Fluid attenuation in non-contrast-enhancing tumor (nCET): an MRI Marker for Isocitrate Dehydrogenase (IDH) mutation in Glioblastoma.

PURPOSE: The WHO 2016 update classifies glioblastomas (WHO grade IV) according to isocitrate dehydrogenase (IDH) gene mutation status. We aimed to determine MRI-based metrics for predicting IDH mutation in glioblastoma. METHODS: This retrospective study included glioblastoma cases (n = 199) with known IDH mutation status and pre-operative MRI (T1WI, T2WI, FLAIR, contrast-enhanced T1W1 at minimum). Two neuroradiologists determined the following MRI metrics: (1) primary lobe of involvement (frontal or non-frontal); (2) presence/absence of contrast-enhancement; (3) presence/absence of necrosis; (4) presence/absence of fluid attenuation in the non-contrast-enhancing tumor (nCET); (5) maximum width of peritumoral edema (cm); (6) presence/absence of multifocal disease. Inter-reader agreement was determined. After resolving discordant measurements, multivariate association between consensus MRI metrics/patient age and IDH mutation status was determined. RESULTS: Among 199 glioblastomas, 16 were IDH-mutant. Inter-reader agreement was calculated for contrast-enhancement (ĸ = 0.49 [- 0.11-1.00]), necrosis (ĸ = 0.55 [0.34-0.76]), fluid attenuation in nCET (ĸ = 0.83 [0.68-0.99]), multifocal disease (ĸ = 0.55 [0.39-0.70]), and primary lobe (ĸ = 0.85 [0.80-0.91]). Mean difference for peritumoral edema width between readers was 0.3 cm [0.2-0.5], p < 0.001. Multivariate analysis uncovered significant associations between IDH-mutation and fluid attenuation in nCET (OR 82.9 [19.22, ∞], p < 0.001), younger age (OR 0.93 [0.86, 0.98], p = 0.009), frontal lobe location (OR 11.08 [1.14, 352.97], p = 0.037), and less peritumoral edema (OR 0.15 [0, 0.65], p = 0.044). CONCLUSIONS: Conventional MRI metrics and patient age predict IDH-mutation status in glioblastoma. Among MRI markers, fluid attenuation in nCET represents a novel marker with high inter-reader agreement that is strongly associated with Glioblastoma, IDH-mutant.

FDG PET/MRI Coregistration Helps Predict Response to Gamma Knife Radiosurgery in Patients With Brain Metastases.

OBJECTIVE: The purpose of this study was to determine whether relative standardized uptake value (SUV) measurements at FDG PET/MRI coregistration are predictive of local tumor control in patients with brain metastases treated with stereotactic radiosurgery (SRS). MATERIALS AND METHODS: A retrospective review was conducted of the images and clinical characteristics of a cohort of patients with brain metastases from non-CNS neoplasms treated with gamma knife radiosurgery (GKRS) who underwent posttherapy FDG PET because of MRI findings concerning for progression. The PET and contrast-enhanced MR images were fused. Relative SUV measurements were calculated from ROIs placed in the area of highest FDG uptake within the enhancing lesion and in the contralateral normal-appearing white matter. Relative SUV was defined as the ratio of maximum SUV in the tumor to maximum SUV in healthy white matter. Two independent readers evaluated response to GKRS using serial posttherapy MRI performed at least 3 months after GKRS completion. The relation between relative SUV and local tumor progression was evaluated with respect to treatment effect. RESULTS: Eighty-five patients (48 [56.5%] women, 37 [43.5%] men; mean age at diagnosis, 60.5 ± 11.3 years) met the inclusion criteria. Thirty-three (38.8%) lesions progressed after SRS. There was a significant association between relative SUV and local tumor control (p = 0.035). Relative SUV provided a diagnostic ROC AUC of 0.67 (95% CI, 0.55-0.79). CONCLUSION: Quantitative relative SUV at posttherapy FDG PET serves as a biomarker of response to SRS in patients with brain metastases in cases in which lesion growth is identified at follow-up MRI. This prognostic data may affect management, supporting the need for further therapeutic actions for selected patients.

MRI patterns of global hypoxic-ischemic injury in adults.

BACKGROUND AND PURPOSE: To assess MRI patterns and associated clinical outcome in adults with global hypoxic-ischemic injury. MATERIALS AND METHODS: In order to identify the patients with evidence of global hypoxic-ischemic injury, we retrospectively searched our radiology information system for reports of brain MRI studies from 01/01/2004 to 12/31/2010, containing the keywords - "hypoxia", "hypoxic", "anoxia" and "anoxic". A board certified neuroradiologist visually inspected the corresponding MR images for the presence, location and extent (focal versus diffuse) of ischemic findings. Clinical data for these patients was collected from the electronic medical records, including mechanism of the hypoxic-ischemic injury, and clinical outcome was measured using modified Rankin Scale (mRS). RESULTS: Review of radiology reports identified 151 cases, of which 64 patients remained after exclusion of normal studies ("no hypoxia" in the report), pediatric patients and patients with remote perinatal hypoxia. Five patients had relatively favorable clinical outcome (mRS of 1 to 3) and 59 had poor outcome (mRS of 4 to 6). Patterns associated with relatively favorable clinical outcome were: a) watershed pattern and b) basal ganglia without cortical involvement. Patterns associated with poor clinical outcome were: a) diffuse cortical and deep grey matter pattern, with and without perirolandic sparing; (b) medial occipital with perirolandic involvement; c) precentral gyrus involvement; d) diffuse white matter involvement; e) brainstem involvement; f) cerebellar involvement and g) hippocampal involvement. CONCLUSION: The vast majority of patients with MRI patterns of hypoxic-anoxic injury have a poor clinical outcome, independently of the observed pattern, with the only relative exception being the watershed pattern and the basal ganglia pattern without cortical involvement.