Nuclear Medicine

Question 1

What is the radioactive decay equation?

Answer 1

dN/dt = -λN

Question 2

What are the relative activities for imaging/therapy compared to non-imaging diagnostic?

Answer 2

Imaging/therapy ~ 50 MBq - 10 GBq
Non-imaging diagnostic ~ 1 - 50 MBq

Question 3

What is the equation for the half life?

Answer 3

t_(1/2) = ln(2) / λ

Question 4

What is the geometric mean?

Answer 4

I_G = SQRT(I_1xI_2)

I_1,I_2: the counts recorded from opposing directions for a particular line

Question 5

(a) What is an example of a smoothing filter?
(b) What is the purpose of a smoothing filter?

Answer 5

(a) 1 2 1
2 4 2
1 2 1
(b) Reduce the pixel-to-pixel variation
Reduce noise

Question 6

What is the purpose of the pulse height analyser?

Answer 6

Determine the recorded events where:
1. The γ photon has NOT been scattered in the patient = good event
2. The γ photon has been Compton scattered in the patient = bad event
Allows spectroscopic imaging which only selects events within a particular energy range

Question 7

What is the difference between PET and gamma cameras?

Answer 7

Full ring of detectors rather than a rotating head
PET is not a standalone modality used in conjunction with CT/MR
No ‘collimators’ in PET
Energy resolution in PET poorer than in gamma camera

Question 8

What is the criteria for PET scintillators?

Answer 8

Short scintillation due to no attenuation from collimators e.g. LSO and LYSO