Abdominal MDCT Standard-Dose Protocols Used in the Prospective Trial

	Protocol
Parameter	IV Contrast Enhanced	Urolithiasis	Supine CT Colonography
Scanner	Discovery CT750 HDa	Discovery CT750 HDa	Discovery CT750 HDa
Scan type	Helical	Helical	Helical
Rotation time (s)	0.5	0.8	0.5
Beam collimation (mm)	40	40	40
No. of detector rows	64	64	64
Pitch	0.516	0.516	0.984
Speed (mm/rotation)	20.64	20.64	39.36
Detector configuration	64 × 0.625	64 × 0.625	64 × 0.625
Slice thickness for noise index (mm)	1.25	1.25	1.25
Scan FOV	Large body	Large body	Large body
Peak kilovoltage	120	120	120
Smart mA (GE Healthcare) range (mA)	60–660	40–660	30–300
Noise index	24	28	50
Reconstruction (filtered back projection)
Displayed FOV (cm)	36–50	36–50	36–50
Reconstruction type	Standard	Standard	Standard
Window width/level (HU)	400/50	400/50	400/50
Reconstruction option	Plus	Plus	Plus
Slice thickness (mm)	2.5	2.5	2.5
Interval (mm)	1.5	1.5	1.5

Note—The protocols considered standard dose in this study are based on use of 40% adaptive statistical iterative reconstruction, which affects the relative dose reduction seen at low dose. The specific protocol for the accompanying low-dose series was derived by adjusting the noise index–slice thickness pairing (and tube current range) to allow targeted 70–90% dose reduction (by projected dose-length product) relative to the standard-dose series.

^aGE Healthcare.