Author: Michael B. Altman, Sharbacha Edward, Jose L. Garcia Ramirez, Anamaria Guta, Elizabeth Gaines Jeong, Justin K. Mikell, Phillip D. H. Wall, Jacqueline Esthappan Zoberi 👨🔬
Affiliation: Washington University School of Medicine in St. Louis, Washington University School of Medicine, WashU Medicine 🌍
Purpose: Modern HDR remote afterloaders (RAL) are equipped with enhanced safety features for accurate source positioning. However, little guidance is provided on the use of these features. We have clinically implemented the distal position correction (DPC) feature on a commercial RAL to adjust source positions to within 1mm of planned positions when the RAL reports 2mm adjustments via its automated length measurement. DPC requires several manual steps – enabling, executing, and visiting all channels to apply the source position adjustment in selected channels. We retrospectively evaluated our usage of the DPC.
Methods: Pre-treatment reports generated by Varian Bravos RALs were analyzed from December 2023 to January 2025 for all HDR treatments. Reports were parsed via in-house software to extract DPC enabled status, RAL automated length adjustments for each channel, and subsequent DPC for each channel. Usage of the DPC was judged by 1) the fraction of plans with DPC enabled and 2) whether execution of DPC followed our policy: length adjustment of 2mm requires DPC of 1mm in opposite direction.
Results: 671 reports were parsed. DPC was not enabled for 23 reports; 19/23 occurred in the first 4 months with 1/71 channels needing DPC, but not applied. Of the 648 reports with DPC enabled, DPC was not executed on 499 with 15/2360 channels needing DPC, but not applied. On the remaining 149 reports with DPC executed, DPC was nonzero on 381/1262 channels. A DPC of 1mm was applied to 381 channels; 36 times when not required. 881 channels had DPC of 0mm, with 2/881 reporting 2mm position discrepancies.
Conclusion: We have safely adopted DPC into our clinical practice to compensate for discrepancies between manual and automated length measurements. DPC inefficiently requires visiting all channels in a plan, which introduces the risk of applying position adjustments to channels not requiring it.