Comments: Plain chest x-rays show diffuse small nodular and reticular densities in both lungs that are more marked laterally and especially in the lung bases.  HRCT shows ring shadows and increased lucency laterally in both lungs from the upper lung regions down to the lung bases where these changes are most prominent.  Perfusion lung scintigraphy shows an inhomogeneous perfusion distribution in the lateral aspects of both lungs, and perfusion is absent in the posterior lung bases laterally.   The single breath and equilibrium images of the ¹³³ Xe gas inhalation study reveal rather homogenous distribution of gas and there is no indication of wash-out delay in any lung region, indicating no evidence of on obstructive ventilatory disturbance.

Technegas planar imaging shows a mildly inhomogeneous distribution in the lateral portions of each lung and inhomogeneity is most prominent in the lung bases.

Clinical point: Evaluation of regional ventilatory disturbances in three dimensions and comparison of morphological abnormalities revealed by HRCT with ventilatory disturbances.

General Comments: Technegas SPECT images show areas of defect in ventilation in addition to a slightly inhomogeneous distribution consistent with the morphological changes revealed by CT.   These abnormalities are located in the lateral lung fields subpleurally.   These ventilatory abnormalities presented in three dimensions are not appreciated by ¹³³Xe gas inhalation studies.