(*-*) EXPOSURE LIMITIS, SHIELDING, QA Flashcards
which barrier is where the useful beam hits?
primary
which barrier is where the scatter and leakage hits?
secondary barrier
restricted/controlled areas (like control room) are limited to ____ msv/wk or ____ msv/yr
.5 msv/wk
or 5 msv/yr
unrestricted/uncontrolled areas (like waiting room) are limited to ____ msv/wk or ___ msv/yr
.02 msv/wk or 1 msv/yr
who keeps the personnel dosimetry records?
RSO (radiation safety officer)
“monitored if expected to receive __% or more of effective dose”
10% or more of effective dose
label which is the PRIMARY BARRIER and which is the SECONDARY barrier
what interlocks are checked daily?
-door
- EPID collision
-safety lights
-audio/visual
-radiation output
-laser alignment
-ODI
-collimator indicator agreement
-imaging QA
-CT water phantom tests (noise and CT numbers/HU)
what interlocks are checked monthly?
-gantry collision
-emergency off buttons
-flatness and symmetry
-light and radiation field agreement
what interlocks are checked annually?
-electron cones
-gantry (mechanical iso)
-collimator (mechanical iso)
-radiation isocenter
what does a “functional” tolerance mean?
means it works, or it does not work - if it does not work, we cannot treat
safety lights, audio/visual, and emergency off buttons have what tolerance?
functional tolerance
safety lights for a LINAC say what? for HDR say what?
LINAC - beam is ON
HDR - source is exposed
what is most common malfunction of safety lights not turning on?
light bulb being out
if emergency off button fails to turn beam off, what is next step?
circuit breaker switch
each LINAC should have at least how many visuals? and a what kind of audio?
2
and a two-way audio system
with cameras, we have what kind of visual of LINAC treatment room. Whereas a CT room has what kind of visual?
an indirect visual
a CT room has a direct visual since kv source is low enough
what interlocks are checked weekly?
-MLC performance (picket fence test)
the “star pattern test” tests for what?
Radiation Isocenter – checks gantry, collimator, and couch
LEVEL 1 requires what?
can still trt but inspect
LEVEL 2 requires what?
can still trt but schedule maintenance ASAP
LEVEL 3 requires what?
do not trt - immediate action needed
1 TVL = ____ HVL
3.3
how much lead is in lead apron?
.5 mm
flattening filter is used for photons or electrons? and is in shape of what?
photons and is in shape of cone
- made of high Z material
high Z material = _________
absorption
intention of flattening filter is what?
to create a flat, even, dose distribution
intention of scattering foil is what? what is the material?
spread e- beam out
-copper or lead
primary collimators are __moveable/stationary__
stationary
secondary collimators are __moveable/stationary__
moveable & asymm
field size ranges from __x__ to __x___ of secondary collimators
0x0 to 40x40
MLCs can transmit <__% of beam
<2%
ODI is located __within/outside__ treatment head
outside treatment… but on it … ODI projects our numbers
you can or cannot adjust primary collimators?
cannot!
collimating jaws and mlcs are made of what?
tungsten
