L 12

1. L 12 SPECT/CT TECHNOLOGY & FACILITY DESIGN

2. Answer True or False • The most common isotope used in SPECT/CT scans is 18F • SPECT scanners work by detecting coincidences of two 511 keV gamma rays • The facility design concepts are almost identical to those used in designing PET/CT facilities Radiation Protection in PET/CT

3. Objective To become familiar with basic SPECT/CT technology, and review considerations in establishing a new SPECT/CT facility Radiation Protection in PET/CT

4. Content • SPECT cameras • Image Quality & Camera QA • SPECT/CT scanners • Design of SPECT/CT facilities Radiation Protection in PET/CT

5. 12.1 SPECT cameras

6. Scintillators Density Z Decay Light Atten . (g/cc) time yield length (ns) (% NaI) (mm) Na(Tl) I 3.67 51 230 100 30 BGO 7.13 75 300 15 11 LSO 7.4 66 47 75 12 GSO 6.7 59 43 22 15 • Na(Tl) I works well at 140 keV, and is the most common scintillator used in SPECT cameras Radiation Protection in PET/CT

7. Scintillation detector Amplifier PHA Scaler Radiation Protection in PET/CT

8. Pulse height analyzer Pulse height (V) UL LL Time The pulse height analyzer allows only pulses of a certain height (energy) to be counted. counted not counted Radiation Protection in PET/CT

9. Pulse-height distributionNaI(Tl) Radiation Protection in PET/CT

10. Semi-conductor detector as spectrometer • Solid Germanium or Ge(Li) detectors • Principle: electron - hole pairs (analogous to ion-pairs in gas-filled detectors) • Excellent energy resolution Radiation Protection in PET/CT

11. Comparison of spectrum from a Na(I) scintillation detector and a Ge(Li) semi-conductor detector Knoll Radiation Protection in PET/CT

12. Gamma camera Used to measure the spatial and temporal distribution of a radiopharmaceutical Radiation Protection in PET/CT

13. Gamma camera(principle of operation) Position X Position Y Energy Z PM-tubes Detector Collimator Radiation Protection in PET/CT

14. GAMMA CAMERA Radiation Protection in PET/CT

15. PM-tubes Radiation Protection in PET/CT

16. Gamma camera collimators Radiation Protection in PET/CT

17. Gamma cameraData acquisition • Static • Dynamic • ECG-gated • Wholebody scanning • Tomography • ECG-gated tomography • Wholebody tomography Radiation Protection in PET/CT

18. ECG-gated acquisition R Interval n Image n Radiation Protection in PET/CT

19. Scintigraphy seeks to determine the distribution ofa radiopharmaceutical Radiation Protection in PET/CT

20. SPECT cameras are used to determine the three-dimensional distribution of the radiotracer Radiation Protection in PET/CT

21. Tomographic acquisition Radiation Protection in PET/CT

22. Tomographic reconstruction Radiation Protection in PET/CT

23. Tomographic planes Radiation Protection in PET/CT

24. Myocardial scintigraphy Radiation Protection in PET/CT

25. ECG GATED TOMOGRAPHY Radiation Protection in PET/CT

26. 12.2 Image Quality & Camera QA

27. Factors affecting image formation • Distribution of radiopharmaceutical • Collimator selection and sensitivity • Spatial resolution • Energy resolution • Uniformity • Count rate performance • Spatial positioning at different energies • Center of rotation • Scattered radiation • Attenuation • Noise Radiation Protection in PET/CT

28. SPATIAL RESOLUTION Sum of intrinsic resolution and the collimator resolution Intrinsic resolution depends on the positioning of the scintillation events (detector thickness, number of PM-tubes, photon energy) Collimator resolution depends on the collimator geometry (size, shape and length of the holes) Radiation Protection in PET/CT

29. SPATIAL RESOLUTION Object Image Intensity Radiation Protection in PET/CT

30. Resolution - distance High sensitivity High resolution FWHM Radiation Protection in PET/CT

31. SPATIAL RESOLUTION - DISTANCE Optimal Large distance Radiation Protection in PET/CT

32. Linearity Radiation Protection in PET/CT

33. NON UNIFORMITY Radiation Protection in PET/CT

34. NON UNIFORMITY Cracked crystal Radiation Protection in PET/CT

35. NON-UNIFORMITY (Contamination of collimator) Radiation Protection in PET/CT

36. NON UNIFORMITYRING ARTIFACTS Good uniformity Bad uniformity Difference Radiation Protection in PET/CT

37. NON-UNIFORMITY Defect collimator Radiation Protection in PET/CT

38. COUNT RATE PERFORMANCE (IAEA QC Atlas) Radiation Protection in PET/CT

39. Spatial positioning at different energies Intrinsic spatial resolution with Ga-67 Point source (count rate < 20k cps); quadrant bar pattern; 3M counts; preset energy window widths; summed image from energy windows set over the 93 keV, 183 keV and 296 keV photopeaks. (IAEA QC Atlas) Radiation Protection in PET/CT

40. Spatial positioning at different energies Radiation Protection in PET/CT

41. Center of Rotation Radiation Protection in PET/CT

42. Tilted detector Radiation Protection in PET/CT

43. Scattered radiation Scattered photon photon electron Radiation Protection in PET/CT

44. The amount of scattered photons registered Patient size Energy resolution of the gammacamera Window setting Radiation Protection in PET/CT

45. PATIENT SIZE Radiation Protection in PET/CT

46. Counts 140 120 100 80 Tc99m 60 40 20 0 120 100 140 160 20 60 Energy Pulse height distribution Full energy peak Scattered photons The width of the full energypeak (FWHM) is determined by the energy resolution of thegamma camera. There willbe an overlap between thescattered photon distributionand the full energy peak,meaning that some scatteredphotons will be registered. FWHM Overlappingarea Radiation Protection in PET/CT

47. Window width 20% 40% 10% Increased window width will result in an increased number ofregistered scattered photons and hence a decrease in contrast Radiation Protection in PET/CT

48. SCATTER CORRECTION Radiation Protection in PET/CT

49. ATTENUATION Register 1000 counts Origin of counts I=I0 exp(-µx) Radiation Protection in PET/CT

50. ATTENUATION Contrast (2cm object) 23% 7% 2% Radiation Protection in PET/CT