The role of EPID in vivo dosimetry in the risk management of stereotactic lung treatments

Background and objective In this work we report our experience with the use of in vivo dosimetry (IVD) in the risk management of stereotactic lung treatments. Methods A commercial software based on the electronic portal imaging device (EPID) signal was used to reconstruct the actual planning target volume (PTV) dose of stereotactic lung treatments. The study was designed in two phases: i) in the observational phase, the IVD results of 41 consecutive patients were reviewed and out-of-tolerance cases were studied for root cause analysis; ii) in the active phase, the IVD results of 52 patients were analyzed and corrective actions were taken when needed. Moreover, proactive preventions were further introduced to reduce the risk of future failures. The error occurrence rate was analyzed to evaluate the effectiveness of proactive actions. Results A total of 330 fractions were analyzed. In the first phase, 13 errors were identified. In the active phase, 12 errors were detected, 5 of which needed corrective actions; in 4 patients the actions taken corrected the error. Several preventions and barriers were introduced to reduce the risk of future failures: the planning checklist was updated, the procedure for vacuum pillows was improved, and use of the respiratory compression belt was optimized. A decrease in the failure rate was observed, showing the effectiveness of procedural adjustment. Conclusion The use of IVD allowed the quality of lung stereotactic body radiation therapy (SBRT) treatments to be improved. Patient-specific and procedural corrective actions were successfully taken as part of risk management, leading to an overall improvement in the dosimetric accuracy.