Accurate Real-Time Position Verification of an Ir-192 Source for Dynamic MR-Guided Single Fraction HDR Prostate Brachytherapy.

Hendrik de Leeuw¹, Marinus A. Moerland², Chris J.G. Bakker¹, Peter R. Seevinck¹

High-dose-rate brachytherapy with Iridium-192 can dramatically improve the efficiency of cancer treatment. To ensure accurate treatment, in particular for single fraction therapy, HDR requires independent treatment verification. CT imaging allows excellent HDR-source localization, but poor organ visualization and tumour delineation. Although MRI provides excellent soft tissue contrast, its geometric accuracy is usually questioned. Therefore, often CT and MRI are combined. Accurate MRI-guidance would be extremely useful for single-fraction HDR brachy-monotherapy. Herein the feasibility of near real-time Iridium source position verification using the co-RASOR imaging technique is demonstrated. The positions on co-RASOR and CT images are shown to correspond within 1mm.