An organ deformation model using Bayesian inference to combine population and patient-specific data

TL;DR

This paper introduces Bayesian deformation models that effectively combine population and patient-specific data to predict organ motion with fewer scans, enhancing radiotherapy planning accuracy.

Contribution

The study develops and evaluates Bayesian models that outperform existing methods by integrating population and individual data for organ deformation prediction.

Findings

Bayesian models show higher spatial correlation with ground truth.

Fewer scans are needed for accurate predictions.

Models are applicable to radiotherapy planning.

Abstract

Objective: Organ deformation models have the potential to improve delivery and reduce toxicity of radiotherapy, but existing data-driven motion models are based on either patient-specific or population data. We propose to combine population and patient-specific data using a Bayesian framework. Our goal is to accurately predict individual motion patterns while using fewer scans than previous models. Approach: We have derived and evaluated two Bayesian deformation models. The models were applied retrospectively to the rectal wall from a cohort of prostate cancer patients. These patients had repeat CT scans evenly acquired throughout radiotherapy. Each model was used to create coverage probability matrices (CPMs). The spatial correlations between these CPMs and ``true'' CPMs, derived from independent scans of the same patient, were calculated. Main results: Spatial correlation with ground truth were significantly higher for the Bayesian deformation models than both patient-specific and population-derived models with 1, 2 or 3 patient-specific scans as input. Statistical motion simulations indicate that this result will also hold for more than 3 scans. Significance: The improvement over known models means that fewer scans per patient are needed to achieve accurate deformation predictions. The models have applications in robust radiotherapy planning and evaluation, among others.