer it is to the point reflector 33. Further, such data is obtained without any non-uniform layer (medium having a different sound velocity from the uniform phantom 31) between the array probe 30 and the uniform phantom 31. The same result should be obtained when using the point reflector 33 when used, but when the microscatterer group 32 is used, the transmission beam is not sufficiently sharp, It is considered that an error occurred in the measurement of the propagation time.

The present invention has been made based on such findings. That is, the array probe 30 mounted on the device
And the uniform phantom 31 are used to measure the propagation time distribution of the ultrasonic echo signals from the microscatterer group 32, the calibration data is created in advance based on the measured data, and the calibration data is stored in the memory of the device. Keep it. Then, when actually performing diagnostic measurement on a living body, the corresponding calibration data is subtracted from the arrival time actually detected for each transducer of the array probe. This corrects error components due to conditions such as the aperture of the array, focal length, and frequency on the device side and conditions such as in-vivo ultrasonic attenuation characteristics.

[0014]

FIG. 2 is a block diagram showing an embodiment of the ultrasonic diagnostic apparatus of the present invention, in which 1 is a probe and a large number of transducers 1a,
, b, 1c, ... Are arranged in an array, and transmit ultrasonic pulses in contact with the body surface of the subject 2 and receive ultrasonic echo signals reflected and returned. The abdominal wall 3, the liver 4, the blood vessel 5, and the gallbladder 6 are present in the body of the subject 2.
The blood vessel 5 and the gallbladder 6 form a structure that does not reflect the ultrasonic echo signal. Reference numeral 7 denotes an ultrasonic beam transmitted from the probe 1 so that the ultrasonic pulse is focused in a predetermined area. Reference numeral 9 is a pulser that drives the probe 1 by applying a high-voltage pulse, 10 is a transmission delay circuit that gives desired delay characteristics to the ultrasonic pulse transmitted from the probe 1, and 11 is a rate pulse generation that generates a rate pulse (reference signal). It is a vessel.

Reference numeral 12 is a preamplifier for amplifying the ultrasonic echo signal received by the probe 1, and 13 is a reception delay circuit for giving a desired delay characteristic to the ultrasonic echo signal. Reference numeral 14 is a phase distortion detection circuit for detecting phase distortion from the ultrasonic echo signal, 22 is an AD converter for converting the output of the phase distortion detection circuit 14 into a digital signal, and 23 is a temporary storage of the digitized echo signal from each transducer. Waveform memory, 21 is a memory for storing calibration data for each transducer described in detail in the section of action, and 23 is a memory for storing the echo signal propagation time of each transducer sequentially read from the waveform memory 24. The delay compensator that subtracts the calibration data of the applicable oscillator
Reference numeral 15 is an adder circuit and envelope detection circuit for phasing and adding echo signals corrected by the delay amount corrector 24 for each transducer and detecting an echo component, and 16 is a CPU that controls the entire system. (Central processing unit), 17 is a DSC (digital scan converter) for converting an ultrasonic echo signal into a TV scanning system, and 20 is a display for displaying an ultrasonic image.

The operation of the apparatus configured as above will be described below.

First, under the control of the CPU 16, a desired delay characteristic is given by the transmission delay circuit 10 to focus the transmitted ultrasonic pulse from the probe 1 on a certain region in the subject, and the ultrasonic wave from the tissue existing near this region is superposed. The probe 1 receives a sound wave echo signal. This received signal is amplified by the preamplifier 12, given a desired delay characteristic by the reception delay circuit 13, and then added to the phase distortion detection circuit 14, where the phase distortion in each transducer constituting the probe 1 is To be detected. This result is based on the control of the CPU 16 and the transmission delay circuit 1
0 or is sent to the reception delay circuit 13, and the phase distortion is corrected by the transmission delay circuit 10 being given a desired delay characteristic, and the ultrasonic pulse is again transmitted from the probe 1. Alternatively, it is corrected by giving a desired delay characteristic only in the reception delay circuit 13.

The echo signal processed as described above is digitized and written in the waveform memory 23, then sequentially read out and added to the delay amount corrector 24. The calibration data memory 21 is read and scanned in synchronization with the readout scanning of the waveform memory 23, and the corrector 24 subtracts the preset calibration data from the propagation time of the echo signal of each transducer. The corrected addition circuit and envelope detection circuit 15 perform phasing addition and envelope detection, which are then sent to the DSC 17, and finally an image with corrected phase distortion is displayed on the display 20.

[0019]

As described above, according to the present invention, the array probe and the uniform phantom that are actually used are used, and the conditions such as the aperture of the array, the focal length, the frequency, the depth, the ultrasonic attenuation characteristic in the living body, etc. The propagation time distribution data is measured in advance, and based on the data, propagation time calibration data for each transducer is created and set in the apparatus. Then, the calibration data is subtracted from the propagation time of each transducer detected during the diagnostic measurement on the living body, and an image is generated from the corrected data. Therefore, it is possible to obtain a high-quality ultrasonic image in which the adverse effects of the many error factors described above are eliminated.

[Brief description of drawings]

FIG. 1 is an explanatory view of the operation of the present invention.

FIG. 2 is a block diagram of an ultrasonic diagnostic apparatus according to an embodiment of the present invention.

[Explanation of Codes] 21 Calibration Data Memory 24 Delay Amount Corrector

Claims (2)

[Claims] 1. An ultrasonic echo signal reflected from a group of minute scatterers in the vicinity of a certain region of a subject, which is transmitted ultrasonic pulses, is observed for each transducer in a receiving aperture,
In the ultrasonic diagnostic apparatus that corrects this by detecting the arrival time of the ultrasonic echo signal to each transducer, calibration data corresponding to each transducer is set, and each transducer is actually An ultrasonic diagnostic apparatus comprising processing means for subtracting the corresponding calibration data from the detected arrival time. 2. A phantom in which a minute scatterer is substantially uniformly mixed in a substance having an attenuation characteristic equivalent to that of a biological tissue, and the phantom using the transducer array probe mounted in the ultrasonic diagnostic apparatus according to claim 1. 2. The calibration of claim 1 based on the measured data by focusing the transmission ultrasonic pulse on a certain area inside and measuring the distribution of the propagation time of the ultrasonic echo signal reflected from the microscatterer group in the vicinity thereof. A method for calibrating an ultrasonic diagnostic apparatus, which comprises creating data.