Nasolacrimal Duct Obstruction on ¹³¹I SPECT/CT: Atypical False-positive Paranasal Radioiodine Uptake as a Complication of Single-dose RAI Treatment

Abstract

Nasolacrimal duct obstruction (NLDO) is a rare complication after radioiodine therapy and may cause false positive 131 I uptake at the point of obstruction in 131 I whole body scan. Here, we report a 59-year-old female patient with papillary thyroid cancer treated with total thyroidectomy followed by 131 I therapy. 131 I whole body scan revealed focal uptake in the head. Single photon emission computed tomography/computed tomography (CT) showed focal uptake at the right proximal nasolacrimal duct. The ophthalmologic examination and the diagnostic maxillofacial CT confirmed the diagnosis of NLDO.

False-positive radioiodine uptake after radioiodine treatment in differentiated thyroid cancer

“…Overall, the literature showed 145 case reports and two series regarding false-positive 131 uptake after RIT For the reasons stated above, we excluded 129 papers, considering only those in which SPECT/CT was performed. A total of 18 papers were thus included: 1 series [17] and 17 case reports [18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34]. The series reported 23 cases of falsepositive results: 15 in the chest, six in the pelvis, one in the cranium, and one in the abdomen.…”

“…Three cases reported uptake in the head: two surgical clips, and one on one eye [30,31,33]. A few other cases were in other sites [24,32]. In many cases, accumulation of radioiodine and the cause was simply classified as "undetermined".…”