Abstract
Low-field permanent magnet-based MRI systems are finding increasing use in portable, sustainable and point-of-care applications. In order to maximize performance while minimizing cost many components of such a system should ideally be designed specifically for low frequency operation. In this paper we describe recent developments in constructing and characterising a low-field portable MRI system for in vivo imaging at 50 mT. These developments include the design of i) high-linearity gradient coils using a modified volume-based target field approach, ii) phased-array receive coils, and iii) a battery-operated three-axis gradient amplifier for improved portability and sustainability. In addition, we report performance characterisation of the RF amplifier, the gradient amplifier, eddy currents from the gradient coils, and describe a quality control protocol for the overall system.
Highlights
In addition to specific hardware improvements including a gradient coil with increased region of linearity, a four-element phased array receive coil, and a battery-operated gradient amplifier, detailed system characterisations of eddy currents, RF transmitter performance, and quality control protocol have been shown
The comparison of two axial gradient coils simulated for the same target DSV, but designed using two different target field methods, demonstrated that for fixed dimensions, in simulations, the new method increases the 5% linear DSV by ∼150%, traded against a decrease in efficiency of ∼25%
The increase in axial linearity allows the whole adult brain to be imaged with little geometric distortion, at a spatial resolution of ∼2 mm using the maximum output of 4 Amps from the gradient amplifier
Summary
In the past 15 years several groups have shown significant progress in the design of low field (
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