Which of the following radio of Iodine is used for thyroid scan: September 2008

Ans. A: 1-123 The radionuclides that are used in thyroid scans are two isotopes of iodine, 1-131 and 1-123, and an isotope of technetium known as 99m Tc. Technetium scanning is preferred for some diagnostic workups because it is relatively fast and does not require the patient to fast beforehand. Many prefer to reserve 1-131 for follow-up evaluations of cancer patients, and use 1-123 for thyroid uptake tests and routine thyroid scans. The reason for the distinction is the higher radiation burden of 1-131.