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Korean J Radiol. 2018 Nov-Dec;19(6):1179-1186. doi: 10.3348/kjr.2018.19.6.1179. Epub 2018 Oct 18.

Size-Specific Dose Estimation In the Korean Lung Cancer Screening Project: Does a 32-cm Diameter Phantom Represent a Standard-Sized Patient in Korean Population?

Author information

1
Department of Radiology, Gachon University Gil Medical Center, Incheon 21565, Korea.
2
Department of Radiology and Center for Imaging Science, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 06351, Korea.
3
Department of Radiology, Seoul National University College of Medicine, Seoul 03080, Korea.
4
Department of Diagnostic Radiology, National Cancer Center, Goyang 10408, Korea.
5
Department of Radiology, Pusan National University School of Medicine and Medical Research Institute, Pusan National University Hospital, Busan 49241, Korea.
6
Department of Radiology, Chungbuk National University Hospital, Cheongju 28644, Korea.
7
Cancer Early Detection Branch, National Cancer Control Institute, National Cancer Center, Goyang 10408, Korea.

Abstract

Objective:

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.

Materials and Methods:

For participants (n = 256, four institutions) of K-LUCAS pilot study, volume CT dose index (CTDIvol) using a 32-cm diameter reference phantom was compared with SSDE, which was recalculated from CTDIvol 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).

Results:

Size-specific dose estimate was higher than CTDIvol (2.22 ± 0.75 mGy vs. 1.67 ± 0.60 mGy, p < 0.001), since the f-size was larger than 1.0 for all participants. The ratio of SSDE to CTDIvol 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 CTDIvol was greater in standard-sized participants than in large-sized participants independent of AEC adaptation; with AEC, SSDE/CTDIvol in large- vs. standard-sized participants: 1.30 ± 0.08 vs. 1.44 ± 0.08 (p < 0.001) and without AEC, 1.32 ± 0.08 vs. 1.42 ± 0.06 (p < 0.001).

Conclusion:

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.

KEYWORDS:

Early detection; Low-dose CT; Radiation dosage; Radiation dose

PMID:
30386149
PMCID:
PMC6201978
DOI:
10.3348/kjr.2018.19.6.1179
[Indexed for MEDLINE]
Free PMC Article

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