MAPS: A Comprehensive Feature Model for Prostate Cancer Diagnosis With Multiparametric MRI

Abstract

Prostate cancer killed over 33000 North American men in 2013. However, the survival outlook for prostate cancer is very good if it is caught early. Prostate cancer screening is therefore very important. Although many methods are currently used to screen for prostate cancer, the use of multiparametric magnetic resonance imaging (mpMRI) is increasing in clinical practice and has been shown to have some power in differentiating between healthy and cancerous tissue. This thesis presents a comprehensive feature model for performing prostate cancer diagnosis using mpMRI. It incorporates a novel tumour candidate identification algorithm to efficiently and thoroughly identify regions of concern and a feature model to grade these regions for severity. Unlike conventional automated classification schemes, this feature model aims to ground its decisions in a way that can be interpreted and understood by the diagnostician. It does this by grouping features into high-level feature categories which are already used by radiologists to diagnose prostate cancer: Morphology, Asymmetry, Physiology, and Size (MAPS), using biomarkers inspired by the PI-RADS guidelines for performing structured reporting on prostate MRI. To the author's best knowledge, the proposed feature model is the first using morphology and asymmetry features for prostate cancer detection.

Clinical mpMRI data were collected from thirteen men with biopsy-confirmed prostate cancer and labeled by an expert radiologist with thirteen years of experience diagnosing prostate MRI. These annotated data were used to train classifiers using the proposed feature model in order to evaluate classification performance. Training was performed using cross-validation in order to avoid overlearning the training set. Experimental results indicated that the proposed model outperformed each of its constituent feature groups as well as a comparable state of the art feature model.

Further work on the MAPS feature model is still warranted. Although the initial results are promising, more data are needed to refine the feature model and discard those features with no predictive power. Additional features should be investigated for inclusion in the model, so that the existing features may be conditioned on the prostate region to reflect the different characteristics between, for instance, the peripheral and the transition zones. Finally, user experience and user acceptance studies would help investigate the degree of cognitive support to diagnosticians that the MAPS model provides.