True statement:

Other high yielding points I127 is stable iodine isotope I-131 Has half life of 8 days The gamma-emitting isotopes iodine-123 (half-life 13 hours) used as nuclear imaging tracers to evaluate the anatomic and physiologic function of the thyroid. Iodine-125 is commonly used by radiation oncologists in low dose rate brachytherapy in the treatment of cancer at sites other than the thyroid, especially in prostate cancer. When I-125 is used therapeutically, it is encapsulated in titanium seeds and implanted in the area of the tumor, where it remains. The low energy of the gamma spectrum in this case limits radiation damage to tissues far from the implanted capsule. Iodine-125, due to its suitable longer half-life and less penetrating gamma spectrum, is also often preferred for laboratory tests that rely on iodine as a tracer that is counted by a gamma counter, such as in radioimmunoassaying