Ventilation perfusion ratios of the normal supine lung using emission tomography.

Ventilation perfusion imaging using single photon emission tomography was carried out in the supine position on four subjects, three normal volunteers and one patient, all free from evidence of respiratory disease. Ventilation imaging was by means of the steady-state inhalation of krypton 81m, perfusion imaging utilised technetium 99m labelled macroaggregates. In the three normal volunteers, perfusion studies were repeated using steady state infusion of 81Krm in solution. Ventilation perfusion ratios were calculated for the anterior, middle and posterior regions of the lung using axial slices from apex to base. The results using 99Tcm for perfusion showed a gradient of ventilation perfusion ratios from front to back of 1.27 anteriorly and 0.93 posteriorly for the right lung, 1.06 anteriorly and 0.77 posteriorly for the left lung. Using 81Krm for perfusion a small gradient of 0.94 to 0.82 was observed.