Thyroid imaging—Mediastinal uptake in thyroid imaging

Abstract

Fig. 1. Jl.nterior. RAO. and LAO views of a 1 thyroid scan show a cold nodule in the right lower pole (palpable edges marked). On the right side. extending inferiorly below the suprasternal notch (n' there is uptake in the mediastinum. (Chin is marked ··c.' configuration of the dilated esophagus that was seen on a barium esophagogram performed four years prior (Fig. 3). The patient gave a past history of having dysphagia and heartburn which first occurred 15 years ago. Four years before this admission he was diagnosed as having achalasia, and subsequently a Heller's myotomy procedure was performed. He claimed that since the operation he was free of symptoms except for the necessity of sleeping in a head-elevated position to prevent refluxation. Figure 3 was obtained during a barium swallow examination, performed one week after his operation. At that time, comparing films with his preoperative study, it was reported that the dilated esophagus remained unchanged, although there was only minimal delay of the barium passing into his stomach. On the day of the thyroid scan, the patient (in a fasting state) swallowed two 1231capsules. One hour later he ate breakfast. Although he was euthyroid, his oneand six-hour thyroid uptake values were lower than normal and the background counts were unusually high. After correlating the images with his previous barium esophagogram, the mystery of the extensive mediastinal uptake was explained on the presumption that a part of the radioiodine that he was given was retained in his megaesophagus and never reached the stomach to be absorbed. On follow-up, the cold nodule in the right lower pole of the gland was seen as a multicystic mass on ultrasonogram and was found to be a benign colloid nodule at surgery. Common: 1) Substernal extension of thyroid gland' 2) Normal esophageal activity when Tc-99m is ultCd l