Whole Body Sodium MRI at 0.5 Tesla Using Surface Coil and Long Echo Time Sequence

Abstract

Experiments on sodium (²³Na) magnetic resonance imaging (MRI) of human organs, including the construction of whole body (WB) MRI, on a clinical 0.5-T scanner are described. The specificity of the research is their conduct in the presence of radio frequency (RF) interference, characterized by the frequency drift of the parasitic RF signal, which complicates its filtering. To solve this problem, the receiver bandwidth (BW) was set as narrow as possible, which, in turn, determined the low sampling rate and pulse sequence with relatively long echo time (TE)—12 ms, which is comparable to the transverse relaxation time of sodium nuclei. ²³Na MRI on a 0.5-T clinical scanner was achieved without significant modifications in the hardware—only 20-cm square-shaped frame coil was made as a transceiver probe head. Scanning was performed using gradient echo method with in-plane resolution of (6.6 × 6.6) mm² without slice selection. After processing the data in K-space, including exponential apodization, images were obtained in which human organs are represented with signal-to-noise ratio (SNR) up to several tens. The scans from nine individual segments of the human body in prone and supine positions were acquired to produce ²³Na WB MRI. The time for one body segment scan was 30 min. The results of the work can be used to assess the potential capabilities of scanners of this class and to compare them with the data obtained using more advanced tools to assess their effectiveness.