Impact of Low-Dose Computed Tomography on Computed Tomography Orders and Scan Length

Curtis Simmons; James Milburn

doi:10.31486/toj.19.0008

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Figure.
Histograms of size-specific dose estimate (SSDE) and computed tomography dose index (CTDI) volume by frequency before and after iterative reconstruction.

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Table 1.

Number of Computed Tomography (CT) Scans in 2013 Based on Aggregated Billing Data

Type	Number of Scans
Head	61,811
Neck	6,089
Chest	41,014
Abdomen^a	8,601
Abdomen/pelvis^a	65,250
Renal stone study^a	1,339
Pelvis	1,316
Spine	13,068
Extremities	3,784
CT-guided study	1,294
CT-angiogram	20,896
Other	15,372
Total	239,834

↵^aAbdomen and abdomen/pelvis scans and renal stone studies were combined for analysis (n=75,190).

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Table 2.

Patient Demographics and Computed Tomography Factors Analyzed Before and After Iterative Reconstruction Presented by Analysis Phase

	Assessment Timepoint
Phase/Variables	Pre-ASIR, July	Post-ASIR, November
Phase 1	n=243	n=233	P-Value
Mean age, years, all patients (range)	52 ± 20 (10-92)	53 ± 20 (4-94)	0.59
Male, n (%)	112 (46)	106 (45)
Male mean age, years (range)	53 ± 18 (10-87)	56 ± 20 (4-89)	0.45
Female, n (%)	131 (54)	127 (55)
Female mean age, years (range)	51 ± 21 (16-92)	51 ± 21 (20-94)	1.0
Mean CTDI_vol, mGy	17.5 ± 5.7	11.0 ± 6.0	<0.001
Mean AP dimension, cm	26.4 ± 5.3	26.1 ± 5.0	0.48
Mean lateral dimension, cm	34.4 ± 4.9	34.3 ± 5.1	0.80
Mean AP+lateral dimensions, cm	60.8 ± 9.8	60.3 ± 9.8	0.62
Mean length of scan, cm	45.1 ± 7.5	43.7 ± 10.4	0.08
Mean SSDE (AP), mGy	20.3 ± 4.6	12.5 ± 5.1	<0.001
Mean SSDE (AP+lateral), mGy	20.8 ± 5.0	12.7 ± 5.1	<0.001
Mean number of phases	1.27 ± 0.60	1.29 ± 0.63	0.79
	Pre-ASIR, July	Post-ASIR, November
Phase 2	n=199	n=184
Mean age, years, all patients (range)	52 ± 20 (10-92)	52 ± 21 (4-94)	1.0
Male, n (%)	90 (45)	84 (46)
Male mean age, years (range)	54 ± 19 (10-87)	53 ± 21 (4-89)	0.74
Female, n (%)	109 (55)	100 (54)
Female mean age, years (range)	50 ± 21 (16-92)	50 ± 21 (20-94)	1.0
Mean number of phases	1.3 ± 0.6	1.3 ± 0.6	0.79
Mean DLP, mGy*cm	1,076 ± 527	715 ± 512	<0.001
	Pre-ASIR, June/July	Post-ASIR, October/November
Phase 3	n=408	n=389

Mean age, years, all patients (range)	52 ± 20 (6-97)	50 ± 21 (4-94)	0.17
Male, n (%)	157 (38)	171 (44)
Male mean age, years (range)	54 ± 19 (10-97)	52 ± 21 (4-93)	0.37
Female, n (%)	251 (62)	218 (56)
Female mean age, years (range)	51 ± 21 (6-93)	49 ± 21 (7-94)	0.31
Mean number of phases	1.2 ± 0.5	1.3 ± 0.6	0.15
Mean DLP, mGy*cm	1,069 ± 634	676 ± 480	<0.001

AP, anterior-posterior; ASIR, adaptive statistical iterative reconstruction; CDTI_vol, computed tomography dose index volume; DLP, dose length product; SSDE, size-specific dose estimate.