PROJECT SUMMARY This project will develop volumetric real-time magnetic resonance imaging (RT-MRI) technology on a novel 0.55 Tesla platform to provide improved assessment of the heart and airway in motion. Rationale: Volumetric real- time imaging by computed tomography and ultrasound have had a profound impact on our ability to understand and evaluate disorders involving movement and of moving organs. These modalities each have limitations that include ionizing radiation, obstructed visualization angles, and limited contrast. MRI is currently capable of slice- by-slice RT-MRI and a leap to volumetric would enable improved assessment of a wide range of heart and airway disorders. Innovation: NIH has developed a 0.55 Tesla MRI instrument, that we argue will enable a breakthrough in RT-MRI performance. This is due to substantially reduced off-resonance effects, substantially reduced tissue heating, and a leap in scan efficiency due to increased flexibility in the MRI pulse sequence. We propose an innovative intramural-extramural partnership and interdisciplinary team to explore this potential. Approach: The objective of this project is to develop and translate low-latency volumetric RT-MRI methods that provide unprecedented spatio-temporal resolution and spatial coverage and will benefit several heart and airway applications. Specifically, we will: 1- develop and technically validate volumetric RT-MRI data acquisition at the 0.55T field strength, 2- develop and technically validate low-latency volumetric RT-MRI reconstruction, artifact mitigation, and segmentation, and 3- clinically evaluate volumetric RT-MRI in two unique patient cohorts at the NIH Clinical Center where it is likely to make an immediate impact on care—patients with tracheomalacia and relapsing polychondritis (N=20), and patients undergoing MRI-guided invasive cardiac catheterization (N=20). Broader Impact: The proposed volumetric RT-MRI technology is generalizable and could benefit many additional applications, such as cardiac function assessment in arrhythmia, and upper airway assessment in obstructive sleep apnea. The intramural and extramural labs each offer unique and complementary expertise to achieve this ambitious technical development. Creation of this new intramural-extramural collaboration will benefit both research programs and lead to new synergies that include basic research, clinical translation, and training of the next generation of scientists and engineers.