A Monte Carlo calculation of dosimetric parameters of 90Sr/90Y and 192Ir SS sources for intravascular brachytherapy

The AAPM TG-60 report has proposed various dose calculation parameters for intravascular brachytherapy (IVBT). These parameters include the dose rate constant (or the dose rate at a reference position for a beta-particle emitting source), the radial dose function, and the anisotropy function. In this work, we have used a modified EGS4 Monte Carlo system to calculate these parameters for the two most commonly used IVBT sources (the beta-particle emitting Sr-90/Y-90 source and the photon emitting Ir-192 SS source). To ensure the calculation accuracy, the present calculation was compared with several measurements and calculations reported by other authors. Excellent agreement was found for the results with the photon source. For beta-particle source calculation, the present results for a variety of point sources agree very well with a previous work. The presently calculated radial dose functions for the Sr-90/Y-90 source are consistent with those of a published work for intermediate radial distances. The dose uniformity in the axial direction was also studied. The contributions of bremsstrahlung photons to total doses for the Sr-90/Y-90 beta source, and the influence of ignoring electron transport on calculated doses for the Ir-192 SS photon source are discussed. (C) 2000 American Association of Physicists in Medicine. [S0094-2405(00)01211-6].