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


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. CTDI(vol) 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). CTDI(vol) values were positively correlated with patient body weight (r = 0.34, P < .001) but had no correlation with collimation size (P = .24).


CONCLUSIONS
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. CTDI(vol) values correlate positively with body weight but have no correlation with collimation size.
Miyoshi
Toshiharu
T
Radiology Services, Gifu University Hospital, 1-1 Yanagido, 501-1194 Gifu, Japan.
Kanematsu
Masayuki
M
Kondo
Hiroshi
H
Goshima
Satoshi
S
Tsuge
Yusuke
Y
Hatcho
Atsushi
A
Shiratori
Yoshimune
Y
Onozuka
Minoru
M
Moriyama
Noriyuki
N
Bae
Kyongtae T
KT
D000005:Abdomen / Q000098:blood supply*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000792:Angiography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011829:Radiation Dosage; D013152:Splanchnic Circulation; D014057:Tomography, X-Ray Computed / Q000379:methods*