Correlation between radioactive isotope scan and ultrasonography of the thyroid in patients with different thyroid diseases

ABSTRACT

In a prospective series of 114 patients, radioisotope scan [RIS] and ultrasonic scan [US] of the thyroid gland were compared in detail. US is the most sensitive test in detecting multi-nodularity [47 percent] versus [25 percent] by RIS and [16 percent] by clinical examination. While RIS is the most sensitive test in detection of residual or recurrence after thyroidectomy [11 percent] versus [7 percent] by US and [5 percent] by clinical examination. Solitary nodules were [46 percent] clinically, 39 percent with RIS and [28 percent] by US. Also RIS and US can differentiate effectively between thyroid and extrathyroid swellings which clinically resemble thyroid. So, the use of RIS and US alter the primary evaluation of thyroid nodularity based on palpation. In spite of the high sensitivity of thyroid US in detection of multinodular goitre [MNG], however, this can not determine the function of the nodules and so, can not exclude neoplasia. Three cases of MNG by US were found by RIS to be as following one case with solitary cold nodule, another case showed MNG with dominant cold nodule, both proved to be follicular adenomas after operation. The third case showed 2 cold nodules the largest of them was found to be follicular carcinoma. Malignancy was detected In [16 percent] of patients with solitary cold or hypofunctioning nodules, nil in patients with solitary cold pure cystic nodules, [14 percent] of cases with solitary cold mixed nodules and [25 percent] in cold solid nodules. In the later group no malignancy was detected in cold hyperechoic solid nodules, [20 percent] malignancy was found in isoechoic solid cold nodules and [43 percent] in hypoechoic solid cold nodules. So, we recommend to begin with RIS in thyroid diseases. If MNG, hot nodules or residual or recurrence was detected US can not add new informations. If absent thyroid tissue [without thyroidectomy], US helps in differentiation between true absence and failure of uptake e.g. in thyroiditis or suppression by hot nodule or malignancy. Also in solitary cold or hypofunctioning nodules malignancy is more predicted if by US the nodule was mixed or solid [isoechoic or hypoechoic]. Thus the combination of RIS and US in solitary cold nodule and absent RIS can lead to a very high accuracy in the preoperative diagnosis of thyroid pathology and making surgery unnecessary in many cases and improving the cost benefit ratio