Osteoarthritis and malignant neoplasms contribute to significant morbidity and mortality in the United States of America. The early diagnosis of osteoarthritis will be useful for instituting appropriate therapies. Similarly, the ability to accurately detect tumor response to chemotherapy may guide to clinical management of the cancer patient. We have developed a magnetic resonance imaging (MRI) method that exploits the magnetic relaxation of water induced by low frequency interactions. Spin-lattice relaxation in the rotating frame (T 1ρ) is sensitive to interactions that have a correlation time on the order of the reciprocal of the spin-lock amplitude. We demonstrate that water T1ρ relaxation is sensitive to the loss of proteoglycan from the extra-cellular matrix of cartilage. We further show that T1ρ imaging can be performed on a clinical MRI system, to demarcate a cartilage lesion in a volunteer. A biophysical mechanism based on proton exchange is developed and tested to explain the T1ρ dispersion characteristics of peptide solutions and cartilage. Finally, we show that T1ρ measurements can detect the response of murine tumors to cyclophosphamide therapy 18 hours after drug administration. In conclusion, this thesis presents data to suggest that T1ρ-MRI may be useful for the early diagnosis of osteoarthritis and for the early detection of tumor response to chemotherapy
