best practices in radiation safety and protection

Question 1

primary sources of radiation

Answer 1

1) natural background
- 3.1 mSv
2) medical sources
- 3.0 mSv

Question 2

radon

Answer 2

1) gas from ground
- enter buildings, inhaled, and deposited to bronchial epithelium

Question 3

space radiation

Answer 3

1) sun or cosmic rays
2) altitude dependent
- each 2000m the radiation doubles
- 0.33 mSv per year at sea level

Question 4

internal radionucleotides

Answer 4

1) ingested
2) exposure from food containing uranium and thorium and decay products
3) bananas and brazil nuts

Question 5

terrestrial radiation

Answer 5

1) exposure from radioactive nuclides in soil

Question 6

medical exposure

Answer 6

1) CT 47%
2) consumer products 4%
3) 0.26% dental
4) conventional radiography and fluoroscopy 10%
5) interventional radiography and fluoroscopy 14%

• about equivalent to background exposure

Question 7

diagnostic imaging principle

Answer 7

1) benefit outweighs the risks
- principle risk is radiation induced cancer
2) must be
- optimized to produce a diagnostically acceptable image
- less than the threshold needed to cause any deterministic effects
- minimized to keep the risk of stochastic effects within an acceptable range

Question 8

linear no threshold (LNT) hypothesis

Answer 8

1) current paradigm for radiation protection guidelines and policy
2) not a demonstrated scientific fact
- linear relationship between dose and risk of inducing a new cancer (even at low doses)
3) no threshold
- no safe dose

Question 9

effective dose

Answer 9

1) radiation risk in humans
2) factors absorbed dose to various tissues and their radiosensitivity
- does not consider other factors
3) doses are measured using anthropomorphic phantom or modeled by simulation
4) does not represent a patient’s radiation dose from a radiographic procedure
- used to compare relative risks from different radiographic procedures to convey the magnitude of risk to patients
5) measure of stochastic risks
- cancer and heritable effects

Question 10

radiation protection

Answer 10

1) justification
2) optimization
3) dose limitation

ALARA
- as low as reasonably achievable

Question 11

justification

Answer 11

1) dentists must identify situations in which the benefit from a diagnostic exposure likely exceeds the risk of harm to the patient
2) practical implication
- identify which patients are selected for radiographs and which exams are chosen

Question 12

optimization

Answer 12

1) principle of ALARA
2) minimize reasonable means to reduce exposure to patients, staff, and self

Question 13

dose limitation

Answer 13

1) dose limits for occupational and public exposure to ensure that individuals are not exposed to unacceptably high doses
2) only applies to dentists and staff who are occupationally exposed
- this does not apply to patients

Question 14

patient selection criteria

Answer 14

1) reduce unnecessary radiographic examination
- only take radiographs when they are likely to provide additional information that is likely to contribute to the diagnosis and treatment plan
2) ADA radiographic selection criteria to satisfy the principle of justification
3) lowest dose image that would provide the necessary diagnostic information

Question 15

panoramic indications

Answer 15

1) overall evaluation of dentition
2) examine for intraosseous pathology
3) gross evaluation of temporomandibular joints
4) evaluation of TMJ
5) evaluation of impacted teeth
6) dentomaxillofacial trauma
7) developmental disturbances of maxillofacial skeleton

Question 16

film and digital imaging

Answer 16

1) fast films reduce exposure
- E/F speed film is 2x as fast and required half the exposure as group D films
2) digital sensors offer equal or greater dose reduction than E/F speed film

Question 17

source to skin distance

Answer 17

1) x-ray beam is less divergent with a longer source to skin distance, reducing the exposed tissue volume
2) longer source-to-skin distance also improves image quality as it decreases image magnification

Question 18

rectangular collimation

Answer 18

1) limiting the size of the x-ray beam to the size of the receptor reduces unnecessary exposure
- rectangular reduces area exposed by 60% compared to round collimation
2) also higher quality radiograph due to decreased amount of scattered radiation

Question 19

protective aprons and thyroid collars

Answer 19

1) CA requires use of protective aprons
2) however, if all other means to reduce exposure are applied, protection of the gonads is unecessary

Question 20

film and sensor holders

Answer 20

1) holders improve alignment during radiographic acquisition significantly reducing avoidable retakes

Question 21

milliampere seconds

Answer 21

1) exposure time is the most crucial setting in influencing diagnostic quality
- image density is controlled by quantity of x-rays produced, which is best controlled by milliapere seconds (mAs)
2) mA and kVp are generally fixed, the only setting the operator needs to select the proper exposure time
3) mount a chart showing optimal exposure times for each region in the arch (in children and adults) by each x-ray machine
4) general rule: less exposure time for anterior region and young patients

Question 22

image interpretation

Answer 22

1) should be viewed on a computer in a darkened environment

Question 23

barriers

Answer 23

1) consult an expert to design and construct dental clinics to meet radiation shielding requirements
2) lead barriers provide most effective method to protect operators from primary and scattered radiation
- exposure switch located behind barriers
3) position and distance rule
- operator should stand at least 6 feet from the patient at an angle of 90-135 degrees to the central x-ray beam
- think inverse square law

Question 24

do NOT

Answer 24

1) hold sensors in place
- the patient can do it if needed
2) hold radiographic tube housing during exposure

Question 25

handheld radiographic devices

Answer 25

1) designed to be held by operator during use
2) backscatter shield is incorporated into the device at the end of the collimator ring to provide a zone in which scatter radiation is negligable
2) for optimal operator protection
- hold device in horizontal position
- place backscatter shield close to the patient
- do not angle the device, ask patient to angle their head instead

Question 26

personal monitoring devices

Answer 26

1) measure operators occupational radiation dose
2) personnel likely to receive more than 10% annual dose limit are required to be monitored
3) clipped to front of chest typically monthly

Question 27

pregnant personnel

Answer 27

1) required to be monitored if the dose is likely to exceed 1 mSv during pregnancy

Question 28

occupational dose limits

Answer 28

1) apply to dentists and their staff who make diagnostic radiographs

Question 29

public dose limits

Answer 29

1) apply to support staff
- i.e. receptionists and patients

Question 30

quality assurance

Answer 30

1) program for periodic assessment of the performance of all parts of the radiologic procedure
2) some states may required written protocols and records of QA tests

Question 31

patient management tips

Answer 31

1) allow them to express concerns
2) Explain why you are recommending radiographs
3) inform new patients that you will request them from previous dentist
4) explain efforts to reduce patient exposure
5) communicate typical effective doses to recommended dental radiographs in comparison to other sources of radiation

Question 32

communicate with pregnant patients

Answer 32

1) ask your patient if they could be pregnant
2) defer routine radiographic examination until after pregnancy
3) if radiographs are needed for a pregnant patient
- emphasize diagnostic and treatment planning benefits of radiographs in maintaining good oral health
- explain could have adverse effects of baby
- reassure that fetal doses are about 42000 fold lower than threshold dose for deterministic effects