Sharif M et al. Serum hyaluronic acid level as a predictor of disease progression in osteoarthritis of the knee. Arthritis Rheum 38:760-767, 1995; Hochberg MC et al. Serum levels of insulin-like growth factor 1 in subjects with osteoarthritis of the knee. Arthritis Rheum 37:1177-1180, 1994
Stable isotopes of an element do not change over time. Atoms of unstable isotopes â also called radioisotopes--change into other elements over time through radioactive decay. Radioisotopes are used in many medical imaging and diagnostic procedures, with the isotope Tc-99m being used in 80 percent of tests.
The radioisotope most widely used in medicine is technetium-99m, employed in some 80% of all nuclear medicine procedures â hence some 30 million per year, of which 6-7 million are in Europe, 15 million in North America, 6-8 million in Asia/Pacific (particularly Japan), and 0.5 million in other regions.