Ultra-high frequency ultrasound (UHFUS) applications in Sjogren syndrome: narrative review and current concepts

Primary Sjogren's syndrome (SS) is a systemic autoimmune chronic inflammatory disease with predominant involvement of the exocrine glands, particularly the salivary glands (SGs). The role of salivary glands ultrasound (SGUS) in the work-up of patients with primary Sjogren syndrome (SS) is progressively increasing due to its useful support in diagnosis and follow-up as a widely available, repeatable, non-invasive and safe technique. Although SGUS is not yet included in the dominant primary SS classification, several studies supported its inclusion in the American College of Rheumatology/European League Against Rheumatism criteria. In this context, a novel imaging technique, ultra-high frequency ultrasound (UHFUS), is being explored. Compared to the frequencies used in conventional ultrasound (US) (up to 22 MHz), UHFUS operates with higher frequencies (30-100 MHz) allowing for outstanding image resolution, up to 30 µm. UHFUS permits the scan of both major and minor SGs, opening new avenues for the integration of tissue and imaging biomarkers. Although further studies are needed to confirm its role, this novel imaging technique might lead to several potential improvements, including earlier diagnosis, reduction of unnecessary and inadequate biopsies and better management and follow-up of patients with primary SS.