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 Collimation

doi:10.1148/radiol.2483071007

HOME

HELP

FEEDBACK

SUBSCRIPTIONS

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 computedtomographic (CT) dose index (CTDI_vol) of 16-detector CT angiogramsof the abdomen acquired with 0.625-mm collimation with those of imagesacquired with 1.25-mm collimation.

Materials and Methods: This study had institutional review boardapproval, and informed consent was obtained from all patients. Dual-phasecontrast 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 randomizedinto two equal-sized groups: those who underwent CT with 0.625-mmcollimation and nonoverlapped reconstruction and those who underwentCT with 1.25-mm collimation and 50% overlapped reconstruction. Scanacquisition time was 7.5 seconds in both groups. CTDI_vol was recorded.Arterial phase volume-rendered, arterial phase multiplanar reformatted,and portal venous phase multiplanar reformatted CT angiograms weregenerated. Qualitative assessment was performed for image qualityand for depiction of splanchnic, intercostal, and lumbar arteriesand veins. The unpaired t test was used for statistical comparison.

Results: On the arterial phase CT angiograms, there was no differencebetween the two collimation groups for the depiction of proximalsplanchnic arteries, while the dorsal pancreatic, intercostal, andlumbar arteries and some peripheral splanchnic arterial brancheswere better delineated on CT scans obtained with 0.625-mm collimationthan on scans obtained with 1.25-mm collimation (P < .05). Regardingthe portal venous phase CT angiograms, no difference between thetwo groups was found in most veins, except the right adrenal vein(P = .003). Image quality was superior for 1.25-mm collimation (P< .001). CTDI_vol values were positively correlated with patientbody weight (r = 0.34, P < .001) but had no correlation with collimationsize (P = .24).

Conclusion: Scanning with 1.25-mm collimation seems adequate fora routine CT angiography examination of most arteries and veins at16-detector CT, while scanning with 0.625-mm collimation facilitatesimproved delineation of fine vessels. CTDI_vol values correlate positivelywith body weight but have no correlation with collimation size.