Optimal contrast for Na MRI

Introduction Na MRI has been used for a variety of tissue and organ imaging, including the brain, cartilage, the disc, breast, and kidneys. With the advent of high-field MRI scanners, high-resolution images can be obtained within clinically acceptable scan times. The sodium ions bound to tissues and organs can provide us with an invaluable information on the onset of disorder, such as osteoarthristis (OA) and degenerative disc diseases (DDD), through their concentration and quadrupolar interaction/relaxation. Slow motion of sodium ions may occur in cells, and its altered relaxation properties further provide important insights into cell viability, such as in the case of tumor tissue, or in the monitoring of muscle activity. In this paper, we are presenting two Na MRI constrast schemes, one selecting sodium ions with quadrupolar interation [1] and the other with quadrupolar relaxation. An optimization algorithm based on optimal control theory is used to achieve a maximum of the contrast.