(Wednesday, 7/17/2019) 10:00 AM - 10:30 AM
Room: Exhibit Hall | Forum 5
Purpose: We report the frequencies of offline adaptive re-planning in our clinic with and without the use of automated dose calculation and tracking (ADCT) upon daily pre-treatment image-guided radiotherapy (IGRT) CT images.
Methods: The Radixact helical tomotherapy treatment system (Accuray, Inc.) includes an on-board megavoltage fan-beam CT (MV-FBCT) for daily IGRT. The ADCT system was implemented within a software module (PreciseART, Accuray) which automatically calculates dose upon the daily MVCT image, tracks daily dose changes, and triggers adaptive re-planning based on user-defined dose-volume criteria. We enrolled 204 tomotherapy patients into this ADCT module. For comparison, we estimated the re-planning rate for cases where pre-treatment IGRT is also acquired, but in the absence of ADCT, based on 202 patients planned and treated using VMAT and kilovoltage cone-beam CT for IGRT.
Results: Among all cases using ADCT, the adaptive re-planning rate was 23 percent, while the re-planning rate among all patients without ADCT was 13 percent. Among prostate cases, the re-planning rate was 14 percent with ADCT versus 4 percent without ADCT; for female pelvis, 30 percent of the cases with ADCT were re-planned versus 13 percent of the cases without ADCT. The increased re-planning rates are primarily attributed to the use of ADCT, which allows easier identification of dose deviations (e.g. PTV under-dosing or OAR over-dosing). The re-planning rates for head-and-neck cancer (HNC) cases were similar with or without ADCT, 33 versus 31 percent respectively. This may be because the way that anatomic changes affect daily dose delivery is better understood for HNC than for other tumor sites.
Conclusion: The automated daily dose calculation and dose tracking increases the frequency of offline adaptive re-planning during the delivery of radiation therapy. Integrating ADCT in daily MV-FBCT guided radiation therapy improves the clinical practice of adaptive re-planning.
Keywords
Cone-beam CT, Image-guided Therapy, Megavoltage Imaging
Taxonomy
TH- External beam- photons: adaptive therapy
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