갑상선 CT에서 스캔 파라메터 변화에 따른 선속 경화 현상 저감에 관한 연구

Abstract

The beam hardening artifact arising from complex shoulder structures in thyroid CT makes it difficult to capture anatomical fine details. Thus, the purpose of our study was to know appropriate scan parameters to reduce artifacts without significantly increasing the radiation dose. We utilized the GE Revolution APEX equipment for this study. We conducted the thyroid CT examinations by varying the thickness to 0.625 mm, 1.25 mm, and 2.5 mm, and adjusting the maximum mA to 300 mA, 600 mA, and 900 mA while applying auto exposure control system. The radiation dose was measured using a glass dosimeter placed at the thyroid location of the RANDO phantom. We measured signal to noise ratio (SNR) and contrast to noise ratio (CNR) of the experimental images to analyze the image quality of the thyroid area. As the slice thickness increases, the experimental dose also increases. The same pattern was observed for the maximum tube current. In terms of SNR, there is no difference between a slice thickness of 0.625 mm and 1.25 mm. However, there is a difference between measurements of 0.625 mm and 2.5 mm, and the same for 1.25 mm and 2.5 mm. No difference was observed in terms of tube current variations. The analysis of CNR reveals that there is not a significant difference as slice thickness and maximum tube current change. To improve quality of the images in complex shoulder structures, adjusting the scan parameters of thyroid CT affects not only SNR but also patient's radiation dose. Analyzing image quality through SNR showed that increasing the slice thickness improved the image quality. However, We should carefully use changes in parameters because the increase in slice thickness also involves an increase in radiation dose.