Purpose: The use of deep inspiration breath-hold (DIBH) for respiratory gating in radiotherapy targeting left-sided breast cancer has led to significant reduction of radiation dose to the heart and lungs. The aim of this study was to assess the DIBH respiratory traces.
Methods: 45 left breast cancer patients with a mean age of 60.6 (SD 11.1) years were enrolled in this study. The patient was coached and asked to perform at least three breath-hold (BH). In total, 146 DIBH traces were acquired and collected during CT simulation using Varian Real-time Position Management (RPM) system. The DIBH respiratory traces stability and reproducibility within the gating window were assessed. The correlation between the DIBH stability/reproducibility and other parameters such as age, isocenter drift, and DIBH amplitude were analyzed.
Results: The mean of DIBH stability and DIBH reproducibility were 0.4385 cm (SD 0.2233) and 0.3462 cm (SD 0.2905) respectively. 65% of patients had stability less than 0.5 cm and 80.0% of patients had reproducibility less than 0.5 cm. The difference between free-breathing and DIBH amplitude showed an average of 2.10 cm (SD 0.75). The optimal gating window was 0.70 cm (SD 0.52). The DIBH reproducibility showed significant correlation with isocenter drift (r=0.47, p=0.0012). Patients older than 60 years showed significant increased variability in DIBH stability (F = 4.87, P = .0007).
Conclusion: We analyzed DIBH respiratory traces for left breast cancer patients, the optimal gating window was 0.7 cm. The range of 0 to 0.5 cm is advisable for DIBH reproducibility and stability. Additional coaching may be needed for patients older than 60 years. The finding of this work could be used as a metric tool to identify the potential candidate for the DIBH technique.