Room: Exhibit Hall
Purpose: DIBH for right sided breast cancer treatment reduces radiation dose to right coronary artery (RCA), heart, and lung compared to free breathing treatment. However for patients who cannot maintain breath hold during treatment, the accuracy of dose delivery is affected. Surface guidance with AlignRT (Vision RT, UK) is used to capture and track the surface motion during treatment. Our aim was to investigate a method to calculate the real time treatment delivered dose, and accumulated dose using the surface tracking.
Methods: A right-sided breast cancer patient was planned using Pinnacle treatment planning (Philips, WI) using the DIBH-CT scans with a prescription dose of 50Gy in 25 fractions. During the treatment monitoring, the real-time deltas with 5.9 frames per second were acquired in AlignRT. The average real-time delta (3 translations and 3 rotations) was used to reconstruct real-time CT images by applying rigid registration to the DIBH CT scans. The constructed CT image was used to compute the real-time target dosimetry.
Results: According to the DIBH plan, the calculated CTV mean dose was 5322cGy, while the real-time breast CTV mean dose in a monitoring session was only 4839cGy. The reduction of CTV dose was 9.1%. The minimum CTV dose decreased from 1707cGy to 288cGy. This does change corresponding with the real time delta: vertical -3.8mm, longitudinal -1.0mm, lateral 2mm, rotation -0.58Â°Â°, roll 0.42Â°Â° and pitch 1.42Â°.
Conclusion: Surface tracking data from the AlignRT can be used to reconstruct the real-time target dose. This can set breathing tolerance for DIBH. Additional right breast DIBH plans will be studied. Since Heart and Lung are most likely to deform non-rigidly relative to the patient surface, further biomechanical modeling and real-time imaging study will decipher the relation between surface tomography and OAR motion.