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DOI: 10.1148/radiol.2483071007
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(Radiology 2008;249:142-150.)
© RSNA, 2008

Gastrointestinal Imaging

Abdomen: Angiography with 16-Detector CT—Comparison of Image Quality and Radiation Dose between Studies with 0.625-mm and those with 1.25-mm Collimation1

Toshiharu Miyoshi, RT, Masayuki Kanematsu, MD, Hiroshi Kondo, MD, Satoshi Goshima, MD, Yusuke Tsuge, MD, Atsushi Hatcho, RT, Yoshimune Shiratori, MD, Minoru Onozuka, PhD, Noriyuki Moriyama, MD, and Kyongtae T. Bae, MD, PhD

1 From the Radiology Services (T.M., M.K.), Department of Radiology (M.K., H.K., S.G., Y.T.), and Department of Medical Informatics (Y.S.), Gifu University Hospital, 1-1 Yanagido, 501-1194 Gifu, Japan; Research Center of Brain and Oral Science (M.K., M.O.) and Department of Physiology and Neuroscience (M.O.), Kanagawa Dental College, Yokosuka, Japan; Department of Radiology, Nagano Red Cross Hospital, Nagano, Japan (A.H.); Research Center for Cancer Prevention and Screening, National Cancer Center Hospital, Tsukiji, Japan (N.M.); and Department of Radiology, University of Pittsburgh Medical Center, Pittsburgh, Pa (K.T.B.). Received June 11, 2007; revision requested August 20; revision received September 11; accepted March 11, 2008; final version accepted March 28. Supported in part by the Health and Labour Sciences Research Grants for Third Term Comprehensive Control Research for Cancer, Ministry of Health, Labour and Welfare, Tokyo, Japan. Address correspondence to M.K.

Purpose: To prospectively compare image quality and volume computed tomographic (CT) dose index (CTDIvol) of 16-detector CT angiograms of the abdomen acquired with 0.625-mm collimation with those of images acquired with 1.25-mm collimation.

Materials and Methods: This study had institutional review board approval, and informed consent was obtained from all patients. Dual-phase contrast material–enhanced CT was performed in 78 patients (48 men and 30 women; age, 34–91 years; mean age, 64.8 years) by using a 16-detector CT scanner. Patients were prospectively randomized into two equal-sized groups: those who underwent CT with 0.625-mm collimation and nonoverlapped reconstruction and those who underwent CT with 1.25-mm collimation and 50% overlapped reconstruction. Scan acquisition time was 7.5 seconds in both groups. CTDIvol was recorded. Arterial phase volume-rendered, arterial phase multiplanar reformatted, and portal venous phase multiplanar reformatted CT angiograms were generated. Qualitative assessment was performed for image quality and for depiction of splanchnic, intercostal, and lumbar arteries and veins. The unpaired t test was used for statistical comparison.

Results: On the arterial phase CT angiograms, there was no difference between the two collimation groups for the depiction of proximal splanchnic arteries, while the dorsal pancreatic, intercostal, and lumbar arteries and some peripheral splanchnic arterial branches were better delineated on CT scans obtained with 0.625-mm collimation than on scans obtained with 1.25-mm collimation (P < .05). Regarding the portal venous phase CT angiograms, no difference between the two groups was found in most veins, except the right adrenal vein (P = .003). Image quality was superior for 1.25-mm collimation (P < .001). CTDIvol values were positively correlated with patient body weight (r = 0.34, P < .001) but had no correlation with collimation size (P = .24).

Conclusion: Scanning with 1.25-mm collimation seems adequate for a routine CT angiography examination of most arteries and veins at 16-detector CT, while scanning with 0.625-mm collimation facilitates improved delineation of fine vessels. CTDIvol values correlate positively with body weight but have no correlation with collimation size.

Supplemental material: http://radiology.rsnajnls.org/cgi/content/full/249/1/142/DC1

© RSNA, 2008