Total body irradiation with 6MVX-rays. Absorbed dose distribution in a humanoid phantom

Dose distribution in a humanoid phantom irradiated with total body irradiation of long SAD techniques by 6MV x-rays are discussed. Absorbed dose are measured by x-ray films or TLDs set in slice of the phntom. Uniformity of dose distribution is compared among the results of irradiations by anterior-posterior opposing two beams, lateral opposing two beams, and these combination (four beams). In the cases of lateral opposing two beams irradiation, irradiation is done with and without water boluses at head and neck region. In the case of four beams (anterior-posterior and bilateral), the uniformity is best among the three irradiation techniques, and the uniformity is within ±10%. In the case of anterior posterior opposing two beams irradiation, the uniformity is rather good, but exceeds ±10%. Lateral opposing two beam irradiation results the worst uniformity. But an application of boluses shows improvent of uniformity of midline of a humanoid phantom. In thoracicregion, as lung is irradiated over high absorbed dose, lung compensator is sufficiently nesessary for dose homogeneous and dose reduction. (author)