Glioblastoma (GBM) effects on quantitative MRI of contralateral normal appearing white matter

The objective was to investigate (with quantitative MRI) whether the normal appearing white matter (NAWM) of glioblastoma (GBM) patients on the contralateral side (cNAWM) was different from NAWM of healthy controls. Thirteen patients with newly diagnosed GBM and nine healthy age-matched controls were MRI-scanned with quantitative magnetization transfer (qMT), chemical exchange saturation transfer (CEST), and transverse relaxation time (T2)-mapping. MRI scans were performed after surgery and before chemo-radiation treatment. Comprehensive qMT, CEST, T2 data were acquired. A two-pool MT model was fit to qMT data in transient state, to calculate MT model parameters $$[{\text{R}},\,{{\text{T}}_{2{\text{b}}}},{\text{ R}}{{\text{M}}_{0{\text{b}}}}/{{\text{R}}_{\text{a}}},\,1/{{\text{R}}_{\text{a}}}{{\text{T}}_{2{\text{a}}}}]$$ . CEST signal was isolated by removing the contributions from the MT and direct water saturation, and CEST signal was calculated for Amide (CESTAmide), Amine (CESTAmine) and nuclear overhauser effect, NOE (CESTNOE). There was no difference between GBM patients and normal controls in the qMT properties of the macromolecular pool $$({\text{R}},\,{{\text{T}}_{2{\text{b}}}},{\text{ R}}{{\text{M}}_{0{\text{b}}}}/{{\text{R}}_{\text{a}}})$$ . However, their free water pool spectrum was different (1/RaT2a,patient = 28.1 ± 3.9, 1/RaT2a,control = 25.0 ± 1.1, p = 0.03). This difference could be attributed to the difference in their T2 time ( $$T_{{2,\;{\text{patient}}}}^{{{\text{obs}}}}$$ = 83 ± 4, $${T}_{{2,\;{\text{control}}}}^{{{\text{obs}}}}$$ = 88 ± 1, p = 0.004). CEST signals were statistically significantly different with the CESTAmide having the largest difference between the two cohorts (CESTAmide,patient = 2.8 ± 0.4, CESTAmide,control = 3.4 ± 0.5, p = 0.009). CEST in cNAWM of GBM patients was lower than healthy controls which could be caused by modified brain metabolism due to tumor cell infiltration. There was no difference in MT properties of the patients and controls, however, the differences in free water pool properties were mainly due to reduced T2 in cNAWM of the patients (resulting from structural changes and increased cellularity).