This article details a method for quantifying tissue sodium levels using sodium-MRI. The technique involves imaging the lower leg to assess sodium accumulation in muscle tissue.
Place the patient's lower leg within the radiofrequency coil of the magnetic resonance imaging or MRI machine.
The coil contains various sodium concentrations as standards to measure tissue sodium accumulation.
Initiate a sodium-MRI scan.
The coil detects fluctuations in the MR signal intensity emitted from the tissue, influenced by the distribution and concentration of sodium ions.
Obtain a total tissue sodium map displaying areas with varying color intensities corresponding to the sodium levels.
Compare these intensities with standard sodium concentrations, which aid in measuring total tissue sodium levels.
Bright colors indicate higher levels, while darker colors indicate lower levels.
Next, capture signals corresponding to the fat and water content of the tissue to generate images of the non-muscle regions.
Subtract non-muscle regions from the total tissue sodium map to generate a refined image and measure muscle tissue sodium content.
Begin by embedding calibration standard sodium chloride solutions in the MRI phantom holder of the coil.
Position the participant on the MRI table in a supine position.
For imaging of the calf at the mid-gastrocnemius muscle, place the phantom holder inside the radiofrequency coil. Position the left lower leg over the phantom holder. Secure the top half of the radiofrequency coil in place.
For sodium imaging, use the three-dimensional gradient-echo sequence as described in the text protocol.
Further, acquire fat- and water-weighted images of the tissue using the mDixon protocol keeping the scanning parameters consistent. Complete the multinuclear exam of the lower extremity.
After the completion of the scan, calibrate the measured sodium signal intensities to the standard sodium chloride concentrations on a per-voxel basis.
Prepare a quantitative sodium map of the tissue and interpolate it to match the matrix size of the fat- and water-weighted mDixon images.
Select each region of interest on the water-weighted mDixon image. Further, segment the outer and inner borders of the skin, total muscle, bone, blood vessels, and subcutaneous adipose tissue. Segment the skin region further into the posterior semi-perimeter of the skin.
Remove the voxels from the bone and blood vessels from the analyses.
Obtain accurate muscle tissue sodium quantification.
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