Photoacoustic image generation apparatus, signal processing device, and photoacoustic image generation method

A signal processing device, comprising:

• a receiving circuit that receives a detection signal of a photoacoustic wave emitted from an insertion needle at least a part of which is inserted into a subject and which has an optical fiber for guiding light emitted from a laser unit, a light emitting end surface of the optical fiber that emits light guided by the optical fiber, and a light absorption member that generates at least one a photoacoustic wave of a plurality of photoacoustic waves due to absorption of the light emitted from the light emitting end surface of the optical fiber, wherein the light emitted includes a number of a plurality of light emissions, and wherein the at least one photoacoustic wave generated corresponds to at least one light emission of the plurality of light emissions;
• and
• a processor, wherein the processor is configured to:
• generate a photoacoustic image based on a plurality of detection signals of the photoacoustic wave;
• detect a position of a generation source of the at least one photoacoustic wave from the photoacoustic image;
• acquire a first signal value indicating an intensity of the at least one photoacoustic wave emitted from the generation source of the at least one photoacoustic wave;
• acquire a second signal value, which indicates noise in the photoacoustic image, wherein the second signal value is acquired in a region away from the generation source of the at least one photoacoustic wave by a predetermined distance;
• obtain a difference signal value by dividing the first signal value by the second signal value, wherein the difference signal value is representative of a signal to noise (SN) relative magnitude relationship between the first signal value and the second signal value;
• compare the SN relative magnitude relationship to a predetermined target range for the difference signal value, wherein the predetermined target range including a first threshold value and a second threshold value, wherein the first and second threshold values represent a lower limit and an upper limit of the predetermined target range, respectfully, and wherein the second threshold value is larger than the first threshold value;
• control the number of light emissions of the plurality of light emissions and a light emission interval of the laser unit for the generation of the photoacoustic image, such that:
• when the obtained difference signal value is smaller than the first threshold value, make the number of light emissions of the plurality of light emissions larger than a current number of light emissions of the laser unit and make the light emission interval shorter than a current light emission interval of the laser unit, and
• when the obtained difference signal value is larger than the second threshold value, make the number of light emissions of the plurality of light emissions smaller than the current number of light emissions of the laser unit and make the light emission interval longer than the current light emission interval of the laser unit;
• wherein the number of light emissions and the light emission interval of the laser unit are controlled so that the difference signal value falls within the predetermined target range to improve image quality of the generated photoacoustic image;
• and
• generate the photoacoustic image by at least adding a number of the plurality of detection signals of the plurality of photoacoustic waves corresponding to the number of light emissions.

A photoacoustic image generation method, comprising:

• receiving a detection signal of a photoacoustic wave emitted from an insertion needle having an optical fiber for guiding light emitted from a laser unit, a light emitting end surface of the optical fiber that emits light guided by the optical fiber, and a light absorption member that generates a at least one photoacoustic wave of a plurality of photoacoustic waves due to absorption of the light emitted from the light emitting end surface of the optical fiber, wherein the light emitted includes a number of a plurality of light emissions, and wherein the at least one photoacoustic wave generated corresponds to at least one light emission of the plurality of light emissions;
• generating a photoacoustic image based on a plurality of detection signals of the at least one photoacoustic wave;
• detecting a position of a generation source of the at least one photoacoustic wave from the photoacoustic image;
• acquiring a first signal value indicating an intensity of the at least one photoacoustic wave emitted from the generation source of the at least one photoacoustic wave;
• acquiring a second signal value, which indicates noise in the photoacoustic image, wherein the second signal value is acquired in a region away from the generation source of the at least one photoacoustic wave by a predetermined distance;
• obtaining a difference signal value by dividing the first signal value by the second signal value, wherein the difference signal value is representative of a signal to noise (SN) relative magnitude relationship between the first signal value and the second signal value;
• comparing the SN relative magnitude relationship to a predetermined target range for the difference signal value, wherein the predetermined target range including a first threshold value and a second threshold value, wherein the first and second threshold values represent a lower limit and an upper limit of the predetermined target range, respectfully, and wherein the second threshold value is larger than the first threshold value;
• and
• providing a processor, the processor configured to control the number of light emissions of the plurality of light emissions and a light emission interval of the laser unit for the generation of the photoacoustic image, such that:
• when the obtained difference signal value is smaller than the first threshold value, make the number of light emissions of the plurality of light emissions larger than a current number of light emissions of the laser unit and make the light emission interval shorter than a current light emission interval of the laser unit, and
• when the obtained difference signal value is larger than the second threshold value, make the number of light emissions of the plurality of light emissions smaller than the current number of light emissions of the laser unit and make the light emission interval longer than the current light emission interval of the laser unit;
• wherein the number of light emissions and the light emission interval of the laser unit are controlled so that the difference signal value falls within the predetermined target range to improve image quality of the generated photoacoustic image;
• and
• wherein, in generating the photoacoustic image, the photoacoustic image is generated by at least adding a number of the plurality of detection signals of the plurality of photoacoustic waves corresponding to the number of light emissions.