JP2017080466A - Subject information acquisition device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an influence which is exerted on an optical sensor by an electromagnetic noise from a light source, when performing photoacoustic measurement.SOLUTION: An analyte information acquisition device comprises: a light source unit 102 comprising light sources 126, 127 and a drive circuit 132 for driving the light sources; a probe 111 for receiving emission of light emitted from the light sources and converting an acoustic wave generated from an analyte into an electric signal; light detection means 117, 118 for detecting the light emitted from the light sources for generating a trigger signal; a controller 103 for receiving the trigger signal from the light detection means and the electric signal from the probe, and generating characteristic information of inside of the analyte; and a housing for intercepting an electromagnetic noise produced from the light source unit. The housing stores the light detection means in a manner of separating the light source unit from the light detection means.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a subject information acquisition apparatus.

  2. Description of the Related Art Conventionally, in the medical field, a photoacoustic apparatus that images the form and function of a subject using a photoacoustic effect has been studied. In such a conventional photoacoustic apparatus, when a user's instruction is received, a controller inside the photoacoustic apparatus sends a signal to the drive circuit of the light source to emit pulsed light. When this pulsed light is applied to the subject via the light guide means, a photoacoustic wave is generated. This photoacoustic wave is received by the probe in contact with the subject and converted into an electrical signal called a photoacoustic signal. The controller performs signal processing and image reconstruction processing on the photoacoustic signal, and presents a diagnostic image to the user.

  In a conventional photoacoustic apparatus, it is necessary to irradiate a subject with a sufficient amount of pulsed light in order to improve the contrast of a diagnostic image. Therefore, a high-power laser is used as the light source. High voltage and large current are required to drive the flash lamp and Q switch inside the laser.

  Further, since there are individual differences and aging changes in the light source, there is a variation in the time from when the controller sends a drive signal until the pulsed light is actually emitted, and the emission timing of the pulsed light is not constant. In view of this, a photoacoustic apparatus that can detect the emission timing of pulsed light by providing an optical sensor has been proposed (Patent Document 1). In the photoacoustic apparatus of patent document 1, a part of pulsed light is guide | induced to an optical sensor, and light emission timing is detected. Then, in synchronization with the light emission timing detected by the optical sensor, the receiving circuit controls the start and stop of photoacoustic signal reception. Further, the position of the light absorption site inside the subject is estimated based on the time difference between the light emission timing and the received signal, and image reconstruction is performed.

  When the light source is a high-power laser as described above, generally, the light source, the light guide means and the optical sensor are placed in one housing so that the pulsed light does not leak out of the housing. The safety of the equipment is ensured. An optical member such as a beam splitter or a mirror is used as the light guiding means, and the pulsed light is branched and guided to the optical sensor.

  On the other hand, in the field of lighting devices, a device using a bundle fiber as a light guiding means has been proposed (Patent Document 2).

JP 2011-229556 A JP 2001-174410 A

When driving a light source in a conventional photoacoustic apparatus, electromagnetic noise from a light source driving circuit that handles a high voltage and a large current may wrap around the photosensor. As a result, the optical sensor malfunctions, and the synchronization process between the light emission timing and the photoacoustic wave reception is adversely affected, and the state inside the subject may not be accurately imaged. In order to prevent this, it is conceivable to take measures against noise with a shield member or the like on the optical sensor. However, since there is a large amount of electromagnetic noise from the light source and there are places where electromagnetic shielding is difficult, such as openings and connectors, the effect of suppressing the influence of electromagnetic noise is limited.

  This invention is made | formed in view of the said subject, The objective is to suppress the influence which the electromagnetic noise from a light source exerts on a photosensor when performing a photoacoustic measurement.

  The present invention employs the following configuration. That is, a light source unit including a light source and a drive circuit that drives the light source, a probe that receives an irradiation of light emitted from the light source and converts an acoustic wave generated from a subject into an electrical signal, and A light detection means for detecting a light emitted from a light source to generate a trigger signal; the trigger signal from the light detection means; and the electrical signal from the probe; A controller for generating information; and a housing for shielding electromagnetic noise generated from the light source unit, wherein the housing stores the light detection means so as to isolate the light source unit and the light detection means. An object information acquiring apparatus characterized by the above.

  ADVANTAGE OF THE INVENTION According to this invention, when performing a photoacoustic measurement, the influence which the electromagnetic noise from a light source has on an optical sensor can be suppressed.

The block block diagram in Example 1 of this invention. The operation | movement flowchart in Example 1 of this invention. The figure which shows the controller internal structure in Example 1 of this invention. The block diagram of the bundle fiber in Example 1 of this invention. The block block diagram in Example 2 of this invention. The block diagram of the probe in Example 2 of this invention. 2 is a timing chart according to Embodiment 1 of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described below should be changed as appropriate according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the following description.

  The photoacoustic apparatus of the present invention uses a photoacoustic effect that receives acoustic waves generated inside a subject by irradiating the subject with light (electromagnetic waves) and acquires characteristic information inside the subject as image data. Device. The characteristic information acquired at this time is the source distribution of acoustic waves generated by light irradiation, the initial sound pressure distribution inside the subject, or the optical energy absorption density distribution, absorption coefficient distribution, and tissue derived from the initial sound pressure distribution. The concentration distribution of the constituent substances is shown. The concentration distribution of the substance is, for example, an oxygen saturation distribution or an oxidized / reduced hemoglobin concentration distribution. Since such characteristic information is also called object information, the photoacoustic apparatus of the present invention can also be called an object information acquiring apparatus.

  The acoustic wave referred to in the present invention is typically an ultrasonic wave, and includes an elastic wave called a sound wave, an ultrasonic wave, or an acoustic wave. An acoustic wave generated by the photoacoustic effect is called a photoacoustic wave or an optical ultrasonic wave. The probe of the subject information acquisition apparatus receives an acoustic wave generated inside the subject.

<Example 1>
In this embodiment, when the emitted light from the light source is guided to the subject, a part of the emitted light is guided to the optical sensor placed in the housing of the receiving circuit.

  FIG. 1 is a block diagram showing a photoacoustic apparatus according to the present embodiment. In FIG. 1, reference numeral 101 denotes a holding unit that fixes a subject and irradiates the subject with pulsed light, receives a photoacoustic wave from the subject, and converts it into a photoacoustic signal. Reference numeral 102 denotes a light source unit including a light source, a light source drive circuit, and an optical system. Reference numeral 103 denotes a controller that receives a photoacoustic signal, performs signal processing and image processing, presents a diagnostic image to the user, and controls operation of the entire apparatus. Reference numeral 104 denotes a subject of the photoacoustic apparatus, which is a part of the body of the subject. Here, a breast will be described as an example.

  Reference numerals 105 and 106 denote optical paths for guiding the pulsed light to the vicinity of the subject, and are constituted by bundle fibers in which a large number of optical fibers are bundled. In this embodiment, an example in which pulse light is irradiated on the subject 104 from two directions will be described. Reference numerals 107 and 108 are optical fibers that are part of the bundle fibers 105 and 106, respectively, and part of the pulsed light to the subject 104 is branched and guided to the controller 103. Reference numeral 109 represents a portion of light absorption (light absorption portion) existing inside the subject, and for example, this is a new blood vessel caused by breast cancer. When the light absorbing portion 109 is irradiated with pulsed light, a photoacoustic wave 110 is generated due to the photoacoustic effect. The bundle fiber corresponds to the light guiding means of the present invention, and part of the optical fiber corresponds to the input means of the present invention.

  Reference numeral 111 denotes a probe which includes a transducer for receiving the photoacoustic wave 110 therein. This transducer is an array of ultrasonic sensor elements such as PZT and CMUT, and converts the photoacoustic wave 110 into a photoacoustic signal that is an electrical signal. In addition, a bundle fiber 105 is connected to the probe 111 so that the subject 104 can be irradiated with pulsed light. Reference numeral 112 denotes a light projecting unit for irradiating the measurement site of the subject with the pulsed light from the direction facing the probe 111. The emitted light from the bundle fiber 106 is enlarged at a predetermined magnification, and the density of the irradiated light. And an optical system for adjusting the irradiation area. A direction from the light projecting unit 112 toward the subject 104 is a Z axis, a horizontal direction (depth direction of the paper surface) of a plane perpendicular to the Z axis is an X axis, and a vertical direction (vertical direction of the paper surface) is a Y axis.

  Reference numeral 113 denotes a plate-like member for compressing and fixing the subject 104, which is located between the subject 104 and the probe 111 and is fixed so as to be in contact with the probe 111. The plate-like member 113 is made of a material having an acoustic impedance close to that of the subject 104 and can transmit the photoacoustic wave 110 to the probe 111 efficiently. Reference numeral 114 denotes a plate-like member for compressing and fixing the subject 104, and the user can move between the light projecting unit 112 and the subject 104 in the Z direction. Accordingly, the subject 104 can be compressed and fixed with various thicknesses according to the size of the subject 104. Further, the plate-like member 114 is composed of a highly light-transmissive member, and can efficiently irradiate the subject 104 with pulsed light.

  Reference numeral 115 denotes a holding mechanism drive unit including a drive circuit and a motor for moving the plate-like member 114 in the Z direction according to a user instruction. The holding mechanism driving unit 115 includes a sensor that measures the thickness of the subject 104 from the distance between the plate-like member 113 and the plate-like member 114. In addition, a proximity sensor that detects whether or not the subject 104 is fixed between the plate-like member 113 and the plate-like member 114 is provided. Reference numeral 116 denotes a stage driving unit including a driving circuit and a motor for two-dimensionally scanning the light projecting unit 112 and the probe 111 on the XY plane. A wide range of diagnostic images can be obtained by scanning the light projecting unit 112 and the probe 111 over the entire subject 104.

Reference numeral 117 denotes an optical input unit including an optical fiber connector, which can connect the optical fiber 107 and the optical fiber 108. When the optical fiber 107 and the optical fiber 108 are connected to the optical input unit 117, the optical fiber is positioned so that the output end of the optical fiber faces the photodiode and the pulsed light enters the photodiode. Reference numeral 118 denotes an optical sensor circuit, which includes a circuit that shapes the current converted by the photodiode and converts it into a digital pulse signal. The optical sensor circuit 118 includes a current-voltage conversion circuit, a comparator, and a Schmitt trigger circuit. The light input unit and the light sensor circuit correspond to the light detection means of the present invention.

  Reference numeral 119 denotes a probe connector for receiving a photoacoustic signal converted by the probe 111, and is constituted by a multi-channel ZIF connector. Reference numeral 120 denotes a receiving circuit that performs signal processing such as amplification, A / D conversion, and noise removal on the photoacoustic signal input via the probe connector 119. The receiving circuit 120 determines A / D conversion processing and stop timing in synchronization with the rising edge of the digital pulse signal from the photosensor circuit 118. Then, a photoacoustic signal is acquired for a certain period and stored in the internal memory 121.

  The control unit 122 is a part that sends instructions to the receiving circuit 120, the holding mechanism driving unit 115, the stage driving unit 116, and the light source driving circuit 132, and performs overall operation control, and is configured by a CPU and software. Reference numeral 123 denotes an image processing circuit, which reads out photoacoustic signal data stored in the memory 121, performs image reconstruction processing, and generates diagnostic image data representing an absorption coefficient distribution inside the subject 104.

  Reference numeral 124 denotes a user interface, that is, an operation unit for the user to set an operation condition of the photoacoustic apparatus and to give an operation start instruction, and includes a keyboard, a mouse, a button switch and the like. The operating conditions include the measurement range of the subject 104 and the measurement time of the photoacoustic signal. In addition, the operation instruction includes the start of imaging of the subject and the interruption of imaging. Reference numeral 125 denotes a display for displaying a diagnostic image to the user and notifying the state of the photoacoustic apparatus.

  Reference numerals 126 and 127 are pulse laser light sources for generating pulsed light, and are constituted by a YAG laser, a titanium sapphire laser, or the like. The pulse laser light source has a flash lamp and a Q switch as means for exciting an internal laser medium, and is configured to be able to electrically control the light emission timing from the outside. The pulse laser light source has an interface for setting the input energy, and is configured to be able to electrically control the energy of the pulsed light from the outside.

  Reference numerals 128 and 129 denote shutters for blocking pulsed light from the light source 126 and the light source 127, respectively. Based on the user's instruction, the shutter can be closed and light irradiation to the subject can be stopped. Optical fiber input units 130 and 131 are parts for inputting pulsed light that has passed through shutter 128 and shutter 129 to bundle fibers 105 and 106, respectively. A member that aligns the optical axis with the incident ends of the bundle fibers 105 and 106 and a magnifying optical system that adjusts the irradiation density and the beam diameter are included.

  Reference numeral 132 denotes a driving circuit for the light source 126, the light source 127, the shutter 128, and the shutter 129, that is, a light source driving circuit. The light source driving circuit 132 turns on the flash lamp at a constant cycle, accumulates excitation energy in the laser medium, turns on the Q switch, and outputs pulsed light having a high energy called a giant pulse. The temperature adjusting unit 133 is an air conditioner or chiller for keeping the internal temperature within a certain range in order to stably perform laser oscillation with the light sources 126 and 127. It is assumed that this temperature range is from 25 degrees to 30 degrees.

The light source unit 102 is shielded from the outside by a housing so that the laser light does not leak to the outside and the internal temperature becomes constant. The pulsed light is applied to the subject 104 from the light projecting unit 112 and the probe 111 in the holding unit. Since the light projecting unit 112 and the probe 111 move on the XY plane, pulse light is transmitted from the light source unit 102 to the holding unit 101 through flexible bundle fibers 105 and 106. A bundle fiber is a bundle of several hundred optical fibers. Several are selected so as to be sparsely distributed in the bundle fibers 105 and 106, and pulse light is transmitted to the controller 103 as optical fibers 107 and 108. In the controller 103, acquisition of the photoacoustic signal from the probe 111 is started in synchronization with the timing at which the pulsed light is received.

  FIG. 2 shows an operation flow of the biopsy apparatus executed by the controller 103. FIG. 7 is a timing chart of control signals from when the controller outputs pulsed light to when it receives a photoacoustic signal.

  In step S <b> 201, the control unit 122 confirms whether or not the measurement is ready based on a signal from the proximity sensor of the holding mechanism driving unit 115. When the subject 104 is fixed between the plate-like members 113 and 114 (S201 = Yes), it is determined that the measurement is ready and the process proceeds to step S203. If the measurement is not ready (S201 = No), the process proceeds to step S202, and after waiting for a predetermined time, the process returns to step S201.

  Subsequently, in step S <b> 203, the CPU 122 reads the setting information designated by the user via the operation unit 124 and records it in the internal memory 121. The setting information includes the number of repeated irradiations at the same measurement position, the measurement range, the pulsed light wavelength, and the like.

Subsequently, in step S <b> 204, the CPU 122 drives the XY stage via the stage driving unit 116 and moves the light projecting unit 112 and the probe 111 to the measurement position of the subject 104.
In step S205, the CPU 122 issues a control signal for opening the shutter 128 and the shutter 129 via the light source driving circuit 132. Thereby, the pulsed light from the laser 126 and the laser 127 reaches the subject 104 via the bundle fibers 105 and 106 and reaches the light input unit 117 via the optical fibers 107 and 108.

  Subsequently, in step S206, the CPU 122 sends a control signal to the light sources 126 and 127 via the light source driving circuit 132 to emit pulsed light. This process will be described in detail with reference to the timing chart of FIG.

  In FIG. 7, reference numeral 701 is a reference pulse signal that rises at a constant period in the control unit 122. Here, it is assumed that the reference pulse signal 701 rises every 100 milliseconds. Here, first, an excitation start signal 702 to the laser 126 is raised at time T722, and an excitation start signal 706 to the laser 127 is raised at time T726, and the flash lamp is turned on to excite the laser medium inside the light source.

  Subsequently, when sufficiently excited, an oscillation start signal 703 to the light source 126 is raised at time T723, and an oscillation start signal to the light source 127 is raised at time T727 to drive the Q switch. As a result, rapid oscillation occurs inside the laser medium, and pulsed light with a large energy is emitted. The light source driving circuit 132 adjusts the timings of the excitation start signal and the oscillation start signal to the light sources 126 and 127, so that the pulsed light beams 704 and 708 are substantially at the same time (T724 and T728) regardless of individual differences among the plurality of light sources. The subject 104 is irradiated with the light. The time width of the pulsed light is about 10 nanoseconds, but the time difference between time T724 and time T728 is adjusted to be 10 nanoseconds or less.

At this time, the pulsed light is input not only to the subject 104 but also to the light input unit 117, converted into the electric pulse signals 705 and 709 by the optical sensor circuit 118, and sent to the receiving circuit 120 at substantially the same time (T725 and time T729). Be notified. There is a delay of several hundred nanoseconds to several microseconds from time T723 to time T724 and from time T727 to time T728, and varies depending on individual differences and aging of flash lamps inside the light source. Therefore, the receiving circuit 120 uses a trigger signal from the optical sensor circuit to detect the timing at which the subject is irradiated with pulsed light.

  Subsequently, the photoacoustic wave generated inside the subject 104 is converted into a photoacoustic signal 711 by the probe 111 and transmitted to the receiving circuit 120 at time T731. This process corresponds to step S207 in FIG. In step S207, the receiving circuit 120 performs A / D conversion on the photoacoustic signal 711 for a predetermined time after the electric pulse signal from the photosensor circuit 118 rises, and stores it in the internal memory. Therefore, the reception circuit 120 raises the conversion start signal 710 to the A / D converter before time T731 when the photoacoustic signal 711 from the subject 104 reaches the reception circuit (T730). Then, the conversion start signal 710 falls at time T733 after time T732 when the photoacoustic signal 711 from the subject has reached the receiving circuit (T733). At that time, addition averaging is performed between signals at the same position on the subject to perform processing to reduce the influence of noise.

  Next, how to obtain time T730 and time T733 will be described. The thickness of the plate-like member 113 is d1 [m], the distance between the plate-like member 113 and the plate-like member 114 is d2 [m], and the average sound speed in the living body is v [m / s]. The values of d1 and v are calculated in advance and stored in the memory 121. The value of d2 is measured by the distance sensor of the holding mechanism driving unit 115. Also, let t1 [s] be the delay required for the trigger signal to reach the receiving circuit after the object 104 is irradiated with the pulsed light.

  At this time, the latter is sufficiently larger in the time required for the pulsed light to reach the light absorbing portion 109 and the time required for the photoacoustic wave 110 to reach the probe 111. Therefore, the interval from time T725 to time T731 can be regarded as d1 / v [s] in consideration of the time that the photoacoustic signal from the subject 104 passes through the plate member 113. The interval from time T725 to time T732 can be regarded as (d2 + d1) / v [s] in consideration of the time required for the photoacoustic signal from the entire subject 104 to arrive. Therefore, the signal processing unit 315 asserts the conversion start signal 710 before time elapses by d1 / v−t1 [s] from time T725 when the trigger signal is input (time T730). Also, the conversion start signal 710 is negated after time (d2 + d1) / v−t1 [s] has elapsed from time T725 (time T733).

  Thereby, all the photoacoustic signals from the subject 104 can be stored in the memory 121 as digital data. These digital data are read by the CPU on the control unit 122, and the data corresponding to the same position on the subject 104 are added and averaged. Subsequently, the image is input to the image processing board 123 and image reconstruction is performed. At this time, if a photoacoustic signal having a high value is received at an early time, it is determined that the light absorption site is at a position close to the probe 111 of the subject 104. On the other hand, if a high-value photoacoustic signal is received at a later time, it is determined that the light absorption site is at a position far from the probe 111 of the subject 104.

Thus, when the data at the time of image reconstruction is acquired based on a malfunctioning trigger signal, the correspondence between the time and the photoacoustic signal is shifted. As a result, there is a possibility that the artifact is drawn at a position different from the actual position on the diagnostic image.
On the other hand, in the present invention, the optical sensor circuit is housed in a housing separate from the light source unit 102, and information is transmitted by pulsed light, thereby preventing a malfunction of the trigger signal due to electromagnetic noise from the lasers 126 and 127.

  Subsequently, returning to the flow of FIG. 2, the description will be continued. In step S208, it is determined whether or not the number of times the photoacoustic signal is stored in the internal memory has reached the number of repeated irradiations read in step S203. If the read value has been reached (S208 = Yes), the process proceeds to step S209, and if not reached (S208 = No), the process returns to step S206. For example, if a value of 3 has been read as the number of repeated irradiations in step S203, the process of step S206 and step S207 is repeated three times, and then the process proceeds to step S209.

  Subsequently, in step S209, it is determined whether or not the measurement of the entire measurement range of the subject 104 has been completed. The measurement range is read in step S203. When the measurement in the entire measurement range is completed (S209 = Yes), the process proceeds to step S210. If there is a position where the measurement has not yet been completed (S209 = No), the process returns to step S204 and the process is continued.

  In step S210, the CPU 122 issues an instruction to the image processing circuit 123, and performs image reconstruction based on the photoacoustic signal data at each measurement position stored in the internal memory of the reception processing circuit 116. Then, a diagnostic image indicating the spectral characteristics inside the living body is output to the display 125.

FIG. 3 shows the configuration of the board inside the controller.
Reference numeral 301 denotes a fiber connector for connecting the optical fiber 107. Reference numeral 302 denotes a fiber connector for connecting the optical fiber 108. A combination of the fiber connectors 301 and 302 corresponds to the light input unit 117.

  Reference numerals 303 and 304 are photodiodes, and light receiving surfaces are arranged on the optical axes of the fiber connector 301 and the fiber connector 302, respectively. Reference numerals 305 and 306 denote current-voltage conversion circuits, which are composed of passive elements such as operational amplifiers and resistors. When the pulsed light is incident on the photodiode, a photocurrent flows, and a voltage proportional to the photocurrent is output by the current-voltage conversion circuits 305 and 306.

  Reference numerals 307 and 308 denote comparators composed of comparison circuits. The comparator compares the output voltages of the current-voltage conversion circuits 305 and 306 with a certain threshold value, and sets the voltage level to a high level only when the threshold value is exceeded. When it is below the threshold, the voltage level is set to a low level. The width of the pulsed light from the light sources 126 and 127 is about 10 nanoseconds. Therefore, the pulse widths of the output voltages of the current-voltage conversion circuits 305 and 306 and the comparators 307 and 308 are also about 10 nanoseconds.

  Reference numerals 309 and 310 denote waveform shapers composed of a waveform shaping circuit. The waveform shaper increases the pulse width from about 10 nanoseconds to about 1 microsecond so that the reception circuit 120 can easily detect the light emission timing. The waveform shaper includes a monostable multivibrator circuit and a buffer circuit. The output pulses of the waveform shapers 309 and 310 are called trigger signals. The trigger signal is input to the trigger branch board 311.

  In general, the receiving circuit 120 is composed of a plurality of substrates. In this embodiment, the probe 111 has 600 ultrasonic sensor elements, and a cable composed of 600 signal lines is input from the probe 111 to the probe connector 119. The receiving circuit 120 is composed of four boards, and each board can digitize 150-channel signals.

  The trigger branch board 311 distributes the output signals of the waveform shaping circuits 309 and 310 to the four receiving circuit boards so that each board operates at the same timing. The trigger branch board is constituted by a high-precision buffer circuit. On the other hand, the photoacoustic signal input to the probe connector 119 is input to the photoacoustic signal branch substrate 312. The photoacoustic signal branching substrate 312 is a substrate for dividing 600 photoacoustic signals into 150 signals and inputting them to four receiving substrates.

  Reference numeral 313 denotes an amplifying unit including a preamplifier for amplifying the photoacoustic signal. The weak photoacoustic signal of about several tens of micro V is amplified to about several milli V by the amplifying unit 313. Reference numeral 314 denotes an A / D conversion unit including an A / D conversion circuit that digitizes the amplified photoacoustic signal. Assume that the start and stop timings of A / D conversion are determined based on a control signal from a signal processing unit described later. Reference numeral 315 is a circuit that performs signal processing on the photoacoustic signal digitized by the A / D converter 314, and is configured by an FPGA. The trigger signal distributed by the trigger branch substrate 311 is input to the signal processing unit 315. These signals correspond to 705 and 709 in FIG.

  When detecting the rising edge of the trigger signal, the signal processing unit 315 asserts an A / D conversion start signal to the A / D conversion unit 314 and starts receiving a photoacoustic signal. Data output from the A / D converter is sequentially stored in the memory 316. The signal processing unit 315 negates the conversion start signal of the A / D conversion unit after storing data in the memory 316 for a time sufficiently longer than the time when the photoacoustic wave from the subject 104 is transmitted to the probe 111. / D conversion is stopped.

  Reference numeral 317 denotes a conductive housing that houses a receiving circuit, a probe connector, a fiber connector, and an optical sensor circuit, and is assumed to be grounded. The material of the housing is copper, iron, aluminum, conductive plastic or the like. In addition, the housing 317 has a minimum gap except for a connector portion connected to the outside, and serves as an electromagnetic shield. Thereby, wraparound of electromagnetic noise from the light source unit 102 and the holding unit 101 can be suppressed. As a result, it is possible to prevent a malfunction in which the optical sensor circuit emits a trigger signal when no pulsed light is emitted. Further, artifacts can be prevented from being mixed into the diagnostic image due to malfunction. Note that the housing is not limited to the form shown in FIG. 3, and at least the optical sensor circuit may be stored so as to be isolated from the light source unit 102. Preferably, the entire controller 103 that is sensitive to electromagnetic noise is housed in a housing and isolated from the light source unit 102.

  At this time, the exterior portion of the probe connector 119 and the exterior portions of the fiber connectors 301 and 302 are insulated from the housing 317. Thereby, it is possible to prevent noise current from the holding unit 101 and the light source unit 102 from propagating to the controller 103 via the exterior shield part of the probe connector or the exterior part of the fiber connector, and the SN ratio of the photoacoustic signal. It leads to improvement.

  In the present embodiment, as described above, the optical input unit and the optical sensor circuit are stored in an electromagnetically shielded housing so as not to be affected by the outside (particularly, a high-output light source). Thus, by arranging the member for detecting light in a housing different from the housing including the light source, the influence of electromagnetic noise can be suppressed.

Further, in this embodiment, the light input unit and the light sensor are stored in a common housing with the controller. Thereby, even if the signal output by detecting light is a weak electric signal, it is not affected by external noise until it is input to the control unit. However, if the member for detecting light can be shielded from noise caused by the light source, the effects of the present invention can be obtained. For example, even if an optical input unit or optical sensor is stored in a housing that is different from a housing that includes a light source and a controller and that transmits an electrical signal to the controller when light is detected, noise caused by the light source Shielding from is possible.

  FIG. 4 is an enlarged view of the bundle fiber incident end of the fiber input unit 130. Reference numeral 401 denotes a frame for collecting a large number of fibers into a circle. Reference numeral 402 indicated by a white circle is an optical fiber that guides pulsed light from the light source unit to the subject 104. The optical fibers 402 are combined to form a bundle fiber 105. Reference numeral 403 indicated by a black circle is an optical fiber that guides pulsed light from the light source unit to the controller 103. The optical fibers 403 are combined into an optical fiber 107 that is a part of the bundle fiber. The optical fibers 403 toward the controller 103 are selected so as to be sparsely distributed in the frame body 401. The number of the optical fibers 403 is selected so that the photodiode 303 is irradiated with a sufficient amount of light to generate the trigger signal.

  Thus, by branching a part of the optical fiber input from the light source unit 102 to the holding unit 101 to the controller 103, the pulsed light can be branched without adding a component such as a beam splitter. In addition, by transmitting an optical fiber between the light source unit 102, the holding unit 101, and the controller 103, an apparatus that is easy to assemble without the need for strict optical path adjustment even when the light source unit is separated from the controller 103 and the holding unit. Can be realized.

  As described above, according to the first embodiment of the present invention, the optical sensor for generating the A / D conversion start timing of the receiving circuit is arranged inside the controller separated from the light source unit. Thereby, the electromagnetic noise from a light source can be prevented and a highly reliable photoacoustic apparatus can be realized.

  In this embodiment, there are two light sources and the example in which the subject is irradiated with pulsed light from two directions has been described. However, the number of light sources and the irradiation direction are not limited thereto. For example, pulsed light from one light source can be branched in the light source unit 102 and irradiated on the subject from two directions. The present invention can also be applied to the case where the subject is irradiated with pulsed light from only one direction. Even when two light sources are provided, the present invention can also be applied to the case where pulse light is irradiated from either the direction of the probe 111 or the direction of the light projecting unit 112.

  In the present embodiment, the example in which light is transmitted from the light source to the holding unit and the controller by the optical fiber has been described. However, the present invention can be applied even if a part or the whole of the light guiding means is replaced with spatial transmission. In this case, if a positioning means for aligning the optical axis, a mirror, a prism for bending the optical path, and the like are appropriately arranged, a photoacoustic apparatus that is less expensive than using an optical fiber can be realized.

  In the present embodiment, the signal processing unit 315 has been described as starting A / D conversion after a predetermined time from receiving the trigger signal from the optical sensor circuit 118 in step S207. However, the content of the processing performed in synchronization with the trigger signal is not limited to this. For example, the A / D conversion unit 314 may be operated at all times, and the signal processing unit 315 may be controlled to store only the signals in the range where the photoacoustic signal exists after receiving the trigger signal in the memory 316.

  In this embodiment, the pulse light is branched by inputting a part of the bundle fiber from the light source unit to the holding unit to the controller. However, the method of branching the pulse light is not limited to this method. For example, pulse light may be branched using a beam splitter in front of the fiber input unit 130 inside the light source unit and guided to the controller 103 using an optical fiber different from the optical fibers 105 and 106.

  In this embodiment, the signal from the photodiode 303 is used to determine the reception timing of the photoacoustic signal. However, the present invention is also applied to the case where the photodiode 303 is used for measuring the light amount and the wavelength. It is possible to apply.

<Example 2>
Next, Example 2 will be described. The difference between the present embodiment and the first embodiment is that the return light reflected by the pulse light applied to the subject is input to the controller. Further, in the first embodiment, the subject is sandwiched and fixed by the plate-like member, and the example of the apparatus that automatically scans the light projecting unit and the probe has been described. However, in this embodiment, the probe is placed on the subject. Will be described using an example of an apparatus in which a user scans the probe along the surface of the subject by hand.

FIG. 5 is a block diagram illustrating a configuration of the photoacoustic apparatus according to the present embodiment.
Reference numeral 501 denotes a light source unit. The difference from the light source unit 102 of the first embodiment is that the number of internal lasers is one instead of two. Reference numeral 502 denotes a controller similar to that of the first embodiment. Since the subject 503, the light absorbing portion 504, the photoacoustic wave 505, and the probe 506 are the same as the subject 104, the light absorbing portion 109, the photoacoustic wave 110, and the probe 111 of the first embodiment, description thereof is omitted. To do.

  Reference numeral 507 denotes a part of the bundle fiber, and is used to guide the pulsed light from the light source unit 501 to the subject 503 via the probe 506. On the other hand, reference numeral 508 denotes a part of the bundle fiber, which is input to the controller 502 and used to detect the light emission timing. In this embodiment, the bundle fiber connected to the probe 506 is branched into two: an optical fiber 507 connected to the light source unit and an optical fiber 508 connected to the controller. Reference numeral 509 denotes a cable for transmitting the photoacoustic signal output from the probe 506 to the controller 502. The cable 509 and the optical fiber 508 can be combined into one cable.

  The optical input unit 510, the optical sensor circuit 511, and the light source driving circuit 522 are the same as the optical input unit 117, the optical sensor circuit 118, and the light source driving circuit 132 of the first embodiment, respectively, but the laser beam is not one system but one system. There are some differences.

  Since the probe connector 512, the receiving circuit 513, and the memory 514 are the same as those in the first embodiment, description thereof is omitted. The control unit 515 is a part (means) that sends instructions to the receiving circuit 513 and the light source driving circuit 522 and controls the entire operation, and is configured by a CPU and software.

  Since the image processing circuit 516, the operation unit 517, and the display 518 are the same as the image processing circuit 123, the operation unit 124, and the display 125 of the first embodiment, description thereof is omitted. Since the laser 519, the shutter 520, the fiber input unit 521, and the temperature adjustment unit 523 are the same as the laser 126, the shutter 128, the fiber input unit 130, and the temperature adjustment unit 133 of the first embodiment, description thereof is omitted.

  The operation of this embodiment is different from that of the first embodiment in that the user manually moves the probe in step S204 in the flow of FIG. However, the other operation flow from light irradiation to photoacoustic signal acquisition is the same as that of the first embodiment.

FIG. 6 is a diagram showing the internal arrangement of the probe 506. Reference numeral 601 denotes an emission end for irradiating the subject 503 with pulsed light from the light source unit 501, and is an emission end of the bundle fibers 507 and 508. Reference numeral 602 denotes a concave lens disposed to face the emission end 601 and adjusts the irradiation density and irradiation pattern of the emitted light from the emission end 601. The pulsed light that has passed through the concave lens 602 has a reduced irradiation density and can be irradiated onto the subject 503. Reference numeral 603 denotes a transducer for receiving a photoacoustic wave and converting it into a photoacoustic signal, and is an array of ultrasonic transducers of several hundred channels arranged in an array.

  A bundle fiber similar to the reference numeral 401 in FIG. 4 is stored inside the emission end 601. Most of the bundle fibers 402 correspond to the optical fiber 507 in FIG. 5 and are connected to the fiber input portion 521 of the light source unit 501. Some sparsely selected optical fibers 403 correspond to the fiber 508 in FIG. 5 and are connected to the optical input 510 in the controller 502.

  The pulsed light from the light source 519 is guided into the probe 506 through the bundle fiber 507 and emitted from the emission end 601 toward the concave lens 602. Then, the subject 503 is irradiated with the pulsed light enlarged by the concave lens 601, and a photoacoustic wave 505 is generated from the light absorbing portion 504. The photoacoustic wave is converted into a photoacoustic signal by the transducer 603 and transmitted to the receiving circuit 513 inside the controller by the cable 509. In the process, part of the pulsed light emitted from 601 is reflected by the surface of the concave lens 602, returns to the emission end 601, and enters the fiber 403. The fibers 403 are combined and connected to the controller 502 as a fiber 508. Therefore, the return light is incident on the optical input unit 510 and the optical sensor circuit 511, and the trigger signal is input to the signal processing unit 315 of the reception circuit 513.

  When detecting the rising edge of the trigger signal, the signal processing unit 315 asserts an A / D conversion start signal to the A / D conversion unit 314 and starts receiving a photoacoustic signal. Data output from the A / D converter is sequentially stored in the memory 316. The signal processing unit 315 stores data in the memory 316 for a time sufficiently longer than the time for which the photoacoustic wave from the subject 503 is transmitted to the probe 111. Thereafter, the conversion start signal of the A / D conversion unit is negated, and A / D conversion is stopped.

  A method for obtaining the time T730 and the time T733 in this embodiment will be described. It is assumed that the distance between the transducer 603 and the subject 503 is d3, the thickness of the subject is d4 [m], and the average sound velocity in the living body is v [m / s]. Also, let t1 [s] be the delay required for the trigger signal to reach the receiving circuit after the object 104 is irradiated with the pulsed light. The values of d3, d4, and v are calculated in advance and stored in the memory 514.

  At this time, the latter is sufficiently larger in the time required for the pulsed light to reach the light absorbing portion 504 and the time required for the photoacoustic wave 505 or the probe 506 to reach. Therefore, the interval from time T725 to time T731 can be regarded as d3 / v [s] in consideration of the time during which the photoacoustic signal from the subject 104 propagates. The interval from time T725 to time T732 can be regarded as (d3 + d4) / v [s] in consideration of the time for propagation of the photoacoustic signal from the entire subject 104. Therefore, the signal processing unit 315 asserts the conversion start signal 710 before time elapses by d3 / v-t1 [s] from time T725 when the trigger signal is input (time T730). Also, the conversion start signal 710 is negated after time (d3 + d4) / v−t1 [s] has elapsed from time T725 (time T733). Thereby, all the photoacoustic signals from the subject 104 can be stored in the memory 316 as digital data. These digital data are read by the CPU on the control board 122, and the data corresponding to the same position on the subject 104 are added and averaged.

  Also in this embodiment, by introducing light into the shielded housing and defining the reception timing of the photoacoustic wave, it is possible to obtain a good diagnostic image while suppressing the influence from the high voltage, large current laser light source. It is possible to enjoy the effects of the present invention.

Furthermore, in this embodiment, by inputting a part of the return light from the probe 508 to the controller 502, not only the timing of light irradiation but also whether or not the pulsed light reaches the subject 503 is detected. can do.
When there is a disconnection failure of the bundle fiber 507 or a failure at the emission end 601, the control unit 515 emits the laser 519 via the light source driving circuit 522 and the subject 520 is opened despite the shutter 520 being opened. There may be a problem that the pulse light does not reach correctly. However, even in such a case, with the photoacoustic apparatus having the configuration of the present embodiment, it is possible to detect a defect in which the pulsed light does not reach the subject correctly and improve the reliability of the apparatus. Can do.

  In the present embodiment, the signal processing unit 315 has been described as starting A / D conversion after a predetermined time from receiving the trigger signal from the optical sensor circuit 118 in step S207. However, the content of the processing performed in synchronization with the trigger signal is not limited to this.

  For example, it is conceivable that the signal processing unit 315 starts A / D conversion simultaneously with the time 723 when the control unit 515 drives the Q switch of the laser 519 via the light source driving circuit 522. Then, after the trigger signal is received, control may be performed so that only the signal in the range (time T731 to T732) where the photoacoustic signal exists is stored in the memory 316. By starting A / D conversion before irradiating pulse light in this way, the photoacoustic signal reaches the probe before the trigger signal due to a large delay in the optical sensor circuit. The photoacoustic signal from the subject can be acquired without missing.

  102: light source unit, 103: controller, 105: bundle fiber, 106: bundle fiber, 107: optical fiber, 108: optical fiber, 111: probe, 117: optical input unit, 118: optical sensor circuit, 122: control Part, 123: image processing circuit, 126: light source, 127: light source

Claims (6)

A light source unit comprising a light source and a drive circuit for driving the light source;
A probe that converts the acoustic wave generated from the subject to the irradiation of the light emitted from the light source into an electrical signal;
Light detecting means for detecting light emitted from the light source and generating a trigger signal;
A controller that receives the trigger signal from the light detection means and the electrical signal from the probe, and generates characteristic information inside the subject;
A housing that shields electromagnetic noise generated from the light source unit;
The object information acquisition apparatus according to claim 1, wherein the housing stores the light detection means so as to isolate the light source unit and the light detection means. A light guide means for guiding the light emitted from the light source to the subject;
Input means for inputting light emitted from the light source into the housing;
Further comprising
The light guiding means is a bundle fiber,
The object information acquiring apparatus according to claim 1, wherein the input unit is a part of a bundle fiber. The object information acquiring apparatus according to claim 2, wherein the input unit divides a part of light irradiated to the subject from the light source and inputs the branched light to the housing. The object information acquiring apparatus according to claim 2, wherein the input unit inputs light reflected from the light guide unit and then reflected on the object to the housing.   The object information acquiring apparatus according to claim 1, wherein the housing that stores the light detection unit also stores the controller. The controller determines, based on the trigger signal, a portion based on the acoustic wave generated from the subject in the electrical signal, and uses the portion of the electrical signal based on the acoustic wave generated from the subject to perform characteristics inside the subject. The object information acquiring apparatus according to claim 1, wherein the information is generated.

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