Prompt2Perturb (P2P): Text-Guided Diffusion-Based Adversarial Attacks on
  Breast Ultrasound Images
Authors: name: Yasamin Medghalchi, name: Moein Heidari, name: Clayton Allard, name: Leonid Sigal, name: Ilker Hacihaliloglu

Deep neural networks (DNNs) offer significant promise for improving breast
cancer diagnosis in medical imaging. However, these models are highly
susceptible to adversarial attacks--small, imperceptible changes that can
mislead classifiers--raising critical concerns about their reliability and
security. Traditional attacks rely on fixed-norm perturbations, misaligning
with human perception. In contrast, diffusion-based attacks require pre-trained
models, demanding substantial data when these models are unavailable, limiting
practical use in data-scarce scenarios. In medical imaging, however, this is
often unfeasible due to the limited availability of datasets. Building on
recent advancements in learnable prompts, we propose Prompt2Perturb (P2P), a
novel language-guided attack method capable of generating meaningful attack
examples driven by text instructions. During the prompt learning phase, our
approach leverages learnable prompts within the text encoder to create subtle,
yet impactful, perturbations that remain imperceptible while guiding the model
towards targeted outcomes. In contrast to current prompt learning-based
approaches, our P2P stands out by directly updating text embeddings, avoiding
the need for retraining diffusion models. Further, we leverage the finding that
optimizing only the early reverse diffusion steps boosts efficiency while
ensuring that the generated adversarial examples incorporate subtle noise, thus
preserving ultrasound image quality without introducing noticeable artifacts.
We show that our method outperforms state-of-the-art attack techniques across
three breast ultrasound datasets in FID and LPIPS. Moreover, the generated
images are both more natural in appearance and more effective compared to
existing adversarial attacks. Our code will be publicly available
https://github.com/yasamin-med/P2P.