Calculated dose impact of the image artifacts at the edges of the area from a wide-bore CT scans in radiotherapy treatment planning

Mini QC CT phamtom were used to imaging eFOV artefact, centrally and partially outside the sFOV with laterally shift and to analyze effects of artefact on CT number distortion and body contour variation. CT number distortion and body contour variation were analyzed maximum artefact region. In the later period, Reference baseline images of Alderson Rando phantom were acquired with the phantom centrally positioned within the sFOV. For comparison, the phantom were then shifted laterally from the center of the phantom 8 cm and 12 cm, ? x direction. The phantom external body contours were then automatically created with a fixed threshold of HU value by the treatment planning system. Critical organs and tissues were contoured by expert doctors and fictitious tumors was delineated as the target, located lung, prastate and breast. The treatment plans for the center position images set was first generated and to evaluate by doctors. Calculated MU, center of the fictitious tumors dose values and tumor median dose values were recorded. The same MUs were used for the subsequent treatment plans for off-center image sets to ensure comparable amount of radiation delivery in each beam configuration plans. The target dose calculated at the center of the tumor and the calculated median tumor doses, were recorded and compared for all treatment plans. Compared with the dose values of located centrally images, the dose values of off-center image sets obtained from the positive direction is increased.