QC Flashcards by David Miller

Dose calibrator constancy checks must be done

daily

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Dose calibrator linearity checks must be performed

quarterly

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Dose calibrator accuracy checks must be performed

annually

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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

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Dose calibrator accuracy checks must show agreement with standard source within __________

± 5%

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Dose calibrator bias voltage must be __________for standard calibrators and ______________ for PET.

~150 V

~500 V

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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

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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

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Mo-99 pig thickness is roughly _________ and has a transmission factor of _________

.6 cm Pb

.497

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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

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This image is an example of

Moly shield holder and and breakthrough shield.

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Mo-99 breakthrough is a _________ event

very rare

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Dose calibrator linearity must be tested within this range

highest administered activity

down to 30 uCi

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The two most probable modes of dose calibrator failure include

Pressure leak from the chamber

Loss of bias battery voltage on the chamber

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Linearity testing can be performed via these two ways

decay or shield test

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Most dose calibrator “failures” are due to

operator error

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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

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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

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Linearity testing at each measurement point must be within what acceptance limits?

± 5%

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Examples of shield based linearity testing include these systems

Lineator

Calicheck

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Fluctuations in the dose calibrator reading during lineator testing will occur

at low activity values as you near 30uCi

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This is a _____________ used for ___________

lineator

shield based linearity dose calibrator testing

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Multi energy calibration of thyroid uptake probes is done using

Eu-152 source

~.5 uCi, exempt source

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Distance of sources used in thryoid probe QC

25 cm

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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