QASCI-Quadruple Asymmetric Saddles for Cardiac Imaging

Introduction: The existing cardiac coil in the market is an 8-channel coil with 4 anterior loops and four posterior loops with a fieldof-view coverage of 30 cm by 30 cm. One finds that the clinical demand for cardiac coils is split into two segments: one is those coils which are solely for cardiac imaging with a field-of-view requirement of 30 cm by 30 cm to cover the heart only; the other segment is for cardiovascular imaging with a field-of-view requirement of 48 cm by 48 cm in order to be capable of performing vascular imaging. In order to increase channel count, element size must be restricted, which limits the coil’s penetration depth, and thus sensitivity to deep tissues. In addition, most high channel cardiac imaging coil systems are both heavy and bulky, making them difficult for the technician/operator to use, and cause the patient discomfort. Therefore a need exists to create a cardiac/cardiovascular imaging coil system that is lightweight, simple to use, and which offers excellent imaging performance throughout the thoracic region. In this study we have constructed a 32-channel phased array MRI coil system designed specifically for cardiac and thoracic vascular imaging. What makes the coil unique and unlike prior art is the specific combination of geometric elements within the design. A new array motif design, the QASQI (Quadruple Asymmetric Saddle for Cardiac Imaging), is used to generate those elements closest to the cardiac region, where they comprise a total of 16 channels (or half of the total channels) of the overall design (Fig 1). To aid patient comfort, the eight rectangular loops can be detached from the QASCI core when cardiac-only imaging is needed, thus decreasing the weight of the system. Thus, an integrated design approach is taken to realize a user-friendly system that is highly optimized for clinical cardiac imaging use. Methods and Materials: The methods consisted of hardware development, modeling and data measurement. Hardware Development: When two groups of QASCI elements are combined with eight rectangular-loop elements, the overall design of the present coil is realized (Fig 1). The peripheral loops provide the depth-of-penetration needed to view deep vasculature, while the four QASCI elements provide a relatively shallow but very high SNR/resolution image of the heart itself. With this combination of elements, it is possible to view the entirety of the thorax, but the FOV has been optimized specifically to meet the needs of cardiac and vascular imaging. Data Measurement: Phantom testing for each topology was done using 1.5T GE Excite scanner and a sequence (TR/TE = ms/ms; 256*128; FOV = 44cm) and a SOS reconstruction.