Comparison among four immobilization devices for whole breast irradiation with Helical Tomotherapy

Purpose: To evaluate the repositioning accuracy of 4 immobilization devices (ID) used for whole breast Helical Tomotherapy treatments: arm float with VacFix® (Par Scientific, Denmark), all-in-one® (AIO®) system (Orfit, Belgium), MacroCast thermoplastic mask (Macromedics, The Netherlands) and BlueBag® system with Arm-Shuttle (Elekta, Sweden).

Materials and methods: Twenty four women with breast cancer with PTV including the breast/chest wall and lymph nodes were involved in this study (6 women per group). Pretreatment registration results were first collected using automatic bone registration + manual adjustment on the vertebra followed by independent registrations on different ROIs representing each treated area (axillary, mammary chain, clavicular, breast/chest wall). The differences in translations and rotations between reference registration and the above mentionned ROIs were calculated. A total of 120 MVCT images were analyzed.

Results: Significant differences were found between IDs (p < 0.0001), ROIs (p = 0.0002) and the session number (p < 0.0001) on the observed shifts, when examining 3D translation vectors. 3D-vectors were significantly lower for the BlueBag® than for the VacFix® or for the AIO® (p < 0.0001), but differences were not significant compared to the mask (p = 0.674). Finally, setup margins were overall smaller for the BlueBag® than for other IDs, with values ranging from 1.53 to 1.91 mm on the mammary chain area, 4.52-6.07 mm on the clavicular area, 2.71-4.62 mm on the axillary area, and 3.39-5.10 mm on the breast.

Conclusion: We demonstrated in this study that the BlueBag® combined with arm shuttle is a robust solution for breast and nodes immobilization during HT treatments.