Dose Reduction Mechanisms Flashcards
What are the goals for oral and maxillofacial radiology?
- Reduce radiation exposure
- Maintain a high degree of diagnostic efficiency
What is the guide principle for radiation protection?
As Low As Reasonably Achievable (ALARA)
● Since the probability or severity of biological damage increases as the radiation dose increases, it is desirable to avoid receiving even the smallest dose of radiation unnecessarily.
What are the mandated dose reduction mechanisms for the x-ray tube head?
- Filtration
- Collimation
What is filtration?
- Selective passage of contents through a specified substance
- Selectively removes a greater proportion of low keV x-ray photons
- Increases mean energy of the beam
Filtration ________ the mean energy of the beam
increases
Filtration selectively removes a greater proportion of _____ keV x-ray photons
low
What are the mandated minimum total filtrations for x-ray tubes?
What is the maximum diameter of beam collimation on the exit side?
2.75 inches
What are the dose reduction mechanisms for x-ray tube heads?
- Rectangular collimator
- High kV generator/transformer
- Constant potential (DC) fully rectified
- Increased focal length
What is the preferred shape for a collimator?
rectangle
AREA EXPOSED is related to the
__________ size of the beam
maximum
effective dose is reflective of the __________ technique
specific
The higher the kV the _____ the dose
Lower
What are the benefits of increased focal length/Long BID
- 27% less head volume
- reduced effective dose
- sharper image
What are the practice options of dose reduction mechanisms?
- Sensor speed (sensitivity)
- Lead (Pb) thyroid collar
- Film-holding devices with beam alignment capability
- Time-temperature or digital quality control processing
What are the different speed films?
- “D” speed (Ultraspeed)
- “E” speed
- “F” speed (Insight)
- digital receptors
— PSP
— CCD
— CMOS
What are the parts of the PSP plates for the air techniques?
- ScanX PSP plates
- Barrier Envelopes
- Plate Transfer Box
What are the options for patient protection?
- Lead apron
- Thyroid collar
What are the recommendations for patient shielding during dentomaxillofacial radiology?
- discontinuing shielding of the gonads, pelvic structures, and fetuses during all dentomaxillofacial radiographic imaging procedures
- thyroid shielding not be used during intraoral, panoramic, cephalometric, and CBCT imaging as the risks of thyroid cancer are negligible from contemporary maxillofacial imaging radiation doses
During an exposure taken with a wall-mounted x-ray unit, the operator shall…
stand behind a protective barrier
If a barrier is not present, the operator shall stand at least ____ feet from the patient and at an angle between 90° - 135° to the direction of the useful beam.
six
An operator should never stand in the _______ beam
primary
_________ badges will be worn by all full-time operators of radiographic equipment while x-ray exposures are being made.
Dosimeter
Annual occupational whole body exposure will not exceed ____ mSv
50
