Photoacoustic image generation apparatus and acoustic wave unit

Patent metadata

Field	Value
Publication number	US-9486144-B2
Application number	US-201414167808-A
Country	US
Kind code	B2
Filing date	Jan 29, 2014
Priority date	Jul 29, 2011
Publication date	Nov 8, 2016
Grant date	Nov 8, 2016

Abstract

Using a laser source unit, pulse laser beams having a plurality of wavelengths is switched and emitted. A Q switch is inserted into an optical resonator including a pair of mirrors which face each other with a laser rod interposed therebetween. A wavelength selection unit includes a plurality of band pass filters having different transmission wavelengths, and selectively inserts the plurality of band pass filters into a light path of the optical resonator. A trigger control circuit controls driving unit that drives the wavelength selection unit so that the band pass filters inserted into the light path of the optical resonator are switched at a predetermined switching speed. In addition, the trigger control circuit causes the laser rod to be irradiated with excitation light from a flash lamp, and then turns on the Q switch at a timing when the wavelength selection unit inserts the band pass filter.

First claim

What is claimed is:

1. A photoacoustic image generation apparatus comprising:
a laser source unit capable of emitting a plurality of pulse laser beams having different wavelengths respectively, the laser source unit including a laser rod, an excitation light source that irradiates the laser rod with excitation light, an optical resonator having a pair of mirrors facing each other with the laser rod interposed therebetween, a Q switch which is inserted into the optical resonator, a wavelength selection unit that includes a plurality of band pass filters having different transmission wavelengths and selectively inserts the plurality of band pass filters into a light path of the optical resonator, and a servo motor that drives the wavelength selection unit so that the band pass filters inserted into the light path of the optical resonator are sequentially switched in a predetermined order; and
an acoustic wave unit that generates a photoacoustic image, the acoustic wave unit including a detection unit that detects a photoacoustic signal generated within an object when the object is irradiated with the pulse laser beams having the plurality of wavelengths, and generates pieces of photoacoustic data corresponding to the respective wavelengths, an intensity ratio extraction unit that extracts a magnitude relation between relative signal intensities of the pieces of photoacoustic data corresponding to the respective wavelengths, a photoacoustic image construction unit that generates a photoacoustic image on the basis of the extracted magnitude relation, and a trigger control circuit that causes the laser rod to be irradiated with excitation light from the excitation light source while controlling the servo motor, and after the irradiation with the excitation light, turns on the Q switch at a timing when the wavelength selection unit inserts the band pass filter, having a transmission wavelength corresponding to a wavelength of the pulse laser beam to be emitted, into the light path to emit the pulse laser beam, wherein
the wavelength selection unit is constituted by a filter rotating body that switches the band pass filter selectively inserted into the light path of the optical resonator in association with rotation, and the servo motor rotationally drives the filter rotating body,
the trigger control circuit sends a signal for controlling the servo motor so that the filter rotating body is continuously rotated in a predetermined direction at a predetermined rotation speed,
the predetermined rotation speed is determined by the trigger control circuit on the basis of the number of wavelengths of the pulse laser beam to be emitted and the number of times of emission of the pulse laser beam per unit time,
the trigger control circuit determines a timing at which irradiation with the excitation light is performed and a timing at which the Q switch is turned on based on filter rotational angle, wherein the filter rotational angle indicates a rotational angle of the filter rotating body obtained by the trigger control circuit and the filter rotational angle is varied in accordance with the rotation of the filter rotating body rotated at the predetermined rotation speed,
when the filter rotational angle corresponds to a value representing a position, the trigger control circuit sends a signal to cause the laser rod to be irradiated with excitation light, and
the value representing the position is obtained by the trigger control circuit by subtracting a value that corresponds to the amount of rotational displacement of the filter rotating body during a period of time required for the excitation of the laser rod from a value that corresponds to a position of the filter rotating body at which the band pass filter corresponding to a wavelength of the pulse laser beam to be emitted is inserted into the light path.

2. The photoacoustic image generation apparatus according to claim 1 , wherein the laser source unit further includes a rotation control unit that sends a signal for controlling the servo motor so that the amount of rotational displacement of the filter rotating body during a predetermined period of time is set to an amount depending on the predetermined rotation speed, and the trigger control circuit controls the servo motor through the rotation control unit.

3. The photoacoustic image generation apparatus according to claim 1 ,
wherein the acoustic wave unit further includes an intensity information extraction unit that generates intensity information indicating signal intensity on the basis of the pieces of photoacoustic data corresponding to the respective wavelengths, and
wherein the photoacoustic image construction unit determines a gradation value of each pixel of the photoacoustic image on the basis of the intensity information, and determines a display color of each pixel on the basis of the extracted magnitude relation.

4. The photoacoustic image generation apparatus according to claim 3 ,
wherein the plurality of wavelengths of the pulse laser beams to be emitted by the laser source unit includes a first wavelength and a second wavelength,
wherein the acoustic wave unit further includes a complex number creation unit that generates complex number data in which one of first photoacoustic data corresponding to a photoacoustic signal, detected when irradiation with the pulse laser beam having the first wavelength is performed, and second photoacoustic data corresponding to a photoacoustic signal, detected when irradiation with the pulse laser beam having the second wavelength is performed, is set to a real part and the other one is set to an imaginary part, and a photoacoustic image reconstruction unit that generates a reconstructed image from the complex number data using a Fourier transform method, and
wherein the intensity ratio extraction unit extracts phase information as the magnitude relation from the reconstructed image, and the intensity information extraction unit extracts the intensity information from the reconstructed image.

5. The photoacoustic image generation apparatus according to claim 1 ,
wherein the detection unit further detects reflected acoustic waves with respect to acoustic waves transmitted to the object to generate reflected acoustic wave data, and
wherein the acoustic wave unit further includes an acoustic wave image generation unit that generates an acoustic wave image on the basis of the reflected acoustic wave data.

Assignees

• Fujifilm Corp

Inventors

• Hirota Kazuhiro
• Kasamatsu Tadashi

Classifications

• A61B8/13

  Tomography (A61B8/10, A61B8/12 take precedence) · CPC title

• A61B5/14542

  for measuring blood gases (A61B5/14551 takes precedence) · CPC title

• H01S3/08027

  by a filter, e.g. a Fabry-Perot filter is used for wavelength setting · CPC title

• A61B8/54

  Control of the diagnostic device · CPC title

• A61B8/0891

  for diagnosis of blood vessels · CPC title