Computed tomography and patient risk: Facts, perceptions and uncertainties

Table 1 Doses of common radiological procedures

Examination	Average effective dose (mSv)	Values reported in literature
Posterioranterior study of chest	0.02	0.007-0.05
Head CT	2	0.9-4.0
Thorax CT	7	4.0-18.0
CT Pulmonary angiogram	15	13.0-40.0
Abdomen CT	8	3.5-25
Pelvic CT	6	3.3-10
Coronary angiography	16	5.0-32

Annual effective dose from natural background radiation = 3 mSv. CT: Computed tomography.

Table 2 Methods to try to optimise dose delivered during computed tomography scanning[3]

Current dose reductionstrategies in CT scanning	Dose reduction strategies gaining interest[92]
Solid state scintillating detectors	Manual/automated adjustment of scanner output according to patient size via: Tube current modulation; Selection of the most dose-efficient tube potential
Electronic circuits with lower levels of background noise	Iterative reconstruction methods
Multi-detector row arrays	Increased spiral pitch or non-spiral methods in cardiac CT
More powerful X-ray tubes and generators
Beam shaping filters which vary the X-ray intensity across the patient cross section

CT: Computed tomography.