The aim of this study was to evaluate impaired lung uptake of (123)I-metaiodobenzylguanidine ((123)I-MIBG) on SPECT, compared with perfusion SPECT and morphologic CT, in patients with pulmonary emphysema (PE).
Methods: (123)I-MIBG SPECT was performed at 15 min and 4 h after intravenous injection of (123)I-MIBG in 36 PE patients with a history of smoking and variable-extent low-attenuation areas on CT, indicative of emphysematous changes, and in 16 controls with no history of smoking and no noticeable low-attenuation areas. The distribution of (123)I-MIBG was compared with that of low-attenuation areas on CT and perfusion on SPECT at the base of the 180 lung lobes of the PE patients. Total-lung (123)I-MIBG kinetics were calculated, including early and delayed lung-to-mediastinum uptake ratios and washout rate.
Results: The controls showed a fairly uniform lung (123)I-MIBG distribution nearly consistent with perfusion. PE patients had heterogeneous (123)I-MIBG defects showing frequent discordance with low-attenuation areas or perfusion distribution; (123)I-MIBG defects were more extensive than low-attenuation areas in 76 lobes (42.2%) of 31 patients (86%) and more extensive than perfusion defects in 44 lobes (24.4%) of 22 patients (61%). (123)I-MIBG defects were seen regardless of the absence of noticeable low-attenuation areas and perfusion defects in 19 lobes (10.5%) of 16 patients (44%). All total-lung (123)I-MIBG kinetic parameters in PE patients were significantly lower than the control values (P < 0.0001), with significant correlation with alveolar-arterial oxygen tension gradient but without correlation with the extent of perfusion defects or low-attenuation areas.
Conclusion: (123)I-MIBG SPECT allows evaluation of lung pathophysiology in PE independently of perfusion SPECT or morphologic CT, and impairment of lung (123)I-MIBG uptake may be more extensive than perfusion or morphologic abnormalities in PE.