During the past year we have continued enhancement of imaging platforms to guide cardiovascular catheter based treatments. These have included co-registered MRI with conventional X-ray, as well as standalone real-time MRI. Static 3D roadmaps derived from MRI datasets are used to enhance image guidance for X-ray cardiovascular interventional procedures, and indeed have been used in this lab to develop novel treatments such as mitral cerclage annuloplasty. Static roadmaps do not accurately represent cardiovascular anatomy during cardiac and respiratory motion. We have developed a system to measure respiratory and cardiac motion from real-time MRI scans and to derive a set of affine models which can be used to beat and breath the 3D roadmaps overlaid on live X-ray. We also have developed robust fully automatic mathematical techniques to register fiducial markers between imaging modalities. We have worked with an industry collaborator to translate our locally developed environment into a clinical industrial prototype for testing in adults and children. We continue to enhance a system for safe patient hemodynamic monitoring and recording during interventional MRI experiments and during transfer between X-ray and MRI. We have developed a system capable of adaptive noise cancellation to filter out RF and magnetic gradient interference. We continue work towards a wireless physiological telemetry system. We will begin work with an SBIR contractor collaborator to translate this work into a clinical industrial prototype for testing in adults and children. Our collaborator Michael S. Hansen has used inexpensive parallel computing resources afforded by game-oriented graphics processing units to accelerate reconstruction of computationally-intensive MRI data. We have successfully integrated non-Cartesian parallel imaging in an interactive acquisition and reconstruction setup and demonstrated that real-time reconstruction and visualization is possible for relatively complicated reconstruction algorithms. This has been integrated with the scanner software to allow seamless combination with other sequence components. This has been disseminated as an open-source image-streaming framework that has become very popular with extensive applications in biomedical imaging. We have developed a system to provide the operator multiple simultaneous representations of real-time MRI data balancing temporal and spatial resolution interactively. The operator chooses the desired representation. We have implemented golden-angle real-time MRI with interactive selection of the temporal resolution. We are migrating our highly successful local real-time MRI software environment onto a commercial platform to facilitate translation outside of NIH, and to enhance industry and university collaboration. This has required considerable development to update workhorse real-time MRI pulse sequences to facilitate rapid multi-author or multi-institution prototyping. This development has allowed investigational human MRI catheterization to be performed with the staff support of a technologist rather than a physicist, reflecting a polished and clinically-relevant system. We also continue to enhance the real-time MRI imaging host and image reconstruction environment, for example to balance temporal and spatial resolution interactively, and to enhance operator workflow during real-time MRI clinical catheterization. We continue work with an industry collaborator to translate our locally developed capabilities into a clinical industrial prototype for testing in adults and children. We have worked with NHLBI collaborators to explore surface coil RF excitation strategies to reduce energy deposition on conductive catheter devices. We have been able to reduce energy deposition by approximately half without significant degradation in image quality, but seek further reduction in heating. We have begun work on real-time MR imaging pulse sequences with reduced energy deposition to enhance the safety of interventional MRI using conductive catheter devices, to avoid heating. This has additional utility in safe MRI in patients with implanted devices such as pacemakers and defibrillators. We also continue to develop new approaches to real-time MRI, or to engineer local noncommercial embodiments of real-time MRI to suit the needs of procedures being developed.
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