JP2840848B2 - Ultrasound diagnostic equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic diagnostic apparatus having beam forming means capable of continuously changing the focal length of a receiving beam and the aperture width of a receiving probe.

(Prior Art) An ultrasonic diagnostic apparatus is an apparatus that irradiates an ultrasonic wave into a subject, receives an ultrasonic wave reflected from a tissue or a lesion, and displays the image to perform diagnosis. For this purpose, the transmitted and received ultrasonic waves are formed into a beam in order to give azimuth resolution to the ultrasonic waves transmitted and received within the subject, and an image of a cross section inside the subject is created by moving the beam. ing.

By the way, if the beam width is wide, it is not possible to distinguish two points in the beam width, and the resolution in the azimuth direction is reduced. Therefore, it is necessary to keep the beam width as narrow as possible to the depth to be imaged in order to obtain an image in which each reflection point can be clearly identified.

The beam width of the transmitted / received wave of the ultrasonic diagnostic apparatus is the product of the transmitted beam width and the received beam width, and the continuously variable received beam width is important. Received beam width Δ of ultrasonic diagnostic equipment
x is approximately represented by the following equation.

Δx = kD / A (1) where k: proportionality constant D: depth A: receiving probe aperture width Therefore, to obtain a uniform azimuth direction resolution at any depth, D in equation (1) What is necessary is to make / A constant.

However, in order to obtain a received beam width having a uniform azimuth resolution between the depth from the transmission point to the deepest reflection point, it is necessary to increase the depth D and increase the aperture width A. Is limited by the maximum aperture width determined by the physical structure of the receiving probe. This state will be described with reference to FIG. The figure is a curve diagram showing an example of the receiving probe,
The possible aperture range of the number of receiving aperture elements is 0 to 64 channels,
An example is shown in which the width of one channel is 0.5 mm. (I)
The figure shows the relationship between the number of aperture elements of the receiving probe that varies with the depth D and the depth D of the aperture width A. The minimum aperture width is 0 m.
The opening width A can be linearly increased in proportion to the depth D from the point m to the point having the maximum opening width of 32 mm.
After the depth of 100 mm, which is 32 mm, the wave receiving aperture width A cannot be made 32 mm or more, and it becomes a straight line with a constant aperture width of 32 mm.
(B) The figure shows a curve when the focal length of the receiving probe is increased in proportion to the depth D, and the receiving focal length linear with respect to the depth D can be increased. (C) The figure shows the beam width received by the receiving probe (hereinafter simply referred to as beam width).
In the figure at a depth of more than 100 mm, the beam width Δx increases in proportion to the depth D because A in equation (1) is constant. The F number is defined as a number representing the beam width as follows.

FIG. 4 shows the relationship among the depth D, the aperture element N, the aperture width A, and the F number. FIG. 5 is a graph showing the relationship between the F number and the depth D. The curve has a substantially constant value up to a depth of 100 mm.

(Problems to be Solved by the Invention) On the other hand, there is approximately the following relationship between the number N of aperture elements and the side lobe level. Here, the side lobe level is defined as shown in FIG. The figure is an explanatory view of the beam pattern of the array type transducer, 11 is a beam pattern indicating the signal intensity distribution of the transmission beam or the sensitivity distribution of the reception beam, 12 is the main lobe at the beam center, 13 is the left and right of the main lobe 12 It is a side lobe that appears on the screen. The peak value of the main lobe 12 is P and the peak value of the side lobe 13 is Q. The side lobe level L is represented by Q / P, and is obtained by the following equation.

N: Number of aperture elements c: Proportional constant Assuming that the number N of aperture elements of the probe has the distribution shown in the graph of FIG. 3A with respect to the depth D, the number N of aperture elements and the probe aperture width A Varies with depth D as shown in the table of FIG.

FIG. 7 shows the relationship between the depth D and the side lobe level L in accordance with the number N of aperture elements in FIG. As shown in FIG. 3 (c), when the number N of aperture elements is changed in order to keep the received beam width constant, the number of aperture elements becomes the third until the depth of the received beam width constant region reaches 100 mm.
As shown in FIG. 7A and FIG. 4, the side lobe level L in this region increases as the depth decreases, and reaches a maximum near the probe, as shown in FIG. Therefore, in the vicinity of the probe, an artifact due to a side lobe occurs, which causes image degradation.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and has as its object to reduce dynamic side lobes from near to far by reducing significant side lobes near the probe and reducing side lobe artifacts. An object of the present invention is to realize an ultrasonic diagnostic apparatus capable of displaying images in a wide range.

(Means for Solving the Problems) The present invention for solving the above problems is directed to an ultrasonic diagnostic apparatus having a beam forming means capable of continuously changing a focal length of a receiving beam and an opening width of a receiving probe. In the deep part, in order to obtain a uniform resolution, the receiving aperture width is linearly changed according to the depth up to the allowable maximum value of the receiving probe aperture width, and in the shallow part, A receiving aperture width setting means for setting and maintaining the receiving probe aperture width at a constant value.

(Operation) In the deep part, the opening width of the receiving probe is changed according to the depth up to the maximum opening width, and in the shallow part, the opening width of the receiving probe corresponds to the depth from a certain depth to a shallow part. The side lobe level is reduced in the shallow part while maintaining the high resolution in the deep part.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a pulse generation circuit for generating a pulse for transmitting an ultrasonic wave at a predetermined repetition period, and transmits a pulse signal to an n-channel transmission beamformer 2. The transmission beamformer 2 applies a phase delay to each channel pulse in order to form a transmission beam from the input n pulse signals. Numeral 3 sends a signal to the pulse generation circuit 1 to control the pulse generation timing and the pulse repetition period, and to control the transmission beamformer 2 to form a transmission beam and determine its focal length, transmission direction and the like. System controller. Reference numerals 4a, 4B,..., 4n denote transmission drivers for amplifying the signal output from the transmission beamformer to generate pulses of required power. Each output is input to the probe 5 and each of the transducer elements 6a to 6n To excite. This probe 5
Has 0 to 64 channels. Reference numeral 7 denotes an aperture variable circuit that changes the aperture width of the probe 5 under the control of the system controller 3 at the time of reception, and 8 denotes a reception beamformer that performs phasing and addition of reception signals from the aperture variable circuit 7 to synthesize a reception beam. Both are system controllers 3
Is controlled by

Next, the operation of the apparatus of the above embodiment will be described. The n-channel transmission pulse generated by the pulse generation circuit 1 is input to the transmission beamformer 2. Transmission beamformer 2
Performs phase delay processing on the transmission pulse of each channel under the control of the system controller 3 to form a transmission beam. In forming the transmission beam, the system controller 3 sets the transmission beam width and the focal length of the transmission beam. The signals subjected to the delay processing by the transmission beamformer 2 are power-amplified by the transmission drivers 4a, 4b,... 4n, input to the probe 5, and transmitted to the transducer elements 6a, 6b,
, 6n are excited and converted into ultrasonic waves, which are transmitted into the subject. The ultrasonic wave reflected from the target point is received by the probe 5 and converted into an electric signal. The electric signal is passed through the variable aperture circuit 7 and subjected to phasing and addition by the receiving beamformer 8 and output.

The system controller 3 controls the variable aperture circuit 7 to change the probe aperture width so as to keep the D / A of equation (1) constant. The number is fixed at a constant 26 channels and the depth
As the depth further exceeds 40 mm, the opening width of the probe is increased so as to keep the D / A of equation (1) constant. As the depth increases, the probe opening width increases. However, when the number of aperture elements reaches 100 mm, which reaches 64 channels, the number of aperture elements cannot be changed thereafter.

In this way, by keeping the number of aperture elements at a constant number of 26 channels without decreasing the number of aperture elements in proportion to the depth in the shallow portion of the depth D, the side lobe level L is increased as shown by the curve in FIG. The depth D is constant at a portion shallower than 40 mm, and is greatly improved at a portion shallower than the conventional side lobe L shown in FIG. In this case, the F-number representing the receiving beam width is a curve shown in FIG. 8, and the receiving beam width within a depth of 40 mm is smaller than the conventional case shown in FIG. Although the uniformity increases, this range is sufficiently small with respect to the entire image, so that a sense of incongruity due to uneven resolution is not felt.

As described above, according to the present embodiment, an image with reduced side lobe artifacts can be obtained without deteriorating the resolution.

The present invention is not limited to the above embodiment.
In the description of the embodiment, examples of the number of aperture elements, the aperture width, the corresponding depth, and the like are shown. However, this is merely an example, and an appropriate number can be selected.

(Effects of the Invention) As described in detail above, according to the present invention, by reducing a remarkable side lobe in the vicinity of the probe and reducing side lobe artifacts, the dynamic range from the near part to the far part is reduced. This makes it possible to display images in a wide range, and has a great practical effect.

[Brief description of the drawings]

1 is a block diagram of an apparatus according to an embodiment of the present invention, FIG. 2 is a side lobe level curve obtained by the apparatus according to the embodiment of the present invention, and FIG. 3 is a beam width curve by a conventional receiving probe. FIG. 4 is a diagram showing numerical values corresponding to depths such as the number of aperture elements, aperture width, and F number of an example of a receiving probe, FIG. 5 is a curve diagram with respect to depth of F number, and FIG. FIG. 7 is an explanatory diagram of a side lobe level, FIG. 7 is a curve diagram of a side lobe level of a conventional example, and FIG. 8 is a curve diagram of an F number obtained by this embodiment. DESCRIPTION OF SYMBOLS 1 ... Pulse generation circuit 2 ... Transmission beam former 3 ... System controller 4a-4n ... Transmission driver 5 ... Probe 6a-6n ... Transducer element 7 ... Aperture variable circuit 8 ... Reception Wave beamformer 11: Beam pattern, 12: Main lobe 13: Side lobe

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-60-199438 (JP, A) JP-A-54-38694 (JP, A) JP-A-60-108042 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) A61B 8/00-8/14

Claims (1)

(57) [Claims] An ultrasonic diagnostic apparatus for receiving an ultrasonic wave from a subject by changing a receiving aperture width of a probe according to a change in a focal length of a plurality of receiving beams. At a plurality of focal lengths existing in the probe-side region with respect to the predetermined focal length, the reception aperture width is maintained at a predetermined width in order to make the side lobe of the reception beam substantially constant. In addition, at a focal length existing in a region opposite to the probe with respect to the predetermined focal length, the receiving aperture is increased as the focal length increases in order to make the receiving beam width substantially constant. An ultrasonic diagnostic apparatus comprising means for increasing the width.