Study: PET/CT quantifies joint inflammation

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Small animal PET/CT using 18F-FDG is a feasible method for monitoring and quantitative assessment of inflammation in glucose-6-phosphate isomerase (G6PI)-induced arthritis, according to research published in the November issue of Arthritis Research & Therapy.

Signalling of radioisotope 18F-FDG injected in mice with G6PI-induced arthritis was analyzed by PET/CT by Ingo M. Irmler, PhD, from the Institute of Immunology at Jena University Hospital in Jena, Germany, and colleagues in the study.

Accumulation of 18F-FDG in tissue was quantified by PET measurement, whereas high definition CT delivered anatomical information. The fusion of both images revealed in detail spatial and temporal distribution and metabolism of 18F-FDG. A distinct 18F-FDG signal could be measured by PET in carpal and tarsal joints, from mice with early or established arthritis. In contrast, no accumulation of 18F-FDG was detectable before arthritis onset, according to Irmler and colleagues.

“Our findings demonstrate the feasibility and usefulness of 18F-FDG joint uptake for objective in vivo quantification of synovial inflammation in the course of G6PI-induced arthritis,” wrote Irmler and colleagues.

Since it is possible to perform repeated non-invasive measurements in vivo, not only numbers of animals in preclinical studies can markedly be reduced by this method, but also longitudinal studies come into reach, e. g. for individual flare-up reactions or monitoring therapy response in progressive arthritis, the researchers added.

Furthermore, in vivo imaging increases statistical quality of data in treatment studies because the status of an animal before and after disease-modulating intervention can be compared directly.

Robust statistical analyses at various time points of arthritis progression showed a highly significant correlation to histopathological inflammation assessment, proposing 18F-FDG small-animal PET/CT as a feasible tool for preclinical arthritis research. In addition to monitoring efficacy of anti-inflammatory drugs, it offers the possibility of performing large-scale animal studies including repeated in vivo examinations, wrote Irmler and colleagues.

Therefore, combined PET/CT using 18F-FDG as a tracer is a new and powerful tool to quantify experimental joint inflammation non-invasively and accurately in vivo, concluded Irmler and colleagues.