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

Abstract 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 mm 2 /s. The mean ADC values of solitary thyroid nodules were measured for b values of 500 and 1000 s/mm 2 . Results The ADC value of benign solitary thyroid nodules ranged from 1.56 to 2.28 × 10 −3  mm 2 /s (b = 1000 s/mm 2 ) and from 1.64 to 2.70 × 10 −3  mm 2 /s (b = 500 s/mm 2 ). The ADC value of malignant solitary thyroid nodules ranged from 0.54 to 1.47 × 10 −3  mm 2 /s (b = 1000 s/mm 2 ) and from 0.61 to 1.56 × 10 −3  mm 2 /s (b = 500 s/mm 2 ). 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  mm 2 /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.