4.2 - Radiation Safety and Protection

Question 1

natural background exposures from most to least percent

Answer 1

radon > space radiation > internal radionuclides > terrestrial radiation

Question 2

what is this:

73% of the total background radiation
Uranium-238 decays to form this

Answer 2

radon

Question 3

what is this:

11% of total background radiation
a function of altitude

Answer 3

space radiation

Question 4

what is this:

7% of total background radiation
Uranium-238 and Thorium-232 decay to form other elements like Potassium-40
Releases gamma radiation

Answer 4

terrestrial radiation

Question 5

what is this:

9% of total background radiation
Ingested (mainly food) substances that contain Uranium, Thorium, and their decay products (Potassium-40, Carbon-14, etc.)

Answer 5

internal radionuclides

Question 6

how many xrays and nuclear examinations per year (worldwide)

Answer 6

3.6 billion

Question 7

what is the biggest source of medication radiation exposure

Answer 7

CT

Question 8

what percent of total exposures from medical sources are dental related

Answer 8

0.26%

Question 9

is radiation cumulative?

Answer 9

YES! all radiation individual is exposed to accumulated over time

Question 10

what is a “linear” relationship between radiation dose and the risk of biological effects (cancer in this case)

Answer 10

linear no-threshold hypothesis

Question 11

even at low doses, is patient at risk

Answer 11

yes

Question 12

is LNT model a fact or hypothesis

Answer 12

HYPOTHESIS!

Question 13

what is LNT used for

Answer 13

to help experts set dose limits

Question 14

can even ONE photon induce biological risks

Answer 14

YES

Question 15

what can we do if one photon can induce biological risks

Answer 15

Limit the dose: only necessary radiographs, use safety and protective precautions
Dose limits: set by policymakers to stay within a certain “low-dose” range

Question 16

guiding principles to implement radiation protection

Answer 16

1. justification
2. optimization
3. dose limitation

Question 17

Benefit to a patient from the diagnostic exposure likely exceeds the
risk of harm
Influences which patients are selected for radiographic examinations and
what examinations are chosen

Answer 17

justification

Question 18

what principle:
ALARA
Dentists should use every reasonable means to reduce unnecessary
exposure
to their patients, their staff, and themselves

Answer 18

optimization

Question 19

what principle:
Applies to dentists and their staff who are exposed occupationally but not
to patients because there are no dose limits for individuals exposed for
diagnostic purposes

Answer 19

dose limitation

Question 20

what is used for patient protection

Answer 20

1. patient selection criteria
2. film and digital sensors
3. intensifying screen and film
4. source-to-skin distance
5. collimation
6. filtration
7. aprons and thyroid collars
8. film and sensor holders

Question 21

is film or digital faster

Answer 21

digital

Question 22

what are types of films and rank from slowest to fastest

Answer 22

D < E < F

Question 23

what screens to used with high-speed films

Answer 23

rare-earth intensifying screens

Question 24

what technique:
with an increase in distance, the beam becomes less divergent, which in return reduces the total volume of tissue that is being exposed

Answer 24

Long cone technique

Question 25

in collimation, field of radiation at patient's skin surface should be no more than what diameter

Answer 25

7 cm

Question 26

where is collimator located

Answer 26

fixed within PID or attached to end of PID

Question 27

shapes of collimator? what is recommended

Answer 27

round or rectangular. rectangular recommended (5 fold reduction in radation exposure when compared to round and improved image quality)

Question 28

do low energy photons add diagnosis value in imaging? explain

Answer 28

NO! it exposes patients and personnel to unnecessary radiation

Question 29

filtration minimzes what

Answer 29

low energy photons

Question 30

Federal regulations: ___ mm of aluminum in machines that operate below 70 kV ___ mm of aluminum at higher kV ranges

Answer 30

1.5; 2.5

Question 31

what are aprons lined with? why?

Answer 31

lead lined to attenuate xrays and reduce gonad and thyroid gland exposure

Question 32

what is gland is most susceptible to radiation exposure during dental radiographic exams

Answer 32

thyroid gland

Question 33

what do film and sensor holders limite

Answer 33

limit cone cutnig and reduce instances of remade exposures

Question 34

why do exposure times vary from region to region

Answer 34

Bone density differs in different areas of the mouth. Exposure time must be altered to achieve optimal images in each area.

Question 35

improperly processes film can lead to what

Answer 35

patient being exposed to ionizing radiation unnecessarily to compensate

Question 36

what are materials that attenuate radiation?

Answer 36

barriers

Question 37

barriers should have what to do what

Answer 37

have leaded glass window to observe patient during exposure

Question 38

position and distance rule

Answer 38

if no barriers are available, you should stand at least six feet away from the patient at an angle of 90-135 degrees to the direction of the X-ray beam, on either side of the patient

Question 39

what provdes a zone where backscatter radiation is negligible

Answer 39

backscatter shield

Question 40

where should handheld radiographic device be positioned

Answer 40

perpendicular to operator

Question 41

what is a personal monitoring device

Answer 41

dosimeter

Question 42

what is devices worn by occupational professionals that measure the amount of radiation the professionals are exposed to This information is monitored to ensure that the professionals are not exposed to inordinate amounts of radiation

Answer 42

dosimeters