Quantitative 3D Ultrashort Echo Time Magnetization Transfer Imaging for Evaluation of Knee Cartilage Degeneration In Vivo

Background Recent studies suggest that macromolecular fraction (MMF) derived from three-dimensional ultrashort echo time magnetization transfer (UTE-MT) imaging is insensitive to the magic angle effect. However, its clinical use in osteoarthritis (OA) remains to be investigated. Purpose To investigate the feasibility of 3D UTE-MT-derived MMF in differentiating normal from degenerated cartilage. Study Type Prospective. Subjects Sixty-two participants (54.8 +/- 16.7 years, 30 females) with and without OA, plus two healthy volunteers (mean age 35.0 years) for reproducibility test. Field Strength/Sequence 3 T/UTE-MT sequence. Assessment A 3D UTE-MT sequence was employed to calculate MMF based on a two-pool model. Kellgren-Lawrence (KL) grade and Whole-Organ Magnetic Resonance Imaging Score (WORMS) were evaluated by three experienced musculoskeletal radiologists. KL grade was condensed into three groups: KL0, KL1-2, and KL3-4. WORMS was regrouped based on extent of lesion (extent group) and depth of lesion (depth group), respectively. The performance of MMF at evaluating the degeneration of cartilage was assessed via Spearman's correlation coefficient and the area under the curve (AUC) calculated according to the receiver-operating characteristic curve. Statistical Tests After normality check, one-way analysis of variance was used to evaluate the performance. Tukey-Kramer test was performed for post hoc testing. Results MMF showed significant negative correlations with KL grade (r = -0.53, P < 0.05) and WORMS (r = -0.49, P < 0.05). Significantly lower MMFs were found in subjects with greater KL grade (11.8 +/- 0.8% for KL0; 10.9 +/- 0.9% for KL1-2; 10.6 +/- 1.1% for KL3-4; P < 0.05) and in cartilage with greater extent (12.1 +/- 1.6% for normal cartilage; 10.9 +/- 1.6% for regional lesions; 9.6 +/- 1.7% for diffuse lesions; P < 0.05) and depth (12.1 +/- 1.6% for normal cartilage; 10.6 +/- 1.6% for partial-thickness lesions; 8.8 +/- 1.7% for full-thickness lesions; P < 0.05) of lesions. AUC values of MMF for doubtful-minimal OA (KL1-2) and mild cartilage degradation (WORMS1-2) were 0.8 and 0.7, respectively. Data Conclusion This study highlights the clinical potential of MMF in the detection of early OA. Level of Evidence 2 Technical Efficacy Stage 2