Computed tomography with volume rendering for the evaluation of parenchymal hyperinflation after bronchoscopic lung volume reduction

Abstract

Objective: To assess computed tomography with volume rendering (CT-VR) as a tool to evaluate parenchymal hyperinflation before and after bronchoscopic lung volume reduction (BLVR) in patients with advanced stage emphysema.

Materials and methods: Between March 2006 and October 2007, we have prospectively studied pre- and postoperatively by spiral multislice CT scan and functional tests seven patients (six male, one female; age range 51-77 years, mean 64) with advanced stage heterogeneous emphysema who underwent BLVR using the Emphasys one-way valves (Emphasys, Redwood City, CA, USA). CT parameters considered were: the volume of the 'target' lobe and of the entire treated lung, the diameters (antero-posterior and cranio-caudal) of the treated hemithorax and the emphysematous parenchyma rate with respect to the normal parenchyma rate of the treated lobe. Lung parenchyma has been classified as emphysematous if the density was in the -1024/-900 Hounsfield units (HU) range and as normal if the density was in the -900/-200 HU range. Preoperative radiological data were compared with postoperative data and plotted against spirometric data observed 1 month after treatment.

Results: Overall, 24 valves have been implanted in the 7 patients. Valves have been placed in the right upper lobe in two patients, in the left upper lobe in four and in both the left upper lobe and the right lower lobe in one. Volume reduction as a proportion of the 'target' lobe and of the entire lung has been observed in all patients with significant differences between mean preoperative and postoperative values [p=0.016 (target lobe); p=0.031 (lung)]. Lobar volume reduction ranged between 1.3% and 53.7% of preoperative values. Volume reduction of the entire lung ranged between 3.1% and 16.8%. Thoracic diameters decreased in all patients after treatment with significant mean differences [p=0.007 (antero-posterior); p=0.004 (cranio-caudal)]. FEV1 increased in six of seven patients with significant mean differences (p=0.025). The higher volume reduction rate has been observed in the three patients showing the better FEV1 improvement. Emphysematous lung parenchyma rate decreased postoperatively in six of seven patients with mean differences being not significant (p=0.17).

Conclusions: CT-VR is an excellent tool to confirm the efficacy of BLVR in reducing parenchymal hyperinflation. Functional advantages are proportional to the volume reduction as measured by CT-VR.