radiation protection aka dose reduction mechanisms Flashcards
two goals for oral and maxillofacial radiology
- reduce radiation exposure
- maintain high degree of diagnostic efficiency
-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.
-time, distance, and shielding factors were prioritized
ALARA
as low as reasonably achievable
(guiding principle of radiation protection)
does reduction mechanisms
xray tube head (mandated)
- filtration
- collimation
filtration blocks
long wave lengths and only allows short wavelengths to reduce radiation
- 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
mandated minimum total filtration for xray tubes
operating kv…
<50 =
50 to 70 =
>70 =
what are aluminum filtration (mm)
aluminum filtration(mm)
<50 = 0.5mm
50 to 70 = 1.5mm
>70 = 2.5mm
exit side beam, collimation max is what diameter
2.75 inches “
(rectangular preferred)
- rectangular collimator
- High kV generator/
transformer - Constant potential
(DC) fully rectified - Increased focal length
this shape of collimator:
xray tube head options for dose reduction me
area exposed is related to the
maximum size of the beam
effect dose for common exams,
FMX PSPP-rectangle coll=
FMX CCD- rectangle coll=
FMX PSPP- round coll=
FMX CCD- round coll=
so basically, ____coll has less radiation exposed
FMX PSPP-rectangle coll=35
FMX CCD- rectangle coll=17
FMX PSPP- round coll=171
FMX CCD- round coll=85
RECTANGLE better
lower dose with ___kV
higher
units are larger
heavier
more money
increased of long BID benefits: (increased focal distance)
- 27% less head volume
- reduced effective dose
- sharper image
Dose Reduction Mechanisms Practice Options
- Sensor speed (sensitivity)
- Lead (Pb) thyroid collar
- Film-holding devices with beam alignment capability
- Time-temperature or digital quality control processing
film speed:
-D speed (ultraspeed)
-E speed
-F speed (insight)
-digital receptors:
1. PSPP
2. CCD (more sens tho)
3. CMOS (seen most)
patient protection
lead apron and thyroid collar
2 recommendations for patient shielding during dentomaxillofacial radiology
- stop shielding of gonads, pelvic and fetus
- stop thyroid cover
during an exposure taken with wall-mounted xray unit, the operator shall stand
behind protective barrier
if barrier not present for operator they should
stand 6 feet from patient at angle between 90-135 degrees to the direction of the useful beam
never stand
in the primary beam
try to stand behind barrier
worn by all full-time
operators of radiographic equipment while xray exposures are being made.
Dosimeter badges
annual occupational whole body exposure will not exceed
50mSv
operators who have declared preg will not receive more than __mSv to the embryo or fetus during the term of pregnancy
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