Dual-energy computed tomography molecular imaging of pigmented villonodular synovitis

Abstract

A 35-year-old woman presented with a 1 year history of non-traumatic gradual swelling of the first ray of the left foot, which had been painful for several weeks. Physical examination revealed a firm, slightly tender mass in the medial plantar soft tissues. Laboratory investigations, including levels of uric acid and CRP, were normal. Radiographs showed a soft tissue mass without' calcification or involvement of bones and joints. The patient underwent dual-energy CT (DECT) for further evaluation. Spectral analysis with two-material decomposition demonstrated an X-ray attenuation characteristic of iron within the distal synovial sheath of the flexor hallucis longus tendon ( Fig. 1 A and B), consistent with localized pigmented nodular tenosynovitis. The diagnosis was subsequently confirmed by percutaneous core needle biopsy ( Fig. 1 C). Pigmented villonodular synovitis (PVNS) encompasses a family of rare, usually benign, neoplastic processes arising from the synovium of joints, bursae and tendon sheaths, with pigmented nodular tenosynovitis occurring most commonly in the digits. While DECT has been proved effective for the detection, characterization and quantification of uric acid deposits in patients with gout [ 1 ], additional musculoskeletal applications have been suggested, including the detection of iron deposition in PVNS [ 2 ]. To our knowledge, this is the first description of non-invasive molecular imaging of PVNS using DECT.