53. NUCLEAR IMAGING: PET

Question 1

1. What does PET stand for?

Answer 1

• Positron Emission Tomography

Question 2

2. What is the difference between SPECT and PET?

Answer 2

IN PET:
- there is an almost-simultaneous detection of
2 gamma (y) photons
- single events can be rejected as noise
- this is why PET scans have a very good Signal to Noise
Ratio compared to SPECT scans

THIS METHOD IS KNOWN AS:
- Coincidence Detection

Question 3

3. What is the Direction of Projection?

Answer 3

• this is a line
• it connects the two Photo Multiplier rubes
• these PMTs recorded the interaction event

Question 4

4. What does Coincidence detection require?

Answer 4

• Ultrafast electronics

Question 5

5. What happens with any detector that records an event?

Answer 5

• this detector opens a gate
• for a very short window of time
• often 5 - 15 nano seconds

Question 6

6. What happens if a Second Detector records an event during this small time window?

Answer 6

• a coincidence event will be recorded

OTHERWISE:
- the initial even is rejected

Question 7

7. In which 2 situations is Noise recorded?

Answer 7

1. WHEN TWO INDEPENDENT EVENTS OCCUR
   
   • within the detection window
2. WHEN A PHOTON IS SCATTERED
   
   • and changes its direction

Question 8

8. What can be said about the sensitivities of the PET Scanner vs the SPECT Scanner?

Answer 8

• the PET Scanner is several orders of magnitude higher
  than that of the SPECT scanner

Question 9

9. What does this image show?

Answer 9

• this is a normal condition of the PET Scanners

Question 10

10. What does this image show?

Answer 10

THE DOT = shows the Annihilation event
= this is when 2 photons are detected
simultaneously

NB:
- this is known as Trues

Question 11

11. What does this image show?

Answer 11

• the Photon is scattered
• the angle that is known shows the Noise

NB:
- this is known as Scatter

Question 12

12. What does this image shows?

Answer 12

• here we have 2 photons
• they are not detected simultaneously

NB:
- this is known as Random

Question 13

13. Where do the photons meet?

Answer 13

• this is the Annihilation Event
• the photons travel in opposite directions
• they meet in the middle
• this is known as the Coincidence

Question 14

14. What do we use PET scans to inspect?

Answer 14

• blood flow
• oxygen intake
• metabolism of organs and tissues

Question 15

15. What 4 issues do we use PET scans to detect?

Answer 15

1. Cancer
2. Heart Problems
3. Brain Disorders
4. Central Nervous System Problems

Question 16

16. At which level do PET scans show problems?

Answer 16

• the cellular level

Question 17

17. What 4 issues do the PET scans analyse at a cellular level?

Answer 17

1. Coronary Artery Disease
2. Brain Tumours
3. Memory Disorders
4. Seizures

Question 18

18. Does this table make sense?

Answer 18

• yes

Question 19

19. What kind of resolution do PET scan images bring forward?

Answer 19

• very high resolution