In vivo differentiation of astrocytic brain tumors and isolated demyelinating lesions of the type seen in multiple sclerosis using 1H magnetic resonance spectroscopic imaging

Quantifying the Metabolic Signature of Multiple Sclerosis by in vivo Proton Magnetic Resonance Spectroscopy: Current Challenges and Future Outlook in the Translation From Proton Signal to Diagnostic Biomarker

Proton magnetic resonance spectroscopy (¹H-MRS) offers a growing variety of methods for querying potential diagnostic biomarkers of multiple sclerosis in living central nervous system tissue. For the past three decades, ¹H-MRS has enabled the acquisition of a rich dataset suggestive of numerous metabolic alterations in lesions, normal-appearing white matter, gray matter, and spinal cord of individuals with multiple sclerosis, but this body of information is not free of seeming internal contradiction. The use of ¹H-MRS signals as diagnostic biomarkers depends on reproducible and generalizable sensitivity and specificity to disease state that can be confounded by a multitude of influences, including experiment group classification and demographics; acquisition sequence; spectral quality and quantifiability; the contribution of macromolecules and lipids to the spectroscopic baseline; spectral quantification pipeline; voxel tissue and lesion composition; T₁ and T₂ relaxation; B₁ field characteristics; and other features of study design, spectral acquisition and processing, and metabolite quantification about which the experimenter may possess imperfect or incomplete information. The direct comparison of ¹H-MRS data from individuals with and without multiple sclerosis poses a special challenge in this regard, as several lines of evidence suggest that experimental cohorts may differ significantly in some of these parameters. We review the existing findings of in vivo¹H-MRS on central nervous system metabolic abnormalities in multiple sclerosis and its subtypes within the context of study design, spectral acquisition and processing, and metabolite quantification and offer an outlook on technical considerations, including the growing use of machine learning, by future investigations into diagnostic biomarkers of multiple sclerosis measurable by ¹H-MRS.

ACRIN 6684: Multicenter, phase II assessment of tumor hypoxia in newly diagnosed glioblastoma using magnetic resonance spectroscopy

A multi-center imaging trial by the American College of Radiology Imaging Network (ACRIN) "A Multicenter, phase II assessment of tumor hypoxia in glioblastoma using 18F Fluoromisonidazole (FMISO) with PET and MRI (ACRIN 6684)", was conducted to assess hypoxia in patients with glioblastoma (GBM). The aims of this study were to support the role of proton magnetic resonance spectroscopic imaging (1H MRSI) as a prognostic marker for brain tumor patients in multi-center clinical trials. Seventeen participants from four sites had analyzable 3D MRSI datasets acquired on Philips, GE or Siemens scanners at either 1.5T or 3T. MRSI data were analyzed using LCModel to quantify metabolites N-acetylaspartate (NAA), creatine (Cr), choline (Cho), and lactate (Lac). Receiver operating characteristic curves for NAA/Cho, Cho/Cr, lactate/Cr, and lactate/NAA were constructed for overall survival at 1-year (OS-1) and 6-month progression free survival (PFS-6). The OS-1 for the 17 evaluable patients was 59% (10/17). Receiver operating characteristic analyses found the NAA/Cho in tumor (AUC = 0.83, 95% CI: 0.61 to 1.00) and in peritumoral regions (AUC = 0.95, 95% CI 0.85 to 1.00) were predictive for survival at 1 year. PFS-6 was 65% (11/17). Neither NAA/Cho nor Cho/Cr was effective in predicting 6-month progression free survival. Lac/Cr in tumor was a significant negative predictor of PFS-6, indicating that higher lactate/Cr levels are associated with poorer outcome. (AUC = 0.79, 95% CI: 0.54 to 1.00). In conclusion, despite the small sample size in the setting of a multi-center trial comprising different vendors, field strengths, and varying levels of expertise at data acquisition, MRS markers NAA/Cho, Lac/Cr and Lac/NAA predicted overall survival at 1 year and 6-month progression free survival. This study validates that MRSI may be useful in evaluating the prognosis in glioblastoma and should be considered for incorporating into multi-center clinical trials.

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.

Anaplastic astrocytoma mimicking progressive multifocal leucoencephalopathy: a case report and review of the overlapping syndromes

Background

Co-occurrence of multiple sclerosis (MS) and glial tumours (GT) is uncommon although occasionally reported in medical literature. Interpreting the overlapping radiologic and clinical characteristics of glial tumours, MS lesions, and progressive multifocal leukoencephalopathy (PML) can be a significant diagnostic challenge.

Case presentation

We report a case of anaplastic astrocytoma mimicking PML in a 27-year-old patient with a 15-year history of MS. She was treated with interferon, natalizumab and finally fingolimod due to active MS. Follow-up MRI, blood and cerebrospinal fluid examinations, and biopsy were conducted, but only the latter was able to reveal the cause of progressive worsening of patient’s disease.

Conclusions

Anaplastic astrocytoma misdiagnosed as PML has not yet been described. We suppose that the astrocytoma could have evolved from a low grade glioma to anaplastic astrocytoma over time, as the tumour developed adjacent to typical MS plaques. The role of the immunomodulatory treatment as well as other immunological factors in the malignant transformation can only be hypothesised. We discuss clinical, laboratory and diagnostic aspects of a malignant GT, MS lesions and PML. The diagnosis of malignant GT must be kept in mind when an atypical lesion develops in a patient with MS.

Liver Transplant Recipient With Tumefactive Demyelinating Lesions: A Case Report and Literature Review

Tumefactive demyelinating lesions (TDLs) that may resemble brain neoplasms or abscesses are uncommon but noteworthy. A solid knowledge of how to distinguish TDLs from malignancy or infection is a key step to avoid unnecessary medical or surgical interventions. Almost all the intracranial demyelination diseases after liver transplantation (LT) refer to central pontine myelinolysis or extrapontine myelinolysis; TDLs after LT have never been reported. In 2005, a 45-year-old Chinese male underwent orthotopic LT due to "acute on chronic liver failure" in our hospital. He took triple anti-rejection drugs including tacrolimus, mycophenolate mofetil, and corticosteroids after LT. In 2010, he was admitted for right limb weakness, and the head magnetic resonance imaging and magnetic resonance spectroscopy revealed the lesions were more likely to be TDLs. His symptoms disappeared after he was administered corticosteroid therapy which proved the diagnosis. Five years later, he was admitted again to hospital with dizziness and double version. The magnetic resonance image and magnetic resonance spectroscopy showed that the new solitary lesion in the cerebellum may in fact be the new TDL. He received corticosteroid therapy and was discharged after symptoms improved. Herein, to our knowledge, we reported the first case of TDL after LT. We reported this case to provide helpful information to clinicians about intracranial demyelination diseases after LT which maybe are not always central pontine myelinolysis or extrapontine myelinolysis.

Lymphomas-Part 2

There are 2 types of central nervous system lymphoma: primary and secondary. Both have variable imaging features making them diagnostic challenges. Furthermore, a patient's immune status significantly alters the imaging findings. Familiarity with typical appearances, variations, and common mimics aids radiologists in appropriately considering lymphoma in the differential diagnosis. Moreover, special types of lymphoma, such as lymphomatosis cerebri, intravascular lymphoma, and lymphomatoid granulomatosis, also are found. This article discusses uncommon types of lymphoma and the differential diagnosis for focal, multifocal, meningeal, and infiltrative lymphomas.

Atypical idiopathic inflammatory demyelinating lesions (IIDL): conventional and diffusion-weighted MR imaging (DWI) findings in 42 cases

INTRODUCTION

The purpose of this study was to evaluate MR imaging characteristics with conventional and advanced MR imaging techniques in patients with IIDL.

METHODS

MR images of the brain in 42 patients (20 male, 22 female) with suspected or known multiple sclerosis (MS) from four institutions were retrospectively analyzed. Lesions were classified into five different subtypes: (1) ring-like lesions; (2) Balo-like lesions; (3) diffuse infiltrating lesions; (4) megacystic lesions; and (5) unclassified lesions. The location, size, margins, and signal intensities on T1WI, T2WI, and diffusion-weighted images (DWI), and the ADC values/ratios for all lesions, as well as the contrast enhancement pattern, and the presence of edema, were recorded.

RESULTS

There were 30 ring-like, 10 Balo-like, 3 megacystic-like and 16 diffuse infiltrating-like lesions were detected. Three lesions were categorized as unclassified lesions. Of the 30 ring-like lesions, 23 were hypointense centrally with a hyperintense rim. The mean ADC, measured centrally, was 1.50 ± 0.41 × 10(-3) mm(2)/s. The mean ADC in the non-enhancing layers of the Balo-like lesions was 2.29 ± 0.17 × 10(-3) mm(2)/s, and the mean ADC in enhancing layers was 1.03 ± 0.30 × 10(-3) mm(2)/s. Megacystic lesions had a mean ADC of 2.14 ± 0.26 × 10(-3)mm(2)/s. Peripheral strong enhancement with high signal on DWI was present in all diffuse infiltrating lesions. Unclassified lesions showed a mean ADC of 1.43 ± 0.13 mm(2)/s.

CONCLUSION

Restriction of diffusion will be seen in the outer layers of active inflammation/demyelination in Balo-like lesions, in the enhancing part of ring-like lesions, and at the periphery of infiltrative-type lesions.

1H magnetic resonance spectroscopy in multiple sclerosis and related disorders

Proton magnetic resonance spectroscopy ((1)H-MRS) is an unconventional technique that allows noninvasive characterization of metabolic abnormalities in the central nervous system. (1)H-MRS provides important insights into the chemical-pathologic changes that occur in patients with multiple sclerosis (MS). In this review article we present the main brain and spinal cord (1)H-MRS features in MS, their diagnostic value in differentiating pseudotumoral demyelinating lesions from primary brain tumors, and their relationship with clinical variables. Last, some data related to the use of (1)H-MRS in therapeutic trials is presented.

Benign course of tumour-like multiple sclerosis. Report of five cases and literature review

BACKGROUND

Multiple sclerosis (MS) with initial neuroradiological features suggestive of brain tumour (tumour-like MS) may represent a challenging diagnosis.

METHODS

Among the patients seen at the MS centre of our Institution between 2000 and 2010, we identified cases presenting with a large (diameter>2 cm), well-defined lesion, suggestive of brain tumour on initial brain magnetic resonance imaging (MRI). Only patients with at least 10 years follow-up were included.

RESULTS

Five young women with MS who presented with a tumour-like lesion on initial brain MRI are described. All cases presented with sudden-onset neurological deficits due to a single large brain lesion compatible with neoplasm at MRI. Two cases underwent brain stereotactic biopsy, both misdiagnosed as astrocytoma. However, the subsequent clinical and MRI follow-up was consistent with MS in all cases. Unnecessary surgery and radiotherapy were responsible for disability in two cases. In three cases, the course of the disease remains benign after more than 13 years from symptoms onset.

CONCLUSIONS

Our report of clinical, radiological and pathological features of five tumour-like MS cases confirms that it is mandatory to consider a demyelinating process in the differential diagnosis of tumour-like brain lesions. Many tumour-like MS cases may have a favourable long term prognosis.

MR imaging of neoplastic central nervous system lesions: review and recommendations for current practice

MR imaging is the preferred technique for the diagnosis, treatment planning, and monitoring of patients with neoplastic CNS lesions. Conventional MR imaging, with gadolinium-based contrast enhancement, is increasingly combined with advanced, functional MR imaging techniques to offer morphologic, metabolic, and physiologic information. This article provides updated recommendations to neuroradiologists, neuro-oncologists, neurosurgeons, and radiation oncologists on the practical applications of MR imaging of neoplastic CNS lesions in adults, with particular focus on gliomas, based on a review of the clinical trial evidence and personal experiences shared at a recent international meeting of experts in neuroradiology, neuro-oncology, neurosurgery, and radio-oncology.

Imaging of brain tumors: MR spectroscopy and metabolic imaging

The utility of magnetic resonance spectroscopy (MRS) in diagnosis and evaluation of treatment response to human brain tumors has been widely documented. The role of MRS in tumor classification, tumors versus nonneoplastic lesions, prediction of survival, treatment planning, monitoring of therapy, and post-therapy evaluation is discussed. This article delineates the need for standardization and further study in order for MRS to become widely used as a routine clinical tool.

Functional MRI for Radiotherapy of Gliomas

In this paper, we review the applications of functional magnetic resonance imaging (MRI) for target delineation and critical organ avoidance for brain radiotherapy. In this article we distinguish functional MRI from brain functional MRI (fMRI). Functional MRI includes magnetic resonance spectroscopic imaging (MRSI), perfusion MRI, diffusion tensor imaging (DTI) and brain fMRI. These functional MRI modalities can provide unique metabolic, pathological and physiological information that are not available in anatomic MRI and can potentially improve the treatment outcomes of brain tumors. For example, both choline (Cho) to N-acetylaspartate (NAA) and Cho to creatine (Cr) ratios from MRSI increase with increasing tumor malignancy and can be used to grade gliomas. Relative cerebral blood volume (rCBV) measurements from dynamic susceptibility contrast perfusion magnetic resonance imaging (DSC MRI) are superior to conventional contrast-enhanced MRI in predicting tumor biology and may be even superior to pathologic assessment in predicting patient clinical outcomes. Brain fMRI can help identify and avoid functionally critical areas when constructing treatment plans for brain radiotherapy. In the past, functional MRI measurements have not been routinely used in a clinical arena due to the experimental nature of these imaging modalities. As these methods become more commonly used and effective image co-registration algorithms become available, integration of functional MRI into the treatment process of brain radiotherapy now appears to be clinically feasible, at least in major medical centers.

Using ex vivo proton magnetic resonance spectroscopy to reveal associations between biochemical and biological features of meningiomas

Object

The goal in this study was to determine if proton (1H) MR spectroscopy can differentiate meningioma grade and is associated with interpretations of biological behavior; the study was performed using ex vivo high-resolution spectra indicating metabolic characteristics.

Methods

Sixty-eight resected tissue samples of meningiomas were examined using ex vivo 1H MR spectroscopy. Of these meningiomas, 46 were WHO Grade I, 14 were WHO Grade II, and 8 were WHO Grade III. Fifty-nine were primary meningiomas and 9 were recurrences. Invasion of adjacent tissue (dura mater, bone, venous sinus, brain) was found in 32 cases. Thirty-nine meningiomas did not rapidly recur (as defined by expansion on MR imaging within a 5-year follow-up period), whereas rapid recurrence was confirmed in 24 meningiomas, and follow-up status was unknown in 5 cases.

Results

The absolute concentrations of total alanine and creatine were decreased in high-grade compared with low-grade meningiomas, as was the ratio of glycine to alanine (all p < 0.05). Additionally, alanine and the glycine/alanine ratio distinguished between primary and recurrent meningiomas (all p < 0.05). Finally, the absolute concentrations of alanine and creatine, and the glycine/alanine and choline/glutamate ratios were associated with rapid recurrence (p < 0.05).

Conclusions

. These data indicate that meningioma tissue can be characterized by metabolic parameters that are not typically identified by histopathological analysis alone. Creatine, glycine, and alanine may be used as markers of meningioma grade, recurrence, and the likelihood of rapid recurrence. These data validate a previous study of a separate group of Grade I meningiomas.

Homonymous hemianopsia as the leading symptom of a tumor like demyelinating lesion: a case report

Introduction

Differential diagnosis of a cerebral lesion can prove to be a very challenging task for the treating physician. Many non-neoplastic neurological diseases can mimic brain neoplasms on neuroimaging.

Case presentation

A previously healthy 23-year-old male, presented with blurred vision to the Emergency Department of our Hospital. After initial clinical and serological examination, he was admitted to our clinic for further investigation. Neurological examination showed left homonymous hemianopsia. Brain MRI revealed edema of the right parietal lobe, compressing the posterior region of the right ventricle. Serum viral, immunological and paraneoplasmatic testing were negative. Spectroscopic MRI described the lesions as tumefactive demyelinated plaques. After treating the patient with intravenous corticosteroids, his symptoms rapidly improved and the extensive lesion of the parietal lobe decreased.

Conclusion

In case of young patients with tumor-like lesions, demyelination should always be considered in the differential diagnosis.

Quantitative imaging biomarkers in neuro-oncology

Conventional structural imaging provides limited information on tumor characterization and prognosis. Advances in neurosurgical techniques, radiotherapy planning and novel drug treatments for brain tumors have generated increasing need for reproducible, noninvasive, quantitative imaging biomarkers. This Review considers the role of physiological MRI and PET molecular imaging in understanding metabolic processes associated with tumor growth, blood flow and ultrastructure. We address the utility of various techniques in distinguishing between tumors and non-neoplastic processes, in tumor grading, in defining anatomical relationships between tumor and eloquent brain regions and in determining the biological substrates of treatment response. Much of the evidence is derived from limited case series in individual centers. Despite their 'added value', the effect of these techniques as an adjunct to structural imaging in clinical research and practice remains limited.

Proton MR spectroscopy improves discrimination between tumor and pseudotumoral lesion in solid brain masses

BACKGROUND AND PURPOSE

Differentiating between tumors and pseudotumoral lesions by conventional MR imaging may be a challenging question. This study aims to evaluate the potential usefulness and the added value that single-voxel proton MR spectroscopy could provide on this discrimination.

MATERIALS AND METHODS

A total of 84 solid brain lesions were retrospectively included in the study (68 glial tumors and 16 pseudotumoral lesions). Single-voxel spectra at TE 30 ms (short TE) and 136 ms (long TE) were available in all cases. Two groups were defined: "training-set" (56 cases) and "test-set" (28 cases). Tumors and pseudotumors were compared in the training-set with the Mann-Whitney U test. Ratios between resonances were defined as classifiers for new cases, and thresholds were selected with receiver operating characteristic (ROC) curves. The added value of spectroscopy was evaluated by 5 neuroradiologists and assessed with the Wilcoxon signed-rank test.

RESULTS

Differences between tumors and pseudotumors were found in myo-inositol (mIns); P < .01) at short TE, and N-acetylaspartate (NAA; P < .001), glutamine (Glx; P < .01), and choline (CHO; P < .05) at long TE. Classifiers suggested tumor when mIns/NAA ratio was more than 0.9 at short TE and also when CHO/NAA ratio was more than 1.9 at long TE. Classifier accuracy was tested in the test-set with the following results: short TE, 82% (23/28); long TE, 79% (22/28). The neuroradiologists' confidence rating of the test-cases on a 5-point scale (0-4) improved between 5% (from 2.86-3) and 27% (from 2.25-2.86) with spectroscopy (mean, 17%; P < .01).

CONCLUSIONS

The proposed ratios of mIns/NAA at short TE and CHO/NAA at long TE provide valuable information to discriminate between brain tumor and pseudotumor by improving neuroradiologists' accuracy and confidence.

What insights have new imaging techniques given into aggressive forms of MS--different forms of MS or different from MS?

"Aggressive" multiple sclerosis (MS) is still a challenging diagnosis, in spite of the relevant progresses concerning the comprehension of the disease mechanisms, especially through pathology studies and the advent of conventional magnetic resonance imaging (MRI). Some reviews have been already published on their clinical and therapeutical aspects, but no systematic review is available in literature about the neuroradiological features, using both conventional and advanced techniques. In particular, advanced MRI techniques, namely diffusion-weighted and tensor imaging, magnetization transfer imaging, and proton magnetic resonance spectroscopy, are giving new insights to find specific and appropriate radiological parameters that can help in targeting the diagnosis. We report a review of literature on the neuroradiological findings of aggressive forms of MS, focusing specifically on the role of advanced MRI techniques in the diagnostic phase and during follow-up.

Cerebral ependymoma in a patient with multiple sclerosis case report and critical review of the literature

BACKGROUND

The concurrence of multiple sclerosis (MS) and brain tumors is a rare but well-recognized condition. The radiologic evidence of the progressive evolution of a mega-plaque in a tumor has never been described. We report the first case of such an occurrence.

METHODS

A 27-year-old woman with a diagnosis of MS was referred to us for an intense frontal headache. Magnetic resonance imaging showed a mass lesion in correspondence of a black hole lesion previously diagnosed. The patient was operated on, with complete removal of the tumor documented by an intraoperative MRI. The histologic examination evidenced an ependymoma. Postoperative radiotherapy was performed.

RESULTS

The patient is well and recurrence-free at 2 years follow-up.

CONCLUSIONS

The present case, documenting the transformation of a mega-plaque into a tumor, suggests a cause-effect relationship between MS and brain tumors.

Demyelination or low-grade glioma? A diagnostic dilemma

BACKGROUND

Demyelination is a neurologic disease, usually diagnosed on the basis of clinical symptomatology and radiologic studies. Rarely, both may be deceiving and masquerading a neoplastic lesion or vice versa.

CASE DESCRIPTION

In the present communication, we describe 2 cases with similar clinical profiles and radiologic pictures, but which turn out to be contrasting pathologic diagnoses.

CONCLUSIONS

We emphasize on histopathologic proof before initiating definitive therapy.

Can proton MR spectroscopic and perfusion imaging differentiate between neoplastic and nonneoplastic brain lesions in adults?

BACKGROUND AND PURPOSE

Noninvasive diagnosis of brain lesions is important for the correct choice of treatment. Our aims were to investigate whether 1) proton MR spectroscopic imaging ((1)H-MRSI) can aid in differentiating between tumors and nonneoplastic brain lesions, and 2) perfusion MR imaging can improve the classification.

MATERIALS AND METHODS

We retrospectively examined 69 adults with untreated primary brain lesions (brain tumors, n = 36; benign lesions, n = 10; stroke, n = 4; demyelination, n = 10; and stable lesions not confirmed on pathologic examination, n = 9). MR imaging and (1)H-MRSI were performed at 1.5T before biopsy or treatment. Concentrations of N-acetylaspartate (NAA), creatine (Cr), and choline (Cho) in the lesion were expressed as metabolite ratios and were normalized to the contralateral hemisphere. Dynamic susceptibility contrast-enhanced perfusion MR imaging was performed in a subset of patients (n = 32); relative cerebral blood volume (rCBV) was evaluated. Discriminant function analysis was used to identify variables that can predict inclusion in the neoplastic or nonneoplastic lesion groups. Receiver operator characteristic (ROC) analysis was used to compare the discriminatory capability of (1)H-MRSI and perfusion MR imaging.

RESULTS

The discriminant function analysis correctly classified 84.2% of original grouped cases (P < .0001), on the basis of NAA/Cho, Cho(norm), NAA(norm), and NAA/Cr ratios. MRSI and perfusion MR imaging had similar discriminatory capabilities in differentiating tumors from nonneoplastic lesions. With cutoff points of NAA/Cho < or =0.61 and rCBV > or =1.50 (corresponding to diagnosis of the tumors), a sensitivity of 72.2% and specificity of 91.7% in differentiating tumors from nonneoplastic lesions were achieved.

CONCLUSION

These results suggest a promising role for (1)H-MRSI and perfusion MR imaging in the distinction between brain tumors and nonneoplastic lesions in adults.

Use of MR spectroscopy and functional imaging in the treatment planning of gliomas

Routine anatomical imaging with CT and MRI does not reliably indicate the true extent or the most malignant areas of gliomas and cannot identify the functionally critical parts of the brain. The aim of the study was to see if the use of MR spectroscopic imaging (MRSI) along with functional MRI (fMRI) can better define both the target and the critical structures to be avoided to improve radiation delivery in gliomas. 12 patients with gliomas underwent multivoxel MRS and functional imaging using GE processing software. The choline to creatine ratio (Cho:Cr), which represents the degree of abnormality for each individual voxel on MRSI, was derived, converted into a grayscale grading system, fused to the MRI images and then transferred to the planning CT images. An intensity-modulated radiation therapy (IMRT) plan was developed using the dose constraints based on both the anatomical and the functionally critical regions. Cho:Cr consistently identified the gross tumour volume (GTV) within the microscopic disease (clinical target volume, CTV) and allowed dose painting using IMRT. No correlation between MRSI based Cho:Cr > or =2 and MR defined CTV nor their location was noted. However, MRSI defined Cho:Cr > or =3 was smaller by 40% compared with post-contrast T1 weighted MRI defined GTV volumes. fMRI helped in optimizing the orientation of the beams. In conclusion, both MRSI and fMRI provide additional information to conventional imaging that may guide dose painting in treatment planning of gliomas. A Phase I IMRT dose intensification trial in gliomas using this information is planned.

Idiopathic inflammatory-demyelinating diseases of the central nervous system

Idiopathic inflammatory-demyelinating diseases (IIDDs) include a broad spectrum of central nervous system disorders that can usually be differentiated on the basis of clinical, imaging, laboratory and pathological findings. However, there can be a considerable overlap between at least some of these disorders, leading to misdiagnoses or diagnostic uncertainty. The relapsing-remitting and secondary progressive forms of multiple sclerosis (MS) are the most common IIDDs. Other MS phenotypes include those with a progressive course from onset (primary progressive and progressive relapsing) or with a benign course continuing for years after onset (benign MS). Uncommon forms of IIDDs can be classified clinically into: (1) fulminant or acute IIDDs, such as the Marburg variant of MS, Baló's concentric sclerosis, Schilder's disease, and acute disseminated encephalomyelitis; (2) monosymptomatic IIDDs, such as those involving the spinal cord (transverse myelitis), optic nerve (optic neuritis) or brainstem and cerebellum; and (3) IIDDs with a restricted topographical distribution, including Devic's neuromyelitis optica, recurrent optic neuritis and relapsing transverse myelitis. Other forms of IIDD, which are classified clinically and radiologically as pseudotumoral, can have different forms of presentation and clinical courses. Although some of these uncommon IIDDs are variants of MS, others probably correspond to different entities. MR imaging of the brain and spine is the imaging technique of choice for diagnosing these disorders, and together with the clinical and laboratory findings can accurately classify them. Precise classification of these disorders may have relevant prognostic and treatment implications, and might be helpful in distinguishing them from tumoral or infectious lesions, avoiding unnecessary aggressive diagnostic or therapeutic procedures.

Pitfalls in the diagnosis of brain tumours

Establishing the diagnosis of a brain tumour is not always a straightforward process. Many non-neoplastic neurological diseases can mimic brain neoplasms on neuroimaging or on histological examination, including multiple sclerosis, stroke, pyogenic abscess, toxoplasmosis, tuberculosis, cysticercosis, fungal infections, syphilis, sarcoidosis, Behçet disease, radiation necrosis, venous thrombosis, and others. Conversely, several types of brain neoplasms, such as glioblastomas, low-grade gliomas, CNS lymphomas, and brain metastases, can present in the absence of typical tumefactive lesions, posing significant diagnostic challenges. In this Review, we discuss the process of accurately establishing the diagnosis of brain tumours, focusing on pitfalls commonly encountered in clinical practice. We also discuss the rational use and limitations of new diagnostic techniques, such as diffusion-weighted MRI, perfusion-weighted MRI, magnetic resonance spectroscopy, single-photon emission tomography, and positron emission tomography, as well as new tools for histological examination, such as immunohistochemistry and molecular genetics analysis.

Proton magnetic resonance spectroscopic imaging to differentiate between nonneoplastic lesions and brain tumors in children

PURPOSE

To investigate whether in vivo proton magnetic resonance spectroscopic imaging (MRSI) can differentiate between 1) tumors and nonneoplastic brain lesions, and 2) high- and low-grade tumors in children.

MATERIALS AND METHODS

Thirty-two children (20 males and 12 females, mean age = 10 +/- 5 years) with primary brain lesions were evaluated retrospectively. Nineteen patients had a neuropathologically confirmed brain tumor, and 13 patients had a benign lesion. Multislice proton MRSI was performed at TE = 280 msec. Ratios of N-acetyl aspartate/choline (NAA/Cho), NAA/creatine (Cr), and Cho/Cr were evaluated in the lesion and the contralateral hemisphere. Normalized lesion peak areas (Cho(norm), Cr(norm), and NAA(norm)) expressed relative to the contralateral hemisphere were also calculated. Discriminant function analysis was used for statistical evaluation.

RESULTS

Considering all possible combinations of metabolite ratios, the best discriminant function to differentiate between nonneoplastic lesions and brain tumors was found to include only the ratio of Cho/Cr (Wilks' lambda, P = 0.012; 78.1% of original grouped cases correctly classified). The best discriminant function to differentiate between high- and low-grade tumors included the ratios of NAA/Cr and Cho(norm) (Wilks' lambda, P = 0.001; 89.5% of original grouped cases correctly classified). Cr levels in low-grade tumors were slightly lower than or comparable to control regions and ranged from 53% to 165% of the control values in high-grade tumors.

CONCLUSION

Proton MRSI may have a promising role in differentiating pediatric brain lesions, and an important diagnostic value, particularly for inoperable or inaccessible lesions.

Image-fusion of MR spectroscopic images for treatment planning of gliomas

1H magnetic resonance spectroscopic imaging (MRSI) can improve the accuracy of target delineation for gliomas, but it lacks the anatomic resolution needed for image fusion. This paper presents a simple protocol for fusing simulation computer tomography (CT) and MRSI images for glioma intensity-modulated radiotherapy (IMRT), including a retrospective study of 12 patients. Each patient first underwent whole-brain axial fluid-attenuated-inversion-recovery (FLAIR) MRI (3 mm slice thickness, no spacing), followed by three-dimensional (3D) MRSI measurements (TE/TR: 144/1000 ms) of a user-specified volume encompassing the extent of the tumor. The nominal voxel size of MRSI ranged from 8 x 8 x 10 mm3 to 12 x 12 x 10 mm3. A system was developed to grade the tumor using the choline-to-creatine (Cho/Cr) ratios from each MRSI voxel. The merged MRSI images were then generated by replacing the Cho/Cr value of each MRSI voxel with intensities according to the Cho/Cr grades, and resampling the poorer-resolution Cho/Cr map into the higher-resolution FLAIR image space. The FUNCTOOL processing software was also used to create the screen-dumped MRSI images in which these data were overlaid with each FLAIR MRI image. The screen-dumped MRSI images were manually translated and fused with the FLAIR MRI images. Since the merged MRSI images were intrinsically fused with the FLAIR MRI images, they were also registered with the screen-dumped MRSI images. The position of the MRSI volume on the merged MRSI images was compared with that of the screen-dumped MRSI images and was shifted until agreement was within a predetermined tolerance. Three clinical target volumes (CTVs) were then contoured on the FLAIR MRI images corresponding to the Cho/Cr grades. Finally, the FLAIR MRI images were fused with the simulation CT images using a mutual-information algorithm, yielding an IMRT plan that simultaneously delivers three different dose levels to the three CTVs. The image-fusion protocol was tested on 12 (six high-grade and six low-grade) glioma patients. The average agreement of the MRSI volume position on the screen-dumped MRSI images and the merged MRSI images was 0.29 mm with a standard deviation of 0.07 mm. Of all the voxels with Cho/Cr grade one or above, the distribution of Cho/Cr grade was found to correlate with the glioma grade from pathologic finding and is consistent with literature results indicating Cho/Cr elevation as a marker for malignancy. In conclusion, an image-fusion protocol was developed that successfully incorporates MRSI information into the IMRT treatment plan for glioma.

[Proton magnetic resonance spectroscopy (1H-MRS) for the diagnosis of brain tumors and the evaluation of treatment]

MR spectroscopy (MRS) is a technique used to study a few metabolites in the brain or tumors in situ. This technique can provide information on tumor histological type and grade, and is helpful to identify tumor-like lesions, particularly abscesses. MRS can be used for treatment monitoring.

Noninvasive magnetic resonance spectroscopic imaging biomarkers to predict the clinical grade of pediatric brain tumors

The diagnosis and therapy of childhood brain tumors, most of which are low grade, can be complicated because of their frequent adjacent location to crucial structures, which limits diagnostic biopsy. Also, although new prognostic biomarkers identified by molecular analysis or DNA microarray gene profiling are promising, they too depend on invasive biopsy. Here, we test the hypothesis that combining information from biologically important intracellular molecules (biomarkers), noninvasively obtained by proton magnetic resonance spectroscopic imaging, will increase the diagnostic accuracy in determining the clinical grade of pediatric brain tumors. We evaluate the proton magnetic resonance spectroscopic imaging exams for 66 children with brain tumors. The intracellular biomarkers for choline-containing compounds (Cho), N-acetylaspartate, total creatine, and lipids and/or lactate were measured at the highest Cho region and normalized to the surrounding healthy tissue total creatine. Neuropathological grading was done with WHO criteria. Normalized Cho and lipids and/or lactate were elevated in high-grade (n = 23) versus low-grade (n = 43) tumors, which multiple logistic regression confirmed are independent predictors of tumor grade (for Cho, odds ratio 24.8, P < 0.001; and for lipids and/or lactate, odds ratio 4.4, P < 0.001). A linear combination of normalized Cho and lipids and/or lactate that maximizes diagnostic accuracy was calculated by maximizing the area under the receiver operating characteristic curve. Proton magnetic resonance spectroscopic imaging, although not a proxy for histology, provides noninvasive, in vivo biomarkers for predicting clinical grades of pediatric brain tumors.

Perfusion MR imaging of brain tumors

Brain tumors rank second as the cause of cancer-related deaths in children and adults younger than 34 years old, and they are seen in adults of all ages. Primary malignant brain tumors are associated with the third highest cancer-related mortality rate and a disproportionate level of disability and morbidity. Considering this, accurate diagnosis and grading of brain tumors are critical to determining prognosis and therapy. Equally important is to evaluate for tumor status during therapy to assess for therapeutic response and treatment-related complications. Brain tumors can be characterized as a heterogeneous group of neoplasm with a correspondingly wide variation in malignant phenotype and a diverse array of imaging features. Magnetic resonance (MR) imaging with intravenous contrast agent is the test of choice to diagnose and monitor brain tumors before, during, and after therapy. Recent advances in imaging methods such as diffusion-weighted imaging, perfusion imaging, and spectroscopic imaging all have in common the ability to provide quantitative cellular, hemodynamic, and metabolic information that may enhance our understanding of brain tumor biology, help us to better assess treatment response, more accurately determine tumor activity during therapy, and differentiate recurrent tumor and treatment related complications. In this article, we will review the basics of brain tumor imaging and focus on the role of perfusion MR imaging in improving accurate diagnosis and monitoring brain tumors during therapy. Both strengths and shortcomings of perfusion MR imaging over standard anatomic MR imaging will be discussed as will important pitfalls of the technique.

Advances in neurosurgical technique in the current management of brain tumors

Despite significant advances in anatomical and functional neuroimaging modalities (eg, magnetic resonance [MR] imaging [MRI], MR spectroscopy [MRS], diffusion and perfusion MR, functional MRI [fMRI], magnetic-source imaging [MSI], diffusion tensor imaging [DTI]) and neuronavigation techniques, intraoperatively obtained functional information remains of crucial importance to the neurosurgeon, especially when operating on tumors that are located in or adjacent to functional cortical sites and subcortical pathways. This article focuses on recent advances in the surgical management of of intracerebral tumors with special emphasis on intraoperative cortical and subcortical stimulation mapping methods, and the prognostic significance of surgery on patient outcome.

Proton magnetic resonance spectroscopy: clinical applications in patients with brain lesions

CONTEXT

Proton spectroscopy has been recognized as a safe and noninvasive diagnostic method that, coupled with magnetic resonance imaging techniques, allows for the correlation of anatomical and physiological changes in the metabolic and biochemical processes occurring within previously-determined volumes in the brain. There are two methods of proton magnetic resonance spectroscopy: single voxel and chemical shift imaging.

OBJECTIVE

The present work focused on the clinical applications of proton magnetic resonance spectroscopy in patients with brain lesions.

CONCLUSIONS

In vivo proton spectroscopy allows the detection of certain metabolites in brain tissue, such as N-acetyl aspartate, creatine, choline, myoinositol, amino acids and lipids, among others. N-acetyl aspartate is a neuronal marker and, as such, its concentration will decrease in the presence of aggression to the brain. Choline increase is the main indicator of neoplastic diseases. Myoinositol is raised in patients with Alzheimer's disease. Amino acids are encountered in brain abscesses. The presence of lipids is related to necrotic processes.

Gliomatosis cerebri: a review of 22 cases

OBJECTIVE

Gliomatosis cerebri is an enigmatic diffuse brain neoplasm whose prognosis is grim. We reviewed data for patients with gliomatosis who were treated at the University of California, San Francisco, during a 10-year period. Our focus was on presentation, radiological and pathological features, and outcomes.

METHODS

We reviewed hospital and clinic records and magnetic resonance imaging scans for 22 patients with gliomatosis. The diagnosis was based on magnetic resonance imaging findings and tissue confirmation for all patients. Seven patients also underwent magnetic resonance spectroscopy. Eleven patients were male (50%), and the median age at presentation was 49 years (range, 7-79 yr).

RESULTS

Kaplan-Meier analysis demonstrated median lengths of survival as follows: no treatment, 1 month (n = 4); radiotherapy alone, 28 months (95% confidence interval, 5-51 mo; n = 13); radiotherapy followed by chemotherapy, two patients, alive at 28 and 104 months; radiotherapy and chemotherapy simultaneously, three patients, one alive at 18 months and the others dead at 7 and 9 months. There was no significant difference between radiotherapy alone and radiotherapy combined with chemotherapy (P = 0.69). Karnofsky Performance Scale scores of >/=70 and grade were both significantly related to length of survival in univariate analyses (P < 0.05); these correlations were confirmed in the multivariate analysis, although the small numbers of patients and deaths precluded reliable interpretation.

CONCLUSION

Although the small number of patients in our study and its retrospective nature preclude definitive conclusions regarding the utility of treatment, our findings suggest that biopsies are useful not only for diagnosis but also for prediction of the length of survival.

1H MR spectroscopy of brain tumours and masses

Accurate diagnosis is essential for optimum management and treatment of patients with brain tumours. Proton magnetic resonance spectroscopy ((1)H MRS) provides information non-invasively on tumour biochemistry and has been shown to provide important additional information to that obtained by conventional radiology. We review the current status of (1)H MRS in classifying brain tumour type and grade, for monitoring response to therapy and progression to higher grade, and as a molecular imaging technique for determining tumour extent for treatment planning.

Glioma and multiple sclerosis: case report

We report a case of a 44-years-old woman with relapsing-remitting and secondarily progressive form of multiple sclerosis (MS) since aged 24 years, who developed an anaplastic astrocytoma. The neurological manifestations of the tumor were misinterpreted as resulting from MS. Sequential MRI examination and seizures raised the possibility of another nature of her symptoms, besides MS. Her initial good response to high doses corticosteroids led to the initial assumption her symptoms were only exclusively due to the demyelinating process. She underwent craniotomy with radical excision of the lesion. Pathological examination disclosed anaplastic astrocytoma. Other cases of coincidental MS and primary CNS tumors are reviewed, as well as their possible relation.

Proton MR spectroscopy in clinical routine

In vivo magnetic resonance spectroscopy (MRS) addresses metabolic pathways and their steady states in different tissue types. The brain has by tradition, and due to technical limitations in other organs, been one of the tissues most studied by MRS, and both 1H- and 31P-MRS have been used. Although 31P-MRS is outstanding for the evaluation of sources of metabolic energy in the brain, 1H-MRS has become the major clinically applied method in neurospectroscopy, as it provides information on markers of neuronal function, myelin, cell membranes, and metabolic active compounds. Furthermore, MR sensitivity is much greater for protons than it is for phosphorus and 1H-MRS, therefore allowing better spatial resolution. This review focuses on neurospectroscopy and diagnostic insights into diverse neurological problems provided by 1H-MRS applied as a clinical tool.

Time course of postoperative recovery of N-acetyl-aspartate in temporal lobe epilepsy

PURPOSE

To assess the time course of increases in N-acetyl-aspartate/creatine (NAA/Cr), which can be measured using proton MR spectroscopic imaging (1H-MRSI), in patients with intractable nonlesional temporal lobe epilepsy (TLE) after successful epilepsy surgery.

METHODS

We performed pre- and postoperative 1H-MRSI in 16 seizure-free (SF) patients and 16 not seizure-free (NSF) TLE patients. We calculated a mixed-design analysis of variance (ANOVA) between SF and NSF groups, ipsi- and contralateral to the side of operation, and pre- and postoperative NAA/Cr measurements. We applied nonlinear regression between pre- and postoperative NAA/Cr differences and the time interval between 1H-MRSI scans to fit a negative exponential model to NAA recovery.

RESULTS

Mixed-design ANOVA revealed that (a) postoperative NAA/Cr was significantly higher in SF than in NSF patients (p = 0.02) and that (b) in the SF group, postoperative NAA/Cr values were significantly higher than preoperative values (p < 0.05) and returned to the normal range in most patients. According to our nonlinear regression model, in SF patients, there was a 50% increase relative to preoperative NAA/Cr values after 5.8 months, whereas an improvement of 95% was reached after 25 months.

CONCLUSIONS

Our results extend preliminary observations of postoperative NAA recovery of SF patients by characterizing the time course of recovery as an exponential function with a half-time of approximately 6 months. The reversal of neuronal metabolic dysfunction remote from the epileptic focus may underlie the clinical observation of improvement of cognitive dysfunction after successful epilepsy surgery.

An automated technique for the quantitative assessment of 3D-MRSI data from patients with glioma

Although proton magnetic resonance spectroscopic imaging (1H-MRSI) has been shown to be effective for localizing tumor in patients with gliomas, it is not a routinely used clinical tool. This is due, in part, to the lack of a standardized, objective method for analyzing spectra. We present an automated technique for a) selecting a population of voxels from each patient that have the spectral features of normal brain regions, and b) using the selected voxels as internal controls for quantifying the probability of abnormality at each voxel location. The technique was demonstrated on a phantom, 14 normal volunteers, and 30 patients with histologically proven tumor. In addition, we demonstrated the usefulness of the method for monitoring patients in serial studies from two glioma patients with progressive disease.

Efficacy of proton magnetic resonance spectroscopy in clinical decision making for patients with suspected malignant brain tumors

We wished to determine the utility of single voxel proton (1H) magnetic resonance spectroscopy (MRS) when used as an alternative or adjunct to brain biopsy in patients harboring lesions suggestive of brain tumors identified by MRI scan. Fifteen patients (age 7-58 years) with MRI scans and clinical histories suggestive of primary brain tumors underwent single voxel 1H-MRS. MRS (16 regions of interest in 15 patients) was used to aid in differentiation between tumor and other pathologies such as stroke or demyelinating plaque (n = 6), radiation necrosis (n = 5), or edema (n = 5). Spectra were quantified to determine absolute molar values of N-acetyl aspartate (NAA), choline (Cho), creatine (Cr), lactate (LAC), and myo-inositol (mI), metabolite ratios relative to Cr were calculated, and spectra were interpreted based on metabolite ratios. Subsequent clinical management was based on MRS interpretation, and patients were then followed to determine if MRS interpretation accurately predicted clinical outcome or surgical findings. Mean follow-up was 12.5 months (range 3-28 months). MRS suggested the presence of recurrent tumor in 7 cases, all of which were subsequently 'confirmed' by tumor resection (n = 4) or disease progression (n = 3). MRS suggested the presence of new tumor in 1 case, subsequently confirmed by surgical resection. MRS suggested the presence of necrosis in 3 patients; all 3 remained radiographically stable during the follow-up period, and one was confirmed by stereotactic biopsy. MRS suggested non-neoplastic lesions in 4 cases, 3 of whom were followed until radiographic resolution of lesions and one of which was confirmed as a pyogenic abscess via stereotactic aspiration. Overall, MRS accurately predicted the pathological nature and clinical outcome of lesions in 15/16 (96%) situations, influenced clinical decision making in 12 cases, and altered surgery planning in 7 patients. In appropriate circumstances MRS can reduce the need for biopsy, and provide an important guide for clinical decision-making in difficult cases.

The role of magnetic resonance in the assessment of multiple sclerosis

Although the correlations between magnetic resonance imaging (MRI) findings and long-term disease evolution range from poor to moderate, conventional pre- and post-contrast MRI provides sensitive and reliable measures to monitor multiple sclerosis (MS) activity over time. MRI pulse sequences that have been recently introduced have shorter acquisition times and their use in large-scale studies can significantly decrease their costs in terms of both working load and patients' discomfort. The application of non-conventional techniques can increase the pathological specificity of MRI findings and, as a consequence, improve the relationship with the clinical evolution of the disease. These techniques also enable us to quantify the subtle abnormalities occuring in the so-called normal-appearing white matter, thus allowing a more accurate assessment of MS burden to be achieved. Some of these techniques have already shown their value for assessing MS dynamics, whereas other still need to go through a more complete validation process prior to any extensive clinical application in MS.

Magnetic resonance techniques to monitor disease evolution and treatment trial outcomes in multiple sclerosis

Although the correlations between magnetic resonance findings and long-term disease evolution range from poor to moderate, conventional precontrast and postcontrast magnetic resonance imaging provides sensitive and reliable measures to monitor multiple sclerosis activity over time. New pulse sequences with shorter acquisition times can be cost effective and reduce patients' discomfort. The application of other techniques that give more accurate estimates of disease burden and have higher pathological specificity might improve our understanding of multiple sclerosis evolution and provide new outcomes for monitoring clinical trials. Work is still needed to obtain optimal imaging of the spinal cord for multiple sclerosis diagnosis and monitoring.