Shielding for radiation scattered dose distribution to the outside fields in patients treated with high energy radiotherapy beams

Scattered dose of therapeutic high energy radiation beams contributed significant unwanted dose to the patient. Measurement of radiation scattered dose outside fields and critical organs, like fetus position and testicle region, from chest or pelvic irradiation by large field of high energy radiation beam, was performed using an ionization chamber and film dosimetry. The scattered doses outside field were measured 5-10% of maximum doses in fields and exponentially decrease from field margins. The scattered photon dose received the uterus from thorax field irradiation and was measured about 1mGy/Gy of photon treatment dose. Shielding construction to reduce this scattered dose was investigated using lead sheet and blocks About 6 cm lead block shield reduced the scatter photon dose under 10mGy for 60Gy on abdomen field and almost reduced electron contamination. (author)