Field of the Invention
The present invention relates to an object information acquiring apparatus and a control method therefor.
Description of the Related Art
Researches for an optical imaging apparatus that irradiates light on an object such as a living organism from a light source such as a laser and converts information concerning the inside of the object obtained on the basis of the incident light into an image have been actively in progress in the medical field. As a kind of this optical imaging technique, there is photoacoustic imaging (PAI).
In the photoacoustic imaging, first, pulsed light from a light source is irradiated on an object. Then, an object tissue (a light absorber), which absorbs energy of the pulsed light propagated and diffused in the object, instantaneously expands and generates an acoustic wave. At this point, since an absorption ratio of the light energy is different depending on the type of the tissue and the wavelength of the light, there is a difference in a generated sound pressure between a test segment such as a tumor and the other tissues. Therefore, an information processing apparatus subjects an electric signal generated by receiving the acoustic wave in a probe to mathematic analysis processing, whereby it is possible to image object information. As the object information, an optical characteristic distribution in the object, in particular, an initial sound pressure distribution, an optical energy absorption density distribution, an absorption coefficient distribution, and the like are obtained. Further, it is possible to perform quantitative measurement of a specific substance concentration in the object, for example, oxygen saturation in blood on the basis of these kinds of information and information concerning the wavelength of irradiated light.
In recent years, a preclinical research for imaging a blood vessel image of a small animal using the photoacoustic imaging technique, and a clinical research for applying this principle to diagnosis of breast cancer and the like have been actively in progress (“Photoacoustic imaging in biomedicine”, M. Xu, L. V. Wang, REVIEW OF SCIENTIFIC INSTRUMENT, 77, 041101, 2006). In the photoacoustic imaging, usually, an optical characteristic distribution of a light absorber present inside the object is converted into an image.
Non Patent Literature 1: “Photoacoustic imaging in biomedicine”, M. Xu, L. V. Wang, REVIEW OF SCIENTIFIC INSTRUMENT, 77, 041101, 2006