SU-E-T-468: Daily KV Cone-Beam CT and Deformable Image Registration as a Method for Studying Dosimetric Consequences of Anatomic Changes in Adaptive CRT of Lung Cancer

Abstract

Purpose: To evaluate anatomic lung tumor changes assessment and actually delivered doses utilizing the deformable kV CBCT Image Registration and compare to 3D CRT for lung cancer. Methods: Five patients diagnosed with lung tumors were treated with 3D CRT and daily KV CBCT images were acquired. Each of the kV CBCT and plan CT images were imported into the Deformable Image Registration (DIR) system. The generated CT image was deformed by the DIR system and new contours were obtained by using the adaptive re-contouring function of the DIR. These contours of 30 sets were individually marked CBCT contours and imported into Varian Eclipce system. The plan for each pair of the new contours and the original contours of the CT image was individually designed with 3D CRT with the same filed angle. These CBCT plans were added by applying a dose accumulation plan (DA plan)and were compared to CT plans. Results: The maximum, minimum, and mean doses to the PTV in the DA plans were avarage separately 1.2%, 29.7%, and 17% less than the CT plans. V5, V10, V20, V30and V50 of the left, the right lung and total lung in DA plans were less than those of the CT plans. The maximum dose of the spinal cord in the DA plans were avarage 27. 9% less than the CT plans. The mean dose of the left, right lung and total lung in the DA plans were reduced by 13.8%, 23.7%, and 15.3% respectively. Conclusion: The adaptive 3D CRT of DA plans based on the deformable registration provides dose escalation on lung cancer, which is helpful in improving the local control and excluding the surrounding normal tissues. It provides a method for further adaptive radiotherapy exploration.