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eFigure 9–20. Normal lung ventilation with xenon-133. With the patient’s single full breath, inhaled radioxenon is evenly distributed to all lung areas, reaching the terminal airways and alveoli in the normal patient (A, posterior view). There is a less noticeable gradient of activity from the upper to the lower lung fields than is seen in perfusion lung images. Fifteen-second images obtained during closed-system rebreathing of a xenon–oxygen mixture show uniform distribution at 120 seconds (B). Serial 15-second frames after switching the patient to room air breathing (C to G) show a homogeneous pattern of washout from all lung areas. This sequence mainly evaluates the posterior lung regions. To better localize gas trapping in specific lung segments or more anterior regions, the acquisition may be modified after the rebreathing phase by rotating the patient into posterior oblique positions. Selected images from a complete study include single breath (H, posterior view), the late phase of rebreathing (I, posterior view), posterior washout (J), left posterior oblique washout (K), and right posterior oblique washout (L). No gas is retained in this patient, which is normal, but in obstructive airway disease gas retention persists and is better localized in the oblique views than in a posterior view alone. A small amount of alveolar xenon normally crosses the alveolar membrane to reach the blood and be distributed throughout the body. Because it is highly soluble in lipids, xenon accumulates in adipose tissue, including the liver, which is faintly seen with prolonged rebreathing. Liver activity should not be mistaken for delayed washout of xenon from the base of the lung. Occasionally, splenic blood pool radioactivity or swallowed xenon in the stomach may also be seen. (SIN BRE = single breath, L REB = late rebreathe, WO = washout.) (Reproduced with permission from Grippi MA, Elias JA, Fishman JA, Kotloff RM, Pack AI, Senior RM, Siegel MD. Fishman’s Pulmonary Diseases and Disorders, 5e. 2015.) Four examples of normal ventilation scans compared with eight examples of abnormal scans.

Current Medical Diagnosis & Treatment 2024 > Pulmonary Venous Thromboembolism

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