Jun Young Park

Modeling heterogeneous covariance patterns in high-dimensional brain imaging data

Research description:

An important lesson from the first undergraduate statistics course is that the increased sample size leads to a higher power. In brain imaging studies, it is common to combine data collected from multiple study sites to recruit more subjects and increase the reproducibility of scientific discoveries. However, each study site uses MRI scanners from different manufacturers and its own processing protocols, which results in data being corrupted by *unwanted* scanner effects (also termed batch effects). For high-quality data, it is necessary to remove these unwanted scanner effects but, at the same time, preserve biological patterns. The student will develop a data science methodology that removes explicit scanner effects from high-dimensional brain imaging data. A particular application of interest is the cortical thickness data obtained from structural magnetic resonance imaging (MRI). Cortical thickness data reveals an explicit spatial autocorrelation structure, and we hypothesize that the significant source of the scanner effect is heterogeneous spatial autocorrelations by scanners. The student will first conduct exploratory data analysis to visualize and quantify these effects. We will then develop a batch correction method and compare its performance to existing methods using simulation studies. A report summarizing the work is expected by the end of the summer.

Year: 2022

Researcher:
Jun Young Park, Statistical Sciences, Faculty of Arts & Science, University of Toronto

Student: 
Linxi Chen, University of Toronto

Through SUDS, undergraduate students engage in hands-on research focused on data sciences and AI methodology applications.

Statistical learning for censored data

Research description:

Understanding censoring, which occurs when the event of interest is not observed for some individuals within the study period, is critical for modeling time-to-event data. This is particularly important for applications such as risk prediction in cancer studies, electronic health records, and clinical trials. Ignoring censoring can lead to biased and inaccurate predictive performance. While numerous statistical approaches in survival analysis, such as Cox regression, have been developed to handle censoring, it remains an open challenge to effectively integrate these methods with modern statistical learning techniques for classification. This SUDS project aims to extend the use of Inverse Probability of Censoring Weighting (IPCW) in conjunction with statistical learning to improve risk prediction for right-censored data. Although IPCW has shown promise when integrated with statistical learning methods (e.g., Vock et al., 2016), its predictive performance can suffer when a significant proportion of subjects are censored before the time of interest due to a huge reduction in effective sample sizes. This project will explore new methodological advancements to address these limitations and validate these approaches through simulation studies and real-world applications in cancer genomics. Students working on this SUDS project will meet weekly with the supervisor to discuss progress and address challenges.

Year: 2025

Researcher:
Jun Young Park, Department of Statistical Sciences, Faculty of Arts and Science, University of Toronto

Student: 
Liyan Wang, University of Toronto

Through SUDS, undergraduate students engage in hands-on research focused on data sciences and AI methodology applications.