<prompt> Most sensitive investigation for preoperative localization of abnormal parathyroid glands is:Neck ultrasound99mTc labelled Sestamibi isotope scanCT scanMRI  <response>: Neck ultrasound locates glands in approximately 75 of cases. 99mTc labeled Sestamibi isotope scans identify approximately 80 of abnormal parathyroid glands.CT MRI is not indicated prior to first time neck exploration. 