What's about PET/CT?

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What's about PET/CT?

  1. 1. The Society of Jiraporn Sriprapaporn, M.D.Medical Radiography Nuclear medicineof Thailand Meeting,Pattaya, Thailand Siriraj Hospital5 July 2012
  2. 2. Topics• What is PET?• Evolution of PET/CT• Principle of PET/CT imaging – PET/CT scanners – PET radiopharmaceuticals• Steps of PET/CT imaging• Oncologic applications of PET/CT
  3. 3. What is PET?
  4. 4. Nuclear Medicine Studies PET 3-D Images SPECT 3-D ImagesGamma Camera 2-D Images
  5. 5. What is PET?• PET: Positron emission tomography• PET is the study of human physiology by electronic detection of short-lived positron emitting radiopharmaceuticals.• PET is used to evaluate metabolic, biochemical and functional activity at cellular level of human living.
  6. 6. Historical Perspectives of PET Scan • The first CT scanner was invented in 1972 by1972 British engineer Godfrey Hounsfield & Allan Cormack (later awarded the Nobel Peace Prize)1973 • The first PET camera was built for human studies by Edward Hoffman, Michael M. Ter- Pogossian, and Michael E. Phelps in 1973 at Washington University.1977 • The first whole-body PET scanner appeared in 1977.1980 • 1980The first commercial MRI scanner was produced by Raymond Damadian and Paul Lauterbur.
  7. 7. • The PET/CT scanner was invented by Dr. Ron Nutt and Dr. David Townsend in 1998• Medical Inventions of the year 2000 by Time Magazine• 2001 commercially available
  8. 8. PET Scan Images m y anato led fd e ta i so ack lo ne l P ET aCOLD WARM
  9. 9. BROWN FAThttp://www.nuclearonline.org/Newsletter/CaseStudy905.htm
  10. 10. IntegratedPET-CT Scan
  11. 11. PET-ONLY VS PET-CT• Longer scanning time • Shorter scanning time.• Lower patient throughput • Increase patient throughput• Limited anatomical • Better anatomical details information – Improve diagnostic accuracy • Can combine contrast CT study
  12. 12. PET-CT Imaging PET/CT Scanner PETPatient Radiopharmaceutical
  13. 13. CT PET PET-CTScanners
  14. 14. PET Radionuclides• Positron-emitting radionuclides (emit positron (e+) from nucleus (p excess)• Relatively short half-lives and high radiation energies (compared to general NM imaging)• Produced by cyclotron or generators
  15. 15. CYCLOTRON
  16. 16. Important Positron EmittersPositron Emitters Physical T1/2• C-11 • 20 min• N-13 • 10 min• O-15 • 2 min• F-18 • 110 min
  17. 17. PET Radiopharmaceuticals• F-18 FDG is the most commonly used PET tracer.• F-18 FDG (18F-2-fluoro-2-deoxy-D-glucose) or fluorodeoxyglucose (glucose analogue)• Glucose metabolism
  18. 18. PET IMAGING Steps of PET/CT Imaging• Production of positron- emitting Rdn.• Labeling a selected compound with a positron- CYCLOTRON emitting Rdn.• Administration into a patient RADIOPHARM PREP. (IV, inhalation)• PET/CT Imaging the patient INJ. PATIENT• Reconstruction & display (Quantitation) PET-CT SCANNER COMPUTER
  19. 19. PET/CT Imaging PET-CT Imaging CT PET• Scout CT• CT low mA• PET scan-Non AC• PET-AC• PET(AC)/CT
  20. 20. Display of PET-CT Images MIP MIP: Maximum Intensity Projection
  21. 21. Combined functional &anatomicalinformation
  22. 22. PET Imaging • Detecting (indirectly) positron emission via the detection of both annihilation photons (511 keV) that occur and hit opposite detectors simultaneously • Spatial resolution ~ 4-5 mm FWHM
  23. 23. PET Annihilation Nu e+ annihPET Detector PET Detector e-
  24. 24. PET-CTClinical Applications
  25. 25. The Lifetime Risk of Cancer • SEER Cancer StatisticsM 45% Review, 1975-2009 (http://www.cancer.org/CaF 38% ncer/CancerBasics/lifetime- probability-of-developing- or-dying-from-cancer) • Great Britain, 1975- 2008 (http://info.cancerresearch uk.org/cancerstats/incidenc e/risk/statistics-on-the-M 42% risk-of-developing-cancer)F 39% > 1/3 risk to have cancer in their lifetime
  26. 26. 4 Factors Facilitate Widespread Use of FDG PET/CT Imaging1. Whole-body scanning; great impact for the detection of distant metastatic sites in cancer patients.2. Availability of 18F FDG for hospitals that do not have a cyclotron3. Combined PET and CT images in a single setting (PET/CT)4. The approval of reimbursement for PET/CT using F-18 FDG for most oncologic studies. Endo K et al. 2006
  27. 27. Limitation of using PET/CT in Thailand• Limited availability• Very high cost (higher than MRI)• Very limited reimbursement – Lung cancer: staging NSCLC (prior surgery) – Colorectal cancer: Suspected tumor recurrence Appropriate uses cost-effective
  28. 28. 18F-FDG PET/CT Imaging in Oncology Advantages Disadvantages• Several tumors • Nonspecific for tumor• Whole-body imaging distant types metastasis • Can be false positive for• Function & anatomy infection-inflammation.• High resolution (PET • May be low sen & spec in technique) very small lesions (<0.5• High sensitivity (depends on cm) metabolic activity) • Radiation (low-dose CT• High accuracy (due to scan & PET) combined CT images) • Image artifacts can occur• Good patient tolerance with CT, contrast. – about 30 min, no noise
  29. 29. Mechanism of Tumor Uptake• Malignant cells have increased glucose utilization.• Once in the tumor cells, FDG is converted into FDG-6-phosphate, which is metabolically trapped in the tumor cells.• Thus, PET scan show increased FDG uptake in the tumors.
  30. 30. FDG Metabolism 1 Glycolysis 2 1 2Enz1 = Hexokinase -- PhosphorylationEnz2= Glucose-6-phosphataseTumor cells higher glycolytic rate than normal tissue.
  31. 31. • PET= metabolic imaging• FDG (flourodeoxyglucose) is a glucose analog.• F-18 FDG is the most commonly used PET tracer for oncology.• Mech: Active transport into cells, once intracellular FDG is phosphorylated by hexokinase but FDG cannot enter glycolysis and becomes metabolically trapped in the cells as FDG-6- Phosphate• Tumors increased metabolic activity- increased glycolysis increased FDG uptake
  32. 32. Normal F-18 FDG Distribution• Brain • GI tract• Heart • Bone marrow (postprandial*) • Lymphoid-thymus• Liver • Breast• Kidneys-BL • Gonad• Muscle • Vascular activity
  33. 33. Radiation exposure from PET/CT imaging• Results: Effective dose from whole-body CT is about 18 mSv, comparable to that for a typical diagnostic abdomen and pelvis CT series.• When adding the effective dose from F-18 FDG of about 7 mSv, the effective dose from a PET/CT study is about 25 mSv.• Conclusions: – The effective doses from WB PET/CT studies are similar to that from a diagnostic abdomen and pelvic CT, respectively. – Patients acquiring 2 PET/CT exams a year will receive an equivalent whole-body x-ray dose equal to the 50 mSv annual maximum permissible dose for occupational radiation workers. Vicki Quan et al. JNM 2007
  34. 34. FDG Imaging: Techniques• Fasting at least 4-6 hours prior to FDG-PET study. – FBS 70-110 ng/dl is ideal for FDG-PET• IV. inject 140uCi/Kg of FDG (10-20 mCi)• 45-60 minutes following iv. FDG, PET scan is performed.• Skull base-to-mid-thighs or head-to-toe• PET scan time: 2-3 min/ bed position• CT scan: low mA scan is adequate for attenuation correaction & anatomical localization.• High mA scan is needed for diagnostic CT scan.• Oral contrast and IV contrast (diagnostic CT)
  35. 35. SUV (Standardized Uptake Value)• Semi-quantitative measurement of degree of FDG accumulation in the ROI to the total injected dose and the patients BW. [R41. Lowe VJ, Naunheim KS. Thorax 1998]• Malignant tumors: increased glycolytic rate Concentration in ROI SUV = --------------------------------------- Injected Dose / BW
  36. 36. Clinical Applications of F-18 FDG in Oncologic Patients Jiraporn Sriprapaporn Faculty of Medicine, Siriraj Hospital
  37. 37. Oncologic Indications for 18F-FDG PET/CT• Differentiating benign from malignant lesions• Searching for an unknown primary tumor• Staging known malignancies• Monitoring the effect of therapy on known malignancies• Determining whether residual tumor or posttreatment fibrosis or necrosis• Detecting tumor recurrence, especially in the presence of elevated levels of tumor markers• Selecting the region for tumor biopsy• Guiding radiation therapy planning Delbeke D et al. JNM 2006
  38. 38. PET in Oncology: Common Applications 1. Single pulmonary nodule (SPN) 2. Lung cancer (NSCLC*) 3. Colorectal cancer* 4. Lymphoma 5. Melanoma 6. Esophageal cancer 7. Head & neck cancer 8. Thyroid cancer 9. Breast cancer 10. Cervical cancer* Reimbursed by Thai government // rules
  39. 39. Solitary Pulmonary Nodule • DxCT: – Primary tumor-Rt – Med node –ve • PET-CT (12-06): – Hypermetabolic, SUVmax = 8 Malignant nodule ! – Med node –ve – Distant met-No
  40. 40. PET for N-Staging of NSCLC• CT: Left NSCLC w a pathologic AP window node (N2) (white), and a non-pathologic retrocaval-pretracheal contralateral mediastinal node (N3) (yellow).• PET-FDG images: increased tracer accumulation within both nodes, consistent with metastases.• Thus, PET is more sensitive than CT in detect small hypermetabolic LN metas. www.auntminnie.com
  41. 41. VK 30-5-2012• A 69-year-old male with history lung cancer at RUL (adenocarcinoma) with liver and subcutaneous metastases s/p CMT last 30-3-2012.• PET/CT imaging (30-5-2012) demonstrated widespread metastases: liver, subcutaneous, bone, adrenal, pancreas, soft tissue, peritoneum.• Mild hypermetabolic thyroid nodule. MIP
  42. 42. Adrenal metastasis Axial PET/ CT Scan_AbdomenLiver metastasis 30-5-2012
  43. 43. Rt. Scapular metastasis Axial PET/ CT Scan_Chest 30-5-2012
  44. 44. 30-5-2012Sagittal PET/ CT Scan_Spine metastatses
  45. 45. WB PET Scan_Coronal (BW) 30-5-2012
  46. 46. CS 2012• History: 30-yo male with diffuse large B- cell lymphoma Dx in March 2012, presenting with SVC obstruction.• PET/CT Findings: – 1st study-staging preRx (5-4-12) • Huge hypermetabolic tumor at anterior mediastinum. (SUVmax 18.8) – 2nd study-post CMT (5-6-12) • Marked reduction of tumor size at ant mediastinum with metabolic response. (SUVmax 6.8)
  47. 47. Lymphoma: Pre & Post Treatment 5-4-12 5-6-12
  48. 48. Pre-treatment 5-4-2012Post-treatment 5-6-2012
  49. 49. Colorectal CA w Liver Metas.: pre-post Rx • Figure 4 Patient with colorectal metastases and previous left hemihepatectomy. • A CT shows two hypodense nodules with contrast enhancement. • B PET/CT fusion indicates a metastatic recurrent tumor beside a scar after operation. • C CT after radiofrequency ablation shows a large area without contrast enhancement (arrow). • D PET/CT fusion after radiofrequency ablation indicates complete ablation of the recurrent metastasis with a photopenic lesion.
  50. 50. Colorectal CA w Liver Metas-: Tumor RecurrenceFigure 5• A CT 3 month after radiofrequency ablation shows no sign of local recurrence.• B PET/CT 3 month after radiofrequency ablation demonstrates a local recurrent tumor.
  51. 51. A 62-year-old man with papillary thyroid carcinoma • s/p total thyroidectomy and cervical node dissection on 11-3-07 and resurgery on 14- 7-10 and 3 doses of RAI Rx last on 21-9- 10. • Post-therapeutic I- 131 TBS on 24-9-10 was negative, while Tg was 662.2 ng/ml.
  52. 52. I-131 TBS vs F-18 FDG PETAnterior Posterior MIP Coronal PET
  53. 53. PET/CT Scan (9-11-2010) • Large hypermeta- bolic soft tissue mass at left side of neck, measured 8.5x3.7x1.9 cm. Recurrent thyroid cancer ERT, RFA Tg from 662 2.1 ng/ml on 18-6- 12.
  54. 54. I-123 F18-FDG• A 56-year-old female patient with papillary thyroid carcinoma since 1994 presented in 2002 with a Rt neck mass and rising Tg.• 123I imaging (A) showed left hilar uptake posteriorly but no uptake in the neck.• 18F-FDG PET scan (B) showed multiple metastatic lesions in the neck.• 131I therapy was given and improved her mediastinal disease but there was no uptake in the neck metastases, which were removed surgically.
  55. 55. I-123 WBS F-18 FDG PET-CT• A 63-year-old woman with follicular thyroid cancer.• I-123 WB scan is negative.• F-18 FDG PET-CT shows multiple pulmonary and mediastinal lymph node metastases. Lin FI 2010
  56. 56. Thyroid bed SPC T spine• (A) A 27-year-old man had a total thyroidectomy and left-sided neck dissection for papillary thyroid carcinoma.• A few years later he presented with an abnormally increased thyroglobulin level, but negative WB planar imaging I-131 (image a) and Tc-99m MDP bone scan (image b)• (B) 18F-FDG-PET/CT revealed FDG-avid recurrent disease within the thyroid surgical bed (red arrows), metastatic FDG-avid left supraclavicular node (blue arrow) and bony metastases within the upper thoracic vertebrae (green arrows) Chua S SNM Nov 2009
  57. 57. Incidentally found right thyroid nodule • 55-yo woman with a history of treated lymphoma was sent for surveillance PET/CT imaging. • Hypermetabolic Rt thyroid nodule was incidentally found and proved to be papillary thyroid carcinoma.Sriprapaporn J. Siriraj Med J 2011;63: 207-209
  58. 58. F-18 FDG PET/CT Oncologic Applications 1. Single pulmonary nodule (SPN) 2. Lung cancer (NSCLC*) 3. Colorectal cancer* 4. Lymphoma 5. Malignant melanoma 6. Esophageal cancer 7. Head & neck cancer 8. Thyroid cancer 9. Breast cancer 10. Cervical cancer* Reimbursed by Thai government // rules
  59. 59. Oncologic Indications for 18F-FDG PET/CT• Differentiating benign from malignant lesions• Searching for an unknown primary tumor• Staging known malignancies• Monitoring the effect of therapy on known malignancies• Determining whether residual tumor or posttreatment fibrosis or necrosis• Detecting tumor recurrence, especially in the presence of elevated levels of tumor markers• Selecting the region for tumor biopsy• Guiding radiation therapy planning Delbeke D et al. JNM 2006
  60. 60. FDG-PET - False Negative• Small lesions < 10 mm, not much active• Hyperglycemia, diabetes• High background neoplastic process – Brain tumors, RCC, soft tissue sarcoma• Low grade malignancies – Low grade lymphoma, well-diff DTC – Bronchoalveolar CA and bronchial carcinoid• Tumors high in G-6-phosphatase eg. HCC• Tumors with large amounts of mucin
  61. 61. FDG-PET - False Positive• FDG is not a cancer-specific agent. ! – Infection/Inflammatory lesions • Post-surgical, healing wound, post RT • Sarcoidosis, TB • Abscess, fungal infection • etc.Better to interpret PET and CT scan images together with clinicalinformation to enhance the specificity
  62. 62. Conclusion• Due to presence of FP & FN results, it’s better to interpret PET and CT scan images together with clinical information to enhance the interpretation accuracy. PET + CT + CLINICAL INFO

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