Author: Shifeng Chen, Mariana Guerrero, Brian A. Hrycushko, Kai Huang, Kai Jiang, Narottam Lamichhane, Paul M. Medin, Elizabeth Nichols 👨🔬
Affiliation: Department of Radiation Oncology, UT Southwestern Medical Center, University of Maryland School of Medicine, Department of Radiation Oncology, University of Maryland School of Medicine, Department of Radiation Oncology, University of Maryland Medical Center 🌍
Purpose: Unloaded needle catheters, if not handled properly, pose a risk for channel misconnection in interstitial high dose rate (iHDR) brachytherapy. This study aims to investigate the dosimetric impact of needle misconnection for Syed template-based iHDR in gynecological cancers.
Methods: Clinical treatment plans for 72 Syed iHDR cases were created in an Oncentra® Brachy planning station. For each case, unloaded needles were considered to be at risk for channel misconnection if their locations were within 1-cm of a loaded needle with the same length. In a simulated plan, the active dwell points from the nearest loaded needle were transferred to the unloaded needle. Dose was calculated for the clinical and simulated plans using a previously-validated Matlab-based HDR dose engine. Changes in dose volume histogram (DVH) metrics were quantified for the target volume D90%, V90%, D100%, V100%, V150%, as well as the D2cc of critical organs at risk (OARs).
Results: Unloaded needles posing a misconnection risk were identified in 52 of the 72 (72.2%) cases. A dosimetric comparison of clinical versus simulated treatment plans revealed that channel misconnection resulted in <±1% changes in all quantified DVH metrics for 14 out of these 52 cases. In 26 cases, the simulated plans had a >±3% change in at least one DVH metric, while 19 and 9 cases showed over ±5% and ±10% changes. The maximal drop in target volume coverage was 50%, whereas the largest dose increase in OAR D2cc was 116.9%.
Conclusion: Channel misconnection to unloaded needles may lead to significant under-coverage of the target and/or dose increase to OARs in iHDR brachytherapy. Clear labelling/documentation of unloaded needles and a second check of channel connections are essential elements of the workflow for iHDR to avoid these dosimetric errors.