I am interested in muscle function for maximal athletic performance and also for defects in clinical diseases, such as, diabetes and inflammatory myositis. We correlate the muscle anatomy observed in various MRI exams with biochemical energy requirements for muscle contraction as measured as ATP and PCr levels by MRS (magnetic resonance spectroscopy).
We are currently investigating muscle defects in patients with inflammatory diseases, such as dermatomyositis and polymyositis. MRI exams showed that inflammation and fat infiltration in muscle diseases are initially concordant with energy deficits of essential ATP and PCr. Low levels of ATP and PCr persist for greater lengths of time, thereby indicating biochemical artifacts as the major defects in muscle contraction. However, these diseases are now being redefined with newer techniques, for example, MR-DWI and MR-DTI (MR-diffusion weighted and MR-diffusion tensor imaging). These techniques examine muscle tissue on a molecular scale by indicating the motion and direction of cellular water and the architecture of muscle fibers. Initial studies showed that inflammation produces greater water movement along the fiber tracks and also shorter fibers. By contrast, fat infiltration indicates slower water motion and even more distortion of fiber structure. These findings are important as they relate to the movement of metabolites and ATP, which are essential for muscle contraction. Improvements in DWI and DTI values may relate to improvements in muscle strength, advancement in clinical evaluations, means for new drug discovery.
Park, J.H., Lee, B.C. and Olsen, N.J. Fatigue and Weakness in Myositis Patients: Dermatomyositis, Polymyositis and Inclusion Body Myositis. Human Fatigue, (Craig Williams. ed.) Chapter 12, 313-337, 2009.
Qi, J., Olsen, N.J., Price, R.R., and Park, J.H. Diffusion Weighted Imaging of Inflammatory Myopathies: Polymyositis and Dermatomyositis. J. Magnetic Resonance Imaging. 27, (1) 212-217, 2008.
Olsen, N.J., Qi, J., and Park, J.H. Imaging and Skeletal Muscle Disease. Current Rheumatology Reports. 7, 106-114, 2005.
Niermann, K.J., Olsen, N.J., and Park, J.H. Magnesium Abnormalities of Skeletal Muscle in Dermatomyositis and Juvenile Dermatomyositis. Arthritis Rheum. 46, (2) 475-488, 2002.
Park, J.H., Kari, S., King, L.E., and Olsen, N.J. Artificial Neural Network Analysis of P-31 MR Spectroscopy Data for Longitudinal Evaluation of Muscle Diseases: Dermatomyositis. NMR in Biomedicine. 11, 245-256, 1998.