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Assessment of chemical shift gradient echo in-phase and opposed-phase sequences in Magnetic Resonance Imaging for brain metastasis diagnosis

Objectives: The purpose of this study was to evaluate ability of the in- and opposed-phase (IOP) sequences in Magnetic Resonance Imaging (MRI) in differentiation Brain Metastasis (BM) from High-Grade Glioma (HGG) using Regions of Interest (ROI) in tumors to determine a Signal Loss Ratio (SLR).

Methods: All consecutive patients with HGG or BM between April 2016 and October 2017 at Poitiers University Hospital were reviewed and images were analyzed prospectively. Patients had pre-operative multi-parametric imaging including the IOP sequences. An intra-tumoral signal loss measurement was performed for each patient to detect and quantify the lipids presence within the tumor. The results were correlated to anatomopathological diagnosis used as gold-standard.

Results: 65 patients (70 tumors) fulfilled the inclusion criteria. Even if there was a partial grading overlap, mean SLR were statistically higher for BM (32,53 ‰ +/- 8,35) than for grade IV gliomas (24,94 ‰ +/- 10,36) (p-value = 0,0075) and higher for grade IV gliomas than for grade III gliomas (14,54 ‰ +/- 9,40) (p-value = 0,0070), with a good intra-observer concordance. According to the Receiving Operator Characteristic (ROC) curve analysis, a first cutoff value of 30 ‰ for SLR generated the best combination of sensitivity (69,6%), specificity (74,5%), Positive Predictive Values (PPV) (57,14%) and Negative Predictive Values (NPV) (83,3%) (P < 0,05) to discriminate HGG from BM.

Conclusions: Our study demonstrates the clinical feasibility and potential role of the IOP sequences in MRI to discriminate BM from HGG, giving preliminary and promising results. Further studies are needed to confirm our results.

Keywords : Magnetic Resonance Imaging, Brain metastasis, Lipids, In and opposed phase imaging Chemical Shift Imaging, Signal Loss Ratio.