Dosimetry Based on Dose Maps Inside the Human Body for External Photon Exposure

Dose distribution inside the human body due to external photon exposure was measured. Radiation detectors were imaging plate (IP) sheets and thermoluminescent dosimeters (TLD). Each IP sheet was installed between horizontally sliced pieces of a rando-phantom. TLDs were also installed inside/around the position of a target organ of the phantom. The rando-phantom was exposed to a photon beam of Cs (0.66MeV) at a distance of 2.0 meters, for example. The direction of the photons that hit the surface of the phantom body could affect the dose distribution inside the human body. In order to check the level of this effect, incident angles of the photon beam in this experiment were changed with 45-degree intervals around the longitudinal axis of the rando-phantom at the same height as the center of a target organ. This study presents continuous visual and numerical dose maps of the inside of the human body. In order to estimate an equivalent dose as an averaged absorbed dose of a target organ, the dose distribution should be taken into account. A pinpoint dose inside of a larger target organ must also be estimated based on the dose maps. Dosimetry based on bio-samples, such as the ESR method with human tooth enamel, must be corrected by the dose distribution in a head. In this case, the sample position in the body becomes an important key parameter for adequate dosimetry, as do the photon energy and direction. This study presents a simple calculation technique to correct the ESR dosimetry. In addition, the dose maps gained by IP could be effectively adopted into the planning of the medical use of the radiation on check or treatment such as the CT scan and the interventional radiology (IVR). They use photons or ions with low energy at a high dose rate.