Magnetic resonance imaging is an inherently signal-to-noise-starved technique that limits the spatial resolution, diagnostic image quality and results in typically long acquisition times that are prone to motion artefacts. This limitation is exacerbated when receive coils have poor fit due to lack of flexibility or need for padding for patient comfort. Here, we report a new approach that uses printing for fabricating receive coils. Our approach enables highly flexible, extremely lightweight conforming devices. We show that these devices exhibit similar to higher signal-to-noise ratio than conventional ones, in clinical scenarios when coils could be displaced more than 18 mm away from the body. In addition, we provide detailed material properties and components performance analysis. Prototype arrays are incorporated within infant blankets for in vivo studies. This work presents the first fully functional, printed coils for 1.5- and 3-T clinical scanners.
Purpose To develop methods for characterizing materials used in screen-printed MRI coils and improve SNR with new lower-loss materials. Methods An experimental apparatus is created to characterize dielectric properties of plastic substrates used in receive coils. Coils are fabricated by screen printing conductive ink onto several plastic substrates. Unloaded and sample loaded quality factor (QUnloaded/QLoaded) measurements and scans on a 3T scanner are used to characterize coil performance. An experimental method is developed to describe the relationship between a coil's QUnloaded and the SNR it provides in images of a phantom. Additionally, 3T scans of a phantom and the head of a volunteer are obtained with a proof-of-concept printed 8-channel array and the results are compared to a commercial 12-channel array. Results Printed coils with optimized substrates can exhibit up to 97% of the image SNR when compared to a traditional coil on a loading phantom. QUnloaded and the SNR of coils are successfully correlated. The printed array results in images comparable to the quality given by the commercial array. Conclusion With the methods and materials proposed, the SNR of printed coils approaches that of commercial coils while using a new fabrication technique that provides more flexibility and close contact to the patient's body.
ediatric MRI is often performed with heavy, large, and relatively inflexible coil arrays designed and built for adult MRI. For awake children, these arrays can be intimidating and uncomfortable, thereby restricting the child's breathing. For parents, they contribute to the stress of the examination. For pediatric caregivers, the coils complicate the placement of medical support equipment, such as mechanical ventilation tubes, pulse oximeters, anesthetic lines, respiratory bellows, blood pressure cuffs, electrocardiogram probes, and video goggles. For sedated or anesthetized children, respiratory compromise from heavy coils on the torso requires more invasive respiratory support or bolstering of the coils away from the patient, with a resultant decrease in signal-to-noise ratio (SNR) and reduced parallel imaging acceleration capability. As a result, much work has been aimed at the design of custom-fitted pediatric coils to maintain SNR. Such efforts have included a flexible cardiac array (1), a set of small head coils for pediatric patients (2), and even a novel pneumatically adjustable head coil to maintain a close patient fit (3). In comparison, flexible arrays have also been proposed by Neocoil (Pewaukee, Wis) and ScanMed (Omaha, Neb). Recently, screen-printed MRI coil technology has been developed to increase SNR due to a more compact fit with respect to the patient. Screen-printed MRI coils allow printing on a flexible substrate (4,5). These coils also have been shown to be printable on fabric, and a 12-channel receive array has been used at 3 T (4-7). In addition to the beneficial SNR increase of large dense MRI coil arrays in general (1,8-14), screen-printed technology (15,16) offers the advantage
We have developed a process for fabricating patient specific Magnetic Resonance Imaging (MRI) Radio-frequency (RF) receive coil arrays using additive manufacturing. Our process involves spray deposition of silver nanoparticle inks and dielectric materials onto 3D printed substrates to form high-quality resonant circuits. In this paper, we describe the material selection and characterization, process optimization, and design and testing of a prototype 4-channel neck array for carotid imaging. We show that sprayed polystyrene can form a low loss dielectric layer in a parallel plate capacitor. We also demonstrate that by using sprayed silver nanoparticle ink as conductive traces, our devices are still dominated by sample noise, rather than material losses. These results are critical for maintaining high Signal-to-Noise-Ratio (SNR) in clinical settings. Finally, our prototype patient specific coil array exhibits higher SNR (5 × in the periphery, 1.4 × in the center) than a commercially available array designed to fit the majority of subjects when tested on our custom neck phantom. 3D printed substrates ensure an optimum fit to complex body parts, improve diagnostic image quality, and enable reproducible placement on subjects.
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