181982937-Clark-s-Pocket-Handbook-For-Radiographers-pdf (1)

Radiation Protection
Table 1.1 Radiation dose quantities
Dose quantities Unit Definition
Absorbed dose Gy Energy absorbed in a known mass of
tissue
Organ dose mGy Average dose to specific tissue
Effective dose mSv Overall dose weighted for sensitivity
of different organs; indicates risk
Entrance surface dose mGy Dose measured at beam entrance
surface; used to monitor doses and
set DRLs for radiographs
Dose–area product Gy per cm 2 Product of dose (in air) and beam
area; used to monitor doses and set
DRLs for examinations
DRL, dose reference level.
Table 2.2 Radiations risk for X-ray examinations to an average adult
Examination
Typical effective
dose (mSv)
Risk*
Hand/foot 0.01 1 in a few million
Chest 0.02 1 in 1000000
Mammography 0.06 1 in 300000
Abdomen 0.7 1 in 30000
Lumbar spine 1.3 1 in 15000
CT head 2 1 in 10000
Barium enema 7.2 1 in 2800
CT body 9 1 in 2200
*Additional lifetime risk of fatal cancer.
CT, computed tomography.
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