Reproducibility of a semi-quantitative lobar pulmonary ventilation and perfusion technique using SPET and CT

Evaluation of regional lung function is valuable prior to lung surgery in patients with chronic lung disease. Our aim was to evaluate the reproducibility of a locally developed single photon emission tomography/computed tomography (SPET/CT) programme between and within three observers in assessing lobar pulmonary volumes, perfusion and ventilation.

Twelve lung transplantation candidates had VQ SPET and diagnostic CT to determine lobar pulmonary function and plan surgery. Their data were used retrospectively in an in-house developed programme which delineates the lung fissures on the diagnostic CT as an anatomical template used to estimate the volume of each of 5 lung lobes. These anatomical volumes were then applied to the corresponding ventilation (^99m Tc technegas) and perfusion (^99m Tc MAA) SPET studies. The data were anonymised, duplicated and then processed in random order blindly by 3 readers several weeks apart. Nine studies could be adequately processed. The programme failed in delineating lung volumes in 2 subjects and there was data corruption in the third. The results were evaluated for inter- and intra- observer variability using an intra-class Correlation Coefficient (ICC). An ICC score was calculated for each lobe for volume, ventilation and perfusion.

Inter- and intra- observer ICC scores for ventilation, and perfusion scans were all very high. Similar very strong ICC concordance scores were noted for volume except intra-observer ICC scores for left upper lobe (0.76) and right mid lobe (0.66) where scores showed strong concordance by standard statistical descriptors. The method was sensitive enough to demonstrate the expected gradient of ventilation/perfusion even in these patients with substantial pathology.

Our method of lobar VQ SPET with CT quantitation has high inter- and intra- observer concordance and in this preliminary data set seems to be a reliable and reproducible test for semi-quantitation of differential volume, ventilation and perfusion of the lobes of the lungs.