Background Digital ulceration (DU) and reduction in hand function due to Raynaud's phenomenon (RP) are more common and severe in Systemic Sclerosis (SSc) than in other Connective Tissue Diseases because of reduced capacity of the digital arteries, which in turn is caused by neointima proliferation. While the presence of DU and loss of hand function reflect the severity of the hand vasculopathy, to date there is no direct surrogate outcome measure of neointima proliferation in Scleroderma hands which could predict onset of SSc in patients with severe RP. Non-contrast Magnetic Resonance Angiography (MRA) employing Time Of Flight technique (TOF) has become more and more utilized for assessing vascular pathologic conditions with MRI. The TOF allows the visualization of the blood flow by different magnetization and therefore contrast resolution between the water nuclei flowing in the arteries and the stationary nuclei of the surrounding tissues in a definite volume.
Objectives To determine the proof of concept, face and content validity of non-contrast hand MRA by TOF as imaging outcome measure of fibroproliferative vasculopathy in Scleroderma.
Methods Twenty hands were scanned from 8 SSc patients (of which 4 with current DU) and 10 healthy volunteers (HV). MRI scans were performed on a 3T Magnetom Verio (Siemens Healthcare). A VIBE 3D T1 scan of 3 minutes and a 2D TOF sequence of 8 minutes were performed using Time of Echo of 5 milliseconds (ms) and repetition time (TR) ranging from 24 to 72 ms when needed. Post-processing analysis was undertaken with OsiriX software. Digital arterial flow index (DAFI) was calculated as % of the ratio of digital arteries flow volume and the respective finger volume. DAFI values were analysed by Graph prism software by two-way-ANOVA or unpaired two-tailed t-test as appropriate.
Results Digital arteries were visualized at TR of 24 ms in 17/20 hands. Three HV required increased TR. Seventy native TOF images were post-processed to obtain the volume of the digital arteries by OsiriX segmentation. DAFI of HV was in average 1.21 (STDV 0.39) vs 0.37 (STDV 0.18) of SSc patients (p<0.0001). These results correlated with Cochin hand function score that was obviously worse in the SSc patients vs HV (p<0.05). Within the SSc patients, fingers with worse vascularization (e.g. affected by DU) had an average DAFI of 0.24 (STDV =0.08) vs 0.40 (STDV 0.18) of the fingers without DU (p=0.02). DAFI of the different fingers in HV had no statistically significant difference. Representative images of one SSc and a HV hand are represented in figure 1.
Conclusions Time of Flight MRA is a sensitive, non-invasive tool to assess arterial flow volume in SSc hands. While definite validation with tissue biopsies is poorly feasible, the correlation of the DAFI with functional score and presence of DU is strongly supporting the face and content validity of the test. Longitudinal evaluation of a large cohort of patients with SSc and secondary RP is warranted to determine the sensitivity to change, the specificity and the potential predictive value of the test in diagnosing fibroproliferative vasculopathy in the hands of patients affected by RP.
Disclosure of Interest None declared