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Gabriel Hoffmann

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Open access Jul 2026

Arterial spin-labeling-based exchange time mapping for differentiation of high-grade glioma and brain metastases

Abstract Background To evaluate whether blood-brain barrier (BBB) mapping via arterial spin-labeling (ASL)-derived exchange time (Tex) can differentiate high-grade gliomas from brain metastases and to compare regional BBB alterations with dynamic susceptibility contrast (DSC)-derived leakage parameters (K2). Methods A total of 18 patients with therapy-naive cerebral masses (11 gliomas, 7 metastases) underwent multi-echo-ASL and DSC perfusion MRI. Tex maps were obtained using a validated extended two-compartment model. K2 maps were derived from single-echo DSC. Tex and absolute K2 (|K2|) were quantified in contrast-enhancing tumor (CET), peritumoral T2/FLAIR hyperintense region (PTR), gray matter (GM), and white matter (WM). Regional differences were assessed using Wilcoxon signed-rank and Mann-Whitney U tests. Receiver operating characteristic (ROC) analyses evaluated discrimination between gliomas and metastases. Results T ex was significantly lower in PTR of gliomas versus metastases (P = 0.046). In receiver operating characteristic analysis, Tex slightly outperformed |K2| alone (area under the curve [AUC] = 0.792, 95% confidence interval [CI] [0.535, 0.986] vs. AUC = 0.760, 95% CI [0.508, 0.959]), with further improvement upon combination (AUC = 0.833, 95% CI [0.577, 1.000]). In gliomas, Tex was significantly lower in CET than in GM and WM (both P < 0.01) and PTR showed significantly lower Tex than WM (p < .01). |K2| was significantly higher in CET than all other regions (all p < .01) but did not differ between PTR and GM/WM. Conclusion In this exploratory study, ASL-derived Tex suggests stronger BBB alterations in peritumoral tissue of high-grade gliomas compared with brain metastases. Adding |K2| further improved discrimination. This supports ASL-based BBB mapping as a complement to DSC leakage imaging. Validation in larger multicenter cohorts is warranted.

Philipp Raffler, Gabriel Hoffmann, M. Günther et al. · Neuro-Oncology Advances · 0 citations

Review Open access Aug 2026

Recent advances in arterial spin labeling MRI for imaging brain tumors.

Perfusion MRI plays an important role in brain tumor assessment, especially for tumor grading and differentiation of tumor progression from pseudoprogression. Arterial spin labeling (ASL) MRI is a non-invasive method for measuring cerebral blood flow (CBF) using blood water as an endogenous tracer, which has great clinical potential for brain tumor imaging and might help to lower the use of gadolinium-based contrast agents. In this review, we discuss recent advances of the ASL method with a special focus on brain tumors, including multi-time point ASL which not only allows more accurate CBF quantification, but also yields arterial transit time (ATT) maps. Another method to reduce dependency on ATT is velocity-selective ASL, for which labeling is directly performed in the imaging volume. By performing a physiological challenge, like a hypercapnia breathing challenge, the reactivity of the tumor's neovasculature can be determined. More recent advances in ASL allow probing the blood-brain barrier (BBB) integrity by measuring the rate of water transport across the BBB (BBB-ASL). By labeling only a single artery, selective ASL sequences can help to identify what part of the tumor is fed by which artery. In conclusion, we see the future potential of ASL MRI not only in replacing contrast agents for perfusion assessment but also in providing additional information to the MRI exam, such as BBB integrity or the architecture of the vascular feeders.

Gabriel Hoffmann, M. V. van Osch · MAGMA · 0 citations