Department of Radiology, Gachon University Gil Medical Center, Incheon 21565, Korea.
Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 06351, Korea.
Korean J Radiol. 2018 Nov-Dec;19(6):1179-1186. doi: 10.3348/kjr.2018.19.6.1179. Epub 2018 Oct 18.
The purposes of this study were to evaluate size-specific dose estimate (SSDE) of low-dose CT (LDCT) in the Korean Lung Cancer Screening (K-LUCAS) project and to determine whether CT protocols from Western countries are appropriate for lung cancer screening in Korea.
For participants (n = 256, four institutions) of K-LUCAS pilot study, volume CT dose index (CTDI) using a 32-cm diameter reference phantom was compared with SSDE, which was recalculated from CTDI using size-dependent conversion factor (f-size) based on the body size, as described in the American Association of Physicists in Medicine Report 204. This comparison was subsequently assessed by body mass index (BMI) levels (underweight/normal vs. overweight/obese), and automatic exposure control (AEC) adaptation (yes/no).
Size-specific dose estimate was higher than CTDI (2.22 ± 0.75 mGy vs. 1.67 ± 0.60 mGy, < 0.001), since the f-size was larger than 1.0 for all participants. The ratio of SSDE to CTDI was higher in lower BMI groups; 1.26, 1.37, 1.43, and 1.53 in the obese (n = 103), overweight (n = 70), normal (n = 75), and underweight (n = 4), respectively. The ratio of SSDE to CTDI was greater in standard-sized participants than in large-sized participants independent of AEC adaptation; with AEC, SSDE/CTDI in large- vs. standard-sized participants: 1.30 ± 0.08 vs. 1.44 ± 0.08 ( < 0.001) and without AEC, 1.32 ± 0.08 vs. 1.42 ± 0.06 ( < 0.001).
Volume CT dose index based on a reference phantom underestimates radiation exposure of LDCT in standard-sized Korean participants. The optimal radiation dose limit needs to be verified for standard-sized Korean participants.
本研究旨在评估韩国肺癌筛查（K-LUCAS）项目中低剂量 CT（LDCT）的大小特异性剂量估计（SSDE），并确定西方国家的 CT 方案是否适用于韩国的肺癌筛查。
对于 K-LUCAS 试点研究的 256 名参与者（来自 4 个机构），使用 32cm 直径参考体模测量容积 CT 剂量指数（CTDI），并与根据美国医学物理学家协会报告 204 中描述的身体大小，使用基于大小的转换系数（f-size）重新计算的 SSDE 进行比较。随后根据体重指数（BMI）水平（消瘦/正常与超重/肥胖）和自动曝光控制（AEC）适应性（是/否）评估这种比较。
SSDE 高于 CTDI（2.22 ± 0.75 mGy 比 1.67 ± 0.60 mGy，<0.001），因为所有参与者的 f-size 均大于 1.0。在 BMI 较低的组中，SSDE 与 CTDI 的比值更高；肥胖组（n = 103）为 1.26，超重组（n = 70）为 1.37，正常组（n = 75）为 1.43，消瘦组（n = 4）为 1.53。独立于 AEC 适应性，标准体型参与者的 SSDE 与 CTDI 的比值大于体型较大的参与者；有 AEC 时，体型较大的与标准体型参与者的 SSDE/CTDI 比值为 1.30 ± 0.08 比 1.44 ± 0.08（<0.001），无 AEC 时为 1.32 ± 0.08 比 1.42 ± 0.06（<0.001）。
基于参考体模的容积 CTDI 低估了标准体型韩国参与者 LDCT 的辐射暴露。需要为标准体型的韩国参与者验证最佳辐射剂量限值。
