Abstract
PurposeUltrasound‐guided fine needle aspirate cytology fails to diagnose many malignant thyroid nodules; consequently, patients may undergo diagnostic lobectomy. This study assessed whether textural analysis (TA) could noninvasively stratify thyroid nodules accurately using diffusion‐weighted MRI (DW‐MRI).MethodsThis multi‐institutional study examined 3T DW‐MRI images obtained with spin echo echo planar imaging sequences. The training data set included 26 patients from Cambridge, United Kingdom, and the test data set included 18 thyroid cancer patients from Memorial Sloan Kettering Cancer Center (New York, New York, USA). Apparent diffusion coefficients (ADCs) were compared over regions of interest (ROIs) defined on thyroid nodules. TA, linear discriminant analysis (LDA), and feature reduction were performed using the 21 MaZda‐generated texture parameters that best distinguished benign and malignant ROIs.ResultsTraining data set mean ADC values were significantly different for benign and malignant nodules (P = 0.02) with a sensitivity and specificity of 70% and 63%, respectively, and a receiver operator characteristic (ROC) area under the curve (AUC) of 0.73. The LDA model of the top 21 textural features correctly classified 89/94 DW‐MRI ROIs with 92% sensitivity, 96% specificity, and an AUC of 0.97. This algorithm correctly classified 16/18 (89%) patients in the independently obtained test set of thyroid DW‐MRI scans.ConclusionTA classifies thyroid nodules with high sensitivity and specificity on multi‐institutional DW‐MRI data sets. This method requires further validation in a larger prospective study. Magn Reson Med, 2015. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Magn Reson Med 75:1708–1716, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance.
Highlights
Thyroid cancer is the most common malignant endocrine tumor, with an annual incidence in the United States of 12.2 per 100,000 in men and women per year [1]
Each regions of interest (ROIs) was originally delineated by an experienced neuroradiologist using the FuncTool software (GE Healthcare) and subsequently carefully traced using ImageJ software onto the original resolution apparent diffusion coefficient (ADC) maps so that binary masks of these ROIs could be imported into MaZda to preserve the original ROI locations
The difference between the means of the benign and malignant nodules was significant (P 1⁄4 0.02); there was overlap between the confidence intervals (CIs), resulting in an area under the curve (AUC) of 0.73, sensitivity of 70%, and specificity of 63% on receiver operator characteristic (ROC) analysis using a cutoff ADC value of 2.16 Â 10À3 mm2/s
Summary
Thyroid cancer is the most common malignant endocrine tumor, with an annual incidence in the United States of 12.2 per 100,000 in men and women per year [1]. Thyroid nodules may have benign or malignant pathology and are diagnosed before surgery using ultrasound-guided fine needle aspirate cytology (FNAC), the current gold standard. Thyroid nodules are common and ultrasound is an excellent screening tool to determine which nodules require FNAC. Up to 7% of nodules yield nondiagnostic cytology, classified as Thy1 [2]. A further 15%–30% of FNACs represent an indeterminate cytology (Thy3), where a follicular or Hurthle cell neoplasm is reported [3]. The risk of malignancy within these Thy and Thy indeterminate nodules is 20%–30% [4].
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