Three radioisotopes are being discussed in a chemistry class. technetium-99m has a half-life of 6 hours. rubidium-87 has a half-life of 50 billion years. which describes who would most likely use each isotope? a geologist would use technetium-99m because short-life indicates an older organism, and a doctor would use rubidium-87 because it allows for a more-accurate measurement of disease. a doctor would use technetium-99m because a short half-life indicates a quick measurement, and a geologist would use rubidium-87 because a longer half-life means that there is a longer time to measure old rock. a doctor would use technetium-99m because a short half-life indicates a quick measurement, and an archeologist would use rubidium-87 because anything containing carbon also contains rubidium. a geologist would use technetium-99m because a short half-life indicates an older organism, and an archeologist would use rubidium-87 because anything containing carbon also contains rubidium.