Part 6: Protection Flashcards
ALARA principle assumes what?
That there is no threshold of radiation dose necessary to achieve a biological effect
Stochastic effects means the ___ of an effect occurring rather than the ___.
probability
severity
Stochastic effects are regarded as a function of ____.
radiation dose without a threshold
Nonstochastic effects mean those effects for which the ____ varies with ___.
severity
radiation dose
Stochastic or nonstochastic?
carcinogenesis
stochastic
Stochastic or nonstochastic?
cataracts
Nonstochastic
Stochastic or nonstochastic?
bone marrow depletion
Nonstochastic
Stochastic or nonstochastic?
non-malignant skin damage
Nonstochastic
Stochastic or nonstochastic?
Somatic effects
Stochastic
Any occupationally exposed individual should not receive a dose more than ___ rem in one calendar year.
5 rems
What is the source of the chief radiation exposure to the operator?
Scatter radiation from the pt
X-ray tube current and ABC should be monitored how often?
once per week
What % reduction in scatter radiation exposure does the 0.5mm lead equivalent apron achieve?
99.9%
Protective gloves of ___ and ___mm lead equivalent are available and must be worn whenever the hand is directly under the x-ray beam.
0.25mm
0.5mm
Protective curtain (overlapping protective drapes) of at least ___mm lead equivalent should be positioned between the ___ and the ___.
0.25mm
patient
fluoroscopist
Mobile screen desks usually come in what increments of mm lead equivalent?
1.0mm and 2.0mm
What are the 2 types of acceptable personnel radiation monitoring devices?
Film badge
Thermoluminescent dosimeter (TLD)
In addition to the film badge or TLD, what other monitoring devices can be worn?
pocket chamber or dosimeter
audible warning device
What is the primary purpose of the filter in the film badge?
to permit dose measurements over a wide range of energies
FIlms used for film badge dosimeter are sensitive to exposure equivalent to doses as low as ___ and as high as ___.
10 milirad
700 rads
1 rem of x-rays is approximately equivalent to ___ rad.
1
What is the most common material used in the TLDs?
lithium fluoride
in solid chip form
What are TLDs sensitive to?
light
(have to be stored sealed)
How do TLDs work?
- ionizing radiation interacts with lithium fluoride crystals
- crystals raised to higher energy states of excitation, become trapped
- crystals heated in measuring device and light is emitted proportional to radiation absorbed and measured
Which are more accurate: TLDs or film badges?
TLDs
Main disadvantages to TLDs
Can only read exposure once, thus not a permanent record
they’re $$$
What is a small pencil sized instrument that discharges a capacitor by ionization of air within the chamber when in the presence of ionizing radiation?
Pocket ionization chamber
What are the two types of pocket ionization chambers used for personnel monitoring?
self-reading
special-device-reading
Some disadvantages to pocket ionization chamber monitoring?
no permanent record
calibrate periodically
sensitive to mechanical shock
subjective reading
limited dose range
possible loss of info if exposed over its maximum
Should a pocket ionization chamber be used alone?
NO
only with film badge or TLD
Benefit of wearing an audible warning device in addition to a TLD or film badge
you can have immediate dose feedback (others take a couple weeks to read and get results back)
Where can you wear an audible warning dose-rate meter?
clipped to garment or belt
placed in a pocket
When wearing a lead apron, where should the monitoring device be placed?
one the collar on the outside of the protective apron
Annual dose limits for:
whole body
skin and extremities
lens of eye
5 rem or 0.05 Sv
50 rem or 0.5 Sv
15 rem or 0.15 Sv
Convert 50 rem to Sv
0.5 Sv
TLDs and film badges are usually changed how often?
monthly
