Significance: Prostate cancer is the most common cancer among men. An accurate diagnosis of its severity at detection plays a major role in improving their survival. Recently, machine learning models using biomarkers identified from Raman micro-spectroscopy discriminated intraductal carcinoma of the prostate (IDC-P) from cancer tissue with a ≥85 % detection accuracy and differentiated high-grade prostatic intraepithelial neoplasia (HGPIN) from IDC-P with a ≥97.8 % accuracy.
Aim: To improve the classification performance of machine learning models identifying different types of prostate cancer tissue using a new dimensional reduction technique.
Approach: A radial basis function (RBF) kernel support vector machine (SVM) model was trained on Raman spectra of prostate tissue from a 272-patient cohort (Centre hospitalier de l’Université de Montréal, CHUM) and tested on two independent cohorts of 76 patients [University Health Network (UHN)] and 135 patients (Centre hospitalier universitaire de Québec-Université Laval, CHUQc-UL). Two types of engineered features were used. Individual intensity features, i.e., Raman signal intensity measured at particular wavelengths and novel Raman spectra fitted peak features consisting of peak heights and widths.
Results: Combining engineered features improved classification performance for the three aforementioned classification tasks. The improvements for IDC-P/cancer classification for the UHN and CHUQc-UL testing sets in accuracy, sensitivity, specificity, and area under the curve (AUC) are (numbers in parenthesis are associated with the CHUQc-UL testing set): +4 % (+8 % ), +7 % (+9 % ), +2 % (6%), +9 (+9) with respect to the current best models. Discrimination between HGPIN and IDC-P was also improved in both testing cohorts: +2.2 % (+1.7 % ), +4.5 % (+3.6 % ), +0 % (+0 % ), +2.3 (+0). While no global improvements were obtained for the normal versus cancer classification task [+0 % (−2 % ), +0 % (−3 % ), +2 % (−2 % ), +4 (+3)], the AUC was improved in both testing sets.
Conclusions: Combining individual intensity features and novel Raman fitted peak features, improved the classification performance on two independent and multicenter testing sets in comparison to using only individual intensity features.
Prostate cancer is the most diagnosed form of cancer among American men and, in vast proportion, the standard of care treatment includes radical prostatectomy. Important risk factors associated with prostatectomies are the presence of post-surgery residual prostate tissue and positive cancer margins, potentially leading to recurrences. Prostate histopathology analysis following the procedure is used to determine follow-up treatment. However, only a limited fraction of the prostate margins can be sampled, which can lead to suboptimal evaluation and treatment. Here we present the development of a wide-field multimodal imaging system designed to quantify intrinsic tissue fluorescence and map scattering and absorption coefficients using spatial frequency domain imaging (SFDI). The system allows targeting of suspicious prostate regions to guide histopathology analysis, aiming to improve diagnostic accuracy and treatment planning. Tissue excitation for endogenous fluorescence is achieved with a 405 nm laser diode and, for SFDI, a digital light projector transmits structured white light used to reconstruct tissue optical properties (absorption, scattering) between 420 and 720 nm. A light transport model-based quantification algorithm then corrects the fluorescence spectra for tissue attenuation, lending a biomarker that correlates with local fluorophore concentrations. Spectral and spatial calibration of both modalities was done on optical phantoms and validation of the fluorescence quantification on biological tissue. Finally, imaging results are presented for 5 human prostates interrogated with the system, along with spatially-registered histopathology analyses. Future work involves massive data acquisition and development of artificial intelligence models for tissue classification (prostate, non-prostate; healthy, cancerous) and adaptation for intraoperative use.
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