Nuclear medicine thyroid scanning does not conclusively determine whether thyroid nodules are benign or malignant; cold nodules on thyroid scans will still require biopsy. Nuclear medicine thyroid scans are useful to evaluate the functional status of thyroid nodules in patients who are hyperthyroid.
Sources:
American Thyroid Association (ATA) Guidelines Taskforce on Thyroid Nodules and Differentiated Thyroid Cancer, et al. Revised American Thyroid Association management guidelines for patients with thyroid nodules and differentiated thyroid cancer. Thyroid. 2009 Nov;19(11):1167-214. PMID: 19860577.
Lee JC, et al. Thyroid scans. Aust Fam Physician. 2012 Aug;41(8):584-86. PMID: 23145398.
Welker MJ, et al. Thyroid nodules. Am Fam Physician. 2003 Feb 1;67(3):559-66. PMID: 12588078.