Low-Cost High-Performance MRI

Abstract

Magnetic Resonance Imaging (MRI) is unparalleled in its ability to visualize anatomical structure and function non-invasively with high spatial and temporal resolution. Yet to overcome the low sensitivity inherent in inductive detection of weakly polarized nuclear spins, the vast majority of clinical MRI scanners employ superconducting magnets producing very high magnetic fields. Commonly found at 1.5–3 tesla (T), these powerful magnets are massive and have very strict infrastructure demands that preclude operation in many environments. MRI scanners are costly to purchase, site, and maintain, with the purchase price approaching $1 M per tesla (T) of magnetic field. We present here a remarkably simple, non-cryogenic approach to high-performance human MRI at ultra-low magnetic field, whereby modern under-sampling strategies are combined with fully-refocused dynamic spin control using steady-state free precession techniques. At 6.5 mT (more than 450 times lower than clinical MRI scanners) we demonstrate (2.5 × 3.5 × 8.5) mm3 imaging resolution in the living human brain using a simple, open-geometry electromagnet, with 3D image acquisition over the entire brain in 6 minutes. We contend that these practical ultra-low magnetic field implementations of MRI (<10 mT) will complement traditional MRI, providing clinically relevant images and setting new standards for affordable (<$50,000) and robust portable devices.

Yield of Brain MRI in Clinically Diagnosed Epilepsy in the Kingdom of Bhutan: A Prospective Study

“…High quality images through the introduction of new technologies like low magnetic field implementation of MRI could soon provide clinically relevant images via affordable and portable devices (Sarracaine et al, 2015). Additionally, current systems to exchange images and share files make the evaluation of the results and remote second opinions relatively easy for future patients (Potchen et al, 2013).…”

Low-Field Cardiac Magnetic Resonance Imaging

“…Given the preponderance of CMR techniques that are, or can be, based on the bSSFP readout including cine, perfusion, late gadolinium enhancement (LGE), T1 mapping, T2 mapping, and non-contrast angiography, it is possible that much of the SNR lost at lower field may be gained back by appropriate choice of pulse sequence and imaging parameters. bSSFP is the most efficient acquisition strategy in terms of SNR per unit time, and its effectiveness at low field is well-known 20, 21 . Besides SAR limiting the effectiveness of bSSFP at 3T and above, especially for cine and bright blood angiography, the technique is also highly sensitive to static magnetic field homogeneity.…”

Adaptive suppression of power line interference in ultra-low field magnetic resonance imaging in an unshielded environment

“…However, power-line harmonic interference and fixedfrequency noise peaks constitute a problem both in unshielded environment and in a shielded room, faced both by SQUID and inductive detection [16,22]. For instance, in vivo human brain imaging using SQUIDs [23] and coils [24] as detectors, and lung imaging based on hyperpolarized gases in a conductively shielded room [25] may all endure the power-line harmonic interference. These interference mechanisms introduce stripe-artifacts in MRI images, reducing the image quality and narrowing the signal band.…”