The British Journal of Radiology, Vol 73, Issue 870 627-635, Copyright © 2000 by British Institute of Radiology

ARTICLES

False positive 131I whole body scans in thyroid cancer

G Mitchell, BE Pratt, L Vini, VR McCready and CL Harmer
Thyroid Unit, Royal Marsden Hospital NHS Trust, Sutton, Surrey, UK.

Well differentiated thyroid cancer is a rare disease in the UK. It is the only cancer which, having metastasized, remains curable by radioisotope therapy with 131I. The main indication for administering repeat doses of 131I is the appearance of abnormal uptake in a whole body scan following diagnostic or therapeutic 131I administration. False positive scans, showing the presence of 131I uptake in the absence of residual thyroid tissue or metastases can occur, although they are uncommon. Unless recognized as a false positive, 131I uptake may result in diagnostic error and lead to administration of an unnecessary therapy dose. We describe a series of nine patients in whom the scans showed false positive uptake of 131I, including cases where the cause of the uptake is still uncertain. We demonstrate the common sites of false positive uptake, discuss the underlying mechanisms and suggest a systematic approach to the interpretation of whole body scans in order to prevent unnecessary treatment with 131I.

This article has been cited by other articles:

				C. Ma, J. Xie, and A. Kuang Is Empiric 131I Therapy Justified for Patients with Positive Thyroglobulin and Negative 131I Whole-Body Scanning Results? J. Nucl. Med., July 1, 2005; 46(7): 1164 - 1170. [Abstract] [Full Text] [PDF]

				E. L. Mazzaferri and R. T. Kloos Current Approaches to Primary Therapy for Papillary and Follicular Thyroid Cancer J. Clin. Endocrinol. Metab., April 1, 2001; 86(4): 1447 - 1463. [Full Text]