• Identifying active vascular microcalcification by 18F-sodium fluoride positron emission tomography

      Irkle, A.; Vesey, A.T.; Lewis, D.Y.; Skepper, J.N.; Bird, Joseph; Dweck, M.R.; Joshi, F.R.; Gallagher, F.A.; Warburton, E.A.; Bennett, M.R.; et al. (2015)
      Vascular calcification is a complex biological process that is a hallmark of atherosclerosis. While macrocalcification confers plaque stability, microcalcification is a key feature of highrisk atheroma and is associated with increased morbidity and mortality. Positron emission tomography and X-ray computed tomography (PET/CT) imaging of atherosclerosis using 18F-sodium fluoride (18F-NaF) has the potential to identify pathologically high-risk nascent microcalcification. However, the precise molecular mechanism of 18F-NaF vascular uptake is still unknown. Here we use electron microscopy, autoradiography, histology and preclinical and clinical PET/CT to analyse 18F-NaF binding. We show that 18F-NaF adsorbs to calcified deposits within plaque with high affinity and is selective and specific. 18F-NaF PET/CT imaging can distinguish between areas of macro- and microcalcification. This is the only currently available clinical imaging platform that can non-invasively detect microcalcification in active unstable atherosclerosis. The use of 18F-NaF may foster new approaches to developing treatments for vascular calcification.
    • Identifying active vascular micro‐calcification by 18F‐sodium fluoride positron emission tomography

      Vesey, A.T.; Irkle, A.; Skepper, J.N.; Bird, Joseph; Dweck, M.R.; Joshi, F.J.; Gallagher, F.A.; Warburton, E.A.; Bennett, M.R.; Brindle, K.M.; et al. (2015-07)
      Background: Vascular calcification is an active cell-mediated process that is a hallmark of atherosclerosis. Whilst macro-calcification confers stability to plaque, micro-calcification is a key feature of high-risk atheroma associated with major adverse cardiovascular events. Positron emission tomography combined with computed tomography (PET/CT) imaging of atherosclerosis using 18F-sodium fluoride (18F-NaF) has the potential to identify active micro-calcification and thus high-risk plaque. The precise molecular mechanism of 18F-NaF binding has however not been validated. The aim of this study was to provide a comprehensive model describing the binding characteristics, pharmacodynamics and pharmacokinetics of 18F-NaF. Methods: Patients undergoing carotid endarterectomy were studied. 18F-NaF binding was analysed using a combination of electron microscopy, autoradiography, gamma scintigraphy, histology and immunohistochemistry, pre-clinical microPET/microCT and dynamic clinical PET/CT. Results: 18F-NaF was shown to bind to calcium within plaque with high affinity. Binding was selective and specific. 18F-NaF PET was able to identify on-going nascent micro-calcification far beyond the resolution of clinical and pre-clinical CT systems. Furthermore, 18F-NaF was able to distinguish between areas of macro and micro-calcification. Conclusions: 18F-NaF PET/CT is the only currently available clinical imaging platform that can detect micro-calcification in active unstable atherosclerosis. The use of 18F-NaF will foster new approaches to developing treatments targeting unstable plaque and vascular calcification.