Volume 51, Issue 4 pp. 1223-1234
Original Research

Fully automated localization of prostate peripheral zone tumors on apparent diffusion coefficient map MR images using an ensemble learning method

Fatemeh Zabihollahy MASc

Corresponding Author

Fatemeh Zabihollahy MASc

Department of Systems and Computer Engineering, Carleton University, Ottawa, Ontario, Canada

Address reprint requests to: F.Z., Department of Systems and Computer Engineering, Carleton University, 339 Riversedge Crescent, Ottawa, ON, Canada, K1V0Y6. E-mail: [email protected]Search for more papers by this author
Eranga Ukwatta PhD, PEng

Eranga Ukwatta PhD, PEng

School of Engineering, University of Guelph, Guelph, Ontario, Canada

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Satheesh Krishna MD

Satheesh Krishna MD

Department of Medical Imaging, University of Toronto, Toronto, Ontario, Canada

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Nicola Schieda MD

Nicola Schieda MD

Department of Radiology, University of Ottawa, Ottawa, Ontario, Canada

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First published: 28 August 2019
Citations: 13
Contract grant sponsor: Natural Sciences and Engineering Research Council of Canada (NSERC); Ontario Graduate Scholarship (OGS; to F.Z.).

Abstract

Background

Accurate detection and localization of prostate cancer (PCa) in men undergoing prostate MRI is a fundamental step for future targeted prostate biopsies and treatment planning. Fully automated localization of peripheral zone (PZ) PCa using the apparent diffusion coefficient (ADC) map might be clinically useful.

Purpose/Hypothesis

To describe automated localization of PCa in the PZ on ADC map MR images using an ensemble U-Net-based model.

Study Type

Retrospective, case–control.

Population

In all, 226 patients (154 and 72 patients with and without clinically significant PZ PCa, respectively), training, and testing was performed using dataset images of 146 and 80 patients, respectively.

Field Strength

3T, ADC maps.

Sequence

ADC map.

Assessment

The ground truth was established by manual delineation of the prostate and prostate PZ tumors on ADC maps by dedicated radiologists using MRI-radical prostatectomy maps as a reference standard.

Statistical Tests: Performance of the ensemble model was evaluated using Dice similarity coefficient (DSC), sensitivity, and specificity metrics on a per-slice basis. Receiver operating characteristic (ROC) curve and area under the curve (AUC) were employed as well. The paired t-test was used to test the differences between the performances of constituent networks of the ensemble model.

Results

Our developed algorithm yielded DSC, sensitivity, and specificity of 86.72% ± 9.93%, 85.76% ± 23.33%, and 76.44% ± 23.70%, respectively (mean ± standard deviation) on 80 test cases consisting of 41 and 39 instances from patients with and without clinically significant tumors including 660 extracted 2D slices. AUC was reported as 0.779.

Data Conclusion

An ensemble U-Net-based approach can accurately detect and segment PCa in the PZ from ADC map MR prostate images.

Level of Evidence: 4

Technical Efficacy: Stage 1

J. Magn. Reson. Imaging 2020;51:1223–1234.

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