در مرکز پزشکی هسته ای دکتر دباغ – دکتر صادقی در خدمت شما هستیم

1. در مرکز پزشکی هسته ای دکتر دباغ – دکتر صادقی در خدمت شما هستیم مشهد، ملاصدرا 11 ، پلاک 1/4 www.DSNMC.ir Tel:+98(51) 38411524; +98(51)38472927

2. Pulmonary Embolism (cases and a brief review) V. R. Dabbagh Kakhki, M.D. Nuclear Medicine Specialist Associate Professor DSNMC Nuclear Medicine Research Center (NMRC; MUMS) www.DSNMC.ir

4. Pretest ProbabilityEpidemiology • Extremely common subclinically • Found at 70% of autopsies • Clinical diagnosis is extremely inaccurate • Only 33% of patients referred for V/Q scans

5. Pretest ProbabilityEpidemiology • Course of Disease • 11% experience sudden death • Diagnosis is not made in 63% • Have 30% mortality rate • 26%: Diagnosis is made and treated : • 8% mortality rate

6. Clinical assessment • Nonspecific • Either dyspnea or tachypnea occur in 96% • 85% have Po2<80 mm Hg • Clinical symptoms of DVT • Very insensitive and non-specific

7. Approach • Respiratory symptoms • Imaging of the chest for PE • Diagnosis remain uncertain • Venous imaging • Pulmonary angiography

8. Venous imagingContrast Venography • Diagnostic standard of reference for DVT • If negative excludes clinically significant DVT • Induces DVT in as many as 8%

9. Venous imagingUltrasonography • Very sensitive and specific (95%) for DVTs above knee • Less accurate for • Calf & pelvis DVTs • Asymptomatic DVTs (65% sensitive)

10. Pulmonary imagingChest X-Ray • Insensitive and non-specific for PE • Signs suggesting PE • Westermark’s sign • Fleischner sing • Hampton’s hump • Most common signs • Consolidation • Atelectasis • Small pleural effusion • Diaphragmatic elevation • To exclude clinical mimics of PE • For comparison with the V/Q study

11. Pulmonary ImagingV/Q scan • Lungs are composed of • Pulmonary circulation • Segmental distribution • Bronchial circulation • PE is segmental in nature

12. Pulmonary imagingV/Q scan

13. Pulmonary imagingLung Perfusion Scan • Performed with • 99mTc-MAA • Shows regional perfusion of the lungs • Very sensitive for PE

14. Pulmonary ImagingLung perfusion scan • Normal lung perfusion scan virtually excludes PE for practical purposes

15. Pulmonary ImagingLung perfusion scan: Normal

16. Pulmonary ImagingLung perfusion scan • PE causes defects which are • Segmental • Pleural based • Wedge-shaped

17. Pulmonary ImagingLung perfusion scan

18. Pulmonary ImagingLung perfusion scan • Many lung pathologies induce perfusion defects • Ventilation scan and chest X-Rays are mandatory for comparison

19. Pulmonary ImagingVentilation scan • Performed with • 133Xe(80 kev) • A first-breath image(100 kcount) • Equilibrium images • Washout Phase • 81mKr • 99mTc labeled aerosols • 99mTc-DTPA • 99mTc-PYP • 99mTc-Technegas

20. Pulmonary ImagingVentilation scan

21. Pulmonary ImagingVentilation scan

22. Pulmonary ImagingVentilation scan

23. Pulmonary ImagingVentilation scan

24. PE Mimics • Unresolved previous PE(35%) • Intravenous drug abuse • Hilar or mdiastinal involvement(LC) • Other process occurring in the • pulmonary arterial lumen(embolism of other than thrrombus, tumor) • Arterial wall(vasculitis,TB,..) • Vascular anomalies (peripheral coarctation) • Extrinsic compression of pulmonary vessels

25. V/Q Scan Diagnostic Criteria • PIOPED criteria • modified PIOPED II criteria • PISAPED criteria

26. V/Q Scan Diagnostic Criteria • Gestalt interpretation • The experienced nuclear medicine physician may be able to provide a more accurate interpretation of the V/Q scan than is provided by the criteria alone

28. Pulmonary ImagingPIOPED criteria • By comparison of V,Q and chest X-Ray, V/Q study can be categorized as • Low probability for PE • <20% • Intermediate Probability for PE • 20-79% • High probability for PE • ≥80%

29. Pulmonary ImagingLow probability

30. Pulmonary ImagingLow probability

31. Pulmonary ImagingIntermediate probability

32. Pulmonary ImagingIntermediate probability

33. Pulmonary ImagingIntermediate probability

34. Pulmonary ImagingIntermediate probability

35. Pulmonary ImagingHigh probability

36. Pulmonary ImagingHigh probability

37. Pulmonary ImagingHigh probability

38. Pulmonary ImagingSpiral CT scan • Overall sensitivity and specificity • 80-85% and 90-95% • Lower sensitivity than V/Q scan • Not clinically relevant • Indirect CT of the legs after pulmonary imaging • Very promising for DVT detection

39. Assessment For PE

40. Assessment of the clinical probability of PE • Wells’ model: • the most frequently used prediction rule for suspected PE • 7 variables • The Wells’ model seems better suited to rule out rather than to rule in the diagnosis of PE and its performance is likely to be better in clinical settings where the prevalence of the disease is expected to be low

42. Assessment of the clinical probability of PE • Simplified Pisamodel: • Recently, a more precise prediction model • 16 variables • It performs equally well in detecting and in ruling out PE.

44. Clinical algorithm for investigation of patientswith suspected PE

45. Stable Patients Diagnostic strategy in stable patients according to clinical probability of PE

46. Haemodynamically unstable PEDiagnostic strategy in patients with severe hypotension or shock

47. Diagnostic algorithms • PE, when suspected, must be confirmed or refuted to avoid the risks of both over and under treatment: • This requires imaging tests. • Only optimal techniques are recommended. • These are MDCT and V/Q Scan (SPECT) with holistic interpretation.

48. Diagnostic algorithms • In each center, the algorithm applied for the diagnosis of PE must be based upon local circumstances, and first and foremost upon the availability of V/Q SPECT and MDCT.

49. V/Q Scan vs. MDCT • V/Q SPECT carries no risk associated with contrast agent injection • V/Q SPECT gives a much lower radiation burden • V/Q SPECT yields a lower rate of nondiagnostic reports • V/Q SPECT has higher sensitivity at similar specificity • V/Q SPECT allows better estimation of PE extension based upon the functional impact of PE.

50. V/Q Scan vs. MDCT • V/Q SPECT offers considerable advantages over other imaging techniques for the diagnosis of PE. • its high sensitivity and specificity • lower and predictable radiation burden • its suitability for follow-up of patients with PE • research into the natural history of PE