Ultrasonic imaging and circular antenna array for ultrasonic imaging

 

(57) Abstract:

The invention is used in medicine, primarily in the ultrasonic mammography, and tomografirovaniya limbs and organs of the abdominal cavity. Ultrasound scanner contains connected in series circular antenna lattice priekaistaudami piezoelectric tranducers, multi-line block of transceivers with antenna switch, multi-channel analog-to-digital Converter, the processing unit of received signals, the accumulation block image and the block tomographic display. When this scanner is further provided with a turntable with software control that has circular antenna array, the latter performed with sparse irregular location priekaistaudami piezoelectric tranducers, the number of which is less than the number of nodes of the steps of scanning and piemeslotie the piezoelectric tranducers have a radiating surface of the cylindrical arc-length directing more than half of the wavelength of the ultrasonic acoustic pulse and placed on the nodes of the ring antenna array, whose numbers and angular distances satisfy particularly the re two groups priekaistaudami piezoelectric tranducers, in one of which the piezoelectric tranducers have the same angle of inclination relative to the plane perpendicular to the axis of the circular antenna array, and the piezoelectric tranducers in the other group have different angles of inclination lying in a certain range, for example, from -20 to +20o. The invention provides high resolution imaging of soft tissue with a small amount of priekaistaudami converters. 2 S. and 1 C.p. f-crystals, 3 ill.

The invention relates to the field of medical diagnostics, in particular to acoustic tomography, and can be used for visualization of the internal structure of soft tissues of the body, such as mammography.

The prior art known to the device (see RF Patent 2002451, class A 61 B 8/14, 1993) to obtain two-dimensional acoustic images to layers - ultrasound scanner, containing connected in series priemysel, the power amplification and switching, analog-to-digital Converter, the processing unit including a memory and a summing device, and display device (visualization). The main disadvantage of this solution is the use of one common transducer for emitting and receiving, at seanna ultrasonic field. It is not possible to conduct a quantitative characterization of acoustic properties of the examined tissue. In addition, the use of a single Converter of this type requires a permanent move, which required the introduction of a scanner and a controller electrically connected with the processing unit, complicating the functional diagram of the imager without the benefit of their information capabilities.

Closest to the invention is an ultrasound imaging, containing connected in series circular antenna lattice priekaistaudami piezoelectric tranducers, which is placed in the tub with the immersion liquid, multichannel transceiver unit and an analog-to-digital Converter, the power gain, the conversion unit and display on the digital computer programmed to perform the Fourier transform (see U.S. Patent 5305752, class A 61 8/00 1994). However, the use of continuous (circular or linear, as claimed in the patent) lattice with the location of the individual piezoelectric tranducers at the distance of half a wavelength (or closer, as stated in the patent) leads to a very small transverse dimensions of each of the piezoelectric tranducers (0.5-1.0 mm, as e is the signal-to-noise ratio. The use of continuous radiation at one or more frequencies) with a duration of at least the time of the double mileage waves in the environment, leads to spurious reflections from the surface of the antenna array, creating an additional obstacle for the reception of the scattered signal. Given as examples in the patent, the device has an antenna grid, consisting of 512 piezo-transformers connected to the electronic unit via a multi-stage switch, which complicates the whole scheme and introduces additional interference.

The invention is directed to creating ultrasound scanner, providing high-resolution reconstruction and visualization of the internal structure of soft biological tissues with low levels of noise and interference that degrades the image, with a relatively small number priekaistaudami piezoelectric tranducers.

The solution of this problem is provided by the fact that the ultrasonic tomograph containing connected in series circular antenna lattice priekaistaudami piezoelectric tranducers, multi-line block of transceivers with antenna switch, multi-channel analog-to-digital preobrazovaniya, according to the invention is further provided with a turntable with software control that has circular antenna array, the latter performed with sparse irregular location priekaistaudami piezoelectric tranducers, the number of which is less than the number of nodes of the steps of scanning and piemeslotie the piezoelectric tranducers have a radiating surface of the cylindrical arc-length directing more than half of the wavelength of the ultrasonic acoustic pulse and placed in the nodes of the circular antenna array, whose numbers and angular distance when combined in different non-repeating pairs satisfy the following relations:

< / BR>
< / BR>
p= zp, (3)

zp= |i-k|, (4)

where P is the minimum number of non-repeating pairs (combinations), each of which is composed of two piezoelectric tranducers;

N is the number of equally spaced knots - step-scan circular antenna array;

l is the arc length of the radiating surface of the piezoelectric tranducers;

R is the radius of the circular antenna array;

- the angular distance between ravnovesie nodes circular antenna array;

p- the current angular distance IU kraushouse couple;

zpmodule differential current numbers of nodes, which are the piezoelectric tranducers, forming each distinct pair. Many values of zpis a continuous series of natural numbers in the interval from to ;

i, k is the current number of nodes, which are the piezoelectric tranducers, forming each distinct pair of values in a numeric interval from 1 to n

In addition, the solution of this problem is provided by the fact that circular antenna array for ultrasonic imaging includes at least two groups priekaistaudami piezoelectric tranducers, in one of which the piezoelectric tranducers have the same angle of inclination0relative to the perpendicular to the plane of tomografirovaniya plane perpendicular to the axis of the circular antenna array, and the piezoelectric tranducers in the other group have different angles of inclinationjlying in a certain range, for example from -20oto +20o.

The proposed design run annular sparse antenna array with the stated choice of layout priekaistaudami piezoelectric tranducers in combination with its rotation provides a high resolution), the equivalent resolution of a solid circular antenna array with ravnovesie the piezoelectric tranducers, (for example, sparse antenna array with 26 piezoelectric tranducers equivalent non-sparse antenna array with 256 evenly spaced piezoelectric tranducers), which allows to significantly simplify the circuit-hardware implementation of ultrasound imaging by reducing the number priekaistaudami circuits (amplifiers and generators), to increase the size priekaistaudami piezoelectric tranducers and reduce the level of noise and interference due to the use of piezoelectric elements with a developed sensitive surface and low impedance.

At the same time declared tilt priekaistaudami piezoelectric tranducers leads to an additional phase shift in the scattered signal depending on the position of the restoring scattering point of the body along an axis perpendicular to the layer tomografirovaniya that allows three-dimensional scanning announced inside layer.

Alternatively, it can accommodate priekslikumi piezoelectric tranducers the above two groups at different horizontal levels, which creates the possibility of the, 1 presents a block diagram of the ultrasonic scanner of Fig. 2 schematically shows a General view of the circular antenna array of Fig. 3 is a General view priekaistaudami piezoelectric tranducers and their location in the circular antenna array.

An ultrasound scanner is designed for two-dimensional and/or three-dimensional ultrasonic imaging and subsequent visualization of the internal structure of soft tissues and organs such as mammary glands, contains connected in series circular antenna grid 1 (CT), multi-block 2 of transceivers with antenna switch (AK-bppu), multichannel analog-to-digital Converter 3 (ADC) unit 4 processing (scattered) signal (BOPS), block 5 image accumulation (BNI) and block 6 tomographic display (BTO).

Circular antenna array 1 (CT) is placed in the bath 7, is filled with the immersion liquid and installed 8 on the rotary table (PS) swivel 9 unit (PU) with control system 10 (SU), includes N=256 equally-spaced knots - step-scan and performed with sparse irregular arrangement 26 priekaistaudami piezoelectric tranducers in the nodes of the ring lattice in such a way that, when one natural numbers zpon the interval from to you can find at least one pair of piezoelectric tranducers, the angular distance between the two elements which isp= zpand the module of the difference between the current numbers of the nodes in which they are located, is equal to zp= |i-k|, where i and k are the numbers of nodes of the ring antenna array with values in the range from 1 to N, in which respectively one and the other piemeslotie the piezoelectric tranducers the above pairs; the angular distance between ravnovesie nodes circular antenna array; l is the arc length of the radiating surface of the piezoelectric tranducers; R is the radius of the circular antenna array.

Forming a circular antenna grid 1 piemeslotie the piezo-transformers 11 are piezoelectric active element 12 of piezoelectric ceramics (for example, type TSTS-19) with a Central emission frequency of 1-2 MHz convex cylindrical surface of the radiation to which the front pasted a thin cylindrical lens 13 of plexiglass (Plexiglas), providing weak focusing in the vertical plane to extend the zone of low divergence, and the opposite (rear) side of the piezoelectric element 12 posted by damping layer 14 of a mixture of metal is zeway antenna array 1 ultrasonic scanner fixed so that at least one group of them has the same angle of inclination0the axis of the cylindrical surface relative to the perpendicular to the plane of tomografirovaniya (the plane perpendicular to the axis of the circular antenna array), which can be zero or the value in a few (3 to 10o) degrees, and in another group piemeslotie the piezoelectric tranducers 11 can have different angles of inclinationj0which lie in a certain range, for example from -20oto +20o.

Ultrasonic imaging is as follows.

In the process of tomografirovaniya rotary table 8 with a circular antenna array 1 is sequentially N discrete positions in increments corresponding to the angular distance between ravnovesie nodes, doing a full turn. While table next position piemeslotie the piezoelectric tranducers 11 from the transmitter of transceiver devices unit 2 (AK-bppu) sequentially fed through the antenna switch signals - radiation pulses with a duration of 3-10 of the oscillation period of the operating frequency (1-2 MHz). After emission of the impulse in one of the piezoelectric tranducers 11 is receiving R the firs 11, the signals are transmitted through the mentioned antenna switches on the amplifier unit 2 (AK-bppu). At the end of the reception of the scattered signal to the antenna switch of the next piezoelectric transducer 11 connects to the transmitter unit 2 (AK-bppu) and the radiation of the next pulse. Upon completion of the process of radiation all priekaistaudami the piezoelectric tranducers 11 circular antenna array 1, the turning device 9 sets the circular antenna grid 1 in the following discrete position (node - step scan).

The signals from the amplifier unit 2 (AK-bppu) are fed to the multi-channel analog-to-digital Converter 3 (ADC), output signals from which are received in block 4 of the processing of received signals (BOPS) and remembered it. In block 4 (BOPS) is the exact measurement of the propagation time of the pulse through the object under examination all the routes connecting the emitters and receivers (emitting and receiving piezoelectric tranducers 11) and through tomografirovaniya. On the basis of these time values in unit 4 (BOPS) is the estimate of the distribution of large-scale (more than 5-10 wavelengths) inhomogeneities in the ultrasonic velocity and absorption in the object inatech signals in order to restore the full picture of the velocity distribution, absorption and tissue density in the cross section tomografichyeskogo body. This two-step processing can correct distortion waves introduced by the heterogeneity of the studied object, which in ultrasonic medical devices, not taking into account such distortion, reduce the resolution several times. Thereby improving the resolution of the proposed MRI scanner in the plane of tomografirovaniya and close to the maximum achievable for a given operating frequency and close to a quarter wavelength.

When using the scanner ring antenna array 1 with priekaistaudami the piezoelectric tranducers 11 mounted at various angles of inclination, in the process of phasing undertaken in unit 4 (BOPS) takes into account the slope mentioned priekaistaudami converters 11, which improves the resolution of the imager in the direction perpendicular to the plane of tomografirovaniya, 5-8 times. Thus, in this case, full voiced layer tomografirovaniya is divided into an appropriate number (5-10) of thin layers, recovered in unit 4 (BOPS) at the same time.

As the information processing unit 5 of the image accumulation (bn is lomograficheskogo display (BTO) is a visual representation of the results of tomografirovaniya or in layered form, either in the form of a synthesized three-dimensional display, obtained by known programs such synthesis.

As an example implementation of the invention designed ultrasonic tomography with circular antenna array 1 formed by the N = 256 ravnovesie nodes with an angular step and having radius R=130 mm, for which the calculation is defined by the optimized number - 26 - priekaistaudami piezoelectric tranducers 11 with the transverse dimensions of the arc length of the radiating surface of the piezoelectric tranducers 11 (piezoelectric element 12 together with structural shell) l 20 mm (), unevenly positioned around the circumference of the ring nodes of the antenna array 1 with the following part numbers:

i, k= (1, 9, 16, 32, 39, 49, 60, 67, 78, 86, 97, 106, 113, 127, 134, 149, 158, 172, 186, 196, 207, 214, 221, 230, 240, 247),

that provides an implementation of a full tomographic scheme that uses all of the angles of radiation and scattering.

Rotary table with 8 swivel device 9 is a precision mechanism stepper motor rotation and the micro accurate setting of the angular position with a special control system 10. Antenna switches transceiver unit 2 implemented on key circuits, generators who ntenna grating 1 is placed in the bath 7 with the immersion liquid (a special blend of acoustic parameters, close to the parameters of the tissues examined organ). Analog-to-digital converters 3 are assembled on a chip Analog-Device. Unit 4 processing of received signals (BOPS) collected at several signal processors engaged in the processing of the first stage. Further processing is carried out in a personal computer with a Pentium 2, enhanced co-processor Sharc. As block 5 image accumulation (BNI) and block 6 tomographic display (BTO) is used by the processor of the personal computer and its display.

1. Ultrasonic tomograph containing connected in series circular antenna lattice priekaistaudami piezoelectric tranducers, multi-line block of transceivers with antenna switch, multi-channel analog-to-digital Converter, the processing unit of received signals, the accumulation block image and the block tomographic display, characterized in that it further provided with a turntable with software control that has circular antenna array, the latter performed with sparse irregular location priekaistaudami piezoelectric tranducers, the number of which is less than the number of nodes srmi with arc-length directing more than half of the wavelength of the ultrasonic acoustic pulse and placed on the nodes of the ring antenna array, the number and angular distance when combined in different non-repeating pairs satisfy the relations

< / BR>
< / BR>
p= zp,

zp= |i-k|,

where P is the minimum number of distinct pairs, each of which is composed of two piezoelectric tranducers;

N is the number of equally spaced knots - step-scan circular antenna array;

l is the arc length of the radiating surface of the piezoelectric tranducers;

R is the radius of the circular antenna array;

- the angular distance between ravnovesie nodes circular antenna array;

p- the current angular distance between the nodes of the ring antenna array, in which are located the piezoelectric tranducers, forming each distinct pair of;

zpmodule differential current numbers of nodes, which are the piezoelectric tranducers, forming each distinct pair, the set of values of zpis a continuous series of natural numbers in the interval from to ;

i, k is the current number of nodes, which are the piezoelectric tranducers, forming each distinct pair of values in a numeric interval from 1 to n

2. Circular antenna array for ultrasonometry least two groups priekaistaudami piezoelectric tranducers, in one of which the piezoelectric tranducers have the same angle of inclinationorelative to the perpendicular to the plane of tomografirovaniya plane perpendicular to the axis of the ring lattice, and the piezoelectric tranducers in the other group have different angles of inclinationjlying in the range of, for example, from -20 to +20o.

3. Circular antenna array for ultrasonic imaging in p. 2, characterized in that piemeslotie the piezoelectric tranducers these two groups are located on different horizontal levels.

 

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