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PET-CT Scan(Principles and Basics)


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introducyion of the Pet/CT machine, its principles, the radiotracer (FDG), SUV....and the application of the PET/Ct in different medical fields

Published in: Technology, Health & Medicine

PET-CT Scan(Principles and Basics)

  1. 1. PRINCIPLES & APPLICATIONS OF PET - CT Presentated BYAbdulkader Helwan Submitted to: Dr. Zafer Topukcu
  2. 2. PET/CT • Medical Imaging Technique • Both systems in one Gantry • Aquired image combined into a coregistered image • Functional imaging by PET • Anatomical imaging by CT-Scanner By Eng. Abdulkader Helwan 2
  3. 3. PET/CT • Combines the functional information with the anatomical detail • Accurate anatomical registration • Higher diagnostic accuracy than PET or CT alone By Eng. Abdulkader Helwan 3
  4. 4. By Eng. Abdulkader Helwan 4
  5. 5. Fused PET/CT images
  6. 6. PET • Stands for positron emission tomography • Machine that can image biological and chemical activities • For ex: imaging brain activity when there is a scary event • Active part of brain can’t be imaged using x-ray of only CT • It can be imaged using PET By Eng. Abdulkader Helwan 7
  7. 7. Principles of PET • Inject a radioactive tracer bind with glucose • The active part of brain absorbs it more than other inactive parts • The radioactive tracer is: Fluorine-18-deoxyglucose (FDG), a radionuclide labeled glucose analogue is injected into the organ that would be imaged 8 By Eng. Abdulkader Helwan
  8. 8. PET tracer: FDG • Fluorodeoxyglucose is a glucose analog. Its full chemical name is 2-fluoro-2-deoxy-D-glucose, commonly abbreviated to FDG. • Radioactive fluoride atom produced in a cyclotron is attached to a molecule of glucose. • The FDG molecule is absorbed by various tissues just as normal glucose would be. By Eng. Abdulkader Helwan 9
  9. 9. FDG CH2HO O HO OH HO OH glucose CH2HO O HO HO OH • Most widely used PET tracer • Glucose utilization • Taken up avidly by most tumours • It is absorbed by various tissues as normal glucose would be. 18F 2-deoxy-2-(F-18) fluro-D-glucose By Eng. Abdulkader Helwan 9
  10. 10. Figure 3. Uptake of FDG. FDG is a glucose analog that is taken up by metabolically active cells by means of facilitated transport via glucose transporters (Glut) in the cell membrane. Kapoor V et al. Radiographics 2004;24:523-543 ©2004 by Radiological Society of North America
  11. 11. FDG Metabolism Glucose Glucose Radioactive Glucose 18F-FDG Glucose FDG Glucose-6Phosphate FDG -6-P X Radioactive Glucose 18F-FDG Unlike glucose, FDG is trapped 11
  12. 12. PET Radiopharmaceuticals Nuclide Half-life Tracer Application O-15 2 mins Water Cerebral blood flow C-11 20 mins Methionine Tumour protein synthesis N-13 10 mins Ammonia Myocardial blood flow F-18 110 mins FDG Glucose metabolism Ga-68 68 min DOTANOC Neuroendocrine imaging Rb-82 72 secs Rb-82 Myocardial perfusion 12
  13. 13. Positron and Photons Emission Kapoor V et al. Radiographics 2004;24:523-543 ©2004 by Radiological Society of North America
  14. 14. Annihilation Reaction • The positron annihilates with an electron to release energy in the form of coincident photons : 15
  15. 15. Coincidence Detection 16
  16. 16. Figure 5. Photograph (frontal view) of a hybrid PET-CT scanner shows the PET ring detector system (red ring). Kapoor V et al. Radiographics 2004;24:523-543 ©2004 by Radiological Society of North America 17
  17. 17. CRYSTALS USED IN PET BaF2 – Barium Flouride(0.8ns) BGO – Bismuth Germinate Oxide(300ns) LSO – Lutetium Orthosilicate(40ns) GSO – Gadolineum Orthosilicate(60ns) YLSO – Yttrium Lutetium Orthosilicate(40ns) 17
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  20. 20. Data Acqusition • The detection of photon pairs by opposing crystals create one event (LOR) • Millions of these event will be stored with in sinograms and used to reconstruct the image • Spatial resolution is determined by the size of crystal and their separation and is typically 3-5mm 22
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  26. 26. Interpretation of Images PET provides images of quantitative uptake of the radionuclide injected that can give the concentration of radiotracer activity in kilobecquerels per milliliter . Methods for assessment of radiotracer uptake – • visual inspection • standardized uptake value (SUV) • glucose metabolic rate 30
  27. 27. SUV • Standardized Uptake Value • The SUV is a semiquantitative assessment of the radiotracer uptake from a static (single point in time) PET image. • Malignant tumors have an SUV of greater than 2.5–3.0, whereas normal tissues such as the liver, lung, and marrow have SUVs ranging from 0.5 to 2.5. • The SUV of a given tissue is calculated with the following formula:
  28. 28. Limitations of PET/CT • FDG is not cancer specific and will accumulate in any areas of high rates of metabolism and glycolysis. • Therefore, increased uptake can be expected in all sites of hyperactivity at the time of FDG administration (e.g. muscles and nervous system tissues); at sites of active inflammation or infection 28
  29. 29. The distribution of FDG within a normal individual (MIP). 31
  30. 30. Physiologic FDG uptake
  31. 31. Figure 17b. Kapoor V et al. Radiographics 2004;24:523-543 ©2004 by Radiological Society of North America
  32. 32. Figure 18. Non-small cell lung carcinoma in a 78-year-old man with enlarged hilar and mediastinal lymph nodes. Kapoor V et al. Radiographics 2004;24:523-543 ©2004 by Radiological Society of North America
  33. 33. Figure 20. Large cell lung cancer in a 54-year-old woman. Kapoor V et al. Radiographics 2004;24:523-543 ©2004 by Radiological Society of North America
  34. 34. Identification of distant metastatic disease Top Tip Evidence suggests that the removal of a solitary adrenal deposit at the time of resection of the lung primary results in an increased life expectancy. Liver, adrenal, brain and bony deposits are common with lung cancer but many of the lesions are undetected in the course of conventional staging
  35. 35. • ASSESSMENT OF TREATMENT RESPONSE Pretherapy and post therapy studies showing a complete metabolic response to therapy.
  36. 36. PET in Neurology The Active Human Brain
  37. 37. Hypo metabolism in left temporal lobe secondary to epilepsy
  38. 38. THANK YOU new ideas make work interesting 40