The application of SPECT/CT scintigraphy with MIBI-Tc 99m in the diagnosis of thyroid nodules - a preliminary report

Abstract

Introduction: Thyroid cancer diagnosis is based mainly on fine needle aspiration biopsy (FNAB) performed under ultrasonography guidance. Questions arise in cases of an inconclusive FNAB result - when there is no clear evidential data to support the existence of a malignant lesion or when there are any other reasons which make the decision process difficult, such as the patient’s age or coexisting diseases. To clarify this issue the patient should be encouraged to undergo surgery treatment or to be followed up. Thyroid scintigraphy with an oncophilic tracer such as MIBI-Tc^99m may be helpful.
Material and methods: The study comprised a group of 12 patients, aged 54-75 (av. 63.5) years, who, in 2009, underwent planar and SPECT/CT thyroid scintigraphy with MIBI-Tc^99m using washout method. The tumour/background ratio in early and delayed images was calculated and the wash-out ratio was estimated. Patients with increased focal lesion uptake were operated on and the lesions were histopathologically verified.
Results: Abnormal scintigraphy results were obtained in 8 patients (10 lesions) and normal results in 4 patients (5 lesions). Out of 15 studies, in 13 cases the washout from the lesion was observed within 2 hours. It was noticed that the images obtained with SPECT/CT washout method were clearer and easier to read in comparison to planar studies. Three patients with an abnormal results underwent surgery and had benign histopathology results after the operation, in 3 patients the observation is being confirmed without any increase in malignancy suspicions, and 2 were lost for observation.
Conclusions: Our preliminary results do support the use of MIBI-Tc99m in the evaluation of indeterminate thyroid nodules. To validate the hypothesis that MIBI-Tc^99m may be used to exclude malignancy in lesions indeterminate by FNAB we propose to use SPECT-CT derived images and standardized evaluation criteria.
(Pol J Endocrinol 2010; 61 (5): 422-426)