Tomographic display of ventilation-perfusion ratio

Tomographic displays of the distribution of ventilation-perfusion ratio in six subjects with a single photon radionuclide computed tomography (RCT) were obtained. The distribution of ventilation (V) and perfusion (Q) were measured separately with continuous breathing of Kr-81m and with intravenous administration of Tc-99m labelled macroaggregates of human serum albumin (MAA). V/Q was calculated pixel-by-pixel and the distributions of V/Q were displayed in a logarithmic scale with the surrounding thoracic cage obtained from transmission CT. The number of voxel, ventilation and perfusion were plotted against log(V/Q). They had almost log normal distributions with smaller variances in healthy subjects than those with emphysema or bronchitis. In the former, much coincidence between V and Q was observed, whereas in the latter, dissociation was seen between them. This noninvasive technique provided not only the visualization of the distribution of V/Q in a transaxial images, but also the quantifications of the V-Q mismatch