Published Online:https://doi.org/10.1148/radiol.2018181352

Convolutional neural networks were superior to radiomic analysis for classification of enhancing lesions. Although both approaches were inferior to radiologists’ performance, convolutional neural networks have the potential for further improvement with more training data whereas radiomic analysis does not.

Purpose

To compare the diagnostic performance of radiomic analysis (RA) and a convolutional neural network (CNN) to radiologists for classification of contrast agent–enhancing lesions as benign or malignant at multiparametric breast MRI.

Materials and Methods

Between August 2011 and August 2015, 447 patients with 1294 enhancing lesions (787 malignant, 507 benign; median size, 15 mm ± 20) were evaluated. Lesions were manually segmented by one breast radiologist. RA was performed by using L1 regularization and principal component analysis. CNN used a deep residual neural network with 34 layers. All algorithms were also retrained on half the number of lesions (n = 647). Machine interpretations were compared with prospective interpretations by three breast radiologists. Standard of reference was histologic analysis or follow-up. Areas under the receiver operating curve (AUCs) were used to compare diagnostic performance.

Results

CNN trained on the full cohort was superior to training on the half-size cohort (AUC, 0.88 vs 0.83, respectively; P = .01), but there was no difference for RA and L1 regularization (AUC, 0.81 vs 0.80, respectively; P = .76) or RA and principal component analysis (AUC, 0.78 vs 0.78, respectively; P = .93). By using the full cohort, CNN performance (AUC, 0.88; 95% confidence interval: 0.86, 0.89) was better than RA and L1 regularization (AUC, 0.81; 95% confidence interval: 0.79, 0.83; P < .001) and RA and principal component analysis (AUC, 0.78; 95% confidence interval: 0.76, 0.80; P < .001). However, CNN was inferior to breast radiologist interpretation (AUC, 0.98; 95% confidence interval: 0.96, 0.99; P < .001).

Conclusion

A convolutional neural network was superior to radiomic analysis for classification of enhancing lesions as benign or malignant at multiparametric breast MRI. Both approaches were inferior to radiologists’ performance; however, more training data will further improve performance of convolutional neural network, but not that of radiomics algorithms.

© RSNA, 2018

Online supplemental material is available for this article.

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Article History

Received: June 9 2018
Revision requested: July 26 2018
Revision received: Sept 25 2018
Accepted: Sept 26 2018
Published online: Nov 13 2018
Published in print: Feb 2019