What is the measured exposure rate shown on the diagram of the GM meter depicted here?
0.017 mR/hr
0.17 mR/hr
1.7 mR/hr
17 mR/hr
170 mR/hr
Which of the following instruments should be used to determine whether all removable contamination has been eliminated?
Geiger-Mueller counter
well counter
dose calibrator
uptake probe
ionization chamber
When performing a room survey with a G-M counter, the technologist should first:
perform a battery check on the counter
calibrate the unit
measure each area designated on the survey diagram
perform a wipe test on each designated area
measure the room background
Which is the maximum exposure rate that can be measured with the G-M meter shown here?
50,000 mR/hr
5,000 mR/hr
500 mR/hr
50 mR/hr
5 mR/hr
When surveying for contamination, which of the following diagrams depicts the correct position of the probe of an end-window GM meter in relation to the surface being monitored?
A
B
C
D
How often must survey meters be calibrated?
daily
before each use
annually
monthly
bi-annually
Which of the following instruments is most appropriate for detecting low-level accidental contamination?
thermoluminescent dosimeter
pocket dosimeter
optically-stimulated luminescence dosimetry
Which of the following radiation monitoring devices is best suited to survey a patient who has received 5.55 GBq of I-131 for therapy?
portable ionization chamber
liquid scintillation counter
In calibrating the survey meter for the nuclear medicine department you discover that it has a 12% error. What is your next course of action?
recommend that it be serviced
throw it away
replace the batteries
use the survey meter as normal
check the high voltage power supply
The average energy required to create an ion pair is:
60 eV
34 eV
5 eV
30 keV
50 eV
An ionization of the entire fixed volume of a gas due to secondary ionization is known as the:
Geiger discharge
Townsend avalanche
proportional effect
internal amplification
inverse gain
How do the sizes of the pulses produced by the collection of ions in he proportional region compare to those produced by an instrument that operates in the ionization region of the gas curve for radiation detectors?
the pulses are in resonance
the pulses are smaller
the pulses are the same size
the pulses are larger
the pulses are affected by pulse pile-up
Gas amplification is a phenomenon associated with instruments that operate in which region of the gas curve for radiation detectors?
recombination
ionization
proportional
continuous discharge
G-M
The output pulse height of a gas detector is, in most cases, dependent upon what?
the quantity of radiation that passes through the gas
number of ions produced in the gas
volume of gas in the detector
pressure of the gas in the tube
type of gas in the tube
A GM counter can identify the energy of the source of radioactivity detected.
True
False
Why is a G-M counter not suitable for quantifying the exposure rate of a high activity spill?
the system is paralyzable at exposure levels greater than 2000 mR/hr
the detector probe cannot be positioned correctly to detect removable activity contained in a spill
the G-M counter is most sensitive to high energy radionuclide sources, which are not commonly used in nuclear medicine
the exposure rate would be overestimated
Which of the following statements is false in regards to ionization survey meters?
the ionization chamber measures current
ionization chambers are energy independent
ionization chambers can measure individual ionization events
ionization chambers are unaffected by deadtime
increasing the pressure of the chamber increases the sensitivity of the device
When is survey meter calibration not necessary?
before first use
after the detector has been serviced for producing QC results outside acceptable limits
after a battery change
What is an advantage of an ionization chamber?
small pulse size produced
requires a calibration factor
sensitive to low levels of activity
changes in temperature and pressure affect the current
can differentiate different types of radiation by varying the window
What is the effect of increasing the temperature of the gas contained in a ionization chamber?
decreases the current produced by radiation interactions in a sealed chamber
decreases the current produced by radiation interactions in an unsealed chamber
increases the current produced by radiation interactions in a sealed chamber
increases the current produced by radiation interactions in an unsealed chamber
increases the current produced by radiation interactions in both sealed and unsealed chambers
What is a disadvantage of a GM counter?
readout is dependent on voltage
sensitive to low activities
can differentiate radionuclides based on their energy
low detection efficiency
not portable