QC Flashcards
Dose calibrator constancy checks must be done
daily
Dose calibrator linearity checks must be performed
quarterly
Dose calibrator accuracy checks must be performed
annually
Accuracy checks must be performed, per 10 CFR 35, with ________ sources with at least one source having an energy between ___________ and ___________ keV.
two
100, 500
Dose calibrator accuracy checks must show agreement with standard source within __________
± 5%
Dose calibrator bias voltage must be __________for standard calibrators and ______________ for PET.
~150 V
~500 V
Beta emitters can’t penetrate the dose calibrator chamber, but produce a secondary signal through the production of __________________ radiation. The dipper construction can / cannot impact the measured activity.
bremstrallung
can
Fo Mo-99 concentration tests, the minimum record retention period is ____________. In addition to the measurement, the record must contain:
3 years
time and date
name of individual performing measure
Mo-99 pig thickness is roughly _________ and has a transmission factor of _________
.6 cm Pb
.497
3 reasons for a Moly test failure:
- External contimantion on outside of moly shield
- Wrong isotope selection
- Worn or dented moly shield, allowing Tc-99m photons to escape
This image is an example of
Moly shield holder and and breakthrough shield.
Mo-99 breakthrough is a _________ event
very rare
Dose calibrator linearity must be tested within this range
highest administered activity
down to 30 uCi
The two most probable modes of dose calibrator failure include
Pressure leak from the chamber
Loss of bias battery voltage on the chamber
Linearity testing can be performed via these two ways
decay or shield test
Most dose calibrator “failures” are due to
operator error
If the voltage test indicates normal chamber voltage and the daily constancy test passed, linearity failure is probably due to
operator error performing the test
With the decay method of linearity testing, 6 common errors are
- Recording time incorrectly (use the same timepiece)
- Failure to zero and background correct before each measurement
- Failure to wait for the reading to stabilize
- Record reading on the lowest possible scale and slow response.
- Failure to anticipate that the last measurement bue occur during normal work hours.
- Failure to reproduce the geometry for each measurement
Linearity testing at each measurement point must be within what acceptance limits?
± 5%
Examples of shield based linearity testing include these systems
Lineator
Calicheck
Fluctuations in the dose calibrator reading during lineator testing will occur
at low activity values as you near 30uCi
This is a _____________ used for ___________
lineator
shield based linearity dose calibrator testing
Multi energy calibration of thyroid uptake probes is done using
Eu-152 source
~.5 uCi, exempt source
Distance of sources used in thryoid probe QC
25 cm
Source used for Chi-Square testing of the thyroid probe
Cs-137
.5 uCi, exempt quantity
These devices are used for
Shield based linearity testing
These sources are used in what detection system?
thyroid probe
The source is located where in these rods?
black tip
What is the black arm used for?
flipped in front and placed against the region to be measured to ensure 25 cm distance
Typical dose calibrator accuracy sources include
Co-57
Ba-133
Cs-137
Co-60
Co-57 sources for the dose calibrator should be replaced approximately
every 4 years due to decay
Dose calibrator sources must have an activity of at least
50 uCi
Two dose calibrator sources with an activity between 100 and 500 keV include
Co-57 (122-136 keV)
Ba-133 (356 keV)
This is an example of a
vial source
You can protect the labeling on a vial source by covering it with
clear tape
A Co-57 vial source usually comes at an activity around
5 mCi
Cs-137 and Ba-133 vial sources for the dose calibrator usually have activities around
200-300 uCi
An example of a typical gamma counter test source
I-129 rod source, .05 uCi, T½ =15.7 Million years
Common supplier of NIST traceable calibration standards
Eckert & Ziegler
Canberra
Common background reading on Ludlum Model 3 Probe
.03 to .04 mR/hr
Threshold for a high radiation area
greater than 100 mRem (1 mSv) / hr at 30 cm from the source or surface
Wipe sample
A sample made for the purpose of determining the presence of removable radioactive contamination on a surface. It is done by wiping, with slight pressure, a piece of soft filter paper over a representative type of surface area. It is also known as a “swipe” or “smear” sample. Minimum recommended sampling area is 10 x 10 cm (100 cm2).
AAPM TG 181 recommends linearity testing be peformed between these ranges
Maximum Activity
1 MBq
According to AAPM TG 181 reproducibility of radionuclide calibrator measurements entails
10 consecutive measurements obtained with a long-lived test source greater than 100 uCi
All measurements within 1% of the average measured activity
(Within .5% for secondary standard radionuclide calibrators)
According to AAPM TG 118, accuracy of secondary standard radionuclide calibrators should be
within ± 2 %
Example of thyroid uptake probe tests
Efficiency (Cs-137 3.17 - 6.33% and Eu-152 5.0-10%)
Chi-squared (Cs-137, 10 1 min counts between 4.1 and 14.7)
Constancy Test (<5% deviation)
(limits are specific to Captus 3000 system)
In spectroscopy with a NaI(Tl) detector with Cs-137, other visible peaks include
Iodine escape peak (30 keV)
backscatter peak (200 keV)
In NM spectroscopy of isotopes with multiple gamma or x-ray emissions, the spectra can show
coincidence summing
The FWHM of a collimator is directly proportional to the ____________ and inversely proportional to the ______________
hole diameter & source to crystal distance
hole length
When measuring intrinsic resolution using a 4-quadrant bar phantom, a typical Tc-99m point source would contain this amount of activity
400 - 800 uCi
For Co-57 flood source, the principal gamma has an energy of ___________ and a typical source (new) activity range is
When measuring intrinsic uniformity, a typical point source may contain
~ 100 uCi (Halama quotes 400 - 800 uCi, but depends on the mfg)
Extrinsic or system uniformity uses this type of source
Co-57 sheet source or Tc-99m water source (planar)
Typical number of counts in extrinsic uniformity test (3 - 15 min)
5 - 15 Million
Typical number of counts in intrinsic uniformity test
5-15 M over 1 to 3 minutes, but depends on the mfg
Which is generally higher, integral or differential uniformity
PMT voltage drift can cause
Peak shift
differences in sensitivity
To create a uniformity correction matrix, you a need a high count image of _________ counts.
The uniformity image can be collected ___________
30 to 100 M (basically ten times the count of the routine flood image to reduce counting statistic variation to < +- 1%
For intrinsic uniformity correction as a calibration you need ____________ and __________
For extrinsic calibration you need ____________, and it is required for each __________
Uniformity correction can
mask underlying problems
Peak _______ for these isotopes ___________
daily
Co-57, Tc-99m and other isotopes used during the day
Test uniformity
each day with 5-15 M counts
(extrinsic is preferred especially on heavily used collimators)
intrinsic flood image tests the detector only - pay attention to the periphery
Resolution testing is performed
once per week with a bar phantom or tri-hole phantom.
Intrinsic (preferred) around 800K counts or extrinsic around 5-10 M
Linearity testing should be performed this often
once per week
intrinsic (preferred) or extrinsic images of 5-10 M
A uniformity correction matrix should be acquired this often
once per month for each isotope used (vendor dependent) with 100 M cts or more typically.
For large area detectors, daily floods should have _________ counts and a count rate _________
10-15 M counts
< 40,000 cps (depending on equipment)
For intrinsic floods with uniformity of 3.5 is __________
Between 3.5 and 5 ___________
Above 5 ______________
ok
repeat flood and see if still marginal, may need to recalibrate
recalibration is necessary
contact physicist if a tube is visible
Two NM accreditation programs
ICANL - international commission for the accreditation of nuclear medicine laboratories (SNM, american society of nuclear cardiology, americal college of nuclear physicians, etc.)
ACR - American college of radiology
Center of rotation check should be performed
monthly
For a LEHR collimatory, the expectivity sensitivity should be
In multiple window spatial registration (Ga-67, 4 point sources at 90, 180, 300 keV) the registraiton should be
within 1 mm over the UFOV
FOR quarterly SPECT phantom studies collect _____ x the counts obtained clinically
2-3
