A National Multi-Institutional Survey of Comprehensive Workflow and Quality Assurance In Cs-131 Tile Implants for Intracranial Tumors
Abstract
Purpose
Cs-131 tile implant–based intracranial brachytherapy requires coordinated interdisciplinary efforts spanning imaging, source management, implantation, post-implant planning, and radiation safety. The extent of inter-institutional variability in these practices remains undefined. This study characterizes current practices to identify areas of variability relevant to quality assurance (QA) and standardization.
Methods
An anonymous 55-question survey addressing personnel involvement, workflow practices, pre- and post-operative imaging, contouring, dosimetry and treatment planning, QA, and radiation safety was distributed to medical physicists at 12 U.S. institutions with active GammaTile programs. Responses were analyzed descriptively.
Results
Medical physicists routinely participated in patient selection (83.3%) and tile estimation/ordering (75.0%). Pre-operative imaging protocols varied: 83.8% centers required T1-weighted MRI imaging, often 1–2 mm slice thickness; while allowable pre-op MRI validity ranged from 7–30 days. Tile count estimation primarily used the GammaTile-lookup table (66.6%) with 25.0% used in-house techniques or clinical experience. Minimum ordering lead-time policies existed in 83.8% centers; seed-use-validity in case of delay in surgery varied (0–2 days). Independent seed-strength verification practiced in 75.0% of centers using ADCL-calibrated reentrant well chambers (58.3%) or cross-calibrated dose-calibrators (33.3%); 58.3% reviewed vendor assay reports. Post-operative resection cavity contouring though nearly universal (91.6%), revealed substantial variability in delineation methods, imaging modality/protocols (MRI/CT), target naming convention, definition, margin application (0–5 mm), and inclusion of residual enhancing disease (58.3%). Target V100, and D90 reporting were relatively consistent, while organs-at-risk dose reporting was inconsistent (always-25.0%, optional-75.0%). Secondary independent dose verification was infrequent (16.7%). Radiation safety practices showed greater consistency for select steps (e.g., pregnancy-related time-outs in 75.0%), with variability in personal protective equipment use, and patient release recommendations.
Conclusion
This multi-institutional survey identified substantial practice variability spanning pre-operative imaging protocols, ordering/verification workflows, post-implant contouring/planning, and secondary QA. Standardization priorities necessitate coordinated, consensus-driven implementation to ensure reproducibility, consistency, safety, and scientific validity.