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Radionuclide Pulmonary imaging (LUNG V/Q SCAN)

Radionuclide Pulmonary imaging (LUNG V/Q SCAN). Dr Hussein Farghaly Nuclear Medicine Consultant RMH. ACUTE PULMONARY EMBOLISM. CLINICAL PRESENTATION: (Non-specific) Haemoptysis , Dyspnea and Pleuritic Chest pain ( Virchows triad)

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Radionuclide Pulmonary imaging (LUNG V/Q SCAN)

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  1. Radionuclide Pulmonary imaging(LUNG V/Q SCAN) Dr Hussein Farghaly Nuclear Medicine Consultant RMH

  2. ACUTE PULMONARY EMBOLISM CLINICAL PRESENTATION: (Non-specific) • Haemoptysis, Dyspnea and Pleuritic Chest pain (Virchows triad) • Back or Abdominal pain, cough, SOB, Low-grade fever,---------- • May be asympotmatic

  3. Evaluation • ABG – Respiratory alkalosis, hypoxia • ECG – Sinus tachycardia & S1Q3T3 • D-Dimer • CXR • Spiral CT with contrast • V/Q Scan • Angiogram

  4. Question 1 Pulmonary angiography as “gold standard” Sensitivity for PE is: • 97% • 93% • 87%

  5. Question 2 Accuracy of V/Q scan in PIOPED – incorrect answer? • 98% sensitivity • 10% specificity • High-probability V/Q scans as PE criteria: Failed to detect PE in 59% of patients • 70% specificity

  6. Question 3 Accuracy of multiple slice CTA – incorrect answer? • Variable sensitivities from 53% to 87% in different studies • Reader’s experience is important • Specificity > 90% • Sensitivity is higher than specificity

  7. Question 4 Diagnostic accuracy of CTA – incorrect answer? • Dependent on clinical probability for PE • CTA has high NPV similar to that at V/Q scan • Independent from clinical probability for PE

  8. Diagnostic Pathways in Acute Pulmonary EmbolismRecommendations of The PIOPED II Investigators

  9. Diagnostic Pathways in Acute Pulmonary Embolism

  10. Pre Imaging Objective clinical probability • Three clinical scoring system have been tested prospectively and validated in large scale clinical trials: Wells’ score (Ann Intern Med 1998) Geneva Score (Arch Intern Med 2001, Ann Intern Med 2006) Pisa Score (Ann RespirCrit Care Med 1999, Ann j Med 2003)

  11. The diagnostic yield of D-Dimer is lower in cancer patient, the elderly, inpatient, recent trauma or surgery and during pregnancy

  12. CHEST X- Ray • Initial CXR usually normal. • May progress to show atelectasis, plueral effusion and elevated hemidiaphram. • Hampton’s hump and Westermark signs are classic findings but are not usually present.

  13. Hampton’s Hump – consists of a pleura based shallow wedge-shaped consolidation in the lung periphery with the base against the pleural surface. • Westermark sign – Dilatation of pulmonary vessels proximal to embolism along with collapse of distal vessels, often with a sharp cut off.

  14. Lung V/Q scan • Should lung scan be omitted for pulmonary embolism diagnosis in the age of multislice spiral CT? A) YES B) NO NO, Lung scan has a role in PE diagnosis When there are: Contraindications to CT Scan: Allergy to iodinated contrast agent Renal failure Pregnancy? High diagnostic yield and avoidance of unnecessary radiation exposure. Pregnancy Young patient with normal X-ray.

  15. Interpretation Criteria of V/Q scan - Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED), 1990 • Revised PIOPED, 1995 • PISA-PED, 1996: Perfusion scan only • PIOPED II , 2006 • Modified PIOPED II : perfusion and CXR

  16. PIOPED • 933/1,493 patients analyzed • 755 of these patients with pulmonary angiography within 12– 24 h of V/Q scan • Posterior xenon-133 ventilation scan, followed by an 8-view Tc-99m MAA perfusion lung scan • One-year follow-up: New PE, major bleeding complications, or death 1Value of the ventilation/perfusion scan in acute pulmonary embolism. Results of the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED). The PIOPED Investigators. JAMA 1990; 263:2753-9 

  17. PIOPED: Probability of PE

  18. V/Q scan accuracy: PIOPED • Based on PA: 98% sensitivity and 10% specificity for V/Q scan • High-probability V/Q scans (V/Q mismatch) as criteria for PE: Failed to detect PE in 59% of patients, based on PA.

  19. Likelihood of PE: PIOPED Predictive values > 90%: Only 22% of patients. Combined V/Q scan and clinical probability: Highest diagnostic accuracy. High clinical probability & high-probability V/Q scan: 95% likelihood of PE. Low clinical probability & low-probability V/Q scan: 4% likelihood of PE.

  20. PISA-PED, 1996: Perfusion scan only • 890 patients with Q scan, compared with PA • 413/670 (62%) patients with abnormal Q scans had PA; no PA if normal/near normal Q scan • 92% sensitivity and 87% specificity • Positive Q scan and high clinical suspicion: PPV >90% • Negative Q scan and low clinical suspicion: NPV of 97%.

  21. Pisa Ped perfusion scan categories and interpretation criteria Miniati M, et al: Value of perfusion lung scan in the diagnosis of pulmonary embolism: Results of the Prospective Investigative Study of Acute Pulmonary Embolism Diagnosis (PISA-PED). Am J Respir Crit Care Med 1996;154:1387–1393.

  22. PISA-PED: Conclusion • Q scanning alone: Much closer to angiography than V/Q scanning • Q scanning rather than V/Q scanning: Imaging technique of first choice for diagnosis of PE

  23. PIOPED II: V/Q scan results • PE present or PE absent: 74% (PISA-PED: 75%) • Sensitivity for PE present: 77% (CTA: 83%) • Specificity of PE absent: 98% (CTA: 98%) Conclusions: V/Q scan provides definitive diagnosis in a majority of patients (74%) Sostman HD, et al. Acute pulmonary embolism: sensitivity and specificity of ventilation perfusion scintigraphy in PIOPED II study. Radiology 2008; 246: 941-946

  24. Stripe Sign: A thin line (stripe) of activity between a Q defect and adjacent pleural surface: sometime in emphysema. Only 6% prevalence of PE.Triple match: Matching Q and V defect, and CXR abnormality, regardless of size: Atelectasis, consolidation. Prevalence of PE: 26% (upper - 11%; middle - 12%; lower - 33%)1

  25. Focal Hot Spots on Perfusion Scan

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