Room: Exhibit Hall | Forum 9
Purpose: To analyze the changes of the volume and dosimetry of target and organs at risk by comparing the daily CBCT images and planning CT images of the Patients with NSCLC, analyze the difference from planned dose and accumulated delivered dose, and try to find the best time to replan for patients with NSCLC.
Methods: This study retrospectively analyzed eight cases of non-small cell lung cancer patients who accepted CRT or IMRT treatment and KV-CBCT. Deform the daily CBCT images to planning CT images in RayStation, and superposition daily CBCT implementation dose to planning CT by the mapping of registration to compare the planning dose with cumulative dose of targets and organs at risk (left and right lung, spinal cord, heart).
Results: The average volume of GTV of 8 patients with CBCT was 88.26% of the original volume. The average plan dose of GTV was 1166.49Â±645.42cGy. The accumulated dose of GTV was 1150.13Â±630.27cGy (Pï¼œ0.05). The average volume of PTV to reach the prescription dose was 95.59% for original plan and 81.47% for accumulated plan (Pï¼ž0.05). The volume changes of the left and right lung of the original volume was 88.95% and 80.32%, respectively. The average dose of the left and right lung of original plan was 167.31Â±165.75cGy and 79.33Â±54.11cGy, respectively. The average accumulated dose was 164.63Â±164.96cGy and 77.63Â±53.36cGy, respectively. There was no significant difference. The average plan dose and accumulated dose of heart was 61.88Â±66.70cGy and 68.38Â±60.91cGy, respectively (Pï¼ž0.05). The average plan maximum dose and accumulated dose for spinal cord was 372.62Â±185.91cGy and 360.00Â±173.14cGy, respectively (Pï¼ž0.05).
Conclusion: The changes of target anatomical structure of patients with NSCLC make difference between the planned dose and cumulative dose. With the dose deformation superposition method, the gap can be found between planning dose and implementation dose.