lesson 2 Flashcards
where the highest occupational exposure
of diagnostic x ray personnel occur together
w/ mobile radiology
Fluoroscopy
- Wr = radiation weighting factor
(different types of radiation) - Wt = tissue weighting factor (tissue
radiosensitivity )
Effective dose
- quantity of importance
- Expressed in mSv (mrem)
Radiation weighting factor Wr- 1 ( 3
types of radiation used in medicine)
- x-ray
- gamma ray
- alpha particle- highest LET; highest
weighting factor (20)
accounts for the relative radiosensitivity of various
tissues
Tissue weighting factor (Wt)
top 2 radiosensitive tissue
- gonads w/ 0.20
- active bone marrow - 0.12
top 2 least radiosensitive tissue
- bone surface - 0.01
- skin (least sensitive) - 0.01
radiation is known to produce (cyclotron physicist)
cataracts
Individuals in the general population
dose limits
1mSv/yr (100mrem/yr)
leaner lined metal container into which the x
ray tube is fitted
- function: insulator (diala oil) against electric shock
Protective tube housing
non penetrating radiation
- alpha
- beta
- soft x-ray
- genz rays
indicates exposure and when the x ray tube
is energized with the use of mA and kVp
indicators
Control panel
restriction of the useful beam to reduce
patient dose and improve image contrast
Collimator
reduction in radiation intensity results from
absorption and scattering
ATTENUATION
feature of radiographic collimators that
automatically adjusts the radiation to the
size of the image receptor.
Positive beam limitation (PBL)
all general purpose diagnostic x ray beams
must have: Total filtration of- at least
2.5mmAl
- the output radiation intensity should be
constant from one exposure to another for
any given technique - checked by: repeating radiation exposure
though the same technique and observe the
average variation in radiation - the variation in X-ray intensity should not
exceed 5%
Reproducibility
ability of a radiographic unit to produce
constant radiation output for various
combinations of mA and exposure time(s)
Linearity
The maximum acceptable variation in linearity
is BLANK from one mA station to an adjacent
mAstation mAs= (mA*s)
10%
RT stands behind this barrier during the
exposure
Fixed protective barrier (console booth)
must be fixed to the operating console and not to a long cord
exposure control ( rotor button)
must be worn when the RT is in the exposure room during the exposure
Protective apparel
- A protective lead apron should be assigned
to each BLANK - the exposure switch 2m cord switch long
and stand 6ft away from the tube during
exposure - x-ray beam away from RT
Portable x-ray unit
Increasing the distance b/n the
fluoroscopic tube and the patient =
reduce patient dose
Decrease distance of the
fluoroscopic tube and the tabletop =
increase patient dose = increase
magnification
but to maintain exposure to the image
intensifier; BLANK must be increased to
compensate for the increased distance
(square law)
mA
SSD means
source- to-skin distance
ESD means
entrance skin dose or ESE (entrance
skin exposure)
dose that exits the patient
Exit exposure dose
SSD must not be less than 38cm
Stationary fluoroscopes
SSD not less
than 30 cm
Mobiles fluoroscopes-
Increase tube and tabletop distance =
increase mA
- serves as a primary protective barrier
- thickness 2mmPb equivalent
Fluoroscopic IR (image Intensifier
assembly)
Total filtration of the fluoroscope
At least 2.5mmAl
Included as part of filtration
- Tabletop
- Patient cradle
Operated at 80kVp- HVL should at least
BLANK (for adequate filtration)
2.4mmAl
-unexposed borders should be visible at all
heights above the tabletop
- collimator shutters should track w/ height
above the tabletop
For automatic collimating devices
fluoroscopic exposure switch, exposure is terminated when released the pedal
Dead man type
-conventional foot pedal
-Pressure switch
Exposure Control
- Size: at least 0.25 mmPb equivalent
- Position: b/n the fluoroscopy and the patient
Protective curtain/panel
produces audible signal/sound when the
fluoroscopic time exceed 5 minutes
Cumulative time
record the total fluoroscopy beam on time for each examination
Assisting personnel
