JP5159803B2 - Subject information acquisition device - Google Patents

Description

The present invention relates to an object information acquisition apparatus that forms an image based on elastic waves generated from an object.

  The photoacoustic imaging method, which is a biological information acquisition method, is a method of detecting an acoustic wave induced inside a living body by irradiating the living body with pulsed laser light and imaging a three-dimensional structure inside the living body. This acoustic wave is generated when the detection target in the living body is irradiated with pulsed laser light and the detection target inside the living body is thermally expanded. Further, by changing the wavelength of the pulse laser beam, it is possible to visualize the distribution of a specific substance having an absorption band such as hemoglobin or glucose in the blood. For this reason, since it is possible to determine non-invasive and potential tumors such as abnormal neovascularization, it has recently attracted attention as a means for screening and early detection of breast cancer.

Conventionally, a specific procedure of the photoacoustic imaging method is disclosed, for example, in Patent Document 1 as follows.
(1) A two-dimensional array electromechanical transducer (transducer) is positioned on the subject surface, and the subject is irradiated with a single pulse of electromagnetic energy.
(2) Immediately after the irradiation of electromagnetic energy, the received signal of each electromechanical transducer is sampled and stored.
(3) For the point r ′ in the subject to be imaged, the delay time for the acoustic wave to reach the position r of each electromechanical transducer element i from the point r ′ is calculated, and each electromechanical transducer element corresponding to the delay time is calculated. The signals are added to obtain the image value at the point r ′.
(4) Repeat step (3) for each point r ′ to be imaged.

  Further, Patent Document 2 discloses a method for reconstructing both a photoacoustic image and a normal ultrasonic echo image using a common one-dimensional array electromechanical transducer, and between the one-dimensional array electromechanical transducer. The structure which arrange | positions the illumination system using a glass fiber is disclosed. In this Patent Document 2, since a one-dimensional array electromechanical transducer is used, in order to reconstruct a three-dimensional image, the one-dimensional array electromechanical transducer is mechanically moved in a direction orthogonal to the array direction. It is necessary to repeat the reconstruction.

JP-T-2001-507952 JP 2005-21380 A

  In order to reconstruct a three-dimensional image using the photoacoustic imaging method, it is desirable to use a two-dimensional array electromechanical transducer in order to reduce the direction dependency of image resolution. As a method for obtaining a photoacoustic image of a wide area on the premise of using a two-dimensional array electromechanical transducer, the following method can be considered. (1) A method of arranging electromechanical transducers over the entire surface of a wide area. (2) A method of mechanical scanning by positioning a relatively small group of electromechanical transducer elements (arrangement of electromechanical transducer elements) in a step-and-repeat manner. However, the method (1) has a problem that the receiving system becomes large and it is difficult to put it to practical use in terms of cost. Further, the method (2) has a problem that non-uniformity in sensitivity occurs between the central portion and the end portion of the two-dimensional array electromechanical transducer. Further, there is a problem that time for positioning to the next position one after another in a step-and-repeat manner is wasted.

Therefore, in the present invention, when an electroacoustic transducer group is mechanically scanned to receive an elastic wave in a wide inspection area, a signal with a uniform sensitivity and a high S / N ratio can be transmitted at high speed while omitting the time for positioning. The photoacoustic imaging apparatus which can be input into is provided.

Photoacoustic imaging apparatus of the present invention in view of the above problems, the electromagnetic wave electro-mechanical transducer that converts into an electric signal by receiving the acoustic wave generated by irradiating the detection object in the object are arrayed From the electromechanical transducer element group, the moving means for moving the electromechanical transducer element group in the arrangement direction of the plurality of electromechanical transducer elements, and at least two or more electromechanical transducer elements among the plurality of electromechanical transducer elements A photoacoustic imaging apparatus for generating a photoacoustic image based on the electric signals added by the adding means , wherein the moving means includes the mechanical electric to receive the acoustic wave while conversion element group is continuously moving, a means for continuously moving the electromechanical conversion element group to the second position from the first position in the arrangement direction, the addition Stage, the electromechanical conversion element group in said first position of the electrical signal converted by receiving acoustic wave, a first electromechanical transducer in a specific position with respect to the subject is converted electric sum signal, of the electrical signals the electromechanical conversion element group is converted by receiving acoustic waves in said second position, and an electric signal by the second electromechanical transducer is in the specific position is obtained by converting the It is a means to do.

According to the present invention, when an electromechanical transducer element group is mechanically scanned to receive an elastic wave in a wide inspection area, a signal with a uniform sensitivity and a high S / N ratio is obtained while omitting the time for positioning. It becomes possible to input at high speed.

It is a figure which shows the principle of the biometric information acquisition apparatus of Embodiment 1. FIG. 3 is a diagram illustrating a method for inputting an acoustic wave in a wide area according to the first embodiment. It is a figure which shows the XY movement mechanism for the mechanical scanning of Embodiment 1. FIG. It is a figure which shows the operation | movement principle of the biometric information acquisition apparatus of Embodiment 1 (when moving a light source and an electromechanical conversion element group integrally). It is a figure for demonstrating the effect of the invention which concerns on Embodiment 1. FIG. It is a figure which shows the principle of operation of the biometric information acquisition apparatus of Embodiment 1 (when fixing a light source and moving a electromechanical conversion element group). It is a figure which shows the specific structure of the received signal process part of the biometric information acquisition apparatus of Embodiment 1. FIG. It is a figure which shows the flowchart of the accumulation addition process of the biometric information acquisition apparatus of Embodiment 1. FIG. It is a figure which shows the time transition of the accumulation addition of the biometric information acquisition apparatus of Embodiment 1 (at the time of 1 element width movement). It is a figure which shows the time transition of the accumulation addition of the biometric information acquisition apparatus of Embodiment 1 (at the time of 2 element width movement). FIG. 6 is a diagram illustrating scanning of a mechanical-electrical conversion element group having a gap according to a second embodiment. It is a figure which shows the time transition of the cumulative addition of the biometric information acquisition apparatus of Embodiment 2 (there is a space | gap. 6 element width movement). It is a figure which shows the time transition of the cumulative addition of the biometric information acquisition apparatus of Embodiment 2 (there is a space | gap. 2 element width movement). 6 is a diagram illustrating a group of electromechanical transducer elements in which a light source is disposed in a gap portion according to Embodiment 2. FIG. It is a figure which shows the electromechanical conversion element group which used the space | gap part of Embodiment 2 as a junction part. It is a figure which shows the method of expressing the received signal arranged in two dimensions in the stripe of Embodiment 3 by a one-dimensional arrangement. It is a figure which shows the time transition when carrying out cumulative addition, moving the stripe of Embodiment 3. FIG. It is a figure which shows the time transition when carrying out cumulative addition using the electromechanical conversion element group with a space | gap of Embodiment 3. FIG. It is a figure which shows another example of the electromechanical conversion element group with a space | gap of Embodiment 3. FIG. It is a figure which shows the example of the arrangement | sequence element comprised combining the one-dimensional arrangement | sequence transmission / reception element for ultrasonic echo images of Embodiment 4, and the two-dimensional arrangement | sequence electromechanical conversion element for photoacoustic imaging methods.

  In the present invention, the elastic wave includes what is called a sound wave, an ultrasonic wave, an acoustic wave, and a photoacoustic wave. For example, an acoustic wave generated inside the subject by irradiating the subject with light that is an electromagnetic wave such as near infrared rays. Waves and ultrasonic waves reflected by transmitting ultrasonic waves inside the subject are included. The elastic wave emitted from the subject includes an elastic wave reflected at at least a portion of the test pair and an elastic wave generated at the portion. That is, the biological information acquisition apparatus of the present invention is a light that irradiates a subject with light that is an electromagnetic wave, receives acoustic waves generated inside the subject with a probe, and displays a tissue image inside the subject. An acoustic imaging apparatus and an ultrasonic apparatus that receives ultrasonic waves transmitted to the inside of the subject and reflected by the detection target and displays a tissue image inside the subject are included.

  In the present invention, a laser is preferable as the electromagnetic wave source. However, the present invention can be implemented not only by laser light but also by electromagnetic waves generally emitted from a light emitting diode or a xenon lamp.

(Embodiment 1)
Hereinafter, Embodiment 1 of the present invention will be described. The biological information acquisition apparatus according to the present embodiment receives a light source as an electromagnetic wave source that generates a pulse laser and an acoustic wave as an elastic wave generated by irradiating the detection target in the subject with the pulse laser from the light source. And a mechanical / electrical conversion element group in which a plurality of mechanical / electrical conversion elements for converting into electrical signals are arranged. Furthermore, the moving means for moving the electromechanical transducer elements in the arrangement direction of the electromechanical transducer elements, the adding means for adding the electrical signals transmitted from the plurality of electromechanical transducer elements, and the addition signal added by the adder means Calculation means for reconstructing (calculating) an image inside the subject based on the calculation means.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the principle of receiving an acoustic signal. In FIG. 1, a subject 6 is fixed so as to be sandwiched from above and below by compression plates 7a and 7b. The subject 6 is irradiated with pulsed laser light from a light source 8 as an electromagnetic wave source that generates a pulsed laser on the compression plate 7a. As a result, the detection target such as hemoglobin inside the subject absorbs the energy of the laser beam, and the temperature of the detection target rises according to the amount of absorbed energy. Due to this, the detection target is instantaneously expanded to generate an acoustic wave. The generated acoustic wave is converted into an electric signal 9 by the electromechanical transducer element group 2 arranged in contact with the lower compression plate 7b and output to the subsequent stage. Note that the light source 8 may be one in which light from a remote light source is guided by a mirror or glass fiber. The light source 8 may be provided integrally with the biological information acquisition apparatus of the present invention, or may be provided separately from the light source 8.

  The light source 8 is preferably a pulse laser light source capable of generating pulsed laser light on the order of several nanometers to several hundred nanoseconds in order to efficiently generate acoustic waves from the detection target. At that time, the wavelength of the pulse laser beam is preferably in the range of 400 nm or more and 1600 nm or less. Furthermore, a region of 700 nm to 1100 nm that absorbs less in the living body is more preferable. As the laser, various lasers such as a solid laser, a gas laser, a dye laser, and a semiconductor laser can be used.

  Next, a method for inputting an acoustic signal in a wide area 3 according to this reception principle will be described with reference to FIG. In FIG. 2, the electromechanical transducer element group 2 includes a plurality of electromechanical transducer elements 1 arranged in a two-dimensional lattice pattern. The reception of the acoustic wave in the wide inspection region 3 moves the electromechanical transducer element group 2 in one direction (X direction) as shown in FIG. 2 to complete the reception of one stripe region 4 and is orthogonal to the moving direction. Move in the direction (Y direction) for positioning. Then, it can be executed by repeating the procedure of moving again and receiving the adjacent stripe region 5. As described above, in the present invention, the electroacoustic transducer elements are moved in the arrangement direction of the electroacoustic transducers when the electroacoustic transducers 1 are arranged in a two-dimensional lattice. Means.

  In addition, the electromechanical transducer 1 of the present embodiment detects an acoustic wave generated from the detection target 13 in the subject that has absorbed a part of the energy of the light irradiated to the subject from the light source, and converts it into an electrical signal. There is a need to. Therefore, it is desirable that the frequency band that can be received by the electromechanical transducer 1 is optimized depending on the size of the detection target in the subject.

  As the electromechanical transducer 1, any detector can be used as long as it can detect acoustic waves, such as a transducer using a piezoelectric phenomenon, a transducer using optical resonance, and a transducer using a change in capacitance. It may be used. For example, when receiving acoustic waves generated from detection objects of various sizes, it is preferable to use a transducer that uses a change in capacitance in a wide detection frequency band or a plurality of transducers that have different detection bands.

  FIG. 3 shows an XY moving mechanism for mechanically scanning the electromechanical transducer element group 2 and the light source 8 along the subject. As shown in FIG. 3, the movement of the present embodiment can be easily realized by a combination of the X-direction moving mechanisms 11a and 11b and the Y-direction moving mechanisms 12a and 12b that move the step-and-repeat in the Y direction. Although the light source 8 may be moved independently of the electromechanical transducer group 2, it is preferable that the light source 8 be moved integrally with the electromechanical transducer group 2 because the range that the ordinary light source can illuminate is limited.

  FIG. 4 is a diagram for explaining the operating principle when the light source 8 and the electromechanical transducer group 2 are moved together. In FIG. 4, 13 is a detection target to be detected such as hemoglobin in the blood, 8a, 8b, 8c and 2a, 2b and 2c are the light source and machine at each time point t = 1, t = 3 and t = 5, respectively. It is an electrical conversion element group (for simplification, the case of t = 2 and t = 4 is omitted).

  When t = 1, the detection target 13 irradiated by the light source 8a generates an acoustic wave, and the acoustic wave that has reached the position of the point P that is a specific position of the subject is electrically converted by the first electromechanical transducer. It is converted into a signal 9a and stored in the temporary storage memory 14a.

  When t = 3, the acoustic wave to be detected irradiated by the light source 8b is converted into the electric signal 9b by the third electromechanical transducer at the position P, which is the same specific position of the subject as when t = 1. It is converted and stored in the temporary storage memory 14b.

  Similarly, at the time point t = 5, at the point P which is a specific position, it is converted into an electrical signal by the fifth electromechanical transducer and stored in the temporary storage memory 14c. At this time, each stored electrical signal is a signal for a certain period after laser irradiation, and is converted into a one-dimensional digital waveform signal by an AD converter (not shown) and stored.

  In the present embodiment, the moving means is located at the position shown in 2a when the t = 1, and the mechanical electricity conversion element group is shown at 2b when t = 3. The electromechanical transducer element group is moved so that the electromechanical transducer element group is positioned at 2c when t = 5.

  That is, the moving means transmits the acoustic wave at the specific position P of the subject with the first mechanoelectric transducer when t = 1, with the third mechanoelectric transducer when t = 3, and t = In the case of 5, the electromechanical transducer element group is moved so as to be received by the fifth electromechanical transducer element.

  Typically, in the present embodiment, the moving means moves the electromechanical transducer element group so that an acoustic wave that reaches a specific position of the subject at a predetermined timing can be received by different electromechanical transducer elements. By moving in this way, it is possible to add an electrical signal caused by an acoustic wave that reaches a specific position of the subject at a predetermined timing.

The movement of the electromechanical transducer group by the moving means of the present embodiment is based on the following idea. That is, if an acoustic wave is received while continuously moving the electromechanical transducer element group, there is a problem that the reception position moves during reception of the acoustic wave. Here, the reception time of the acoustic wave is at most about 50 to 100 μs after irradiation with the pulse laser beam, and is extremely short. On the other hand, the period of pulsed laser beam irradiation is usually limited to a slow period of about 100 ms in order to avoid damage to the living body. Therefore, since the electromechanical transducer has to move at a low speed in accordance with the slow irradiation period, even if the acoustic wave is received while being continuously moved, there is substantially no difference from when it is stopped and received . By receiving while moving continuously as this, omitting the time for positioning and moving time of the electromechanical conversion element group can allow high-speed signal input.

  The stored one-dimensional digital waveform signals are read out in parallel at an appropriate time and added as a one-dimensional waveform signal by the adder circuit 15. If it does in this way, the acoustic signal of the multiple times which reached the same point P from the same detection target 13 will be added, and the SN ratio of the received signal in P point can be improved. At this time, when viewed at the same point P on the subject, the added acoustic signals are those obtained by adding the acoustic wave signals illuminated at relatively different positions as shown in FIG. This is equivalent to an acoustic signal when the three lights 8a, 8b, and 8c are simultaneously emitted. Therefore, the spatial illuminance unevenness of illumination is thereby smoothed, and further improvement in received signal quality can be achieved. In particular, in the case of the method of the present embodiment, since such illumination smoothing is performed everywhere in the stripe, it is possible to reduce illumination unevenness at the boundary portion of the electromechanical transducer element group which is particularly problematic. I can do it.

  Such a feature can be realized by moving in the array direction in both the one-dimensional array and the two-dimensional array of electromechanical transducers. In the case of a two-dimensional array, a plurality of one-dimensional array elements are used. By processing each in parallel, there is an effect of speeding up.

  4 shows an example in which the light source 8 is moved from the position 8a to the position 8c as t = 1 changes to t = 5. However, the light source 8 is moved to a specific position as shown in FIG. It may remain fixed. However, since the range in which the pulse laser beam from the light source 8 is irradiated is limited, it is necessary to move the light source 8 so that at least the pulse laser beam reaches the detection target. That is, it is preferable that the light source 8 moves while maintaining a certain relative position with the electromechanical transducer element group 2 so that the pulsed laser light reaches the detection target.

  In FIG. 4, the acoustic wave that has reached the point P among the acoustic waves generated from the detection target 13 has been described in order to simplify the description. However, since the acoustic wave generated from the detection target 13 actually propagates in each direction, it is detected at a position other than the P point that is a specific position.

  The above contents are summarized as follows.

  The moving means is configured such that the electromechanical transducer element group at the first position (2a) at the first timing (for example, t = 1) and the second position (2b) at the second timing (for example, t = 3). Move to be.

  The electromechanical transducer element group 2 irradiates the detection target with the pulse laser at the first timing (t = 1), and similarly receives the acoustic wave from the detection target at the first position (2a) at the first timing. . Further, the electromechanical transducer element group 2 irradiates the detection target with the pulse laser at the second timing (t = 3), and similarly generates an acoustic wave generated from the detection target at the second timing at the second position (2b). ).

  An adder circuit 15 serving as an adding means adds the next electric signals 9a and 9b. Of the acoustic wave received at the first timing (t = 1), the electrical signal generated by the first electromechanical transducer (first transducer) corresponding to the specific position (point P) of the subject ( 9a). Of the acoustic wave received at the second timing (t = 3), the electrical signal (9b) generated by the second electromechanical transducer (third transducer) corresponding to the specific position (point P).

  Next, a specific configuration of the received signal processing unit will be described with reference to FIG. A computer 21 that controls the whole and reconstructs an image from a received signal is provided at the right end of FIG. 7, and a mechanism for signal input including the subject 6 is provided at the left end. The light source 8 and the electromechanical transducer group 2 are mounted on the stages 23 and 24 and moved by the stage control circuit 22. In this figure, the electromechanical transducer element group 2 uses a 4 × 4 element array as a specific example.

  The light source 8 is controlled to emit light in synchronization with the position of the electromechanical transducer group 2 by the laser control circuit 25, and acoustic wave signals within a predetermined time from the laser emission are input in parallel from 4 × 4 receiving elements. Signals S00, S01, S02, and S03 from four elements arranged in the direction of movement of the arrow in FIG. Converters 27a, 27b, 27c, and 27d convert the signals into one-dimensional digital waveform signals. Then, the temporary storage memories Ma, Mb, Mc, and Md selected by the rotation shift circuit 28 are cumulatively added as waveform signals using the adders 29a, 29b, 29c, and 29d. The one-dimensional digital waveform signal in the temporary storage memory that has been accumulated a predetermined number of times is transferred to the computer 21 via the selection circuits 31 and 32. The signals of the electromechanical transducer elements other than the four elements arranged in the moving direction are also processed in parallel by the same circuit blocks 41, 42, and 43, and transferred to the computer 21 in a time division manner. These series of procedures are controlled by a timing control circuit 26 that receives a command from the computer 21. The computer 21 reconstructs a three-dimensional image at a position corresponding to the reception stripe based on the transferred digital waveform signal.

  FIG. 8 is a flowchart showing specific operations of the rotation shift circuit 28 and the cumulative addition circuit (29a and Ma, 29b and Mb, 29c and Mc, 29d and Md). In the flowchart, since the processes corresponding to the temporary storage memories Ma, Mb, Mc, and Md are all executed in parallel, the processes executed in parallel are shown in each block.

  First, processing corresponding to the temporary storage memory Ma will be described in order. Each block in the flowchart is processed one by one for each period T in which an acoustic wave is received. At the time of t = 4m * T, the temporary storage memory Ma transfers the contents of Ma to the computer 21 and inputs and stores the signal of S00 as it is without performing addition processing. At the time of t = (4m + 1) * T, the S01 signal is added to the contents of Ma as a one-dimensional waveform and stored again. At the time of t = (4m + 2) * T, the S02 signal is added to the contents of Ma as a one-dimensional waveform and stored again. At the time of t = (4m + 3) * T, the S03 signal is added to the contents of Ma as a one-dimensional waveform and stored again. When the process of t = (4m + 3) * T is completed, m is incremented and the process returns to the process of t = 4m * T again. In this way, Ma stores the addition result of four conversion element signals every four periods, and the contents are transferred to the computer 21.

  For the temporary storage memory Mb, as shown in the flowchart of FIG. 8, processing similar to that for the temporary storage memory Ma is executed at a timing shifted by T. The same applies to the temporary storage memories Mc and Md. That is, a signal input from a specific receiving element is associated with the cumulative addition memories Ma, Mb, Mc, Md, Ma,. At this time, since the cumulative addition memory of each signal does not overlap at the same time, the allocation of the received signal can be realized by the rotation shift circuit 28 as described above. In addition, since each memory processes the transfer timing to the computer 21 in order, transfer in a time division manner can be easily performed.

  FIG. 9 shows the time transition of this cumulative addition, with the horizontal axis representing the position in the movement direction and the vertical axis representing the input time. In the figure, four conversion elements are moved in the arrangement direction, and an acoustic signal is input by emitting a laser light source each time the four conversion elements are moved by the width of one element.

  When the acoustic signal is input and accumulated for each position of the subject as described above, the signal can be added four times except for the first part as indicated by the lowest number. Since the signal-to-noise ratio improvement of about twice can be expected by adding the signal four times, if the portion of the four-time addition is input to the computer as an input effective area and used for image reconstruction, a three-dimensional image with an improved SN ratio is obtained. Can be created.

  FIG. 10 is a diagram showing another example of the time transition of cumulative addition. FIG. 10 shows a state in which an acoustic signal is input every time the two-element width is moved. In this case, since the signal is added twice, the improvement rate of the S / N ratio is slightly lower than in the previous example, but the stage speed for scanning the stripe is improved twice. In general, when moving an array element composed of M elements, if one of the divisors of M is d and an acoustic signal is input every time the d element width is moved, an addition signal of M / d times is obtained. The stripe scanning speed increases in proportion to d. The maximum number of additions is M additions when d = 1, and the minimum is one addition when d = M. 9 and 10 have been described using the electromechanical transducer elements one-dimensionally arranged in the moving direction, but in the case of a two-dimensional array element having N element arrays in the direction orthogonal to the moving direction. As described above, N sets of processes are performed in parallel.

  According to the present invention relating to the present embodiment, in a biological information acquisition device that mechanically scans a group of electromechanical transducer elements and inputs an acoustic signal in a wide examination area, a signal having a uniform sensitivity and a high S / N ratio can be obtained at high speed. It becomes possible to input.

  In the present invention, not only can an acoustic wave generated by irradiating an electromagnetic wave in a subject be received, but also an ultrasonic wave transmitted to the subject and reflected by a detection target can be received. For example, in FIG. 6, even if the light source 8 is replaced with an ultrasonic sound source, the ultrasonic waveform reflected at the detection target 13 and reaching the point P is always the same. Therefore, signals of different receiving elements received at the same point P can be added, and the gist of the present invention can be implemented. The ultrasonic sound source may be located at any position as long as it is fixed to the subject. There may be a single ultrasonic sound source or a plurality of ultrasonic sound sources.

(Embodiment 2)
Next, Embodiment 2 of the present invention will be described. In the second embodiment, a different electromechanical transducer element group from that in the first embodiment is used. The rest is the same as in the first embodiment.

  In the electromechanical transducer element group 51 according to the present embodiment, as shown in FIG. 11, six electromechanical transducer elements 52 are arranged in the moving direction with two gaps 53 having a width of 2 elements interposed therebetween. FIG. 12 shows a temporal transition when an acoustic signal is input every time the element width moves by using this electromechanical transducer group. As shown in FIG. 12, in this case, although the electromechanical transducer element group 51 having the gap 53 is used, it is possible to input an acoustic signal added once at successive positions. The electromechanical transducer element group according to the present embodiment typically has a gap having an integer multiple of the arrangement pitch of the electromechanical transducer elements inside the arrangement.

  FIG. 13 shows a temporal transition when an acoustic signal is input every time two element widths are moved using the same electromechanical transducer element group 51 as in FIG. In this case, the acoustic signal can be added three times. In this way, even if there is a gap in the electromechanical transducer element group, the same signal input as in the electromechanical transducer element group without a gap is possible. Therefore, for example, as shown in FIG. 14, by arranging the light source unit 56 in the gap 55 between the electromechanical conversion elements 54, it becomes easy to illuminate the pulse laser beam from the arranged electromechanical conversion element side. In the photoacoustic imaging method, since the attenuation of light intensity inside the subject is large, illumination with pulsed laser light from the arranged electromechanical transducer elements is extremely effective for improving the quality of the reconstructed image.

  Further, when a large electromechanical transducer group having a large number of elements is manufactured, a method of forming a large electromechanical transducer group by joining a plurality of small electromechanical transducer elements that are easy to manufacture is employed. Also in this case, if the boundary portion 57 of the small electromechanical transducer element group as shown in FIG. 15 is configured as the gap portion as described above, there is an advantage that the size of the boundary portion can be increased and the manufacture becomes easy. is there.

  According to the present embodiment, as described above, various input methods are possible by devising the timing of the arrangement of the electromechanical transducer elements and the input of the acoustic signal. Usually, the repetition period of the acoustic signal input is often limited to a certain period or less in order to avoid damage to the subject. Therefore, when high-speed input is required, a method of increasing the moving speed and reducing the number of additions is selected, and when a high-quality signal input is required, a method of decreasing the moving speed and increasing the number of additions is selected. .

(Embodiment 3)
Next, a third embodiment of the present invention will be described. In the third embodiment, in addition to the addition process in the moving direction of the electromechanical transducer element group, the addition process in the direction orthogonal to the moving direction of the electromechanical transducer element group is also performed. The rest is the same as in Embodiments 1 and 2 above.

  When an acoustic signal is input using a group of M electromechanical transducer elements arranged in M in the moving direction and N in the direction orthogonal to the moving direction, the stripe length of N widths is obtained when one movement is completed. The number of signal waveforms corresponding to is input to the computer. Next, if adjacent stripes are set so as to overlap some areas, and an acoustic wave signal is similarly input by continuous movement and taken into a computer, the data of the overlapping areas can be added on the computer.

  Referring to FIG. 16, when the input signal waveforms are combined in the moving direction and expressed by one small rectangular area as shown in FIG. 16, the acoustic wave data 58 of the stripe 4 is N pieces continuous in the vertical direction (FIG. 16). In the case of (4), it can be represented by 4) small rectangles 59. FIG. 17 illustrates the temporal transition of the addition process using this expression. FIG. 17 shows an example in which a signal is input using a two-dimensional array element of N = 4 while shifting the stripe position by the vertical width of one element. Even in this case, if a computer is used, four times of movement addition can be performed as in the case of the continuous movement described above.

  FIG. 18A shows an example in which the electromechanical transducer element group 60 having the gap region 62 in the electromechanical transducer element region 61 in the direction orthogonal to the moving direction (stripe moving direction) is used. Also in this case, as in the case of the moving direction, the cumulative addition can be performed three times by shifting the stripe position by the vertical width of two elements as shown in FIG.

  FIG. 19 shows an example of the electromechanical transducer element group 65 in which the gap 64 is provided in the electromechanical transducer element region 63 in both the moving direction and the orthogonal direction (stripe moving direction). Even in such a mechanical / electrical conversion element group 65, it is possible to execute a positionally dense signal input or addition input for the reason described above.

  If the cumulative addition is performed not only in the moving direction but also in the orthogonal direction (stripe moving direction) using the two-dimensional array electromechanical transducer as described above, the number of added signals is increased, so that the SN ratio is improved. Since illumination unevenness can also be smoothed two-dimensionally, it is possible to reconstruct an image with higher quality.

  Since image reconstruction processing for an input signal is often linear or nearly linear processing, an equivalent effect can be obtained by adding the reconstructed three-dimensional voxel image instead of directly adding the input signal. Is obtained. In this case, since the image reconstruction of the stripe region can be performed while inputting the acoustic signal of the stripe region, the dead time for waiting for the input of the adjacent stripe can be reduced.

(Embodiment 4)
Next, a fourth embodiment of the present invention will be described. In the fourth embodiment, a one-dimensional array transmission / reception element for ultrasonic echo signals (second mechanical / electrical conversion element group) and a mechanical / electrical conversion element group (first mechanical / electrical conversion) for receiving an acoustic wave generated by irradiating electromagnetic waves are used. (Element group) are integrated. The present embodiment is also effective for a diagnostic apparatus that simultaneously generates an ultrasonic echo image and a photoacoustic image. Other points are the same as in the other embodiments.

  In the photoacoustic imaging method, it is desirable to use a two-dimensional array of electromechanical transducer elements in order to achieve isotropic photoacoustic image resolution. Similarly, it is desirable to use a two-dimensional array ultrasonic transmission / reception element in an ultrasonic echo image. However, since the ultrasonic frequency is relatively high, it is necessary to use a large number of small transmission / reception elements, and the two-dimensional array is a large signal processing circuit. There is a problem of increase in cost and cost. For this reason, many practical apparatuses input a three-dimensional ultrasonic echo signal while continuously moving a one-dimensional array of transmitting and receiving elements. Therefore, as shown in FIG. 20, the one-dimensional array transmission / reception element 71 for ultrasonic echo signals and the electromechanical transducer element group 72 in which the electromechanical transducer elements are arranged two-dimensionally are integrated and moved continuously. Quality photoacoustic images and ultrasound echo images can be reconstructed simultaneously.

DESCRIPTION OF SYMBOLS 1 Mechanical-electric conversion element 2, 2a, 2b, 2c Mechanical-electrical conversion element group 6 Subject 8, 8a, 8b, 8c Light source 9, 9a, 9b, 9c Electric signal 13 Detection object 14a, 14b, 14c which generates an acoustic wave Temporary memory 15 Adder circuit

Claims (8)

A group of electromechanical transducer elements in which a plurality of electromechanical transducer elements that receive an elastic wave generated by irradiating an object to be detected in a subject and convert it into an electrical signal;
Moving means for moving the group of electromechanical transducer elements in an arrangement direction of the plurality of electromechanical transducer elements;
Adding means for adding electrical signals transmitted from at least two or more electromechanical transducer elements among the plurality of electromechanical transducer elements;
The moving means is means for continuously moving the electromechanical transducer element group from a first position to a second position in the arrangement direction so as to receive an elastic wave while the electromechanical transducer element group continuously moves. ,
The adding means includes
Image reconstruction processing in which the first mechanoelectric transducer at a specific position with respect to the subject is transformed out of the electric signal that is received and converted by the electromechanical transducer element at the first position. With the previous electrical signal,
Among the electrical signals converted by receiving the elastic wave at the second position, the group of electromechanical transducer elements converts the electrical signal before the image reconstruction process converted by the second electromechanical transducer element at the specific position; The object information acquiring apparatus characterized by being means for adding.   The object information acquiring apparatus according to claim 1, wherein the electrical signal added by the adding unit is a digitally converted electrical signal before image reconstruction processing.   3. The subject information acquiring apparatus according to claim 1, wherein the electromechanical transducer elements of the electromechanical transducer element group are arranged in a two-dimensional lattice pattern.   Also in the direction orthogonal to the direction of continuous movement of the electromechanical transducer elements group, the electromechanical transducer elements different from each other receive the elastic wave at the specific position and add the electrical signal before the image reconstruction process by the adding means. The object information acquiring apparatus according to claim 1, wherein the object information acquiring apparatus is an object information acquiring apparatus. An electromagnetic wave source configured to irradiate a first electromagnetic wave at a first time and to irradiate a second electromagnetic wave at a second time after the first time;
The elastic wave received at the first position is an elastic wave generated by the first electromagnetic wave,
5. The subject information acquisition apparatus according to claim 1, wherein the elastic wave received at the second position is an elastic wave generated by the second electromagnetic wave. 6.   The object information acquiring apparatus according to claim 5, wherein a range in which the electromagnetic wave source illuminates the object moves while maintaining a certain relative position with respect to the electromechanical transducer element group.   The object information according to claim 1, wherein a distance between the first position and the second position is an integer multiple of an element width of the electromechanical transducer. Acquisition device. Based on the electric signal which the adding means is added to output, by performing the image reconstruction processing, in any one of claims 1 to 7, characterized in that it has a calculation means for forming a photoacoustic image The subject information acquisition apparatus described.

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