Poster — Wed Eve—37: Phantom Study Comparing Image Quality of Slow‐CT and Average CT Dataset from 4DCT Radiotherapy Planning Acquisitions

Abstract

The purpose of this work was to compare slow‐CT () and average CT () datasets with free‐breathing helical CT () for contouring of organs at risk (OAR) and radiation treatment planning in patients receiving stereotactic body radiation therapy in lung. A quantitative examination of image quality parameters obtained from 4DCT‐derived datasets was performed using a mobile image quality phantom. The rigid phantom was translated in the superior‐inferior and anterior‐posterior directions through the CT scanning plane. Measurements of noise, low and high‐contrast resolution, spatial linearity, sensitometry, and observation of image artifacts resulting from phantom motion were recorded. In addition to these measurements, we computed the mean CT image () by increasing the number of breathing phases in the average CT calculation, and compared those image quality parameters with , and . While the image quality parameters were statistically the same in the phantom study, datasets had fewer image artifacts than the datasets. The image quality of the datasets improved greatly when the number of datasets used to generate the CTN was larger than the maximum permissible bins on the 4DCT reconstruction software (10 phases). or datasets may be used in place of for OAR contouring and potentially dose calculations, without significant compromise in image quality. This work demonstrates that when 4DCT is available, it may not be necessary to acquire a separate scan for OAR contouring.