A Flexible and Modular Receiver Coil Array for Magnetic Resonance Imaging

Adaptable, wearable, and stretchable coils: A review

Over the last four decades, there have been various evolutions in the design and development of coils, from volume coils to the recent introduction of wireless receive arrays. A recent aim has been to develop coils that can closely conform to the anatomy of interest to increase the acquired signal. This goal has given rise to designs ranging from adaptable transmit coils to on-body stretchable receive arrays made using fabric or elastomer substrates. This review covers the design, fabrication details, experimental setup, and MRI results of adaptable, wearable, and stretchable MRI coils. The active and passive automatic tuning and matching strategies are examined with respect to mitigating signal-to-noise ratio reduction when the coil form is altered. A brief discussion of wireless MRI coils, which provide a solution to overcome the cabling issues associated with MRI coil development, is also included. The adaptable, wearable, and stretchable coils and various coil tuning techniques represent innovative radiofrequency coil solutions that pave the way for next-generation MRI hardware development.

Wireless, customizable coaxially shielded coils for magnetic resonance imaging

Anatomy-specific radio frequency receive coil arrays routinely adopted in magnetic resonance imaging (MRI) for signal acquisition are commonly burdened by their bulky, fixed, and rigid configurations, which may impose patient discomfort, bothersome positioning, and suboptimal sensitivity in certain situations. Herein, leveraging coaxial cables' inherent flexibility and electric field confining property, we present wireless, ultralightweight, coaxially shielded, passive detuning MRI coils achieving a signal-to-noise ratio comparable to or surpassing that of commercially available cutting-edge receive coil arrays with the potential for improved patient comfort, ease of implementation, and substantially reduced costs. The proposed coils demonstrate versatility by functioning both independently in form-fitting configurations, closely adapting to relatively small anatomical sites, and collectively by inductively coupling together as metamaterials, allowing for extension of the field of view of their coverage to encompass larger anatomical regions without compromising coil sensitivity. The wireless, coaxially shielded MRI coils reported herein pave the way toward next-generation MRI coils.

Flexible multi-purpose integrated RF/shim coil array for MRI and localized B0 shimming

PURPOSE

To develop a flexible, lightweight, and multi-purpose integrated parallel reception, excitation, and shimming (iPRES) coil array that can conform to the subject's anatomy and perform MR imaging and localized B0 shimming in different anatomical regions with a high SNR, shimming performance, ease of positioning, and subject comfort.

METHODS

A four-channel flexible iPRES coil array was constructed by enabling RF and direct currents to flow on the same flexible coil elements for imaging and shimming, respectively. Shimming experiments were performed with the coil array wrapped around the knee or neck of healthy subjects to demonstrate its high shimming performance and versatility. Additionally, its SNR and shimming performance in the knee were compared to those obtained with the coil array wrapped around a larger rigid tube designed to fit most knee sizes.

RESULTS

Shimming with the coil array wrapped around the knee or neck resulted in an average reduction in B0 RMSE of 50.1% and 40.5% relative to first-order and second-order spherical harmonic shimming, respectively, and substantially reduced distortions in DWI images. In contrast, shimming the knee with the coil array wrapped around the rigid tube only provided a 29.6% reduction in B0 RMSE, whereas the SNR was reduced by 58.7%.

CONCLUSION

The flexible iPRES coil array can conform to different anatomical regions and perform imaging and localized B0 shimming with a higher SNR, shimming performance, ease of positioning, and comfort compared to a rigid iPRES coil array, which should be valuable for many applications throughout the human body.

Performance of a Flexible 12-Channel Head Coil in Comparison to Commercial 16- And 24-Channel Rigid Head Coils

Purpose: To compare the performance of a 12-channel flexible head coil (HFC12) with commercial 16-channel (HRC16) and 24-channel (HRC24) rigid coils.

Methods: The phantom study was performed on a 1.5 T MR scanner with HFC12, HRC16, and HRC24. The SNR and noise correlation matrix of T1WI, T2WI, and diffusion weighted imaging (DWI) were measured. The SNR profiles were created according to the SNR. In addition, 1/g-factors were calculated in different acceleration directions. In the in vivo study, T1WI, T2WI, and DWI were performed in one healthy volunteer with three different coils. The SNR and noise correlation matrix were measured.

Results: In the phantom study and in vivo study, the SNR of HFC12 in the transverse, sagittal, and coronal planes was the highest, followed by HRC24, and that of HRC16 was the lowest. The SNR profiles showed that the SNR at the edge of HFC12 was the highest. The mean value of the noise correlation matrix of HFC12 was the highest. The 1/g-factor results showed that HFC12 obtained the best acceleration ability in the head–foot acceleration direction when the reduction factor was set to two. The SNR of HFC12 in most cortices was significantly higher than that of HRC16 and HRC24, except in the occipital cortex. The SNR of HRC24 in the occipital cortex was higher than that of HFC12.

Conclusion: The SNR of HFC12 in T1WI, T2WI, and DWI was better than that of the HRC24 and HFC16. The SNR of HFC12 in the cortex was significantly higher than that of the commercial rigid head coil, except in the occipital cortex.

The Core of Medical Imaging: State of the Art and Perspectives on the Detectors

In this review, the roles of detectors in various medical imaging techniques were described. Ultrasound, optical (near-infrared spectroscopy and optical coherence tomography) and thermal imaging, magnetic resonance imaging, computed tomography, single-photon emission tomography, positron emission tomography were the imaging modalities considered. For each methodology, the state of the art of detectors mainly used in the systems was described, emphasizing new technologies applied.

Simultaneous Head and Spine MR Imaging in Children Using a Dedicated Multichannel Receiver System at 3T

OBJECTIVE

The purpose of this work was to enable simultaneous head and spine Magnetic Resonance imaging (MRI) in children at 3T by using a dedicated multichannel radiofrequency coil array system.

METHODS

A 24-channel head and spine pediatric coil system was developed and constructed. The coils performance was compared with a commercially available 24-channel adult head-neck coil and a spine coil (1-4 spine of 16-channel were selected). Signal-to-noise ratio (SNR) and parallel imaging capability were quantitatively evaluated by phantom studies and in vivo imaging experiments. With Institutional Review Board and Ethics Committee approval, the designed coil was used to acquire head and spine images on 27 children in clinical settings.

RESULTS

The pediatric coil provided substantial SNR improvements with an increase of 32 % to 40 % in the brain region and up to a two-fold increase in the surface. SNR increased by at least 18 % in the spine region. The coil enabled higher resolution and a faster imaging speed, owing to significantly improved SNR. Extensive coverage of the coil enabled high-quality fast imaging from head-neck to the whole spine. Good image quality with an average score 4.63 out of 5 was achieved using the developed pediatric coil in clinical studies.

CONCLUSION

Simultaneous head and spine MRI with superior performance have been successfully acquired in children subjects at 3T using the dedicated 24-channel head and spine pediatric coil system.

SIGNIFICANCE

The 24-channel pediatric coil system potentially can enhance pediatric head and spine MRI in clinical research and diagnosis.

Making Magnets More Attractive: Physics and Engineering Contributions to Patient Comfort in MRI

Patient comfort is an important factor of a successful magnetic resonance (MR) examination, and improvements in the patient's MR scanning experience can contribute to improved image quality, diagnostic accuracy, and efficiency in the radiology department, and therefore reduced cost. Magnet designs that are more open and accessible, reduced auditory noise of MR examinations, light and flexible radiofrequency (RF) coils, and faster motion-insensitive imaging techniques can all significantly improve the patient experience in MR imaging. In this work, we review the design, development, and implementation of these physics and engineering approaches to improve patient comfort.