Nuclear Medicine

Question 1

What isotopes are used for Nuclear Imaging

Answer 1

99 Tc-m (gamma)
131 I (beta plus)

Question 2

What does a collimator do (NM)

Answer 2

Selects photon direction
High collimation = high spatial res
// = same image size
Converge = bigger

Question 3

What are good qualities of a scintillator

Answer 3

High Z (high efficiency)
Transparent to its own emitted light
Light wavelength matches photomultiplier sensitivity

Question 4

What does a photomultiplier do

Answer 4

Photos interact with cathode —> electrons
Electrons accelerated towards dynodes
Electrons extract more electrons from dynodes
Creates amplified pulse at anode

Question 5

What does pulse height analysis do

Answer 5

Discriminate scattered and direct photos (Compton scattering) which improves spatial res

Question 6

What is SPECT

Answer 6

Gamma emitters
Info collected by rotating a camera 360°

Question 7

How is SPECT conducted

Answer 7

1. Detector is collimated
2. Set of // projections obtained
3. Filter backprojection/iterative methods

Question 8

What is photon attenuation

Answer 8

Incorrect reconstruction due to attenuation

Question 9

How is photon attenuation corrected

Answer 9

Measure emission intensity
Consider measurement from opposite direction
Create a geometric average
(Only works for uniform objects)

Question 10

How does PET work

Answer 10

Beta + emitter
Position annihilates electron and produces 2 photons in opposite directions
Detected by 2 opposite detectors
Creates line of response between 2 detected photons
Reconstructed by grouping // LORs and using CT algorithms

Question 11

PET artifacts

Answer 11

1. Random coincidence
2. In plane scatter
3. out of plane scatter