Using deformable registration to assess dosimetric impact of variability in deep inspiration breath hold (DIBH) levels for left breast treatment

BACKGROUND: In deep inspiration breath hold (DIBH) left breast radiation treatment, dosimetric impact of variation within breath hold (BH) tolerances has not been precisely quantified. PURPOSE: Estimate target and organs at risk (OAR) dose variations due to patient movements within BH target tolerances, and assess impacts on 3DCRT, VMAT and pseudo skin flash planning. METHODS: ), heart, lung, and breast mean doses, and heart hotspot (D1cc) were evaluated at each deviation. RESULTS: Deformable registration demonstrated relative motion of the target and OARs not previously observed with simple rigid registration methods. Target coverage in 3DCRT plans were more robust against BH target variation compared to VMAT and pseudo skin flash. However, pseudo skin flash show comparable target coverage to 3DCRT for BH target overshoot. With 3DCRT, the heart hot spot shows significant individual variations in the undershoot regime. CONCLUSION: Deformable registration-based dose estimation reveals complex organ motion with significant individual variability in plan robustness. 3DCRT is less sensitive to BH variability than VMAT. Our protocol potentially enables individualized approach to selecting technique and tolerances based on patients' DIBH movements.