Ch.5 And Ch.11 Flashcards
What is personnel monitoring ?
The monitoring of equivalent dose to any person occupationally exposed on a regular basis to monitor ionizing radiation. (Dosimetry)
Radiation workers are at risk to receiving _____% or more of the annual occupational effective dose limit because of their work-related activities.
10%
Most healthcare facilities issue dosimetry devices when personnel could receive approximately ______% of their annual effective dose in any month which is _____.
1%, 0.05msv or 50rems
Occupational radiation exposure levels are kept well ______ annual effective dose limits
Below
Annual whole body dose for occupational exposure
5rem/50msv
Annual whole body dose for general public exposure
0.5rems/5msv
Annual whole body doses for embryo during the entirety of the gestation period
Should not exceed 0.5rems/5msv
Annual whole body doses for embryo during any month for gestation
Should not exceed 0.05rems/0.5msv
Where do you place a personnel dosimeter when you’re not wearing a lead apron?
At collar level
Placement of personnel dosimeter when wearing a lead apron?
At collar level on the outside of the protective apron
Placement of personnel dosimeter when tech has two personnel dosimeters AND wearing a lead apron?
At collar level on outside, one at waist level beneath the apron
Placement of personnel dosimeter when tech is pregnant
Worn underneath lead apron at waist level and outside at collar level (?)
What are the types of personnel dosimeters?
Film badge, TLD, OSL, pocket dosimeter
Which dosimeter relies on the ability of ionizing radiation to affect a density change on film emulsion ?
Film badge
The TLD (_______) functional component is the ____________. Readings are made by heating the _______ clip to a point of combustion.
Thermoluminescent dosimeter, lithium fluoride
Which personnel dosimeter contains an aluminum oxide detector and is exposure to a laser light?
Optically stimulated luminescence dosimeter (OSL)
The Pocket Dosimeter gives ______ readings and ionizes _______ in the chamber with the electrical charge reading out by introducing a signal.
Instant, gas
Personal dosimeters from MOST to LEAST radiosensitive
Pocket dosimeter, OSL, TLD, Film Badge
3 categories of radiation survey instruments for area monitoring
- Those w/o a readout scale
- Those with a readout scale
- Ionization chamber based
______ ________ tube is the most common. Serves as a primary portable radiation survey instrument for area monitoring in nuclear medicine facilities.
Geiger-Muller
Gas filled detectors include
- Ionization chamber type survey meter (cutie pie)
- Proportional counter
- GM survey meter
Which gas -filled detector is used to measure alpha and beta radiation and is not useful in diagnostic imaging ?
Proportional counter
Which gas-filled detector is used for x-radiation from radiographic and fluoroscopic x-ray equipment and is used for radiation protection surveys?
Cutie pie
What are x-ray beam limitation devices made of?
Lead
Simplest type of beam limitation device. Flat, lead plate with hole in the middle. Hole will be slightly smaller than IR. Fits below x-ray tube window. Utilized for equipment with a fixed SID and fixed IR size. FOV is not adjustable.
Aperture diaphragm
Techs can control. Length and width can be adjusted. Uses light localization to give us our size and shape. (Manual)
Variable aperture collimators
Circular shape. Attaches to the bottom of the collimator housing. EX: dental, facial bones, sinuses
Cylinders and cones
Gives us the exact size of the structure that is selected. Automatic
Positive beam limitation
A properly collimated beam can
Reduce scatter and reduce pt dose (reducing pt dose=^ quality of image)
Typically composed of aluminum and expressed in mmAl/eq.
Filtration
What is the primary purpose of filtration?
Removes low energy photons from reaching the IR and reduces scatter
What effects does filtration have on average beam energy?
Removes low energy, nondiagnostic x-ray photons from the beam
Hardens the beam by increasing the effective energy and quality of the beam
Expressed as a % of beam penetration (what percentage of the beam has penetrated the patient)
Increasing filtration=Decreases exposure rate
What does inherent filtration consist of?
Exists in the construction of the tube.
Glass envelope, insulating oil, collimation mirrors
0.5-1mmAl/eq
What does added filtration consist of?
Layers of aluminum placed in the path of a primary beam to increase total filtration
EX: mammography
What does total filtration consist of?
Inherent + Added
Total Filtration Guidelines state that any tube operating above ______ must have a minimum of _____ filtration.
70kvp, 2.5mmAl/eq
Total filtration for kvp ranges below 50kvp
0.5mmAl/eq
Total filtration for kvp ranges from 50-70kvp
1.5mmAl/eq
Total filtration for kvp ranges above 70kvp
2.5mmAl/eq
What must be measured to verify that the x-ray beam is adequately filtered?
Half value layer
When discussing the actual x-ray tube, HVL is expressed in
MmAl
Compensating filters are commonly made of
Aluminum, lead acrylic, and other suitable materials
Compensating filters partially attenuates the x-rays directed to the ________ areas while permitting more x-radiation to strike the thicker, more dense area
Thinner
Compensating filters partially attenuates the x-rays directed to the ________ areas while permitting more x-radiation to strike the thicker, more dense area
Thinner
AEC
Automatic Exposure Control
Another term for AEC
Phototiming
AECs are designed to produce an acceptable image while ______ radiation exposure to the patient
Limiting
Todays AEC systems utilize ______
Ionization chambers
What are grids constructed of?
Parallel stripes (radiopaque strip)
Using a grid requires
More exposure
Grids are used on body parts that are more than _____cm thick (______in)
10cm, 4in.
_______ mAs is needed with an ______ in grid ratio
Increased, increase
Increasing grid ratio=_____ scatter=______ quality=________ patient dose
Decreases, increases, increases
Grids higher than ______ are not usually used in Diagnostic imaging
12:1
