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European Radiology

, Volume 29, Issue 7, pp 3348–3357 | Cite as

Deep learning for liver tumor diagnosis part II: convolutional neural network interpretation using radiologic imaging features

  • Clinton J. Wang
  • Charlie A. Hamm
  • Lynn J. Savic
  • Marc Ferrante
  • Isabel Schobert
  • Todd Schlachter
  • MingDe Lin
  • Jeffrey C. Weinreb
  • James S. Duncan
  • Julius ChapiroEmail author
  • Brian Letzen
Imaging Informatics and Artificial Intelligence

Abstract

Objectives

To develop a proof-of-concept “interpretable” deep learning prototype that justifies aspects of its predictions from a pre-trained hepatic lesion classifier.

Methods

A convolutional neural network (CNN) was engineered and trained to classify six hepatic tumor entities using 494 lesions on multi-phasic MRI, described in Part 1. A subset of each lesion class was labeled with up to four key imaging features per lesion. A post hoc algorithm inferred the presence of these features in a test set of 60 lesions by analyzing activation patterns of the pre-trained CNN model. Feature maps were generated that highlight regions in the original image that correspond to particular features. Additionally, relevance scores were assigned to each identified feature, denoting the relative contribution of a feature to the predicted lesion classification.

Results

The interpretable deep learning system achieved 76.5% positive predictive value and 82.9% sensitivity in identifying the correct radiological features present in each test lesion. The model misclassified 12% of lesions. Incorrect features were found more often in misclassified lesions than correctly identified lesions (60.4% vs. 85.6%). Feature maps were consistent with original image voxels contributing to each imaging feature. Feature relevance scores tended to reflect the most prominent imaging criteria for each class.

Conclusions

This interpretable deep learning system demonstrates proof of principle for illuminating portions of a pre-trained deep neural network’s decision-making, by analyzing inner layers and automatically describing features contributing to predictions.

Key Points

• An interpretable deep learning system prototype can explain aspects of its decision-making by identifying relevant imaging features and showing where these features are found on an image, facilitating clinical translation.

• By providing feedback on the importance of various radiological features in performing differential diagnosis, interpretable deep learning systems have the potential to interface with standardized reporting systems such as LI-RADS, validating ancillary features and improving clinical practicality.

• An interpretable deep learning system could potentially add quantitative data to radiologic reports and serve radiologists with evidence-based decision support.

Keywords

Liver cancer Artificial intelligence Deep learning 

Abbreviations

CNN

Convolutional neural network

CRC

Colorectal carcinoma

DL

Deep learning

FNH

Focal nodular hyperplasia

HCC

Hepatocellular carcinoma

ICC

Intrahepatic cholangiocarcinoma

LI-RADS

Liver Imaging Reporting and Data System

PPV

Positive predictive value

Sn

Sensitivity

Notes

Funding

BL and CW received funding from the Radiological Society of North America (RSNA Research Resident Grant No. RR1731). JD, JC, ML, and CW received funding from the National Institutes of Health (NIH/NCI R01 CA206180).

Compliance with ethical standards

Guarantor

The scientific guarantor of this publication is Julius Chapiro.

Conflict of interest

The authors of this manuscript declare relationships with the following companies: JW: Bracco Diagnostics, Siemens AG; ML: Pro Medicus Limited; JC: Koninklijke Philips, Guerbet SA, Eisai Co.

Statistics and biometry

One of the authors has significant statistical expertise.

Informed consent

Written informed consent was waived by the Institutional Review Board.

Ethical approval

Institutional Review Board approval was obtained.

Methodology

• retrospective

• experimental

• performed at one institution

Supplementary material

330_2019_6214_MOESM1_ESM.pdf (29 kb)
ESM 1 (PDF 28.6 kb)

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Copyright information

© European Society of Radiology 2019

Authors and Affiliations

  • Clinton J. Wang
    • 1
  • Charlie A. Hamm
    • 1
    • 2
  • Lynn J. Savic
    • 1
    • 2
  • Marc Ferrante
    • 1
  • Isabel Schobert
    • 1
    • 2
  • Todd Schlachter
    • 1
  • MingDe Lin
    • 1
  • Jeffrey C. Weinreb
    • 1
  • James S. Duncan
    • 1
    • 3
  • Julius Chapiro
    • 1
    Email author
  • Brian Letzen
    • 1
  1. 1.Department of Radiology and Biomedical ImagingYale School of MedicineNew HavenUSA
  2. 2.Institute of RadiologyCharité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität, and Berlin Institute of HealthBerlinGermany
  3. 3.Department of Biomedical EngineeringYale School of Engineering and Applied ScienceNew HavenUSA

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