Spectroscopic increase in choline signal is a nonspecific marker for differentiation of infective/inflammatory from neoplastic lesions of the brain

Multiparametric magnetic resonance imaging features of giant intracranial tuberculomas

OBJECTIVES

To evaluate Magnetic Resonance Imaging (MRI) features of Giant Tuberculomas (GT) of the brain and deduce characteristic imaging phenotypes which may differentiate GT from higher grade glioma.

METHODS

A retrospective analysis of MRI was done on Tuberculomas of size >2 cm. The diagnosis was established by histopathology or presumed from size reduction on follow-up MRI while on empirical anti-tubercular therapy (ATT). Multimodality characteristics of GT on T1/T2W, Fluid attenuation recovery (FLAIR), Diffusion-Weighted imaging (DWI), Susceptibility Weighted Imaging (SWI), Spectroscopy (MRS) and Perfusion weighted sequences were assessed. These imaging features were also evaluated in WHO Grade IV, IDH-wild type glioma (histopathologically and genetically proven) and a comparative analysis of the imaging features between GT and glioma was done.

RESULTS

Thirty-two GT and 20 glioma were evaluated. Pronounced intralesional T2 hypointensity (n = 8;25%), T2 hyperintense crescent beneath the periphery (n = 25, 78.1%), T2W lamellated/whorled appearance (n = 17;53.125%), hyperintense rim on T1W MT (n = 25;78.1%), peripheral rim of diffusion restriction (n = 22; 68.75%), peripheral rim of blooming on SWI (n = 20, 62.5%), prominent lipid resonance on MR spectroscopy (n = 30; 93.75%), overshoot of the signal intensity-time curve above the base line (n = 9/10; 90%) on dynamic susceptibility contrast (DSC) perfusion, were remarkable imaging characteristics. Reduction of peripheral T1 hyperintensity, compaction of T2 hypointense core, expansion of sub-marginal T2 hyperintense rim and increased peripheral susceptibility (n = 20; 62.5%) during follow-up imaging, while on ATT, were standout features. GT could be differentiated from WHO grade IV (IDH-wild type) glioma on the basis of a significantly higher proportion of GTs showing a whorled/lamellated appearance, T1 hyperintense rim, T2 hypointense core, DWI-ADC mismatch, well-defined rim on SWI, prominent lipid peak on MRS and a submarginal T2 hyperintense rim. GT showed a higher normalized ADC ratio from the core as well as the rim. Significantly higher proportion of glioma showed a T1 hypointense and T2 hyperintense core and a nodular rim enhancement. A significantly higher r CBV, Choline to creatine, choline to NAA ratio and mean thickness of the peripheral enhancing rim were defining features among gliomas.

CONCLUSION

Neuroimaging features of GT have been elucidated. Reduction of peripheral T1 hyperintensity, compaction of T2 hypointense core, expansion of sub-marginal T2 hyperintense rim, and increased peripheral susceptibility on follow-up may be considered imaging markers of response to anti-tubercular therapy. Multiparametric MRI features can differentiate GT from WHO grade IV (IDH-wild type) glioma.

Magnetic resonance imaging spectrum of intracranial tubercular lesions: one disease, many faces

Tuberculosis is a devastating disease and has shown resurgence in recent years with the advent of acquired immunodeficiency syndrome. Central nervous system involvement is the most devastating form of the disease, comprising 10% of all tuberculosis cases. The causative organism, Mycobacterium tuberculosis, incites a granulomatous inflammatory response in the brain, the effects of which can be appreciated on magnetic resonance imaging (MRI), which can thus be used for diagnosis of the same. Neurotuberculosis can present in various patterns, which can be identified on MRI. The meningeal forms include leptomeningitis and pachymeningitis. Parenchymal forms of neurotuberculosis include tuberculoma in its various stages, tubercular cerebritis and abscess, tubercular rhombencephalitis, and tubercular encephalopathy. Each pattern has characteristic MRI appearances and differential diagnoses on imaging. Complications of neurotuberculosis, usually of tubercular meningitis, include hydrocephalus, vasculitis, and infarcts as well as cranial nerve palsies. Various MRI sequences besides the conventional ones can provide additional insight into the disease, help in quantifying the disease load, and help in differentiation of neurotuberculosis from conditions with similar imaging appearances and presentations. These can enable accurate and timely diagnosis by the radiologist and early institution of treatment in order to reduce the likelihood of permanent neurological sequelae.

Intradural Juvenile Xanthogranuloma with Involvement of Multiple Nerve Roots: A Case Report and Review of the Literature

BACKGROUND

Juvenile xanthogranuloma (JXG) is a rare, non-Langerhans cell histiocytic disorder that primarily presents as multiple cutaneous lesions in young males. Solitary lesions in the spinal column are an especially rare presentation of this disease, and central nervous system involvement can portend a poor prognosis. We report an unusual case of an adult woman with an unresectable JXG of the lumbar spine. A review of the reported cases of thoracolumbar JXG and the current data regarding diagnosis and treatment are presented.

CASE DESCRIPTION

A 28-year-old woman presented with back pain and worsening lower extremity pain, numbness, and weakness. Magnetic resonance imaging demonstrated an enhancing lumbar mass. However, at surgery, no discrete mass was identified. Multiple roots were grossly enlarged, and electrical stimulation identified the L4 root with the most abnormal findings. Despite an attempt at debulking, most of the mass could not be safely removed. The patient experienced incomplete improvement of the symptoms postoperatively but elected to forgo chemotherapy. The 3-month follow-up imaging study showed active lumbar spinal disease, and imaging and follow-up examinations at 27 months revealed no changes. Her symptoms were satisfactorily controlled with conservative therapy.

CONCLUSIONS

JXG of the spine is a rare disease with nonspecific clinical and radiographic findings that can make it difficult to diagnose and dictates the use of immunohistochemical staining. If possible, total surgical resection will offer the best outcomes; however, other modalities such as chemotherapy can be viable alternatives or adjuvant modalities.

Evaluation of intracranial tuberculomas using diffusion-weighted imaging (DWI), magnetic resonance spectroscopy (MRS) and susceptibility weighted imaging (SWI)

OBJECTIVE:

The present study was aimed to evaluate patients of suspected intracranial tuberculomas with diffusion-weighted imaging (DWI), magnetic resonance spectroscopy (MRS) and susceptibility-weighted imaging (SWI).

METHODS:

The present study evaluated 116 patients known or suspected of having central nervous system tuberculosis with advanced MRI techniques comprising of DWI, MRS and SWI in addition to the conventional MRI.

RESULTS:

Apparent diffusion coefficient value of tuberculomas was not significantly different (p > 0.05) from apparent diffusion coefficient value of metastatic lesions and high-grade gliomas. MRS revealed that NAA/Cr and NAA/Cho ratios of tuberculomas were not significantly different (p > 0.05) from that of malignant brain lesions. However, Cho/Cr ratio of tuberculomas (1.36 ± 0.41) was significantly lower from that of malignant brain lesions (2.63 ± 0.99). SWI revealed a complete and regular hypointense peripheral ring in 42 cases of tuberculomas (58%) and in none of the malignant brain lesions.

CONCLUSION:

DWI offers no clear advantage in differentiating tuberculomas from metastasis and gliomas. Tuberculomas may be differentiated from metastases and gliomas by their unique metabolite pattern on MRS. Presence of a complete and regular peripheral hypointense ring in SWI favors the diagnosis of tuberculomas.

ADVANCES IN KNOWLEDGE:

The results from the present study suggest promising role of SWI in the discrimination of tuberculomas from metastatic brain lesions and gliomas with the presence of a complete and regular peripheral hypointense ring favoring the diagnosis of tuberculomas.

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.

Characterisation of musculoskeletal tumours by multivoxel proton MR spectroscopy

OBJECTIVE

The purpose of this study is to evaluate the role of multi-voxel proton MR spectroscopy in differentiating benign and malignant musculoskeletal tumours in a more objective way and to correlate the MRS data parameters with histopathology.

METHODS AND MATERIALS

A hospital-based prospective study was carried out comprising 42 patients who underwent MRI examinations from 1 July 2013 to 30 June 2014. After routine sequences, single-slice multi-voxel proton MR spectroscopy was included at TE-135 using the PRESS sequence. The voxel with the maximum choline/Cr ratio was used for analysis of data in 32 patients. The strength of association between the MR spectroscopy findings and the nature of tumour and histopathological grading were assessed.

RESULTS

Of the 42 patients, the MR spectra were not of diagnostic quality in 10. In the remaining 32 patients, 12 (37.5%) had benign and 20 (62.5%) malignant tumours. The mean choline/Cr ratio was 6.97 ± 5.95 (SD) for benign tumours and 25.39 ± 17.72 (SD) for malignant tumours. In our study statistical significance was noted between the choline/Cr ratio and the histological nature of musculoskeletal tumours (p = 0.002) assessed by unpaired t-test. The choline/Cr ratio and histological grading were also found to be significant (p = 0.001) when assessed by one-way ANOVA test.

CONCLUSIONS

Multi-voxel MR spectroscopy showed a higher choline/Cr ratio in malignant musculoskeletal tumours than in benign ones (p = 0.002). The choline/Cr ratio and histological grading of musculoskeletal tumours also showed statistical significance (p = 0.001).

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.

MR spectroscopy of intracranial tuberculomas: A singlet peak at 3.8 ppm as potential marker to differentiate them from malignant tumors

PURPOSE

The diagnosis of intracranial tuberculomas is often challenging. Our purpose is to describe the most common metabolic patterns of tuberculomas by MR spectroscopy (MRS) with emphasis on potential specific markers.

METHODS

Single-voxel MRS short echo time was performed in 13 cases of tuberculomas proven by histology and/or response to anti-mycobacterial therapy. For comparison MRS was also performed in 19 biopsy-proven malignant tumors (13 high-grade gliomas and six metastasis). Presence of metabolic peaks was assessed visually and categorical variables between groups were compared using chi-square. Metabolite ratios were compared using Mann-Whitney test and diagnostic accuracy of the metabolite ratios was compared using receiver-operating characteristic (ROC) curves analysis.

RESULTS

Spectroscopic peaks representing lipids and glutamate/glutamine (Glx) as well as a peak at ∼3.8 ppm were well defined in 77% (10/13), 77% (10/13) and 69% (nine of 13) of tuberculomas, respectively. Lipid and Glx peaks were also present in most of the malignant lesions, 79% (15/19) and 74% (14/19) respectively. However, a peak at ∼3.8 ppm was present in only 10% (two of 19) of the tumor cases (p < 0.001). Higher Cho/Cr and mI/Cr ratios helped discriminate malignant lesions with an area under the ROC curve of 0.86 (SE: 0.078, p < 0.002, CI: 0.7-1) and 0.8 (SE: 0.1, p < 0.009, CI: 0.6-1), respectively. Threshold values between 1.7-1.9 for Cho/Cr and 0.8-0.9 for mI/Cr provided high specificity (91% for both metabolites) and adequate sensitivity (75% and 80%, respectively) for discrimination of malignant lesions.

CONCLUSION

A singlet peak at ∼3.8 ppm is present in the majority of tuberculomas and absent in most malignant tumors, potentially a marker to differentiate these lesions. The assignment of the peak is difficult from our analysis; however, guanidinoacetate (Gua) is a possibility. Higher Cho/Cr and mI/Cr ratios should favor malignant lesions over tuberculomas. The presence of lipids and Glx is non-specific.

Combining diffusion tensor imaging and magnetic resonance spectroscopy to study reduced frontal white matter integrity in youths with family histories of substance use disorders

Individuals with a family history of substance use disorder (FH+) show impaired frontal white matter as indicated by diffusion tensor imaging (DTI). This impairment may be due to impaired or delayed development of myelin in frontal regions, potentially contributing to this population's increased risk for developing substance use disorders. In this study, we examined high angular resolution DTI and proton magnetic resonance spectroscopy data from the anterior corona radiata were collected in 80 FH+ and 34 FH- youths (12.9 ± 1.0 years old). White matter integrity indices included fractional anisotropy (FA), N-acetylaspartate (NAA), and total choline (tCho). Lower FA suggests decreased myelination. Decreased NAA coupled with higher tCho suggests impaired build-up and maintenance of cerebral myelin and consequently greater breakdown of cellular membranes. We found FH+ youths had lower FA (P < 0.0001) and NAA (P = 0.017) and higher tCho (P = 0.04). FH density (number of parents and grandparents with substance use disorders) was negatively correlated with FA (P < 0.0001) and NAA (P = 0.011) and positively correlated with tCho (P = 0.001). FA was independently predicted by both FH density (P = 0.006) and NAA (P = 0.002), and NAA and tCho were both independent predictors of FH density (P < 0.001). Our finding of lower frontal FA in FH+ youths corresponding to lower NAA and increased tCho is consistent with delayed or impaired development of frontal white matter in FH+ youths. Longitudinal studies are needed to determine how these differences relate to substance use outcomes.

Central nervous system tuberculosis

Tuberculosis (TB) has shown a resurgence in nonendemic populations in recent years and accounts for 8 million deaths annually in the world. Central nervous system involvement is one of the most serious forms of this infection, acting as a prominent cause of morbidity and mortality in developing countries. The rising number of cases in developed countries is mostly attributed to factors such as the pandemic of acquired immunodeficiency syndrome and increased migration in a globalized world. Mycobacterium TB is responsible for almost all cases of tubercular infection in the central nervous system. It can manifest in a variety of forms as tuberculous meningitis, tuberculoma, and tubercular abscess. Spinal infection may result in spondylitis, arachnoiditis, and/or focal intramedullary tuberculomas. Timely diagnosis of central nervous system TB is paramount for the early institution of appropriate therapy, because delayed treatment is associated with severe morbidity and mortality. It is therefore important that physicians and radiologists understand the characteristic patterns, distribution, and imaging manifestations of TB in the central nervous system. Magnetic resonance imaging is considered the imaging modality of choice for the study of patients with suspected TB. Advanced imaging techniques including magnetic resonance perfusion and diffusion tensor imaging may be of value in the objective assessment of therapy and to guide the physician in the modulation of therapy in these patients.

Brain proton magnetic resonance spectroscopy of alcohol use disorders

This chapter critically reviews brain proton magnetic resonance spectroscopy ((1)H MRS) studies performed since 1994 in individuals with alcohol use disorders (AUD). We describe the neurochemicals that can be measured in vivo at the most common magnetic field strengths, summarize our knowledge about their general brain functions, and briefly explain some basic human (1)H MRS methods. Both cross-sectional and longitudinal research of individuals in treatment and of treatment-naïve individuals with AUD are discussed and interpreted on the basis of reported neuropathology. As AUDs are highly comorbid with chronic cigarette smoking and illicit substance abuse, we also summarize reports on their respective influences on regional proton metabolite levels. After reviewing research on neurobiologic correlates of relapse and genetic influences on brain metabolite levels, we finish with suggestions on future directions for (1)H MRS studies in AUDs. The review demonstrates that brain metabolic alterations associated with AUDs as well as their cognitive correlates are not simply a consequence of chronic alcohol consumption. Future MR research of AUDs in general has to be better prepared - and supported - to study clinically complex relationships between personality characteristics, comorbidities, neurogenetics, lifestyle, and living environment, as all these factors critically affect an individual's neurometabolic profile. (1)H MRS is uniquely positioned to tackle these complexities by contributing to a comprehensive biopsychosocial profile of individuals with AUD: it can provide non-invasive biochemical information on select regions of the brain at comparatively low overall cost for the ultimate purpose of informing more efficient treatments of AUDs.

Recognition of anaplastic foci within low-grade gliomas using MR spectroscopy

BACKGROUND

The recognition of anaplastic foci within low-grade gliomas is of extreme importance in patients under follow-up for Grade II gliomas. We present the algorithm of MR spectroscopy (MRS)-guided brain biopsy and its correlation with tumour histology.

METHODS

Twenty-seven patients harbouring suspected Grade II/III glioma were examined on our 3T MR. 2D PRESS-CSI metabolite images of Choline/Creatine, Creatine/N-acetylaspartate and Choline/N-acetylaspartate were calculated and exported to the DICOM format. According to these maps, a stereobiopsy was performed at the point of maximum Choline/Creatine ratio prior to tumour resection. In the case of enhancing tumour, a subsequent biopsy was performed from the point of enhancement. Comparisons were made between the histology of the biopsied specimens and the resected tumours.

RESULTS

Eleven tumours were diagnosed as high-grade and sixteen as low-grade lesions. The correlation between main spectroscopic ratios (Cho/Cr and Cho/NAA) was strongly positive at the points of maximum Cho/Cr. Similar results were obtained at the points of contrast enhancement. Comparison of histological parameters of biopsy samples at the points of maximum Cho/Cr and histological examination of the completely resected tumours gives a strong correlation of tumour grade, number of mitoses and Ki-67 expression. The diagnostic accuracy of MRS-guided biopsy was 84%. The absolute value of Cho/NAA was higher in high-grade compared to that of low-grade lesions. The value of Cho/NAA ratio of 0.9 using MRS produced a sensitivity and specificity of 78% in the differentiation between low-grade and high-grade lesions. Combining MRS with structural MR, the sensitivity increased to 86% and the specificity to 80%.

CONCLUSIONS

Strong correlation was demonstrated between Cho/Cr and Ch/NAA ratios. Strong correlation was demonstrated between histological parameters of biopsy samples taken using Cho/Cr ratio and those from total tumour examination. Diagnostic accuracy of MRS-guided biopsy was 84%. Sensitivity and specificity of MRS combined with structural MR reaches 86% and 80%.

(1)H-NMR spectroscopy revealed Mycobacterium tuberculosis caused abnormal serum metabolic profile of cattle

To re-evaluate virulence of Mycobacterium tuberculosis (M. tb) in cattle, we experimentally infected calves with M. tb andMycobacterium bovisvia intratracheal injection at a dose of 2.0×10⁷ CFU and observed the animals for 33 weeks. The intradermal tuberculin test and IFN-γin vitro release assay showed that both M. tb and M. bovis induced similar responses. Immunohistochemical staining of pulmonary lymph nodes indicated that the antigen MPB83 of both M. tb and M. bovis were similarly distributed in the tissue samples. Histological examinations showed all of the infected groups exhibited neutrophil infiltration to similar extents. Although the infected cattle did not develop granulomatous inflammation, the metabolic profiles changed significantly, which were characterized by a change in energy production pathways and increased concentrations of N-acetyl glycoproteins. Glycolysis was induced in the infected cattle by decreased glucose and increased lactate content, and enhanced fatty acid β-oxidation was induced by decreased TG content, and decreased gluconeogenesis indicated by the decreased concentration of glucogenic and ketogenic amino acids promoted utilization of substances other than glucose as energy sources. In addition, an increase in acute phase reactive serum glycoproteins, together with neutrophil infiltration and increased of IL-1β production indicated an early inflammatory response before granuloma formation. In conclusion, this study indicated that both M. tb and M.bovis were virulent to cattle. Therefore, it is likely that cattle with M. tb infections would be critical to tuberculosis transmission from cattle to humans. Nuclear magnetic resonance was demonstrated to be an efficient method to systematically evaluate M. tb and M. bovi sinfection in cattle.

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.

Relationship between fractional anisotropy of cerebral white matter and metabolite concentrations measured using (1)H magnetic resonance spectroscopy in healthy adults

Fractional anisotropy (FA) of water diffusion in cerebral white matter (WM), derived from diffusion tensor imaging (DTI), is a sensitive index of microscopic WM integrity. Physiological and metabolic factors that explain intersubject variability in FA values were evaluated in two cohorts of healthy adults of different age spans (N=65, range: 28-50years; and N=25, age=66.6±6.2, range: 57-80years). Single voxel magnetic resonance spectroscopy (MRS) was used to measure N-acetylaspartate (NAA), total choline-containing compounds, and total creatine, bilaterally in an associative WM tract: anterior corona radiata (ACR). FA values were calculated for the underlying, proximal and two distal WM regions. Two-stage regression analysis was used to calculate the proportion of variability in FA values explained by spectroscopy measurements, at the first stage, and subject's age, at the second stage. WM NAA concentration explained 23% and 66% of intersubject variability (p<0.001) in the FA of the underlying WM in the younger and older cohorts, respectively. WM NAA concentration also explained a significant proportion of variability in FA of the genu of corpus callosum (CC), a proximal WM tract where some of the fibers contained within the spectroscopic voxel decussate. NAA concentrations also explained a significant proportion of variability in the FA values in the splenium of CC, a distal WM tract that also carries associative fibers, in both cohorts. These results suggest that MRS measurements explained a significant proportion of variability in FA values in both proximal and distal WM tracts that carry similar fiber-types.

(1)H MR spectroscopy with external reference solution at 1.5 T for differentiating malignant and benign breast lesions: comparison using qualitative and quantitative approaches

OBJECTIVE

To compare the diagnostic capability of proton ((1)H) magnetic resonance spectroscopy (MRS) in differentiating benign from malignant breast lesions on the basis of qualitative and quantitative approaches.

METHODS

We performed single-voxel (1)H MRS for 208 breast lesions, identified a clear total composite choline compounds (tCho) peak of signal-to-noise of ≥2 to represent malignancy (qualitative approach), and regarded tCho concentration equal to or greater than the cut-off value to represent malignancy (quantitative approach). We compared the diagnostic ability of both approaches using the Akaike information criterion (AIC) and McFadden's R (2).

RESULTS

Histologically, 169 lesions were malignant; 39 were benign. The qualitative approach demonstrated 84.6 % sensitivity and 51.3 % specificity for differentiating malignant and benign lesions. The mean tCho concentration was 1.13 mmol/kg for malignancy, 0.43 mmol/kg for benignity. The optimal cut-off point was 0.61 mmol/kg, use of which achieved 68.1 % sensitivity and 79.4 % specificity. Calculated AIC and R (2) score suggested the superiority of the quantitative approach for differentiating malignancy.

CONCLUSIONS

Quantitative MRS provides higher specificity than qualitative MRS for differentiating malignant from benign lesions and could be more useful as an additional examination in routine breast MR imaging.

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.

Invasive intracranial aspergillosis: the management dilemmas

BACKGROUND

Invasive intracranial aspergillosis remains a disease with high morbidity and mortality. The rapid increase in the incidence of this disease led us to review the literature and formulate a treatment protocol for such patients.

METHODS

An analysis of 46 patients with invasive intracranial aspergillosis is presented and the subgroups of extradural and intradural variety are evaluated with different treatment strategies.

RESULTS

Patients with extradural form of disease had 100% survival, whereas antifungal chemotherapy preloading tends to provide a better outcome.

CONCLUSIONS

Extradural aspergillosis does not need chemotherapy preloading, whereas intradural variant may have improved survival chances after preloading. Liposomal formulation has an advantage of shortened time duration for preloading, because the daily administration dose is 6 times higher than conventional preparation.

Multivoxel MR Spectroscopic Imaging – Distinguishing Intracranial Tumours from Non-neoplastic Disease

Introduction: Multi-voxel MR spectroscopic imaging (MRSI) provides chemical metabolite information that can supplement conventional MR imaging in the study of intracranial neoplasia. Our purpose was to use a robust semi-automated spectroscopic analysis to distinguish intracranial tumours from non-neoplastic disease. Materials and Methods: Twenty intracranial tumours and 15 patients with non-neoplastic disease confirmed on histological examination or serial neuroimaging were studied with 2-dimensional MRSI using point-resolved spectroscopic (PRESS) imaging localisation. Using semi-automated post-processing software, spectra were analysed for peak heights of choline (Cho), creatine (Cr), N-acetyl aspartate (NAA), lactate (Lac) and lipid (Lip). Normalised Cho (nCho) ratios, computed by dividing maximum Cho in the lesion by the normal-appearing brain, were compared between intracranial tumours and non-neoplastic disease. Results: Meningiomas displayed homogenously elevated Cho. Malignant tumours, especially large glioblastoma multiforme, displayed inhomogeneity of metabolites within the tumour. All tumours had elevation of nCho >1 (mean 1.91 ± 0.65), and non-neoplastic diseases had tumour nCho <1 (mean 0.91 ± 0.46), which was significantly lower (P <0.05). Two patients with non-neoplastic lesions, one with subacute cerebral infarction and the other with cryptococcoma, had elevated Cho compared to normal tissue (false positive rate 13%). Conclusion: Using semi-automated MRSI method, a simplified normalised Cho algorithm provides a method to distinguish intracranial tumours from non-neoplastic disease. Key words: Brain neoplasm, Magnetic resonance imaging, Nuclear magnetic resonance, Spectroscopy

In vivo proton spectroscopy of giant cell tumor of the bone

OBJECTIVE

The proton MR spectroscopic finding of elevated choline has been reported to be useful in the differentiation of malignant from benign musculoskeletal tumors. This study was designed to evaluate the MR spectroscopy features of giant cell tumor (GCT) of the bone, primarily to determine whether the presence of choline is a frequent occurrence in these tumors and whether MR spectroscopy features can be correlated with clinical, radiologic, and histopathologic findings.

SUBJECTS AND METHODS

MRI, dynamic contrast-enhanced MRI, and proton MR spectroscopy were performed in 33 patients with bone tumors on a 1.5-T MR scanner. Of these, 12 patients who had GCT of the bone form the subject material for this study. Dynamic contrast-enhanced MRI and single-voxel proton MR spectroscopy were performed after preliminary evaluation with radiography. Patients were divided into two groups, those with elevated choline levels and those without a choline peak on MR spectroscopy. The clinical and radiologic features, including the Campanacci stage and dynamic MRI findings, were compared in these two groups. Core biopsy was performed in all patients, and in 10 of 12 patients, histopathologic evaluation of the postoperative resected specimen was also performed.

RESULTS

Although all 12 tumors were benign on histopathology, four had elevated choline levels. Of these, three (75%) had an aggressive radiographic appearance (Campanacci stage 3). As opposed to this, only three of the eight (37.5%) tumors without a choline peak had an aggressive radiographic appearance. Except for a single case, all tumors showed early enhancement and washout of contrast material on dynamic MRI.

CONCLUSION

The results of this study indicate that GCT of bone may show raised choline levels on proton MR spectroscopy. This finding is not an indicator of malignancy in these tumors.

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.

Differentiating intracranial aspergillosis from a high grade glioma using MRI and MR spectroscopic imaging

We compare the MRI (magnetic resonance imaging) and MRSI (MR spectroscopic imaging) findings in a patient with intracerebral aspergillosis to those typically seen in an infiltrating high-grade glioma (HGG). We demonstrate paramagnetic areas of T2-hypointensity due to the pathologic deposition of iron and other paramagnetic elements seen in intracerebral aspergillosis. We also demonstrate the diffusion-weighted imaging (DWI) findings and discuss how MR spectroscopy can be useful in differentiating an aspergilloma from a high-grade glioma.

Relative cerebral blood volume is a measure of angiogenesis in brain tuberculoma

OBJECTIVE

The aim of this study was to correlate the perfusion indices with magnetic resonance imaging-derived cellular and necrotic fraction of the tuberculoma and angiogenesis metrics on histopathology.

METHODS

We performed dynamic contrast-enhanced magnetic resonance imaging in 13 excised brain tuberculoma patients. Microvascular density and vascular endothelial growth factor (VEGF)-expressing cells were quantified from the excised tuberculoma. The cellular and necrotic fractions of the tuberculomas were quantified on a postcontrast T1-weighted imaging.

RESULTS

Relative cerebral blood volume of cellular portion significantly correlated with cellular fraction volume (r = 0.882, P < 0.001), microvascular density (r = 0.900, P < 0.001), and VEGF (r = 0.886, P < 0.001) of the 13 excised tuberculomas. Microvascular density also correlated significantly with VEGF (r = 0.919, P < 0.001).

CONCLUSIONS

Relative cerebral blood volume is a measure of angiogenesis in the cellular fraction of the brain tuberculoma. This information may be of value in predicting the therapeutic response in future.

Recent advances in magnetic resonance neurospectroscopy

Over the past two decades, proton magnetic resonance spectroscopy (proton MRS) of the brain has made the transition from research tool to a clinically useful modality. In this review, we first describe the localization methods currently used in MRS studies of the brain and discuss the technical and practical factors that determine the applicability of the methods to particular clinical studies. We also describe each of the resonances detected by localized solvent-suppressed proton MRS of the brain and discuss the metabolic and biochemical information that can be derived from an analysis of their concentrations. We discuss spectral quantitation and summarize the reproducibility of both single-voxel and multivoxel methods at 1.5 and 3-4 T. We have selected three clinical neurologic applications in which there has been a consensus as to the diagnostic value of MRS and summarize the information relevant to clinical applications. Finally, we speculate about some of the potential technical developments, either in progress or in the future, that may lead to improvements in the performance of proton MRS.

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.

Identification of diffuse and focal brain lesions by clinical magnetic resonance spectroscopy

The purpose of this paper is to facilitate the comparison of magnetic resonance (MR) spectra acquired from unknown brain lesions with published spectra in order to help identify unknown lesions in clinical settings. The paper includes lists of references for published MR spectra of various brain diseases, including pyogenic abscesses, encephalitis (herpes simplex, Rasmussen's and subacute sclerosing panencephalitis), neurocysticercosis, tuberculoma, cysts (arachnoid, epidermoid and hydatid), acute disseminated encephalomyelitis (ADEM), adrenoleukodystrophy (ALD), Alexander disease, Canavan's disease, Krabbe disease (globoid cell leukodystrophy), Leigh's disease, megalencephalic leukoencephalopathy with cysts, metachromatic leukodystrophy (MLD), Pelizaeus-Merzbacher disease, Zellweger syndrome, HIV-associated lesions [cryptococcus, lymphoma, toxoplasmosis and progressive multifocal leukoencephalopathy (PML)], hydrocephalus and tuberous sclerosis. Each list includes information on the echo time(s) (TE) of the published spectra, whether a control spectrum is shown, whether the corresponding image and voxel position are shown and the patient ages if known. The references are listed in the approximate order of usefulness, based on spectral quality, number of spectra, range of echo times and whether the voxel positions are shown. Spectra of Zellweger syndrome, cryptococcal infection, toxoplasmosis and lymphoma are included, along with a spectrum showing propanediol (propylene glycol).

Brain magnetic resonance spectroscopy in Tourette's disorder

OBJECTIVE

Although abnormalities of neural circuits involving the cortex, striatum, and thalamus are hypothesized to underlie Tourette's disorder, the neuronal abnormalities within components of these circuits are unknown. The purpose of this study was to examine the cellular neurochemistry within these circuits in Tourette's disorder using proton magnetic resonance spectroscopy, a method that has not previously been used in neurobiological investigations of the disorder.

METHOD

Proton magnetic resonance spectroscopic imaging examinations were conducted in 25 males with Tourette's disorder (age 10.9 +/- 2.0 years) and 32 male comparison subjects (age 11.5 +/- 2.7 years). Spectra from frontal cortex, caudate nucleus, putamen, and thalamus were analyzed, and N-acetylaspartate, creatine, choline, myoinositol, and glutamate + glutamine were quantified and compared between the groups.

RESULTS

Patients with Tourette's disorder demonstrated a reduction in N-acetylaspartate and choline in the left putamen, along with reduced levels of creatine bilaterally in the putamen. In the frontal cortex, patients had significantly lower concentrations of N-acetylaspartate bilaterally, lower levels of creatine on the right side, and reduced myoinositol on the left side.

CONCLUSIONS

The results of this study suggest compromised neuronal integrity and deficits in density of neuronal and nonneuronal cells in components of the neural circuits implicated in Tourette's disorder.

Proton MR spectroscopy of the brain with a focus on chemical issues

Among the vast number of metabolites in living tissues, metabolites detectable by in vivo MR spectroscopy are limited to those present in high concentrations, and the actual number is only 10 to 20. None is disease-specific. Interpretation of MRS data, therefore, must be based on general knowledge of biochemical processes in association with pathological changes. Each spectrum is a window on the actual biochemical changes taking place within the living tissues, but the reality entails a wide and confusing variance. Continuous expansion of the knowledge may reduce the uncertainty of interpreting MRS data.

Cerebral aspergillosis due to Aspergillus fumigatus in AIDS patient: first culture - proven case reported in Brazil

Cerebral aspergillosis is a rare cause of brain expansive lesion in AIDS patients. We report the first culture-proven case of brain abscess due to Aspergillus fumigatus in a Brazilian AIDS patient. The patient, a 26 year-old male with human immunodeficiency virus (HIV) infection and history of pulmonary tuberculosis and cerebral toxoplasmosis, had fever, cough, dyspnea, and two episodes of seizures. The brain computerized tomography (CT) showed a bi-parietal and parasagittal hypodense lesion with peripheral enhancement, and significant mass effect. There was started anti-Toxoplasma treatment. Three weeks later, the patient presented mental confusion, and a new brain CT evidenced increase in the lesion. He underwent brain biopsy, draining 10 mL of purulent material. The direct mycological examination revealed septated and hyaline hyphae. There was started amphotericin B deoxycholate. The culture of the material demonstrated presence of the Aspergillus fumigatus. The following two months, the patient was submitted to three surgeries, with insertion of drainage catheter and administration of amphotericin B intralesional. Three months after hospital admission, his neurological condition suffered discrete changes. However, he died due to intrahospital pneumonia. Brain abscess caused by Aspergillus fumigatus must be considered in the differential diagnosis of the brain expansive lesions in AIDS patients in Brazil.

Granulomatous diseases of the central nervous system

Infectious diseases of the central nervous system (CNS), particularly those accompanied by the formation of granulomas, are a constant diagnostic challenge in some specific regions of the world, above all in developing countries. The pattern of image seen on CT or MR scan is the result of the inter-relations between the individual characteristics of the infectious agent and the capacity of each host to mount an appropriate inflammatory response to that specific type of aggression, inside one particular compartment of the CNS. Taking these parameters into account we will discuss the several patterns of image found in parasitic, bacterial, and fungal granulomatous infections.

The nonspecific nature of proton spectroscopy in brain masses in children: a series of demyelinating lesions

MRI imaging has significantly improved the detection of brain lesions over the past few decades. It has high sensitivity to intracranial pathology but confident preoperative tissue diagnosis is relatively unusual. MR spectroscopy provides in-vivo biochemical information and has been used to improve the low specificity of tumour diagnosis. During the last decade there have been a number of reports making the case that proton spectroscopy can distinguish different grades of glial tumours and in some situations provide information on histological type. We report four children who presented with neurological symptoms and focal masses on MRI. MRS in each of them gave results consistent with textbook descriptions of malignancy, but in all four cases the abnormalities were subsequently shown to be due to demyelination. We reiterate that spectroscopic appearances are nonspecific and spectroscopic data should be evaluated in the light of concurrent imaging features and the clinical presentation.

Proton magnetic resonance spectroscopy of basal ganglia in chronic fatigue syndrome

Fatigue is a common symptom of neurological diseases that affect basal ganglia function. We used proton magnetic resonance spectroscopy ((1)H MRS) to study the metabolic functions of the basal ganglia in chronic fatigue syndrome (CFS) to test the hypothesis that fatigue in CFS may have a neurogenic component. (1)H MRS of left basal ganglia was carried out in eight non-psychiatric patients with CFS and their results were compared to age- and sex-matched healthy asymptomatic healthy controls. A highly significant increase in the spectra from choline-containing compounds was seen in the CFS patient group (p < 0.001). In the absence of regional structural or inflammatory pathology, increased choline resonance in CFS may be an indicator of higher cell membrane turnover due to gliosis or altered intramembrane signalling.

Differentiation of hydatid cyst from cysticercus cyst by proton MR spectroscopy

The metabolite patterns obtained by ex vivo proton MR spectroscopy of fluid from different locations of hydatid cysts of sheep and humans (n = 16) and cysticercus cysts of swine and humans (n = 25) were compared with an objective of differentiating the two parasites on the basis of their metabolite pattern. The spectra from hydatid fluid differed from cysticercus cyst by the absence of creatine in the former. When the hydatid cyst was fertile, malate and/or fumarate was also observed, which was absent in cysticercus cyst. The most likely explanation for the presence of creatine only in the cysticercus fluid is its active diffusion from the surrounding host tissue along with a contribution from the musculature present in the bladder wall of the cyst.

Comparative evaluation of magnetization transfer MR imaging and in-vivo proton MR spectroscopy in brain tuberculomas

We have compared and analyzed the value of in vivo proton MR spectroscopy (PMRS) and T1 weighted magnetization transfer (MT) MR imaging in tissue characterization of brain tuberculomas. We studied 33 cases of proven intracranial tuberculomas with in vivo PMRS and T1 weighted MT MR imaging. MT ratios from the rim and core of the tuberculomas were calculated and compared with metabolites seen on PMRS. Final diagnosis of tuberculoma was based on histopathology (n = 26) and/or associated tuberculous meningitis (n = 7) in all the cases. Out of the 33 patients who underwent both PMRS and T1 weighted MT MR imaging, spectroscopy showed only lipids at 0.9 ppm, 1.3 ppm, 2.0 ppm, and 2.80 ppm in 26 cases while lipids at 0.9 ppm, 1.3 ppm, 2.0 ppm and 2.80 ppm along with choline at 3.22 ppm was seen in remaining 7 patients. MT ratios from the core or solid necrosis varied from 21-29% while from the rim or cellular region varied from 16-24%. MT ratios from all the 33 lesions were consistent with tuberculomas while PMRS showed choline along with lipids in 7 predominantly cellular lesions simulating a neoplasm. We conclude that T1 weighted MT MR imaging appears to be more consistent in the tissue characterization of brain tuberculomas.

The potential of proton magnetic resonance spectroscopy ((1)H-MRS) in the diagnosis and management of patients with brain tumors

Proton ((1)H) magnetic resonance spectroscopy (MRS) is a noninvasive method that can monitor the metabolic changes in most brain diseases. This technique is now available on current 1.5 Tesla magnetic resonance units and does not require sophisticated software or time-consuming post-processing techniques. Previous studies using single-voxel techniques showed the usefulness of MRS for the diagnosis of brain tumor despite some technical issues, including spatial resolution and volume coverage. Recent advances have been made through the use of multivoxel techniques and metabolite maps, which allow assessment of both the entire volume of the lesion and the surrounding normal-appearing brain tissue. Recent studies suggest the potential of this technique to guide biopsies, to define radiotherapy targets, and to monitor patients after treatment. Some persistent drawbacks, including measurement time and spectral resolution, will probably be overcome in the near future.