Anatomy-Guided Multi-Path CycleGAN for Lung CT Kernel Harmonization

Abstract

Accurate quantitative measurement in lung computed tomography (CT) imaging often relies on consistent kernel reconstruction across scanners and manufacturers. Harmonization can reduce measurement variability caused by heterogeneous reconstruction kernels; however, harmonization across different manufacturers and scanners remains challenging due to significant differences in reconstruction protocol and positional alignment of subjects, often resulting in anatomical hallucinations. To address this, we propose a multi-path cycleGAN framework that incorporates multi-region anatomical labels and a tissue statistic loss as anatomical regularization to preserve structural integrity during harmonization. We trained our model on 100 scans each of four representative reconstruction kernels from the National Lung Screening Trial (NLST) dataset and evaluated it on 240 withheld scans. Experimental results demonstrate superior performance of our method in both within manufacturer harmonization and cross-manufacture harmonization: Harmonizing hard-to-soft kernel images within a single manufacturer significantly reduces emphysema measurement discrepancies (p < 0.05). Across manufacturers, harmonizing all kernels to a reference soft kernel yields consistent emphysema quantification (p > 0.05) and preserves anatomical structures, as demonstrated by improved Dice similarity coefficient in skeletal muscle and subcutaneous adipose tissue between harmonized and unharmonized images. These findings demonstrate that segmentation-driven anatomical regularization effectively addresses cross-manufacturer discrepancies, ensuring robust quantitative imaging. We release our code and model at https://github.com/MASILab/AnatomyconstrainedMultipathGAN.