Table 1.

Dataset of CTDI_vol and DLP values and estimated EDs.

	Group 1			Group 2 - Sequential scan			Group 3 - Helical scan
	CT Philips	CT GE	T-test	CT Philips	CT GE	T-test	CT Philips	CT GE	T-test
Scan parameters
Tube voltage (kV)				120	120		120	120
Tube current				378 mAs (432 mA)	350 mA		423 mAs (299 mA)	80-300 (smart mA)
Slice thickness (mm)				1.25	1.25		1	1.25
Rotation time (s)				0.75	1		0.4	0.5
Pitch				–	–		0.399	0.516:1
Strength of IR				Level 3	60 %		Level 4	50 %
Number of patients	100	100		50	50		20	20
ED (mSv)
min	1.76	1.21		1.76	1.33		2.46	1.66
max	2.84	2.14		2.84	2.14		2.84	2.06
mean (SD)	2.09 (0.31)	1.74 (0.28)	p < 0.01a	1.99 (0.17)	1.98 (0.15)	p=0.15	2.63 (0.11)	1.81 (0.15)	p < 0.01a
median	1.89	1.76		2.01	1.95		2.64	1.79
DLP (mGy.cm)
min	840.2	574.52		840.2	631.48		1172	656.61
max	1353	1017.66		1353	1017.7		1353	979.63
mean(SD)	993.28 (146.18)	828.14 (130.06)	p < 0.01a	949.42 (80.87)	942.13 (73.05)	p=0.64	1252.2 (52.11)	859.66 (72.04)	p < 0.01a
median	900.55	839.43		959.1	928.56		1255	850.24
third quartile	1019.75	928.52		960	1017.57		1291.75	901.41
CTDIvol(mGy)
min	54.6	29.27		56.2	35.08		54.6	32.91
max	71.9	59.96		71.9	59.96		54.6	41.12
mean (SD)	57.61 (2.89)	43.66 (11.15)	p < 0.01a	58.63 (3.33)	57.25 (3.4)	p < 0.05a	54.6 (0.0)	37.18 (2.52)	p < 0.01a
median	57.4	37.8		58	58.03		54.6	37.78
third quartile	58.6	56.54		58.93	58.03		54.6	39.29

^aStatistically significant.