SAT0644 T1rho mapping in the assessment of articular cartilage integrity of the knee in children with juvenile idiopathic arthritis
Authors: A.M. Barendregt, V. Mazzoli, C. van Gulik, M. van den Berg, A. Nassar Sheikh Rashid, K.M. Dolman, D. Schonenberg-Meinema, T.W. Kuijpers, M. Maas, A.J. Nederveen, R. Hemke
Journal: Annals of the Rheumatic Diseases (2018)

<h3>Background</h3> Early detection of microstructural damage to cartilage of patients with juvenile idiopathic arthritis (JIA) might prevent irreversible cartilage damage by timely treatment and follow-up of cartilage microstructure. New, quantitative MRI sequences such as T1ρ are possibly able to detect pre-erosive cartilage damage by quantifying proteoglycan (PG) loss of cartilage[.<sup>1–4</sup> <h3>Objectives</h3> To study feasibility of T1ρ mapping for assessment of articular cartilage integrity in children with JIA and study correlation between T1ρ relaxation time and the Juvenile Arthritis MRI score (JAMRIS)[<sup>5</sup> for disease activity. <h3>Methods</h3> After IRB approval and informed consent, the knee of patients with JIA or suspected JIA was imaged at 3T MRI using T2, pre and post contrast T1 and a sagittal T1ρ sequence with 400 Hz and spin lock time of 5, 10, 20, 40 and 50 ms. A region of interest (ROI) was drawn in articular cartilage of the knee on the T1ρ images, resulting in a mean T1ρ value of articular cartilage per patient. Using regular T2W and T1W pre and post contrast scans, JAMRIS was assigned to discriminate inflamed knees (JAMRIS ≥1) from non-inflamed knees (JAMRIS 0). In SPSS, Mann-Whitney U test and Spearman correlation coefficient were used to compare the mean T1ρ value between patients with and without arthritis on MRI and to correlate T1ρ values with JAMRIS score. ROI drawing was performed twice in 5 subjects. Intraclass correlation coefficient (ICC) was used to study intra-reader reliability. <h3>Results</h3> Of all 13 patients (median age 13.7 years), 7 patients had inflammation in the knee. No cartilage lesions were observed on standard MRI sequences. Acquisition of the T1ρ was successful and without artefacts in 100% of the children. Patients with inflammation in the knee showed a significantly longer T1ρ value than patients without inflammation in the knee: 36.3 ms (IQR 29.0–40.4) versus 27.7 ms (IQR 25.8–30.2), p=0.02. Correlation between T1ρ value and JAMRIS score was 0.76 (p=0.003). Repeatability of ROI drawing was characterised by ICCs&gt;0.99, p&lt;0.05. <h3>Conclusions</h3> This pilot study indicates that, even in the absence of cartilage erosions, significant differences are seen in cartilage integrity with higher T1ρ relaxation times in patients with knee arthritis. This might indicate loss of glycosaminoglycan content in active synovitis of the knee. Thus, our pilot data suggest that T1ρ could serve as an imaging biomarker for cartilage integrity, ultimately aiming to prevent irreversible cartilage damage and long-term disability in this young JIA population. <h3>References</h3> [1] Tsushima, et al. Rheumatol Int2012;32:2867–2875. [2] Takayama, et al. Eur J Radiol2013;82:e192–198. [3] Duvvuri, et al. Osteoarthritis Cartilage2002;10:838–844. [4] Regatte, et al. Acad Radiol2002;9:1388–1394. [5] Hemke, et al. Eur Radiol2013;23:1075–1083. <h3>Disclosure of Interest</h3> None declared