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Rad Protection

Chap 4

QuestionAnswer
Does an ionization chamber survey meter have a wide or narrow range? What is the range? Wide ; 0-1000 mR/hr
Gas-filled radiation detectors are used? As and integration type of ionization chamber
What is a crystal that is used in TLD? lithium floride
What kind of dector can be used to identify an unknown gamma emitter? Multichannel crystal spectrometer
What normally operates in the rate mode? an ion chamber
operation in which region of a gas-filled chamber results in the lowest output? recombination
The resolving time of a radiation dector is the time required: to detect sequential ionizations
THe amt of light emitted by a scintillation phosphor is proportional to what feature of photon energy? absorbed
In thermoluminescence dosimetry, a plot of output intensity versus temp is called a: glow curve
When an accurate measurement of radiation exposure is made in the air, what should be used? ionization chamber
What is a characteristic of a Geiger-Mueller counter? measures counts per min
What is a characteristic of scintillation dectors that are used as survey instruments? can detect individual photons
Sodium iodide is a good gammay ray detector bc: it has a high Z
Compared with Geiger-Mueller counters, scintillation counters: are more sensitive to gamma rays
The signal detector of a gas-filled radiation detector is the: central electrode
-measuring and or detecting radiation dosimetry
-devices that measure radiation dosimeters
When are personnel monitoring devices required? When the personnel might recieve 10% or more of the annual dose limit
What is the annual dose limit? 50 mSv ( 5 rem)
Which area of the body is likely to receive 10-20 times more radiation that the waist? head and neck
What are 5 common characteristics of personal monitoring instruments? lightweight & easy to carry durable able to detect and record small and large exposure in reliable manner; mechanical shock shouldn't affect performance; low in cost
-recommended to wear as a second monitor device when the hands are required to be near the primary beam extermity dosimeter
What are the 3 parts of the film badge? durable & lightweight; assortment of metal filters; film packet
What should be made of a low atomic number to filter out the low energy x-ray and gamma ray? plastic film cover
-allows the measurement of the approximate energy reaching the dosimeter filters
What has a sensity range from 0.1 mSv (10 mRem) to 5000 mSv (500 rem) film badge
What is the instrument used to measure the optical density on the film? densitometer
What are the advandages of a film badge? inexpensive; east to handle; reasonably accurate; provides a permanent record
What are the disadvantages of a film badge? can't be used longer than a month; sensitive to heat and humidity; accuracy is limited to give or take 20%
- provides the best features of traditional film and TLD while elimination some of the disadvantages. OSL
What is the chemical compound within an OSL? aluminum oxide
How is a OSL read? scannde by a laser light; will emit light porportional to the amt of radiation it receives; light is then measured and acheived
What is the readout that an OSL produces? glow curve
What is the range of an OSL badge? 5 keV - 40 Mev
What is the maximum sensitivity of an OSL? 1000 Rem
How long can an OSL badge be worn? What is reccommended? 1 yr ; 2 mths
What time of dosimeter looks like a fountain pen? pocket dosimeters
-works on ionization chambers and the gold leaf electroscope pocket dosimeters
What is the range for pocket dosimeters? 0-200 mR
What are the advantages of a pocket dosimeter? immediate reading, easy to carry, reasonably accurate and sensitive ( but not as accurate as film badge, OSL or TDL )
What are the disadvantages of a pocket dosimeter? expensive, very sensitive to mechanical shock, no permanent record
-uses crystals that can undergo changes in their physcial properties TLD
What is one crystal that is used in TLD? lithium floride
What are the advantages of the TLD? crystals interact with radiation as tissue would; can measure radiation as low as 5 mR; not affected by heat or humidity; can be worn up to 3 mths; more sensitive and accurate than film badge
What are the disadvantages to TLD? inital high cost; readouts must be carefully obtained or results will be lost
What are the two types of field survey instruments? gas filled and scintillation
What type of dector are: ionization chambers, proportional counters, geiger-muller counters? gas-filled detectors
High sensitivity means? that an instrument can detect very low radiation intensities
The larger the chamber... the more gas molecules, the more sensitive
Accuracy is controlled by? the overall design
What are the 7 common requirements an area monitoring device should possess? Lightweight; rugged; reliability & accuracy; simplicity; tissue equivalence; economic
-is used for contamination control in nuclear medicine and portable work geiger-muller counter
- has an audio response geiger-muller counter
What is the range of the Geiger-muller counter? less than 100 mR/ hr
-very popular in clinical radiology cutie pie
what is the range of a cutie pie? 1 mR - 1R
- used to calibrate x-ray machines & is accurate withing + or - 20% cutie pie
-have no realistic use in radiology & used in stationary labortory assay small quantities of radioactivity proportional counters
more accuracy = less sensitivity
How do ionization chambers work? radiation passes through air & ionizes atoms; negative ions are measured & reading is est
- unusable region region of recombination- first stage, very low voltage
- highest accuracy region, second stage, region the ion chamber operate in ion chamber region
-more senstitive region but less accurate, third region, instruments using this range are in a lab setting proportional region
-least accurate but most sensitive; avalanche of electrons are produced from a primary ion;quenching agent ; fourth region geiger-muller region
-not useful, voltage too high; fifth region region og continuous discharge
Out of the 5 regions, which are useful? ion chamber, proportional, geiger-muller
-these devices are used in nuclear medicine and ct scintillation dectors
What can scintillation phosphors be? gases, liquids, solids
Created by: erikasmith28