胎児心拍数信号の自動解析のためのマルチスケール、マルチ基底ウェーブレット投票ネットワーク

Accurate computer-aided interpretation of fetal heart rate (FHR) recordings depends on detecting the baseline and transient accelerations (Acc) and decelerations (Dec) that deviate from it. Most deep learning models treat FHR as a simple 1-D time sequence, overlooking the spectral separation between the low-frequency baseline and high-frequency Acc/Dec patterns. Neglecting this clinically important time-frequency structure can result in missed detections of Acc and Dec events and increased susceptibility to noise. To overcome these limitations, we present WaveFHR-VNet-a U-Net-style, multi-scale, multi-basis wavelet-voting network that analyzes FHR signals in the joint time-frequency domain. WaveFHR-VNet embeds a discrete wavelet transform (DWT) in every encoder block. Each DWT splits the features into approximation (low-pass) coefficients, which preserve the low-frequency baseline trends, and detail (high-pass) coefficients, which preserve the high-frequency Acc/Dec edges. Cascading these decompositions through successive layers yields a hierarchical, multi-scale representation. The decoder uses inverse DWT for full-resolution reconstruction. Skip connections are equipped with an Interactive Coefficient Selection (ICS) module that learns attention masks to suppress Doppler noise and motion artefacts in the detail stream while amplifying diagnostically salient transients. To enhance spectral diversity, five complementary wavelet bases (db4, db6, sym4, sym5, bior3.5) operate in parallel; a simple voting layer fuses their outputs, eliminating manual basis tuning. Evaluated on four FHR datasets, WaveFHR-VNet achieved state-of-the-art performance, with improvements of up to 5.3995% Dice, 5.4758% IoU, and 4.6263% accuracy over the best baselines on LCU-DB, the most widely used public benchmark. It also demonstrates strong cross-dataset generalization, consistently outperforming all comparison models. These results suggest that WaveFHR-VNet can serve as a reliable tool for intrapartum monitoring.