An algorithm on the basis of standard MRI sequences and age predicted isocitrate dehydrogenase status in lower-grade gliomas without advanced computational methods. Background A readily implemented MRI biomarker for glioma genotyping is currently lacking. Purpose To evaluate clinically available MRI parameters for predicting isocitrate dehydrogenase (IDH) stat...

Preoperative clinical magnetic resonance imaging (MRI) protocols for gliomas, brain tumors with dismal outcomes due to their infiltrative properties, still rely on conventional structural MRI, which does not deliver information on tumor genotype and is limited in the delineation of diffuse gliomas. The GliMR COST action wants to raise awareness about the state of the art of advanced MRI techniques in gliomas and their possible clinical translation or lack thereof. This review describes current methods, limits, and applications of advanced MRI for the preoperative assessment of glioma, summarizing the level of clinical validation of different techniques. In this first part, we discuss dynamic susceptibility contrast and dynamic contrast‐enhanced MRI, arterial spin labeling, diffusion‐weighted MRI, vessel imaging, and magnetic resonance fingerprinting. The second part of this review addresses magnetic resonance spectroscopy, chemical exchange saturation transfer, susceptibility‐weighted imaging, MRI‐PET, MR elastography, and MR‐based radiomics applications.Evidence Level: 3Technical Efficacy: Stage 2

Preoperative clinical MRI protocols for gliomas, brain tumors with dismal outcomes due to their infiltrative properties, still rely on conventional structural MRI, which does not deliver information on tumor genotype and is limited in the delineation of diffuse gliomas. The GliMR COST action wants to raise awareness about the state of the art of advanced MRI techniques in gliomas and their possible clinical translation. This review describes current methods, limits, and applications of advanced MRI for the preoperative assessment of glioma, summarizing the level of clinical validation of different techniques. In this second part, we review magnetic resonance spectroscopy (MRS), chemical exchange saturation transfer (CEST), susceptibility‐weighted imaging (SWI), MRI‐PET, MR elastography (MRE), and MR‐based radiomics applications. The first part of this review addresses dynamic susceptibility contrast (DSC) and dynamic contrast‐enhanced (DCE) MRI, arterial spin labeling (ASL), diffusion‐weighted MRI, vessel imaging, and magnetic resonance fingerprinting (MRF).Evidence Level: 3.Technical Efficacy: Stage 2.

Purpose: Accurate glioma classification affects patient management and is challenging on non- or low-enhancing gliomas. This study investigated the clinical value of different chemical exchange saturation transfer (CEST) metrics for glioma classification and assessed the diagnostic effect of the presence of abundant fluid in glioma subpopulations. Methods: Forty-five treatment-naïve glioma patients with known isocitrate dehydrogenase (IDH) mutation and 1p/19q codeletion status received CEST MRI (B_1rms = 2μT, T_sat = 3.5 s) at 3 T. Magnetization transfer ratio asymmetry and CEST metrics (amides: offset range 3–4 ppm, amines: 1.5–2.5 ppm, amide/amine ratio) were calculated with two models: ‘asymmetry-based’ (AB) and ‘fluid-suppressed’ (FS). The presence of T2/FLAIR mismatch was noted. Results: IDH-wild type had higher amide/amine ratio than IDH-mutant_1p/19q^codel (p < 0.022). Amide/amine ratio and amine levels differentiated IDH-wild type from IDH-mutant (p < 0.0045) and from IDH-mutant_1p/19q^ret (p < 0.021). IDH-mutant_1p/19q^ret had higher amides and amines than IDH-mutant_1p/19q^codel (p < 0.035). IDH-mutant_1p/19q^ret with AB/FS mismatch had higher amines than IDH-mutant_1p/19q^ret without AB/FS mismatch ( < 0.016). In IDH-mutant_1p/19q^ret, the presence of AB/FS mismatch was closely related to the presence of T2/FLAIR mismatch (p = 0.014). Conclusions: CEST-derived biomarkers for amides, amines, and their ratio can help with histomolecular staging in gliomas without intense contrast enhancement. T2/FLAIR mismatch is reflected in the presence of AB/FS CEST mismatch. The AB/FS CEST mismatch identifies glioma subgroups that may have prognostic and clinical relevance.

537 Objectives Lung density changes during respiration which affects PET/CT quantification in the lung. We investigate the relation between density changes measured in CT, FDG concentration changes measured in PET and local volume changes obtained from the registration deformation field. Methods CINE CT and FDG PET data were acquired from patients suffering from lung cancer with solitary pulmonary nodules. These data were respiratory gated into 6 gates using the amplitude of the respiratory signal from an external device (RPM). Gated PET data were reconstructed with matched gated CT for the attenuation correction. After segmenting the lungs on the gated CT images, we performed an affine plus a non-rigid registration (NiftyReg with the Normalized Mutual Information objective function) of gated CT to a reference gate, which was chosen to correspond to an inhalation breathing state (i.e largest lung volume). From each registration, the local volume change (i.e Jacobian determinant) was measured from estimated deformation fields. ROIs were drawn on the lung away from edges, obvious artefacts and blood vessels. Regions where density changed less than 5% were excluded. Results The registration was visually judged to be of very good quality. The density and the PET tracer concentration were not conserved after registration. The average difference in density (PET concentration) between the registered image and the reference is 10% (15%), but this reduced to 5% (8%) after correcting for local volume change. The density and PET concentration are linearly related with a positive slope and a non-zero intercept (r² between 0.6 and 0.9). Conclusions We have shown that using the Jacobian underestimates the correction needed to preserve both density and PET concentration. The non-zero intercept in the density-activity relationship suggests a lack of local conservation of PET activity. In the future, we will investigate if this could be clarified by taking the PET tracer in blood into account. Research Support This work is supported by funding from GSK, Fibrosis DPU, GlaxoSmithKline R&D and EPSRC. This project is supported by researchers at the National Institute for Health Research, University College London Hospitals Biomedical Research Centre.

To investigate the relative somatotopic organization of the motor corticospinal/corticobulbar foot, hand, lip and tongue fascicles by combining fMRI with DTI and to examine the influence of subjacent intrinsic tumours on these fascicles. The study was approved by the local ethics committee. Seven male and three female volunteers (median age: 35 years) and one female and eight male patients with brain tumours (median age: 37 years) were scanned on a 1.5-T MRI scanner. fMRI data, analysed using SPM5, identified the motor task-driven fMRI grey matter activations of the hand, foot, lips and tongue as seed regions for probabilistic tractography. The relationship between the components of the CST was assessed and the distances between them were measured. A statistical comparison was performed comparing these distances in the group of healthy hemispheres with those of the group of non-affected hemispheres and healthy hemispheres. Hand fascicles were identified in all subjects (38/38, 100%), followed by foot (32/38, 84%), lip (31/38, 81%) and tongue fascicles (28/38, 74%). At superior levels, the hand fascicles were anterolateral to the foot fascicles in 77-93% of healthy hemispheres (HH), in 50-71% of non-affected patients' hemispheres (pH) and in 67-89% of affected PH. At inferior levels, the hand fascicles were either anteromedial in 46-45% of HH or anterior in 75% of non-affected PH and in 67-83% of affected PH. Tongue and lip fascicles overlapped in 25-45% of HH, in 10-20% of non-affected PH and in 15-25% of affected PH. No significant difference was found between the group of affected hemispheres and that of healthy and non-affected hemispheres. The somatotopy of the hand fascicles in relation to the foot fascicles was anterolateral in patients and volunteers at superior levels but anteromedial in volunteers and mostly anterior in patients at inferior levels. The lip and tongue fascicles generally overlapped. Intracranial tumours displaced the motor fascicles without affecting their relative somatotopy.