The Choline (Cho) peak is a heterogeneous peak representing various choline-containing compounds such as acetylcholine, phosphocholine (lecithin), glycerophosphocholine, and various other intermediates of phospholipids metabolism. It is an indicator of cell density and cell wall turnover. Elevated levels are found in tumors, especially malignant ones, and in certain demyelinating diseases. Choline resonance presents at 3.22 ppm. Studies have shown there is also a direct association between Cho and levels of Ki-67, a protein expressed in all phases of the cell cycle except GO that serves as a good marker for cellular proliferation. This observation makes Cho a reliable predictor of cellular activity in tumor tissue.