Development of a simple and rapid method of precisely identifying the position of 10B atoms in tissue: an improvement in standard alpha autoradiography

Boron neutron capture therapy (BNCT) can be utilized to selectively kill cancer cells using a boron compound that accumulates only in cancer cells and not in normal cells. Tumor-bearing animals treated by BNCT are routinely used to evaluate long-term antitumor effects of new boron compounds. Alpha-autoradiography is one of the methods employed in the evaluation of antitumor effects. However, a standard alpha-autoradiography cannot detect the microdistribution of (10)B because of the difficulty associated with the superposition of a tissue sample image and etched pits on a track detector with the etching process. In order to observe the microdistribution of (10)B, some special methods of alpha-autoradiography have been developed that make use of a special track detector, or the atomic force microscope combined with X-ray and UV light irradiation. In contrast, we propose, herein, a simple and rapid method of precisely identifying the position of (10)B using the imaging process and the shape of etched pits, such as their circularity, without the need to use special track detectors or a microscope. A brief description of this method and its verification test are presented in this article. We have established a method of detecting the microdistribution of (10)B with submicron deviation between the position of etched pits and the position of reaction in a tissue sample, for a given circularity of etched pits.