Optimal scan delays for multiphasic renal multidetector row computed tomography performed with fixed injection duration of contrast medium.
OBJECTIVE
The purpose of our study was to prospectively determine optimal scan delays for multiphasic imaging of the kidney performed with multidetector row computed tomography (CT) and fixed injection duration of intravenous contrast medium.


METHODS
One hundred ninety-eight patients underwent 3-phase CT of the kidney with 8-slice CT after receiving 2 mL/kg of an intravenous contrast medium of 300 mg I/mL for a fixed duration of 30 seconds. The patients were prospectively randomized into 4 groups according to different scan delays from the start of injection: group 1 (25, 45, 65 seconds), group 2 (30, 50, 70 seconds), group 3 (35, 55, 75 seconds), and group 4 (40, 60, 80 sec). Mean CT values (Hounsfield units [HU]) of the abdominal aorta, renal arteries, veins, cortexes, and medulla were measured. Increases in CT values from precontrast to postcontrast CT (deltaHU) and renal artery-to-vein and renal cortex-to-medulla differential contrasts (deltaHU) were assessed. Qualitative analysis was also performed.


RESULTS
Abdominal aorta and renal artery enhancements peaked at 35 seconds (305 DeltaHU; 253 DeltaHU) after injection start, and renal veins peaked at 45 seconds (196 DeltaHU). Renal cortexes peaked at 40 seconds (197 DeltaHU), and renal medullae peaked at 75 seconds (152 DeltaHU). Renal artery-to-vein differential contrasts were high (95-137 deltaHU) at 25 to 30 seconds, and cortex-to-medulla contrasts were high (79-130 deltaHU) at 30 to 55 seconds and then decreased to less than 10 deltaHU at 75 seconds. Qualitative results were in good agreement with quantitative results.


CONCLUSIONS
With a fixed 30-second injection, estimated optimal scan delays for multiphasic imaging the kidney were, from the start of injection, 25 to 30 seconds for renal arterial CT angiography, 35 to 45 seconds for the corticomedullary, and 75 seconds for the nephrographic phase.
Tsuge
Yusuke
Y
Department of Radiology, Gifu University School of Medicine, Gifu University Hospital, Gifu, Japan. yusuke@gifu-u.ac.jp
Kanematsu
Masayuki
M
Goshima
Satoshi
S
Kondo
Hiroshi
H
Hoshi
Hiroaki
H
Yokoyama
Ryujiro
R
Miyoshi
Toshiharu
T
Onozuka
Minoru
M
Moriyama
Noriyuki
N
Bae
Kyongtae T
KT
D000368:Aged; D000369:Aged, 80 and over; D003287:Contrast Media / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D007267:Injections / Q000379:methods; D007472:Iohexol / Q000008:administration & dosage*; D007668:Kidney / Q000000981:diagnostic imaging*; D007674:Kidney Diseases / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011856:Radiographic Image Enhancement / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*
D003287:Contrast Media; D007472:Iohexol