title: Monte Carlo aided room scatter corrections in the air-kerma strength standardization of 169Yb and 60Co brachytherapy sources.
abstract: For accurate evaluation of air-kerma strength, S(k), of 169Yb and 60Co brachytherapy sources, the present study reports Monte Carlo (MC) based corrections for (1) room scatter, and (2) departure from constant room scatter for rooms of various sizes. Correction for exponential attenuation of effective primary in air is also reported for the above sources. Values of S(k) per contained mCi, S(k)/A(c) predicted by MC calculations for 169Yb source (model X1267) with and without Ti K x-rays are 1.302 +/- 0.03% (this value is in excellent agreement with the published value reported by Piermattei et al) and 1.260 +/- 0.03% cGy cm2 h(-1) mCi(-1) respectively, and in the case of Cathetron 60Co source the value of S(k)/A(c) is 11.015 +/- 0.01% cGy cm2 h(-1) mCi(-1). It is observed that depending upon the position of the source with respect to the surrounding concrete scattering surfaces and set of d values, the assumption of constant room scatter has resulted in overestimation of S(k) that varied between 0.30% and 1.5% for the 169Yb source and only between 0.10% and 0.20% for the 60Co source.
authors.affiliation: Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 094, India. pteena@yahoo.com
authors.forename: T Palani
authors.initials: TP
authors.lastname: Selvam
authors.forename: K N Govinda
authors.initials: KN
authors.lastname: Rajan
authors.forename: P
authors.initials: P
authors.lastname: Sethulakshmi
authors.forename: B C
authors.initials: BC
authors.lastname: Bhatt
mesh_terms: D000465:Algorithms; D016477:Artifacts; D001417:Background Radiation; D001918:Brachytherapy / Q000295:instrumentation* / Q000379:methods / Q000592:standards*; D002138:Calibration / Q000592:standards; D003037:Cobalt Radioisotopes / Q000032:analysis* / Q000627:therapeutic use; D009010:Monte Carlo Method; D011786:Quality Control; D011829:Radiation Dosage; D011868:Radioisotopes / Q000032:analysis / Q000627:therapeutic use; D011874:Radiometry / Q000379:methods* / Q000592:standards*; D011879:Radiotherapy Dosage / Q000592:standards; D011880:Radiotherapy Planning, Computer-Assisted / Q000592:standards; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity; D015018:Ytterbium / Q000032:analysis* / Q000627:therapeutic use
chemical_list: D003037:Cobalt Radioisotopes; D011868:Radioisotopes; D015018:Ytterbium