Recent advances in non-invasive imaging of systemic sclerosis-related digital ulcers.

Digital ulcers are a major source of pain and disability in patients with systemic sclerosis. Current treatments are not ideal, yet drug development for digital ulcers is hampered by a lack of objective outcome measures to facilitate clinical trials. Advances in non-invasive imaging could provide a way forward. This review article first describes the rationale for non-invasive imaging of digital ulcers in both clinical practice and research. In clinical practice, magnetic resonance imaging allows early diagnosis of underlying osteomyelitis, and smartphone imaging allows early (remote) identification of digital ulcers. In research, non-invasive imaging provides new insights into pathophysiology, as well as the ability to measure precisely digital ulcer surface area and volume. The imaging techniques discussed include mobile phone photography, ultrasound, laser Doppler methods and emerging technologies (multispectral imaging and polarisation-sensitive optical coherence tomography). Between them, these methods hold promise as outcome measures for early and later phase trials, but first require full validation.