Dose distributions produced by shielded applicators using 241Am for intracavitary irradiation of tumors in the vagina.
Dosimetric characteristics of shielded vaginal applicators containing encapsulated 241Am sources are investigated in this work. Encapsulated 241Am sources emit primarily 60-keV photons which are more effectively shielded by thin layers of high atomic number materials than the 662-keV photons from 137Cs sources. With 241Am, it is possible to achieve almost unidirectional irradiation of localized vaginal tumors. The drastic decrease in irradiation volume on the contralateral side (uninvolved with tumor) is observed to decrease dose by up to 20%, even in the forward direction (unshielded side toward the tumor) of the applicator. A possible explanation for the observed effects of shields in both the forward and backward directions is the reduction of scattered photon fluence due to absorption of photons in the lead shield via photoelectric effect. Current theoretical models do not include this perturbation effect caused by shields on brachytherapy applicators.
Muench
P J
PJ
Yale University School of Medicine, Department of Therapeutic Radiology, New Haven, Connecticut 06510.
Nath
R
R
D000576:Americium / Q000627:therapeutic use*; D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods; D005260:Female; D006801:Humans; D011835:Radiation Protection / Q000295:instrumentation; D011879:Radiotherapy Dosage; D013819:Thermoluminescent Dosimetry; D014625:Vaginal Neoplasms / Q000532:radiotherapy*
D000576:Americium