Computer-Aided Cobb Measurement Based on Automatic Detection of Vertebral Slopes Using Deep Neural Network.

Junhua Zhang,Hongjian Li,Yufeng Zhang,Liang Lv

doi:10.1155/2017/9083916

Abstract

Objective To develop a computer-aided method that reduces the variability of Cobb angle measurement for scoliosis assessment. Methods A deep neural network (DNN) was trained with vertebral patches extracted from spinal model radiographs. The Cobb angle of the spinal curve was calculated automatically from the vertebral slopes predicted by the DNN. Sixty-five in vivo radiographs and 40 model radiographs were analyzed. An experienced surgeon performed manual measurements on the aforementioned radiographs. Two examiners used both the proposed and the manual measurement methods to analyze the aforementioned radiographs. Results For model radiographs, the intraclass correlation coefficients were greater than 0.98, and the mean absolute differences were less than 3°. This indicates that the proposed system showed high repeatability for measurements of model radiographs. For the in vivo radiographs, the reliabilities were lower than those from the model radiographs, and the differences between the computer-aided measurement and the manual measurement by the surgeon were higher than 5°. Conclusion The variability of Cobb angle measurements can be reduced if the DNN system is trained with enough vertebral patches. Training data of in vivo radiographs must be included to improve the performance of DNN. Significance Vertebral slopes can be predicted by DNN. The computer-aided system can be used to perform automatic measurements of Cobb angle, which is used to make reliable and objective assessments of scoliosis.

Highlights

Scoliosis is a spinal deformity in which the spine shows a lateral curvature in the frontal plane [1]
We proposed a computer-aided Cobb angle measurement method that automatically determined the slopes of vertebrae by using a deep neural network (DNN)
We used a spine model to generate the training set. This model included 12 thoracic vertebrae and five lumbar vertebrae. This model was made in a high-resolution imaging medium (Sawbones, Vashon, WA, USA) that could be used to produce a realistic image in radiographic environments as real bones

Summary

Introduction

Scoliosis is a spinal deformity in which the spine shows a lateral curvature in the frontal plane [1]. The Cobb angle method [2] is the gold standard to assess curve severity in posteroanterior (PA) radiographs. To measure the Cobb angle, the most tilted vertebrae (endvertebrae) at the top and bottom of the spinal curve are identified. The Cobb angle can be measured manually by determining the angle between the lines, respectively, drawn along the upper endplate of the superior endvertebra and the lower endplate of the inferior end-vertebra. Manual Cobb angle measurement requires experience and judgment. There could be errors in Cobb angle measurement if the surgeon selects different end-vertebrae and estimates different vertebrae slopes. Even when the same end-vertebrae are selected, Cobb angle measurements may vary by up to 5∘ for the same observer and by 7∘ for different observers [3, 4]

Methods

Results

Conclusion