Diffusion-weighted MRI and apparent diffusion coefficient in differentiation of benign from malignant solitary thyroid nodule

Objective: The aim of this study was to assess the ability of DWI and ADC to differentiate benign from malignant solitary thyroid nodule.Patients and methods: This prospective study was done on 60 patients with solitary thyroid nodule. DW- MRI was performed on all subjects at b values of 0, 500 and 1000 mm2/s. The mean ADC values of solitary thyroid nodules were measured for b values of 500 and 1000 s/mm2.Results: The ADC value of benign solitary thyroid nodules ranged from 1.56 to 2.28 × 10−3 mm2/s (b = 1000 s/mm2) and from 1.64 to 2.70 × 10−3 mm2/s (b = 500 s/mm2). The ADC value of malignant solitary thyroid nodules ranged from 0.54 to 1.47 × 10−3 mm2/s (b = 1000 s/mm2) and from 0.61 to 1.56 × 10−3 mm2/s (b = 500 s/mm2). The mean ADC value for malignant nodules was significantly lower than that for benign nodules (P = 0.000). ADC value of 1.5 × 10−3 mm2/s was used as a cutoff value for differentiation of benign from malignant thyroid nodules.Conclusions: DWI is a powerful tool for the differentiation of benign and malignant nodules and for assessing the functional activity of the thyroid gland, and ADC at b-1000 is more accurate in evaluation of solitary thyroid nodule in comparison with b-500