Instrumentation Review

Region A of this graph represents:

Recombination region

Region B of this graph represents:

Ionization region

Region C of this graph represents:

proportional region

Region D of this graph represents:

Geiger-Muller region

Region E of this graph represents:

continuous discharge

What instruments operate in region B?

ionization chambers

What instruments operate in region C?

Proportional counters

What instruments operate in Region D of this graph?

Geiger Mueller Counter

Basic ionization chambers operate at ______ voltage and collect only ____ ions

low; primary

T/F Basic ionization chambers are very reliable with high amounts of radiation

True

T/F Basic ionization chambers are not reliable with high amounts of radiation

false

T/F: basic ionzation chambers are very precise and accurate

true

What are the 3 types of basic ionization chambers used in NM?

Radiation survey meter “Cutie Pie”

Pocket Dosimeters

Dose Calibrators

T/F: A GM counter is a type of survey meter

false

What is the use of a radiation survey meter/cutie pie?

accurately determining exposure rate from therapeutic dose

Select the correct unit of measurement of a Radiation survey meter/cutie pie

mR/hr

What is the purpose of a pocket dosimeter?

measures total radiation dose during a certain time interval, and provides immediate reading

T/F: A dose calibrator is a type of solid scintilator

false

Which region of the voltage graph does an ionization chamber operate in?

Ionizing region

A dose calibrator is a type of

ionization chamber

What is dead time

The time during which a counter cannot respond to another ionizing event

T/F Geiger-Muller counters are useful when measuring large amounts of radioactivity

false

Which one is more sensitive to radiation?

Geiger-Mueller counter

Survey meter constancy is perfomed

daily

How often should calibration of survey meters be performed?

annually

Constancy (sealed source checks) should be within ___% of each other

10%

An example of a gas filled detector is a

dose calibrator

Constancy on a dose calibrator should be performed

daily (& installation)

Linearity on a dose calibrator should be performed

quarterly (& installation)

Accuracy on a dose calibrator should be performed

annually (& installation)

geometry on a dose calibrator should be performed

installation and repair

Constancy is testing an instruments

reproducibility of measurements of a source of a known activity from day to day

Linearity is testing an instruments

Ability to measure low-high activity doses accurately

Accuracy is testing an instruments

ability to provide a true measure of the activity of radionuclides at different gamma energies

When using the decay method to test linearity, a dose of high activity should be assayed until it decays down to ____ or less

30 uCi

During linearity testing, the calculated activity is 17mCi, and the dose was measured as 19.6. Is this reading within the limit?

no, the dose calibrator should be repaired or checked

How often should Reference Sources be leak tested?

every 6 months

How often should reference sources be inventoried?

every 6 months

If variations in calculated vs measured readings during geometry testing, what should be used?

correction factors

The expected reading for a geometry test on a 5ml syringe was 2.95 mCi.  The actual reading was 2.63 mCi.  What is the percent error?

10.8%

The percent error for a geometry test is 10.8%. Does this instrument need correction factors?

yes

A well counter is a type of:

Solid scintillation detector

What test is performed on an uptake probe to compare the measured variability of a group of measurements?

Chi-square

What is the maximum activity a well counter can count?

1 uCi

What is the formula used to calculate detector efficiency?

# detected events / # source emissions

Voltage calibration for well counters and uptake probes should be performed

daily

Efficiency for well counters and uptake probes should be performed

quaterly

Constancy QC for well counters and uptake probes should be performed

daily

Chi Square testing for well counters and uptake probes should be performed

variably

Voltage calibration QC for well counters and uptake probes is used to

determine the appropriate operating high voltage and amplified gain

Efficiency calibration QC for well counters and uptake probes is used to

evaluate the ability of the instrument to detect radioactive disintegrations

Acceptable Chi-square values are between ___ to ___

0.1 - 0.9

This artifact is called a

star artifact

This artifact is caused by

septal penetration

Septal

As the pinhole collimator is moved farther from the source, the image becomes _______

smaller

As the pinhole collimator is moved closer, the image becomes _______

larger

Converging collimators are used to _____ an image

magnify

All of the following are types of scintillation detectors except

gas

Solid scintillation detectors are most commonly made of

NAI(Tl)

What is the energy of Co-57

122 keV

Image A is an example of

cold PMT tubes

Image A is an example of ____, and is caused by the photopeak being set ____

Cold PMTs; too high

This is an example of

Photopeak correctly positioned - uniform appearece

A flood field uniformty test is performed, identify this image

Hot tubes - photopeak set too high

How often should a flood field uniformity test be performed for a gamma camera?

daily

how many counts should be obtained for a flood field uniformity test for a scintilation camera?

3-5 million counts

A source should be placed _______ away from a camera when testing a gamma camera’s intrinsic uniformity

5 FOV

The problem in this image is most likely caused by

PMT tube failure

The problem in this image is most likely caused by

cracked crystal

The image on the right is an extrinsic flood image. What is the most likely cause of this defect?

Collimator damage

What is spatial linearity?

Ability to produce a uniform image with straight lines corresponding to straight lines in a phantom

How often should spatial linearity be performed?

weekly

Spatial linearity should be performed using a

bar phantom

Spatial resolution is defined as:

Ability to discriminate between two points

Spatial resolution should be checked

weekly

Spatial resolution must be performed with a

bar phantom

The real spatial resolution of a camera is expressed quantitatively as

FWHM

If FWHM is 15keV, what is the energy resolution of Tc-99m?

11%

How do you calculate energy resolution when given the FWHM?

[FWHM / photopeak of isotope] X 100 = Energy resolution

Calculate the sensitivity of a camera that produces 26,657 cpm with a 152 uCi source.  Background is 340 cpm.

173 cpm/uCi

Calculate the sensitivity of a camera that produces 15,600 cpm with a 130 uCi source.  Background is 430 cpm.

116 cpm/uCi

Sensitivity is expressed as

cpm/uCi

How do you calculate DPM?

DPM = net CPM / efficiency

Calculate the DPM of a source that produces 28,078 cpm measusured by a well counter with 35% efficiency. Background is 340 cpm

73,537 DPM

What is this phantom

orthagonal hole

What is this phantom

Hine Duley

What phantom is this

Four Quadrant bar phantom

What phantom is this

Parallel-Line Equal Spaced Phantom (PLES)

What is the most commonly used bar phantom

4 quadrant

What are the advantages of SPECT

• Improves image contrast

• Separates overlapping structures

• Ability to assess attenuation

• 3-D representation of the organ surface or “volume” can be rendered.

Field Uniformity testting for SPECT camera should be perfomed

daily

Field uniformity testing for a SPECT camera should have less than ___% differences

<5%

How often should the COR check be performed?

At least weekly

What artifact is caused by detector non-uniformity in SPECT imaging?

Bullls-eye or ring artifacts

What is the minimum number of counts that should be obtained in a uniformity correction flood for a SPECT camera?

30 million

Ramp filters primarily:

Erases blurring from filtered back projection

Hanning Filters are used for

smoothing (noise reduction)

Butterworth filters are used for

Smoothing (reducing noise)