Segmental Hyperperfusion in Lobar Pneumonia Visualized with Respiratory-gated Four-Dimensional Pulmonary Perfusion Positron Emission Tomography–Computed Tomography

Abstract

A 64-year-oldman underwent a respiratory-gated four-dimensional pulmonary perfusion positron emission tomography (PET)/computed tomography (CT) for preoperative regional lung function quantification. This was performed after intravenous administration of Gamacroaggregated albumin (1–3). At the time of imaging, he had a productive cough, fever, and subsequent clinical diagnosis of bronchopneumonia. Images demonstrated an area of hyperperfusion localized to an area of dense collapse/consolidative change in the lateral segment of the right middle lobe (Figure 1 and supplemental video E1). The abnormality was also clearly apparent on the nonattenuation correction images, excluding an attenuation artifact. Studies have typically documented matched ventilation–perfusion or reverse mismatch phenomenon in pneumonia (4). Although occlusive obstruction of lobar airways is usually accompanied by reflex hypoxic vasoconstriction, the local release of inflammatory mediators with vasodilatory properties with infection results in failure of this mechanism and shunting leading to hypoxia (5). The histopathologic correlate is the red hepatization phase of lobar pneumonia. Tc-macroaggregated albumin single-photon emission computed tomography/CT had also been performed in this patient, but no corresponding perfusion abnormality was found. Although this was performed 72 hours earlier, the CT abnormality was similar; we contend that in addition to the superior imaging characteristics of PET, the absence of respiratory gating and attenuation correction contributed to lack of abnormality on single-photon emission computed tomography. The higher spatial and temporal resolution of PET combined with four-dimensional acquisition (6) provides a major advance in image quality and may improve our understanding of pulmonary physiology in a spectrum of diseases. n