Multiple choice The radiactive isotope used for locating brain tumors and damaged heart cells is iodine-131 thallium-201 technetium-99m sodium-24 Reveal answer Fill a bubble to check yourself C Correct answer Explanation Technetium-99m is used for locating brain tumors and damaged heart cells.Technetium-99m is probably the most widely used radioisotope in medicine today; it is a decay product of molybdenum-99.