Dose evaluation of multi-slice CT for different parameters in chest examinations using TLD method

In radiodiagnosis, optimization is defined as a method of reducing the patient-absorbed doses without affecting image quality. In this study, we aimed to determine the parameters of a multi-slice CT (MSCT) scanner (LightSpeed VCT 64; General Electric) that ensure the least organ dose with the best image quality (i.e., optimization) for chest examinations, which are the most frequently used radio diagnostic investigations. Organ doses of an anthropomorphic phantom were measured during MSCT chest scans by using GR-100 (LiF: Mg, Ti) thermo-luminescent dosimeters (TLDs) attached to various parts of the organs. The accumulated equivalent doses were calculated to evaluate the radiation risk to sensitive organs by using different scan conditions and measuring the absorbed doses, because different scan parameters (e.g., pitch, tube current, scan type, etc.) may affect the dose contribution to these organs. By means of the radiation and tissue weighting factors recommended in the International Commission on Radiological Protection (ICRP) 103 report, the effective dose was then estimated. The pitch value and tube current were the main parameters affecting the organ doses of the phantom: increase in the pitch value and reduction of the tube current decreased the absorbed doses without impacting the image resolution and diagnostic information. Consequently, radiologists can establish an optimization protocol in MSCT and acquire high-resolution images with adequate diagnostic information while using the lowest exposure dose for chest examinations.