Sodium MRI in Pediatric Brain Tumors

Deblurring ²³Na-MRI with iterative Bowsher reconstruction. A, Native ²³Na-MRI of a healthy volunteer (A) can be significantly sharpened to B using 2-point T2 estimation and anatomic priors. Similarly, C and D demonstrate the benefit of IBR deblurring in a patient with glioma, allowing clearer intralesional resolution.

Dual-TE ²³Na-MRI in a pediatric patient with suppression of the elevated “free” sodium signal within vitreous fluid of the globe (crosshair). Note T2-based signal loss from TE = 0.5–5 ms. Also note, susceptibility artifacts in the left temporal lobe and nasal cavity, becoming especially pronounced on subtraction. (Same patient in Figs 3–6).

Diffuse midline glioma centered in the pons in a pediatric patient. T1 MPRAGE with tumor (solid arrow) centered in the pons extending into the left middle cerebellar peduncle. Subtraction of the 2 echo times demonstrates a focal region of elevated sodium in the tumor (arrow). Susceptibility artifact displays as elevated signal in the region of the right temporal bone (dashed arrow), which could potentially be misinterpreted as elevated tissue sodium concentration (same patient as above).

Thresholding the sodium concentrations in the pediatric patient above. Focal region of elevated sodium in the tumor (arrow). Thresholding allows precise depicting of the tumor.

Pediatric patients with diffuse midline glioma from above. The increased focus of sodium concentrations (arrow) in the tumor was acquired after radiation treatment; this region may represent the following: radioresistant region of the tumor (A) and region of tumor progression (B). Follow-up conventional MRI a further 2 months after radiation cessation demonstrates tumor progression in the region of the prior sodium elevation. This anecdote supports the hypothesis that elevated sodium signal represents an early biomarker of tumor progression/recurrence.