Radiation Safety Flashcards
Although dental radiographs use a very small amount of radiation, can harmful effects still occur?
Yes, It is important to understand the risks and address them with patients
All ionizing radiation is — and produces — changes in living tissues
Harmful, biological
Ionization can cause disruption, which leads to?
temporary and/or permanent damage
Direct theory
radiation damages the protein, lipid, carbohydrate, and DNA molecule of a cell and causes cell death
- accounts for 1/3 of radiation-induced biological damage
Indirect theory
radiation interacts with the cells’ water content (H2O) and produces free radicals
- accounts for approximately 2/3 of radiation-induced biologic damage, proportional to the body’s water content (60-80% water)
Free radicals are mostly which elements? Are they stable?
H and OH; they are highly unstable
They interact with each other and produce toxins such as hydrogen peroxide (H2O2)
Latent period
time between radiation exposure and observed clinical effect
Acute exposure
occurs when a large dose of radiation is absorbed in a short period (e.g., nuclear exposure)
(high doses of radiation to the whole body may result in nausea, diarrhea, fever, hair loss, and death)
Chronic exposure
occurs when small doses of radiation are absorbed over time
- the effects may not be visible for an extended amount of time
- low doses of radiation received over a long period may result in cancers
Exposure of the entire body results in?
more severe biological effects
Long-term effect
may occur months, years, or decades following exposure
Cumulative effects
exposure to radiation has a cumulative effect over a life time
some tissues can repair themselves but some will stay damaged
Recovery period
repair period
Most injuries from low-dose radiation are repaired naturally
Somatic effect
injury to the person being affected
Genetic effect
injury to the future generation
Stochastic effect
probability of the occurrence increases with dose, but the severity is not dependent on the dose (e.g., cancer)
(all or nothing - a person either has or doesn’t have the condition)
Non-stochastic effect (deterministic)
severity of the damage is dependent on the dose (e.g., loss of hair)
Highly-sensitive cells
immature cells, quickly-dividing cells, younger person’s cells
Less-sensitive cells
highly-specialized cells, mature cells, slowly-dividing cells
Cell types in order of most sensitive to least sensitive
- Small lymphocytes, blood-forming (bone marrow) cells, reproductive cells, intestines
-Skin, lens of eye, oral mucosa
-Connective tissue, immature bone, blood
-Mature bone, salivary gland, thyroid, kidney, liver
-Muscle, nerve
Most sensitive parts of a cell
DNA and Chromosomes
Critical organs
organs that are more sensitive to radiation
CO: Thyroid
adult thyroid glands are fairly resistant to radiation while children’s thyroid glands are sensitive
CO: Bone Marrow
exposure to a large amount of radiation can cause leukemia
CO: Skin
radiation can cause erythema (redness)
Background radiation
radiation encountered in daily living arising from natural and artificial sources
natural sources of radiation
radon cosmic radiation, terrestrial radiation, etc.
- Accounts for most of background radiation exposure
- 20-images full-mouth survey taken with F-speed films and rectangular collimation is equivalent to 1-2 days of background radiation
Radon
a gas released from the ground and decaying material that releases radiation energy that penetrates every aspect of our environment (house, soil, etc.) and combines with dust, which can be inhaled
Artificial sources of radiation
Majority come from from medical assessments (not dental assessments)
CT scans emit 100 times more radiation energy than a dental radiograph
Other sources include: television sets, smoke alarms, building materials, etc
Dental radiation is responsible for — of the total exposure from medical imaging
1-5%
Dental exposure is similar to?
doses received during a cross-country airplane flight
What are the two systems used to measure the amount of radiation?
Standard (traditional) and Systeme Internationale (newer)
Standard units include:
Roentgen
Rad: Radiation absorbed dose
Rem: Roentgen equivalence in man
SI units include:
C/kg: Coulombs per kilogram
Gy: Gray
Sv: Sievert
Both units follow these specific conversions
1 Sv = 100 rem
1 Gy = 100 rad
Milli (m) is equal to 1000, therefore 1000 mrem = 1 rem
Exposure
quantity of ionization in the air
- the measurement is taken at the skin surface before radiation penetrates the tissues
- measured in Roentgen (Standard system) or Coulomb (SI system)
Absorbed dose
amount of radiation absorbed by an object
- depending on the material, the amount of radiation absorbed will vary
- measured in Rad (Standard system) or Gray (SI system)
Dose equivalent
absorbed dose “adjusted” to the biological damage potential of the particular type of radiation
- some types of radiation produce greater effects than others
- measured in Rem (Standard system) or Sievert (SI system)
Maximum Permissible Dose (MPD)
Defined by the National Council on Radiation Protection and Measurements (NCRP)
Is the dose of radiation expected to produce any significant radiation effects?
No
What is the MPD for an occupational person?
5 rem/year (5000 mrem), or 50 mSv/year
* 00 rem = 1 Sv; 1 rem = 0.01 Sv; 5 rem = 0.05 Sv = 50 mSv
MPD for a non-occupational person
10% of worker amount, or 0.5 rem (500 mrem), or 5 mSv/year
Maximum accumulated lifetime dose
5 rem x N - 18 (N = age)
For pregnant patients, use?
non-occupational dose
ALARA (As Low As Reasonably Achievable)
exposure should be kept to a minimum and benefits should outweigh the risks for the patien
Dental radiographs should be carefully prescribed depending on?
the patient’s age and risk level for oral diseases
Should “routine” radiographs be taken?
No
Dosimeter
receptor badge that measures exposure to radiation
Worn at waist level
New Patient
Primary dentition
selected periapical/occlusal views and/or posterior bitewings if proximal surfaces cannot be visualized or probed
New PT
Which type of patients may not require a radiographic exam?
Patients without evidence of disease and with open proximal contacts
* child dentition is more spread out, which usually allows the probe to detect the interproximal surfaces
New PT
Mixed dentition (after eruption of first permanent tooth)
posterior bitewings with panoramic exam; or posterior bitewings and selected periapicals
New PT
Adolescent
posterior bitewings with panoramic exam; or posterior bitewings and selected periapicals
New PT
A full-mouth intraoral radiographic exam is preferred when?
the patient has clinical evidence of generalized dental disease or a history of extensive dental treatment
Recall PT
T/F: Radiographs should be taken every 6 months regardless of the patient’s condition
False; should not
Examine the patient’s caries risk and determine the interval
Recall PT
Radiographs should be taken?
only if the interproximal surface cannot be examined with an instrument or visually
Recall PT
High caries risk
posterior bitewing examination at 6 to 12-month intervals for children and adults
Recall PT
Low caries risk
posterior bitewing examination at 12 to 24-month intervals (children), 18 to 36-month intervals (adolescents)
Periodontal Diseases & Growth Development
Clinical judgment should determine the need for and type of radiographic images
If adolescents are developing 3rd molars?
panoramic examination may be needed
Clinical Positioning
- Never stand in the line of the primary beam
- Clinician should stand behind a protective wall
- If a wall is not available, stand at least 6 feet from the source of radiation, at a 90-135° angle from the beam
- Clinician should never hold the tube head or receptor in the patient’s mouth during exposure. If assistance is required, a parent or guardian should be shielded and allowed to help the patient
Dosimeter
- Measures the amount of occupational exposure
- Most commonly worn as a badge that contains a receptor package
- The badge should be worn at all times by the professional at work.
- Every 3-4 weeks, the badge is sent for review
Equipment Monitoring
Dental radiographic machines should be inspected regularly to identify leakage
Digital radiography requires a – amount of radiation compared to receptor and is therefore considered –
lesser; safer
