Fast Room Temperature Very Low Field-Magnetic Resonance Imaging System Compatible with MagnetoEncephaloGraphy Environment

Abstract

In recent years, ultra-low field (ULF)-MRI is being given more and more attention, due to the possibility of integrating ULF-MRI and Magnetoencephalography (MEG) in the same device. Despite the signal-to-noise ratio (SNR) reduction, there are several advantages to operating at ULF, including increased tissue contrast, reduced cost and weight of the scanners, the potential to image patients that are not compatible with clinical scanners, and the opportunity to integrate different imaging modalities. The majority of ULF-MRI systems are based, until now, on magnetic field pulsed techniques for increasing SNR, using SQUID based detectors with Larmor frequencies in the kHz range. Although promising results were recently obtained with such systems, it is an open question whether similar SNR and reduced acquisition time can be achieved with simpler devices. In this work a room-temperature, MEG-compatible very-low field (VLF)-MRI device working in the range of several hundred kHz without sample pre-polarization is presented. This preserves many advantages of ULF-MRI, but for equivalent imaging conditions and SNR we achieve reduced imaging time based on preliminary results using phantoms and ex-vivo rabbits heads.

High-sensitivity in vivo contrast for ultra-low field magnetic resonance imaging using superparamagnetic iron oxide nanoparticles

“…Recently, the clear market for a low-cost, portable MRI scanner, particularly in the field of emergency medicine, has led to the design and construction of several prototype MRI scanners that operate at low magnetic fields (<0.3 T) (4), where it becomes economically advantageous to generate the main B 0 magnetic field with permanent magnets (5)(6)(7)(8)(9)(10)(11). Further reduction of B 0 into the ultra-low field regime (ULF; B 0 <10 mT) (12) makes possible MRI scanners based on inexpensive, and lightweight, electromagnets (13)(14)(15)(16). Using modern hardware and new acquisition techniques, this new wave of low-cost scanners can acquire far superior diagnostic information (13) to earlier generations of low-field MRI scanners (17) and could become common screening tools, particularly at remote hospitals and medical clinics (4).…”

Optimized 3D co-registration of ultra-low-field and high-field magnetic resonance images

“…VLF MRIs were recorded on a prototype operating at a static field of 8.9 mT inside a magnetically shielded room [ 6 ]. We used a Spin Echo (SE) sequence, cartesian sampling with 1×1×1 mm 3 resolution, 6.4×6.4×6.4 cm 3 FOV, TR = 500 ms, TE = 19 ms, NEX = 37 and total acquisition time of 8.5 min for each volume.…”

“…In the last 15 years, new instrumental apparatuses have been developed to perform Magnetic Resonance Imaging (MRI) at low fields (LF MRI, B < 10 mT), in contrast to the general tendency to increase the magnetic field strength for higher spatial resolution (see [ 1 , 2 ] for reviews on actual LF NMR/MRI instruments and applications). These devices operate at field levels ranging from ~1 μT (Ultra Low Field, ULF [ 3 , 4 ]) to ~10 mT (Very Low Field, VLF [ 3 – 6 ]).…”

Design and Analysis of a Whole-Body Noncontact Electromagnetic Subthreshold Stimulation Device with Field Modulation Targeting Nonspecific Neuropathic Pain

“…When the resonant frequency becomes low as in the present case, the standard RF birdcage coil will possess very low inductance L. Tuning such a coil toward resonance at low frequencies would require large capacitance C. This, however, means a low Q-factor (quality factor Q L C R = / / is the "gain" of the series resonator) and higher costs, as well as higher fabrication complexity [83,84], and will restrict the use of the conventional birdcage coil to frequencies above at least a few megahertz. Different methods to overcome this difficulty have been suggested [83][84][85][86][87][88], but they are all limited to small-size coils.…”