PhaseGen: A Diffusion-Based Approach for Complex-Valued MRI Data Generation
This work addresses the gap for medical imaging researchers and clinicians by enabling pretraining of models that require complex-valued data, leveraging existing magnitude datasets for more accurate diagnostic tasks, though it is incremental in applying diffusion models to this specific domain.
The paper tackles the problem of generating synthetic complex-valued MRI raw data (k-Space) conditioned on magnitude images, which are commonly used but discard phase information. The result shows that training with synthetic phase data improves skull-stripping segmentation accuracy from 41.1% to 80.1% and enhances MRI reconstruction when combined with limited real data.
Magnetic resonance imaging (MRI) raw data, or k-Space data, is complex-valued, containing both magnitude and phase information. However, clinical and existing Artificial Intelligence (AI)-based methods focus only on magnitude images, discarding the phase data despite its potential for downstream tasks, such as tumor segmentation and classification. In this work, we introduce $\textit{PhaseGen}$, a novel complex-valued diffusion model for generating synthetic MRI raw data conditioned on magnitude images, commonly used in clinical practice. This enables the creation of artificial complex-valued raw data, allowing pretraining for models that require k-Space information. We evaluate PhaseGen on two tasks: skull-stripping directly in k-Space and MRI reconstruction using the publicly available FastMRI dataset. Our results show that training with synthetic phase data significantly improves generalization for skull-stripping on real-world data, with an increased segmentation accuracy from $41.1\%$ to $80.1\%$, and enhances MRI reconstruction when combined with limited real-world data. This work presents a step forward in utilizing generative AI to bridge the gap between magnitude-based datasets and the complex-valued nature of MRI raw data. This approach allows researchers to leverage the vast amount of avaliable image domain data in combination with the information-rich k-Space data for more accurate and efficient diagnostic tasks. We make our code publicly $\href{https://github.com/TIO-IKIM/PhaseGen}{\text{available here}}$.