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ventilation-perfusion (VQ) scan

Assessment of ventilation-perfusion (VQ) mismatch. Indications: - chronic thromboembolic pulmonary hypertension (CTEPH) - method of choice - assessment of pulmonary embolism - pulmonary angiography is generally method of choice Clinical significance: - initial diagnostic modality in the evaluation of chronic thromboembolic pulmonary hypertension (CTEPH) [4] - alternate diagnostic modality in the evaluation of pulmonary emboli a) initial diagnostic test in pregnant women b) preferred method in patients with risk of acute kidney injury - preexisting kidney disease (chronic renal failure) - diabetes mellitus - hypovolemia - free urinary light chains of multiple myeloma [1] c) pulmonary CT angiography is the preferred method in patients with intermediate to high-probability PE [1] - ventilation in the absence of perfusion suggests pulmonary emboli - two or more segmental defects on perfusion scan suggest large vessel chronic thromboembolic disease or pulmonary hypertension - however, defects on perfusion scan are non-specific & may be seen in COPD - pulmonary angiography is indicated to resolve equivocal findings on VQ scan. Sensitivity: 77%, specificity 98% [3] VQ scans underestimate severity of central pulmonary arterial obstruction. [2]

General

pulmonary ventilation imaging

References

  1. Medical Knowledge Self Assessment Program (MKSAP) 11, 16, 18. American College of Physicians, Philadelphia 1998, 2012, 2018
  2. Smith R., Jewish Home for the Aging, Reseda CA, 2001, unpublished
  3. Sostman HD et al, Acute pulmonary embolism: Sensitivity and specificity of ventilation-perfusion scintigraphy in PIOPED II study. Radiology 2008, 246:941 PMID: 18195380
  4. Salaun P-Y et al. Noninvasive diagnosis of pulmonary embolism. Chest 2011 Jun; 139:1294 PMID: 20724733