Novel RF Driven MRI Magnet for Imaging Enhancement

The RF-MAFS project is devoted to develop new technology in the portable Magnetic Resonance Imaging (MRI) field. The problems of commercial MRI devices are their sizes and initial/operational cost. Also, their deployment involves large facilities inside hospitals which makes them impossible to be used inside Emergency Rooms (ER) or ambulances.
There are different prototypes of portable MRI machines developed during the last decade. However, none of them posses neither the spatial resolution nor the sizes and EMC compatibility characteristics to be deployed in ER or ambulances. The proposed technology in this project addresses these to problems by developing the first Radio-Frequency Magic Angle Field Spinning magnet. In this way, a fundamental medical tool in injury and disease diagnosis will be available in ER, ambulances or even in low-budget medical facilities.
The RF-MAFS magnet consist in 3 magnets producing 3 different fields. The first magnetic field aligns with the longitudinal axis of the sample under study. The second and the third magnetic fields lay in the transverse plane to the previous magnetic field. This two fields oscillate at the same frequency but out of phase by 90º. If they are also oriented in perpendicular directions, the result is a magnetic field which rotates at the oscillating frequency. The combination of both (longitudinal and rotating) magnetic fields results in a tilted and rotating RF-MAFS field. The amplitude of the longitudinal field with respect to the rotating field controls the tilting angle of the resultant field.
An MRI pulse sequence inside such a magnet will result in a more spatially resolved image compared with the MRI image obtained in a MRI device that produce the same magnetic field but static. Therefore, a very portable MRI device (which will produce a low magnetic field compared with commercial equipment) will have its spatial resolution enhanced making it usable for early medical diagnosis of injuries or diseases.
In order to develop the MRI machine based in the RF-MAFS magnet the objectives of this project are:

1º.- Design, build and test the RF-MAFS magnet able to host a sizable sample.
2º.- Design, build and test the electronics and the software needed to perform MRI experiments inside the RF-MAFS magnet.

These two ambitious objectives have been carried out during two years with the budget provided by the MSCA Fellowship and the support of the government of the Basque Country through the Culture, Linguistics, Politics and Education Department, under Grant IT1104-16. The developed work has resulted in the MRI RF-MAFS prototype assembled and tested electronically and magnetically. It has also resulted in a MSc. Thesis and Graduate final Thesis as teaching training of the experienced researcher and several courses in project planning and management provided by the Government of the Basque Country.
Despite the developed work completes the technology and the hardware/software is tested and characterized of the MRI system, the integration has not been completely debugged and therefore at the moment neither NMR nor MRI experiments have been developed. However, it is intention of the researcher to perform those experiments in the following semester, providing final evidences of the MRI enhancement resulting from the utilization of the RF-MAFS magnet.

The work performed during the project can be broken into two different categories:

2.1 Technology developed during the project:

As a result of these two years, the RF-MAFS magnet has been tested and presented to the scientific community by a publication in a peer-reviewed journal and an scientific conference. The magnet produces 10 mT magnetic flux density, with configurable tilting angle and rotating frequency up to 12 kHz. The homogeneity of the magnetic field is 1000 ppm inside a cylindrical volume of 30 mm diameter and 30 mm length which translates to approx. 400 Hz of spectral width in a Nuclear Magnetic Resonance (NMR) experiments on a water sample.
At the same time, the electronics devoted to perform NMR experiments have been developed. These electronics comprehend: 1) the transmitting and receiving RF coils tuned to 336.21 kHz to 475.36 kHz, 2) the transmitting/receiving RF front-end able to decouple the transmitting and receiving coil, and amplify NMR signals of 2 µV, 3) the signal generation and synchronization platform able to produce RF pulses and TTL signals which enable/disable transmitter and receiver, 4) an extra RF coil tuned around 290 MHz devoted to perform hyperpolarization of the imaged sample by Overhauser Dynamic Nuclear Polarization (O-DNP).

2.2 Training received by the experienced researcher:

As intended by the MSC Actions, the training of the experienced researcher has comprised a large amount of resources. In this way, the training has been focused in both teaching training and industrial training. 1) The hosting institution has allowed the researcher to perform teaching activities such as directing a MSc. Thesis based on the development of one of the coils of the RF-MAFS magnet and a Graduate Final Project consisting in the positioning system for the other two coils of the RF-MAFs magnet. Also, some practical courses on Electronics for Communications were carried out. 2) The Government of the Basque Country, through the hosting institution provided to the experienced researcher with the opportunity of assisting to courses on project planning and management. These courses consisted in monthly classes with experts both from the Basque Country, Spain and abroad.

As stated before, the RF-MAFS magnet is the first of its type. Accordingly with calculations already presented on published contributions, a magnet providing the same spatial resolution that the RF-MAFS magnet should produce around 0.1 T and a device like that must be constructed with an assembly of permanent magnets. Such a magnet would weight around 50 kg and generate a safety circle around the equipment (the 4 Gauss line) of 4 m. This two characteristics eliminate these solutions as portable MRI machines in ERs or ambulances due to the safety constraints these locations impose. Therefore, the RF-MAFS magnet already provides a magnetic field for MRI experiments able to be deployed in ER and ambulances in an easier manner than the prototypes proposed by the state of the art.
It opens the MRI technology to a new point of view where the 'bigger the better' paradigm is not longer applicable. At the moment, the direction of the market for MRI devices makes the technologist and the funding agencies to invest time and money on stronger magnets for higher spatial resolution. However, the associate costs to these magnets are enormous. Facilities must be huge, the cryogenic maintenance is expensive and failure problems are almost impossible to fix without a intensive expend of money. A technology like the RF-MAFS magnet could change that. In that sense, the magnet developed during the last two years produces no radiation that needs a safety area, weights 15 kg and, as stated before, is able to produce usable MRI images in the near future shorting out the money needed to deploy this technology in medical environments.

Periodic Reporting for period 1 - RF-MAFS (Novel RF Driven MRI Magnet for Imaging Enhancement)

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