Abstract: ^\rm99\rmT\rmc^\rmm\rmO_4^ - thyroid imaging is one of the classic items in nuclear medicine imaging, providing a simple and effective method for the assessment of thyroid function status. It is generally believed that patients do not need special preparation before examination, but recent studies have found that the intake of large doses of iodine in the short term can affect the uptake of ^\rm99\rmT\rmc^\rmm\rmO_4^ - by the thyroid gland, while the effects of other non-thyroid-related drugs on thyroid imaging are rarely reported. The authors reported two cases of ^\rm99\rmT\rmc^\rmm\rmO_4^ - thyroid imaging failure in patients treated with ⁹⁹Tc-methylenediphosphonate. The images showed a decreased uptake of ^\rm99\rmT\rmc^\rmm\rmO_4^ - in the thyroid and significant uptake in multiple organs and large blood vessels in the whole body. The examination procedure was reviewed and the possible reasons for the imaging failure were preliminatively analyzed, and some suggestions were put forward for avoiding similar problems in the future.