Nuclear Scanning in Evaluation and Treatment of Thyroid Disorders: A Beginners Guide

Thyroid disorders are common worldwide and the biggest fear amongst most patients with neck swellings is thyroid cancer. We need simple techniques in our clinics to diagnose and treat patients with thyroid disorders in order to initiate the right treatment as well as to alleviate patient’s anxiety. Incomplete information and ignorance regarding these techniques prevents many clinicians to benefit from these simple and cost effective methods. Thus radioisotope modalities are still underutilized in many countries. We put together a short review by compiling our experience of common ways to effectively utilize radioisotope techniques in thyroid clinics along with literature review from current guidelines in a most simple and easy to understand way for the clinician. Vandana K Dhingra* Department of Nuclear Medicine, All India Institute of Medical Sciences, India Vandana K Dhingra Clinics in Oncology Nuclear Medicine Remedy Publications LLC., | http://clinicsinoncology.com/ 2017 | Volume 2 | Article 1260 2 maximum benefits from the scanning. In 2009–2010 American Thyroid Association (ATA) and other guidelines have published their recommen dations suggesting that the thyroid scintigraphy is useful only in patients with nodule diameter greater than 1 cm, provided that TSH concentration is subnormal. The role of scintigraphy in this case is to show whether a nodule, that is manifested in ultrasound, is a focus of excessive hormonal activity (hot nodule) or accu mulates the radiotracer at a level similar to or lower than the rest of the gland (warm or cold nodule). Since the hot nodules are rarely malignant, according to ATA guidelines fine-needle biopsy is not necessary in such a case. At the same time, performing Scintigraphy in all patients with nodular goitre is not recommended by experts, since adequate assessment obtained with ultrasound and cytology is sufficient in most cases [6]. Patient preparation for thyroid scintigraphy Usually no prior patient preparation is needed for Thyroid Scintigraphy. In case the patient is taking thyroid hormone replacement therapy or iodine, the study should be done four to six weeks after stopping these drugs. The female patients who are pregnant or breast feeding the babies should inform the nuclear medicine physician before taking a diagnostic test. Although the radiation exposure involved is very low, however, in case of pregnancy the procedure would be performed only id really needed at that point (benefit vs. risk evaluation). The Basic Gamut of Nuclear Medicine in Thyroid Disorder Evaluation While referring and interpreting results of thyroid Scintigraphy, the physician should be aware of the current situation of the patient: • History of thyroid disease • Ultrasound findings • Current TSH Used drugs, in particular thyroid hormones, antithyroid drugs and iodine-containing agents (amiodarone, disinfectant and expectorant drugs), these may have effect on overall functioning of the thyroid gland as well as on scan findings Thyroid Scintigraphy is functional imaging and is interpreted with full knowledge of the patient status for optimal results [6]. • Post surgical detection of remnant /metastasis –diagnostic • Ablation of remnant/metastasis –therapeutic Principles of interpretation of thyroid scan Thyroid scintigraphy produces an image of distribution of radiotracer in thyroid parenchyma. It helps to diagnose thyroid diseases on the basis of level of radiotracer uptake as compared to surrounding structures, radiotracer distribution in thyroid, any extrathyroidal uptake etc. It gives an idea about thyroid location. It also helps to know thyroid morphology including its size and overall & regional level of thyroid function both qualitatively and quantitatively. A normal thyroid scan Normally the gland is symmetrical and the lateral borders of lobes are straight to convex. Tracer is normally seen in salivary glands and in capillary network of the neck tissue also, called as ‘blood pool’. This is seen as a light background along the neck contour. Graves’ disease Typical clinical features of Graves’ with biochemical parameters and a thyroid scan would complete workup of these patients. Radioiodine therapy is the treatment of choice in non-complicated, small to medium sized goitres . Thyroid Scintigraphy usually shows uniform diffuse enlargement. Tracer is uniformly distributed in the thyroid. Not normally seen pyramidal lobe (a remnant of thyroglossal duct) can be seen in a hypertrophied gland. Tracer is barely trapped in salivary glands due to less tracer availability for extraction to them consequent to higher trapping by thyroid.