Abstract
Magnetic resonance imaging systems rely on signal detection via radiofrequency coil arrays which, ideally, need to provide both bendability and form-fitting stretchability to conform to the imaging volume. However, most commercial coils are rigid and of fixed size with a substantial mean offset distance of the coil from the anatomy, which compromises the spatial resolution and diagnostic image quality as well as patient comfort. Here, we propose a soft and stretchable receive coil concept based on liquid metal and ultra-stretchable polymer that conforms closely to a desired anatomy. Moreover, its smart geometry provides a self-tuning mechanism to maintain a stable resonance frequency over a wide range of elongation levels. Theoretical analysis and numerical simulations were experimentally confirmed and demonstrated that the proposed coil withstood the unwanted frequency detuning typically observed with other stretchable coils (0.4% for the proposed coil as compared to 4% for a comparable control coil). Moreover, the signal-to-noise ratio of the proposed coil increased by more than 60% as compared to a typical, rigid, commercial coil.
Highlights
Magnetic resonance imaging (MRI) is an indispensable technique to non-invasively depict anatomic structures and facilitate diagnosis
Commercial RF coils are generally built to accommodate a wide range of anatomical dimensions, which increases the mean offset distance of the coil from the anatomy and reduces the available signal-to-noise ratio (SNR)
We describe a method of fabricating soft and stretchable RF receive coils based on liquid metal and ultra-stretchable polymer with a smart geometry design to provide autotuning capability and mitigate the resonance frequency shift, without using additional tuning circuitry
Summary
Magnetic resonance imaging (MRI) is an indispensable technique to non-invasively depict anatomic structures and facilitate diagnosis. Commercial RF coils are generally built to accommodate a wide range of anatomical dimensions, which increases the mean offset distance of the coil from the anatomy and reduces the available SNR This problem becomes especially challenging when trying to use the same coils for adults as infants or small children[6]. Some commercial arrays provide limited mechanical flexibility, with portions that can be partially folded around the area of interest; this improves coupling between the imaged volume and the coil and affords a slightly higher filling factor, improving RF receive efficiency. These designs are bulky and limited in their flexibility to a single direction. Mercury’s toxicity, and its tendency to assume a spherical shape due to surface tension, limited its use
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