  Glioma constitutes 80% of malignant primary brain tumors and is usually
classified as HGG and LGG. The LGG tumors are less aggressive, with slower
growth rate as compared to HGG, and are responsive to therapy. Tumor biopsy
being challenging for brain tumor patients, noninvasive imaging techniques like
Magnetic Resonance Imaging (MRI) have been extensively employed in diagnosing
brain tumors. Therefore automated systems for the detection and prediction of
the grade of tumors based on MRI data becomes necessary for assisting doctors
in the framework of augmented intelligence. In this paper, we thoroughly
investigate the power of Deep ConvNets for classification of brain tumors using
multi-sequence MR images. We propose novel ConvNet models, which are trained
from scratch, on MRI patches, slices, and multi-planar volumetric slices. The
suitability of transfer learning for the task is next studied by applying two
existing ConvNets models (VGGNet and ResNet) trained on ImageNet dataset,
through fine-tuning of the last few layers. LOPO testing, and testing on the
holdout dataset are used to evaluate the performance of the ConvNets. Results
demonstrate that the proposed ConvNets achieve better accuracy in all cases
where the model is trained on the multi-planar volumetric dataset. Unlike
conventional models, it obtains a testing accuracy of 95% for the low/high
grade glioma classification problem. A score of 97% is generated for
classification of LGG with/without 1p/19q codeletion, without any additional
effort towards extraction and selection of features. We study the properties of
self-learned kernels/ filters in different layers, through visualization of the
intermediate layer outputs. We also compare the results with that of
state-of-the-art methods, demonstrating a maximum improvement of 7% on the
grading performance of ConvNets and 9% on the prediction of 1p/19q codeletion
status.
