Multiple choice Which of the following is the most commonly used medical radioisotope? Uranium-238 Molybdenom-99 Krypton-81 Technetium-99 Reveal answer Fill a bubble to check yourself D Correct answer Explanation Technetium-99m is a meta-stable nuclear isomer of technetium-99, symbolised as 99 m Tc. It is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used medical radioisotope.