Week 5- Radiation Monitoring Flashcards
What is personnel dosimetry?
The monitoring of equivalent dose to any person occupationally exposed on a regular basis to ionizing radiation
What is one purpose of personnel dosimetry?
Ensures that occupational radiation exposure levels are kept well below annual effective (EfD) limits
When is personnel monitoring required?
Whenever radiation workers are likely to risk receiving 10% of the annual occupational Efd limit in a single year as a consequence of their work
What is 10% of the annual occupational EfD limit?
50 mSv (5 rem)
When do most healthcare facilities issue personnel dosimetry devices?
When personnel could receive 1% of annual EfD limit in any month
What is 1% of annual occupational EfD limit per month?
.5 mSv (50 mrem)
What is the first purpose of personnel dosimeters?
To provide an indication of the working habits/conditions of diagnostic imaging personnel
What is the second purpose of personnel dosimeters?
Determines occupational exposure by detecting and measuring the quantity of ionizing radiation to which the dosimeter has been exposed
What is a common misconception of personnel dosimeters?
Does not protect the wearer from exposure, it is only capable of detecting and measuring ionization
During routing radiographic procedures where should a dosimeter be worn?
Primary personnel dosimeter should be attached to the clothing on the front of the body at collar level
When a protective apron is used where should a dosimeter be worn?
Should be work outside the apron at collar level on the anterior surface of the body
What is the primary dosimeter measuring when its placed at collar level?
Measuring the dose to the thyroid, head and neck
When wearing an apron where should a secondary dosimeter be placed?
Under the apron at waist level
For pregnant personnel, where should the dosimeter be worn?
- Primary dosimeter worn at collar level
- Secondary dosimeter work at abdominal level
What is a type of extremity dosimeter?
A thermoluminescent dosimeter (TLD) ring badge
What is the necessity of a TLD ring?
A second monitor that should be worn when the performing radiographic procedures that require hands to be near primary x-ray beam
What does the laser etched cover of the TLD ring contain?
Personal identification
What record should radiation exposure be a part of?
Part of the employment record of all workers
What values are represented in the employment record?
Values represent the average annual EfD to the whole body
What are characteristics of personnel dosimeters?
- Lightweight and easy to carry
- Made of materials durable enough to tolerate normal daily use
- Able to detect and record both small and large exposures in a consistent manner
- Unaffected by outside influences like weather or humidity
- Are reasonably inexpensive to purchase and maintain
- Permit healthcare facilities to use large numbers of monitors in a cost-effective manner
What are the three most current types personnel dosimeters?
- Optically stimulated luminescence dosimeter (OSL)
- Direct Ion Storage (DIS)
- Extremity dosimeter (TLD)
What is the most common device used for monitoring occupational exposure?
Optically stimulated luminescence dosimeter (OSL)
What does an OSL dosimeter contain?
Aluminum oxide detector
What energy discrimination does an OSL dosimeter contain?
Filters made of aluminum, tin and copper
What is the sensitivity level of OSL dosimeters?
Accurate reading as low as 10 uSv
What are the advantages of OSL dosimeters?
- Lightweight, durable and easily worn
- Preloaded packet
- Allows for reanalysis
What are the disadvantages of OSL dosimeters?
- Occupational exposure is recorded only in the body area where the device is attached
- Exposure cannot be immediately determined
How do OSL dosimeters compare to other devices?
Its the 2nd most sensitive
What are the terms of use for an OSL dosimeter?
Can be used up to 1 year, but its normally worn for 1-3 months
What type of detector does a TLD contain?
Lithium fluoride crystals
How does the detector work in a TLD?
The photon energy is stored until the detector is “read” by heading it
What are pocket ionization chambers?
Pocket dosimeters that resemble a fountain pen
What type of detector does a pocket ionization chamber contain?
Ionization chamber with a built in electrometer
What is the sensitivity level of a pocket ionization chamber?
The most sensitive type of
What are the terms of use of a pocket ionization chamber?
Cannot be used for long-term monitoring. They provide an immediate readout and are used for short term monitoring in high dose situations
How is a Direct Ion Storage Dosimeter set up?
Small ionization gas filled dosimeter is connected to a solid state device with EEPROM
How does a DIS dosimeter work?
Radiation ionizes the gas in the ion chambers and the electric charge stores it until its “read-out”
How is a DIS read out?
It’s read out by physically connecting it to a device where the data can be stored electronically or via an app
What are the advantages of DIS?
- Instant access to data
- Lightweight and durable
- Can be dropped/scratched without harming the device
What are the disadvantages of DIS dosimeter?
Must be worn to be accurate
When a radiation worker changes jobs, what happens to their dose record?
It transfers to the new employer
What are the 3 categories of radiation survey instruments?
- Those without a readout scale
- Those with a readout scale
- Ionization-chamber based
What is the most common detector in radiation survey instruments?
Geiger-Muller tube detector
What does the simplest form of radiation survey instruments provide?
Indicates the presence of radiation above background level
What is one limitation of radiation survey instruments?
They do not provide a cumulative exposure reading
What are the types of instruments used for radiation survey?
Portable devices that can detect and measure radiation in the environment
What do radiation survey instruments respond to?
Respond to the charged particles that are produced by the radiation interacting with and ionizing the gas in the detector
What do radiation survey instruments measure?
Measure either the quantity of electrical charge resulting from the ionization of gas or the rate at which the electrical charge is produced
What do gas filled detectors include?
- Ionization chamber type survey meter (cutie pie)
- Proportional counter
- GM survey meter
What are the requirements for radiation survey instruments?
- Portable
- Durable
- Reliable
- Interacts with radiation like tissues do
- Detect all common types of ionizing radiation
- Is not impacted by energy of the radiation
- Cost effective
- Calibrated annually to ensure accurate operation
How can ionization chambers be used to measure X-ray exposure?
Can be used to measure the radiation output from both radiographic and fluoroscopic X-ray equipment
What is the cutie pie ionization chamber used for?
Radiation protection surveys
What needs to be calibrated periodically to meet state and federal dose evaluation standards?
The ionization chamber and electrometer systems
How do medical physicists use ionization chambers?
Ionization chambers are connected to electrometers to perform stand measurements required by state, federal and health orgs for radiographic devices
What is the primary portable radiation survey instrument used in nuclear medicine?
The Geiger-Muller survey meter
What does the Geiger-Muller Survey meter effective in?
Effective to detect radioactive nuclei or photons to small amounts of radiation
What is the Geiger-Muller survey meter used to detect?
Used to detect radiation from spills, lost radioactive sources, etc
How does the Ginger-Muller survey meter work?
It has an audible signal and a meter to measure the presence of radiation
What is the proportional counter used for?
As a lab instrument to measure alpha and beta particles, NOT for diagnostic imaging
