Characteristic curve
Graph that represents response of an IR to a probe.
Film-screen characteristic curve plots the _____ of the developed film on the _____ axis as a function of the exposure on the horizontal axis.
optical density, vertical
Densitometer
instrument used to determine amount of radiation that a film badge has been exposed to
Extremity dosimeter
device that monitors equivalent dose of radiation to the hands
Film badges
economical type of personnel monitoring device. Records radiation exposure accumulated by radiosensitive film at a low rate over a long period of time
Geiger-Muller (GM) detector
device that detects individual radioactive particles or photons. serves as a primary radiation survey instrument for area monitoring in nuc. med. facilities
Glow curve
- graphical plot that demos the relationship of light output, or emitted thermoluminescence intensity, to temperature variation
- curve represents a unique signature of exposure by TLD badge
Ionization chamber-type survey meter (cutie pie)
- exposure rate meter device normally used for area surveys as well as accurate integrating or cumulative exposure instrument
- measures x-radiation and gamma radiation
Optical density
intensity of light transmitted through a given area of film, compared to intensity of light transmitted originally
Optically stimulated luminescence (OSL) dosimeter
- device for monitoring occupational exposure that contains an aluminum oxide detector
- read using laser light at selected frequencies
- becomes luminescent in proportion to amount of radiation received
Personnel dosimeter
- device that provides indication of working habits and conditions of diagnostic imaging personnel
- determines occupational exposure by detecting and measuring quantity of ionizing radiation
Personnel dosimetry
monitoring of radiation exposure of any person occupationally exposed to ionizing radiation on a regular basis
Personnel monitoring report
written report of occupational radiation exposure of personnel prepared by a monitoring company
Pocket ionization chamber (pocket dosimeter)
- personnel monitoring device that contains a positively and negatively charged electrode
- when exposed to ionizing radiation, air around positively charged electrode is ionized and discharges the mechanism in proportion to amount of radiation received
Proportional counter
radiation survey instrument generally used in a lab to detect alpha and beta radiation and other types of radiation
Radiation-dosimetry film
radiographic film in a film badge that is sensitive to doses ranging from 0.1 mSv (10 mrem) - 5000 mSv (500 rem)
Radiation survey instruments
area monitoring devices that detect and measure radiation
Thermoluminescent dosimeter (TLD)
- personnel monitoring device that contains lithium fluoride as sensing material
- crystals emit visible light in proportion to amount of radiation received
TLD analyzer
device that measures amount of ionizing radiation to which a TLD badge has been exposed
Personnel dosimetry
monitoring of persons regularly exposed to radiation
Personnel dosimetry is required when...
workers are likely to receive more than 10% of annual dose limit of 50mSv/5rem
Purpose of personnel monitoring
- measures and detects amount of radiation received
- indication of working habits and conditions
Dosimeter Placement
Routine Radiographic Procedures
- when protective apron is not being worn
- front of body, at collar level
Dosimeter Placement
With a Protective Apron
- outside apron, at collar level
Dosimeter Placement
As 2nd monitor with apron
1st - outside apron at collar level
2nd - under apron at waist level
Dosimeter Placement
Monitor for Embryo-Fetus
- primary monitor - at collar level
- 2nd monitor - at abdomen level
Extremity Dosimeter
Measures exposure to hands
Worn on finger as 2nd monitor
5 Characteristics of Personnel Dosimeters
- lightweight and easy to carry
- durable
- detect/record small and large exposures
- not effected by temperature/humidity
- inexpensive to purchase and maintain
4 types of personnel dosimeters
- film badge
- optically stimulated luminescence dosimeter (OSL)
- Pocket ionization chamber
- thermoluminescent dosimeter (TLD)
Film badges record...
whole body exposure at a low rate over a long period of time
Film badge sensitive to doses from...
0.1 mSv - 5000 mSv
Film badge doses less than...
0.1 mSv are not usually detected
Film badge parts
plastic film holder, film packet, metal filters
Film Badge
Plastic Film Holder
- durable and lightweight
- made of low atomic number material
Film Badge
Film Packet
- outside of packet forms an envelope for film
- film backed by lead to absorb scatter
- radiation exposing film causes blackening
- density of filters on film proportional to amount of radiation received and the energy of the radiation
Film Badge
Metal Filters
- located inside plastic holder
- made of aluminum or copper
- measures energy of radiation by density and appearance of filter image/shadow cast after processing
Film Badge Advantages
- permanent legal record of exposure
- economical, inexpensive, not easily damaged
- monitors x, gamma, beta radiation
- able to discriminate between types of radiation
Film Badge Disadvantages
- sensitive to temperature, humidity, shock
- exposure not determinable on day of occurance
Optically Stimulated Luminescence Dosimeter (OSL)
- most common
- combines best features of film badge and TLD
OSL sensitivity ranges
X ray and gamma = 1 mrem - 1000 rem
Beta = 10 mrem - 1000 rem
Neuron = 20 mrem - 25 rem
OSL Components
- sensing material holder
- water resistant blister pack
- preloaded detector packet containing several different filters
OSL measures radiation exposure through a thin layer of ______ and different filters
Aluminum oxide film
Each filter in an OSL ______ a portion of aluminum oxide film
blocks
OSL - process of exposure assessment
- during processing, aluminum oxide film is stimulated with a blue-laser causing it to become luminescent
- luminescence is proportional to amount of radiation received during use
OSL advantages
- lightweight, durable, easy to carry
- not sensitive to heat, moisture, shock
- can be used up to 1 year
OSL disadvantages
exposure not determinable on day of occurence
Pocket Ionization Chamber (Pocket Dosimeter)
- most sensitive type of personnel monitoring device
- uncommon in diagnostic imaging
- more time consuming to use
- looks like pen and contains thimble ionization chamber
Types of Pocket Dosimeters
- self reading; built in electrometer
- non- self reading; seperate electrometer to read device
Both require special charging unit
Pocket Dosimeters Parts
- 2 electrodes
- central wire anode
- ionization chamber
- metal coated quartz fiber
- special charging unit - quartz fiber must be zeroed
Pocket Dosimeter
Process of Exposure Assessment
When exposed to ionizing radiation...
- electrodes ionize and discharge mechanism in proportion to amount of radiation received
- fiber indicator moves along scale showing amount of exposure in mR
Pocket Dosimeter Sensitivity Range
0 - 200 mR
Pocket Dosimeter Advantages
- compact, convenient, easy to carry
- sensitive to primary and secondary radiation
- accurate and immediate reading
Pocket Dosimeter Disadvantages
- expensive
- no permanent legal record of exposure
- subject to shock, misreading
Thermoluminescent Dosimeter Components
- plastic case holder
- LiF crystals as sensing material
- various filters to differ between types of radiation
TLD Exposure Assessment
- contains lithium fluoride crystals
- radiation excites LiF crystals and energy is stored
- crystals are passed through a heating process and energy is released in the form of light
- intensity of light is proportional to TLD badge exposure
TLD advantages
- interacts w/ radiation similar to human tissue
- more sensitive and accurate doses than film badge
- measures exposures as low as 5 mR
- not sensitive to temp. humidity
- worn up to 3 months
- reusable crystals
TLD disadvantages
- initial high cost
- read only once
Control Badge
- basis for comparison against other badges upon return to monitoring company
- kept in control
- density reading should be zero
Personnel Monitoring Report
- written report of radiation exposure of personnel prepared by the monitoring company
Personnel Monitoring Report records doses in ...
mrem
Radiation Survey Instruments for Area Monitoring Purpose
detect presence or absence of cumulative intensity of radiation
Radiation Survey Instruments for Area Monitoring Requirements
- portable
- reliable readings
- interacts with radiation similar to human tissue
- detect all common radiation types
- not affected by energy or direction of radiation
- cost effective
- calibrated annually
Gas Filled Radiation Survey Instruments Process
- radiation ionizes gas in chamber
- releasing electrons
- electrical signal is then measured
- detect presence or absence of radiation
3 types of survey instruments
ionization chamber-type survey meter
proportional counter
geiger-muller detector
Ionization Chamber Type Survey Meter (Cutie Pie) Measures...
- exposure rate used for area surveys
- cumulative exposure
- x, gamma, beta radiation
Cutie Pie ranges
rate mode - measures intensities ranging from 1 mR/hr to several 1000 mR/hr
Integrate sum mode = 1 mR to several R
Cutie Pie Advantage
measures within seconds
Cutie Pie Disadvantages
- delicate detector
- large size
- needs to warm-up
Proportional Counter
- serves no purpose in diagnostic imaging
- used in lab setting to detect low level radioactive contamination and alpha and beta radiation
Geiger Muller (GM) Detector
serves as portable radiation survey instrument for area monitoring in nuc med facilities
GM sensitivities
detects...
- particles emitted from radioactive nuclei except for alpha particles
- area contaminated by radioactive material
- lost radioactive source
GM components
- audible sound system
- reads in mR/hr
GM disadvantages
- different energies cause different readings
- jam in high intensity radiation areas