Implementing butterfly volumetric modulated arc radiotherapy (VMAT) with deep inspiration breath hold (DIBH) for mediastinal lymphomas

Introduction: Radiotherapy for mediastinal lymphomas is associated with significant long term side effects particularly to the heart, lungs and breasts1&2. Studies have shown that the butterfly technique can reduce dose to these organs3. This technique was implemented in combination with voluntary DIBH to manage target volume motion and reduce dose to the heart. Voluntary DIBH allowed the target volume to contract left/right and elongate anterior/posterior so that the main mediastinal volume was positioned away from the lungs and heart. Voluntary DIBH does not involve costly equipment and is well tolerated by patients. The technique was adapted from the breast protocol previously implemented in the department. Method and Materials: Patients were scanned in a modified 7 point thermoplastic shell, made with the patient in voluntary DIBH (patient breathing after every 20seconds before going back into breath-hold). Measurements from the alignment tattoos to in room lasers during voluntary DIBH at CT were recorded and DIBH stability maintained during treatment by visual alignment of lasers to reference marks drawn on using the recorded measurements. Organs at risk and clinical volumes were outlined. Field placement was considered carefully as the angles were limited due to the large head of the Varian LINACS. Routinely superior/inferior, anterior, and posterior arcs were used. Depending on the size and position of target volume another lateral beam may utilised. Planned using Pinnacle SmartArc with arcs split to keep within a 20second limit. Results: Implementation: A Day 0 was introduced for a dummy run. Patients practiced holding their breath for 20seconds, however the CBCT/arcs took longer. CBCT/treatment was interrupted to allow the patient to breathe normally before commencing breath hold again. Pitch caused set-up issues in 7 cases. Most patients were able to comply with consistent breath hold. CT, planning and Treatment times are longer which can have an impact on a busy department. Conclusion and Discussion: A total of 13 patients have been treated with this technique. Further work is being undertaken to investigate the average treatment times, DVHs and imaging.

Citation

Salmon, C., et al. (2020). Implementing butterfly volumetric modulated arc radiotherapy (VMAT) with deep inspiration breath hold (DIBH) for mediastinal lymphomas. Radiography, 26(S1), S26. https://doi.org/10.1016/j.radi.2019.11.063

URI

https://hdl.handle.net/20.500.14709/1044