PET scanning of macrophages in patients with scleroderma fibrosing alveolitis

RationaleAssessment of disease activity in fibrosing alveolitis due to systemic sclerosis (FASSc) is difficult without using invasive investigation. A repeatable noninvasive method of assessing disease at a cellular level such as with positron emission tomography (PET) could be of great value in evaluating high-resolution changes in the pathological process.ObjectivesTo investigate whether the level of inflammatory cell traffic and lung density in FASSc, imaged in vivo by PET, is different to controls and whether they are associated with changes in pulmonary function indices.MethodsWe used PET to measure lung density and tissue uptake of ¹¹C-R]-PK11195, a ligand that binds to receptors found in abundance in macrophages. Fifteen patients with FASSc were compared to seven controls.ResultsA trend of reduced uptake of ¹¹C-R]-PK11195 was observed in FASSc patients (P=.09) and correlated inversely with lung density (r=?.62; P<.05), which was significantly elevated in FASSc 0.35±0.02 vs. 0.23±0.02 g/cc (mean±S.E.M.); P<.005].ConclusionThese results demonstrate that inflammatory cell traffic and lung density can be imaged in vivo in FASSc using PET, and that this approach might be of potential value in understanding, in situ, components of pathogenesis that may have value for prognosis.