Extras Flashcards
How do you express the Figure of merit in an equation.
SNR/sqrt(dose)
draw a graph of FOM vs energy and explain why its like that.
bell shaped curve. You want it to be wide. The contrast decreases on the right which makes it go down and reduces on the left due to the high dose.
Nyquist theorem?
is that the sampling frequency should be atleast half the signal frequency
How do you calculate the energy resolution?
ability to determine energy = FWHMX100/No of photoelectrons.
the number of photoelectrons can be determined as equal to the energy
butterworth vs hann filters?
Butterworth cuts off at half maximum. Hann defined as cut off at zero.
compare resolution for SPECT vs PET
spect determined by the collimator and gamma camera intrinsic resolution.
PET: determined by the positron range, detector size (2x as good as spect)
attenuation for SPECT vs PET?
SPECT : determined as the average path from point to body surface.
PET : 2x Spect based on full body thickness.
Sensitivity of SPECT vs PET?
Limited by collimator (you knew that) and full ring open geometry for PET.
Scatter in SPECT vs PET?
35 % only in body boundary. SPECT
PET - 15-40% includes outside body boundary
Draw A QAD
Not all photons interact ( 1st dip)
Photons interact and
COV?
1/sqrt(mean of counts) or SD/MEAN
What are the benefits of TOF
Converges faster and better contrast
MLEM IS ____ but _____
osem is _____
flexible but slow
osem is faster
Intensity of the bremsstralung is proportional to ?
z^2.Z^2/m^2
what is the scattered photon energy?
hv = mc^2 / ((1-costheta) + (1/alpha))
