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IMAGE INTERPRETATION · LUNG V/Q IMAGING

How Tc-99m MAA Lung Perfusion Imaging Works

Lung perfusion scintigraphy — multiple views
Lung perfusion scintigraphy — multiple views

Public domain · Wikimedia Commons · source file

Question

Tc-99m MAA (macroaggregated albumin) is used for lung perfusion scanning. What is the mechanism by which MAA produces a perfusion scan?

  1. AMAA is absorbed by alveolar epithelium and distributed by lymphatics
  2. BMAA binds to surfactant in the alveoli
  3. CMAA temporarily occludes 0.1–0.5% of pulmonary capillaries proportional to blood flow
  4. DMAA crosses into the alveoli and is exhaled, producing a ventilation image
Show the answer and explanation

C. MAA temporarily occludes 0.1–0.5% of pulmonary capillaries proportional to blood flow

Tc-99m MAA particles (10–100 μm) are injected IV and travel to the pulmonary vasculature, where they temporarily lodge in pulmonary capillaries proportional to regional blood flow. Only 0.1–0.5% of capillaries are occluded, causing no hemodynamic effects in normal patients. Areas of reduced blood flow (PE, pulmonary hypertension) receive less MAA, appearing as photon-deficient ('cold') regions. The particles dissolve within 6–8 hours and are cleared by the reticuloendothelial system.

More lung v/q imaging images

V/Q lung scan showing ventilation-perfusion mismatchReducing MAA Particles in Pulmonary Hypertension Lung perfusion scintigraphy — multiple projectionsStripe Sign on a Lung Perfusion Scan V/Q lung scan — matched ventilation and perfusion defectsV/Q Scan in COPD: Matched Defects Lung perfusion scintigraphy — normal study in a young female patientV/Q Scan vs CTPA for Pulmonary Embolism in Pregnancy Lung scintigraphy — ventilation and perfusion imagesVentilation Agents: Tc-99m DTPA Aerosol vs Xe-133 V/Q lung scan — ventilation and perfusion projectionsIntermediate-Probability V/Q Scan
← Normal Lung Perfusion Scan and Pulmonary EmbolismReducing MAA Particles in Pulmonary Hypertension →

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