Is hybrid lung SPECT/CT necessary for pre-interventional quantification of relative lobar lung function?

Aim: In pulmonary malignancies (PM) calculation of relative lung function from perfusion scintigraphy is an established tool to predict post-surgical lung function. Published data has proven the superiority of 3D vs. planar imaging. Data from hybrid SPECT/CT-scanners allow for registration of the low dose CT (ldCT) to the diagnostic CT (dCT). A dCT is used as the best basis for anatomical lobe delineation. Due to limited availability of SPECT/CT-cameras, the aim of the study was to test whether - using of a dedicated software algorithm and a dCT - the quantification of perfusion data from SPECT-scanners is as exact as from SPECT/CT-scanners. Methods: 61 patients with PM were routinely examined before surgery using hybrid V-/P-SPECT/CT with Technegas and 99mTc-MAA. Quantification was done using “HERMES Hybrid 3D-Lung Lobe Quantification”. In setting A (hybrid) SPECT and a combination of low-dose CT and diagnostic CT was used for quantification. In setting B (non-hybrid) only the dCTs were used. Correlation analyses of the resulting relative lobar perfusion between both approaches were performed, additionally processing time was compared. Results: 305 lobes were quantified with both approaches. Evaluation time was 6:37 min (hybrid) versus 6:34 min (non-hybrid). Lobar values ranged from 0-55% for hybrid and from 0-58% in the non-hybrid approach, no significant differences were found (p>0.9). Correlation was excellent for both approaches with R=0.984 and a slope of the regression line of 1.001 (p