Development and clinical translation of photoacoustic mammography.

To practically apply photoacoustic (PA) imaging technology in medicine, we have developed prototypes of a photoacoustic mammography (PAM) device to acquire images for diagnosing breast cancer in the Kyoto University/Canon joint research project (CK project supported by MEXT, Japan). First, the basic ability of the PAM system to visualize the network of blood vessels and the Hb saturation index was evaluated using a prototype of PAM that has a flat scanning detector and is capable of simultaneously acquiring photoacoustic (PA) and ultrasound images. Next, another prototype of a PAM device with hemispherical sensors was developed to improve the visibility of the 3D structure of vessels by reducing the limited view effect. In clinical examination of breast cancer cases, the PAM system allowed 3D visualization of fine vessel networks with a spatial resolution of a half-millimeter and enabled us to determine the features of tumor-related vascular structures in human breast cancer. In addition, the oxygen saturation status of Hb was visualized using two different wavelengths, enabling more precise characterization of the tumor microenvironment. Results of clinical evaluation using our developed prototype of a PAM device confirmed that PA imaging technology has the potential to promote early detection of breast cancer, and realization of its practical use is expected in the near future.