Abstract
The purpose of this study was to identify optimal CT acquisition parameter settings for each make and model of scanners used in a large Radiation Oncology (RO) Department, considering the special requirements of CT simulation. Two CT phantoms were used to evaluate the image quality of the five different multichannel CT scanners using helical scan mode. We compared the effects of various pitch, detector configurations, and rotation time parameters on image artifacts, and on spatial and contrast resolution. We found that helical artifact was closely related to pitch and detector configuration settings. This artifact was scanner‐specific and generally more obvious when the channel width or detector collimation was equal to the image thickness. Different acquisition parameter settings produced slight differences in observed high‐ and low‐contrast resolution. Short rotation time degraded image quality for certain scanners, but only slightly, while other rotation times, such as 0.75 sec/rotation and above, had no obvious effect on resolution. An optimized combination of acquisition parameters was determined for each scanner make and model, based on phantom image quality and other considerations for clinical applications. This information may be directly useful for physicists whose CT simulation scanners match one of the five examined in this study. If not, the strategy reported here may be used as a guide to perform a similar evaluation of the scanner.PACS numbers: 87.57.Ce, 87.57.qp, 87.55.Gh, 87.57.C‐
Highlights
Multi-channel CT has been widely accepted for diagnostic applications as well as for radiotherapy virtual simulation purposes
Because most patients undergoing CT simulation in radiation oncology (RO) have diagnosed cancers, and generally only one scan is used for CT simulation, radiation dose is of less concern than it is in diagnostic imaging (DI)
Artifact evaluation For all CT scanners, helical artifacts were more severe when the channel width was equal to the image thickness and a relatively high pitch was used
Summary
Multi-channel CT has been widely accepted for diagnostic applications as well as for radiotherapy virtual simulation purposes. The effect of CT acquisition parameters on image quality is important to all clinical applications, though the goals of the applications are quite different. A few studies[1,2,3,4,5,6] regarding optimizing acquisition parameters for certain applications in diagnostic imaging (DI) using multi-channel CT scanners partially addressed the effects of machine settings on image quality. The purpose of this study was to address this gap, and determine the optimal image acquisition parameter settings for conventional CT simulation protocols, including pitch (defined as couch movement per gantry rotation divided by beam width), detector configuration, and rotation time using several different CT scanners in our radiation oncology (RO) department. Routine radiation dose values were collected in order to help understand image quality characteristics between scanners
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