JP2870888B2 - Photoacoustic imaging device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a photoacoustic imaging apparatus, and more particularly, to a photoacoustic imaging apparatus that performs image processing based on a photoacoustic signal emitted from a sample by irradiating the sample with light. The present invention relates to an apparatus that combines an ultrasonic imaging apparatus that obtains an image of a sample by transmitting and receiving ultrasonic waves.

[Prior Art] Conventionally, a photoacoustic imaging apparatus has been used as a material evaluation unit for detecting a defect in a solid material (for example, ceramics). That is, the test object is irradiated with intermittent light, and analysis and evaluation of the test object are performed based on a photoacoustic signal generated by the test object according to the frequency of the intermittent light.
Furthermore, the test object is placed on the XY stage and moved so that the irradiation light scans the test object surface uniformly, and a certain range of image display is performed based on the strength of the photoacoustic signal, that is, the magnitude of the amplitude. Specimen analysis is being performed.

On the other hand, an ultrasonic imaging apparatus is used as an apparatus for diagnosing tissue of a living body and inspecting surface properties and acoustic properties of metals, ceramics and the like. In particular, ultra-high-frequency ultrasonic imaging devices
Usually called an ultrasonic microscope, it is used for performing fine image diagnosis of a subject by transmitting and receiving ultrasonic waves having a high resolution.

Conventional examples of the photoacoustic imaging apparatus and the ultrasonic imaging apparatus will be described with reference to FIGS. 2 and 3. FIG.

FIG. 2 is a diagram showing a schematic configuration of a conventional general photoacoustic imaging apparatus, in which a light source 12 of a light irradiation unit 10 includes a condenser lens 14.
It is arranged to face the spectroscope 16 with the. In this example, a xenon lamp is used as the light source 12, and the spectroscope 16 selects and emits light of a predetermined wavelength from a xenon lamp that is a continuous spectrum light source. A variable wavelength driving device 18 is connected to the spectroscope 16 so that the emission wavelength of the spectroscope 16 can be arbitrarily adjusted.

Further, an optical chopper 20 and a condenser lens 22 are arranged on a light beam emitted from the spectroscope 16. Light chopper 20
Is for making light of a predetermined wavelength from the spectroscope 16 into intermittent light of a predetermined frequency. This optical chopper 20 is, for example, 10 Hz
A modulation frequency of about 10 KHz can be obtained. The sample cell 24 is located at the position where the intermittent light passing through the condenser lens 22 is irradiated.
Are arranged, and a sample 26 is placed in the sample cell 24 with a condenser lens 22.
It is placed on a table 28 that can move in the X and Y directions with respect to light from. In the sample cell 24, a microphone 30 for detecting an acoustic signal emitted from the sample 26 is arranged. A lock-in amplifier 34 is connected to the microphone 30 via a preamplifier 32, and the lock-in amplifier 34
, A computer 36 is further connected. The selected wavelength signal from the variable wavelength driving device 18 is also input to the computer 36. An image display device 38 is connected to the computer 36.

The signal detected by the microphone 30 is transmitted to the preamplifier 32
The lock-in amplifier 34 performs phase lock based on the frequency signal from the optical chopper 20 to remove noise, and sends an output signal to the computer 36. The computer 36 performs image processing based on this signal, supplies a processing signal to the image display device 38, and the image is displayed on the image display device 38 as an image.

According to this photoacoustic imaging apparatus, light of a predetermined wavelength emitted from the spectroscope 16 is irradiated on the sample 26 as intermittent light of a predetermined frequency by the optical chopper 20, so that the frequency set by the optical chopper 20 Is generated. Accordingly, the photoacoustic signal and sound can be detected by the microphone 30.

Then, by moving the sample 26 by the operation of the table 28 and scanning the irradiation light, an image based on the photoacoustic signal of the scanned area of the sample 26 can be obtained. The image based on this photoacoustic signal is an image affected by the thermal properties of the sample material, that is, the part emitted as heat of the irradiated light is captured as a photoacoustic signal, and is obtained by the strength of this signal. Image to be displayed on the image display device 38, for example,
It can be displayed on the CRT.

Further, the wavelength variable driving device 18 can arbitrarily change the setting of the wavelength by the spectroscope 16 and detect the intensity of the photoacoustic signal due to light irradiation for each predetermined wavelength. Therefore,
By previously detecting the characteristics of various substances with respect to the wavelength of light, it becomes possible to analyze various substances in the sample by irradiating intermittent light with changed wavelengths.

For detection of a photoacoustic signal emitted from the sample 26, a device that attaches a piezoelectric element (such as a ZnO piezoelectric element) to the sample 26 and converts the photoacoustic signal into an electric signal is used in addition to the microphone.

FIG. 3 is a diagram showing a general overall configuration of an ultrasonic microscope as an ultrasonic imaging apparatus, and includes a high-frequency pulse generator 40;
Is connected to a pulse control circuit 42.
The high frequency pulse generator 40 controls the high frequency pulse generator 40 to generate an ultrahigh frequency burst wave electric signal. This signal is supplied via a circulator 44 to a piezoelectric transducer 48 attached to the upper end of an acoustic lens 46 made of sapphire or the like. The piezoelectric transducer 48
The supplied signal is converted into an ultrasonic wave, and the ultrasonic wave is collected on a sample 52 placed on a sample stage 50 through an acoustic lens 46 to collect sound as shown by a broken line 54 in the drawing to form a spot. Project. The space between the tip of the acoustic lens 46 and the sample 52 is filled with water 53 as a couplant in order to prevent the propagation loss of ultrasonic waves from increasing.

The reflected wave from the sample 52 is collected by the acoustic lens 46, converted into an electric signal by the piezoelectric transducer 48, and supplied to the gate circuit 56 via the circulator 44.
The gate circuit 56 extracts only the reflection signal from the sample 52 based on the output of the pulse control circuit 42. Gate circuit
The output of 56 is sent to an amplification / detection circuit 58, amplified and detected, and supplied to a scan converter 60.

The sample stage 50 is moved in the X-axis and Y-axis directions by the scanning control device 64 based on a control signal from the control circuit 62, whereby the sample 52 and the acoustic lens 46 are relatively moved in the X-axis and Y-axis directions. Be moved. Then, the scanning control device 64 includes:
A position signal indicating the relative position between the sample 52 and the acoustic lens 46 is supplied to the scan converter 60. Scan converter 60
Supplies the detection signal from the amplification / detection circuit 58 as a luminance signal to the monitor 66 as an image display unit based on the position signal, and displays an image based on the strength of the reflected ultrasonic wave.

According to such an ultrasonic microscope, a fine ultrasonic image diagnosis is performed by transmitting and receiving an ultrasonic wave of an ultra-high frequency having an extremely high resolution, and is also used for a tissue diagnosis of a living body.

[Problems to be Solved by the Invention] The above-described conventional photoacoustic imaging apparatus and ultrasonic imaging apparatus are each used independently, and particularly, analysis using images for diagnosis of a living body is performed only by an ultrasonic microscope. .

However, tissue diagnosis of a living body using an ultrasonic microscope has not achieved sufficient results, and there is a demand to improve the diagnostic accuracy in microscopic image diagnosis of a living body.
There is a problem in that highly reliable and highly accurate tissue diagnosis of a living body can be achieved by one device using one device.

Object of the Invention The present invention has been made to solve the above problems, the purpose of which is to combine a photoacoustic imaging device and an ultrasonic imaging device, a photoacoustic signal and tissue analysis of biological tissues and plant tissues. It is an object of the present invention to provide a photoacoustic imaging apparatus capable of performing highly accurate diagnosis by using two kinds of imaging techniques using ultrasonic waves.

[Means for Solving the Problems] In order to achieve the above object, a photoacoustic imaging apparatus according to the present invention includes a sample stage having a transparent plate on which a sample to be image-diagnosed is placed, and an ultrasonic imaging mode. An ultrasonic transducer that transmits an ultrasonic wave to the sample, receives a reflected wave thereof, and receives a photoacoustic wave from the sample in a photoacoustic image mode, and a predetermined frequency having a predetermined wavelength in the photoacoustic image mode A light irradiator having a light emitting means for emitting the intermittent light to the sample, and creating an ultrasonic image based on the reflected wave received by the ultrasonic transducer in the ultrasonic image mode, and in the photoacoustic image mode, A shared image creating unit that creates a photoacoustic image based on a photoacoustic wave received by an ultrasonic transducer, and an image that displays the ultrasonic image and the photoacoustic image And a light emitting unit of the light irradiation unit and the ultrasonic transducer are arranged to face each other with a transparent plate of the sample stage interposed therebetween.

[Operation] According to the photoacoustic imaging apparatus having the above-described configuration, the ultrasonic transducer and the light emitting unit of the light irradiation unit are opposed to each other with the transparent plate on which the sample is placed interposed therebetween. Ultrasound transmission and reception and light irradiation can be performed from the front and back surfaces of the sample.

Then, a photoacoustic signal emitted from the sample by light irradiation can be received by the transducer, and an image is displayed based on the reflected wave or photoacoustic signal (photoacoustic wave) of the ultrasonic wave received by the ultrasonic transducer. Since the signal processing is performed by the common signal processing unit, it is possible to avoid an increase in the size of the entire apparatus.

Then, the analysis and inspection of the sample can be performed on one sample by the image based on the photoacoustic signal affected by the thermal property based on the light irradiation and the image based on the transmission and reception of the ultrasonic wave.

Therefore, by using it for tissue diagnosis of a living body, two types of tissue analysis images having different properties can be obtained, and more accurate diagnosis can be performed by comparing and analyzing the images.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the figure, the same elements as those shown in FIGS. 2 and 3 are denoted by the same reference numerals, and description thereof will be omitted.

A characteristic feature of the present invention is that a sample table having a transparent plate for mounting a sample, an ultrasonic transducer and a light emitting unit are arranged to face each other with the sample table interposed therebetween, and further, a common signal processing unit for image display is used. Has been made.

In the present embodiment, the sample stage 50 is configured by providing a transparent plate 50a formed of a glass plate or the like at the center and surrounding the outer periphery with a frame 50b.

An acoustic lens 46 provided with piezoelectric transducers 48 on both sides of the transparent plate 50a and an optical fiber 68, which is a light emitting means of a light irradiation unit, are arranged to face each other. The arrangement position of the optical fiber 68 and the acoustic lens 46 is such that a photoacoustic signal emitted from a living tissue 70 as a sample by light irradiation from the optical fiber is received by the acoustic lens 46 and efficiently sent to the piezoelectric transducer 48. It is preferable that the position is set at a position vertically opposed to the transparent plate 50a.

In the present embodiment, the light irradiating unit 10 includes a laser light source 72, a light chopper 20 for chopping laser light from the laser light source 72 into intermittent light at a predetermined frequency, a condenser lens 22, and a light from the condenser lens 22 that is transparent. It is constituted by an optical fiber 68 that irradiates the living tissue 70 placed on the plate 50a from the lower surface side. Thus, in this embodiment,
By using a laser light source 72 as the light source, a spectroscope for setting the light shown in the conventional example of FIG.
16 and the variable wavelength driving device 18 are not required. However, when performing image diagnosis by light irradiation of a plurality of wavelengths, it is of course possible to perform light irradiation with a light source such as a xenon lamp as in the conventional example.

Next, the signal processing unit 74 for performing image display based on a photoacoustic signal from the living tissue 70 emitted by light irradiation and image display by transmission and reception of ultrasonic waves by the monitor 66,
A circuit similar to the signal processing circuit of the ultrasonic microscope shown in FIG. 3 is used. The signal processing operation is similar.

Therefore, the converted electric signal from the piezoelectric transducer 48 that has received the reflected ultrasonic wave is displayed on the monitor 66 after the signal processing similar to the processing in FIG.
The operation as the photoacoustic image device is performed by the optical fiber 68
When the intermittent light of a predetermined frequency set by the optical chopper 20 is applied to the living tissue 70 as a sample, a photoacoustic signal similar to the frequency of the applied intermittent light is issued. This photoacoustic signal is transmitted to the piezoelectric transducer via the acoustic lens 46 in the same manner as the operation of receiving the reflected ultrasonic wave.
Received at 48. Then, an image based on the photoacoustic signal can be displayed on the monitor 66 by the same processing as the signal processing of the reflected wave of the ultrasonic wave.

As a result, both a gray-scale image obtained based on the intensity of the reflected wave of the ultrasonic wave and an image based on the photoacoustic signal influenced by the characteristics of heat emitted by the irradiated light having completely different properties from the image. The tissue image of the living body can be diagnosed by the above image.

Further, the same living tissue 70 placed on the transparent plate 50a can be subjected to a diagnostic test under the same setting conditions without changing the setting state, and by comparing two types of images for a common living tissue. Complementary diagnostic imaging can be performed.

[Effects of the Invention] As described above, according to the photoacoustic imaging apparatus according to the present invention, a sample can be obtained by two types of images: an image based on a photoacoustic signal emitted from the sample and an image based on transmission and reception of ultrasonic waves to and from the sample. Analysis and inspection can be performed.

Further, by sharing the signal processing unit of both image devices, two types of video images can be displayed without increasing the size of the devices.

With these two types of images, diagnosis based on the individual images and complementary diagnosis based on comparison between the two images can be performed, and the accuracy of minute image diagnosis of the sample can be improved.

[Brief description of the drawings]

 FIG. 1 is a schematic configuration diagram showing an overall configuration of an embodiment of the present invention, FIG. 2 is a schematic overall configuration diagram of a conventional photoacoustic imaging apparatus, and FIG. 3 is a schematic overall configuration diagram of a conventional ultrasonic microscope. . 10: Light irradiation unit 48: Piezoelectric transducer 50: Sample table 50a: Transparent plate 70: Living tissue 74: Signal processing unit

Claims (1)

(57) [Claims] 1. A sample stage having a transparent plate on which a sample to be image-diagnosed is placed, and an ultrasonic wave is transmitted to the sample in an ultrasonic image mode, and a reflected wave is received. An ultrasonic transducer for receiving a photoacoustic wave from the sample, a light irradiation unit having a light emitting unit for emitting intermittent light having a predetermined wavelength and a predetermined frequency in the photoacoustic image mode to the sample, and an ultrasonic image mode. A shared image that creates an ultrasound image based on the reflected wave received by the ultrasound transducer and creates a photoacoustic image based on the photoacoustic wave received by the ultrasound transducer in a photoacoustic image mode in A light emitting unit of the light irradiating unit and the ultrasonic transducer, comprising: a creating unit; and an image display unit that displays the ultrasonic image and the photoacoustic image. Sa is the photoacoustic imaging apparatus, characterized in that disposed facing each other across the transparent plate of the sample stage.