[A frequency-adaptive implicit neural representation method for medical image compression]

To address the limitations of data storage and transfer caused by exponential growth of medical imaging data size, we propose a frequency-adaptive implicit neural compression (FAINC) method for medical images based on optimized implicit neural networks (INRs).

A retrospective analysis was conducted on abdominal CT data from 356 patients in the KiTS19 and AVT datasets. We developed the FAINC method, a multi-subnetwork collaborative compression framework, which first evaluates the frequency-domain complexity of image blocks using the Spectral Sparsity Index (SSI), and then dynamically allocates them to subnetworks of different capacities through a frequency-domain gating mechanism. Compression output is achieved by combining parameter quantization with entropy coding. To assess its performance, the proposed method was compared with mainstream commercial compression standards (H.265/HEVC and JPEG2000), the implicit neural representation method NeRV, and the deep-learning-based compression method DVC.

The FAINC method achieved the best reconstruction performance on both KiTS19 and AVT datasets at high compression ratios. At bitrates of BPV=0.32 and BPV=0.34, the FAINC method obtained the highest PSNR (47.03 and 50.76), the highest SSIM (0.9853 and 0.9930), and the lowest RMSE (0.0045 and 0.0029), achieving also a significantly higher subjective image quality score than other methods. Ablation studies demonstrated that the frequency-domain gating mechanism and dynamic parameter allocation contributed approximately 2.05 dB and 1.87 dB PSNR improvements, respectively.

The proposed method substantially enhances image reconstruction quality at high compression ratios and outperforms the existing mainstream approaches in terms of structural fidelity and compression efficiency. The FAINC method provides a promising technical solution for efficient storage and low-bandwidth remote transfer of medical image data.