Collagen degradation assessment with an in vitro rotator cuff tendinopathy model using multiparametric ultrashort‐TE magnetization transfer (UTE‐MT) imaging

Purpose This study aims to assess ultrashort‐TE magnetization transfer (UTE‐MT) imaging of collagen degradation using an in vitro model of rotator cuff tendinopathy. Methods Thirty‐six supraspinatus tendon specimens were divided into three groups and treated with 600 U collagenase (Group 1), 150 U collagenase (Group 2), and phosphate buffer saline (Group 3). UTE‐MT imaging was performed to assess changes in macromolecular fraction (MMF), macromolecule transverse relaxation time (T2m), water longitudinal relaxation rate constant (R1m), the magnetization exchange rate from the macromolecular to water pool (Rm0w) and from water to the macromolecular pool (Rm0m), and magnetization transfer ratio (MTR) at baseline and following digestion and their differences between groups. Biochemical and histological studies were conducted to determine the extent of collagen degradation. Correlation analyses were performed with MMF, T2m, R1m, Rm0w, Rm0m, and MTR, respectively. Univariate and multivariate linear regression analyses were performed to evaluate combinations of UTE‐MT parameters to predict collagen degradation. Results MMF, T2m, R1m, Rm0m, and MTR decreased after digestion. MMF (r = −0.842, p