Role of Dynamic Magnetic Resonance Imaging in differentiating benign from malignant thyroid nodule

Abstract

Thyroid nodules are a common clinical problem, nodular thyroid is commonly detected on palpation in 4%–7% of the population, on sonographic examination in 10%–40%, and by pathologic examination at autopsy in 50%. In contrast, compared with the high prevalence of nodular thyroid disease, thyroid cancer is rare, however, it is prudent to differentiate the benign from malignant ones in order to decrease the risk of unnecessary surgery for the benign thyroid nodules. Despite great improvement in diagnostic techniques such as thyroid scan and CT scan of neck, there is still a large problem to use a non- invasive and reliable technique to differentiate benign from malignant thyroid nodules. Recent developments in MRI techniques may be of diagnostic value. Diffusion-weighted MR imaging (DWI) is an emerging technique sensitive to changes in the microstructural organization of tissue that may affect water diffusion. It has been used to evaluate head and neck tumours, Apparent Diffusion Coefficient (ADC) value is a quantitative parameter for distinguishing malignant tumours from benign thyroid nodules. Diffusion-weighted imaging (DWI) is functional MRI that is based on the diffusion of water molecules through the tissue of interest. DWI can provide crucial information regarding the molecular profile of the underlying pathology and pathophysiological mechanisms. Specifically, the diffusion of water molecules in malignant tumors is restricted, which results in a decreased apparent diffusion coefficient (ADC); this difference in the ADC facilitates the differentiation of benign tumours from malignant tumours. Generally, malignant tumours have enlarged nuclei and show hypercellularity. These histopathologic characteristics reduce the extracellular matrix and the diffusion space of water protons in the extracellular areas, with a resultant decrease in the ADC value. The objective of this study is to evaluate the role of diffusion weighted imaging (DWI) and apparent diffusion coefficient (ADC) to differentiate benign from malignant thyroid nodules This cross-sectional study was conducted at the endocrinology outpatient clinic at Ain-Shams university hospitals included 34 patients who were determined to have thyroid nodules by clinical examination and ultrasonography. All patients were subjected to history taking, general and local clinical examination, laboratory investigation, neck ultrasound, MRI and FNAB.