Evaluation of Articular Cartilage in Knee Osteoarthritis Using Macromolecular Proton Fraction Mapping.

Abstract

Purpose: To evaluate the clinical utility of macromolecular proton fraction mapping for early osteoarthritis detection and compare its effectiveness with T₂* mapping in evaluating cartilage degeneration.

Methods: Eleven controls and 29 patients with osteoarthritis underwent 3.0T magnetic resonance imaging. Patients were classified based on the Kellgren-Lawrence grading system into mild osteoarthritis (KL 1-2, n = 9) and severe (KL 3-4, n = 20) osteoarthritis. Macromolecular proton fraction maps were generated from proton density-, T₁-, and magnetization transfer-weighted images using a single-point synthetic reference algorithm. T₂* maps were derived from multi-echo sequences. Macromolecular proton fractions and T₂* values were measured in 6 subregions of the femoral cartilage. Statistical analyses were conducted to compare values among the control, mild osteoarthritis, and severe osteoarthritis groups.

Results: Macromolecular proton fraction values decreased with increasing osteoarthritis severity. Compared to controls, both the mild and severe osteoarthritis groups exhibited significantly lower macromolecular proton fraction in the medial anterior and medial posterior regions. Additionally, the severe osteoarthritis group demonstrated significantly lower macromolecular proton fraction values in the medial central and lateral posterior regions compared to controls. In contrast, T₂* values generally increased with osteoarthritis severity. The mild and severe osteoarthritis groups had significantly elevated T₂* values in the medial anterior region compared to controls. Furthermore, the mild osteoarthritis group exhibited increased T₂* in the medial central region, whereas the severe osteoarthritis group had significantly higher T₂* in the medial anterior, medial posterior, and lateral posterior regions compared to controls.

Conclusion: Macromolecular proton fraction mapping demonstrated sensitivity to early-stage cartilage degeneration in osteoarthritis, suggesting its potential as a biomarker for early osteoarthritis detection. The combination of macromolecular proton fraction and T₂* mapping could enhance the biochemical assessment of cartilage integrity, providing valuable insights for early diagnosis and monitoring treatment effects in osteoarthritis.