Radiology, Vol 168, 753-757, Copyright © 1988 by Radiological Society of North America
Recurrent thyroid carcinoma: characteristics on MR images
W Auffermann, OH Clark, S Thurnher, M Galante and CB Higgins
Department of Radiology, University of California, School of Medicine, San Francisco 94143.
Magnetic resonance (MR) imaging was used in 32 patients, including eight
with benign disease, after partial or total thyroidectomy to determine
sensitivity and specificity of MR imaging in the detection of tumor
recurrence, to compare signal intensities of scar versus recurrent tumor
qualitatively and quantitatively, and to define the extent of recurrent
tumor. Findings from surgery (n = 23), needle biopsy (n = 1), or clinical
follow-up (n = 8) were used for verification. Of 24 patients with primary
thyroid carcinoma, 15 had recurrence and nine had a normal postsurgical
thyroid bed. Diagnosis from MR images was correct in 20 cases, but false
positive in three and false negative in one. Local recurrence was
characterized by low to medium intensity on short repetition time
(TR)/short echo time (TE) images and medium to high intensity on long
TR/long TE images. Scar in the normal postsurgical thyroid bed showed low
intensity on both short and long TR/TE images. Local recurrence of thyroid
carcinoma and lymph node metastasis produced positive contrast compared
with muscle on short TR/short TE (31 + 19%) and long TR/long TE (85 + 30%)
images; fibrosis produced negative contrast, particularly on long TR/long
TE (- 56, -80%) images. These results indicate the capability of MR imaging
in the evaluation of recurrence of thyroid tumors and in the
differentiation of abnormal tissue due to tumor recurrence from
postoperative fibrosis by means of signal contrast relative to a reference
tissue.
