On the dosimetric accuracy of a Sievert integration model in the proximity of 192Ir HDR sources.

PURPOSE

To investigate the efficacy of a Sievert integration model in dosimetry close to 192Ir high-dose-rate brachytherapy sources and validate its accuracy and potential to resolve dosimetric differences between these sources in the cm and mm distance ranges relevant to interstitial and intravascular brachytherapy applications, respectively.

METHODS AND MATERIALS

The dosimetric quantities of the generalized Task Group 43 formalism, as well as dose rate profiles in polar and Cartesian coordinates, are calculated, and results are compared to corresponding Monte Carlo data in the literature.

RESULTS

Sievert calculations were found in excellent agreement with corresponding Monte Carlo published results. Dose rate polar angle profiles in the cm distance range depended significantly on corresponding anisotropy function data, whereas in the mm distance range, dose rate polar angle profiles are governed by the corresponding geometry function profiles, because anisotropy proved insignificant. Radial dose functions of the sources were found comparable. A simple equation for the calculation of the dose rate constant of the sources within clinically acceptable accuracy is provided.

CONCLUSIONS

The particular Sievert model proved capable of resolving dosimetric differences of the sources and provides results within clinical accuracy. Therefore, it constitutes a useful tool for dosimetry in clinical practice and especially in intravascular applications, where there is currently a lack of available dosimetric data.