Radiation protection

Question 1

Radiation protection aims to

Answer 1

reduce radiation risks (complications).

Question 2

3 General radiation protection principles?
exam question!

Answer 2

Use of radiation must always be justified (Justification)

ALARA (As Low As Reasonably Achievable) principle (Optimization) (in reference to radiation doses)

Implementation of dose limits (Limitation)

Question 3

What does Gy stand for?

Answer 3

“The gray” is the unit of ionizing radiation dose in the International System of Units (SI).

Gy and Sv is essentially the same thing or at least treated that way in many contexts.

For X-rays and gamma rays the gray is numerically the same value when expressed in sieverts.

Question 4

Definition of Dose in the context of radiography

Answer 4

Measure of radiation received or absorbed by a subject. For characterization of radiation and substance interactions (including transmitted energy) (Gy-unit).

Question 5

Definition of Dosimeter in the context of radiography

Answer 5

is a device that measures exposure to
ionizing radiation.

It has two main uses: for human radiation protection and for measurement of dose in
both medical and industrial processes.

Question 6

Absorbed dose is what?
How is it denoted?

Answer 6

Absorbed dose:
Symbol - D, Unit- Gy, 1 Gy= 1 J/kg

The average energy transferred to the substance.

Question 7

How is equivalent dose denoted?
What is it?

Answer 7

Equivalent dose: Symbol- H, Unit- Sv

Uses a radiation weighting factor that considers different biological effects of various types of radiation.

Equivalent dose measures the biological effect that the organ or tissue gets.

Question 8

Explain Effective dose

Answer 8

Summed whole body dose

Symbol- E, Unit- Sv (sievert)

Indicates radiation harmful effect to humans. The risk rate of late
complications (cancer, hereditary diseases).

+ Tissue weighting factor (shows you the relative sensitivity of the organ or tissue).

Question 9

Difference between:
absorbed dose
equivalent dose
effective dose

Answer 9

Absorbed Dose: amount of radiation energy absorbed per unit mass of tissue, measured in Grays (Gy). It quantifies the actual energy deposited in a material.

Equivalent Dose: Takes into account the type of radiation (e.g., alpha, beta, gamma), weighing the absorbed dose by a radiation weighting factor. It’s measured in Sieverts (Sv) and reflects the potential biological harm of different types of radiation.

Effective Dose: Further adjusts the equivalent dose by considering the varying sensitivity of different tissues and organs to radiation. Also measured in Sieverts (Sv), it represents the overall risk of exposure to different types of radiation.

Question 10

Explain Personal dosimeters

Answer 10

Personal dosimetry checks for radiation that is present around workers wearing
thermoluminescent dosimeters (TLDs)
(there are also other types of dosimeters).

The radiation worker can receive information about their own effective dose.

Unit: mSv (millisievert)

The measurement is carried out by the Radiation Department of the Environmental Board.

Question 11

Where should you wear your dosimeter?

Answer 11

Wear it in the chest region on the outside of the lead apron.

Question 12

Categories of radiation workers

Answer 12

Category A & B

Question 13

Describe Category-A of radiation workers

Answer 13

Category A radiation workers receive or may receive a higher annual effective dose than 20 mSv.

 Dosimeters are measured once a month.
 Category A radiation workers must undergo a medical examination
at least once a year.

Question 14

Describe Category B of radiation workers

Answer 14

The annual effective dose of category B radiation workers must be between 1 mSv-6 mSv.

 Dosimeters are measured at frequency once every three months (4 times a year).

Question 15

Effective dose limits

Answer 15

Depending on radiation worker category A or B.

Question 16

When ionizing radiation comes in contact with a cell any or all of the following may happen: (3)

Answer 16

 Radiation may damage the cell but the cell will repair itself.

 Radiation may affect the cell’s ability to reproduce itself correctly, possibly
causing a mutation.

 Radiation may kill the cell. The death of one cell is of no concern but if too many cells in one organ (e.g. liver) die at once, the organism will die.

Question 17

Radiation damage to the DNA can be
caused by what specifically?

Answer 17

the direct action of ionizing radiation (mostly alpha radiation) or indirect action of radiation (x-rays).

Question 18

Direct action of ionizing radiation occurs when

Answer 18

alpha particles, beta particles or x-rays create ions which physically break one or both of the sugar phosphate backbones or break the base pairs of the DNA.

 Note- all three types of radiation can
break “backbone“ of the DNA, break
hydrogen bonds and damage bases.

Question 19

Explain indirect action of ionizing radiation on DNA.

Answer 19

Ionizing radiation can damage cells
indirectly by creating free radicals.

 Free radicals are molecules that are
highly reactive due to the presence of
unpaired electrons on the molecule.

 As a result of these chemical changes,
cells may undergo a variety of structural changes which lead to altered function or cell death.

Question 20

Ionizing radiation can cause two types of breaks in the sugar phosphate
backbone.

Answer 20

A single strand break - are readily repaired using the opposite strand as a
template.

Double strand breaks are believed to be the most harmful lesions produced in
chromosomes by ionizing radiation because such breaks are difficult to repair, they can cause mutations and cell death.

Question 21

2 types of mutations can occur with single strand breaks from indirect radiation:

Answer 21

1. Base pair substitutions - replacement of one base by another.
2. Frameshift mutations - changes the reading frame of a gene. 2 possibilities:
   Insertion of one or more extra nucleotides into a DNA chain or loosing one or
   more nucleotides from a DNA chain.

Question 22

Difference between deterministic and stochastic effects of radiation.

Answer 22

Deterministic Effects occur only above a certain radiation dose threshold, Severity increases with increasing dose.

Examples include skin burns, cataracts, and radiation sickness. Usually involve damage to a large number of cells.

Stochastic Effects have no threshold; even low doses can cause effects, but the probability increases with higher doses.

Severity is independent of dose; instead, the likelihood of occurrence rises.
Examples include cancer and genetic mutations. Are caused by damage to individual cells, often leading to long-term effects.

Question 23

The deterministic effect of radiation lies in

Answer 23

a high dose, which damages many cells at once and has an acute effect.

Deterministic effects describe a cause
and effect relationship between
radiation and certain side-effects.

Deterministic effects only occur if the
dose is higher than a certain threshold
value.

Question 24

Describe stochastic effects of radiation.

Answer 24

Stochastic effects account for the remaining late onset effects:
 They have no threshold dose.
 They increase in likelihood as dose increases.
 Their severity is not dose related.

 cancer or genetic mutations, do not have a guaranteed threshold or dose level where they will definitely happen.

 Stochastic effects include tumor and hereditary effects.

Question 25

How many Gy are lethal?

Answer 25

6 Gy for sure

but 3-5 Gy can kill some individuals

= 6000 mSv
= 6 Sv

Question 26

Risk, in radiation protection, is the probability of

Answer 26

developing distant effects, such as tumors or hereditary defects.

The risk of developing tumors (probability) for Sv per year, in lifetime is:

 For 1 Sv, 5 out of 100 people
 For 100 mSv, 5 out of 1000 people
 For 1 mSv, 5 out of 100,000 people

Question 27

What are the General principles of radiation protection of personnel? (3)
exam question!

Answer 27

Time, distance and shielding.

Time - limit and minimize exposure

Distance - dose decreases with distance and this helps staff

Shielding - lead barriers on ppl, concrete for xray rooms, radioactive substances can be stored under water (limits penetration)

Question 28

Radiation protection of the patient (animals)

Answer 28

The medical personnel and patients radiation protection is inseparable from one another.

 Repeated X-ray exposures increase risk
 Collimation as precise as poss.
 Optimized parameters to reduce unnecessarily large doses.

Question 29

To reduce patient exposure and scatter
radiation, also to improve contrast, what simple action should be done?

Answer 29

patient exposure area is collimated as small as possible.

Question 30

The effect of radiation on an unborn, human child depends on: (2)

Answer 30

 The size of the radiation dose

 Fetus development stage

 Prenatal death - the most risk-sensitive period: 0-8 days after conception.

Threshold dose, that causes fetal death, malformation and mental retardation,
a dose of 100-200 mGy/mSv or more is considered.

Question 31

The radiation risk level for children under 10

Answer 31

is up to 17% per Sv compared to 4% for adults (ICRP).

Children’s cells divide rapidly and organs may be less differentiated, so they are more sensitive to radiation.

Children have a longer life expectancy - more likely to develop cancer.

Question 32

The rules for safe use of the X-ray device (5)

Answer 32

 The person staying in the X-ray room must be over 18 years of age.

 If you are pregnant or not sure that you may be pregnant, do not enter the X-ray room.

 When performing a X-ray examination, persons who stay inside the room must wear personal protective equipment:
lead apron, protective gloves, thyroid protection and, if necessary, safety glasses.

 Before the exposure, close all doors.

 If the animal is anesthetized (small animal), use sandbags to fixate the animal.
Avoid placing hands and getting your body into the radiation field!

Question 33

When using a mobile X-ray machine
outside the X-ray room, make sure that: (3)

Answer 33

Everyone would properly use personal
protective equipment.

X-rays are not directed towards a wall behind which are people.

Random people would not be in the same
room while taking the picture.

Question 34

MRI is medical imaging technique that uses
what to obtain diagnostic images?

Answer 34

radio waves and a strong magnetic field to obtain diagnostic images.

MRI does not use ionizing radiation so its known to be safe.

Nowadays, different magnets are used in
clinical practice:
➢ Permanent Magnet scanner (up to 0.5-0.7 T)
➢ Electromagnet (up to 0.3 T)
➢ Superconducting scanner (usually 1.5-3 T) (cooled with liquid helium or nitrogen)

In the MRI room, there is always a magnetic
field (with the exception of an electromagnet that can be turned off).

Question 35

There are two types of metals, what are they

Answer 35

ferromagnetic and non-ferromagnetic

Most common ferromagnetic metals are iron, cobalt and nickel.

Ferromagnetic does not mean that
a metal contains iron, but rather that the material has magnetic properties as iron can.

Metal objects can create artifacts in MRIs.

Question 36

To avoid health risks, you must not enter MRI room, if You have: (4)

Answer 36

 Pacemaker
 Ear implant that can not be removed
 Ferromagnetic metallic vascular clips
 Some types of joint prostheses, metal foreign bodies, fracture fixing plates
and screws.

Just in case - all metal objects must be removed as we are not going to determine material composition of the object.

Question 37

Safety requirements in Computed Tomography (CT)

Answer 37

 The study must be justified.

 Based on human radiation protection, CT
studies should not be performed if the animal is pregnant.

 Use of low-dose protocols.

 AEC (is Automatic Exposure Control (AEC), which aims to automatically modulate the tube current)

 Before starting the CT scan close all doors.

Staff may not be inside the study room when CT examination is performed. The patient must be sedated and no one is allowed to stay with the animal.

Question 38

UV-C radiation safety

Answer 38

UV-C ceiling and movable lamps are used for disinfection because the light wave destroys the DNA of bacteria, viruses, spores, fungi, mold and mites.

 Turn off UV-C lamps immediately when
entering a room.

 Do not stay in room while UV-C lamps
are working - protect skin and eyes.

 Mercury is used in UV-C lamp bulbs. If
the bulb breaks, the room should be
ventilated.

 Do not leave medical equipment in a
room where UV-C lamps are operating
(UV-C radiation breaks down polymer
structures (such as plastics) - cracking
occurs.

Question 39

Medical oxygen safety

Answer 39

Oil and grease are extremely hazardous
in the presence of medical oxygen, and
there is a risk of explosion or fire.

 Never use oil or grease as a lubricant in
devices using medical oxygen.

 Smoking and open flames are not
allowed near oxygen equipment.

 Never use electrical equipment such as
hair dryers at the same time as oxygen
therapy.

Question 40

Symbols denoting:
absorbed dose
equivalent dose
effective dose

Answer 40

Absorbed dose: Symbol - D, Unit- Gy
Equivalent dose: Symbol- H, Unit- Sv
Effective dose: Symbol- E, Unit- Sv

Question 41

General radiation protection principles?

vs

General principles of radiation protection of personnel?

Answer 41

Justification, ALARA (Optimization), Limitation

vs

Time
Distance
Shielding