How much radiation do you use?

Question 1

dose units

Answer 1

radiation absorbed dose (D)
equivalent dose (H)
effective dose (E)

Question 2

radiation absorbed dose (D)

Answer 2

amount of energy absorbed from the radiation beam per unit mass of tissue
unit - gray measured in joules per kg

Question 3

equivalent dose (H)

Answer 3

measures radiobiological effectiveness of different types of radiation
unit - sievert
equivalent dose = radiation absorbed dose x radiation quality weighting factor

Question 4

effective dose

Answer 4

allows doses from different investigations of different parts of the body to be compared by converting all doses to an equivalent whole body dose

effective dose = equivalent dose x tissue weighting factor (Wt)

unit - sievert

Question 5

what are effective doses for dental radiology

Answer 5

0.008-0.001 mSV

why is there a range?
dose varies with equipment

Question 6

reference dose

Answer 6

published max absorbed dose for every investigation

set by health protection

Question 7

radiation dose limits

Answer 7

principles :

1. no practice is adopted unless there is net positive benefit
2. all exposure should be kept as low as possible
3. equivalent dose should not exceed limits recommended

Question 8

radiology patient groups

Answer 8

1. examination directly associated with illness - no set dose limit
2. systematic examinations
3. occupational medicolwegal or insurance purposes
4. medical research

Question 9

radiation workers

Answer 9

non classified - dental 6msv a year
classified - power plant workers 20msv a year

ionising radiation regulations

Question 10

personal monitoring devices

Answer 10

TLD film badge

electronic personal dose meter

Question 11

natural background radiation dose

Answer 11

average 2.6 msv

average periodical is equivalent to 16 hours of background radiation

Question 12

what is the risk probability

Answer 12

traditional d speed intra oral film - 1 fatal in 2 million

modern 70kv fast e speed - 1 in 20 million

Question 13

how many films in uk a year?

Answer 13

intraoral around 25 million

panoramic 3 million

Question 14

genetic stochastic risk?

Answer 14

1 congenital abnormality every 3 years