Table 3.

Chest diagnostic/screening X-ray exposure characteristics by medical procedures

Characteristicsa	Cases N = 1552		Controls N = 1363
	No.	%	No.	%
Conventional radiography + fluoroscopy
Never	213	13.7	242	17.8
Ever	1,296	83.5	1,097	80.5
Missing	43	2.8	24	1.8
Number of lifetime exposures
1–3	377	24.3	379	27.8
4–9	248	16.0	195	14.3
≥10	258	16.6	213	15.6
Missing	456	29.4	334	24.5
Age at first exposure (years)
Mean (sd)	20.4 (10.9)		22.0 (12.5)
Missing	291	18.8	202	14.8
Tomography
Never	1,389	89.5	1,276	93.6
Ever	48	3.1	40	2.9
Missing	115	7.4	47	3.5
Number of lifetime exposures
1	37	2.4	30	2.2
≥2	9	0.6	9	0.7
Missing	117	7.5	48	3.5
Age at first exposure (years)
Mean (sd)	40.0 (15.8)		42.8 (15.4)
Missing	115	7.4	47	3.5
Scintigraphy
Never	1,416	91.2	1,294	94.9
Ever	21	1.4	22	1.6
Missing	115	7.4	47	3.5
Number of lifetime exposures
1	18	1.2	18	1.3
≥2	3	0.2	4	0.3
Missing	115	7.4	47	3.5
Age at first exposure (years)
Mean (sd)	50.8 (10.2)		53.4 (12.0)
Missing	115	7.4	47	3.5
Mammography
Never	266	17.1	102	7.5
Ever	1271	81.9	1252	91.9
Missing	15	1.0	9	0.7

^a Lifetime exposures up to one year prior to diagnosis for cases and up to one year prior to date of questionnaire completion for controls