Comparison of HRCT and SPECT in the estimation of emphysema heterogeneity for endoscopic lung volume reduction

Introduction: Lung volume reduction (LVR) is a therapeutic option for patients with advanced heterogeneous lung emphysema in COPD. We compared the extent of emphysema as assessed by two current standard methods: high-resolution computed tomography (HRCT) analysed by StratX® software and single photon emission computed tomography (SPECT).   Method: Patients evaluated for LVR were considered for inclusion. The primary endpoint was the qualitative and quantitative discordance on the extent of tissue destruction per lobe as assessed by perfusion (SPECT) and voxel density (StratX®). Secondary outcomes were the evaluation of fissure completeness by StratX® and an improvement in lung function test (LFT) after LVR. Results: We included 164 patients in this study. Qualitative discordance occurred in 29.3% patients, mainly in the RUL and was more severely rated by SPECT. Quantitative discordance was highest in the RUL (20.16±35.49%). The highest fissure completeness was measured between the LUL and LLL (91.61±12.46%). After LVR, there was a significant improvement in RV, TLC and FEV1 (all p<0.001) and in 50% of patients there was a significant improvement in at least one LFT parameter. However, seven patients showed no improvement in any LFT parameter.   Conclusion: In this study we demonstrated that there is a discordance regarding the estimation of emphysema extent in at least one lobe in one third of patients evaluated for LVR with SPECT and HRCT/StratX®. Our results warrant direct comparison of SPECT and StratX® in terms of preoperative evaluation in a randomized controlled trial.