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
Operators who have declared a pregnancy will not receive more than __ mSv to the embryo or fetus during the term of the pregnancy.
5
What are the types of handheld x-ray units?
The NOMAD, NOMAD Pro and NOMAD Pro II are self-contained, hand-held, portable dental X-ray units.
How does the nomad device violate radiology statutes?
- During each exposure, the operator shall stand at least 6 feet from the patient or behind a protective barrier
- Neither the tube housing nor the position indicating device (cone, cylinder) shall be hand-held during exposure
NOMAD Use _______ current radiology statutes
Violates
A _____________ must be permanently mounted to the cone of a handheld x-ray unit and used at all times during radiographic exposure.
backscatter shield
What are the exemptions for licensed handheld units?
- A backscatter shield must be permanently mounted to the cone and used at all times during radiographic exposure.
- Operators must wear a personnel monitor device that is evaluated monthly.
- All personnel must receive training in the safe use of these X-ray systems, and records of the training kept for review.
What are the primary features of a NOMAD Pro?
Maximize the operator’s area
of protection while using a handheld x-ray unit by doing the
following:
- Place the backscatter shield at the end of the PID
- Align the PID close to the patient.
- Keep all body parts within the area of the shield’s protection.
More operator exposure if the
sensor does or does not parallel the standing position of the operator
DOES NOT
Less operator exposure and better shield protection, if the sensor DOES _______ the standing position of the operator
parallel
