AJR:204, June 2015 W677 visceral fat area is CT [10, 11]. MRI can be also used to assess abdominal fat distribution [11, 12]; however, the use of MRI is limited by its poor accessibility and high cost as com- pared with CT [10]. Providing excellent reso- lution for adipose tissue, CT represents a di- rect method for assessing the visceral fat deposition in both adult and pediatric popula- tions [10]. On the other hand, the exposure to ionizing radiation limits its broad application in healthy subjects given that the widespread use of CT around the world has raised concern about the increase in the risk of cancer from medical radiation exposure [13]. Because ra- diation-induced carcinogenesis is a stochastic effect, the risk may be expected to decrease with a decrease of the radiation dose. Several approaches have been attempted to reduce the radiation dose to patients dur- CT Dose Reduction for Visceral Adipose Tissue Measurement: Effects of Model-Based and Adaptive Statistical Iterative Reconstructions and Filtered Back Projection Yoshitake Yamada 1 Masahiro Jinzaki 1 Yuki Niijima 1 Masahiro Hashimoto 1 Minoru Yamada 2 Takayuki Abe 3 Sachio Kuribayashi 1 Yamada Y, Jinzaki M, Niijima Y, et al. 1 Department of Diagnostic Radiology, Keio University School of Medicine, 35 Shinanomachi, Shinjuku-ku, Tokyo 160-8582, Japan. Address correspondence to M. Jinzaki (jinzaki@rad.Medicinekeio.ac.jp). 2 Multidimension Biomedical Imaging & Information Laboratory in Research Park, Keio University School of Medicine, Tokyo, Japan. 3 Department of Preventive Medicine and Public Health, Center for Clinical Research, Keio University School of Medicine, Tokyo, Japan. Medical Physics and Informatics • Original Research WEB This is a web exclusive article. AJR 2015; 204:W677–W683 0361–803X/15/2046–W677 © American Roentgen Ray Society B ody fat tissue is traditionally dis- tributed in two main compart- ments with different metabolic characteristics: the visceral adi- pose tissue and subcutaneous adipose tissue. Several studies have implicated abdominal visceral adipose tissue in the development of various metabolic abnormalities [1]; coro- nary artery disease [2, 3]; and cancers of the colon [4], breast [5], and prostate [6]. In ad- dition, investigators have reported associa- tions between abdominal visceral adipose tissue and coronary artery calcium score [7]; systemic markers of inflammation [8]; and predisposition to infections and noninfec- tious complications, greater length of hospi- tal stay, and higher hospital mortality [9]. The reference standard modality for the quantitative measurement of the abdominal Keywords: abdomen, intraabdominal fat, MDCT, radiation dose DOI:10.2214/AJR.14.13411 Received July 3, 2014; accepted after revision October 7, 2014. M. Jinzaki and S. Kuribayashi received a research grant from GE Healthcare Japan. The remaining authors had complete unrestricted access to the study data at all stages of the study. Supported in part by the Japan Society for the Promotion of Science (JSPS KAKENHI grant no. 26861016). OBJECTIVE. The objective of our study was to evaluate the effects of radiation dose re- duction and the reconstruction algorithm used—filtered back projection (FBP), adaptive sta- tistical iterative reconstruction (ASIR), or model-based iterative reconstruction (MBIR)—on the measurement of abdominal visceral fat using CT. SUBJECTS AND METHODS. Standard-dose and low-dose abdominal CT exami- nations were performed simultaneously with automatic exposure control in 59 patients; the noise index for a 5-mm slice thickness was 12 for routine-dose CT and 24 for low-dose CT. The routine-dose CT images were reconstructed using FBP (reference standard), and the low-dose CT images were reconstructed using FBP, ASIR (so-called hybrid iterative recon- struction [IR]), and MBIR (so-called pure IR). In the 236 image series obtained, the visceral fat area was measured. Data were analyzed by the Pearson correlation coefficient test and a Bland-Altman difference analysis. RESULTS. The radiation dose of the low-dose abdominal CT examinations was 73.0% (mean) lower than that of routine-dose CT examinations. Excellent correlations were ob- served between the visceral fat areas measured on the routine-dose FBP images and those measured on the low-dose FBP, low-dose ASIR, and low-dose MBIR images (r = 0.998, 0.998, and 0.998, respectively; p < 0.001). A Bland-Altman difference analysis revealed ex- cellent agreements, with mean biases of –0.47, –0.41, and 0.18 cm 2 for the visceral fat area between the routine-dose FBP images and the low-dose FBP, low-dose ASIR, and low-dose MBIR images, respectively. CONCLUSION. A 73.0% reduction of the radiation dose would be possible in CT for the measurement of the abdominal visceral fat regardless of which reconstruction algorithm is used (i.e., FBP, hybrid IR, or pure IR). Yamada et al. CT Dose Reduction for Intraabdominal Fat Measurement Medical Physics and Informatics Original Research Downloaded from www.ajronline.org by 52.73.204.196 on 05/16/22 from IP address 52.73.204.196. Copyright ARRS. For personal use only; all rights reserved