Diagnosing Thyroid Cancer: Radionuclide Scanning Of The Thyroid

Thyroid Radionuclide Scanning

• This test is performed by a nuclear medicine specialist. After a small, safe amount of radioisotope (I-123 or Tc99) is taken by mouth or injected into a vein, the radiologist obtains pictures of the thyroid.
  
• Nodules can be seen as dark spots (called "cold") or bright spots (called "hot").
  
• Nodules that concentrate the radioisotope are "hot" and are usually making excessive thyroid hormone. "Hot" nodules are rarely associated with cancer and may not require FNAB investigation.
  
• Nodules that do not concentrate iodine are "cold" and are usually making less than normal amounts of thyroid hormone
   
  • More than 80%-85% of all thyroid nodules are "cold".
    
  • These nodules are typically more worrisome for cancer, and require evaluation with FNAB.