الفهرس 
Dosimetric evaluation of patient setup errors via IG-IMRT
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Abstract
The goal of radiotherapy treatment is to deliver maximum dose to tumor and minimum dose elsewhere. During fractionated radiation therapy, setup errors are an inherent part of the radiation treatment process. Image Guided Radiation Therapy (IGRT) can used to increase the agreement between planned treatment and actual delivered dose to patient. In this work setup errors are detected using Kilo-voltage Cone Beam Computed Tomography (kV-CBCT). The specific patient (personalised/individual) setup errors are applied on Head and Neck (H&N) and prostate Intensity Modulated Radiation Therapy (IMRT) treatment plans using Simultaneous Integrated Boost (SIB) technique by varying the plan isocenter in order to evaluate the extent of the effect of setup errors and to investigate their impact on target volumes with the help of Dose-Volume Histogram (DVH) parameters and dosimetric indices. Results show that prostate systematic errors are 0.44, 0.54 and 0.73 mm while random errors are 3.16, 2.46 and 3.87 mm in LR, SI and AP directions, respectively. H&N systematic errors are 0.32, 0.28 and 0.23 mm while random errors are 2.22, 2.26 and 1.83 mm in LR, SI and AP directions, respectively. For 23 H&N patients, significant differences (p-value < 0.05) are reported between original and shifted Planning Target Volumes (PTVs) due to setup errors. After consideration of setup errors for the three investigated target volumes (target-70, target-60 and target-54), the mean dose delivered to 95% of target volume (D95%) is significantly reduced from 58.6 to 57.2 Gy for target-60, significant deteriorations in target dose homogeneity for target-70 and target-60 are measured using the Homogeneity Index (HI) while no significant change in dose conformity is detected using Conformity Index (CI). For 12 prostate patients, at individual level, the D95% is always higher for original isocenter compared to shifted isocenter for target-81 and target-56. The mean D95% value is significantly (p < 0.05) reduced from 78.6 to 73.9 Gy and from 54.4 to 52.8 Gy for target-81 and target-56, respectively. Significant reduction in the dose conformity is observed for target-81 as measured using CI parameter. Significant reduction in the homogeneity of target dose distribution (higher HI values) for shifted targets (50% and 69% for target-81 and target-56, respectively) is also reported compared to original plans