What is primarily assessed with lung scans using Tc MAA?

• A. Oxygen saturation levels
• B. Blood flow to the lungs
• C. Airway resistance
• D. Ventilation efficiency

Answer: (B)

Lung scans utilizing Technetium-labeled macroaggregated albumin (Tc MAA) primarily assess blood flow to the lungs. This radiopharmaceutical is employed in perfusion imaging, which provides valuable information regarding the pulmonary circulation. When injected into the bloodstream, Tc MAA particles become trapped in the pulmonary capillaries, allowing for visualization of blood flow distribution in the lungs.

This assessment is crucial for diagnosing various conditions, such as pulmonary embolism, where blood flow is impeded. The scans highlight areas of decreased perfusion, indicating potential blockages or abnormalities in the vascular supply to lung tissue.

The other presented choices do not accurately reflect the primary function of Tc MAA lung scans. For instance, oxygen saturation levels are typically evaluated through other non-imaging methods such as pulse oximetry. Airway resistance is assessed with different techniques, like spirometry, which evaluates airflow in the lungs rather than blood flow. Ventilation efficiency relates to how well air is distributed in the lungs rather than how blood circulates through them, which is not the focus of a perfusion scan with Tc MAA. Thus, the primary goal of Tc MAA lung scans is indeed to assess blood flow within the pulmonary system.