title: Multiclass imbalance learning: Improving classification of pediatric brain tumors from magnetic resonance spectroscopy.
abstract: Classification of pediatric brain tumors from1H-magnetic resonance spectroscopy (MRS) can aid diagnosis and management of brain tumors. However, varied incidence of the different tumor types leads to imbalanced class sizes and introduces difficulties in classifying rare tumor groups. This study assessed different imbalanced multiclass learning techniques and compared the use of complete spectra and quantified metabolite profiles for classification of three main childhood brain tumor types.
  
  
  
  Single-voxel, Short echo time MRS data were collected from 90 patients with pilocytic astrocytoma (n = 42), medulloblastoma (n = 38), or ependymoma (n = 10). Both spectra and metabolite profiles were used to develop the learning algorithms. The borderline synthetic minority oversampling technique and AdaboostM1 were used to correct for the skewed distribution. Classifiers were trained using five different pattern recognition algorithms.
  
  
  
  Use of imbalanced learning techniques improved the balanced accuracy rate (BAR) of all classification methods (average BAR over all classification methods for spectra: oversampled data = 0.81, original = 0.63, P < 0.001; metabolite concentration: oversampled-data = 0.91, original = 0.75, P < 0.0001). Performance of all classifiers in discriminating ependymomas increased when oversampled data were used compared with original data for both complete spectra (F-measure P < 0.01) and metabolite profile (F-measure P < 0.001).
  
  
  
  Imbalanced learning techniques improve the classification accuracy of childhood brain tumors from MRS where group sizes differ and facilitate the inclusion of rarer tumor types into clinical decision support systems. Magn Reson Med 77:2114-2124, 2017. © 2016 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.
authors.affiliation: Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom.|Birmingham Children's Hospital NHS Foundation Trust, Birmingham, United Kingdom.
authors.forename: Niloufar
authors.initials: N
authors.lastname: Zarinabad
authors.affiliation: School of Psychology and Birmingham University Imaging Centre, University of Birmingham, Edgbaston, Birmingham United Kingdom.
authors.forename: Martin
authors.initials: M
authors.lastname: Wilson
authors.affiliation: Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom.|Birmingham Children's Hospital NHS Foundation Trust, Birmingham, United Kingdom.
authors.forename: Simrandip K
authors.initials: SK
authors.lastname: Gill
authors.affiliation: Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom.|Birmingham Children's Hospital NHS Foundation Trust, Birmingham, United Kingdom.
authors.forename: Karen A
authors.initials: KA
authors.lastname: Manias
authors.affiliation: Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom.|Department of Medical Physics, University Hospitals Birmingham NHS Foundation Trust, Birmingham, United Kingdom.
authors.forename: Nigel P
authors.initials: NP
authors.lastname: Davies
authors.affiliation: Institute of Cancer and Genomic Sciences, University of Birmingham, Birmingham, United Kingdom.|Birmingham Children's Hospital NHS Foundation Trust, Birmingham, United Kingdom.
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Peet
mesh_terms: D000465:Algorithms; D014408:Biomarkers, Tumor / Q000378:metabolism*; D001932:Brain Neoplasms / Q000175:diagnosis* / Q000378:metabolism*; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D005260:Female; D006801:Humans; D000069550:Machine Learning; D008297:Male; D008875:Middle Aged; D010363:Pattern Recognition, Automated / Q000379:methods; D066244:Proton Magnetic Resonance Spectroscopy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D014408:Biomarkers, Tumor
keywords: MR spectroscopy; brain tumors; classification; diagnosis; imbalanced learning