JPH0127740B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field]

This invention provides an ultrasonic diagnostic apparatus that transmits ultrasound waves into the body of a subject (patient) and receives reflected signals inside the body to obtain a two-dimensional distribution image of acoustic reflection characteristics on a predetermined tomographic plane as a tomographic image. In particular, the present invention relates to improvements in transducer arrays that transmit and receive ultrasonic waves.

[Conventional technology]

Conventionally, a transducer array of an ultrasonic diagnostic apparatus has a large number of ultrasonic transducer elements arranged in a straight line, and signal transmission and reception to each element is controlled using a phased array method. As a result, a linear scan in which the transmitted and received ultrasonic beams are moved parallel to each other in the array direction, that is, within the tomographic plane, and a sector scan in which they are swung in a fan shape are performed, and the acoustic reflection characteristics of the tomographic plane of the human body are investigated. A two-dimensional distribution image is obtained as a tomographic image. In this case, it is of course desirable that the transmitted and received ultrasound beams be focused in the array direction (inside the tomographic plane) and in the direction perpendicular to the array direction (in the tomographic thickness direction). In order to obtain this focusing effect, electrons are focused in the direction within the tomographic plane, and focused in the direction of the thickness of the tomographic plane by an acoustic lens attached to the radiation surface of the transducer array.

[Problem to be solved by the invention]

However, acoustic lenses have various problems such as being difficult to manufacture and process, not easily achieving close contact with the transducer array, and not having very good focusing effects. In view of the above, an object of the present invention is to provide a transducer array for an ultrasonic diagnostic apparatus that can effectively perform focusing in the thickness direction of a tomographic plane without using an acoustic lens.

[Means for Solving the Problems] In order to achieve the above object, a transducer array of an ultrasonic diagnostic apparatus according to the present invention includes a large number of ultrasonic transducer elements arranged in a straight line, and each element A main array in which signal transmission and reception to and from Each of the plurality of elements is controlled so that signals of opposite phases are alternately transmitted and received to the elements of the main array, and the dimension of each element in the sub-array direction is long in the center and shorten toward both ends. A predetermined number of subarrays are provided.

[Effect]

In each of the many sub-arrays arranged perpendicular to the main array, each element is controlled so that it alternately transmits and receives signals of opposite phase to the elements of the main array. Therefore, this subarray will function as a Fresnel strip. Further, the dimension (length in the array direction) of each element in each subarray is determined such that it is long at the center and becomes short toward both ends. Therefore, the ultrasonic beam can be focused at a predetermined distance determined by the above dimensions in the subarray direction (cross-sectional thickness direction) by the subarray functioning as a Fresnel strip.

【Example】

Next, an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, a transducer array 1 of an ultrasonic diagnostic apparatus according to an embodiment of the present invention consists of a two-dimensional array of ultrasonic transducer elements. That is, the elements 11a, 12a, 13a, . . . are arranged in a straight line to form a main array. Elements 11a, 12a, 13 forming this main array
a,..., a plurality of elements 11b to 11g, 1 in the direction perpendicular to the main array.
2b to 12g, . . . are arranged to form subarrays for each of the main array elements 11a, 12a, 13a, . A backing layer 2 is provided on the back side of these many elements, and a 1/4 wavelength matching layer 3 is provided on the front side (ultrasonic wave transmitting/receiving side). In this transducer array 1, main array elements 11a, 12a, 13a,
The transmission and reception of signals to each of the transducer arrays is controlled by the phased array method, similar to the conventional transducer array. In other words, focusing the ultrasound beam in the main array direction (intra-sectional direction),
In order to determine the direction of the beam, the phase of the drive signal given to each of the elements 11a, 12a, 13a, . . . of the main array and the received signal from these are slightly different for each element. On the other hand, each element of the sub-array is alternately given a drive signal having an opposite phase to the drive signal given to the main array element. For example, in the sub-array provided in the element 11a of the main array, a signal with a zero phase shift and a signal with a phase shift π of the drive signal applied to the element 11a of the main array are applied to the element 11a of the main array. The (adjacent) elements 11b and 11c have a signal with a phase shift of π, the second elements 11d and 11e have a signal with a phase shift of zero, and the third element 11f and 1
1g is alternately given a signal with a phase shift of π, and so on. The phase relationship of the received signals is similarly controlled. This subarray will therefore function as a Fresnel strip. Regarding the dimensions of each element, the main array elements 11a, 12a,
The lengths in the arrangement direction (arrangement direction as the main array) of each of 13a, . . . are approximately equal.
As for the subarray, the length in the arrangement direction (the arrangement direction as a subarray) is longer at the center as shown in the figure, and is sequentially shorter at both ends.
This is because the ultrasonic beam is focused at a predetermined distance by the subarray functioning as a Fresnel strip as described above. That is, the center or central element of the subarray (eg 11a)
For each element (for example, 11
a, 11b, 11c, 11d, 11e, 11f,
11g) boundary position (distance from center to boundary)
is ρm (m=0, 1, 2,...), that is, the boundary position between elements 11a and 11b and 11a and 11c is ρ0, the boundary position between elements 11b and 11d and 11c and 11e is ρ1, and element 11d. When the boundary position between 11f and 11e and 11g is set to ρ2, each element is adjusted so that ρm satisfies the following relationship: ρm = √ (2) (1 + 2) λ; Ultrasonic wavelength f; Focal length. (For example, 11a, 11b, 11c, 11d, 11e, 11
By determining the length of f, 11g) in the subarray direction, the ultrasonic beam can be focused at a focal length f in the subarray direction. For example, the propagation speed of sound waves in the body is 1500m, and the frequency of ultrasound is 3M.
In terms of Hz, the dimensions for focusing to a focal length of 20 cm are given by the above formula for element 11a.
14.14mm, 11b, 11c 5.18mm, 11
It can be calculated as 3.56 mm for d and 11e, and 2.90 mm for 11f and 11g. In this way, the subarrays are set in a phase relationship that constitutes a Fresnel strip, and the dimensions of each element of the subarray that functions as a Fresnel strip are set to a length such that they are focused at a predetermined distance. , subarray direction (fault plane thickness direction)
The shape of the ultrasonic beam becomes as shown by the dotted line 41 in FIG. 2, and a focusing effect with a long focal depth (the length of the focusing region in the distance direction from the transducer array 1) can be obtained. By the way, according to the acoustic lens, the second
As shown by the two-dot chain line 42 in the figure, as the distance increases after focusing, the light rapidly diffuses, and the Fresnel strip configuration has better focusing characteristics. In the above embodiment, the subarray has a Fresnel strip configuration, but even if the dimensions of the subarray elements in the subarray direction are the same and the phase of signal transmission and reception to these elements is controlled by a phased array method, the difference in the tomographic thickness direction A focusing effect can be obtained. However, in this case, the configuration of the electronic circuit becomes complicated because phase control must be performed for each element of the subarray.

【Effect of the invention】

According to the transducer array of the ultrasound diagnostic apparatus of the present invention, a large number of subarrays having a Fresnel strip configuration are provided in a direction perpendicular to the main array, so that the ultrasound beam is focused in the direction of the thickness of the tomographic plane with good characteristics. It is possible to remove artifacts (virtual images) from ultrasonic tomographic images and improve the image quality. Furthermore, since no acoustic lens is used, problems in manufacturing, processing, etc. can be solved and manufacturing can be done easily and at low cost. Furthermore, it is possible to obtain excellent focusing characteristics such as a deeper depth of focus than that of an acoustic lens.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view of an embodiment of the present invention;
FIG. 2 is a diagram for explaining the focusing of the ultrasonic beam in the subarray direction. 1...Transducer array, 11a, 12
a, 13a...Main array element, 11
a to 11g, 12a to 12g... Element of subarray, 2... Backing layer, 3... 1/4 wavelength matching layer, 41, 42... Ultrasonic beam.

Claims (1)

[Claims] 1 A main array consisting of a large number of ultrasonic transducer elements arranged in a straight line, in which signal transmission and reception to each element is controlled by a phased array method, and a main array for each element of this main array. A plurality of ultrasonic transducer elements are arranged in a perpendicular direction, and each of the plurality of elements is controlled so that signals of opposite phases are alternately transmitted and received to the elements of the main array, and A transducer array for an ultrasonic diagnostic apparatus comprising a large number of subarrays, each element having a dimension in the subarray direction that is long at the center and becomes short toward both ends.