Diffusion-weighted MR imaging of thyroid nodules

Abstract

Introduction

The purpose of our study was to determine the diagnostic role of diffusion-weighted imaging (DWI) in the differentiating of malignant and benign thyroid nodules by using fine needle aspiration biopsy cytology criteria as a reference standard. The apparent diffusion coefficient (ADC) values of the normal-looking thyroid parenchyma were also evaluated both in normal patients and in patients with nodules.

Methods

Between March 2007 and February 2008, 76 consecutive patients with ultrasound-diagnosed thyroid nodules and 20 healthy subjects underwent diffusion-weighted MR imaging by using single-shot spin echo, echo planar imaging. A total of 93 nodules were included in the study using the following b factors 100, 200, and 300 mm²/s. ADC values of thyroid nodules and normal area in all subjects were calculated and compared using suitable statistical analysis.

Results

Mean ADC values for malignant and benign nodules were $0.96 \pm 0.65 \times 10^{ - 3}$ and $3.06 \pm 0.71 \times 10^{ - 3} {{{\text{mm}}^2 } \mathord{\left/ {\vphantom {{{\text{mm}}^2 } {\text{s}}}} \right. \kern-\nulldelimiterspace} {\text{s}}}$ for b-100 factor, $0.56 \pm 0.43 \times 10^{ - 3}$ and $1.80 \pm 0.60 \times 10^{ - 3} {{{\text{mm}}^2 } \mathord{\left/ {\vphantom {{{\text{mm}}^2 } \operatorname{s} }} \right. \kern-\nulldelimiterspace} \operatorname{s} }$ for b-200, and $0.30 \pm 0.20 \times 10^{ - 3}$ and $1.15 \pm 0.43 \times 10^{ - 3} {{{\text{mm}}^2 } \mathord{\left/ {\vphantom {{{\text{mm}}^2 } \operatorname{s} }} \right. \kern-\nulldelimiterspace} \operatorname{s} }$, for b-300, respectively. Mean ADC values of malignant nodules were lower than benign nodules. There were significant differences in ADC values between benign and malignant nodules. ADC values among normal-appearing thyroid parenchyma of patients and normal-appearing thyroid parenchyma of healthy subjects were insignificant at all b factors.

Conclusion

Benign nodules have higher ADC values than malignant ones. DWI may be helpful in differentiating malign and benign thyroid nodules.