Improvement of Simulation CT Imaging Protocol to Increase Accuracy in Determining Therapeutic Volumes of Soft Tissue Tumors

Abstract

Abstract Objective: In many cases, standard diagnostic CT scans used to treatment planning of soft tissue tumors. These protocols provide appropriate images for diagnostic purposes. The purpose of this study is to evaluate the imaging quality parameters of CT to optimize the protocol for accuracy and precision of treatment planning. Materials and methods: This study was conducted in two steps. In the first step, the effective parameters on detection of low-contrast objects evaluated objectively by using the ACR 464 phantom. Qualitative parameters include low contrast resolution, high contrast resolution, contrast to noise ratio, signal to noise ratio and noise. In this study, low contrast resolution and high contrast resolution were measured directly by using ACTS software. The signal to noise ratio, contrast to noise ratio and noise index were calculated based on image analysis by using the formulas. In the next step, the percentage of error in the contouring was measured subjectively for the high-contrast and standard protocols. Results: The protocol with higher mA and lower Kv lead to dose increasing of *81.89%. As well as contrast-to-noise ratio and signal-to-noise ratio increased by *76,73% and 61.13%, respectively, and noise decreased by 58.44%. The error percentage values in the contouring of the low contrast object in Module 2 for the standard protocol and the high contrast protocol were 0.2469 and 0.00706, respect ively. Keyword: radiotherapy, CTsimulation, image quality, tumor contouring