1. Function and Structure in
Nuclear Medicine

2. Nuclear Medicine
• Radioactive material is administered into the patient
body
• Photons emitted in the patients are detected by a
scintillator
• Distribution of the radioactivity in the patient body is
reconstructed from projections

3. Maria Składowska-Curie (1867-1934)
Radioactivity
Maria Składowska-Curie ( )

4. Radioactivity
Process that involves the nucleus

5. Radioactivity
Energy state of nucleus changes

6. Radioactivity Decay scheme diagram for 14C
Transition
energy
• Numbers of protons and neutrons change
• b- particle is emitted

7. Radioactivity Decay scheme diagram for 14C
14C is not good for imaging because the decay does
not produce photons

8. Nuclear Medicine
• Radioactive material that emits photons is administered
into the patient body
• Photons coming in the patients are detected by a
scintillator
• Distribution of the radioactivity in the patient body is
reconstructed from projections

9. Radioactivity Decay scheme diagram for 14C
14C not only does not produce useful photons
but also its half-life is 5730 years

10. Nuclear Medicine
• Radioactive material with half-life in order of few hours that emits photons is administered into the patient body
• Photons coming in the patients are detected by a
scintillator
• Distribution of the radioactivity in the patient body is
reconstructed from projections

11. Decay scheme diagram for 133Xe

12. Decay scheme diagram for 133Xe
Half-life 5.2 days

13. What about positron emitters ?

14. Decay scheme diagram for 18F

17. Nuclear Medicine
• Radioactive material with half-life in order of few hours that emits gamma photons is administered into the patient body
• Photons coming in the patients are detected by a
scintillator
• Distribution of the radioactivity in the patient body is
reconstructed from projections

18. Detection
• Photon energy cannot be too high because photons would have too high penetration
• Hard to detect
• Safety issues
• Photon energy cannot be too low because photons would have too low penetration

19. Nuclear Medicine
• Radioactive material with half-life in order of few hours that emits gamma photons is administered into the patient body
• Photons with energies ranging from 50 keV to 600 keV coming in the patients are detected by a scintillator
• Distribution of the radioactivity in the patient body is
reconstructed from projections

20. Gas Filled Detectors

21. Solid State Detectors

22. Scintillation Detectors
Nuclear Medicine uses scintillation detectors
Interaction of a gamma photon with the crystal produces visible light (several hundred photons)

23. Interacción de la radiación con la materiaEF
Recombinación EC
Fotones primarios
Aniquilación CP EF
Ionización Excitación Bremsstrahlung
e- -Auger

24. Scintillation Detectors

25. Efecto Compton

26. Efecto Compton
Detector

27. Efecto Compton

28. Crystals Commonly used in NM

29. Detector de Rayos X
Si PIN diodo
MCA

30. Detector de Rayos X
Si PIN diodo
Full-Width Half-Maximum

31. Direction of incoming photon
Photomultiplier tubes
Crystal

32. Direction of incoming photon
Photomultiplier tubes
Crystal
Lead collimator

33. Direction of incoming photon
Photomultiplier tubes
Crystal
Lead collimator
The ambiguity is resolved by performing tomography i.e. rotating detector around patient

34. Single Photon Emission Tomography

35. Single Photon Emission Computed Tomography
SPECT
Typically:
• 60 projections are acquired around patient over at least 180°
• It takes 1 minute per projection to acquire enough photon counts

36. 2 detector camera

37. 3 detector camera

39. SPECT is not a very efficient technique

40. SPECT is not a very efficient technique
• Only 1 in every 10,000 gamma photons is detected
• Resolution is only about 1cm

41. Positron Emission Tomography (PET)

42. PET
SPECT

43. PET

45. PET
PET
SPECT

46. Examples of NM images
SPECT Cardiac Imaging
•Perfusion
•Viability

47. Cardiac SPECT

48. Cardiac SPECT

49. Brain SPECT primary photon (collimator response)
scattered photon (scatter and collimator response )
absorbed photon (absorption)

50. Brain SPECT primary photon (collimator response)
scattered photon (scatter and collimator response )
absorbed photon (absorption)

51. Brain SPECT

52. Brain SPECT
Frontal Lobe Dementia

53. Oncology PET – 18FDG 57 years old male, Lung Nodule D 1 cm
Hypermetabolic nodule : cancer
No adenopathy, no metastasis : possible surgery
FDG : 15 mCi ; 15 min

54. 57 years old male, lung cancer Ganglionary hepatic and bony metastases
Oncology PET – 18FDG
57 years old male, lung cancer
Ganglionary hepatic and bony metastases
FDG : 5 mCi ; 7 x 7,5 min

55. Oncology PET – 18FDG 68 year old male, pancreatic cancer and melanoma
Ganglion, bone and diffuse metastases
FDG : 10 mCi ; 13 min

57. Is there an ideal Nuclear Medicine camera ?

58. Is there an ideal Nuclear Medicine camera ?
•Electronic collimation
•Single photon emitter

59. Is there an ideal Nuclear Medicine camera ?
•Electronic collimation
•Single photon emitter
Yes, there is

61. Compton Camera

62. Physics 101-Compton Scattering

63. Physics 101-Compton Scattering

64. Gamma photon is scattered
and deposits energy E
Scattered gamma
photon is detected

70. Challenges still to overcome
• Detector 1 need to have VERY good energy resolution
Solid state (semiconductor) detectors
need to be used

71. Challenges still to overcome
• In order to reconstruct the distribution of radioactivity from “Compton cones” HUGE
inverse problem needs to be solved