Hyperpolarized helium and xenon MRI of the lungs has been shown to provide useful physiological information about pulmonary function. Hyperpolarized helium imaging has been shown to provide outstanding imaging of lung gas spaces while allowing for structure-function information such as alveolar dimensions and oxygen depletion. Hyperpolarized xenon dissolves in the blood pool through lung parenchyma, opening up the potential for simultaneous ventilation and perfusion imaging and gas exchange measurements. Further, imaging of inert fluorinated gases such as SF6 show great promise for pulmonary imaging. While much work has been performed to characterize the utility of gas imaging, the field still remains in the research phase, partially due to the lack of available clinical RF technology for multinuclear scanning. Here, we propose to create an RF coil and interface platform that can be permanently tuned to any of the aforementioned specific frequencies. Further, this technology will be specifically created for 3T magnets, a field strength that more and more hospitals are purchasing and installing. This coil and interface design will be developed by Ralph Hashoian at Clinical MR Solutions, who has previously designed and delivered coils for gas imaging, and it will be validated and tested by Mitchell Albert at the University of Massachusetts Medical School, a co-inventor of in vivo hyperpolarized gas imaging. Our coil design will consist of a transmit/receive quadature flexible coil with four loop elements. This design will simultaneously allow for patient comfort and homogenous transmission with high signal to noise reception. Our preliminary results at 1.5T using this type of coil design in hyperpolarized helium imaging have produced excellent results. The coil interface will consist of a low loss, high power transmit receive switch, low noise pre-amplifiers, and a Quadrature hybrid, all integrated into an injection molded enclosure that will plug into the main system coil connection. Included will be specific OEM required circuits for coil ID, fault analysis and PIN diode drivers. This integrated interface approach will allow for easier coil connections for all the gas frequencies involved in the study and ensure a simple, robust and clinically relevant interface. Finally, our RF coil design and interface platform will be designed to overcome the challenges at 3T including high RF power deposition, increased patient impedance matching loss, and patient safety concerns. Once developed, we will test our design by acquiring hyperpolarized helium ventilation and airway images. These images will be evaluated by a radiologist for image quality and homogeneity. Taken together, our design will offer more clinically effective RF coils and interface to the research community and ultimately hasten the transition to the clinic.
Hyperpolarized gas and inert fluorinated gas MR imaging stand at the doorstep of clinical application. However, their advancement to the clinic is hindered by the lack of available multinuclear RF technology to perform these exams. Here, we propose an RF coil design and scanner interface that is seamlessly integrated into the clinical scanner to image hyperpolarized helium, xenon, or inert fluorinated gases at 3T. This design, which is targeted for clinical compliance, will allow for high signal to noise imaging while maintaining patient comfort and safety. Taken together, the proposed architecture of an integrated coil and interface will facilitate clinical gas lung imaging and ultimately help facilitate clinical acceptance and translational research of the technique.
