A Noise-Aware Robustness Evaluation Framework for Breast Cancer Classification in Ultrasound Imaging

Accurate detection of breast cancer is essential, as it remains a leading cause of cancer-related mortality worldwide. Ultrasound is adopted due to its accessibility, safety, and capability, complementing mammography and MRI. Yet interpretation is challenging because images are operator-dependent. This has motivated deep learning (DL) to improve lesion detection, classification, and segmentation. Although DL achieves high accuracy under noise-free conditions, real-world reliability remains underexplored because acquisition factors and speckle noise degrade images, increasing missed-malignancy risk. To address the limited reliability of breast ultrasound classifiers under noisy acquisition conditions, we propose a noise-aware training framework that evaluates model robustness under controlled Gaussian, Poisson, and speckle noise to simulate clinically relevant degradations. We used the publicly available breast ultrasound images (BUSI) dataset, which contains 780 ultrasound images collected in 2018 from 600 female patients, and evaluated a custom convolutional neural network (CNN) and a pretrained Inception V3 model. The framework combines controlled noise modeling, robustness assessment, and noise-matched training across different noise types and severities. Performance was assessed via accuracy and malignant recall. Results show that Gaussian noise most affected the performance of the custom CNN, reducing accuracy by 36.1% at 5 dB signal-to-noise ratio (SNR), while Poisson noise most affected Inception V3, reducing accuracy by 35.2%. Speckle noise produced smaller accuracy changes, but malignant recall declined under high noise. Noise-matched training improved accuracy by up to 56.5% at 5 dB, though gains were smaller at reduced noise. These findings show that noise-aware, recall-preserving evaluation is necessary for safer breast ultrasound analysis.