Examination type		Estimated fetal dose per examination (rad)*	Number of examinations required for a cumulative 5-rad dose†
Plain films
Skull4		0.004	1,250
Dental5		0.0001	50,000
Cervical spine4		0.002	2,500
Upper or lower extremity4		0.001	5,000
Chest (two views)6		0.00007	71,429
Mammogram6		0.020	250
Abdominal (multiple views)6		0.245	20
Thoracic spine4		0.009	555
Lumbosacral spine6		0.359	13
Intravenous pyelogram6		1.398	3
Pelvis4		0.040	125
Hip (single view)6		0.213	23
CT scans (slice thickness: 10 mm)
Head (10 slices)6		< 0.050	> 100
Chest (10 slices)6		< 0.100	> 50
Abdomen (10 slices)6		2.600	1
Lumbar spine (5 slices)6		3.500	1
Pelvimetry (1 slice with scout film)6		0.250	20
Fluoroscopic studies
Upper GI series6		0.056	89
Barium swallow6		0.006	833
Barium enema6		3.986	1
Nuclear medicine studies
Most studies using technetium (99mTc)7		< 0.500	> 10
Hepatobiliary technetium HIDA scan6		0.150	33
Ventilation-perfusion scan (total)		0.215	23
	• Perfusion portion: technetium6	0.175	28
	• Ventilation portion: xenon (133Xe)6	0.040	125
Iodine (131I), at fetal thyroid tissue6		590.000	‡
Environmental sources (for comparison)
Environmental background radiation (cumulative dose over nine months)8		0.100	N/A