# Identification of Regions of Interest in Neuroimaging Data With Irregular Boundary Based on Semiparametric Transformation Models and Interval‐Censored Outcomes

## TL;DR

This paper introduces a new method to identify brain regions linked to Alzheimer's progression using irregular neuroimaging data and censored time outcomes.

## Contribution

A novel semiparametric model using bivariate splines and an EM algorithm for irregular neuroimaging data with interval-censored outcomes is proposed.

## Key findings

- Bivariate splines over triangulation effectively model irregular brain regions in neuroimages.
- The proposed method identifies regions of interest associated with Alzheimer's progression.
- Simulation studies and real data analysis confirm the method's effectiveness and efficiency.

## Abstract

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that leads to memory loss, cognitive decline, and behavioral changes, without a known cure. Neuroimages are often collected alongside the covariates at baseline to forecast the prognosis of the patients. Identifying regions of interest within the neuroimages associated with disease progression is thus of significant clinical importance. One major complication in such analysis is that the domain of the brain area in neuroimages is irregular. Another complication is that the time to AD is interval‐censored, as the event can only be observed between two revisit time points. To address these complications, we propose to model the imaging predictors via bivariate splines over triangulation and incorporate the imaging predictors in a flexible class of semiparametric transformation models. The regions of interest can then be identified by maximizing a penalized likelihood. A computationally efficient expectation–maximization algorithm is devised for parameter estimation. An extensive simulation study is conducted to evaluate the finite‐sample performance of the proposed method. An illustration with the AD Neuroimaging Initiative dataset is provided.