RESUMO
Background: In locoregional radiotherapy of breast cancer with deep inspiration breath hold (DIBH), setup accuracy may depend on hospital protocol. At present, comparison between different positioning devices is challenging due to differing hospital protocols. The aim of this study was to evaluate the setup accuracy obtained with surface-guided radiation therapy (SGRT; AlignRT®, Catalyst™) or with lasers and real-time position management (RPM™) in DIBH. Materials and methods: A total of 1692 image pairs were analyzed in three groups: positioning using AlignRT® surface guidance system (Group A, n = 45), Catalyst™ (Group C, n = 50) and conventional lasers and tattoos (Group L, n = 46). We evaluated residual errors for the bony chest wall, th1 and humeral head in kV images with laser- or SGRT-based setup with and without daily image-guided radiation therapy (IGRT). Results: Less isocenter variance was found in Group A than in Group L or C (p ≤ 0.05) and in Group C than in L (p = 0.02-0.6). With SGRT only, the smallest random rotation error was found in Group A (p = 0.01). With daily IGRT, only a small difference was found for residual errors between the groups. Conclusion: Setup with SGRT improves the isocenter reproducibility compared to lasers and RPM™. Only small differences were found in setup accuracy between the SGRT devices. Due to improved isocenter accuracy, daily orthogonal IGRT is suggested in all the groups.
RESUMO
BACKGROUND: Setup accuracy within adjuvant radiotherapy of breast cancer treated in free breathing is well studied, but a comparison of the typical regions of interest (ROI) used in surface guided radiation therapy (SGRT) does not exist. The aim of this study was to estimate the setup accuracy obtained with differently shaped ROIs in SGRT. MATERIALS AND METHODS: A total of 573 orthogonal image pairs were analyzed from free breathing breast patients in two groups: positioning using AlignRT® surface guidance system (Group A, n = 20), and setup using conventional laser and tattoo setup (Group L, n = 20). For SGRT, three different setup ROIs were used: a Breast-shaped, O-shaped and T-shaped (B-O and T-ROI). We evaluated the isocenter-, rotation-, pitch and arm position accuracy and residual errors for the chest wall and shoulder joint in kV orthogonal and tangential setup images with laser- or SGRT-based setup. RESULTS: Less isocenter variance was found in Group A than in Group L. Rotations and posture errors were larger in group L than in Group A (p ≤ 0.05). Rotation error was smaller with T-shaped ROI than with O- or B-shape (p = 0.01-0.04). CONCLUSION: Setup with AlignRT® improves reproducibility compared to laser setup. Between the different ROI shapes only small differences were found in the patient posture or the isocenter position in the images. The T-ROI is recommended to set up the chest wall bony structure and an additional B-ROI may be used to fine-tune the soft tissue accuracy.
