chapter 4: pet instrumentation Flashcards
setting the ring plane difference to limit the number of contiguous rings that allow coincidence detection may
reduce the wide variation in sensitivity
reduce the wide variation in specificity
decrease the number of detected randoms
increase the number of detected trues
reduce the wide variation in sensitivity
the energy resolution of crystal materials used in pet scanners is relatively
high
poor
variable
different depending on the material
poor
the dominant type of interaction at 511 kev is
characteristic
bremsstrahlung
compton scattering
photoelectric
compton scattering
scatter fraction is dependent on all of the following except
energy window
signal to noise ratio
scatter material geometry and size
specifics of the scanner
signal to noise ratio
NECR =
T^2/(T+S+R)
detector parallax can be described as
a scanner having too few detectors, decreasing sensitivity
the increase in randoms and scatters in 3d mode
interactions taking place at varying crystal depths at the edge of the FOV
mispositioned LORs
interactions taking place at varying crystal depths at the edge of the FOV
when applying a PSF correction, this may affect
scanner sensitivity
SUVs
NECR
signal-to-noise ratio
SUVs
acquiring in list mode is available and advantageous for all of the following except
ToF systems
cardiac gating
respiratory gating
2D mode
2D mode
the use of timing marker information and physiologic gating markers describes
frame mode
list mode
A and B
cardiac gating
list mode
pyramidal sensitivity is most commonly an issue with
overlapping bed positions
continuous bed motion
ToF systems
patients with large body habitus
overlapping bed positions
all of the following contribute to the high-quality image except
Tof acquisition
overlapping bed positions
applying PSF correction
scatter/random fraction correction
overlapping bed positions (continuous is better, more uniform sensitivity)
which is the correct order after image acquisition?
raw data formed into sinograms, recon to axial image slices, apply corrections
raw data formed to sinograms, apply corrections, recon to axial image slices
apply corrections, raw data formed to sinograms, recon to axial image slices
apply corrections, recon to axial image slices, raw data formed to sinograms
raw data formed into sinograms, recon to axial image slices, apply corrections
the most commonly used recon algorithm in pet is
FBP
RAMLA
OSEM
MLEM
OSEM
the typical parameters for reconstructing a pet scan are usually
high number of subsets and high number of iterations
low number of subsets and low number of iterations
low number of subsets and high number of iterations
high number of subsets and low number of iterations
low number of subsets and high number of iterations
all of the following are methods to reconstruct 3D angle sinograms except
SSRB
FORE
RAMLA
full 3D recon
RAMLA
the most common filter used for pet images is the
butterworth filter
gaussian filter
3d filter
scatter fraction filter
gaussian filter
the most common technique for processing 3D sinograms is
FORE
SSRB
full 3d recon
RAMLA
FORE
a very smooth pet scan image will most likely have a filter applied that is
5 mm
7 mm
10 mm
12 mm
12 mm
pet scanners are inherently what type of image?
qualitative
quantitative
3d
2d
quantitative
one issue with applying a PSF correction is
SUVmax is falsely lower
SUVmax is falsely higher
SUVmin is falsely lower
SUVmin is falsely higher
SUVmax is falsely higher
a bright rim of activity around the outside edge of the body indicates
truncation
non-attenuated photons
high voltage drift
low signal-to-noise ratio
non-attenuated photons
the mathematical assumption of uniform attenuation is referred to as the
chi square test
chang technique
point spread function
iterative reconstruction
chang technique
the technique that assumes that the linear attenuation coefficient is the same for all pixels may be used in all of the following areas except the
brain
chest
abdomen
pelvis
chest
transmission sources are most commonly
Cs137 and Ba133
Cs137 and Ge68
Ge68 only
Cs137 only
Cs137 and Ge68
Ge68 is a
beta emitter
alpha emitter
positron emitter
positron and beta emitter
positron emitter
all of the following are true concerning transmission scans for attenuation correction except
has lower radiation exposure compared to CT
transmission image must be transcribed to 511 keV values
takes 20-30 mins
Ge68 or Cs137 may be used
transmission image must be transcribed to 511 keV values
image segmentation refers to
the recon of 3d slices to 2d slices
identifying areas that have similar tissue density
the transcribing of CT data to 511 keV attenuation values
the mathematical assumption of attenuation values
identifying areas that have similar tissue density
replacing pixel values
increases image noise
reduces image noise
prolongs reconstruction
shortens reconstruction
reduces image noise
the scanner measures image radioactivity in
MBq/ml
KBq/ml
mCi/ml
uCi/ml
KBq/ml
SUVbw =
roi tracer concentration (mCi/cc) / (tracer dose (mCi)/patient weight (kg))
