Implication of Filters on the Accuracy of Radiotherapy Planning and the Need for Recalibration of the CT-to-ED Curve

Abstract

This article examines the effect of the presence or absence of an ImAR filter on the calibration curve for converting X-ray tomography (CT) data to relative electron density (CT-to-ED) values for the abdominal region and head. On CT images this results in distortion of Hounsfield Units (HU) values. The latter, in turn, can lead to inaccuracies in the CT-to-ED calibration curve.
 Conclusions: If the filters are set up correctly and applied according to the planning system manufacturer's recommendations, changes in the CT-to-Ed curve should be negligible. CT-to-ED curves are an important tool for improving the accuracy and quality of radiation therapy for cancer.