Evaluating The Impact Of CT Scanning Parameters On Dose Calculations By The Treatment Planning System In External Beam Radiation Therapy

Abstract

This study sought to evaluate scanning parameters for Computed Tomography (CT) simulations and its impact on dose calculation by a treatment planning systems. A Computerized Imaging Reference System (CIRS) electron density phantom was scanned with a GE multi-detector scanner to acquire 1.25 mm slices in helical mode. Evaluations were done with the standard image reconstruction using a circular region of interest (ROI) from the measuring tool of the workstation software. Radiation therapy plans were prepared using the Eclipse Treatment Planning System (TPS) and an analysis of the influence of the scanning parameters over dose calculation was done. Scanning parameters can affect the dose calculation resulting in deviations between the TPS and Hounsfield Unit-relative electron density (HU-ED r) calibration curve. Such deviations may lead to uncertainties in the calculation of output dose in the radiotherapy plan. Changes in kilo-voltage peak (kVp) had a direct impact on the HU measured for each tissue-equivalent insert. The effects of different tube voltages on the HU for various tissue substitutes in the phantom, and their dosimetric impact on dose calculation in TPS is due to variations in the HU-EDr calibration curve.