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Dosimetry comparison of 192 Ir Sources
Author(s) -
Papagiannis P.,
Angelopoulos A.,
Pantelis E.,
Sakelliou L.,
Baltas D.,
Karaiskos P.,
Sandilos P.,
Vlachos L.
Publication year - 2002
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 - 10.1118/1.1508378
Subject(s) - dosimetry , point source , monte carlo method , physics , brachytherapy , computational physics , transverse plane , anisotropy , dose rate , cartesian coordinate system , line source , geometry , nuclear medicine , optics , mathematics , medical physics , statistics , medicine , radiation therapy , anatomy
192 Ir sources besides being widely utilized in the field of conventional brachytherapy also find use in contemporary peripheral and coronal intravascular applications. In this study, the same Monte Carlo simulation code and input data were used to investigate differences between the dose rate distributions of the most commonly used192 Ir sources in the cm and mm distance range. Findings are discussed in view of differences in source and encapsulation dimensions as well as structural details. Results are presented in the AAPM TG‐43 formalism, as generalized by AAPM TG‐60, for five192 Ir HDR source designs as well as an LDR seed and an LDR wire source. Dose rate constants of the sources at r 0= 1 cm and r 0= 2 mm were found proportional to the corresponding geometry factors along the transverse source bisectors and an equation of the form Λ r 0( cGyh − 1 U − 1) = 1.12 × G ( r 0 , 90 ° ) provides results within clinical accuracy (less than 2%) for any192 Ir source. Radial dose functions do not depend significantly on source and encapsulation geometry and agree within 2% with that of a point192 Ir source. Anisotropy is of importance for accurate dosimetry at the cm distance range but it does not affect dose rate in the mm distance range significantly. At such short radial distances the source geometry factor defines the shape of isodose lines. Dose uniformity at given distances from the sources is strongly dependent on source dimensions as indicated by dose rate profiles in polar and Cartesian coordinates.