Background/Objectives: Given the significant economic and social burden of osteoporosis, there is growing interest in developing an efficient alternative to the traditional dual-energy X-ray absorptiometry (DXA). Radiofrequency Echographic Multi Spectrometry (REMS) is an innovative, non-ionizing imaging technique that recently emerged as a viable tool to diagnose osteoporosis and estimate the fragility fracture risk. Nevertheless, its clinical use is still limited due to its novelty and continuing uncertainty of long-term performance. Methods: In order to evaluate the accuracy of the REMS, a systematic review of the English-language literature was conducted. Three databases were searched for relevant publications from 1 January 2015 until 1 December 2024 using the keyword combinations “(radiofrequency echographic multi spectrometry OR REMS) AND (dual-energy X-ray absorptiometry OR DXA)”. The initial search yielded 602 candidate articles. After screening the titles and abstracts following the eligibility criteria, 17 publications remained for full-text evaluation. Results: The reviewed studies demonstrated strong diagnostic agreement between REMS and DXA. Additionally, REMS showed enhanced diagnostic capabilities in cases where lumbar bone mineral density measurements by DXA were impaired by artifacts such as vertebral fractures, deformities, osteoarthritis, or vascular calcifications. REMS exhibited excellent intra-operator repeatability and precision, comparable to or exceeding the reported performance of DXA. The fragility score (FS), a parameter reflecting bone quality and structural integrity, effectively discriminated between fractured and non-fractured patients. Moreover, REMS proved to be a radiation-free option for bone health monitoring in radiation-sensitive populations or patients requiring frequent imaging to assess fracture risk. Conclusions: This current study underscores the robustness of REMS as a reliable method for diagnosing and monitoring osteoporosis and evaluating bone fragility via the FS. It also identifies critical knowledge gaps and emphasizes the need for further prospective studies to validate and expand the clinical applications of REMS across diverse patient populations.

Background: Systemic sclerosis (SSc) is an autoimmune disease with interstitial lung disease (ILD) representing the leading cause of mortality. Diaphragmatic muscle impairment, which may contribute to respiratory dysfunction, is underexplored in SSc. Objective: This study aimed to assess diaphragmatic thickness using HRCT in patients with SSc-ILD and to investigate whether this parameter correlates with disease severity and clinical outcomes. Methods: We conducted a multicentric retrospective observational study that included 161 participants: 69 with SSc-ILD and 92 matched controls without pulmonary disease. Preliminary findings from this cohort were previously communicated as a conference abstract at EULAR 2024. Diaphragmatic thickness was measured on axial and coronal CT images at the celiac axis level by two independent radiologists. Clinical and functional parameters were collected, including forced vital capacity (FVC), diffusing capacity for carbon monoxide (DLCO), echocardiographic findings, and 6 min walking test performance. Results: The left hemidiaphragm was significantly thinner in patients with SSc-ILD compared with controls (2.98 ± 1.04 mm vs. 3.44 ± 0.97 mm; p = 0.004), while the right hemidiaphragm showed a non-significant trend toward reduction (3.21 ± 1.09 mm vs. 3.52 ± 1.05 mm; p = 0.072). Thinning of the right hemidiaphragm correlated significantly with lower FVC (p < 0.05). ROC analysis identified an optimal left diaphragm cut-off of ≤3.115 mm (AUC = 0.635, 95% CI: 0.556–0.709, sensitivity = 66.7%, specificity = 60.9%). No associations were found with the autoantibody profile, disease duration, or treatment. Interobserver reliability was excellent (Bland–Altman mean difference −0.002 mm, p = 0.95). Conclusions: HRCT-measured left hemidiaphragm thickness is significantly reduced in patients with SSc-ILD compared with controls, and right hemidiaphragm thickness correlates with impaired lung function. Although its discriminative performance is modest (AUC 0.635), this parameter may serve as a supplementary zero-burden addition to routine HRCT evaluation alongside pulmonary function tests. The retrospective cross-sectional design precludes conclusions about causality or prognosis; prospective studies incorporating concurrent functional diaphragm assessment are warranted.