Program Information
A Clinical Treatment Dose Monitoring System Based On CBCT
A Qin*, J Liang , D Yan , William Beaumont Hospital, Royal Oak, MI
Presentations
WE-F-605-2 (Wednesday, August 2, 2017) 1:45 PM - 3:45 PM Room: 605
Purpose: To monitor delivered dose and trigger plan adaptation when necessary, an automatic treatment dose (Tx-dose) reconstruction system based on CBCT was developed and evaluated on various cancer sites.
Methods: An in-house system was developed which includes three modules: Treatment Schedule Monitoring module (TSM), Pseudo-CT Generating Module (PCM) and Treatment Dose Reconstruction module (TDR). The workflow is as following: the image specialist, who conducts daily CBCT evaluation, requests Tx-dose when significant anatomic or motion variation is observed. TSM will watch the treatment progress in MOSAIQ and trigger PCM when CBCTs are available. PCM will perform pre-treatment CT to CBCT deformable registration (DIR), and map the CT intensity to CBCT to generate Pseudo-CT. A novel phase-matching DIR were developed to generate 4D-Pseudo-CT for lung cancer treatment. TDR module is then started to create Pinnacle scripts to reconstruct Tx-dose on Pseudo-CT. Finally, the Tx-doses are warped to plan-CT and accumulated through all delivered fractions as cumulative dose via DIR. For lung patients, the 4D-dose is calculated on both 4DCT and 4D-Pseudo-CT and warped to the end of inhale phase of the plan-CT. To minimize extra clinical workload, the system is designed to run mostly automatic with few user interactions. Eight recent treated patients (five SBRT-lung, two head&neck, one breast) were retrospectively evaluated. Clinical relevant dosimetric parameters were extracted from the final cumulative Tx-dose and compared with the planned ones.
Results: For 5 Lung patients, D99 of the final cumulative dose of GTV is 95.9±2.5%(93.6-100.1%) of that of originally planned. One of two head&neck patient had 3%decrease in CTV D99 and 11.5%increase of ipsilateral-parotid mean dose due to weight loss. The D99 of the breast patient CTV decreased to 93.5%.
Conclusion: We have demonstrated the feasibility and effectiveness of a treatment dose verification system on various cancer sites in our clinical setting.
Funding Support, Disclosures, and Conflict of Interest: This research was supported by Elekta R&D funding.
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