Correction to: 3D APT and NOE CEST-MRI of healthy volunteers and patients with non-enhancing glioma at 3 T

Objective Clinical application of chemical exchange saturation transfer (CEST) can be performed with investigation of amide proton transfer (APT) and nuclear Overhauser enhancement (NOE) effects. Here, we investigated APT- and NOE-weighted imaging based on advanced CEST metrics to map tumor heterogeneity of non-enhancing glioma at 3 T. Materials and methods APT- and NOE-weighted maps based on Lorentzian difference (LD) and inverse magnetization transfer ratio (MTR REX ) were acquired with a 3D snapshot CEST acquisition at 3 T. Saturation power was investigated first by varying B 1 (0.5–2 µT) in 5 healthy volunteers then by applying B 1 of 0.5 and 1.5 µT in 10 patients with non-enhancing glioma. Tissue contrast (TC) and contrast-to-noise ratios (CNR) were calculated between glioma and normal appearing white matter (NAWM) and grey matter, in APT- and NOE-weighted images. Volume percentages of the tumor showing hypo/hyperintensity (VP hypo/hyper,CEST ) in APT/NOE-weighted images were calculated for each patient. Results LD APT resulting from using a B 1 of 1.5 µT was found to provide significant positive TC tumor,NAWM and MTR REX NOE ( B 1 of 1.5 µT) provided significant negative TC tumor,NAWM in tissue differentiation. MTR REX -based NOE imaging under 1.5 µT provided significantly larger VP hypo,CEST than MTR REX APT under 1.5 µT. Conclusion This work showed that with a rapid CEST acquisition using a B 1 saturation power of 1.5 µT and covering the whole tumor, analysis of both LD APT and MTR REX NOE allows for observing tumor heterogeneity, which will be beneficial in future studies using CEST-MRI to improve imaging diagnostics for non-enhancing glioma.