An extremity scanner capable of sequentially performing high resolution 3D molecular imaging by positron emission tomography (PET) and 3D anatomical imaging by X-ray computed tomography (CT) has been built by our group. This system is the first of its kind. We report our initial experience in using this system for (1) assessing metabolic activity (hence, inflammation) in Rheumatoid Arthritis (RA), Psoriatic Arthritis (PsA) and Osteoarthritis (OA) of the hand, (2) monitoring early response to anti-TNF-alpha therapy in RA, and (3) characterizing bone remodeling (osteoblastic) activity in early OA.
Eight patients (5 with RA, 2 with PsA, all starting etanercept, and 1 with early OA) were recruited. Three RA patients also had OA. The RA and PsA patients were administered the radiotracer fluorodeoxyglucose (18F-FDG) and were scanned at 80 ± 5 min post-injection. The scan lasted 13 min. All RA patients were scanned at baseline and at 1 month after initiation of etanercept therapy. Changes from baseline in regions of high metabolic activity were documented from PET/CT images. The PsA patients have only been scanned at baseline to date. The patient with early OA was administered the radiotracer sodium fluoride (18F-NaF) and was scanned at 105 min post-injection. Images for all patients were read by consensus by three radiologists.
Detailed 3D quantitative maps of molecular activity and anatomy were produced by the extremity system. Baseline scans in RA patients showed classic symptoms such as inflammation in the carpal synovium, the pisiform-triquetral compartment, at the thumb CMC joint (from OA) and at sites of erosions. In responders to etanercept (3 patients) as determined by a routine 3-month clinical exam, a reduction of >30% in maximum PET signal in the carpal synovium and pisiform-triquetral compartment was observed at 1 month. An increase of >20% at 1 month was observed in clinical non-responders (2 patients). In the PsA patients, enthesitis and inflammatory activity in the nail bed were noted at baseline and can be quantified. In the patient with early OA, high bone remodeling activity was identified at sites of subchondral cysts and the thumb CMC joint, although only very early joint space narrowing was clinically noted.
Our initial studies show that high resolution PET/CT molecular imaging biomarkers can potentially provide novel means for documenting the pathogenesis of RA, PsA and OA in the hand. Extremity PET/CT may prove to be a useful tool for early monitoring of response to anti-TNF-alpha inhibitor or other newer therapies.
Disclosure: A. J. Chaudhari, None; A. Ferrero, None; F. Godinez, None; K. Yang, None; J. M. Boone, Varian Medical Systems, 2, Hologic, Inc., 2, Siemens Medical Systems, 2, Fuji Medical Systems, 2, Stanford Research Institute, 5, Artemis, 5 ; M. H. Buonocore, None; J. C. Hunter, None; D. K. Shelton, None; R. Hagge, None; S. W. Falen, None; R. D. Tesar, None; S. M. Naguwa, Abbott Laboratories, 8, Wyeth Pharmaceuticals, 8, Amgen, 8, Centacor, 8, Genentech and Biogen IDEC Inc., 8, UCB, 8 ; N. E. Lane, None; S. P. Raychaudhuri, None; R. D. Badawi, None.