Photoacoustic imaging apparatus and photoacoustic imaging method

Abstract

A photoacoustic imaging apparatus includes holding members configured to hold a subject, an acoustic wave conversion unit configured to receive an acoustic wave generated by irradiating the subject, which is held by the holding members, with light from a light source and convert the acoustic wave into an electric signal, a processing unit configured to generate image data from the electric signal, and an imaging unit configured to capture an optical pattern generated on a light diffusion member by emitting the light to the light diffusion member arranged on a surface of a side where the subject is irradiated with the light in the holding members where the holding members contact the subject in holding the subject, wherein the processing unit calculates light absorption coefficient distribution in the subject based on the optical pattern captured by the imaging unit and the electric signal acquired by the acoustic wave conversion unit.

1 . A photoacoustic imaging apparatus comprising:
 a light source configured to emit first light and second light at different timings from each other;   a light amount measurement unit configured to measure a light amount of a part of the first light emitted from the light source;   an acoustic wave conversion unit configured to receive an acoustic wave generated by irradiating a subject with the first light and convert the acoustic wave into an electric signal;   a processing unit configured to generate image data based on the electric signal; and   an imaging unit configured to capture an optical pattern of the second light,   wherein the processing unit is configured to:   calculate a light amount distribution of the first light in the subject based on the light amount of the part of the first light and the optical pattern of the second light, and   generate image data based on the light amount distribution of the first light in the subject and the electric signal.   
     
     
         2 . The photoacoustic imaging apparatus according to  claim 1 , wherein the processing unit is configured to:
 calculate light irradiation density distribution of the first light based on the light amount of the part of the first light and the optical pattern of the second light, and   calculate the light amount distribution of the first light in the subject based on the light irradiation density distribution of the first light.   
     
     
         3 . The photoacoustic imaging apparatus according to  claim 2 , wherein the processing unit is configured to:
 calculate relative light irradiation density distribution of the second light based on the optical pattern of the second light,   calculate the light irradiation density distribution of the first light based on the relative light irradiation density distribution of the second light and the light amount of the part of the first light.   
     
     
         4 . The photoacoustic imaging apparatus according to  claim 3 ,
 wherein the processing unit is configured to calculate a light amount of the first light based on the light amount of the part of the first light, and   wherein the processing unit is configured to calculate the light irradiation density distribution of the first light based on the relative light irradiation density distribution of the second light and the light amount of the first light.   
     
     
         5 . The photoacoustic imaging apparatus according to  claim 1 , wherein the processing unit is configured to generate the image data of a light absorption coefficient distribution in the subject. 
     
     
         6 . The photoacoustic imaging apparatus according to  claim 2 , wherein the processing unit is configured to control the light source so that a maximum value of the light irradiation density distribution of the first light is less than or equal to a maximum permissible exposure amount for the subject. 
     
     
         7 . The photoacoustic imaging apparatus according to  claim 1 , wherein the light source is a laser generator. 
     
     
         8 . The photoacoustic imaging apparatus according to  claim 1 , further comprising a holding member configured to hold the subject by contacting the subject. 
     
     
         9 . The photoacoustic imaging apparatus according to  claim 1 , further comprising:
 an optical system configured to lead light from the light source to the subject.   
     
     
         10 . The photoacoustic imaging apparatus according to  claim 1 ,
 wherein the light amount measurement unit includes an optical sensor, a thermal sensor, and a pyroelectric sensor.   
     
     
         11 . The photoacoustic imaging apparatus according to  claim 1 ,
 wherein the imaging unit includes plural elements configured to detect light.   
     
     
         12 . A photoacoustic imaging method comprising:
 emitting first light;   measuring a light amount of a part of the first light;   converting an acoustic wave generated by the irradiating the subject with the first light into an electric signal;   emitting second light at a different timing from the first light,   capturing an optical pattern of second light;   calculating light amount distribution of the first light in the subject based on the light amount of the part of the first light and the optical pattern of the second light, and   generating image data based on the light amount distribution of the first light in the subject and the electric signal.   
     
     
         13 . The photoacoustic imaging method according to  claim 12 , wherein the calculating light amount distribution of the first light in the subject includes:
 calculating light irradiation density distribution of the first light based on the light amount of the part of the first light and the optical pattern of the second light, and   calculating the light amount distribution of the first light in the subject based on the light irradiation density distribution of the first light.   
     
     
         14 . The photoacoustic imaging method according to  claim 13 , wherein the calculating light amount distribution of the first light in the subject includes:
 calculating relative light irradiation density distribution of the second light based on the optical pattern of the second light, and   calculating the light irradiation density distribution of the first light based on the relative light irradiation density distribution of the second light and the light amount of the part of the first light.   
     
     
         15 . The photoacoustic imaging method according to  claim 14 , wherein the calculating light amount distribution of the first light in the subject includes:
 calculating a light amount of the first light based on the light amount of the part of the first light, and   calculating the light irradiation density distribution of the first light based on the relative light irradiation density distribution of the second light and the light amount of the first light.   
     
     
         16 . The photoacoustic imaging method according to  claim 12 , wherein the image data of a light absorption coefficient distribution in the subject is generated. 
     
     
         17 . The photoacoustic imaging method according to  claim 13 , further comprising determining whether a maximum value of the light irradiation density distribution of the first light is less than or equal to a maximum permissible exposure amount for the subject. 
     
     
         18 . The photoacoustic imaging method according to  claim 17 , further comprising controlling a light source that emits the first light so that the maximum value of the light irradiation density distribution of the first light becomes less than or equal to the maximum permissible exposure amount if the maximum value of the light irradiation density distribution of the first light is not less than the maximum permissible exposure amount for the subject. 
     
     
         19 . The photoacoustic imaging method according to  claim 13 , further comprising controlling a light source that emits the first light so that a maximum value of the light irradiation density distribution of the first light is less than or equal to a maximum permissible exposure amount for the subject.