A 3D-CNN model with CT-based parametric response mapping for classifying COPD subjects

Sci Rep. 2021 Jan 8;11(1):34. doi: 10.1038/s41598-020-79336-5.

Abstract

Chronic obstructive pulmonary disease (COPD) is a respiratory disorder involving abnormalities of lung parenchymal morphology with different severities. COPD is assessed by pulmonary-function tests and computed tomography-based approaches. We introduce a new classification method for COPD grouping based on deep learning and a parametric-response mapping (PRM) method. We extracted parenchymal functional variables of functional small airway disease percentage (fSAD%) and emphysema percentage (Emph%) with an image registration technique, being provided as input parameters of 3D convolutional neural network (CNN). The integrated 3D-CNN and PRM (3D-cPRM) achieved a classification accuracy of 89.3% and a sensitivity of 88.3% in five-fold cross-validation. The prediction accuracy of the proposed 3D-cPRM exceeded those of the 2D model and traditional 3D CNNs with the same neural network, and was comparable to that of 2D pretrained PRM models. We then applied a gradient-weighted class activation mapping (Grad-CAM) that highlights the key features in the CNN learning process. Most of the class-discriminative regions appeared in the upper and middle lobes of the lung, consistent with the regions of elevated fSAD% and Emph% in COPD subjects. The 3D-cPRM successfully represented the parenchymal abnormalities in COPD and matched the CT-based diagnosis of COPD.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Case-Control Studies
  • Deep Learning
  • Female
  • Humans
  • Imaging, Three-Dimensional / methods
  • Lung / diagnostic imaging
  • Male
  • Middle Aged
  • Neural Networks, Computer
  • Pulmonary Disease, Chronic Obstructive / classification*
  • Pulmonary Disease, Chronic Obstructive / diagnostic imaging
  • Respiratory Function Tests
  • Tomography, X-Ray Computed / methods