Radiation dose measurements in coronary CT angiography

Table 1 Radiation weighting factor for various type and energy range

Type and energy range	Radiation weighting factor, WR (ICRP-60)
Photons, all energy	1
Electrons, muons, all energy	1
Neutrons < 10 keV	5
10 eV-100 keV	10
> 100 keV-2MeV	20
> 2–20 MeV	10
> 20 MeV	5
Protons > 2 MeV	5
Alpha particles, fission fragments and heavy nuclei	20

Adapted from Ng et al[7]. ICRP: International Commission on Radiological Protection.

Table 2 Tissue weighting factor comparison between International Commission on Radiological Protection publication-103 and publication-60

Organs	Tissue weighting factor, WT
	ICRP-103	ICRP-60
Colon	0.12	0.12
Lung	0.12	0.12
Red bone marrow	0.12	0.12
Stomach	0.12	0.12
Breast	0.12	0.05
Gonads	0.08	0.20
Bladder	0.04	0.05
Liver/Oesophagus	0.04	0.05
Thyroid	0.04	0.05
Bone surface/skin	0.01	0.01
Brain	0.01	-
Salivary glands	0.01	-
Remainder tissues	0.121	0.052

Adapted from Ng et al[7].

¹Remainder tissues in International Commission on Radiological Protection (ICRP)-103: adrenals, kidneys, muscle, small intestine, pancreas, spleen, thymus, uterus/cervix, prostate, extra-thoracic region, gallbladder, heart, lymphatic nodes and oral mucosa;

²Remainder tissues in ICRP-60: adrenals, kidney, muscle, small intestine, pancreas, spleen, thymus, uterus, upper large intestine and brain.

Table 3 Estimated effective doses for diagnostic medical exposures associated with background equivalent radiation time and lifetime fatal cancer risks from National Radiological Protection Board

X-ray examination	Estimated effective dose (mSv)	BERT1	Fatal cancer risk per examination2
Limbs and joints (exclude hip)	< 0.01	< 1 d	1 in a few millions
Dental (single bitewing)	< 0.01	< 1.5 d	1 in a few millions
Dental (panoramic)	0.01	1.5 d	1 in 2 million
Chest (single PA)	0.02	3 d	1 in a million
Skull	0.07	1 d	1 in 300000
Cervical spine	0.08	2 wk	1 in 200000
Thoracic spine	0.7	4 mo	1 in 30000
Lumbar spine	1.3	7 mo	1 in 15000
Abdomen	0.7	4 mo	1 in 30000
Hip	0.3	7 wk	1 in 67000
Pelvis	0.7	4 mo	1 in 30000
Intravenous urography	2.5	14 mo	1 in 8000
Barium swallow	1.5	8 mo	1 in 13000
Barium meal	3	16 mo	1 in 6700
Barium follow-through	3	16 mo	1 in 6700
Barium enema	7	3.2 yr	1 in 3000
CT head	2	1 yr	1 in 10000
CT chest	8	3.6 yr	1 in 2500
CT abdomen/pelvis	10	4.5 yr	1 in 2000

Adapted from Ng et al[7].

¹Natural background radiation based on Australia average = 2.4 mSv per year;

²Appropriate lifetime risk for patients from 16-69 years old: paediatric = 2x; geriatric = 5x. BERT: Background equivalent radiation time.