Safety, QA, Prescribing Radiographs- Day 3 Flashcards
Exposure measures
Measures capacity of x-rays to ionize AIR
Unit: roentgen (R) = coulombs/kg
Measures intensity of radiation field; NOT radiation absorbed
Absorbed dose measures
Measure of total energy absorbed by any type of ionizing radiation PER UNIT MASS OF MATTER
Unit: gray (Gy) = J/kg
Effective dose
Estimates risk in humans
Primary risk of dental radiography is
Cancer
Cancer risk well established for high dosage
Less certainty regarding low-dose procedures
Linear non-threshold hypothesis
Widely accepted in radiation safety and protection
Linear relationship between dose and risk of inducing a new cancer
No threshold = no “safe dose”
3 guiding principles in radiation protection
Justification
Optimization
Dose Limitation
Justification
Patient benefit vs. risk of harm
Which patients need which examinations
Optimization
Use every reasonable means to reduce unnecessary expsosure
ALARA =
As Low As Reasonably Achievable
Dose Limitation
Limits for workers and public but NOT patients
Patient selection
Radiographic screening for the purpose of detecting disease before clinical examination should not be performed. A thorough clinical examination, consideration of the patient history, review of any prior radiographs, caries risk assessment and consideration of the dental and general health needs of the patient should precede the radiographc examination.
___speed film twice as fast as group D (half the exposure)
E/F
Source to skin distance
Use of long source to skin distances of 20 cmto 40 cm are appropriate, but longer distances are optimal
Preferred collimation shape and why
Rectangular>circular because rectangular will decrease radiation dose by up to fivefold as compared with a circular one.
What part of the body is very susceptible to radiation
Thyroid, esp. in children
Use leaded aprons and thyroid collars
ADA and NCRP concluded
leaded aprons unnecessary
Film holders recommended
that align the film precisely with the collimated beam are recommended for periapical and bitewing radiographs
The optimal operating potential of dental x-ray units is between
60 and 70kVp
Usually kVp and mA are fixed; only what changes?
time
To protect office staff, barriers should contain a
leaded glass window
When shielding is not possible, the operator should stand
at least 2 meters from the tube head and out the path of the primary beam.
Position-and-distance rule
Used when use of barrier is impossible
Operator is at least 6 feet from patient at an angle of 90 to 135 degrees to the central ray of the x-ray beam
Used when use of barrier is impossible
Operator is at least 6 feet from patient at an angle of 90 to 135 degrees to the central ray of the x-ray beam
Workers may not receive an annual dose
greater than 1 (ONE) mSv
New patient: Child with Primary Dentition
Selected periapicals/occlusal/bitewings if proximal surfaces cannot be visualized
New patient: Child with Transitional Dentition
Individualized exam consisting of posterior bitewings with panoramic exam or selected periapical
New patient: Adolescent with Permanent Dentition
Individualized exam consisting of posterior bitewings with panoramic exam or selected periapicals
Full mouth recommended when patient has generalized disease or history of extensive dental treatment
Pregnancy
Fetal exposure is ~1 microGy for a full-mouth examination
ADA recommends use of thyroid colar and aprons during dental radiography of pregnant patients
