False-positive scalp activity in ¹³¹I imaging associated with hair coloring

A patient with metastatic papillary thyroid carcinoma (after surgical resection of tumor and positive lymph nodes) undergoing thyroid ablation therapy with ¹³¹I is described. Wholebody scintigraphy was performed 1 wk after ablation therapy to evaluate the presence of residual disease. The whole-body images demonstrated an artifact caused by tracer accumulation in the patient's scalp related to recent hair coloring. Common etiologies of false-positive ¹³¹I scintigraphic findings are briefly reviewed. The importance of taking preventative measures to decrease the number of false-positive findings and recognizing these findings when they occur is discussed.