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Dynamically adjustable permanent magnet arrays have been proposed to generate switchable magnetic fields for pre-polarisation in Ultra-Low Field magnetic resonance imaging. However, the optimal switching dynamics of the pre-polarisation magnetic field as well as the energy requirements, mechanical forces and stresses during switching of the pre-polarisation field have not been evaluated. We analysed these requirements numerically and estimated the magnetic resonance signal strength and image quality for two practical switching modes in an instrument suitable for scanning the human head. Von Mises stress analysis showed that although magnetic forces were significantly higher for two specific rungs, the structural integrity of magnet rungs would not be compromised. Our simulations suggest that a significantly higher signal yield is obtained by switching off the pre-polarisation field with the angular velocity in each rung dependent on its location.

We describe with a theoretical and numerical analysis the use of small permanent magnets moving along prescribed helical paths for 3D spatial encoding and imaging without sample adjustment in ultra-low field magnetic resonance imaging (ULF-MRI). With our developed method the optimal magnet path and orientation for a given encoding magnet number and instrument architecture can be determined. As a proof-of-concept, we studied simple helical magnet paths and lengths for one and two encoding magnets to evaluate the imaging efficiency for a mechanically operated ULF-MRI instrument with permanent magnets. We demonstrate that a single encoding magnet moving around the sample in a single revolution suffices for the generation of a 3D image by back projection.

Today’s societies are challenged by the increasing costs of healthcare and global inequality in the availability, accessibility, appropriateness and affordability of medical technologies. There are ways to improve equality and efficiency and decrease costs in this area without fundamentally changing current health systems and business models. Many services and products are experiencing a paradigm shift toward an open source economic model that can be extended to medical technologies in a way that will intrinsically promote sustainable growth and innovations while improving education and global health. This new way of thinking offers an infrastructure by which some sectors of global health can be democratized. Here we present an in-depth discussion of the advantages of open source medical technology for the public and private sectors, then provide a concrete example of the progress of our efforts to develop an open source magnetic resonance imaging (MRI) scanner. Based on our calculations such an instrument could potentially result in cost savings of up to $3.3 billion within about 20 years for the German healthcare system alone. On a global scale the implications of an affordable open source MRI would be even more striking. We suggest a series of milestones to be met to a widespread development of open source medical technology with the aim of improving global health in a way that is less restricted by current political and economic borders.

Object We studied the feasibility of generating the variable magnetic fields required for ultra-low field nuclear magnetic resonance relaxometry with dynamically adjustable permanent magnets. Our motivation was to substitute traditional electromagnets by distributed permanent magnets, increasing system portability. Materials and Methods The finite element method (COMSOL® ) was employed for the numerical study of a small permanent magnet array to calculate achievable magnetic field strength, homogeneity, switching time and magnetic forces. A manually operated prototype was simulated and constructed to validate the numerical approach and to verify the generated magnetic field. Results A concentric small permanent magnet array can be used to generate strong sample prepolarisation and variable measurement fields for ultra-low field relaxometry via simple prescribed magnet rotations. Using the array, it is possible to achieve a pre-polarisation field strength above 100 mT and variable measurement fields ranging from 20-50 μT with 200 ppm absolute field homogeneity within a field-of-view of 5 x 5 x 5 cubic centimetres. Conclusions A dynamic small permanent magnet array can generate multiple highly homogeneous magnetic fields required in ultra-low field nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) instruments. This design can significantly reduce the volume and energy requirements of traditional systems based on electromagnets, improving portability considerably.