A.A. Tarasova1, N.V. Anisimov2, O.S. Pavlova3, M.V. Gulyaev4, Yu.A. Pirogov5

1–5 Lomonosov Moscow State University (Moscow, Russia)

1 arina.tarasova99@mail.ru, 2 anisimovnv@mail.ru, 3 pavlova.olga@physics.msu.ru, 4 gulyaev@physics.msu.ru, 5 yupi937@gmail.com

The problems of magnetic resonance (MR) scanning at low signal-to-noise ratio, electromagnetic interference (EMI) and equipment imperfections are considered. Attention is paid to pulsed interference, as well as interference represented by continuous radiation, the frequency and amplitude of which vary chaotically over time. Manifestations of hardware and software imperfections leading to distortions of MR images were noted. These include, in particular, failures in digital signal processing (DSP) and direct current (DC) offset correction algorithms. These imperfections can be caused by various reasons - software errors, poor shielding, aging equipment, etc. Recently, articles have appeared that recommend detecting EMI based on the analysis of electromagnetic coupling between sources and spatially distributed receiving coils connected to a multi-channel receiver, and based on this information, eliminating EMI from MRI data. If such resources are not available when conducting MRI studies, then simple procedures described in this paper can be used to minimize or suppress interference. They involve planning the research time taking into account the dynamics of the interference environment, setting an extremely narrow receiver bandwidth, as well as editing k-space points distorted by interference and hardware factors. The issues of optimizing scanning parameters are considered, in particular those related to setting the matrix size and sampling frequency, as well as practical aspects of data processing, in particular the use of apodization in k-space. The methods described in the article were used for 23Na MRI of the human head on a clinical 0.5 T scanner, the adaptation of which for detecting sodium signals was reduced only to modification of the proprietary receiving coil. It has been shown that with standard processing of MR data, images are uninformative. But if the k-space data is edited before the Fourier transform, then the information content of sodium images becomes comparable to proton ones if scans are performed with the same spatial resolution and similar tissue contrast.

Tarasova A.A., Anisimov N.V., Pavlova O.S., Gulyaev M.V., Pirogov Yu.A. Magnetic resonance imaging at low signal-to-noise ratio, electromagnetic interferences and hardware imperfections. Electromagnetic waves and electronic systems. 2024. V. 29. № 3. P. 30−40. DOI: https://doi.org/10.18127/j15604128-202403-04

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