Prognostic value of choline and creatine in WHO grade II gliomas

2-Hydroxyglutarate as an MR spectroscopic predictor of an IDH mutation in gliomas

The mutated enzyme isocitrate dehydrogenase (IDH) 1 and 2 has been detected in various tumor entities such as gliomas and can convert α-ketoglutarate into the oncometabolite 2-hydroxyglutarate (2-HG). This neuro-oncologically significant metabolic product can be detected by MR spectroscopy and is therefore suitable for noninvasive glioma classification and therapy monitoring.This paper provides an up-to-date overview of the methodology and relevance of 1H-MR spectroscopy (MRS) in the oncological primary and follow-up diagnosis of gliomas. The possibilities and limitations of this MR spectroscopic examination are evaluated on the basis of the available literature.By detecting 2-HG, MRS can in principle offer a noninvasive alternative to immunohistological analysis thus avoiding surgical intervention in some cases. However, in addition to an adapted and optimized examination protocol, the individual measurement conditions in the examination region are of decisive importance. Due to the inherently small signal of 2-HG, unfavorable measurement conditions can influence the reliability of detection. · MR spectroscopy enables the non-invasive detection of 2-hydroxyglutarate.. · The measurement of this metabolite allows the detection of an IDH mutation in gliomas.. · The choice of MR examination method is particularly important.. · Detection reliability is influenced by glioma size, necrotic tissue and the existing measurement conditions.. · Bauer J, Raum HN, Kugel H et al. 2-Hydroxyglutarate as an MR spectroscopic predictor of an IDH mutation in gliomas. Fortschr Röntgenstr 2024; DOI 10.1055/a-2285-4923.

Using Single-Voxel Magnetic Resonance Spectroscopy Data Acquired at 1.5T to Classify Multivoxel Data at 3T: A Proof-of-Concept Study

In vivo magnetic resonance spectroscopy (MRS) has two modalities, single-voxel (SV) and multivoxel (MV), in which one or more contiguous grids of SVs are acquired.

PURPOSE

To test whether MV grids can be classified with models trained with SV.

METHODS

Retrospective study. Training dataset: Multicenter multiformat SV INTERPRET, 1.5T. Testing dataset: MV eTumour, 3T. Two classification tasks were completed: 3-class (meningioma vs. aggressive vs. normal) and 4-class (meningioma vs. low-grade glioma vs. aggressive vs. normal). Five different methods were tested for feature selection. The classification was implemented using linear discriminant analysis (LDA), random forest, and support vector machines. The evaluation was completed with balanced error rate (BER) and area under the curve (AUC) on both sets. The accuracy in class prediction was calculated by developing a solid tumor index (STI) and segmentation accuracy with the Dice score.

RESULTS

The best method was sequential forward feature selection combined with LDA, with AUCs = 0.95 (meningioma), 0.89 (aggressive), 0.82 (low-grade glioma), and 0.82 (normal). STI was 66% (4-class task) and 71% (3-class task) because two cases failed completely and two more had suboptimal STI as defined by us.

DISCUSSION

The reasons for failure in the classification of the MV test set were related to the presence of artifacts.

Advances in molecular and imaging biomarkers in lower-grade gliomas

INTRODUCTION

Lower-grade (grade 2-3) gliomas (LGGs) constitutes a group of primary brain tumors with variable clinical behaviors and treatment responses. Recent advancements in molecular biology have redefined their classification, and novel imaging modalities emerged for the noninvasive diagnosis and follow-up.

AREAS COVERED

This review comprehensively analyses the current knowledge on molecular and imaging biomarkers in LGGs. Key molecular alterations, such as IDH mutations and 1p/19q codeletion, are discussed for their prognostic and predictive implications in guiding treatment decisions. Moreover, the authors explore theranostic biomarkers for the potential of tailored therapies. Additionally, they also describe the utility of advanced imaging modalities, including widely available techniques, as dynamic susceptibility contrast perfusion-weighted imaging and less validated, emerging approaches, for the noninvasive LGGs characterization and follow-up.

EXPERT OPINION

The integration of molecular markers enhanced the stratification of LGGs, leading to the new concept of integrated histomolecular classification. While the IDH mutation is an established key prognostic and predictive marker, recent results from IDH inhibitors trials showed its potential value as a theranostic marker. In this setting, advanced MRI techniques such as 2-D-hydroxyglutarate spectroscopy are very promising for the noninvasive diagnosis and monitoring of LGGs. This progress offers exciting prospects for personalized medicine and improved treatment outcomes in LGGs.

White Matter Metabolite Ratios Predict Cognitive Outcome in Pediatric Traumatic Brain Injury

The prognostic ability of global white matter and gray matter metabolite ratios following pediatric traumatic brain injury (TBI) and their relationship to 12-month neuropsychological assessments of intelligence quotient (IQ), attention, and memory is presented. Three-dimensional proton magnetic resonance spectroscopic imaging (MRSI) in pediatric subjects with complicated mild (cMild), moderate, and severe TBI was acquired acutely (6-18 days) and 12 months post-injury and compared to age-matched typically developing adolescents. A global linear regression model, co-registering MRSI metabolite maps with 3D high-resolution magnetic resonance images, was used to identify longitudinal white matter and gray matter metabolite ratio changes. Acutely, gray matter NAA/Cr, white matter NAA/Cr, and white matter NAA/Cho ratios were significantly lower in TBI groups compared to controls. Gray matter NAA/Cho was reduced only in the severe TBI group. At 12 months, all metabolite ratios normalized to control levels in each of the TBI groups. Acute gray matter and white matter NAA ratios were significantly correlated to 12-month assessments of IQ, attention, and memory. These findings suggest that whole brain gray matter and white matter metabolite ratios reflect longitudinal changes in neuronal metabolism following TBI, which can be used to predict neuropsychological outcomes in pediatric subjects.

In vivo brain MR spectroscopy in gliomas: clinical and pre-clinical chances

Purpose

Gliomas, the most common primary brain tumours, have recently been re-classified incorporating molecular aspects with important clinical, prognostic, and predictive implications. Concurrently, the reprogramming of metabolism, altering intracellular and extracellular metabolites affecting gene expression, differentiation, and the tumour microenvironment, is increasingly being studied, and alterations in metabolic pathways are becoming hallmarks of cancer. Magnetic resonance spectroscopy (MRS) is a complementary, non-invasive technique capable of quantifying multiple metabolites. The aim of this review focuses on the methodology and analysis techniques in proton MRS (1H MRS), including a brief look at X-nuclei MRS, and on its perspectives for diagnostic and prognostic biomarkers in gliomas in both clinical practice and preclinical research.

Methods

PubMed literature research was performed cross-linking the following key words: glioma, MRS, brain, in-vivo, human, animal model, clinical, pre-clinical, techniques, sequences, 1H, X-nuclei, Artificial Intelligence (AI), hyperpolarization.

Results

We selected clinical works (n = 51), preclinical studies (n = 35) and AI MRS application papers (n = 15) published within the last two decades. The methodological papers (n = 62) were taken into account since the technique first description.

Conclusions

Given the development of treatments targeting specific cancer metabolic pathways, MRS could play a key role in allowing non-invasive assessment for patient diagnosis and stratification, predicting and monitoring treatment responses and prognosis. The characterization of gliomas through MRS will benefit of a wide synergy among scientists and clinicians of different specialties within the context of new translational competences. Head coils, MRI hardware and post-processing analysis progress, advances in research, experts’ consensus recommendations and specific professionalizing programs will make the technique increasingly trustworthy, responsive, accessible.

Systematic review-Time to malignant transformation in low-grade gliomas: Predicting a catastrophic event with clinical, neuroimaging, and molecular markers

Background

Despite an initially indolent course, all WHO grade II, LGGs inevitably transform to malignant, WHO grades III and IV, without current curative options. Malignant transformation (MT) remains unpredictable with limited prognostic markers to steer timing of interventions. The aim of this study was to review and assign predictive value to specific clinical, molecular, and radiological markers impacting MT, thereby justifying timely therapeutic interventions.

Methods

Searches of MEDLINE, Embase, and Cochrane databases were conducted from inception to April 28, 2021 and outputs were analysed in accordance with PRISMA protocol.

Results

From an initial 5,032 articles, 33 articles were included, totalling 5672 patients. Forty-three prognostic factors were registered to significantly impact MT. These were categorised as 7 clinical; 14 neuroimaging; 8 biological/molecular; 3 volumetric; 5 topological; 3 histological; and 3 treatment-related. Following analysis, 10 factors were highlighted: the pre-operative prognosticators were 1. presentation with epileptic seizures; 2. VDE > 8 mm/y; 3. VDE > 4 mm/y; 4. rCBV > 1.75; 5. PTV ≥ 5 cm (65 ml); 6. PTV ≥ 100 ml; and 7. cortical involvement. The post-operative prognosticators were: (1) IDH-wt, (2) TP53 mutation, and (3) temozolomide monotherapy.

Conclusions

The management of LGGs remains controversial, as conservative and invasive treatment may be associated with MT and impaired quality of life, respectively. Our review indicates that MT can be predicted by specific metrics in VDE, PTV, and rCBV, alongside cortical involvement. Additionally, patients with IDH-wt tumours TP53 mutations, or receiving TMZ monotherapy are more likely to undergo MT. Our data may form the basis of a predictive scoring system.

MRS as an Aid to Diagnose Malignant Transformation in Low-Grade Gliomas with Increasing Contrast Enhancement

BACKGROUND AND PURPOSE

Increased contrast enhancement has been used as a marker of malignant transformation in low-grade gliomas. This marker has been found to have limited accuracy because many low-grade gliomas with increased contrast enhancement remain grade II. We aimed to investigate whether MR spectroscopy can contribute to the diagnosis of malignant transformation in low-grade gliomas with increased contrast enhancement.

MATERIALS AND METHODS

Patients with low-grade gliomas who had contemporaneous MR spectroscopy and histopathology for tumor regions with increased contrast enhancement between 2004 and 2015 were retrospectively reviewed. Clinical data collected were sex and age, Karnofsky Performance Scale, histologic subtypes, isocitrate dehydrogenase 1 mutation status, disease duration, adjuvant therapy, and post-radiation therapy duration. Imaging data collected were contrast-enhancement size, whole-tumor size, MR spectroscopy metabolite ratios, and tumor grades of regions with increased contrast enhancement. Diagnostic values of these factors on malignant transformation of low-grade gliomas were statistically analyzed.

RESULTS

A total of 86 patients with 96 MR spectroscopy studies were included. Tumor grades associated with increased contrast enhancement were grade II (n = 42), grade III (n = 27), and grade IV (n = 27). On multivariate analysis, the NAA/Cho ratio was the only significant factor (P < .001; OR, 7.1; 95% CI, 3.2-16.1) diagnostic of malignant transformation. With 0.222 as the cutoff value, the sensitivity, specificity, and accuracy of NAA/Cho for diagnosing malignant transformation were 94.4%, 83.3%, and 89.6%, respectively.

CONCLUSIONS

MR spectroscopy complements conventional MR imaging in the diagnosis of malignant transformation in a subgroup of low-grade gliomas with increased contrast enhancement.

The biological and clinical basis for early referral of low grade glioma patients to a surgical neuro-oncologist

The discovery of IDH1/2 (isocitrate dehydrogenase) mutation in large scale, genomewide mutational analyses of gliomas has led to profound developments in understanding tumourigenesis, and restructuring of the classification of both high and low grade gliomas. Owing to this progress made in the recognition of molecular markers which predict tumour behavior and treatment response, the increasing importance of adjuvant treatments such as chemo- and radiotherapy, and the tremendous advances in surgical technique and intraoperative monitoring which have facilitated superior extents of resection whilst preserving neurological functioning and quality of life, contemporary management of low grade glioma (LGG) has switched from a passive, observant approach to a more active, interventional one. Furthermore, this has implications for the manner in which patients with incidentally discovered and/or asymptomatic LGG are managed, and this review of the biological behaviour of LGG, as well as its clinical investigation and management, should act as a timely reminder to all clinicians of the importance of referring LGG patients early to a surgical neuro-oncologist who is not only familiar and acquainted with the vagaries of this disease process, but who, in addition, is devoted to delivering care to these patients with the support of a multi-disciplinary clinical decision-making unit, comprising medical neuro-oncologists, radiation oncologists and allied health professionals.

Prediction of IDH Status Through MRI Features and Enlightened Reflection on the Delineation of Target Volume in Low-Grade Gliomas

Isocitrate dehydrogenase mutational status defines distinct biologic behavior and clinical outcomes in low-grade gliomas. We sought to determine magnetic resonance imaging characteristics associated with isocitrate dehydrogenase mutational status to evaluate the predictive roles of magnetic resonance imaging features in isocitrate dehydrogenase mutational status and therefore their potential impact on the determination of clinical target volume in radiotherapy. Forty-eight isocitrate dehydrogenase-mutant and 28 isocitrate dehydrogenase–wild-type low-grade gliomas were studied. Isocitrate dehydrogenase mutation was related to more frequency of cortical involvement compared to isocitrate dehydrogenase–wild-type group (34/46 vs 6/24, P = .0001). Peritumoral edema was less frequent in isocitrate dehydrogenase–mutant tumors (32.6% vs 58.3% for isocitrate dehydrogenase–wild-type tumors, P = .0381). Isocitrate dehydrogenase–wild-type tumors were more likely to have a nondefinable border, while isocitrate dehydrogenase–mutant tumors had well-defined borders (66.7% vs 39.1%, P = .0287). Only 8 (17.4%) of 46 of the isocitrate dehydrogenase–mutant tumors demonstrated marked enhancement, while this was 66.7% in isocitrate–wild-type tumors (P < .0001). Choline–creatinine ratio for isocitrate dehydrogenase–wild-type tumors was significantly higher than that for isocitrate dehydrogenase–mutant tumors. In conclusion, frontal location, well-defined border, cortical involvement, less peritumoral edema, lack of enhancement, and low choline–creatinine ratio were predictive for the definition of isocitrate dehydrogenase–mutant low-grade gliomas. Magnetic resonance imaging can provide an advantage in the detection of isocitrate dehydrogenase status indirectly and indicate the need to explore new design for treatment planning in gliomas. Choline–creatinine ratio in magnetic resonance spectroscopy could be a potential more reasonable reference for the new design of delineation of target volume in low-grade gliomas.

Assessment of Overall Survival in Glioma Patients as Predicted by Metabolomic Criteria

Objective: We assess the efficacy of the metabolomic profile from glioma biopsies in providing estimates of postsurgical Overall Survival in glioma patients.

Methods: Tumor biopsies from 46 patients bearing gliomas, obtained neurosurgically in the period 1992–1998, were analyzed by high resolution ¹H magnetic resonance spectroscopy (HR- ¹H MRS), following retrospectively individual postsurgical Overall Survival up to 720 weeks.

Results: The Overall Survival profile could be resolved in three groups; Short (shorter than 52 weeks, n = 19), Intermediate (between 53 and 364 weeks, n = 19) or Long (longer than 365 weeks, n = 8), respectively. Classical histopathological analysis assigned WHO grades II–IV to every biopsy but notably, some patients with low grade glioma depicted unexpectedly Short Overall Survival, while some patients with high grade glioma, presented unpredictably Long Overall Survival. To explore the reasons underlying these different responses, we analyzed HR-¹H MRS spectra from acid extracts of the same biopsies, to characterize the metabolite patterns associated to OS predictions. Poor prognosis was found in biopsies with higher contents of alanine, acetate, glutamate, total choline, phosphorylcholine, and glycine, while more favorable prognosis was achieved in biopsies with larger contents of total creatine, glycerol-phosphorylcholine, and myo-inositol. We then implemented a multivariate analysis to identify hierarchically the influence of metabolomic biomarkers on OS predictions, using a Classification Regression Tree (CRT) approach. The CRT based in metabolomic biomarkers grew up to three branches and split into eight nodes, predicting correctly the outcome of 94.7% of the patients in the Short Overall Survival group, 78.9% of the patients in the Intermediate Overall Survival group, and 75% of the patients in the Long Overall Survival group, respectively.

Conclusion: Present results indicate that metabolic profiling by HR-¹H MRS improves the Overall Survival predictions derived exclusively from classical histopathological gradings, thus favoring more precise therapeutic decisions.

Pre- and post-surgery MRSI predictive value in adult oligodendroglioma prognosis

PURPOSE

The aim of this study was to study the relationship between MRSI, before and after surgery, and patient survival. The accuracy of pre-operative MRSI in differentiating low- from high-grade oligodendrogliomas (ODGs) was also studied.

METHODS

Two hundred patients with ODG were retrospectively included in this study between 2000 and 2016. All patients underwent MRSI before any treatment or biopsy and/or after surgery for an intra-axial brain tumour. The R software was used for statistical data analysis. p < 0.05 was considered statistically significant. Kaplan-Meier curves were calculated for patients with low-grade ODG and high-grade ODG pre- and post-operatively, to study survival (overall survival, OS). The best threshold of each MRSI metabolite ratio was obtained using receiver operating characteristic curves (ROCs).

RESULTS

One hundred patients underwent pre-operative MRSI and 170 post-operative MRSI. N-acetylaspartate (NAA), lactate (Lac), choline (Cho) and creatine (Cr) were measured. Kapan-Meier curves showed that survival was poorer for a nCho/Cr > 3.02 in the pre-operative and nCho/Cr > 2.04, Lac/Cr > 0.743 and nCho/NAA > 3.63 in the post-operative period. Post-operative MRSI predicts survival better than pre-operative MRSI. nCho/Cr and Lac/Cr distinguished low- from high-grade ODG with a good positive predictive value.

CONCLUSION

MRSI is associated with survival. It is a non-invasive tool which completes histopathology and can predict patients' prognosis, thus improving patient management.

Surgical Management of Incidental Gliomas

Detailed brain imaging studies discover gliomas incidentally before clinical symptoms or signs show. These tumors represent an early stage in the natural history of gliomas. Left untreated, they are likely to progress to a symptomatic stage and transform to malignant gliomas. A greater extent of resection delays the onset of malignant transformation and prolongs patient survival. Because incidental gliomas are typically smaller and less likely to be in eloquent brain locations, there is a strong case for early surgical intervention to maximize resection and improve outcomes. This article discusses developments in the surgical management of low-grade gliomas.

In Vivo 1H Magnetic Resonance Spectroscopy

In vivo Magnetic Resonance Spectroscopy (MRS) allows the non-invasive detection and quantification of a number of metabolites from localized volumes within a living organism. MRS localization techniques can be divided into two main groups, single voxel and multi-voxel. Single voxel techniques provide the metabolic profile from a specific small volume, whereas multi-voxel techniques are used to obtain the spatial distribution of metabolites throughout a large volume subdivided into small contiguous voxels. This chapter describes standard protocols for the acquisition and processing of in vivo single voxel¹H MRS data from the rodent brain.

Brain microstructure by multi-modal MRI: Is the whole greater than the sum of its parts?

The MRI signal is dependent upon a number of sub-voxel properties of tissue, which makes it potentially able to detect changes occurring at a scale much smaller than the image resolution. This "microstructural imaging" has become one of the main branches of quantitative MRI. Despite the exciting promise of unique insight beyond the resolution of the acquired images, its widespread application is limited by the relatively modest ability of each microstructural imaging technique to distinguish between differing microscopic substrates. This is mainly due to the fact that MRI provides a very indirect measure of the tissue properties in which we are interested. A strategy to overcome this limitation lies in the combination of more than one technique, to exploit the relative contributions of differing physiological and pathological substrates to selected MRI contrasts. This forms the basis of multi-modal MRI, a broad concept that refers to many different ways of effectively combining information from more than one MRI contrast. This paper will review a range of methods that have been proposed to maximise the output of this combination, primarily falling into one of two approaches. The first one relies on data-driven methods, exploiting multivariate analysis tools able to capture overlapping and complementary information. The second approach, which we call "model-driven", aims at combining parameters extracted by existing biophysical or signal models to obtain new parameters, which are believed to be more accurate or more specific than the original ones. This paper will attempt to provide an overview of the advantages and limitations of these two philosophies.

Interrogating Metabolism in Brain Cancer

This article reviews existing and emerging techniques of interrogating metabolism in brain cancer from well-established proton magnetic resonance spectroscopy to the promising hyperpolarized metabolic imaging and chemical exchange saturation transfer and emerging techniques of imaging inflammation. Some of these techniques are at an early stage of development and clinical trials are in progress in patients to establish the clinical efficacy. It is likely that in vivo metabolomics and metabolic imaging is the next frontier in brain cancer diagnosis and assessing therapeutic efficacy; with the combined knowledge of genomics and proteomics a complete understanding of tumorigenesis in brain might be achieved.

Adult Brain Tumors: Clinical Applications of Magnetic Resonance Spectroscopy

Proton magnetic resonance spectroscopy (H-MRS) may be helpful in suggesting tumor histology and tumor grade and may better define tumor extension and the ideal site for biopsy compared with conventional magnetic resonance (MR) imaging. A multifunctional approach with diffusion-weighted imaging, perfusion-weighted imaging, and permeability maps, along with H-MRS, may enhance the accuracy of the diagnosis and characterization of brain tumors and estimation of therapeutic response. Integration of advanced imaging techniques with conventional MR imaging and the clinical history help to improve the accuracy, sensitivity, and specificity in differentiating tumors and nonneoplastic lesions.

Advances in neuro-oncology imaging

Despite the fact that MRI has evolved to become the standard method for diagnosis and monitoring of patients with brain tumours, conventional MRI sequences have two key limitations: the inability to show the full extent of the tumour and the inability to differentiate neoplastic tissue from nonspecific, treatment-related changes after surgery, radiotherapy, chemotherapy or immunotherapy. In the past decade, PET involving the use of radiolabelled amino acids has developed into an important diagnostic tool to overcome some of the shortcomings of conventional MRI. The Response Assessment in Neuro-Oncology working group - an international effort to develop new standardized response criteria for clinical trials in brain tumours - has recommended the additional use of amino acid PET imaging for brain tumour management. Concurrently, a number of advanced MRI techniques such as magnetic resonance spectroscopic imaging and perfusion weighted imaging are under clinical evaluation to target the same diagnostic problems. This Review summarizes the clinical role of amino acid PET in relation to advanced MRI techniques for differential diagnosis of brain tumours; delineation of tumour extent for treatment planning and biopsy guidance; post-treatment differentiation between tumour progression or recurrence versus treatment-related changes; and monitoring response to therapy. An outlook for future developments in PET and MRI techniques is also presented.

Quantitative multi-modal MR imaging as a non-invasive prognostic tool for patients with recurrent low-grade glioma

Low-grade gliomas can vary widely in disease course and therefore patient outcome. While current characterization relies on both histological and molecular analysis of tissue resected during surgery, there remains high variability within glioma subtypes in terms of response to treatment and outcome. In this study we hypothesized that parameters obtained from magnetic resonance data would be associated with progression-free survival for patients with recurrent low-grade glioma. The values considered were derived from the analysis of anatomic imaging, diffusion weighted imaging, and ¹H magnetic resonance spectroscopic imaging data. Metrics obtained from diffusion and spectroscopic imaging presented strong prognostic capability within the entire population as well as when restricted to astrocytomas, but demonstrated more limited efficacy in the oligodendrogliomas. The results indicate that multi-parametric imaging data may be applied as a non-invasive means of assessing prognosis and may contribute to developing personalized treatment plans for patients with recurrent low-grade glioma.

COMPARISON BETWEEN PROTON MAGNETIC RESONANCE SPECTROSCOPY FINDINGS IN DOGS WITH TICK-BORNE ENCEPHALITIS AND CLINICALLY NORMAL DOGS

In vivo diagnosis of tick-borne encephalitis is difficult due to high seroprevalence and rapid viral clearance, limiting detection of antibodies in blood and cerebrospinal fluid. Magnetic resonance imaging (MRI) characteristics of tick-borne encephalitis have been reported, however MRI studies can also be negative despite the presence of neurologic signs. Magnetic resonance spectroscopy (¹ H MRS) is an imaging method that provides additional information about the metabolic characteristics of brain tissues. The purpose of this retrospective cross-sectional study was to describe brain metabolites using short echo time single-voxel ¹ H MRS in dogs with confirmed tick-borne encephalitis and compare them with healthy dogs. Inclusion criteria for the affected dogs were neurological symptoms suggestive of tick-borne encephalitis, previous endemic stay and tick-bite, diagnostic quality brain MRI and ¹ H MRS studies, and positive antibody titers or confirmation of tick-borne encephalitis with necropsy. Control dogs were 10, clinically normal beagles that had been used in a previous study. A total of six affected dogs met inclusion criteria. All dogs affected with tick-borne encephalitis had ¹ H MRS metabolite concentration alterations versus control dogs. These changes included mild to moderate decreases in N-acetyl aspartate and creatine peaks, and mild increases in glutamate/glutamine peaks. No lactate or lipid signal was detected in any dog. Myoinositol and choline signals did not differ between affected and control dogs. In conclusion, findings supported the use of ¹ H MRS as an adjunctive imaging method for dogs with suspected tick-borne encephalitis and inconclusive conventional MRI findings.

Basic Principles and Clinical Applications of Magnetic Resonance Spectroscopy in Neuroradiology

Magnetic resonance spectroscopy is a powerful tool to assist daily clinical diagnostics. This review is intended to give an overview on basic principles of the technology, discuss some of its technical aspects, and present typical applications in daily clinical routine in neuroradiology.

The role of imaging in the management of adults with diffuse low grade glioma: A systematic review and evidence-based clinical practice guideline

QUESTION

What is the optimal imaging technique to be used in the diagnosis of a suspected low grade glioma, specifically: which anatomic imaging sequences are critical for most accurately identifying or diagnosing a low grade glioma (LGG) and do non-anatomic imaging methods and/or sequences add to the diagnostic specificity of suspected low grade gliomas?

TARGET POPULATION

These recommendations apply to adults with a newly diagnosed lesion with a suspected or histopathologically proven LGG.

RECOMMENDATION

LEVEL II

In patients with a suspected brain tumor, the minimum magnetic resonance imaging (MRI) exam should be an anatomic exam with both T2 weighted and pre- and post-gadolinium contrast enhanced T1 weighted imaging. CRITICAL IMAGING FOR THE IDENTIFICATION AND DIAGNOSIS OF LOW GRADE GLIOMA:

LEVEL II

In patients with a suspected brain tumor, anatomic imaging sequences should include T1 and T2 weighted and Fluid Attenuation Inversion Recovery (FLAIR) MR sequences and will include T1 weighted imaging after the administration of gadolinium based contrast. Computed tomography (CT) can provide additional information regarding calcification or hemorrhage, which may narrow the differential diagnosis. At a minimum, these anatomic sequences can help identify a lesion as well as its location, and potential for surgical intervention. IMPROVEMENT OF DIAGNOSTIC SPECIFICITY WITH THE ADDITION OF NON-ANATOMIC (PHYSIOLOGIC AND ADVANCED IMAGING) TO ANATOMIC IMAGING:

LEVEL II

Class II evidence from multiple studies and a significant number of Class III series support the addition of diffusion and perfusion weighted MR imaging in the assessment of suspected LGGs, for the purposes of discriminating the potential for tumor subtypes and identification of suspicion of higher grade diagnoses.

LEVEL III

Multiple series offer Class III evidence to support the potential for magnetic resonance spectroscopy (MRS) and nuclear medicine methods including positron emission tomography and single-photon emission computed tomography imaging to offer additional diagnostic specificity although these are less well defined and their roles in clinical practice are still being defined.

QUESTION

Which imaging sequences or parameters best predict the biological behavior or prognosis for patients with LGG?

TARGET POPULATION

These recommendations apply to adults with a newly diagnosed lesion with a suspected or histopathologically proven LGG.

RECOMMENDATION

Anatomic and advanced imaging methods and prognostic stratification

LEVEL III

Multiple series suggest a role for anatomic and advanced sequences to suggest prognostic stratification among low grade gliomas. Perfusion weighted imaging, particularly when obtained as a part of diagnostic evaluation (as recommended above) can play a role in consideration of prognosis. Other imaging sequences remain investigational in terms of their role in consideration of tumor prognosis as there is insufficient evidence to support more formal recommendations as to their use at this time.

QUESTION

What is the optimal imaging technique to be used in the follow-up of a suspected (or biopsy proven) LGG?

TARGET POPULATION

This recommendation applies to adults with a newly diagnosed low grade glioma.

RECOMMENDATIONS

LEVEL II

In patients with a diagnosis of LGG, anatomic imaging sequences should include T2/FLAIR MR sequences and T1 weighted imaging before and after the administration of gadolinium based contrast. Serial imaging should be performed to identify new areas of contrast enhancement or significant change in tumor size, which may signify transformation to a higher grade.

LEVEL III

Advanced imaging utility may depend on tumor subtype. Multicenter clinical trials with larger cohorts are needed. For astrocytic tumors, baseline and longitudinal elevations in tumor perfusion as assessed by dynamic susceptibility contrast perfusion MRI are associated with shorter time to tumor progression, but can be difficult to standardize in clinical practice. For oligodendrogliomas and mixed gliomas, MRS may be helpful for identification of progression.

Classification of brain tumours from MR spectra: the INTERPRET collaboration and its outcomes

The INTERPRET project was a multicentre European collaboration, carried out from 2000 to 2002, which developed a decision-support system (DSS) for helping neuroradiologists with no experience of MRS to utilize spectroscopic data for the diagnosis and grading of human brain tumours. INTERPRET gathered a large collection of MR spectra of brain tumours and pseudo-tumoural lesions from seven centres. Consensus acquisition protocols, a standard processing pipeline and strict methods for quality control of the aquired data were put in place. Particular emphasis was placed on ensuring the diagnostic certainty of each case, for which all cases were evaluated by a clinical data validation committee. One outcome of the project is a database of 304 fully validated spectra from brain tumours, pseudotumoural lesions and normal brains, along with their associated images and clinical data, which remains available to the scientific and medical community. The second is the INTERPRET DSS, which has continued to be developed and clinically evaluated since the project ended. We also review here the results of the post-INTERPRET period. We evaluate the results of the studies with the INTERPRET database by other consortia or research groups. A summary of the clinical evaluations that have been performed on the post-INTERPRET DSS versions is also presented. Several have shown that diagnostic certainty can be improved for certain tumour types when the INTERPRET DSS is used in conjunction with conventional radiological image interpretation. About 30 papers concerned with the INTERPRET single-voxel dataset have so far been published. We discuss stengths and weaknesses of the DSS and the lessons learned. Finally we speculate on how the INTERPRET concept might be carried into the future.

Magnetic Resonance (MR) Metabolic Imaging in Glioma

This review is focused on describing the use of magnetic resonance (MR) spectroscopy for metabolic imaging of brain tumors. We will first review the MR metabolic imaging findings generated from preclinical models, focusing primarily on in vivo studies, and will then describe the use of metabolic imaging in the clinical setting. We will address relatively well-established (1) H MRS approaches, as well as (31) P MRS, (13) C MRS and emerging hyperpolarized (13) C MRS methodologies, and will describe the use of metabolic imaging for understanding the basic biology of glioma as well as for improving the characterization and monitoring of brain tumors in the clinic.

The diagnostic performance of magnetic resonance spectroscopy in differentiating high-from low-grade gliomas: A systematic review and meta-analysis

OBJECTIVE

Magnetic resonance spectroscopy (MRS) is a powerful tool for preoperative grading of gliomas. We performed a meta-analysis to evaluate the diagnostic performance of MRS in differentiating high-grade gliomas (HGGs) from low-grade gliomas (LGGs).

METHODS

PubMed and Embase databases were systematically searched for relevant studies of glioma grading assessed by MRS through 27 March 2015. Based on the data from eligible studies, pooled sensitivity, specificity, diagnostic odds ratio and areas under summary receiver operating characteristic curve (SROC) of different metabolite ratios were obtained.

RESULTS

Thirty articles comprising a total sample size of 1228 patients were included in our meta-analysis. Quantitative synthesis of studies showed that the pooled sensitivity/specificity of Cho/Cr, Cho/NAA and NAA/Cr ratios was 0.75/0.60, 0.80/0.76 and 0.71/0.70, respectively. The area under the curve (AUC) of the SROC was 0.83, 0.87 and 0.78, respectively.

CONCLUSIONS

MRS demonstrated moderate diagnostic performance in distinguishing HGGs from LGGs using tumoural metabolite ratios including Cho/Cr, Cho/NAA and NAA/Cr. Although there was no significant difference in AUC between Cho/Cr and Cho/NAA groups, Cho/NAA ratio showed higher sensitivity and specificity than Cho/Cr ratio and NAA/Cr ratio. We suggest that MRS should combine other advanced imaging techniques to improve diagnostic accuracy in differentiating HGGs from LGGs.

KEY POINTS

• MRS has moderate diagnostic performance in distinguishing HGGs from LGGs. • There is no significant difference in AUC between Cho/Cr and Cho/NAA ratios. • Cho/NAA ratio is superior to NAA/Cr ratio. • Cho/NAA ratio shows higher sensitivity and specificity than Cho/Cr and NAA/Cr ratios. • MRS should combine other advanced imaging techniques to improve diagnostic accuracy.

[Towards more precision in the therapy of brain tumors. Possibilities and limits of MRI]

Due to the introduction of advanced functional and spectroscopic magnetic resonance (MR) sequences, MR imaging has gained significant importance in neuro-oncology. In contrast to recent years when neuro-oncological imaging was mostly limited to contrast-enhanced T1-weighted images, advanced MR methods provide direct visualization and assessment of tumor pathophysiology. This article summarizes the most relevant MR methods for neuro-oncological imaging and highlights the pathophysiological background as well as potential clinical applications. Ultimately, this article gives a glimpse into the future and introduces potential applications of ultra-high field MRI.

Advances in Magnetic Resonance and Positron Emission Tomography Imaging: Assessing Response in the Treatment of Low-Grade Glioma

Following combined-modality therapy for the treatment of low-grade gliomas, the assessment of treatment response and the evaluation of disease progression are uniformly challenging. In this article, we review existing response criteria, and discuss the limitations of conventional magnetic resonance imaging to distinguish between progression and treatment effect. We review the data on advanced imaging techniques including positron emission tomography and functional magnetic resonance imaging, which may enhance the interpretation of posttreatment changes, and enable the earlier assessment of the efficacy and toxicity of therapy in these patients with prolonged survival.

Imaging evidence and recommendations for traumatic brain injury: advanced neuro- and neurovascular imaging techniques

SUMMARY

Neuroimaging plays a critical role in the evaluation of patients with traumatic brain injury, with NCCT as the first-line of imaging for patients with traumatic brain injury and MR imaging being recommended in specific settings. Advanced neuroimaging techniques, including MR imaging DTI, blood oxygen level-dependent fMRI, MR spectroscopy, perfusion imaging, PET/SPECT, and magnetoencephalography, are of particular interest in identifying further injury in patients with traumatic brain injury when conventional NCCT and MR imaging findings are normal, as well as for prognostication in patients with persistent symptoms. These advanced neuroimaging techniques are currently under investigation in an attempt to optimize them and substantiate their clinical relevance in individual patients. However, the data currently available confine their use to the research arena for group comparisons, and there remains insufficient evidence at the time of this writing to conclude that these advanced techniques can be used for routine clinical use at the individual patient level. TBI imaging is a rapidly evolving field, and a number of the recommendations presented will be updated in the future to reflect the advances in medical knowledge.

[PET in gliomas. Overview of current studies]

Gliomas which represent 30% of intracranial tumours are morphologic lesions and therefore CT and MRI are the first line diagnostic procedures with MRI giving better soft tissue resolution and permitting additional functional information. These mainly morphologic imaging modalities yield only restricted information on grade of malignancy, on infiltration into and effects on surrounding brain tissue, on differentiation between necrotic and recurrent tumour, on prognosis and on efficacy of treatment. Information on these important issues for patient management can be obtained by PET-studies of glucose metabolism with FDG, of aminoacid-uptake and protein synthesis with 11C-methionin, 18F-fluorethyltyrosin and 18F-fluor-deoxyphenylalanin and of proliferation by 18F-deoxythymidin. With the increasing availability of 18F-tracers PET has obtained wider spread clinical application. In all these applications a coregistration with morphologic imaging should be obtained, and for that purpose hybrid installations (PET-MR) are already being used.

An NMR metabolomics approach for the diagnosis of leptomeningeal carcinomatosis in lung adenocarcinoma cancer patients

Leptomeningeal carcinomatosis (LC) is a metastatic cancer invading the central nervous system (CNS). We previously reported a metabolomic diagnostic approach as tested on an animal model and compared with current modalities. Here, we provide a proof of concept by applying it to human LC originating from lung cancer, the most common cause of CNS metastasis. Cerebrospinal fluid from LC (n = 26) and normal groups (n = 41) were obtained, and the diagnosis was established with clinical signs, cytology, MRI and biochemical tests. The cytology on the CSF, the current gold standard, exhibited 69% sensitivity (~100% specificity) from the first round of CSF tapping. In comparison, the nuclear magnetic resonance spectra on the CSF showed a clear difference in the metabolic profile between the LC and normal groups. Multivariate analysis and cross-validation yielded the diagnostic sensitivity of 92%, the specificity of 96% and the area under the curve (AUC) of 0.991. Further spectral and statistical analysis identified myo-inositol (p < 5 × 10(-14)), creatine (p < 7 × 10(-8)), lactate (p < 9 × 10(-4)), alanine (p < 7.9 × 10(-3)) and citrate (p < 3 × 10(-4)) as the most contributory metabolites, whose combination exhibited an receiver-operating characteristic diagnostic AUC of 0.996. In addition, the metabolic profile could be correlated with the grading of radiological leptomeningeal enhancement (R(2) = 0.3881 and p = 6.66 × 10(-4)), suggesting its potential utility in grading LC. Overall, we propose that the metabolomic approach might augment current diagnostic modalities for LC, the accurate diagnosis of which remains a challenge.

Impacts of MR spectroscopic imaging on glioma patient management

Magnetic resonance (MR) modalities are routine imaging tools in the diagnosis and management of gliomas. MR spectroscopic imaging (MRSI), which relies on the metabolic characteristics of tissues, has been developed to accelerate the understanding of gliomas and to aid in effective clinical decision making and development of targeted therapies. In this review, the potentials and practical challenges to frequently use this technique in clinical management of gliomas are discussed. The applications of new biomarkers detectable by MRSI in differential glioma diagnosis, pre- and post-treatment evaluations, and neurosurgery are also addressed.

Malignant gliomas: current perspectives in diagnosis, treatment, and early response assessment using advanced quantitative imaging methods

Malignant gliomas consist of glioblastomas, anaplastic astrocytomas, anaplastic oligodendrogliomas and anaplastic oligoastrocytomas, and some less common tumors such as anaplastic ependymomas and anaplastic gangliogliomas. Malignant gliomas have high morbidity and mortality. Even with optimal treatment, median survival is only 12–15 months for glioblastomas and 2–5 years for anaplastic gliomas. However, recent advances in imaging and quantitative analysis of image data have led to earlier diagnosis of tumors and tumor response to therapy, providing oncologists with a greater time window for therapy management. In addition, improved understanding of tumor biology, genetics, and resistance mechanisms has enhanced surgical techniques, chemotherapy methods, and radiotherapy administration. After proper diagnosis and institution of appropriate therapy, there is now a vital need for quantitative methods that can sensitively detect malignant glioma response to therapy at early follow-up times, when changes in management of nonresponders can have its greatest effect. Currently, response is largely evaluated by measuring magnetic resonance contrast and size change, but this approach does not take into account the key biologic steps that precede tumor size reduction. Molecular imaging is ideally suited to measuring early response by quantifying cellular metabolism, proliferation, and apoptosis, activities altered early in treatment. We expect that successful integration of quantitative imaging biomarker assessment into the early phase of clinical trials could provide a novel approach for testing new therapies, and importantly, for facilitating patient management, sparing patients from weeks or months of toxicity and ineffective treatment. This review will present an overview of epidemiology, molecular pathogenesis and current advances in diagnoses, and management of malignant gliomas.

The impact of extent of resection on malignant transformation of pure oligodendrogliomas

Object

Recent evidence suggests that a greater extent of resection (EOR) extends malignant progression-free survival among patients with low-grade gliomas (LGGs). These studies, however, rely on the combined analysis of oligodendrogliomas, astrocytomas, and mixed oligoastrocytomas—3 histological subtypes with distinct genetic and molecular compositions. To assess the value of EOR in a homogeneous LGG patient population and delineate its impact on LGG transformation, the authors examined its effect on newly diagnosed supratentorial oligodendrogliomas.

Methods

The authors identified 93 newly diagnosed adult patients with WHO Grade II oligodendrogliomas treated with microsurgical resection at Barrow Neurological Institute. Clinical, laboratory, and radiographic data were collected retrospectively, including 1p/19q codeletion status and volumetric analysis based on T2-weighted MRI.

Results

The median preoperative and postoperative tumor volumes and EOR were 29.0 cm3 (range 1.3–222.7 cm3), 5.2 cm3 (range 0–156.1 cm3), and 85% (range 6%–100%), respectively. Median follow-up was 75.4 months, and there were 14 deaths (15%). Progression and malignant progression were identified in 31 (33%) and 20 (22%) cases, respectively. A greater EOR was associated with longer overall survival (p = 0.005) and progression-free survival (p = 0.004); however, a greater EOR did not prolong the interval to malignant progression, even when controlling for 1p/19q codeletion.

Conclusions

A greater EOR is associated with an improved survival profile for patients with WHO Grade II oligodendrogliomas. However, for this particular LGG patient population, the interval to tumor transformation is not influenced by cytoreduction. These data raise the possibility that the capacity for microsurgical resection to modulate malignant progression is mediated through biological mechanisms specific to nonoligodendroglioma LGG histologies.

Metabolic mapping of gliomas using hybrid MR-PET imaging: feasibility of the method and spatial distribution of metabolic changes

BACKGROUND AND PURPOSE

The most powerful adjunct to histopathology for the grading of gliomas seems to be the metabolic imaging using positron emission tomography and magnetic resonance spectroscopy (MRS). The purposes of this study were to examine the feasibility of simultaneous acquisition of both techniques for purposes of tumor grading in a newly launched hybrid magnetic resonance positron emission tomography (MR-PET) and to examine the spatial distributions of metabolic changes in gliomas.

MATERIALS AND METHODS

Twenty-eight consecutive patients with gliomas underwent simultaneous methionine (Met) MR-PET imaging for detection of the most malignant tumor part before surgical sampling. After coregistration and fusion of MR-PET and MRS data, tumor to normal brain (T/N) Met uptake ratios and the corresponding metabolites peaks (choline [Cho], creatine [Cr], and N-acetylaspartate [NAA]) in MRS were recorded. The patients were divided into 4 types on the basis of the relation between the Met uptake area and the increased metabolite ratios: type I, the increased Met uptake area had at least 50% overlap or was completely within the area of increased Cho/NAA ratio; type II, the increased Met uptake site had less than 50% overlap of increased Cho/NAA ratio site; type III, the increased Met uptake region had no spatial relationship with the "hot" lesions in the MRS maps; and type IV, there was no pathologically increased Met uptake. The surgical sampling was performed in the tumor part with the highest Met uptake and, in the absence of increased Met accumulation, in the site with the highest Cho/NAA ratio. All surgical samples were referred to the neuropathology division for histological grading.

RESULTS

A total of 16 low-grade gliomas (World Health Organization grade II) and 12 high-grade gliomas (World Health Organization grade III) were included. Three lesions (10%) of type I were identified. Four lesions (14%) were classified as type II and 6 lesions (21%) were classified as type 3, where the increased Met uptake region had no spatial relationship with the hot lesions in the MRS maps. In 15 of the 28 patients (54%), there was no increased Met accumulation (type 4 lesions). Maps of Cho/NAA and Cr/NAA showed a close spatial relationship in most of the patients. Median T/N Met uptake ratio in the pooled surgically sampled tumor sites was 1.6 (range, 1-3), and median Cho/NAA and Cho/Cr ratios were 2.1 (range, 0.9-5.8) and 1.5 (range, 0.5-8.3), respectively. Spearman rank correlations of the metabolic markers in the low-grade gliomas showed significant correlations between Met uptake and Cr/NAA ratio (ρ = 0.59; P = 0.015) as well as between Cho/NAA and Cr/NAA ratios (ρ = 0.79; P = 0.0002). The normalized tumor creatine was significantly higher in anaplastic tumors compared with the low-grade gliomas (P = 0.001). A tendency for a significant positive correlation was found between normalized tumor creatine and Met uptake in the anaplastic tumors.

CONCLUSIONS

Metabolic mapping before histological sampling is feasible using simultaneous MR-PET imaging. High T/N Met uptake ratio reflecting high expression of amino-acid membrane transporters, which is indicative of proliferating tumor cell populations, does not always spatially correlate with neuronal cell loss and cell membrane proliferation (Cho/NAA) seen in MRS. Increased Cr/NAA is associated with increased methionine uptake in low-grade gliomas, whereas normalized creatine in tumor tends to correlate with methionine accumulation, which indicates a possible coupling of these metabolic indices in anaplastic tumors. Thus, spatial distribution differences in gliomas should be taken into account when planning surgical sampling.

Metabolic changes in patients with aneurysmal subarachnoid hemorrhage apart from perfusion deficits: neuronal mitochondrial injury?

BACKGROUND AND PURPOSE

Neuronal damage in aSAH apart from perfusion deficits has been widely discussed. We aimed to test if cerebral injury occurs in aSAH independently from visible perfusion deficit by measuring cerebral metabolites in patients with aSAH without infarction or impaired perfusion.

MATERIALS AND METHODS

We performed 3T MR imaging including (1)H-MR spectroscopy, DWI, and MR perfusion in 58 patients with aSAH and 11 age-matched and sex-matched control patients with incidental aneurysm. We compared changes of NAA, Cho, Glx, Lac, and Cr between all patients with aSAH and controls, between patients with and without visible perfusion deficit or infarction and controls, and between patients with and without visible perfusion deficit or infarction by using the Wilcoxon signed-rank test.

RESULTS

We found that NAA significantly (P < .005) decreased in all patients with aSAH. Cho was significantly increased in all patients compared with controls (P < .05). In patients without impaired perfusion or infarction, Glx was significantly decreased compared with both controls (P = .005) and patients with impaired perfusion or infarction (P = .006).

CONCLUSIONS

The significant decrease of NAA and Glx in patients with aSAH but without impaired perfusion or infarction strongly suggests global metabolic changes independent from visible perfusion deficits that might reflect neuronal mitochondrial injury. Further, impaired perfusion in aSAH seems to induce additional metabolic changes from increasing neuronal stress that might, to some extent, mask the global metabolic changes.

1H-MR spectroscopy metabolite levels correlate with executive function in vascular cognitive impairment

BACKGROUND

White matter hyperintensities (WMHs) are associated with vascular cognitive impairment (VCI) but fail to correlate with neuropsychological measures. As proton MR spectroscopy ((1)H-MRS) can identify ischaemic tissue, we hypothesised that MRS detectable brain metabolites would be superior to WMHs in predicting performance on neuropsychological tests.

METHODS

60 patients with suspected VCI underwent clinical, neuropsychological, MRI and CSF studies. They were diagnosed as having subcortical ischaemic vascular disease (SIVD), multiple infarcts, mixed dementia and leukoaraiosis. We measured brain metabolites in a white matter region above the lateral ventricles with (1)H-MRS and WMH volume in this region and throughout the brain.

RESULTS

We found a significant correlation between both total creatine (Cr) and N-acetylaspartyl compounds (NAA) and standardised neuropsychological test scores. Cr levels in white matter correlated significantly with executive function (p=0.001), attention (p=0.03) and overall T score (p=0.007). When lesion volume was added as a covariate, NAA also showed a significant correlation with executive function (p=0.003) and overall T score (p=0.015). Furthermore, while metabolite levels also correlated with total white matter lesion volume, adjusting the Cr levels for lesion volume did not diminish the strength of the association between Cr levels and neuropsychological scores. The lowest metabolite levels and neuropsychological scores were found in the SIVD group. Finally, lesion volume alone did not correlate significantly with any neuropsychological test score.

CONCLUSION

These results suggest that estimates of neurometabolite levels provide additional and useful information concerning cognitive function in VCI not obtainable by measurements of lesion load.

Survival analysis in patients with newly diagnosed glioblastoma using pre- and postradiotherapy MR spectroscopic imaging

BACKGROUND

The objective of this study was to examine the predictive value of parameters of 3D (1)H magnetic resonance spectroscopic imaging (MRSI) prior to treatment with radiation/chemotherapy (baseline) and at a postradiation 2-month follow-up (F2mo) in relationship to 6-month progression-free survival (PFS6) and overall survival (OS).

METHODS

Sixty-four patients with newly diagnosed glioblastoma multiforme (GBM) being treated with radiation and concurrent chemotherapy were involved in this study. Evaluated were metabolite indices and metabolite ratios. Logistic linear regression and Cox proportional hazards models were utilized to evaluate PFS6 and OS, respectively. These analyses were adjusted by age and MR scanner field strength (1.5 T or 3 T). Stepwise regression was performed to determine a subset of the most relevant variables.

RESULTS

Associated with shorter PFS6 were a decrease in the ratio of N-acetyl aspartate to choline-containing compounds (NAA/Cho) in the region with a Cho-to-NAA index (CNI) >3 at baseline and an increase of the CNI within elevated CNI regions (>2) at F2mo. Patients with higher normalized lipid and lactate at either time point had significantly worse OS. Patients who had larger volumes with abnormal CNI at F2mo had worse PFS6 and OS.

CONCLUSIONS

Our study found more 3D MRSI parameters that predicted PFS6 and OS for patients with GBM than did anatomic, diffusion, or perfusion imaging, which were previously evaluated in the same population of patients.

Potential of MR spectroscopy for assessment of glioma grading

BACKGROUND

Magnetic resonance spectroscopy (MRS) is an imaging diagnostic method based that allows non-invasive measurement of metabolites in tissues. There are a number of metabolites that can be identified by standard brain proton MRS but only a few of them has a clinical significance in diagnosis of gliomas including N-acetylaspartate, choline, creatine, myo-inositol, lactate, and lipids.

METHODS

In this review, we describe potential of MRS for grading of gliomas.

RESULTS

Low-grade gliomas are generally characterized by a relatively high concentration of N-acetylaspartate, low level of choline and absence of lactate and lipids. The increase in creatine concentration indicates low-grade gliomas with earlier progression and malignant transformation. Progression in grade of a glioma is reflected in the progressive decrease in the N-acetylaspartate and myo-inositol levels on the one hand and elevation in choline level up to grade III on the other. Malignant transformation of the glial tumors is also accompanied by the presence of lactate and lipids in MR spectra of grade III but mainly grade IV gliomas. It follows that MRS is a helpful method for detection of glioma regions with aggressive growth or upgrading due to favorable correlation of the choline and N-acetylaspartate levels with histopathological proliferation index Ki-67. Thus, magnetic resonance spectroscopy is also a suitable method for the targeting of brain biopsies.

CONCLUSIONS

Gliomas of each grade have some specific MRS features that can be used for improvement of the diagnostic value of conventional magnetic resonance imaging in non-invasive assessment of glioma grade.

Emerging imaging tools for use with traumatic brain injury research

This article identifies emerging neuroimaging measures considered by the inter-agency Pediatric Traumatic Brain Injury (TBI) Neuroimaging Workgroup. This article attempts to address some of the potential uses of more advanced forms of imaging in TBI as well as highlight some of the current considerations and unresolved challenges of using them. We summarize emerging elements likely to gain more widespread use in the coming years, because of 1) their utility in diagnosis, prognosis, and understanding the natural course of degeneration or recovery following TBI, and potential for evaluating treatment strategies; 2) the ability of many centers to acquire these data with scanners and equipment that are readily available in existing clinical and research settings; and 3) advances in software that provide more automated, readily available, and cost-effective analysis methods for large scale data image analysis. These include multi-slice CT, volumetric MRI analysis, susceptibility-weighted imaging (SWI), diffusion tensor imaging (DTI), magnetization transfer imaging (MTI), arterial spin tag labeling (ASL), functional MRI (fMRI), including resting state and connectivity MRI, MR spectroscopy (MRS), and hyperpolarization scanning. However, we also include brief introductions to other specialized forms of advanced imaging that currently do require specialized equipment, for example, single photon emission computed tomography (SPECT), positron emission tomography (PET), encephalography (EEG), and magnetoencephalography (MEG)/magnetic source imaging (MSI). Finally, we identify some of the challenges that users of the emerging imaging CDEs may wish to consider, including quality control, performing multi-site and longitudinal imaging studies, and MR scanning in infants and children.

Low-grade gliomas in adults

In recent years, advances in the understanding of low-grade glioma (LGG) biology have driven new paradigms in molecular markers, diagnostic imaging, operative techniques and technologies, and adjuvant therapies. Taken together, these developments are collectively pushing the envelope toward improved quality of life and survival. In this article, the authors evaluate the recent literature to synthesize a comprehensive review of LGGs in the modern neurosurgical era.