NORMAL V/O SCAN A)Xenon-133 ventilation study B)Tc-99m MAA images C)The chest radiograph was also normal. C
Pleural effusion and Pacemaker effect. A-P chest radiograph reveals uniformly greater density inthe right lung compared to the left caused by an effusion layering out posteriorly when the patient is supine. Corresponding Tc-99m MAA perfusion study shows decreased perfusion to the right lung on the posterior view (upper left hand image), which is not seen on the other views,tipping The pacemaker causes a well-defined defect (arrow).
Swallowed Tc-99m DTPA. Intense uptake in the trachea and stomach may result from swallowed radiopharmaceutical.
Effects of airway obstruction: Ventilation abnormalities may be due to obstructions in larger airways. This might present as a large defect (left ) caused by bronchogenic carcinoma or mucous plugs. Constriction of smaller bronchi in asthma can also cause ventilation abnormalities (right).
Effect of pulmonary artery branching pattern on the appearance of emboli. Emboli may be due to larger more proximal clots (left) or showers of smaller clots lodging more distally (right). In either case, the resulting defects should be pleural- based wedged shape and corresponding to the segments of the lung.
What are the two most commonly used radiopharmaceuticals for ventilation imaging? What are their advantages and disadvantages? What is the minimum number of particles recommended for pulmonary perfusion imaging? How should the dose of technetium-99m MAA be adjusted in pediatric patients? What is the size range of MAA particles? What is the biological fate of MAA particles? What is the preferred patient position during administration of Tc-99m MAA?