115 Questions
What type(s) of radiation are being measured when a Geiger counter is used to measure a radioactive source with its cover removed?
Beta/alpha particles and gamma rays
What do radiation interactions in a gas-filled detector create?
Negative electrons and positive ions
Where do the negative electrons migrate to in a gas-filled detector?
Anode
According to the standard of practice, what should the percent energy resolution fall between for Cs137?
10%-20%
If the energy spread for Cs137 is 635 keV to 689 keV at half-maximum, does the instrument have an acceptable percent energy resolution?
8.2%
Where is the region of operation on the voltage-response curve for a Geiger counter?
Geiger muller region
Does pulse mode operation of a gas-filled detector require a high photon flux to produce an accurate reading?
False
What is the function of a collimator?
Absorbs gamma rays going at undesirable angles
What is the most important factor in determining the appropriate matrix size for a digital image?
Resolution
Which of the following is the main difference between an all-purpose and a high-resolution collimator?
Hole diameter
What is the function of a pulse height analyzer?
Determines if an event's energy falls within the energy window
Which of the following can be used as the stopping condition for a gamma camera image?
Information density
True or False: Septal penetration is more of a problem with higher-energy gamma rays than lower-energy gamma rays.
True
What is the appropriate collimator if we want high-quality images of the bones of the hand?
High resolution
What is the function of a scintillation crystal?
Absorbs gamma rays and creates scintillation photons.
What is the purpose of a photomultiplier tube in a scintillation detector?
Convert the scintillation into an electric signal.
What is the minimum time separation required between two radiation events in order for them to be detected as two separate events?
Dead time
Which type of collimator has better resolution at the same object-collimator distance?
Parallel-hole collimator
What mainly determines a gamma camera’s extrinsic resolution?
Resolution of the collimator being used
Which of the following will improve image contrast?
Decreased object-collimator distance
In filtered backprojection, how does the filter work in the reconstruction?
By modifying the amplitude of the spatial frequencies used in the reconstruction
In which SPECT study is it acceptable to acquire with a 180º orbit?
Heart imaging
Which semiconductor material is used in commercial intraoperative probes?
Cadmium zinc telluride (CZT)
What is the purpose of the photomultiplier tube in a scintillation detector?
To convert the scintillation photons into an electronic signal
"Scintillators used for PET have different strengths. BGO has high stopping power for 511 keV photons and therefore maximizes the ________ detected." Fill in the blank.
Total number of coincidences
"Scintillators used for PET have different strengths. LSO has a short decay time, reducing the number of ________." Fill in the blank.
"Random coincidences"
Select the correct incidence type:
Scatter event
In PET scans using CT corrections, is a single correction factor used for all tissues?
False
Is an area of increased activity on the non-attenuation-corrected PET scan always a real hot spot?
False
What type of magnets are generally used in clinical MRI tomographs?
Superconducting magnets
What is required for creating an MR image?
Atoms with an unpaired proton
Is it necessary to administer DTPA in a room with negative pressure?
False
Is Xe 133 gas administered by use of a nebulizer?
False
What type(s) of radiation are being measured when a Geiger counter is used to measure a radioactive source with its cover removed?
Beta/alpha particles and gamma rays
'Baseline shift' and 'pulse pile-up' are most likely to occur in situations with:
High counting rates
'Dead time' is the minimum time separation between two radiation events that is required for them to be detected as two separate events. Is this statement:
True
Which of the following will improve image contrast?
Decreased object-collimator distance
What kind of radiation is being measured when a Geiger counter is used to measure a radioactive source with its cover removed?
Gamma rays
What do radiation interactions in a gas-filled detector create?
Negative electrons and positive ions
Where do the negative electrons migrate to in a gas-filled detector?
Cathode
True or False: Pulse mode operation of a gas-filled detector requires a high photon flux to produce an accurate reading.
True
When a CT scan is used to correct for attenuation in a PET scan, is a single correction factor used for all tissues?
False
Is it always true that an area of increased activity on the non-attenuation-corrected PET scan is a real hot spot?
False
Is it necessary to administer Xe 133 gas by use of a nebulizer?
False
Will baseline shift and pulse pile-up most likely occur in situations with high counting rates?
False
Which type of collimator has better resolution at the same object-collimator distance?
Parallel-hole collimator
What mainly determines a gamma camera’s extrinsic resolution?
Resolution of the collimator being used
Which of the following will degrade contrast?
Decreased object-collimator distance
In filtered backprojection, how does the filter work in the reconstruction?
It modifies the amplitude of the spatial frequencies used in the reconstruction
Which semiconductor material is used in commercial intraoperative probes?
Cadmium Zinc Telluride (CZT)
What is the purpose of the photomultiplier tube in a scintillation detector?
To amplify the radiation signal
'Scintillators used for PET have different strengths. LSO has a short decay time, reducing the number of ________.' Fill in the blank.
Prompt events
'Scintillators used for PET have different strengths. GSO, with its improved energy resolution, allows for a greater exclusion of ____________.' Fill in the blank.
Scatter coincidence
In which of the following SPECT studies is it acceptable to acquire with a 180º orbit?
Heart
True or false: In transmission imaging, one measures photons from an external source that pass through the object.
True
True or false: As many as half of all counts in a SPECT study may have been scattered before being registered in the gamma camera.
True
Which of the following contributes the most to dead time?
Prompt events
What is the purpose of a pulse height analyzer in a scintillation detector?
Identifies pulses within the energy window
Which of the following materials is used in commercial intraoperative probes?
CZT
What function does a collimator serve in a gamma camera?
Absorbs gamma rays going at undesirable angles
Which of the following is a disadvantage of a digital image?
It is aesthetically more pleasing than an analog image
What is the function of a light pipe in the context of a gamma camera?
Improves uniformity of gamma camera flood image
What will improve the collimator's overall sensitivity?
Increasing the hole length
Which type of collimator would be suitable if part of the body being imaged is small compared to the camera’s field of view?
Converging
What is the main cause of non-uniformity in a gamma camera?
PMTs
What determines a gamma camera's extrinsic resolution primarily?
The distance between the collimator and the object being imaged
What function does a position circuit serve?
Determines the position of an event
True or False: Septal penetration is more of a problem with lower-energy gamma rays than higher-energy gamma rays.
False
What type(s) of radiation are being measured when a Geiger counter is used to measure a radioactive source with its cover removed?
Beta particles and gamma rays
Which region of operation on the voltage-response curve is associated with a Geiger counter?
Geiger muller region
What causes the change in charge on one or both plates of a gas-filled detector?
Migration of positive ions and negative electrons
Which type of gas-filled detector requires a high photon flux for accurate readings in pulse mode operation?
Geiger counter
What primarily determines a gamma camera's extrinsic resolution?
Collimator design
What is the purpose of the photomultiplier tube in a scintillation detector?
To amplify the light signals from the scintillation crystal
'Dead time' is the minimum time separation between two radiation events that is required for them to be detected as two separate events. Is this statement:
True
True or False: In transmission imaging, one measures photons from an external source that pass through the object.
True
According to the standard of practice, what should the percent energy resolution fall between for Cs137?
10%-20%
What is the minimum time separation required between two radiation events in order for them to be detected as two separate events?
100 ns
Which of the following can be used as the stopping condition for a gamma camera image?
All of the above
What mainly determines a gamma camera’s extrinsic resolution?
Intrinsic resolution of the collimator
Which type of collimator has better resolution at the same object-collimator distance?
Diverging
What is the function of a pulse height analyzer?
Determines if an event's energy falls within the energy window
Which of the following materials is used in commercial intraoperative probes?
CZT
'Scintillators used for PET have different strengths. BGO has high stopping power for 511 keV photons and therefore maximizes the ________ detected.' Fill in the blank.
Absorption fraction
'Scintillators used for PET have different strengths. GSO, with its improved energy resolution, allows for a greater exclusion of ____________.' Fill in the blank.
Scatter fraction
'Scintillators used for PET have different strengths. LSO has a short decay time, reducing the number of ________.' Fill in the blank.
Scatter fraction
Which of the following will improve image contrast?
Decreased object-collimator distance
In which of the following SPECT studies is it acceptable to acquire with a 180º orbit?
Heart
Which of the following does NOT degrade contrast?
Greater count density
True or false? In transmission imaging, one measures photons from an external source that pass through the object.
True
Which of the following semiconductor materials is used in commercial intraoperative probes?
CZT
The purpose of the photomultiplier tube in a scintillation detector is to:
Convert the scintillation photons into an electronic signal
'Scintillators used for PET have different strengths. LSO has a short decay time, reducing the number of ________.' Fill in the blank.
Prompt events
'Scintillators used for PET have different strengths. BGO has high stopping power for 511 keV photons and therefore maximizes the ________ detected.' Fill in the blank.
Total number of coincidences
'Scintillators used for PET have different strengths. GSO, with its improved energy resolution, allows for a greater exclusion of ____________.' Fill in the blank.
Scatter coincidences
True or false? Attenuation is more of a problem with PET than it is with single-photon imaging.
True
Which of the following is NOT true about the use of a CT scan to correct for attenuation in a PET scan?
A single correction factor can be used for all tissues
Is it always true that an area of increased activity on the non-attenuation-corrected PET scan is a real hot spot?
No
What type of magnets are generally used in clinical MRI tomographs?
Superconducting magnets
True or false: DTPA administration must be done in a room with negative pressure?
False
True or false: Xe 133 gas is administered by use of a nebulizer?
False
When a Geiger counter is used to measure a radioactive source and its cover is removed, what type(s) of radiation are being measured?
Beta, alpha particles, and gamma rays
'Baseline shift' and 'pulse pile-up' are most likely to occur in situations with:
High counting rates
'Dead time' is the minimum time separation between two radiation events that is required for them to be detected as two separate events. Is this statement:
True
Which of the following will improve image contrast?
Use of 2D projections to make a 3D matrix and derive 2D slices
'Creating an MR image requires: Atoms with an unpaired proton.' True or false?
False
In PET scans using CT corrections, is a single correction factor used for all tissues?
True
Is it necessary to administer Xe 133 gas by use of a nebulizer?
False
Will baseline shift and pulse pile-up most likely occur in situations with low counting rates?
False
Is it always true that an area of increased activity on the non-attenuation-corrected PET scan is a real hot spot?
False
Does pulse mode operation of a gas-filled detector require a high photon flux to produce an accurate reading?
True
What determines a gamma camera's extrinsic resolution primarily?
Collimator design
What kind of radiation is being measured when a Geiger counter is used to measure a radioactive source with its cover removed?
Beta/alpha particles and gamma rays
Which of the following contributes the most to dead time?
Pulse generation time
Which of the following will degrade contrast?
Low counting rates.
Study Notes
Radiation Measurement and Detectors
- When a Geiger counter is used to measure a radioactive source with its cover removed, it measures alpha, beta, and gamma radiation.
- In a gas-filled detector, radiation interactions create ion pairs.
- In a gas-filled detector, negative electrons migrate to the anode.
Pulse Height Analyzer and Collimators
- A pulse height analyzer is used to analyze the energy spectrum of radiation.
- A collimator is used to restrict the angle of incidence of radiation on a detector.
- A high-resolution collimator has smaller holes and is used for high-quality images of small objects.
Gamma Cameras and SPECT
- The extrinsic resolution of a gamma camera is mainly determined by the collimator.
- A 180º orbit is acceptable for some SPECT studies.
- In filtered backprojection, the filter works in the reconstruction to reduce noise.
Scintillators and PET
- BGO has high stopping power for 511 keV photons, maximizing detection.
- LSO has a short decay time, reducing the number of random coincidences.
- GSO has improved energy resolution, allowing for a greater exclusion of scattered photons.
Image Contrast and Resolution
- High-energy gamma rays are more susceptible to septal penetration.
- A high-resolution collimator and a large matrix size can improve image contrast.
- Dead time is the minimum time separation between two radiation events required to detect them as separate events.
MRI and X-Ray
- Clinical MRI tomographs use superconducting magnets.
- DTPA administration does not require a room with negative pressure.
- Xe 133 gas is administered using a nebulizer.
Miscellaneous
- Pulse mode operation of a gas-filled detector requires a high photon flux to produce an accurate reading.
- Baseline shift and pulse pile-up occur in situations with high counting rates.
- A position circuit serves to determine the position of radiation detection events.
- A light pipe is used to transmit light from the scintillator to the photomultiplier tube in a gamma camera.
Test your knowledge on gamma camera resolution and collimators with this quiz. Determine whether statements about pinhole and parallel-hole collimators, as well as the extrinsic resolution of a gamma camera, are true or false. Additionally, identify components of background counts in nuclear medicine images.
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