ABSTRACT
Objective: To determine the diagnostic accuracy of Diffusion-Weighted Imaging [DWI] and Apparent Diffusion Coefficient [ADC] mapping in differentiating benign from malignant thyroid nodules by taking histopathology as the gold standard
Study Design: A cross-sectional analytical study
Place and Duration of Study: Department of Radiology at Combined Military Hospital [CMH], Lahore, from August 2012 to July 2013
Methodology: Thirty-five patients, who were referred to radiology department of CMH, Lahore, for ultrasound or Fine Needle Aspiration Cytology [FNAC] of thyroid gland, fulfilling the inclusion and exclusion criteria, were included in the study. They were evaluated on 1.5 Tesla MRI machine with T1- and T2-weighted imaging as well as fat suppressed technique. DWI was done using b-values of 0 and 1000 s/mm[2] and ADC values were calculated for the thyroid nodules. All of these patients were subjected to ultrasound guided core biopsy and histopathology results were correlated with ADC values
Results: The benign nodules showed facilitated diffusion while malignant nodules showed restricted diffusion. T-test was used to assess the difference in mean ADC values between benign and malignant nodules. The mean ADC value of the malignant thyroid nodules [0.94 +/- 0.16 x 10[-3] mm[2]/s] was significantly lower than that of the benign thyroid nodules [1.93 +/- 0.13 x 10[-3] mm[2]/s] [p-value < 0.05]. ADC value of 1.6 x 10[-3] mm[2]/s was used as a cut-off, for differentiating benign from malignant thyroid nodules. The sensitivity, specificity, PPV, NPV and diagnostic accuracy of DWI and ADC values in differentiating benign from malignant thyroid nodules were 93%, 95%, 93%, 95% and 92.3%, respectively
Conclusion: DWI is a non-invasive diagnostic tool for characterization and differentiation between benign and malignant thyroid nodules. It not only decreases the burden of unnecessary surgeries when pre-operative FNAC and biopsy are inconclusive, but is also helpful in reaching a definite diagnosis when a nodule is not amendable to biopsy due to any reason