<prompt> Dye used in SPECT -0-14Tc - 99Nitrogen - 16Iodine 124  <response>: Ans. is b i.e., Tc - 99 o The radioisotopes typically used in SPECT to label tracers are Iodine - 123, technetium - 99m, xenon -133, thallium - 201, and fluorine - 18. 