MR imaging characteristics of recurrent thyroid tumors

MR imaging was used to evaluate 32 patients after partial or total thyroidectomy. Surgical (n = 25) or clinical (n = 7) follow-up was done. Of 23 patients with primary thyroid carcinomas, MR imaging disclosed recurrence in 15 and no recurrence in eight. There were two false-positive diagnoses and one false-negative diagnosis. Nine patients who had undergone surgery for benign disease were studied to assess the appearance of the thyroid bed after thyroidectomy. Local recurrence of carcinoma was characterized by low to medium signal intensity on T1-weighted images and medium to high signal intensity on T2-weighted images. Scar tissue has low intensity. Coronal and sagittal images provided definition of local and mediastinal extension and metastasis. Thus, MR imaging can be used to evaluate recurrence of thyroid tumors and to differentiate recurrence from postoperative fibrosis