Magnetization transfer based contrast for imaging denatured collagen

Purpose: To study of the sensitivity of various NMR and MRI methods and parameters to the degree of thermal denaturation of collagen. Materials and Methods: Collagen type I powder was washed with methanohchloroform to remove traces of lipids and then suspended in saline. Denaturation was carried out by heating the suspension for 5-120 minutes at a temperature range of 50-100°C. The NMR methods tested were two T₂ filter methods: Goldman-Shen (GS) and Edzes-Samulski (ES); magnetization transfer contrast (MTC); double quantum filtering (DQF) and high resolution spectroscopy. MRI contrasts based on these methods were compared. Results: The following parameters were found to be sensitive to denaturation of collagen: 1) the amount of spins that experience high dipolar interactions as assessed by DQF; 2) MTR; 3) k_wT _1w (where k_w is the magnetization transfer rate from water to collagen, and T_1w is the water protons longitudinal relaxation time); and 4) aliphatic residues content. The contrast between native and denatured collagen was improved by all the tested methods, with ES and DQF producing the highest contrast. Conclusion: Methods depending on T₂ filtering and DQF were found to be sensitive to the degree of thermal denaturation of collagen and improve the contrast between native and denatured collagen.