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IMAGE INTERPRETATION · LUNG V/Q IMAGING

Reducing MAA Particles in Pulmonary Hypertension

V/Q lung scan showing ventilation-perfusion mismatch
V/Q lung scan showing ventilation-perfusion mismatch

CC BY-SA 4.0 · Hellerhoff / Wikimedia Commons · source file

Question

When performing a V/Q scan to evaluate for PE, which of the following patient conditions MOST requires a reduced Tc-99m MAA particle count?

  1. AWarfarin anticoagulation
  2. BMetformin use
  3. CPulmonary arterial hypertension (PAH)
  4. DThyroid hormone replacement
Show the answer and explanation

C. Pulmonary arterial hypertension (PAH)

Patients with severe pulmonary arterial hypertension (PAH) have a reduced functional pulmonary vascular bed. Injecting the standard 200,000–700,000 MAA particles could temporarily occlude too large a percentage of already-compromised pulmonary capillaries. Therefore, the particle count is REDUCED (typically to ~100,000 particles) in patients with PAH, right-to-left shunts, or single-lung transplant recipients. Anticoagulation, metformin, and thyroid hormones are not relevant to MAA particle count.

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