Implementing safe and robust Total Marrow Irradiation using Helical Tomotherapy - A practical guide.

Total Marrow Irradiation (TMI) with Helical Tomotherapy is a radiotherapy treatment technique that targets bone marrow and sanctuary sites prior to stem cell or bone marrow transplantation (SCT/BMT). TMI is a complex procedure that involves several critical steps that all need to be carefully addressed for a successful implementation, such as dose homogeneity in field junctions, choice of target margins, integrity of treatment and back-up planning. In this work we present our solution for a robust and reproducible workflow throughout the treatment chain and data for twenty-three patients treated to date. MATERIAL & METHODS:Patients were immobilized in a whole body vacuum cushion and thermoplastic mask. CT-scanning and treatment were performed in two parts with field matching at the upper thigh. Target consisted of marrow containing bone and sanctuary sites. Lungs, kidneys, bowel, heart and liver were defined as organs at risk (OAR). A fast surface scanning system was used to position parts of the body not covered by the imaging system (MVCT) as well as to reduce treatment time. RESULTS:All patients completed their treatment and could proceed with SCT/BMT. Doses to OARs were significantly reduced and target dose homogeneity was improved compared to TBI. Robustness tests performed on field matching and patient positioning support that the field junction technique is adequate. Replacing MVCT with optical surface scanning reduced the treatment time by 25 min per fraction. CONCLUSION:The methodology presented here has shown to provide a safe, robust and reproducible treatment for Total Marrow Irradiation using Tomotherapy.