Role of Diffusion-Weighted Magnetic Resonance Imaging in Differentiating Benign From Malignant Thyroid Lesions: A Prospective Study

Abstract

Introduction: Accurate non-invasive imaging technique for characterising thyroid nodules has always been problematic. Diffusion-Weighted Magnetic Resonance Imaging (DW-MRI) is a functional MR imaging modality that quantifies the net diffusion of water molecules in any lesion. Thyroid carcinoma due to its increased cellularity shows diffusion restriction on DWI with low Apparent Diffusion Coefficient (ADC) values that can be used to differentiate benign and malignant thyroid nodules. Aim: To evaluate role of DW-MRI in differentiating benign from malignant thyroid disease and to calculate ADC values of thyroid lesion/nodule on DW-MRI and correlate with FNAC/histopathology findings. Materials and Methods: A prospective study was conducted in department of Radiodiagnosis, Maharishi Markandeshwar Institute of Medical Sciences and Research, Mullana, Ambala. Total of fifty patients with neck swelling diagnosed clinically and confirmed on ultrasound were included. The patients underwent routine as well diffusion weighted MRI using b-values of 0,400 and 800 mm2/sec. Their ADC values were calculated and were finally correlated with histopathological findings. Statistical analysis was done using SPSS v.21 and a p-value of <0.05 was considered as significant. Results: The mean age of the patients was 41.8±13.9 years with maximum number of patients in the age group of 31 to 40 years. The mean ADC value of benign thyroid nodules (1.721×10-3mm2/sec) was significantly higher than that of malignant thyroid nodules (1.075×10-3mm2/sec) (p=0.01). The best cut-off value for distinguishing benign and malignant nodules was 1.371×10-3mm2/sec with sensitivity, specificity, PPV an NPV of 93.75%, 91.17%, 83.33% and 96.87%, respectively. The accuracy of the study in differentiating benign from malignant thyroid lesions was 92%. Conclusion: DW-MRI due to its ability to probe the microstructure of the tumour, its short acquisition time, its high repeatability and safety is a new promising non-invasive imaging modality that can reliably differentiate between benign and malignant thyroid nodules and can help avoid unnecessary biopsies and consequently its hazards.