V/Q SPECT-Normal Values for Lobar Function and Comparison With CT Volumes

Ventilation and perfusion lung imaging with SPECT/CT permits accurate delineation of the individual lobes of the lungs using the CT images for use in ascribing the relative functional contribution to overall lung function of the lobes of both ventilation and perfusion. Moreover, an advantage of using Technegas as the ventilation agent and radiolabelled macro-aggregated albumin microspheres as the perfusion agent is that the deposition pattern is fixed upon administration and thus different patient postures can be studied and the effect of gravity and position determined, even though the scans must be acquired with the subject supine using conventional gamma camera SPECT/CT systems. In this paper we report on normal ranges for functional contribution of the individual lobes of the lung to overall function studied in the supine and erect positions in a small cohort of normal subjects. Differences are seen between the anatomical volumes as determined by segmentation of the CT scans and the ventilation and perfusion contributions in the different positions. As pulmonary function testing in the respiratory laboratory is usually performed in the upright position we perform all of our clinical imaging lung function studies in this position (for radiotracer administration) also. The methodology for measuring lobar function is minimally invasive, readily available, and would be hard to imagine being acquired as readily with any other technique.