Table 2.

CT acquisition and reconstruction parameters

Acquisition Parameter	CT Diagnostic Tasks
	Detection of liver metastases (Contrast-enhanced abdominal CT)	Detection of indeterminate pulmonary nodules (Unenhanced chest CT)	Detection of potential causes of acute neurologic deficit (Unenhanced head CT)
Tube energy (kVp)	Vendor-supplied automatic kV selection	120 kV	120 kV
Tube current setting of routine clinical exam	200 QRM*	70 QRM	250 eff. mAs**
Automatic exposure control	On	On	Off
Axial slice thickness/reconstruction interval (mm)	3/2	1.5/1	5/5
Other reconstruction volumes (slice thickness/reconstruction interval [mm])	Coronal 3/2	Thick maximum intensity projection 10/2.5	N/A
Reconstruction Kernels (FBP/IR)***	B30/I30(2)	B50/I50(2)	H40/J40(2)
Dose levels (as represented by tube current setting) examined by all readers (Top value is routine setting	200 QRM 160 QRM 120 QRM 100 QRM 80 QRM 60 QRM	70 QRM 30 QRM 10 QRM 5 QRM 2.5 QRM -	250 eff. mAs 200 eff. mAs 150 eff. mAs 100 eff. mAs 50 eff. mAs 25 eff. mAs
Dose levels examined by nominal CTDIvol (mGy)	13.5 10.8 8.1 6.8 5.4 4.1	4.7 2.0 0.7 0.3 0.2	38.3 30.6 23.0 15.3 7.7 3.8
Total number of dose/kernel configurations	12	10	12

^*QRM = quality reference effective mAs, the setting for the CT system automatic exposure control, that delivers equivalent image quality at a given setting across patients of different sizes

^**eff. mAs = effective milli-ampere second

^***FBP = filtered backprojection; IR = iterative reconstruction