Comparison of Quantitative Ventilation-Perfusion Lung Scan Results Using Different Xenon-133 Ventilation Images

Objective: This paper evaluates the influence of the specific Xe ventilation images used to calculate differential function in quantitative ventilation-perfusion lung scans. Methods: Whole-lung differentials were determined on 43 Xe ventilationfl mTc-macroaggregated albumin perfusion studies. Ventilation calculations were performed for the firstbreath, up to three equilibrium and the composite of all equilibrium images, and perfusion calculations were performed for the anterior and posterior images and their geometric mean. Differences of :::5% between comparable images were considered significant. Results: The first-breath ventilation differential differed from at least one equilibrium view in 13 patients {30%) and from the composite of all equilibrium images in seven patients {16%), while the posterior perfusion differential differed from the anterior differential in 15 patients {35%) and from the geometric mean differential in six patients {14%). By comparison, the posterior or geometric mean perfusion differential differed from either the first-breath or composite ventilation differential in 31 patients {72%). Nine patients {21 %) had ventilation/perfusion discrepancies =::10%, with ventilation differentials more symmetric in seven patients. Conclusion: The choice of Xe ventilation image has only a limited effect on differential calculations. Discrepancies are more frequent between ventilation and perfusion differentials, making it important to determine both, particularly in patients with asymmetric lung disease.