4. Discussion
This study addresses a critical challenge in medical imaging: balancing the need for large, high-quality datasets to train machine learning models with the need to protect patient privacy. By using generative models—specifically, Latent Diffusion Models (LDMs)—we demonstrate a viable path towards privacy-preserving synthetic data generation that preserves practical utility.
The main key contribution of this work is the development of a pipeline capable of generating mammographic images conditioned on diagnostic and spatial metadata, such as lesion location and projection type. This conditional synthesis approach can produce realistic and diverse samples while preserving essential diagnostic features. The use of a KL-VAE-based encoder–decoder further enhanced image fidelity, achieving a 5.8 FID score. Ref. [
48] presents FID 4.383 and [
49] 52.89, but the studies are incomparable due to different datasets.
Our experiments revealed that the synthetic dataset is sufficient for training cancer classification models: a classifier trained solely on synthetic images achieved an ROC-AUC of 0.77 compared to 0.82 when trained on real data. Although there is a slight degradation in performance, the gap is relatively small, suggesting the potential of synthetic data as a surrogate in scenarios where access to real data is limited or legally restricted.
Importantly, the privacy evaluation demonstrated strong robustness to re-identification attempts. By training and testing an SNN-based identification model, we confirmed that synthetic images do not contain one-to-one mappings to original data. Re-identification metrics (e.g., mAP@R ≈ 0.0051) and distance distributions support the conclusion that patient identity is effectively obscured. Furthermore, human evaluators were unable to reliably distinguish between real and synthetic samples in a blinded setting further affirming the realism of synthetic data.
Our results underscore a fundamental trade-off between data fidelity and privacy: improving synthetic realism does not have to come at the cost of leaking patient-specific features. The presented method strikes a compelling balance by incorporating semantic information (through masks and labels) while introducing sufficient latent-space variability to reduce similarity to real inputs.
Nevertheless, the synthetic data is derived from masks based on the original data, which could still embed subtle patient-specific traits if not carefully designed. Moreover, the cancer classification task, while illustrative, does not encompass the full spectrum of diagnostic applications. Further studies are needed to evaluate the utility of synthetic datasets for segmentation, detection, or multi-class classification tasks. While our privacy analysis includes standard metrics and qualitative inspection, formal guarantees such as differential privacy bounds were not established and represent an important direction for future research.
To sum up, this paper presents a comprehensive framework for generating private synthetic mammograms. Our key contributions are as follows:
High-quality image generation: We developed a generative model, specifically a Latent Diffusion Model (LDM), that produces realistic synthetic mammograms, achieving a state-of-the-art Fréchet Inception Distance (FID) score of 5.808. A blinded evaluation by a radiologist confirmed the visual fidelity, with an identification accuracy of only 43% (close to random chance).
Generative network results: The generated synthetic data achieved a Fréchet Inception Distance (FID) of 5.8, preserving diagnostic features.
Preservation of diagnostic utility: We verified that the synthetic data retains clinical value. A cancer classification model trained exclusively on our generated data achieved an ROC-AUC of 0.77, demonstrating only a slight performance drop compared to a model trained on original data (ROC-AUC: 0.82) and proving its practical utility for downstream tasks.
Robust patient privacy assurance: We rigorously evaluated privacy risks. Our identification model showed near-zero re-identification accuracy (mAP@R of 0.001 on the training set), and a distribution analysis of image embeddings confirmed that synthetic images are significantly less similar to their original counterparts than original images are to each other, effectively mitigating the risk of data leakage.
Overall, the study confirms that LDM-based synthetic data generation can be a powerful tool in privacy-sensitive domains, offering a way to enable open collaboration and data sharing without compromising patient confidentiality. Future work will focus on enhancing the conditioning mechanism, introducing formal privacy guarantees, and testing scalability across diverse imaging modalities and institutions.
In future work, we plan to take a closer look at more privacy attacks on our pipeline. We plan to test attribute-inference attacks and run ablations to see how much leakage comes from lesion cues and overall breast shape. On the defense side, we will try different fine-tuning techniques, simple regularization of the loss/conditioning (including randomized masking and small geometry tweaks), and basic output filters based on embedding similarity.
Another potential next step is a multi-reader study to check how well radiologists detect and classify lesions on synthetic mammograms. Using blinded, lesion-level reads and standard ROC/FROC measures, we would compare the results with matched real images to verify non-inferiority.
Author Contributions
Conceptualization, D.S., E.U., A.L., and Y.M.; methodology, D.S. and E.U.; software, D.S. and E.U.; validation, D.S., E.U., and Y.M.; formal analysis, Y.M.; investigation, D.S.; resources, Y.M.; data curation, E.U.; writing—original draft preparation, D.S.; writing—review and editing, D.S., E.U., A.L., and Y.M.; visualization, D.S.; supervision, Y.M.; project administration, E.U. and Y.M.; funding acquisition, Y.M. All authors have read and agreed to the published version of the manuscript.
Funding
This work was supported by a grant, provided by the Ministry of Economic Development of the Russian Federation in accordance with the subsidy agreement (agreement identifier 000000C313925P4G0002) and the agreement with the Ivannikov Institute for System Programming of the Russian Academy of Sciences dated 20 June 2025 No. 139-15-2025-011.
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
The data presented in this study are available on request from the corresponding author.
Conflicts of Interest
The authors declare no conflicts of interest.
Abbreviations
The following abbreviations are used in this manuscript:
ML | Machine Learning |
LDM | Latent Diffusion Model |
CLDM | Conditional Latent Diffusion Model |
VAE | Variational Autoencoder |
VQ-VAE | Vector Quantized Variational Autoencoder |
KL-VAE | Kullback–Leibler Variational Autoencoder |
GAN | Generative Adversarial Network |
SNN | Siamese Neural Network |
FID | Fréchet Inception Distance |
BI-RADS | Breast Imaging Reporting and Data System |
CT | Computed Tomography |
MRI | Magnetic Resonance Imaging |
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