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Dose distributions around cylindrical 2 4 1 Am sources for a clinical intracavitary applicator
Author(s) -
Nath Ravinder,
Gray Laurence,
Park Chang H.
Publication year - 1987
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.596007
Subject(s) - dosimetry , ionization chamber , percentage depth dose curve , thermoluminescent dosimetry , dose profile , scattering , nuclear medicine , absorbed dose , materials science , ionization , thermoluminescence , lithium fluoride , thermoluminescent dosimeter , optics , physics , dosimeter , nuclear physics , ion , medicine , luminescence , quantum mechanics
Encapsulated, cylindrical sources containing 2, 5, and 8 Ci of 2 4 1 Am have been designed and fabricated for intracavitary irradiation of uterine cancers. Exposure rates in air and dose rates in water around these sources have been measured using an ionization chamber and a lithium fluoride thermoluminescent dosimetry system. Dose rates in water at a distance of 2.5 cm from the source center along a direction transverse to the source axis were found to be 10.4, 24.3, and 23.3 cGy/h for the 2‐, 5‐, and 8‐Ci sources, respectively, using an ionization chamber. Under the same conditions, the thermoluminescent dosimetry system yielded the values of 10.3, 23.1, and 22.3 cGy/h. It was observed that the ratio of dose‐to‐water and exposure in air is sensitive to the scattering geometry and source geometry in the case of 2 4 1 Am photons. This ratio was found to increase substantially as conditions of full scattering were approached. A three‐dimensional integration model was employed for the determination of dose distributions around these sources. Results of this dose computation model have been compared against the measured data and were found to be in good agreement with each other. Average deviations of calculated data from measured data were in the range of 0.2 to 0.5 cGy/h and larger deviations were observed in the paraxial region, where the effects of oblique filtration are more severe. Computed dose rate tables were employed as reference source data in a modified version of a commercial treatment planning system in order to develop a facility for clinical dosimetry of 2 4 1 Am intracavitary applications.