Inverse Z-spectrum analysis of chemical exchange saturation transfer MRI in orthotopic models of paediatric-type diffuse high grade glioma.

Motivation: The diffuse growth of paediatric-type diffuse high grade glioma (PDHGG) precludes complete delineation with conventional MRI. Goal(s): Molecular imaging with CEST may improve tumour detection. Approach: Three orthotopic models of PDHGG were assessed using inverse Z-spectrum analysis of CEST data. Results: Clear distinction between tumour and contralateral normal-appearing brain in ssMT and rNOE maps, which relate to macromolecular content, was observed in two well-defined tumour models when analysed using MTRRex and AREX. Similar CEST contrast was also apparent in a third more diffuse model, inconspicuous on T2w-MRI. This CEST approach can successfully stratify PDHGG tumours in vivo. Impact: Relaxation compensated CEST metrics provide novel biochemical contrasts in three orthotopic models of paediatric-type diffuse high grade glioma, enabling detection of diffuse disease, highlighting the clinical potential of CEST contrasts to stratifying tumours.