Dynamic Susceptibility Magnetic Resonance Research Articles

Association of dynamic susceptibility magnetic resonance imaging at initial tumor diagnosis with the prognosis of different molecular glioma subtypes

PurposeThe updated 2016 CNS World Health Organization classification differentiates three main groups of diffuse glioma according to their molecular characteristics: astrocytic tumors with and without isocitrate dehydrogenase (IDH) mutation and 1p/19q co-deleted oligodendrogliomas. The present study aimed to determine whether dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) is an independent prognostic marker within the molecular subgroups of diffuse glioma.MethodsFifty-six patients with treatment-naive gliomas and advanced preoperative MRI examination were assessed retrospectively. The mean and maximal normalized cerebral blood volume values from DSC-MRI within the tumors were measured. Optimal cutoff values for the 1-year progression-free survival (PFS) were defined, and Kaplan-Meier analyses were performed separately for the three glioma subgroups.ResultsIDH wild-type astrocytic tumors had a higher mean and maximal perfusion than IDH-mutant astrocytic tumors and oligodendrogliomas. Patients with IDH wild-type astrocytic tumors and a low mean or maximal perfusion had a significantly shorter PFS than patients of the same group with high perfusion (p = 0.0159/0.0112). Furthermore, they had a significantly higher risk for early progression (hazard ratio = 5.6/5.1). This finding was independent of the methylation status of O6-methylguanin-DNA-methyltransferase and variations of the therapy. Within the groups of IDH-mutant astrocytic tumors and oligodendrogliomas, the PFS of low and highly perfused tumors did not differ.ConclusionHigh perfusion upon initial diagnosis is not compellingly associated with worse short-term prognosis within the different molecular subgroups of diffuse glioma. Particularly, the overall highly perfused group of IDH wild-type astrocytic tumors contains tumors with low perfusion but unfavorable prognosis.

Magnetic resonance perfusion for differentiating low-grade from high-grade gliomas at first presentation.

Magnetic resonance perfusion for differentiating low-grade from high-grade gliomas at first presentation.

Bayesian Quantification of Contrast-Enhanced Ultrasound Images With Adaptive Inclusion of an Irreversible Component.

Contrast Enhanced Ultrasound (CEUS) is a sensitive imaging technique to assess tissue vascularity and it can be particularly useful in early detection and grading of arthritis. In a recent study we have shown that a Gamma-variate can accurately quantify synovial perfusion and it is flexible enough to describe many heterogeneous patterns. However, in some cases the heterogeneity of the kinetics can be such that even the Gamma model does not properly describe the curve, with a high number of outliers. In this work we apply to CEUS data the single compartment recirculation model (SCR) which takes explicitly into account the trapping of the microbubbles contrast agent by adding to the single Gamma-variate model its integral. The SCR model, originally proposed for dynamic-susceptibility magnetic resonance imaging, is solved here at pixel level within a Bayesian framework using Variational Bayes (VB). We also include the automatic relevant determination (ARD) algorithm to automatically infer the model complexity (SCR vs. Gamma model) from the data. We demonstrate that the inclusion of trapping best describes the CEUS patterns in 50% of the pixels, with the other 50% best fitted by a single Gamma. Such results highlight the necessity of the use ARD, to automatically exclude the irreversible component where not supported by the data. VB with ARD returns precise estimates in the majority of the kinetics (88% of total percentage of pixels) in a limited computational time (on average, 3.6 min per subject). Moreover, the impact of the additional trapping component has been evaluated for the differentiation of rheumatoid and non-rheumatoid patients, by means of a support vector machine classifier with backward feature selection. The results show that the trapping parameter is always present in the selected feature set, and improves the classification.

Magnetic resonance (MR) perfusion imaging to differentiate early progression from pseudoprogression following chemoradiotherapy for glioblastoma (GBM).

2009 Background: Patients with glioblastoma (GBM) treated with temozolomide and radiotherapy (RT) may experience early progressive disease (PD) or pseudoprogression (PsP) due to radiation effects, both of which appear as contrast-enhancing lesions on MRI. Currently, there is no reliable way to differentiate between PD and PsP, posing a common diagnostic and treatment dilemma since patients with PD have a poor prognosis, while PsP usually resolves without changes in therapy. Methods: We retrospectively identified 71 GBM patients with new or enlarging enhancing lesions on initial MRI following temozolomide and RT. In twenty patients, dynamic susceptibility (DSC) MR perfusion had been performed, including relative cerebral blood volume (rCBV), relative peak height (rPH) and peak signal recovery (PSR) of the enhancing lesions. Two independent reviewers unaware of results of DSC MR perfusion imaging assigned patients to either PD or PsP based on review of clinical data and follow up or results of biopsy of the enhancing lesions (if available). Two-sided Wilcoxon rank-sum tests were used to evaluate associations between DSC parameters and PD or PsP status. Results: The PsP group had significantly lower median rCBV compared to PD (1.5 vs 2.8, p=0.009) and rPH (1.3 vs 3.0, p<0.001), with higher PSR (1.0 vs 0.8, p=0.039). Receiver operator characteristic analysis revealed an optimal rCBV threshold of ≤1.80 to detect PsP with 100% sensitivity and 75% specificity (AUC=0.938). To maximize specificity, an rCBV threshold of ≤2.40 achieved 69% sensitivity and 100% specificity to detect PsP. Conclusions: DSC MR perfusion imaging of new or enlarging enhancing lesions immediately after completion of RT and temozolomide successfully identified patients with PsP versus those with PD, which has important implications for clinical treatment.