CEST and ZAP MRI Reveal Age-Related Biochemical Changes in Knee Joint Tissues

Motivation: Aging leads to biophysiological changes in knee joint tissues that precede structural degeneration; conventional MRI techniques lack the sensitivity to detect these early alterations. Goal(s): The goal of this study is to investigate CEST and ZAP macromolecule exchange MRI to identify biochemical markers of age-related changes in knee tissues. Approach: Four young and three senior individuals were scanned with a combined CEST and ZAP MRI protocol. ZAP analyzed exchange proton fractions and corresponding apparent T2 relaxation times, while CEST assessed specific exchange groups. Results: Senior subjects exhibited reduced proton fractions and lower glycosaminoglycan content, indicating early tissue degeneration. Impact: CEST showed decreased hydroxyl (-OH) peak, suggesting age-related glycosaminoglycan decline, while ZAP showed increase in restricted protons fraction (Fr) in elders, suggesting decreased hydration. This parametric MRI approach could provide early biomarkers for diagnosing and monitoring joint tissue alterations.