Table 5.

Comparison of the distributions of CTDI_vol and DLP classified in terms of tube voltage used

		CTDIvol (mGy)						DLP (mGy cm)
		n	Median	Mean	CV (%)	Reduction rate (%)	p-value	n	Median	Mean	CV (%)	Reduction rate (%)	p-value
Adults		Head without contrast agent						Head without contrast agent
	kV <120	7	42.0	47.4	30.8	37.0	p < 0.05	7	740.0	876.1	37.2	24.2	p = 0.28
	kV ≥120	691	70.1	75.2	38.4			695	1100.0	1155.1	59.4
		Head CT angiography with contrast agent						Head CT angiography with contrast agent
	kV <120	41	32.0	46.0	99.3	55.1	p < 0.05	42	547.3	658.8	67.2	40.2	p < 0.05
	kV ≥120	251	54.0	102.5	149.5			252	889.5	1101.0	69.2
		Chest without contrast agent						Chest without contrast agent
	kV <120	10	8.9	8.5	32.3	29.1	p < 0.05	10	325.0	340.1	37.6	21.6	p = 0.12
	kV ≥120	440	10.1	12.0	76.6			442	400.0	434.0	44.3
		Chest with contrast agent (tumour)						Chest with contrast agent (tumour)
	kV <120	20	9.3	19.2	138.7	−32.4	p = 0.45	20	405.7	568.0	93.5	5.6	p = 0.73
	kV ≥120	296	11.5	14.5	85.2			298	478.3	601.8	68.3
		Abdomen and pelvis without contrast agent						Abdomen and pelvis without contrast agent
	kV <120	12	9.0	9.6	38.7	36.8	p < 0.05	12	445.0	497.8	35.8	30.8	p < 0.05
	kV ≥120	417	13.9	15.3	48.1			419	652.3	719.1	49.8
		Abdomen and pelvis with contrast agent (acute abdomen)						Abdomen and pelvis with contrast agent (acute abdomen)
	kV <120	19	9.9	11.2	49.5	54.2	p < 0.05	19	450.0	554.4	69.1	48.2	p < 0.05
	kV ≥120	322	15.6	24.5	132.7			325	850.9	1070.9	75.3
		Coronary artery without contrast agent						Coronary artery without contrast agent
	kV <120	7	5.2	9.1	89.8	11.5	p = 0.85	7	62.8	219.2	144.4	−12.3	p = 0.86
	kV ≥120	202	5.6	10.2	154.5			202	88.0	195.3	175.0
		Coronary artery with contrast agent						Coronary artery with contrast agent
	kV <120	35	34.0	36.2	74.1	53.8	p < 0.05	35	492.0	516.0	77.6	49.0	p < 0.05
	kV ≥120	256	57.4	78.3	100.6			256	921.9	1011.8	68.3
		Chest and pelvis without contrast agent						Chest and pelvis without contrast agent
	kV <120	10	10.5	10.4	17.1	29.4	p < 0.05	10	781.4	761.8	24.9	20.5	p < 0.05
	kV ≥120	407	13.0	14.8	47.8			409	884.0	958.6	38.9
		Liver with non-contrast and contrast agent						Liver with non-contrast and contrast agent
	kV <120	16	10.7	19.4	85.6	59.7	p < 0.05	16	459.0	736.8	73.6	55.4	p < 0.05
	kV ≥120	330	17.7	48.0	175.2			335	1054.9	1653.6	250.2
		Whole-body without contrast agent (trauma)						Whole-body without contrast agent (trauma)
	kV <120	5	11.6	12.2	27.6	54.1	p < 0.05	5	1000.0	952.4	27.1	44.8	p < 0.05
	kV ≥120	136	14.5	26.6	110.2			137	1162.0	1725.8	173.2
Children (5 years)		Head without contrast agent						Head without contrast agent
	kV <120	35	29.8	29.8	40.3	30.4	p < 0.05	36	476.5	466.0	38.0	24.7	p < 0.05
	kV ≥120	298	39.3	42.9	55.6			300	596.6	618.6	50.4
		Head (non-helical) without contrast agent						Head (non-helical) without contrast agent
	kV <120	14	25.0	28.2	54.6	37.2	p < 0.05	14	435.0	405.8	47.6	21.5	p = 0.14
	kV ≥120	142	40.6	44.8	61.6			142	490.0	516.7	53.9
		Head (helical) without contrast agent						Head (helical) without contrast agent
	kV <120	21	30.5	30.9	28.4	24.7	p < 0.05	21	550.0	509.1	30.5	28.5	p < 0.05
	kV ≥120	156	38.3	41.1	48.0			157	663.8	711.5	44.0
		Head with contrast material (tumour)						Head with contrast material (tumour)
	kV <120	12	30.9	31.9	22.9	26.8	p < 0.05	12	524.5	555.0	54.9	23.7	p = 0.24
	kV ≥120	86	37.8	43.5	62.4			86	610.6	727.8	67.4
		Chest without contrast agent						Chest without contrast agent
	kV <120	46	3.5	5.9	213.9	24.4	p = 0.33	46	99.6	140.1	147.3	28.6	p = 0.10
	kV ≥120	99	5.7	7.8	69.2			101	160.0	196.2	74.8
		Chest with contrast agent (tumour)						Chest with contrast agent (tumour)
	kV <120	32	3.6	5.0	68.6	29.0	p < 0.05	32	114.6	132.1	60.8	33.3	p < 0.05
	kV ≥120	66	6.0	7.1	58.9			66	157.9	198.0	68.9
		Abdomen and pelvis without contrast agent						Abdomen and pelvis without contrast agent
	kV <120	47	4.6	7.3	172.3	21.1	p = 0.32	47	139.4	211.3	103.6	23.8	p = 0.06
	kV ≥120	103	7.0	9.2	70.2			107	240.0	277.3	69.8
		Abdomen and pelvis with contrast agent (acute abdomen)						Abdomen and pelvis with contrast agent (acute abdomen)
	kV <120	43	4.0	6.2	96.7	46.3	p < 0.05	43	151.8	215.6	75.2	47.8	p < 0.05
	kV ≥120	77	9.2	11.6	99.9			77	300.5	413.2	95.0

CTDI_vol, volume CT dose index; DLP, dose–length product;

n indicates the number of CTDI_vol or DLP values.