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Performance Comparison of Individual and Ensemble CNN Models for the Classification of Brain 18F-FDG-PET Scans

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Abstract

The high-background glucose metabolism of normal gray matter on [18F]-fluoro-2-D-deoxyglucose (FDG) positron emission tomography (PET) of the brain results in a low signal-to-background ratio, potentially increasing the possibility of missing important findings in patients with intracranial malignancies. To explore the strategy of using a deep learning classifier to aid in distinguishing normal versus abnormal findings on PET brain images, this study evaluated the performance of a two-dimensional convolutional neural network (2D-CNN) to classify FDG PET brain scans as normal (N) or abnormal (A). Methods: Two hundred eighty-nine brain FDG-PET scans (N; n = 150, A; n = 139) resulting in a total of 68,260 images were included. Nine individual 2D-CNN models with three different window settings for axial, coronal, and sagittal axes were trained and validated. The performance of these individual and ensemble models was evaluated and compared using a test dataset. Odds ratio, Akaike’s information criterion (AIC), and area under curve (AUC) on receiver-operative-characteristic curve, accuracy, and standard deviation (SD) were calculated. Results: An optimal window setting to classify normal and abnormal scans was different for each axis of the individual models. An ensembled model using different axes with an optimized window setting (window-triad) showed better performance than ensembled models using the same axis and different windows settings (axis-triad). Increase in odds ratio and decrease in SD were observed in both axis-triad and window-triad models compared with individual models, whereas improvements of AUC and AIC were seen in window-triad models. An overall model averaging the probabilities of all individual models showed the best accuracy of 82.0%. Conclusions: Data ensemble using different window settings and axes was effective to improve 2D-CNN performance parameters for the classification of brain FDG-PET scans. If prospectively validated with a larger cohort of patients, similar models could provide decision support in a clinical setting.

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Abbreviations

FDG:

[18F]-fluoro-2-D-deoxyglucose

2D-CNN:

two dimensional convolutional neural network

AIC:

Akaike’s information criterion

AUC:

area under curve

CSV:

comma separated value file

CT:

computed tomography

MR:

magnetic resonance

PET:

positron emission tomography

PNG:

Portable Network Graphics format

ROC:

receiver operating characteristic

SD:

standard deviation

SUV:

standardized uptake value.

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Authors and Affiliations

  1. Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Stanford University, 300 Pasteur Drive, Office H2228, Stanford, CA, 94305, USA

    Tomomi Nobashi, Valentina Ferri, Mary Ellen Koran, Benjamin L. Franc, Andrei Iagaru & Guido A. Davidzon

  2. Clinic for Nuclear Medicine, University Hospital Essen, Essen, Germany

    Claudia Zacharias

  3. DimensionalMechanics Inc.®, 2821 Northup Way Suite, Bellevue, WA, #200, USA

    Jason K. Ellis

Authors
  1. Tomomi Nobashi
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  2. Claudia Zacharias
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  3. Jason K. Ellis
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  4. Valentina Ferri
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  5. Mary Ellen Koran
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  6. Benjamin L. Franc
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  7. Andrei Iagaru
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  8. Guido A. Davidzon
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Corresponding author

Correspondence to Guido A. Davidzon.

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This retrospective study protocol received approval by the institutional review board and was found to be compliant with the standards of the Health Insurance Portability and Accountability Act.

Conflict of Interest

JKE and CZ are employed and related to DimensionalMechanics Inc.

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Nobashi, T., Zacharias, C., Ellis, J.K. et al. Performance Comparison of Individual and Ensemble CNN Models for the Classification of Brain 18F-FDG-PET Scans. J Digit Imaging 33, 447–455 (2020). https://doi.org/10.1007/s10278-019-00289-x

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