Bland Altman plot for agreement of different technologies when calculating projected percentage of lung function loss with pneumonectomy. (Top) Comparison of perfusion scintigraphy and VRI. (Middle) Comparison of ventilation scintigraphy and VRI. (Bottom) Comparison of perfusion scintigraphy and ventilation scintigraphy. Top and bottom horizontal lines represent limits of agreement; middle horizontal line is the mean difference.