Purpose: To evaluate the feasibility of using volumetric modulated arc therapy (VMAT) using RapidArc to deliver total body irradiation (TBI) treatment. Methods: VMAT planning was performed a whole body computed tomography (CT) data set using Rapid Arc. The planning target volumes included entire body trimmed to 3 mm below the skin. The organs at risk included the lungs and kidneys. A dose of 12 Gy in 10 fractions was prescribed to the target volume. The VMAT-TBI technique consisted of three isocentres and three overlapping arcs: the head and neck, the chest, and the pelvis. The plans were prescribed to ensure, at a minimum, 95% planning target volume dose coverage with the prescription dose (percentage of volume receiving dose of 12 Gy was 95%) and maximum dose of 109.8%. Mean dose to lung was restricted at 8.6 Gy. Results: The total body volume in the study was 15469 cm 3 and the PTV volume was 11322 cm 3 . The mean dose to PTV was 104%. The homogeneity index was 0.09. Sparing of normal tissues with adequate coverage of skeletal bones was shown to be feasible with Rapid Arc. The study demonstrates that VMAT is feasible for TBI treatment. Unlike conventional TBI chest wall boost with electrons was not required. Conclusion: The technique for total body irradiation using RapidArc VMAT was found feasible and is undergoing further studies prior to clinical use.
Purpose: To evaluate and standardize gamma analysis for different RapidArc plans. Methods: 45 different RapidArc plans were selected for the analysis study. Verification plan was created for each treatment plans in Eclipse 10.0 TPS using the AAA algorithm. Gamma analysis Pre‐treatment quality assurance was done using 2D array combined with Octavius phantom. Analysis was done separately for head and neck, thorax and abdomen case using different dose difference (DD) and distance to agreement (DTA) passing criteria. Results: The standard gamma passing criteria (3mm, 3%) shows a good pass percentage for all the sites with an average passing percentage of 95.49 (SD ± 3.75), 97.82 (SD ± 1.95) and 97.89 (SD ± 2.43) with head and neck, thorax and abdomen cases respectively. But when comparing head and neck and thorax cases, there is a significant difference between 1% DD and 3% DD for thorax cases. Also there is a significant difference between 1% DD and 3% DD with thoracic cases when compared to head and neck and abdomen cases. P‐Value of 0.009 (for 1mm, 1% gamma), 0.003 (for 2mm, 1% gamma), 0.010 (for 3mm, 1% gamma) was observed when analysis was done comparing head and neck with thorax cases. Also significant changes were noted when comparing thorax cases with abdomen with P‐Value of 0.001 (for 1mm, 1% gamma), 0.003 (for 2mm, 1% gamma), and 0.047 (for 3mm, 1% gamma). Same conditions were observed when comparison done for thorax and abdomen cases, with a significance difference with thorax cases. Conclusion: It is recommended to standardize the gamma passing criteria for specific site rather than going for the standard (3mm DTA, 3% DD) criteria. Also it is suggested to choose lower DD passing criteria to know the mismatch areas in the fluence when ever analysis done with thoracic cases.
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