T2 Mapping MRI for Differentiation of Hemarthrosis and Nonhemorrhagic Joint Effusion in Patients with Hemophilia

Background Differentiating acute hemarthrosis from nonhemorrhagic effusion in patients with hemophilia is clinically challenging and may require invasive joint aspiration. Purpose To determine whether T1 or T2 mapping MRI at 3 T can noninvasively differentiate acute hemarthrosis from nonhemorrhagic joint effusion in patients with hemophilia. Materials and Methods In this prospective study, ex vivo validation was first performed using blood dilution series from three control participants to determine blood detection limits and 14-day stability for T1 and T2 mapping at 3 T. Consecutive patients with hemophilia and joint effusion scheduled for arthrocentesis or surgery were then recruited (September 2019 through December 2022) to quantify T2 relaxation times in vivo. Arthrocentesis- or surgery-based classification of joint fluid served as the reference standard. Groups were compared using the Mann-Whitney U test, and diagnostic performance was evaluated using receiver operating characteristic analysis. Results Thirty male participants were evaluated (mean age, 35 years ± 17 [SD]). Ex vivo validation demonstrated that T2 mapping enabled reliable discrimination of blood concentrations down to 0.39%, with results remaining stable over 14 days, whereas reliable discrimination with T1 mapping was limited to dilutions greater than 12.5%. In the clinical sample, in vivo T2 relaxation times were lower in participants with acute hemarthrosis (median, 185 msec; range, 80-322 msec) than in those with nonhemorrhagic effusions (median, 523 msec; range, 368-747 msec; P < .001). A T2 cutoff value of 361 msec differentiated hemorrhagic (14 of 30 [47%]) from nonhemorrhagic (16 of 30 [53%]) effusions with 100% sensitivity (14 of 14 [100%; 95% CI: 77, 100]) and 100% specificity (16 of 16 [100%; 95% CI: 79, 100]; area under the receiver operating characteristic curve, 1.00). Conclusion T2 mapping MRI at 3 T enabled noninvasive differentiation of hemarthrosis and nonhemorrhagic joint effusion in participants with hemophilia, with excellent diagnostic performance. © RSNA, 2026 See also the editorial by Oca Pernas in this issue.