JP2009247511A - Ultrasonic imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible ultrasonic array probe capable of achieving a highly accurate beam formation with a small number of signal lines and having flexibility in bending or shape deformation. <P>SOLUTION: This ultrasonic imaging apparatus has: a probe including a plurality of elements for transmitting/receiving ultrasonic signals with a subject, and a connection section for relatively movably connecting the plurality of elements; a computing section computing relative positional information of the plurality of elements based on the receiving signals of the plurality of elements; and an image data generation section generating image data from the receiving signal and the relative positional information. This ultrasonic imaging apparatus optimizes a delay time between the receiving signals for minimizing the width of a receiving point response function so as to estimate the shape of a probe itself, transmit/receive based on the estimated shape and take a tomographic image. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrasonic imaging technique for imaging an image using an echo signal resulting from a spatial change in acoustic impedance inside a subject.

  An ultrasonic diagnostic apparatus that captures an ultrasonic image transmits ultrasonic waves from an ultrasonic probe to a subject, receives reflected echoes generated from the subject with the ultrasonic probe, and performs ultrasonic probe. An ultrasonic image is reconstructed and displayed based on the received signal output from the child. An ultrasonic image is an image of the position and intensity of a received echo signal. Assuming that the sound speed of the object is uniform, the distance in the propagation direction of the echo of interest can be determined by the time from transmission to reception.

  On the other hand, when obtaining a two-dimensional or three-dimensional ultrasonic image, it is necessary to control the position in the azimuth direction (direction orthogonal to the propagation direction) to acquire an echo signal. This azimuth scanning method includes a mechanical scanning method in which the transducer in the probe is moved in the azimuth direction, and a plurality of transducers are formed in the probe, and a delay time is given to the signal from each transducer. There is an electronic scanning method for controlling the signal income position.

  Here, as a probe, there exists a thing of the form used in a body cavity, for example, as described in patent document 1. FIG.

Japanese Patent Laid-Open No. 2004-167092

  In the case of the mechanical scanning method, 1. 1. Upper limit of imaging speed is lower than electronic scanning. 2. There is a problem in position reproducibility when capturing multiple tomographic images. 3. When the movement of the object is estimated by the Doppler method, the influence of the movement of the vibrator is generated. There is a possibility that the object is deformed by moving the vibrator. Hereinafter, the electronic scanning method will be described.

  In electronic scanning, as shown in FIG. 1, the difference in distance from each transducer to the target site is replaced with a time difference, and transmission and / or reception is performed to focus and transmit to an arbitrary place in space. In addition, it is possible to increase the reception sensitivity of an echo signal at an arbitrary place. At this time, since the accuracy of the focus depends on the estimation accuracy of the “distance from the transducer to the target site”, the conventional probe uses a highly rigid probe, and the shape of the probe depends on the measurement conditions. We have suppressed deformation as much as possible. For this reason, a probe having a high rigidity is generally used. However, considering the variety of applications, it may be advantageous for the probe to have low rigidity. For example, in the case of a probe used in a body cavity, the cross-sectional area is as small as possible when it is introduced into the body cavity, and the probe can be folded in the body cavity when it is desired to expand the aperture greatly in order to sharpen the focus of the transmission / reception beam It is desirable. Further, when monitoring is performed with the object kept in close contact with the subject for a long time, particularly when monitoring a movable part such as a joint, it is desirable that the shape of the probe can be changed in accordance with the change of the shape of the subject.

  However, when the probe is foldable with a joint such as a joint, information on the relative positions of the joints connecting a plurality of elements of the probe is required. For example, a rotation angle detection sensor can be used. When it is desired to increase the adhesion to the subject or to increase the reduction ratio of the cross-sectional area in folding, the number of angle detection sensors increases, and the number of signal lines increases accordingly. In order to improve the adhesion, the larger the number of joints, the better. Since the vibrator cannot be divided, the case where the number of joints is the maximum is the case where the number of joints is equal to the number of vibrators. However, when the adhesion is the best, the number of signal lines is doubled compared to when there is no joint. In an electronic scanning type ultrasonic imaging apparatus, the number of signal lines is usually large, usually about 200, and further doubling the number greatly impairs practicality. In view of the above, an object of the present invention is to realize an apparatus configuration that can easily change the shape and can reduce the number of signal lines for estimating the shape of a probe.

  As an example, the present invention is based on a probe including a plurality of elements that transmit and receive an ultrasonic signal to and from a subject, and a connecting portion that relatively movably connects the plurality of elements, and reception signals of the plurality of elements. And a calculation unit that calculates relative position information of the plurality of elements, and an image data generation unit that generates image data from the received signal and the relative position information.

  By optimizing the delay time between received signals so that the width of the reception point response function is minimized, the shape of the probe itself is estimated, and transmission / reception is performed based on the estimated shape, and tomographic imaging is performed. May be configured to perform.

  It is possible to realize an apparatus configuration in which the shape can be easily changed and the number of signal lines for estimating the shape of the probe is reduced.

  Hereinafter, examples of embodiments of the present invention will be described.

  First, the overall configuration of the apparatus will be described with reference to FIG. A probe beam former 3 and a receive beam former 6 are connected to a probe 1 whose shape can be flexibly deformed via a send / receive switch 2. The transmission beamformer 3 uses a waveform stored in the transmission waveform memory 5 and gives a delay time and a weight to a transmission signal for each element so that the ultrasonic beam is focused at a desired position. It is controlled by the system 4. The electrical signal from the transmission beamformer 3 is converted into an ultrasonic signal by the probe 1, and an ultrasonic beam is irradiated to a subject not shown here. The echo signal reflected in the subject and returned to the probe is converted into an electric signal by the probe 1 and sent to the receiving beam former 6. The signal received by the receiving beam former 6 is first used by the element position estimating unit 7 to estimate the element position. This element position estimation result is used to calculate the delay time and weight of the receiving beam former, and is used to selectively enhance the echo signal from the desired position of the subject. The output of the beamformer 6 is converted into an image signal by the scan converter 9 through envelope detection, log compression, band pass filter, gain control, and the like by the detection unit 8 and displayed as a tomographic image on the display unit 10. The above description relates to the imaging of the first frame. When the movement of the subject between the frames is small, the estimation result of the element position estimation unit 7 is reflected and the control system starts from the second frame. The delay time calculated by the transmission beamformer can also be recalculated in a form corresponding to the element position. The element position estimation unit 7 is composed of a received data memory, an evaluation function storage unit, an evaluation calculation unit, and a shape estimation unit, and outputs an evaluation function from the received data based on an evaluation function described later. The most probable element shape is obtained, and this estimated element shape is used as an output.

  The reason that the element position estimation result needs to be reflected only in the receiving beamformer in the first frame is as follows. In ultrasound imaging, from the viewpoint of spatial resolution and sensitivity, it is conceivable that both transmission and reception are focused at each point in the field of view. For example, when the number of scanning lines is N and the imaging range in the depth direction / the beam width in the depth direction = M, NxM transmission / reception is repeated to perform imaging for one frame. The time required to acquire one frame is proportional to NxM. In order to shorten the imaging time, methods called dynamic focus and aperture synthesis are often employed. This improves the frame rate by reducing the number of transmissions while maintaining the spatial resolution with high-accuracy reception focus by setting multiple reception focus points for one transmission. Is the method. Since reception can be performed by focusing on an arbitrary place in space by shifting and adding the delay time of the signal received at each channel, it does not depend on the propagation time of the ultrasonic wave in the living body. In addition, a plurality of focus points can be switched. More specifically, a single received signal is used to focus on a plurality of separate points (aperture synthesis), or continuous in time according to the depth of the reflected source of the received signal. The position can be shifted (received dynamic focus). When such a method is used, imaging is performed with the received beam spatially narrowed compared to the transmitted beam. As a result, it is necessary for the received wave to focus the beam compared to the transmitted wave, so it is important to grasp the more accurate element position in the received wave.

  Here, (1) evaluation function (I. Point response function in azimuth direction, II. Point response function in depth direction, III. Two-dimensional point response function, IV. Function to calculate cross-correlation between adjacent signals) , (2) Evaluation method (I. Sequential expansion from the end of the array, II. Divide the whole aperture into two parts, sequentially increase the number of divisions, III. (I. Rotation only (without expansion / contraction), II. Rotation and expansion / contraction), (4) Transducers (I. PZT, II. PVDF, III. CMUT) are examined. Hereinafter, embodiments will be described separately with respect to some typical examples. Hereinafter, the condition having flexibility refers to a condition in which a plurality of elements are coupled so that their relative positions are movable.

  In this embodiment, the case where the array shown in FIG. 2 that does not expand and contract with flexibility will be described. The evaluation functions are I. Point response function in the azimuth direction, II. Point response function in the depth direction, and III. Two-dimensional point response function. For flexibility (constraint conditions), I. Consider only rotation (no expansion / contraction). In FIG. 2A, the degree of freedom of rotation is realized by a joint, and in FIG. 2B, the degree of freedom of rotation is realized by bending a film. In addition, when the expansion and contraction of the film cannot be ignored or when the gap of the element is long and the deflection of the film cannot be ignored, the configuration of FIG. In this embodiment, an explanation will be given by taking as an example a case where expansion and contraction and deflection are sufficiently small.

  As shown in FIG. 3, the fixation to the subject is fixed to the subject with several fixing bands 101. Since the connecting portion of the probe array is flexible, it is possible to obtain a long-term monitoring that is fixed across the joint of the subject and a tomographic image while the joint is moving. Until now, the heart has been mainly used for the observation of the movement in the living body by the ultrasonic imaging. However, the application of the configuration of this embodiment makes the ultrasonic imaging effective for the orthopedic observation. In addition, since the living body is always accompanied by deformation, making the probe flexible reduces the sense of discomfort caused by the contact of the probe and the contact of the probe, and prevents the contact from becoming worse. I can do it.

As for the transducer, a PZT (lead titanium zirconate) element is used as shown in FIG. 4A, a PVDF (polyvinylidene fluoride) element as shown in FIG. 4B, or a cMUT (capacitive micro- machined ultrasound transducer) elements can be used. Here, the case of a film type corresponding to FIG. 2B will be described as an example in the following order. First, (a) When PZT is used PZT has an acoustic impedance of about 30 MRayl, which is significantly different from 1.5 MRayl of a living body, and therefore has an intermediate acoustic impedance (usually higher than that of metal particles or metal oxide particles or ceramic powder). The acoustic matching layer 8 (which adjusts the sound speed and density by using a mixture of molecular resins) is formed on one or two layers of the PZT on the transmission surface side, and on that, the acoustic for focusing in the direction orthogonal to the electronic focus is performed. The lens 1 is formed. The acoustic lens uses a silicone rubber or a mixture of silicone rubber and particles whose sound speed is slower than that of a living body, and thus is an extremely flexible material. This acoustic lens 1 plays the role of the flexible sheet of FIG. On the back surface of the PZT piezoelectric element, a backing material made of a mixture of a metal or metal oxide and a polymer material having a large damping coefficient such as rubber is formed as a damping material. This suppresses unnecessary responses caused by the return of the ultrasonic pulse radiated from the back surface, and by selecting an appropriate acoustic impedance as a load, the ultrasonic pulse has a reverberation and the time resolution is reduced. Prevents deterioration. By connecting these piezoelectric elements, matching layers, and elements formed from the backing material via a sheet member (flexible sheet), the entire array can be flexibly deformed. As the piezoelectric element, in addition to using PZT, as shown in (b), a polymer piezoelectric film such as polyvinylidene fluoride can also be used. In this case, a flexible probe array can be realized by sandwiching the piezoelectric film 10 between the acoustic lens 1 and the backing material 4 and using a patterned electrode on one side of the electrode. In this case, there is an advantage that manufacture is easier than other methods. There is also a method of utilizing cMUT as an electroacoustic transducer. In this case, as shown in (c), the cMUT element 12 formed on the silicon substrate is also sandwiched between the backing material 4 and the acoustic lens 1, and the rest can be realized in the same manner as described above.
As shown in FIG. 2A, the same effect can be obtained even if elements formed of a piezoelectric element, a matching layer, and a backing material are connected via a joint (connecting portion). An enlarged view of this element is shown in FIG. Here, a case of a structure like a caterpillar will be described as an example. The joint 3 (here, the shaft is inserted into the hole of the joint 3) between the acoustic element 2 mainly composed of the acoustic lens 1, the matching layer 8, the piezoelectric element 7, and the backing material 4, and the acoustic element 2 adjacent thereto. , Rotation about this shaft becomes possible.), And is composed of an upper wiring 6b and a lower wiring 6a connected to the upper and lower electrodes of the piezoelectric element. In order to achieve acoustic isolation and not hinder mobility between elements, a material in which a gas is mixed into a resin having a small acoustic impedance such as silicone rubber may be poured. In order to mix the gas, a micro balloon having a shell structure enclosing gas or a material such as urethane foam can be used. For example, an organic microballoon having a thermoplastic resin outer shell known as the trade name EXPANCEL and having a particle size of about 10 to 100 microns can be used. This filler also contributes to maintaining the strength of the probe array. The piezoelectric element 7 may be the aforementioned PZT piezoelectric material, a polymer piezoelectric film, or a cMUT. In order not to affect the mobility of the joint 3, the wiring 6 is taken out in a direction parallel to the rotation axis of the joint, connected to a coaxial cable or a flexible printed circuit board with a GND pattern, and bundled in the entire cable. Connect to the device.
Next, a method for estimating the shape of the transducer itself and taking a tomographic image using the flexible transducer described so far will be described.
(1) First, an ultrasonic wave is transmitted to an object without knowing the shape of the subject, and a signal is acquired for each reception channel.
(2) Next, receive beamforming is performed based on the assumed initial shape, and an initial point response function is obtained. This is PSF ₀ .
(3) A search for iteratively estimating the probe shape is performed so that PSF ₀ is optimal.
(4) When the estimation of the probe shape is completed, a transmission beam is formed, ultrasonic waves are transmitted to the object, and reception beam forming based on the shape estimation result is performed on the reception echo.
(5) A tomogram is generated and displayed on a display through normal envelope detection, filtering processing, log compression, and scan conversion processing.
(6) Perform a few processes as appropriate at a frequency according to the likelihood of a change in the shape of the probe, and perform imaging while updating the shape estimation result.
Next, the PSF ₀ optimization process, which is different from the imaging by the probe in which the present embodiment is assumed to be a rigid body, will be described. As shown in FIG. 1, ultrasonic beam forming provides the delay time calculated for each element by determining the distance between the focal point and each element position and dividing the distance difference between the elements by the sound velocity of the object. This is realized by performing addition between channels. It is known that the point response function obtained in this way is the minimum (both azimuth and propagation directions) when the delay time is most correct. Therefore, try changing the delay time pattern to minimize the point response function. What is necessary is just to obtain the delay time pattern. Here, the minimum point response function means the minimum width of the point response function. Depending on the situation, the width in the depth direction is minimized, the width in the azimuth direction is minimized, the arithmetic average of both It is appropriate to minimize the geometric mean. The case of calculating sequentially from the end will be described with reference to FIG. With the element at the end as the origin, the element interval is P, the angle of the i-th element is Θ _i , and the rotation angle of the i-1th joint is θ _i-1 , the i-th element position (X _i , Y _i) are i-1 th element position with (X _i-1, Y _i-1) and the rotation angle _{Θ i-1, (X i} -1 + P / 2cosΘ i-1 + P / 2cos (Θ _{i-1 + θ i-1} ), Y i-1 + P / 2sinΘ it-1 + P / 2sin (Θ i-1 + θ i-1)) and can be calculated.
That is, as one method, first, an estimated delay time is given to the received signal of the second element with the degree of freedom as the two parameters of Θ ₁ and θ ₁ for the receiving beam at the extreme end, addition is performed, and ch1 And Θ ₁ and θ ₁ are obtained so that the point response function is minimized. After that, it is possible to obtain Θ and θ of the entire element by sequentially obtaining the element position using a mathematical induction method.

  However, especially when the delay time is estimated with the first few elements, it is difficult to form a beam, and the estimation accuracy of Θ and θ is lowered.

  Therefore, instead of estimating sequentially from the end, a method of increasing the number of divisions gradually can be taken. This will be described with reference to FIG. For example, when the number of channels in the aperture is 128, first, delay addition based on the initial estimated shape is performed in the left half and the right half, respectively. Next, the joint angle between the left half addition signal and the right half addition signal is estimated so that the point response function is minimized. After this estimation is completed, the left and right apertures are divided in half, and the delay time between 1/4 and 2/4 is estimated, and the delay time between 3/4 and 4/4 is estimated. In this way, the estimation accuracy is improved while sequentially increasing the number of divisions. In other words, to divide the aperture here means to bundle elements having spatially close positions. For example, when there are 128 channels in the aperture, first dividing the aperture into two means that 1 to 63 channels are bundled together and 64 to 128 channels are bundled together. Next, when the aperture is divided into four, it is bundled into four from 1 to 31, 32 to 63, 64 to 95, and 96 to 128 ch. This is an operation of making this successively finer.

As a method having the same effect as this method, it is assumed that the delay time function can be expressed by a polynomial of F (x) = Σa _n x ⁿ and x, and F (x) is first assumed that n is 0. estimation, that is, the _{a 0.} Next, a ₁ and a ₀ are estimated based on this estimation result, and n is increased thereafter. These methods are effective when the high spatial frequency component is not included in the spatial frequency component of the array shape.

  In addition, in order to correct the phenomenon that the focus is blurred due to non-uniform sound speed of the living body, there is a beam forming method called adaptive image reproduction that detects the phase shift of the received signal between adjacent elements and replaces it with the corrected delay time. is there. In this embodiment, the probe shape is estimated based on the received signal, and the shape deformation is estimated, but at the same time, the biological sound speed non-uniformity correction is also performed.

  In this embodiment, the evaluation function is IV. A function for calculating cross-correlation between adjacent signals is considered, the evaluation method corresponds to all of the above I to III, and the flexibility (constraint condition) is I.I. Consider only rotation.

  In Example 1, using the point response function as an evaluation function, the delay time distribution at which the evaluation function is optimal was considered to be a delay time distribution reflecting the probe shape. This can be said to be a method for obtaining the optimum result. On the other hand, there is also a method for obtaining the delay time distribution without using the evaluation function as in the first embodiment. This is a method of obtaining a complex cross-correlation for each received signal of each channel and obtaining a delay time distribution from the phase difference. If the signal-to-noise ratio is not sufficient with only the received signal of 1ch, a method of obtaining a cross-correlation after adding the signals for each of a plurality of adjacent elements and improving the signal-to-noise ratio is also effective. Before performing cross-correlation, a time window function is added to the received signal, then cross-correlation is performed, and the center position of this window function is shifted to obtain a different delay time distribution for each depth. It is possible to improve the estimation accuracy of the delay time by the method of obtaining the average after removing the low estimation result. When bundling elements, if N is the number of elements to be bundled, the effect of noise decreases as N increases, but the spatial resolution of element position estimation decreases. In addition, it is necessary to optimize the optimum number of bundles. Alternatively, the position may be estimated purely by cross-correlation, or an element shape function having a plurality of parameters that are not determined in advance is assumed, and this function is used to calculate the least square with respect to the element position obtained from the cross-correlation function. There is also a method of determining the element shape by fitting. In the case of the present embodiment, the point that it can cope with various element shapes is advantageous as compared with the above-described method, but there are disadvantages such as high calculation processing cost and being easily affected by noise. The cross-correlation calculation may take convolution, but in the case of a complex function, the division may be performed when the phase difference is to be obtained, or the arctan is obtained by the real part and the imaginary part, and the phase difference is obtained. Well, there are several possible ways.

  In this embodiment, as the flexibility (constraint condition), II. Rotation and expansion / contraction are examined.

In the embodiments so far, only the angle is changed as a joint, but when the target part is a living body joint or the like, it is necessary not only to rotate but also to expand and contract to always be in close contact with the joint. There is. In this case, the joint 3 does not rotate as shown in FIG. 11, but a joint that can be expanded and contracted and rotated can be configured by using, for example, a spring. An example is shown in FIG. Adjacent acoustic elements 2 are connected by a spring 15. If the spring is exposed, foreign matter may enter the gap, which is undesirable for hygiene purposes. Therefore, the front and back surfaces are sandwiched between flexible polymer sheets 16 so that the spring 15 is not exposed. . In this case, with the endmost element as the origin, the interval between i-1 and the i-th element is P _i-1 , the angle of the i-th element is Θ _i , and the rotation angle of the i-1th joint is θ _i- When _1, i-th element position (X _i, Y _i) by using i-1 th element position (X _i-1, Y _i-1) and the rotation angle Θ _i-1, (X _{i -1} + P _i-1 / 2 cos Θ _i-1 + P _i-1 / 2 cos (Θ _i-1 + θ _i-1 ), Y _i-1 + P _i-1 / 2sin Θ _i-1 + P _i-1 / 2sin (Θ _{i -1} + θ _i-1 )). This optimum value is not mathematically obtained, but it is possible to obtain the minimum value within the search range.
Further, as described in the previous embodiment, if the cross-correlation is obtained between the received signals of each channel and the delay time difference is estimated, it can be obtained even if the element position model is as described above. Therefore, in the present embodiment, a method for estimating the shape by cross-correlation is suitable.

  In this embodiment, the element width and the width of the interval between the elements are set to be different at least in a part.

  In the configuration described in the first embodiment, since a joint or the like is provided between the elements, the element spacing is increased as compared with a normal array. As is well known in the array, no grating lobe is generated when the element spacing P is a wavelength λ and P <λ / 2, but a grating lobe is generated when P> λ / 2. In P to λ / 2, even if a grating lobe occurs, the angle is large from the normal vector direction of the probe transmission surface, and this is not a problem in tomographic imaging. However, the grating lobes can cause artifacts on the image as P-3 / 4λ approaches λ. For example, when the array is driven at 5 MHz, the wavelength is 0.308 mm when the sound speed of the living body is 1540 m / s. For this reason, even if the element width is 0.2 mm, a grating lobe is generated when there is a gap of about 0.1 mm between the elements due to the formation of a joint. In order to avoid this, as shown in FIG. 7, by setting the element width and the indirect width between the elements to be different at least in some places, the positions of the grating lobes are dispersed, and the artifact strength is reduced. I can do it. In order to change the element spacing, the element width may be changed randomly as shown in FIG. Further, the width of the gap may be changed randomly as shown in FIG. Further, the number of elements between the joints may be changed randomly as shown in FIG. In the case of FIG. 7A, when thickness vibration such as PZT is used, the ratio between the thickness and the element width affects the vibration mode. However, when thickness vibration is not used like cMUT, it is relatively easy to change the element width. In addition, when one electrical element is formed from a plurality of acoustic elements such as a cMUT or a sub-die vibrator, the acoustic characteristics can be changed by changing the number of acoustic elements bundled together. The element width of the electric element can be changed while maintaining the above. In the cases of (b) and (c), even if the element spacing is changed randomly, there is little possibility of affecting the acoustic behavior of the element.

In the embodiments so far, explanation has been given regarding a flexible transducer characterized by good contact with a living body. However, even in a probe used in the body, the effect of having a flexible shape is great. As an advantage of imaging with a probe in the body, imaging can be performed from a position closer to the observation target, and thus has the following advantages.
(1) Since the propagation distance is short and it is not necessary to go through the skin, a high frequency that is more susceptible to the influence of attenuation can be selected. For this reason, spatial resolution can be improved.
(2) Since the beam can be narrowed as the focal length / aperture width is smaller, the resolution of the beam can be improved by making the focal length fine.
(3) Since attenuation due to propagation is reduced, a signal with originally low sensitivity, such as a signal from a blood cell, can be acquired with a relatively good signal-to-noise ratio.
Since the intervening tissue between (4) is reduced, the relative movement of the target region and the probe can be reduced. Accordingly, elastography imaging for measuring the hardness of the subject is facilitated, and clutter removal in Doppler imaging is facilitated.
However, as mentioned in (2), it is necessary to secure the aperture width. On the other hand, when it is introduced into the living body, it is necessary to approach through the oral cavity, make a hole in the body surface, translaparoscopically approach, or approach from the blood vessel. It is necessary to reduce the width and to reduce the cross-sectional area in a plane perpendicular to the traveling direction. If the size of the space around the introduction portion and the imaging location does not change much, it is not a problem because it is physically difficult to increase the aperture width. However, when introduced orally and imaging the surrounding pancreas, liver, etc. from the stomach, or when introducing into the body via blood vessels and imaging the surroundings from the heart's ventricle or atria, the introduction part There is a spatial margin around the imaging location. In such a case, the merit of folding and introducing into the body, expanding the probe within the body, and widening the aperture is great. In addition, since it is difficult to freely apply ultrasonic jelly in the body, it is also desirable that the shape fits the object, so that the merit of deforming the shape is great.

  Hereinafter, the present embodiment will be described with reference to FIG. In this embodiment, an actuator for controlling the relative positions of a plurality of elements is built in and active deformation is performed. FIG. 8A shows a case where a spatially discrete actuator is used, and FIG. 8B shows a case where a spatially continuous actuator is used. First, regarding a spatially discrete actuator, this corresponds to the caterpillar type element of FIG. 11 and includes an actuator that rotates at the position of the shaft 3 when a voltage is applied. As the actuator, a piezoelectric type, an electromagnetic type or the like can be used. On the other hand, the discrete type can be realized by using a mode in which a voltage application direction and a strain direction of a polymer piezoelectric film such as polyvinylidene fluoride are perpendicular to each other. In any case, it is introduced into the body in a folded state, and is deployed by the force of the actuator until it appropriately contacts the object at the target site. In this case, “appropriate contact” means that either the reaction force from the object related to the actuator or the operating amount of the actuator has reached the threshold first. If all the operating amounts of the actuator are monitored, it is not necessary to estimate the shape from the received beam as described in the previous embodiment. In order to prevent the number of signal lines from becoming enormous, it is possible to monitor the operation amount of the actuator at several places, and the joint deformation between them can be estimated from the received beam.

  In the embodiments so far, the description has been made on the one-dimensional array in which the elements are arranged in one direction. However, this method is also effective for two-dimensional arrays. In particular, the practical value of the folding type array used in the body as in Example 7 is more remarkable in the case of a two-dimensional array that has a large effect of reducing the cross-sectional area by folding. FIG. 9 shows an example of a two-dimensional array provided with joints. In the case of a two-dimensional array, the effect of providing a joint is the effect of reducing the cross-sectional area perpendicular to the direction of travel when bending into the body by bending in the direction 1 in the figure, and bendable in the same directions 1 and 2 This has the effect of improving contactability. In the case of deformation only in the direction 1, it is sufficient that the joint can only rotate. However, in the case of deformation in both the direction 1 and 2, if there is only a degree of freedom of rotation, the transmission surface will be wrinkled. Not practical. Therefore, as described in the fourth embodiment, it is desirable to use a joint having a degree of freedom of rotation and expansion / contraction in at least one direction. Moreover, it goes without saying that the range of selection is further expanded in two dimensions with respect to the evaluation method described at the beginning of the example. For example, without assuming a deformation in one direction (if there is a direction where shape deformation seems to be small, it is desirable to fix the direction first), firstly estimate the deformation in the orthogonal direction, and then The deformation is estimated with respect to the direction in which the initial deformation is not considered. If necessary, the shape estimation accuracy can be increased by repeating this procedure a plurality of times.

Or, to perform two-dimensional shape estimation, select a method that increases the degree of freedom by using a two-dimensional shape estimation function to estimate shape deformation by bundling in a two-dimensional block. You can also. For example, the shape function S (x, y) is decomposed into Sn (x, y) = x ⁿ + x ^n-1 y +... ^N and every ^n- th order term and expressed as S = ΣSn. In this format, the shape can be estimated by sequentially increasing the order from n = 0. As a method similar to this method, S may be a function of r and θ instead of a function of x and y, and a more optimal function may be selected according to an assumed deformation.

  In addition, even if it is two-dimensional, by imposing a constraint condition on the actuator, it is set to be substantially equivalent to one-dimensional deformation, and the method described in the previous examples is used for deformation estimation. You can also.

  As described above, the ultrasonic diagnostic apparatus according to the embodiment to which the present invention is applied has been described. However, the ultrasonic diagnostic apparatus to which the present invention is applied has various other forms without departing from the spirit or main features thereof. Can be implemented. Therefore, the above-mentioned embodiment is only a mere illustration in all points, and is not interpreted limitedly.

FIG. 3 is a diagram illustrating the principle of electronic focus. The figure of the probe array in an Example. The schematic diagram of the fixing method of the probe array in an Example, and the usage method. The schematic diagram at the time of using the various piezoelectric elements in an Example. Explanatory drawing of the function which gives the probe shape in Example 1. FIG. FIG. 3 is an explanatory diagram of a sequential delay time estimation method according to the first embodiment. The figure of the probe array of the random element spacing in Example 4. The figure of the probe array which mixedly mounted the actuator in Example 5. FIG. The figure of the two-dimensional array probe in Example 6. The system block diagram in an Example. The figure of the probe array in an Example. The figure of the probe array in Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Acoustic lens, 2 ... Acoustic element, 3 ... Joint, 4 ... Backing material, 5 ... Flexible sheet, 6 ... Wiring, 7 ... Piezoelectric element, 8 ... Matching layer, 9 ... Filler, 10 ... Piezoelectric film, 11 ... Pattern electrode 12 ... cMUT element formed on a silicon substrate, 13 ... Sheet type actuator, 14 ... Actuator and sensor, 15 ... Spring, 16 ... Polymer film, 100 ... Flexible transducer, 101 ... Fixed band, 102 ... Element, DESCRIPTION OF SYMBOLS 103 ... Movable joint, 104 ... Immovable joint, 201 ... Probe, 202 ... Transmission / reception changeover switch, 203 ... Transmission wave former, 204 ... Control system, 205 ... Transmission waveform memory, 206 ... Reception beam former, 207 ... Element position estimation unit, 208 ... detection unit, 209 ... scan converter, 210 ... display unit

Claims (17)

A probe comprising a plurality of elements that transmit and receive an ultrasonic signal to and from the subject, and a connecting part that relatively movably connects the plurality of elements;
An arithmetic unit that calculates relative position information of the plurality of elements based on reception signals of the plurality of elements;
An ultrasonic imaging apparatus comprising: an image data generation unit configured to generate image data from the received signal and the relative position information.   The ultrasonic imaging apparatus according to claim 1, wherein the calculation unit calculates a rotation angle of the plurality of elements as the relative position information.   The ultrasonic imaging apparatus according to claim 1, wherein the calculation unit calculates shape information of the probe as the relative position information.   The ultrasonic imaging apparatus according to claim 1, wherein the calculation unit includes a storage unit that stores an evaluation function, and an evaluation calculation unit that calculates using the evaluation function read from the storage unit. The ultrasonic imaging apparatus according to claim 1, wherein the storage unit stores a point response function as the evaluation function.   The ultrasonic imaging apparatus according to claim 1, wherein the storage unit stores a function for calculating a cross-correlation of reception signals of the plurality of elements as the evaluation function.   The ultrasonic imaging apparatus according to claim 1, wherein the evaluation calculation unit calculates the delay time of the reception signal by bundling the plurality of elements for each element.   The said evaluation calculating part reads a point response function as the said evaluation function of a received signal, and controls the delay time of the said received signal so that the width | variety of the said point response function may become the minimum. Ultrasonic imaging device.   2. The ultrasonic imaging apparatus according to claim 1, wherein the plurality of elements have different element widths and interval widths at least in a part thereof.   The ultrasonic imaging apparatus according to claim 1, further comprising an actuator that controls a relative position of the plurality of elements.   The ultrasonic imaging apparatus according to claim 1, wherein the plurality of elements are two-dimensional arrays. A plurality of elements for transmitting and receiving ultrasonic signals to and from the subject;
A probe comprising: a connecting portion that relatively movably connects the plurality of elements.   The probe according to claim 12, wherein the plurality of elements have different element widths and interval widths at least in a part thereof.   The probe according to claim 12, wherein the connecting portion is a sheet member, and the plurality of elements are connected via the sheet member.   The probe according to claim 12, further comprising an actuator that controls a relative position of the plurality of elements.   The probe according to claim 12, further comprising a filler disposed between the plurality of elements.   13. The probe according to claim 12, wherein the plurality of elements are any one of a titanium zirconate element, a polyvinylidene fluoride element, and a cMUT element.

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