Development and clinical validation of Knowledge-based planning for Volumetric Modulated Arc Therapy of cervical cancer including pelvic and para aortic fields.

BACKGROUND AND PURPOSE: Knowledge-based planning (KBP) is based on a model to estimate dose-volume histograms, configured using a library of historical treatment plans to efficiently create high quality plans. The aim was to report configuration and validation of KBP for Volumetric Modulated Arc Therapy of cervical cancer. MATERIALS AND METHODS: A KBP model was configured from the institutional database (n = 125), including lymph node positive (n = 60) and negative (n = 65) patients. KBP Predicted plans were compared with Clinical Plans (CP) and Re-plans (Predicted plan as a base-plan) to validate the model. Model quality was quantified using coefficient of determination R2, mean square error (MSE), standard two-tailed paired t-test and Wilcoxon signed rank test. RESULTS: Estimation capability of the model was good for the bowel bag (MSE = 0.001, R2 = 0.84), modest for the bladder (MSE = 0.008) and poor for the rectum (MSE = 0.02 R2 = 0.78). KBP resulted in comparable target coverage, superior organ sparing as compared to CP. Re-plans outperformed CP for the bladder, V30 (66 ± 11% vs 74 ± 11%, p < .001), V40 (48 ± 14% vs 52 ± 14%, p < .001), however sparing was modest for the bowel bag V30 (413 ± 191cm3 vs 445 ± 208cm3, p = .037) V40 (199 ± 105cm3 vs 218 ± 127cm3, p = .031). All plans were comparable for rectum, while KBP resulted in significant sparing for spinal cord, kidneys and femoral heads. CONCLUSION: KBP yielded comparable and for some organs superior performance compared to CP resulting in conformal and homogeneous target coverage. Improved organ sparing was observed when individual patient geometry was considered.

Implementation of a visual feedback system for motion management during radiation therapy.

PURPOSE: To describe the details of an in-house video goggles feedback system assembled from several commercially available components. The objective of this paper is to share our experience with this system, provide details on the equipment needed, system assembly, patient set up and user settings on some components. MATERIALS AND METHODS: The system consisted of goggles (FPView3DHD, ITV, USA), RJ45(Registered Jack) to Digital Visual Interface (DVI) converter (Tripplite), DVI to HDMI converters, Local Area Network(LAN) cable, HDMI and power extender cables. The video coaching system was implemented both in CT simulator (GE Discovery)) and in treatment delivery machine True Beam v2.1 Varian Medical Systems (VMS, Palo Alto), which was integrated with respiratory motion management (RPM V 1.7.5) system. RESULTS: The video feedback system is in clinical use since Aug 2017, so far, we have treated 13 patients, with approximately 150 fractions. The performance of the device was found to be satisfactory. All the patients were coached for DIBH and the usage of the goggles, which includes wearing the goggles, display details of the monitor, and the threshold levels of the breathing wave cycle. The patients understand the instructions very well and hence regulate the breathing cycle, which improves the treatment accuracy and efficiency. CONCLUSION: Video feedback system for motion management, for patients undergoing radiotherapy was implemented successfully both in CT simulator and in linear accelerator.