An improved method for the analysis of xenon-133 washin and washout curves

A method is described for analysis of xenon-133 washin and washout curves, in the presence of a slowly varying background. The method uses least-squares fitting of a single exponential together with a quadratic function to correct for the background. The method has been applied both to simulated data and to data from 25 patients. The accuracy in the relevant lung parameters was 5% over a wide range of the specific ventilation. A comparison is made with other methods in use to measure regional lung-function parameters. Our method produces reliable results even when specific ventilation is low, which can occur in patients with chronic airflow obstruction, where other methods may incur errors of more than 45%.