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2017: V/Q in PE What’s up?

2017: V/Q in PE What’s up?. Darlene Metter, MD, FACR. Disclosure. None. Thank you. Mark Tulchinsky, MD* Leonard M Freeman, MD*. * Co-authors for “ Current Status of Ventilation-Perfusion Scintigraphy in Suspected Pulmonary Embolism ” Mar 2017 AJR. Learning Objectives.

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2017: V/Q in PE What’s up?

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  1. 2017: V/Q in PE What’s up? Darlene Metter, MD, FACR

  2. Disclosure • None

  3. Thank you • Mark Tulchinsky, MD* • Leonard M Freeman, MD* * Co-authors for “Current Status of Ventilation-Perfusion Scintigraphy in Suspected Pulmonary Embolism” Mar 2017 AJR

  4. Learning Objectives • Describe current V/Q imaging techniques • Explain probabilistic vs definitive reporting • Compare the rationale for planar vs SPECT vs SPECT-CT

  5. Format 1. VQ scans: then and now 2. VQ interpretation in the US 3. The small clot controversy

  6. Venous Thromboembolism • PE or DVT = venous thrombosis • PE: Life threatening DVT PE

  7. PE • PE: > 90% have DVT • DVT: 30-50% will have PE • unRx: up to 30% die

  8. PE • US annual estimates: - 900,000 DVT or PE - 60,000-100,000 deaths • Symptoms: nonspecific; need high clinical suspicion • Diagnosis: usually imaging (VQ, CT)

  9. VQ Scans: Then and Now

  10. The Scan • Ventilation: - gas (133Xe) - liquid droplets (99mTc agents) - particles (non-US: Technegas) • Perfusion: 99mTc MAA

  11. Ventilation • Gas: 133Xe: dynamic imaging, 1 view; need co-operative pt; most sensitive for airway disease • Liquid droplets: 99mTc DTPA, PYP, MDP, SC: concordant V to Q views; central airway deposition; swallowed RP; most often used in US

  12. Ventilation • Gas: 133Xe: dynamic imaging, 1 view; need co-operative pt; most sensitive for airway disease • Liquid droplets: 99mTc DTPA, PYP, MDP, SC: concordant V to Q views; central airway deposition; swallowed RP; most often used in US

  13. Ventilation • Particles: Technegas (non-US); subµ carbon particles, ideal SPECT agent A B Which is Technegas?

  14. Perfusion Sensitive test Maps blood flow at the time of injection Defects are nonspecific R L Anterior Posterior LPO RPO

  15. PE Diagnosis • Ventilation perfusion mismatch • Normal CXR and ventilation with a segmental perfusion defect

  16. 1968: LUL and RLL PE (I-131 MAA) Courtesy LM Freeman

  17. 1968: LUL and RLL PE (I-131 MAA) Courtesy LM Freeman

  18. Perfusion Imaging • Planar: 6-8 static views; - PRO: easy to see entire lung; easy to see extra-pulmonary activity; miss small clot - CON: assessing seg/non-seg defect due to summation effect

  19. Perfusion Imaging • SPECT: - PRO: Increase contrast resolution, increase sensitivity, no additional pt radiation - CON: added imaging time; seg vs non-seg defects; over diagnosis Image courtesy of Dr Niraj Patel.

  20. Perfusion Imaging • SPECT-CT: - PRO: anatomic CT correlate, increase sensitivity & specificity - CON: added pt dose from CT; over diagnosis of small PE Image courtesy of Dr Niraj Patel.

  21. Imaging • SPECT-CT: - QUESTION: Are all segmental defects w/o anatomic CT correlate PEs? Significance? - Differential Dx: vasculitis, spasm, “normal clot?” But are there other DDX? Image courtesy of Dr Niraj Patel.

  22. Segmental Q defects • PE • Hypoplastic/dysplastic pulmonary artery • Vasculitis • XRT • Mediastinitis • Granulomatous disease • Tumor

  23. Segmental Q defects* • Spontaneous vasospasm – extremely rare • Plexogenic arteriopathy (severe PAH) • Iatrogenic non-thrombosis: vertebroplasty, glue from AVM, silicone emboli • Pulmonary parasites (Schistosomiasis, Echinococcus) * UT Chest radiologist: Dr CS Restrepo .

  24. SPECT-CT • Gutte (Denmark) - 81 consec pt ; clinical, +D-dimer or Wells >2 - VQ SPECT/CT and CTPA; 6 month FU - 38% PE consensus dx: clinical, CTA, V/Q SPECT (incorporation bias) Sens Specif - VQ SPECT 97% 88% - VQ SPECT/CT 97% 100% - Q SPECT/CT 93% 51% - CTA 68% 100% * Gutte et al. J Nucl Med 2009;50:1987-1992.

  25. SPECT-CT • Gutte (Denmark) - 81 consec pt ; clinical, +D-dimer or Wells >2 - VQ SPECT/CT and CTPA; 6 month FU - 38% PE consensus dx: clinical, CTA, V/Q SPECT (incorporation bias) Sens Specif - VQ SPECT 97% 88% - VQ SPECT/CT 97% 100% - Q SPECT/CT 93% 51% - CTA 68% 100% * Gutte et al. J Nucl Med 2009;50:1987-1992.

  26. Format 1. VQ scans: then and now 2. VQ interpretation in the US 3. The small clot controversy

  27. Basic Principle • Importance of diagnosing PE • Pt has survived the insult (PE) • Treat to prevent the potentially fatal PE • PE recurrence • Untreated: 25% • Treated: 7%

  28. Interpretation Schemes • US: PIOPED I & II, mod PIOPED I (probabilities) • Europe/Canada/Australia: modified PIOPED II with Q scan/CXR & PISAPED (outcomes) • survey 15/18 acad sites*; 1 hybrid * 2015: PE present, PE absent & few non-dx; 2/18 sites

  29. PIOPED I* (1990) Multi-site prospective (> 900) S/S of V/Q scan V/Q & pulm angio c/w clinical outcomes Dev categ & criteria for prob of acute PE, later modified (1993)** Prevalence: 33% (68% inpt) * Prospective Investigation of Pulmonary Embolism Diagnosis * * One segmental MM (low → intermediate)

  30. PIOPED I: Major Problems 1) Only 28% definitive diagnosis • 72% inconclusive, 44% intermediate 2) Low probability had unacceptable high frequency of PE* 3) High probability had a low sensitivity (41%) * Up to 20% probability of PE

  31. PIOPED II (2002) Multi-site prospective (> 800) Assess efficacy of CTA-CTV in acute PE & evaluate the “very low probability” V/Q scan (PPV<10%) V/Q, CTA, CTV, USN, DSA Prevalence: 23% (11% inpt)

  32. CTA vs V/Q • 1990’s to 2000’s dec VQ scans • High # of “non-diagnostic” VQ • ↑ use of CTA in PE • ↓ use of V/Q • 2012: CTA procedure of choice in PE; reported PE +/PE -;6% tech • Propose VQ as “outcomes” (like CT)

  33. The V/Q Response: Modified PIOPED II * Sostman HD et al Radiol Mar 2008:246(3): 941-946 • 2008 Sostman* • Retrosp analysis of PIOPED II pt using V/Q • 74% classified as PE+/PE- • PIOPED I: 28% conclusive/72% inconclusive

  34. The V/Q Response: Modified PIOPED II * Sostman HD et al Radiol Mar 2008:246(3): 941-946 • 2008 Sostman* • Retrosp analysis of PIOPED II pt using V/Q • 74% classified as PE+/PE- • PIOPED I: 28% conclusive/72% inconclusive

  35. Modified PIOPED II • 2 versions: • V/Q & CXR • Q scan & CXR* • Reporting: • V/Q: High, nondx, very low, normal • Q: PE present, PE absent, nondx *1994 Stein (Gottschalk): perfusion only

  36. Modified PIOPED II • 2 versions: • V/Q & CXR • Q scan & CXR* • Reporting: • V/Q: High, nondx, very low, normal • Q: PE present, PE absent, nondx *1994 Stein (Gottschalk): perfusion only

  37. Modified PIOPED II • 2 versions: • V/Q & CXR • Q scan & CXR* • Reporting: • V/Q: High, nondx, very low, normal • Q: PE present, PE absent, nondx *1994 Stein (Gottschalk): perfusion only

  38. V/Q High: 2 or > V/Q MM V Low: nonseg, Q<CXR, triple </= seg M mid/upper, 1-3 sm, 2 or >/= M w/o CXR, stripe sign, lg effusion Normal: no defects NonDx: All others (low, intermediate) Q scan PE(+): 2 or >/= Q/CXR MM PE(-): nonseg, Q<CXR, 1 match mid/upper, 1-3 small, “stripe sign”, one large effusion NonDx: All other findings Modified PIOPED II

  39. PISA-PED* (1995) Clinical prob + CXR + Q scan 176 pt; prevalence 35%; 1° inpt PE present, PE absent, non-Dx - 37 PE; 69/176 abn (21% PE) - S/S: 89%/92%; PPV 95%;NPV 81%; accuracy 90% * Prospective Investigative Study of Acute Pulmonary Embolism Diagnosis

  40. PISA-PED • PE present: >/= 1 wedged shaped Q defect (SHAPE is important) • PE absent: non-wedged shaped Q defect, near normal or normal Q • Non-diagnostic: Cannot classify as PE+ or PE- * 2011 SNM Practice Guideline For Lung Scintigraphy

  41. PISA-PED Critique • ¼ abn but PE(-): no angio or F/U • ½ abn: no angio (contraindications) • PE(+): not all had angio • No angios on normal/near normal • Same reviewer for clinical assessment & scan interpretation (clinical bias)

  42. Question Raised • PISA-PED and Mod PIOPED II (Q only): Is a ventilation study needed? • Re-looked at Q only studies using PIOPED II database (prevalence 19%)

  43. 2008 Comparative Trial: Q* Q + CXR: Mod PD II vs PISA-PED Nondx: mod PD II 21%; PISA-PED 0 If exclude nondx, S/S mod PD II: 85%/93% PISA-PED: 80%/97% PISA-PED = Mod PD II (Q only) but less non-Dx studies * Sostman HD et al J Nucl Med 2008 Vol 49, No 11. p1741-1748

  44. Imaging Acute PE* *Mettler FA , Guiberteau MJ Essentials of Nuclear Medicine Imaging 6th ed. 2012: p 212.

  45. Imaging Acute PE* *Mettler FA , Guiberteau MJ Essentials of Nuclear Medicine Imaging 6th ed. 2012: p 212.

  46. 2 Major Benefits for Q Only • Lower radiation dose* • Whole body CT ED > 5 times V/Q • 4-16/64: 5.4 mSv/19.9 mSv • VQSPECT/CT: 2.8 mSv • Female breast**: ● CT: 10-70 mSv: V/Q: 1.5 mSv ● CT 60% females; 27% < 40 yrs 2. Lower cost * Stein PD. Pulmonary Embolism 3rd ed. 2016 p 416 ** Metter DF et al. AJR 2017;208:489-494.

  47. 2 Major Benefits for Q Only • Lower radiation dose* • Whole body CT ED > 5 times V/Q • 4-16/64: 5.4 mSv/19.9 mSv • VQSPECT/CT: 2.8 mSv • Female breast**: ● CT: 10-70 mSv: V/Q: 1.5 mSv ● CT 60% females; 27% < 40 yrs 2. Lower cost 15% ED of CTA * Stein PD. Pulmonary Embolism 3rd ed. 2016 p 416 ** Metter DF et al. AJR 2017;208:489-494.

  48. Change 2 Categories • The low probability scan 2. The single moderate or large segmental mismatch defect

  49. Low Probability • Sostman (2008)*: • PIOPED II database: 6.7% incidence of PE • Stein (2016)**: Reviewed 4 outcome studies in low probability scans w/o Rx • Incidence of nonfatal PE: 0.13% • Incidence of fatal PE: 0% • Low probability = “No evidence of PE” * Radiology 2008. 245:941-946. ** Stein PD Pulmonary Embolism, 3rd ed. Chickester, W Sussex, Hoboken, NJ. Wiley Blackwell. 206:408-409.

  50. Single MM Vascular Defect • Stein* • Vascular defect: • PPV of one moderate or large perfusion defect is similar • “Vascular defect” equates a moderate to a large perfusion • Simplifies V/Q interpretation for PE * Chest 1993. 104:1468-1471.

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