Quieter and faster
Anyone who has ever lain in an MRI machine knows that it is not only the cramped space, but above all the loud noise that causes patients stress. Determining which part of the body is sending back which signal usually requires a magnetic field whose strength varies with position – the gradient field. Switchable coils dynamically overlay this field on the strong permanent magnetic field, and this causes the loud noise. “The loudest noise during measurement is usually produced when the images are recorded,” says Prof. Matthias Günther, deputy director at Fraunhofer MEVIS. “We are working on using metamaterials to completely eliminate this source of noise.”

To this end, researchers involved in the project use a metamaterial array system. The signals from the various body regions strike different “pixels” in the array system, so it also serves to localize the signals. The first prototype is due to be completed in spring 2021, with the researchers planning to improve it in later steps. However, examinations will not be completely silent: there is currently nothing that can be done about the noise generated when the magnetic field is switched to obtain special image information, such as blood flow or diffusion effects, but it can be made much quieter than the noise produced by the imaging.
And if additional magnetic field switching for imaging can be eliminated, the process also becomes much faster. “According to theoretical calculations, our technology should enable us to complete scans up to one thousand times faster. Only when the experiments have been done will we know just how fast that will be in practice,” says Günther. Patients would then be able to enjoy much faster and quieter examinations.

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