Multiparametric MR imaging for differentiating between benign and malignant thyroid nodules: Initial experience in 23 patients

Purpose: To evaluate multiparametric MR imaging with combined use of apparent diffusion coefficients (ADCs) and time-signal intensity curves (TICs) for discriminating malignant thyroid nodules from benign ones. Materials and Methods: ADCs and TICs of 7 benign and 16 malignant nodules were retrospectively analyzed on lesion-by-lesion (overall ADCs and TICs) and pixel-bypixel (ADC and TIC mapping) bases. ADCs were determined using b-values of 500 and 1000 s/mm(2). The TICs were classified into 5 patterns on the basis of increment ratio, peak time, and washout ratio. Stepwise approach based on ADC and TIC criteria was used to discriminate between benign and malignant nodules. Results: Overall ADC discriminated undifferentiated carcinomas from papillary carcinomas at 91% accuracy (<= 1.3 x 10(-3) mm(2) /s) and differentiated lymphomas from the other malignant nodules at 100% accuracy <= 0.65 x 10(-3) mm(2) /s). Most malignant thyroid nodules had large (>= 45%) areas of rapid-uptake TIC profile with small (<= 15%) areas of flat TIC profile, or had small (<45%) areas of rapid-uptake TIC profile with large (<= 25%) areas of extremely low or low ADCs (<= 1.2 x 10(-3) mm(2) /s). Stepwise approach discriminated malignant nodules from benign ones at 91% accuracy. Conclusion: The multiparametric MR imaging helps discriminating malignant thyroid nodules from benign ones.