Neutron and gamma doses from medical in vivo prompt gamma-ray activation using a mobile nuclear reactor

Medical diagnosis of toxic contaminants in body organs using in vivo neutron capture prompt gamma-ray activation technique has been investigated by several research groups. By using a high-resolution germanium detector coupled with fast electronics, characteristic prompt gamma rays emitted from neutron capture reactions with toxic cadmium, mercury, and silicon inside the human body are recorded in partial-body in vivo prompt gamma-ray activation analysis (PBIVPGAA) diagnosis. Although the radiation doses to the skin were reported in each and every previous PBIVPGAA work, organs and tissues sensitive to radiation, such as gonads, red bone marrow, bone surface, thyroid, breast, and lung are either the irradiated organ itself or are not far from the neutron beam. Both neutrons and gamma rays can scatter into the sensitive organ or tissue and interact with nuclei to cause radiation damage. The radiation safety and protection in PBIVPGAA diagnosis should focus on the radiation dose to sensitive organs and tissues, not to the skin. In this work the neutron facility identical to that used in previous works, the 0.1-W Tsing-Hua Mobile Educational Reactor (THMER) is used for PBIVPGAA diagnosis. A Lucite phantom was irradiated to simulate the investigation of toxic mercury and cadmium in kidneys and liver. The radiation risks of hereditary and somatic effects to irradiated patients were evaluated. Features of radiation doses and associated risks re discussed in this paper and compared to other medical diagnostic methods using nuclear techniques