Abstract
Purpose Recent studies have identified that among different available radionuclides, the dose characteristics and shielding properties of ytterbium-169 ( 169Yb) and thulium-170 ( 170Tm) may suit high–dose rate (HDR) brachytherapy needs. The purpose of this work was to compare clinically optimized dose distributions using proposed 169Yb and 170Tm HDR sources with the clinical dose distribution from a standard microSelectron V2 HDR iridium-192 ( 192Ir) brachytherapy source (Nucletron B.V., Veenendaal, The Netherlands). Methods and materials CT-based treatment plans of 10 patients having prostate volumes ranging from 17 to 92 cm 3 were studied retrospectively. Clinical treatment of these patients involved 16 catheters and a microSelectron V2 HDR 192Ir source. All dose plans were generated with inverse planning simulated annealing optimization algorithm. Dose objectives used for the 192Ir radionuclide source were used for the other two radionuclides. The dose objective parameters were adjusted to obtain the same clinical target (prostate) volume coverage as the original 192Ir radionuclide plan. A complete set of dosimetric indices was used to compare the plans from different radionuclides. A pairwise statistical analysis was also performed. Results and conclusions All the dose distributions optimized with specific 192Ir, 169Yb, and 170Tm sources satisfied the standard clinical criteria for HDR prostate implants, such as those for the Radiation Therapy Oncology Group clinical trial 0321, for combined HDR and external beam treatment for prostate adenocarcinoma. For equivalent clinical target volume dose coverage, the specific 169Yb and 170Tm sources resulted in a statistically significant dose reduction to organs at risk compared with microSelectron V2 HDR 192Ir source. This study indicates that a 170Tm or 169Yb radionuclide source may be an alternative to the 192Ir radionuclide sources in HDR brachytherapy.
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