Abstract
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Objectives Endobronchial valve placement (EVP) is a new treatment option for patients with pulmonary emphysema (PE). Imaging of lung function is desired to evaluate the least functional lung areas. The aim of this study was to investigate associations of ventilation/perfusion (V/P) SPECT/CT and functionalCT (fCT).
Methods Nineteen patients (11 men, 7 women; median age: 68.6 years) with PE and COPD were evaluated by standardized V/P SPECT/CT (Tracer: T99m MAA and Tc99m micro aerosol Technegas) and fCT for EVP. A software based analyzing system (SBAS) was used to assess counts per lung lobe (CpLo), counts per lung (CpLu), volume per lung lobe (VpLo) and volume per lung (VpLu), Count density per lobe (CDpLo=CpLo/VpLo) and ratios of counts (RC=CpLo/CpLu) and count density (RCD=CDpLo/ CDpLu) were calculated. fCT was used to assess differences (diff)of VpLo and VpLu in inspiration- and expiration. A ratio of diffVpLo / diffVpLu (=RdiffV) was calculated. Intermethod variability and association was analyzed using Spearman`s Rho correlation coefficient with p < 0.05 considered as a significant correlation and rho <0.5 considered as poor correlation.
Results Comparing V/P SPECT/CT with fCT yielded no correlation between density parameters and fCT parameters for perfusion (CDpLo vs. diffVpLo,-0.005; RCD vs. RdiffV, 0.023) and for ventilation (CDpLo vs. diffVpLo: 0.120; RCD vs. RdiffV, -0.017). Comparing V/P SPECT/CT with fCT with respect to the absolute number of counts in V/P SPECT/CT yielded weak correlations for perfusion (CpLo vs. diffVpLo, 0.344; RC vs. RdiffV, 0.418) and for ventilation (CpLo vs. diffVpLo, 0.392; RD vs.RdiffV, 0.372).
Conclusions V/P SPECT/CT and fCT correlate weakly or not at all in patients with PE. For planning of endobronchial valve placement it should be considered that the functional information of fCT and V/P SPECT/CT is hardly comparable.