Chapter 5 Flashcards
When are monitoring personnel devices required
Whenever radiation workers are likely to risk receiving 10% or more of the annual occupational EfD limit in any single year as a consequence of their work-related activities
What is the annual occupational EfD limit
50 mSv
Most health care facilities issue dosimetry devices when personnel could receive appox __% of their annual occupational EfD limit in any month
1% or .5mSv
Personnel dosimeter determines occupational exposure by:
Detecting and measuring the quantitiy of ionization that the dosimeter has been exposed to
Placement of primary dosimeter
Front of the body at collar level
Placement of primary dosimeter when a protective apron is used
Outside the apron at the collar level
Placement of dosimeter as a second monitor
Beneath the apron at waist level
Placement of dosimeter as a monitor for the embyro-fetus
Abdominal level beneath the apron
What type of dosimeter is used when performing radiographic procedures require the hands to be near the primary x-ray beam
Thermoluminescent dosimeter (TLD)
What is the most common type of dosimeter used for monitoring of occupational exposure in diagnostic imaging
OSL
What does OSL stand for
Optically Stimulated Luminescence Dosimeter
What is the OSL detector made of
Aluminum oxide
How is an OSL read out
By using laser light at selected frequencies
How long can an OSL be worn without a reading
1 year
What are the 3 different filters that are incorporated into the detector packet of the OSL dosimeter
Aluminium
Tin
Copper
What filter in the OSL dosimeter attenuates the least? Most?
Least - Aluminium
Most - Copper
In OSL dosimeters, ______ -energy radiation would demonstrate a similar reading through all 3 filters
High-energy
If an OSL dosimeter is subject to low-energy radiation, the laser readout would be much more pronounced in the region covered by the _______ filter
Aluminum
In OSL dosimeters, the varied energy ranges are classified as:
Deep - 1cm or more
Eye - .03cm
Shallow - .01cm or less
OSLs lowest and highest possible readings for xray
10uSv to 10 sV
Purpose of a control monitor
Used for a basis for comparison with the OSL dosimeters after they have been returned to the processing company
Advantages of the OSL
Lightweight
Durable (not affected by heat, moisture or pressure)
Easily worn
Disadvantages of OSL
Only records radiation exposure in the body where the device is attached
Exposure cannot be determined on the day of occurance
What information is recored on the peronnel monitoring report
Personal data
Type of dosimeter
Radiaition quality
EqD data (deep, eye, and shallow)
Cumulative EqD doses
Inception date
Ring dosimeters are most often worn by:
Nuc med techs
Where are ring dosimeters worn
Under gloves
What is the sensing material in TLDs
Lithium flouride
What happens in a TLD when irradiated
Electons in the lithium flouride molecule absorb energy and are excited to higher energy levels
What happens in a TLD when passed through a special heating process for reading purposes
Trapped electrons rise above their present location into the conduction band
Then, the electrons return to their normal state with the emission of energy in the form of visible light
What records the amount of light emitted by the crystals in a TLD
TLD analyzer
What is the plot that represents the exposure received by a TLD ring dosimeter
Glow curve
Advantages of TLD ring dosimeter
Accurate and reliable
Small and lightweight
Can be worn up to 3 months
Reusable
Disadvantages of TLD ring dosimeter
Readings will be lost if not carefully recorded
Cannot be used as a permanent legal record
The DIS dosimeter is a small ionization gas filled dosimeter connected to a _______________ device
Solid state
In DIS dosimeters, when radiation ionizes the gas in the chamber, the cumulative electric charge is stored in the
EEPROM
The DIS dosimeter is read out through a
USB or wireless
Advantages of DIS dosimeters
Instant access to data
Lightweight
Durable
Disadvantages of DIS dosimeters
Dosimeter must be regularly used
Most common type of radiation survey instruments
Geiger-Muller tube
How do survey instruments respond when coming in contact with ionizing radiation
The charged particles ionize the gas (air) in the detector
What do radiation survey instruments measure
Total quantity of electrical charge resulting from the ionization of that gas or the rate at which the electric charge is produced
Types of gas-filled radiation dectectors serving as field instruments
Ionization chamber (cutie pie)
Proportional counter
GM survey
Requirements for radiation survey instruments
- Portable
- Durable
- Reliable
- Interacts with ionizing radiation similar to how tissue reacts
- Detects all common types of ionizing radiation
- Energy of radiation should not significantly affect the response of the detector
- Cost effective
- Calibrated annually
What instruments measure exposure and exposure rate
Cutie pie and proportional counter
What instrument measured only exposure rate
GM meter
The cutie pie measures what type of radiation
X-rays
Gamma rays
Beta radiation
What ionization detector has the ability to measure a wide range of radiation exposures within a few seconds
Cutie pie
Disadvantages of the cuite pie
Delicate detector
Needs proper warm up time
Cannot be used for typical diagnostic procedures because the exposure times are too short
What type of ionizing radiation is a proportional counter used for
Alpha and beta radiation
What is the primary portable radiation survey instrument for monitoring nuclear medicine facilities
GM Survey meter
Components of GM Survey Meter
Audible sould system that alerts the operator of ionizing radiation
Metal encloses the ionization chamber
Disadvantages of GM Survey Meter
Can provide erroneous readings
Likely to saturate or jam when it is placed in a pulsed high-intensity radiation area
What is used to measure the radiation output from both radiographic and fluoroscopic xray equipment
Ionization chambers
What must be calibrated periodically to meet state and federal requirements for patient evaluation dose
Ionization chamber and electrometer system
Who uses ionization chambers connected to electrometers to perform standards measurements for radiographic and fluoroscopic devices
Medical physicists
What type of monitoring device gives accurate readings as low as 10uSv for xray and gamma rays with energies ranging from 5keV to 40MeV
OSL
What type of monitoring device has color-coding, graphic formats, and body location icons
OSL
What monitoring device destroys stored information during readout process
TLD
What monitoring device is not cost effective for large number of personnel
Pocket ionization chamber
What monitoring device must be calibrated to zero or its initial reading must be recorded each day
Pocket ionization chamber
What type of monitoring device has an immediate readout
Pocket ionization chamber
What type of monitoring device offers complete reanalysis
OSL
What type of monitoring devices are not affected by heat, moisture, or pressure
OSL/TDL
What type of monitoring device provides instant access to reports
Personnel digital ionization dosimeter
