Lecture 25 - Radiation Safety

Question 1

Ionising radiation

Answer 1

• radiation removes electrons from atoms to form ions

- can be carcinogenic, leukemogenci, mutagenic ot teratogenic

Question 2

Non ionising radiation

Answer 2

• radiation energy cannot create ions but can have other effects such as thermal or photochemical
• not carcinogenic

Question 3

Alpha particles

Answer 3

• nasty and dangerous

- not used except for some radioisotype therapy

Question 4

Beta particles

Answer 4

• same as electrons
  Nasty
• used for therapy

Question 5

Gamma rays

Answer 5

• electromagnetic radiation
• penetrating
• not as nasty as particles
• safe for imaging but at high intensities can also be used for therapy

Question 6

X rays

Answer 6

• physicall identical to gamma rays but come from electron, not nucleus
• penetrating -> used for imaging
• relatively safe for imaging
• used for radiotherapy at high intensity

Question 7

Appliation of ionising radiation

Answer 7

• radiology - x ray
• nucleuar medicine: radionuclides
• radiotherapy - X ray, particles and radionuclides
• dental
• radio-labelling techniques: radionuclide
• blood irradiation - gamma rays

Question 8

Non ionising radiation appliation

Answer 8

• MRI
• UV therapy
• lasers” high and low power

Question 9

Radiation dose units

Answer 9

• absorbed dose: gray Gy

- effective dose: Sievert SV

Question 10

Physical effect of radiation

Answer 10

• energy absorption, ionisation

Question 11

Physico-chemical effect of radiation

Answer 11

• interaction of ions with molecules, formation of free radicals

Question 12

Chemical effect of radiation

Answer 12

• interaction of free radicals with molecules, cells and DNA

Question 13

Biological effect of radiaiton

Answer 13

• cell death, change in genetic data in cell, mutations

Question 14

3 types of radiation effect

Answer 14

• Stochastic: probability of effect related to dose
• DEterministic: threshold for effect: no effect below, above, certaintiy and severity increases with dose
• hereditary (genetic)

Question 15

Eg of stochastic effect

Answer 15

• DNA effects, mainly repaired

- carcinogenesis, leukemogenesis

Question 16

Eg of deterministic effect

Answer 16

• cell death not repaired

- epilation, radiation sickness, erythema

Question 17

Time

Answer 17

• the longer the exposure, the higher the dose

Question 18

Shielding

Answer 18

• high density, high atomic number and thickness are required for protection
• 0.3mm lead aprons for X ray staff

Question 19

Distance

Answer 19

• radiation decreases with the square of distance
• twice the distance = 1/4 radiation level
• distance is the simplest and best protection

Question 20

Structure of radiation protection

Answer 20

• internal body sets standards and philisophy, based on reviews and radiation effect
• Main recomendations are for dose limits to workers and public, and risk factors
• dose limits are reduced to 25% for medical workers in NSW
• equivalent to 2x annual background

Question 21

Background radiation

Answer 21

• unavoilable and equivalent to 2 CXR per week in australia
• 2.3 mSv/yr in Sydney
• from radon/thoron in air mainly
• medical sources add about 15% average

Question 22

Patient dose, indicated exposure

Answer 22

• doses for diagnostic procedures range from 20 year
• therapeutic procedures ranfe up to thousands of background years
• effects can be serious but rare
• CT scans largest source of exposure (50%)

Question 23

Accident types

Answer 23

• wrong patient, wrong examination, wrong body part
• irradiation of uterus in unknown pregnancy
• overdose
• contamination

Question 24

In utero irradiation

Answer 24

• before implantation: no risk
• 3-8 weeks: organ malformation
• 8-25 weeks: severe mental retardation
• organogenesis - cancer/leukemia in childhood or adult life

Question 25

Risk for cancer/leukemia

Answer 25

- about 3 times that for pop as a whole - 16%/SV At most

Question 26

Legal oblications

Answer 26

- regulatory body in NSW is the EPA - radiologist and nuclear medicine physicians need a license - non-radiologists want to use fluoroscopy need a licence - radionuclide users ned a licence - all examinations must be approved by a doctor

Question 27

Other legal obligations

Answer 27

- radiation apparatus must be registered - premises must be rgistered - certain worker groups need a radiation monitor - accidents must be reported - research using radiaiton must be evaluated and approved

Question 28

3 doctors rule

Answer 28

- limitation - justification - optimisation