Table 1.

List of exposure parameters and reconstruction techniques used in the reference and ultra-low-dose test protocols

Exposure protocol	Reconstruction technique	Matrix	In-plane voxel size (mm)	kV	mA	Rotation time (s)	Pitch	CTDIvol (mGy)	Effective dose (µSv)a
									Scan length of 5 cm	Scan length of 10 cm
Reference	FBP	512 × 512	0.391	120	100	1.0	0.53	29.4	308.7	617.4
LD1	FBP	512 × 512	0.391	80	10	0.4	0.53	0.53	5.6	11.1
	ASIR 50
	ASIR 100
	MBIR	1024 × 1024	0.195
LD2	FBP	512 × 512	0.391				0.97	0.29	3.0	6.1
	ASIR 50
	ASIR 100
	MBIR	1024 × 1024	0.195

CTDIvol volume CT dose index, LD low-dose protocol, FBP filtered back-projection, ASIR adaptive statistical iterative reconstruction, MBIR model-based iterative reconstruction

^aCalculated from the dose–length product based upon a k factor of 0.0021