Dual energy CT와 Spectral CT를 이용한 선량 및 물질변화 따른 유용성 비교

Comparison of usefulness according to dose and change of substance, using Dual energy CT and Spectral CT

목적: Dual energy CT와 Spectral CT를 사용하여 선량과 Iodione함유량, 물질 별로 각 장비의 단일에너지 유용성를 비교해 보고자한다. 대상 및 방법: 장비는 SIEMENS사의 192 (384)Channel Dual source SOMATOM Force와 Philips사의 IQon Spectral CT를 사용하였고, 본 실험 사용된 팬텀은 인체조직등가물질을 표현한 Tissue Characterization Phantom (Gammex467), 촬영조건은 두 장비 동일한 조건으로 하여 CTDIvol를 20 mGy, 30 mGy, 40 mGy,로 설정하여 Helical scan하였다. 또한 조영제 Phantom은 Iodine을 2.5 mgI/mL, 5 mgI/mL, 7 mgI/mL 10 mgI/mL, 15 mgI/mL를 생리식염수와 혼합하여 Total Volume 50 ml로 자체 제작하였다. 조직Phantom과 조영제Phantom을 장비 별로 스캔 후 Monoenergetic image를 얻어 40 keV에서100 keV의 해당하는 HU값을 비교해보았다. 결과: 조직Phantom과 조영제Phantom을 CTDIvol변화를 줘 검사하였을 때 여러 에너지의 monoE[keV]가 HU값은 크게 변하지 않았으며 두 장비 모두 비슷한 값을 제공하였다. Water와 liver와 같은 CT Number값이 낮은 물질들은 40 keV에서100 keV로 올렸을 때 다른 조직들보다 변화의 폭이 적음을 알 수 있었고. Iodine과 CB2 Resin-30 % CaCO3와 CB2 Resin-50 % CaCO3을 비교해 보았을 때, MonoE값을 40keV에서100 keV으로 올렸을 때 HU값 또한 두 장비 모두 큰 폭으로 변화하였다. 결론: Dual energy CT와 Spectral CT에서 MonoE[keV]값은 유의하게 측정되었으며, 임상에 적용 시 결석과 같은 칼슘을 함유하고 있는 물질 경우 MonoE를 이용하여 연부조직과의 차이를 분석하여 진단 폭을 한층 넓혀줄 것으로 사료된다.

Purpose: This paper is written to compare usefulness of mono-Energy images related to radiation dose, iodine content concentration, and various substances, using Spectral CT and Dual energy CT. Material and method: The equipment used in this study is the SIEMENS 192 (384) Channel Dual source SOMATOM Force and the Philips IQon Spectral CT. The phantom used in this experiment is Tissue Characterization Phantom (Gammex467) which represents tissue equivalent material. In the same circumstance for both equipment, helical scan was performed with increased CTDIvol such as 20 mGy, 30 mGy, 40 mGy. Also, Phantom for comparison according to contrast agent concentration was prepared by mixing 2.5 mgI/mL, 5 mgI/mL and 7 mgI/mL, 10 mgI/mL 15 mgI/mL of each iodine with normal saline to have 50 ml of total volume. The Tissue Characterization Phantom and the phantom for contrast agent comparison were scanned by the equipment from SIEMENS and Philips. This study evaluated Hounsfield Unit (HU) values obtained from them on monoE image sat from 40 keV to 100 keV. Result: When the tissue phantom and the contrast agent Phantom were examined by CTDIvol changes, HU values at the level of various monoE[keV] were not significantly changed. Also, the similar results was obtained from using both equipment. As the level of monoE[keV] increased from40 keV to 100 keV, the substances with lower CT number such as water and liver showed less variation of HU values than other tissues. However, comparing iodine, CB2 Resin-30 % CaCO3 and CB2 Resin-50 % CaCO3, the results of HU values significantly changed, as the level of monoE[keV] increased from 40 keV to 100 keV with both equipment. Conclusion: HU values obtained from various monoE[keV] images in Dual energy CT and Spectral CT indicated almost same. In the clinical applications, the use of monoE[keV] images is expected to broaden the range of diagnosis by helping to detect the differences between soft tissues and substances containing calcium such as stone.