The clinical value of proton magnetic resonance spectroscopy in adult brain tumours

A historical overview of magnetic resonance imaging, focusing on technological innovations

Magnetic resonance imaging (MRI) has now been used clinically for more than 30 years. Today, MRI serves as the primary diagnostic modality for many clinical problems. In this article, historical developments in the field of MRI will be discussed with a focus on technological innovations. Topics include the initial discoveries in nuclear magnetic resonance that allowed for the advent of MRI as well as the development of whole-body, high field strength, and open MRI systems. Dedicated imaging coils, basic pulse sequences, contrast-enhanced, and functional imaging techniques will also be discussed in a historical context. This article describes important technological innovations in the field of MRI, together with their clinical applicability today, providing critical insights into future developments.

Preoperative magnetic resonance spectroscopy improves diagnostic accuracy in a series of neurosurgical dilemmas

OBJECT

The purpose of this study was to evaluate the usefulness of preoperative magnetic resonance spectroscopy (MRS) in neurosurgical patients with diagnostically challenging intracranial lesions.

METHODS

Included in this study are twenty-three consecutive patients presenting to the neurosurgery service with diagnostically challenging intracranial lesions and who were investigated by conventional MR imaging and proton ((1)H) MRS, followed by surgery with subsequent histopathological diagnosis. An experienced neuroradiologist (RJ) blinded to the final histopathology evaluated the imaging studies retrospectively. Provisional diagnoses based on preoperative clinical and conventional MR data versus preoperative MRS data were compared with definitive histopathological diagnoses.

RESULTS

Compared with preoperative clinical and conventional MR data, (1)H MRS improved the accuracy of MR imaging from 60.9% to 83%. We found (1)H MRS reliably distinguished between abscess and high-grade tumour, and between high-grade glioma and low-grade glioma, but was not able to reliably distinguish between recurrent glioma and radiation necrosis. In 12/23 cases (52%) the (1)H MRS findings positively altered our clinical management. Two representative cases are presented.

CONCLUSIONS

Our study supports a beneficial role for (1)H MRS in certain diagnostic intracranial dilemmas presenting to neurosurgeons. The information gleaned from preoperative (1)H MRS can be a useful adjunct to clinical and conventional MR imaging data in guiding the management of patients with intracranial pathologies, particularly high-grade tumour versus abscess, and high-grade versus low-grade glioma. Further larger prospective studies are needed to clearly define the utility of (1)H MRS in diagnostically challenging intracranial lesions in neurosurgery.

Metabolic response of glioma to dichloroacetate measured in vivo by hyperpolarized (13)C magnetic resonance spectroscopic imaging

BACKGROUND

The metabolic phenotype that derives disproportionate energy via glycolysis in solid tumors, including glioma, leads to elevated lactate labeling in metabolic imaging using hyperpolarized [1-(13)C]pyruvate. Although the pyruvate dehydrogenase (PDH)-mediated flux from pyruvate to acetyl coenzyme A can be indirectly measured through the detection of carbon-13 ((13)C)-labeled bicarbonate, it has proven difficult to visualize (13)C-bicarbonate at high enough levels from injected [1-(13)C]pyruvate for quantitative analysis in brain. The aim of this study is to improve the detection of (13)C-labeled metabolites, in particular bicarbonate, in glioma and normal brain in vivo and to measure the metabolic response to dichloroacetate, which upregulates PDH activity.

METHODS

An optimized protocol for chemical shift imaging and high concentration of hyperpolarized [1-(13)C]pyruvate were used to improve measurements of lactate and bicarbonate in C6 glioma-transplanted rat brains. Hyperpolarized [1-(13)C]pyruvate was injected before and 45 min after dichloroacetate infusion. Metabolite ratios of lactate to bicarbonate were calculated to provide improved metrics for characterizing tumor metabolism.

RESULTS

Glioma and normal brain were well differentiated by lactate-to-bicarbonate ratio (P = .002, n = 5) as well as bicarbonate (P = .0002) and lactate (P = .001), and a stronger response to dichloroacetate was observed in glioma than in normal brain.

CONCLUSION

Our results clearly demonstrate for the first time the feasibility of quantitatively detecting (13)C-bicarbonate in tumor-bearing rat brain in vivo, permitting the measurement of dichloroacetate-modulated changes in PDH flux. The simultaneous detection of lactate and bicarbonate provides a tool for a more comprehensive analysis of glioma metabolism and the assessment of metabolic agents as anti-brain cancer drugs.

Specific biomarkers of receptors, pathways of inhibition and targeted therapies: clinical applications

A deeper understanding of the role of specific genes, proteins, pathways and networks in health and disease, coupled with the development of technologies to assay these molecules and pathways in patients, promises to revolutionise the practice of clinical medicine. In particular, the discovery and development of novel drugs targeted to disease-specific alterations could benefit significantly from non-invasive imaging techniques assessing the dynamics of specific disease-related parameters. Here we review the application of imaging biomarkers in the management of patients with brain tumours, especially malignant glioma. This first part of the review focuses on imaging biomarkers of general biochemical and physiological processes related to tumour growth such as energy, protein, DNA and membrane metabolism, vascular function, hypoxia and cell death. These imaging biomarkers are an integral part of current clinical practice in the management of primary brain tumours. The second article of the review discusses the use of imaging biomarkers of specific disease-related molecular genetic alterations such as apoptosis, angiogenesis, cell membrane receptors and signalling pathways. Current applications of these biomarkers are mostly confined to experimental small animal research to develop and validate these novel imaging strategies with future extrapolation in the clinical setting as the primary objective.

Non-spin-echo 3D transverse hadamard encoded proton spectroscopic imaging in the human brain

A non-spin-echo multivoxel proton MR localization method based on three-dimensional transverse Hadamard spectroscopic imaging is introduced and demonstrated in a phantom and the human brain. Spatial encoding is achieved with three selective 90° radiofrequency pulses along perpendicular axes: The first two create a longitudinal ±M(Z) Hadamard order in the volume of interest. The third pulse spatially Hadamard-encodes the ±M(Z)s in the volume of interest in the third direction while bringing them to the transverse plane to be acquired immediately. The approaching-ideal point spread function of Hadamard encoding and very short acquisition delay yield signal-to-noise-ratios of 20 ± 8, 23 ± 9, and 31 ± 10 for choline, creatine, and N-acetylaspartate in the human brain at 1.5 T from 1 cm(3) voxels in 21 min. The advantages of transverse Hadamard spectroscopic imaging are that unlike gradient (Fourier) phase-encoding: (i) the volume of interest does not need to be smaller than the field of view to prevent aliasing; (ii) the number of partitions in each direction can be small, 8, 4, or even 2 at no cost in point spread function; (iii) the volume of interest does not have to be contiguous; and (iv) the voxel profile depends on the available B1 and pulse synthesis paradigm and can, therefore, at least theoretically, approach "ideal" "1" inside and "0" elsewhere.

Quantitative MR imaging and spectroscopy of brain tumours: a step forward?

OBJECTIVES

A prospective quantitative MR study of brain tumours was performed to show the potential of combining different MR techniques to distinguish various disease processes in routine clinical practice.

METHODS

Twenty-three patients with various intracranial tumours before treatment (diagnosis confirmed by a biopsy) and 59 healthy subjects were examined on a 3-T system by conventional MR imaging, 1H spectroscopic imaging, diffusion tensor imaging and T2 relaxometry. Metabolic concentrations and their ratios, T2 relaxation times and mean diffusivities were calculated and correlated on a pixel-by-pixel basis and compared to control data.

RESULTS

Different tumour types and different localisations revealed specific patterns of correlations between metabolic concentrations and mean diffusivity or T2 relaxation times. The patterns distinguish given tissue states in the examined area: healthy tissue, tissue infiltrated by tumour, active tumour, oedema infiltrated by tumour, oedema, etc. This method is able to describe the complexity of a highly heterogeneous tissue in the tumour and its vicinity, and determines crucial parameters for tissue differentiation.

CONCLUSIONS

A combination of different MR parameters on a pixel-by-pixel basis in individual patients enables better identification of the tumour type, direction of proliferation and assessment of the tumour extension.

KEY POINTS

• Magnetic resonance offers many different methods of examining the brain. • A combination of quantitative MR parameters helps distinguish different brain lesions • Different tumour types revealed specific correlation patterns amongst different MR parameters • The correlation patterns reflect highly heterogeneous complex tissue within tumours.

Complementary effect of H MRS in diagnosis of suprasellar tumors

OBJECTIVE

Suprasellar tumors are considered exceptionally important in neurosurgical practice due to their proximity to vital portions of the brain. Predicting histology of these tumors is of prime importance in determining the surgical approach, prognosis, and probable postoperative complications. There are numerous cases where computed tomography and magnetic resonance imaging (MRI) fail to predict histology. We have studied the role of magnetic resonance spectroscopy (MRS) in the diagnosis of suprasellar tumors.

METHODS

Twenty-three patients with primary nonfunctional suprasellar tumors and high-quality magnetic resonance spectra were studied. The most probable diagnosis (adenoma, meningioma, craniopharyngioma, or astrocytoma) was made by a neuroradiologist based on the MRI findings and then based on MRI plus MRS findings. Finally, the results were compared with the pathology report.

RESULTS

The information provided by MRS led the radiologist to alter his prior diagnosis that was based on the MRI in four patients, and the final diagnoses were in accordance with the histopathology. Wrong diagnosis was made by MRI plus MRS in three patients. Test efficiency of MRI was 69.6%, and it was 87% for MRI plus MRS. However, the difference was not statistically significant (P value=.152).

CONCLUSION

MRS may be useful in providing a more improved preoperative diagnosis of suprasellar tumors.

In vivo high-resolution localized (1) H MR spectroscopy in the awake rat brain at 7 T

In vivo localized high-resolution (1) H MR spectroscopy was performed in multiple brain regions without the use of anesthetic or paralytic agents in awake head-restrained rats that were previously trained in a simulated MRI environment using a 7T MR system. Spectra were obtained using a short echo time single-voxel point-resolved spectroscopy technique with voxel size ranging from 27 to 32.4 mm(3) in the regions of anterior cingulate cortex, somatosensory cortex, hippocampus, and thalamus. Quantifiable spectra, without the need for any additional postprocessing to correct for possible motion, were reliably detected including the metabolites of interest such as γ-aminobutyric acid, glutamine, glutamate, myo-inositol, N-acetylaspartate, taurine, glycerophosphorylcholine/phosphorylcholine, creatine/phosphocreatine, and N-acetylaspartate/N-acetylaspartylglutamate. The spectral quality was comparable to spectra from anesthetized animals with sufficient spectral dispersion to separate metabolites such as glutamine and glutamate. Results from this study suggest that reliable information on major metabolites can be obtained without the confounding effects of anesthesia or paralytic agents in rodents.

In vivo characterization of several rodent glioma models by 1H MRS

The assessment of metabolites by (1)H MRS can provide information regarding glioma growth, and may be able to distinguish between different glioma models. Rat C6, 9 L/LacZ, F98 and RG2, and mouse GL261, cells were intracerebrally implanted into the respective rodents, and human U87 MG cells were implanted into athymic rats. Ethyl-nitrosourea induction was also used. Glioma metabolites [e.g. total choline (tCho), total creatine (tCr), N-acetylaspartate (NAA), lactate (Lac), glutamine (Gln), glutamate (Glu), aspartate (Asp), guanosine (Gua), mobile lipids and macromolecules (MMs)] were assessed from (1)H MRS using point-resolved spectroscopy (PRESS) [TE = 24 ms; TR = 2500 ms; variable pulse power and optimized relaxation delay (VAPOR) water suppression; 27-μL and 8-μL voxels in rats and mice, respectively] at 7 T. Alterations in metabolites (Totally Automatic Robust Quantitation in NMR, TARQUIN) in tumors were characterized by increases in lipids (Lip1.3: 8.8-54.5 mM for C6 and GL261) and decreases in NAA (1.3-2.0 mM for RG2, GL261 and C6) and tCr (0.8-4.0 mM for F98, RG2, GL261 and C6) in some models. F98, RG2, GL261 and C6 models all showed significantly decreased (p < 0.05) tCr, and RG2, GL261 and C6 models all exhibited significantly decreased (p < 0.05) NAA. The RG2 model showed significantly decreased (p < 0.05) Gln and Glu, the C6 model significantly decreased (p < 0.05) Asp, and the F98 and U87 models significantly decreased (p < 0.05) Gua, compared with controls. The GL261 model showed the greatest alterations in metabolites. (1)H MRS was able to differentiate the metabolic profiles in many of the seven rodent glioma models assessed. These models are considered to resemble certain characteristics of human glioblastomas, and this study may be helpful in selecting appropriate models.

Advances in pituitary imaging technology and future prospects

There have been substantial advances in pituitary imaging in the last half-century. In particular, magnetic resonance imaging is now established as the imaging modality of choice, providing high quality images of the hypothalamic-pituitary axis and adjacent structures. More recent technological advances, such as the emergence of 3 Tesla MRI, are already being widely incorporated into imaging practice. However, other advanced techniques, including a variety of potential imaging biomarkers, still require further research to evaluate their potential and define their precise role. The recent development of intraoperative MRI appears promising and may have the potential to improve the outcome of pituitary surgery. Modern high quality imaging inevitably leads to the discovery of incidental lesions, including those within the pituitary gland, although it also plays a central role in their subsequent evaluation and management.

Spatial characteristics of newly diagnosed grade 3 glioma assessed by magnetic resonance metabolic and diffusion tensor imaging

The spatial heterogeneity in magnetic resonance (MR) metabolic and diffusion parameters and their relationship were studied for patients with treatment-naive grade 3 gliomas. MR data were evaluated from 51 patients with newly diagnosed grade 3 gliomas. Anatomic, diffusion, and metabolic imaging data were considered. Variations in metabolite levels, apparent diffusion coefficient (ADC), and fractional anisotropy (FA) were evaluated in regions of gadolinium enhancement and T2 hyperintensity as well as regions with abnormal metabolic signatures. Contrast enhancement was present in only 21 of the 51 patients. When present, the enhancing component of the lesion had higher choline-to-N-acetylaspartate index (CNI), higher choline, lower N-acetylaspartate, similar creatine, similar ADC and FA, and higher lactate/lipid than the nonenhancing lesion. Regions with CNI ≥ 4 had higher choline, lower N-acetylaspartate, higher lactate/lipid, higher ADC, and lower FA than normal-appearing white matter and regions with intermediate CNI values. For lesions that exhibited gadolinium enhancement, the metabolite levels and diffusion parameters in the region of enhancement were consistent with it corresponding to the most abnormal portion of the tumor. For nonenhancing lesions, areas with CNI ≥ 4 were the most abnormal in metabolic and diffusion parameters. This suggests that the region with the highest CNI might provide a good target for biopsies for nonenhancing lesions to obtain a representative histologic diagnosis of its degree of malignancy. Metabolic and diffusion parameter levels may be of interest not only for directing tissue sampling but also for defining the targets for focal therapy and assessing response to therapy.

Distinct peak at 3.8 ppm observed by 3T MR spectroscopy in meningiomas, while nearly absent in high-grade gliomas and cerebral metastases

The purpose of the present study was to evaluate distinct metabolic features of meningiomas to distinguish them from other brain lesions using proton magnetic resonance spectroscopy. The study was performed on 17 meningiomas, 24 high-grade gliomas and 9 metastases. Elevated signal intensity at 3.8 ppm observed in low TE spectra adequately differentiated meningioma from other brain tumors while alanine was not indicative of meningioma occurrence; the presence of lipids and lactate did not provide a strong index for meningioma malignancy.

Neurotoxicity of the CNS: diagnosis, treatment and prevention

Treatment-induced CNS toxicity remains a major cause of morbidity in patients with cancer. Real advances in the design of safer radiation procedures have been counterbalanced by a wider use of combined radiotherapy (RT)-chemotherapy regimens, the development of radiosurgery, and the increasing number of long-term survivors. While classic radionecrosis or chemonecrosis have become less common, more subtle changes such as progressive cognitive dysfunction are increasingly reported after RT (radiation-induced leukoencephalopathy) or chemotherapy (administered alone or in combination). The most important and controversial complications of RT, chemotherapy and combined treatments in the CNS are reviewed here, including new diagnostic tools, practical management and prevention that will influence the future management of cancer patients.

New pathology classification, imagery techniques and prospective trials for meningiomas: the future looks bright

PURPOSE OF REVIEW

Advances in functional and metabolic imaging have been added to the diagnostic armamentarium for meningioma. New prospective trials have been initiated, and it is foreseen that American Society of Clinical Oncology evidence-level II will be soon available for this brain tumor. This review will focus on recent advances in radiology and their significance for clinical care. The new WHO classification will be detailed.

RECENT FINDINGS

Brain invasion is an important criterion in the 2007 WHO classification for atypical meningioma. Apparent diffusion coefficient values on MRI observed with grade II and grade III meningiomas are significantly decreased when compared to benign tumors. [F]fluorodeoxyglucose PET may also predict tumor grade and tumor recurrence. Radio-labeled amino acid PET may be used to delineate target volume for radiotherapy planning. Stereotactic biopsy guidance and functional therapy monitoring could be foreseen using PET-MRI. One phase II study is assessing the benefit of dose escalation for nonbenign meningioma and another evaluates the therapeutic strategy of observation, standard- and high-dose radiotherapy for low-risk, intermediate-risk and high-risk patients.

SUMMARY

The use of functional MRI, with or without PET imaging, may be useful in assessing the potential clinical outcome of meningioma. Various therapeutic strategies, including observation and high-dose radiotherapy, are evaluated in two ongoing phase II studies.

Proton MR spectroscopy in a 1T open MR imaging system

(1)H-MR spectroscopy is an established noninvasive MR imaging technique that can be helpful in the diagnosis of brain lesions and in treatment planning. Claustrophobia and body habitus preclude some patients from routine MR imaging in a closed-bore system. The development of (1)H-MR spectroscopy for use in an open MR imaging system would enable a more complete characterization of brain lesions in these patients.

MR-visible lipids and the tumor microenvironment

MR-visible lipids or mobile lipids are defined as lipids that are observable using proton MRS in cells and tissues. These MR-visible lipids are composed of triglycerides and cholesterol esters that accumulate in neutral lipid droplets, where their MR visibility is conferred as a result of the increased molecular motion available in this unique physical environment. This review discusses the factors that lead to the biogenesis of MR-visible lipids in cancer cells and in other cell types, such as immune cells and fibroblasts. We focus on the accumulations of mobile lipids that are inducible in cultured cells by a number of stresses, including culture conditions, and in response to activating stimuli or apoptotic cell death induced by anticancer drugs. This is compared with animal tumor models, where increases in mobile lipids are observed in response to chemo- and radiotherapy, and to human tumors, where mobile lipids are observed predominantly in high-grade brain tumors and in regions of necrosis. Conducive conditions for mobile lipid formation in the tumor microenvironment are discussed, including low pH, oxygen availability and the presence of inflammatory cells. It is concluded that MR-visible lipids appear in cancer cells and human tumors as a stress response. Mobile lipids stored as neutral lipid droplets may play a role in the detoxification of the cell or act as an alternative energy source, especially in cancer cells, which often grow in ischemic/hypoxic environments. The role of MR-visible lipids in cancer diagnosis and the assessment of the treatment response in both animal models of cancer and human brain tumors is also discussed. Although technical limitations exist in the accurate detection of intratumoral mobile lipids, early increases in mobile lipids after therapeutic interventions may be useful as a potential biomarker for the assessment of treatment response in cancer.

Application of Novel Response/Progression Measures for Surgically Delivered Therapies for Gliomas

BACKGROUND

The Response Assessment in Neuro-Oncology (RANO) Working Group is an international, multidisciplinary effort to develop new standardized response criteria for clinical trials in brain tumors. The RANO group identified knowledge gaps relating to the definitions of tumor response and progression after the use of surgical or surgically based treatments.

OBJECTIVE

To outline a proposal for new response and progression criteria for the assessment of the effects of surgery and surgically delivered therapies for patients with gliomas.

METHODS

The Surgery Working Group of RANO identified surgically related end-point evaluation problems that were not addressed in the original Macdonald criteria, performed an extensive literature review, and used a consensus-building process to develop recommendations for how to address these issues in the setting of clinical trials.

RESULTS

Recommendations were formulated for surgically related issues, including imaging changes associated with surgical resection or surgically mediated adjuvant local therapies, the determination of progression in the setting where all enhancing tumor has been removed, and how new enhancement should be interpreted in the setting where local therapies that are known to produce nonspecific enhancement have been used. Additionally, the terminology used to describe the completeness of surgical resections has been recognized to be inconsistently applied to enhancing vs nonenhancing tumors, and a new set of descriptors is proposed.

CONCLUSION

The RANO process is intended to produce end-point criteria for clinical trials that take into account the effects of prior and ongoing therapies. The RANO criteria will continue to evolve as new therapies and technologies are introduced into clinical trial and/or practice.

Adult human neurogenesis: from microscopy to magnetic resonance imaging

Neural stem cells reside in well-defined areas of the adult human brain and are capable of generating new neurons throughout the life span. In rodents, it is well established that the new born neurons are involved in olfaction as well as in certain forms of memory and learning. In humans, the functional relevance of adult human neurogenesis is being investigated, in particular its implication in the etiopathology of a variety of brain disorders. Adult neurogenesis in the human brain was discovered by utilizing methodologies directly imported from the rodent research, such as immunohistological detection of proliferation and cell-type specific biomarkers in postmortem or biopsy tissue. However, in the vast majority of cases, these methods do not support longitudinal studies; thus, the capacity of the putative stem cells to form new neurons under different disease conditions cannot be tested. More recently, new technologies have been specifically developed for the detection and quantification of neural stem cells in the living human brain. These technologies rely on the use of magnetic resonance imaging, available in hospitals worldwide. Although they require further validation in rodents and primates, these new methods hold the potential to test the contribution of adult human neurogenesis to brain function in both health and disease. This review reports on the current knowledge on adult human neurogenesis. We first review the different methods available to assess human neurogenesis, both ex vivo and in vivo and then appraise the changes of adult neurogenesis in human diseases.

A systematic review of the literature on the effects of dexamethasone on the brain from in vivo human-based studies: implications for physiological brain imaging of patients with intracranial tumors

BACKGROUND

Among glucocorticoids, dexamethasone is most widely used for treatment of cerebral edema because of its long biological half-life and its low mineralocorticoid activity (sodium retaining).

OBJECTIVE

A systematic review of the literature on the effects of dexamethasone on the brain from in vivo studies in humans.

METHODS

A MEDLINE database search (via the PubMed interface) and an EMBASE database search (via the Dialog interface) of the past 35 years was performed. Every article relating to human use reported in English was included. In addition, references of all eligible articles were searched to identify other possible sources.

RESULTS

Twenty-four articles matched the eligibility criteria. There were disparate methodologies and conflicting results, although they tended to indicate a decrease in blood-tumor barrier permeability, decreased tumoral perfusion, decreased tumoral diffusivity, and the possibility of decreased perfusion in contralateral normal-appearing brain tissue.

CONCLUSION

Treatment with dexamethasone may alter imaging parameters from cerebral perfusion studies used in the management of brain tumors. In adequately powered studies, it may be possible to assess the longer term effects of dexamethasone on normal brain tissue to help optimize use with longer term survivors that are emerging as improvements in glioma treatment are made.

Primary and metastatic intraaxial brain tumors: prospective comparison of multivoxel 2D chemical-shift imaging (CSI) proton MR spectroscopy, perfusion MRI, and histopathological findings in a group of 159 patients

BACKGROUND

This study aims to assess the diagnostic value of multivoxel 2D chemical-shift imaging (CSI) proton magnetic resonance (MR) spectroscopy combined with perfusion magnetic resonance imaging (MRI) in the differential diagnosis and grading of brain tumors by comparing neuroimaging data with histopathological findings obtained after resection or biopsy.

METHODS

A total of 159 patients with a previous brain tumor diagnosis underwent multivoxel 2D CSI proton MR spectroscopy and perfusion MRI. MR spectroscopy multivoxel 2D CSI was performed with an echo time of 30, TR 1,500, FOV 160 mm, acquisition time 7 min 34 s. rCBV maps were evaluated during postprocessing. Statistical analysis was performed on the examination of distributive normality, with logarithmic transformations, Fisher's test, and Bonferroni's test. We used the Pearson's test to compare percentages.

RESULTS

In the differential diagnosis between GBM and metastases, MR spectroscopy multivoxel 2D CSI, combined with dynamic contrast enhanced MRI (DCE-MRI) perfusion, reached high sensibility and specificity (p < 0.000001). In brain tumor grading, the same method reached high sensibility and specificity (p < 0.000001) in distinguishing grade III-IV gliomas but encountered difficulty in determining grades within the two main groups of primary brain tumors, especially where mixed gliomas were involved.

CONCLUSIONS

The systematic use of CSI spectroscopy and perfusion imaging has shown a high potential in the differential diagnosis and grading of brain tumors. Further exploration into diagnostic procedures that can significantly distinguish between grade III-IV and grade II tumors is needed.

Detecting response of rat C6 glioma tumors to radiotherapy using hyperpolarized [1- 13C]pyruvate and 13C magnetic resonance spectroscopic imaging

We show here that hyperpolarized [1-(13) C]pyruvate can be used to detect treatment response in a glioma tumor model; a tumor type where detection of response with (18) fluoro-2-deoxyglucose, using positron emission tomography, is limited by the high background signals from normal brain tissue. (13) C chemical shift images acquired following intravenous injection of hyperpolarized [1-(13) C]pyruvate into rats with implanted C6 gliomas showed significant labeling of lactate within the tumors but comparatively low levels in surrounding brain.Labeled pyruvate was observed at high levels in blood vessels above the brain and from other major vessels elsewhere but was detected at only low levels in tumor and brain.The ratio of hyperpolarized (13) C label in tumor lactate compared to the maximum pyruvate signal in the blood vessels was decreased from 0.38 ± 0.16 to 0.23 ± 0.13, (a reduction of 34%) by 72 h following whole brain irradiation with 15 Gy.

Metabolomic patterns in glioblastoma and changes during radiotherapy: a clinical microdialysis study

We employed stereotactic microdialysis to sample extracellular fluid intracranially from glioblastoma patients, before and during the first five days of conventional radiotherapy treatment. Microdialysis catheters were implanted in the contrast enhancing tumor as well as in the brain adjacent to tumor (BAT). Reference samples were collected subcutaneously from the patients' abdomen. The samples were analyzed by gas chromatography-time-of-flight mass spectrometry (GC-TOF MS), and the acquired data was processed by hierarchical multivariate curve resolution (H-MCR) and analyzed with orthogonal partial least-squares (OPLS). To enable detection of treatment-induced alterations, the data was processed by individual treatment over time (ITOT) normalization. One-hundred fifty-one metabolites were reliably detected, of which 67 were identified. We found distinct metabolic differences between the intracranially collected samples from tumor and the BAT region. There was also a marked difference between the intracranially and the subcutaneously collected samples. Furthermore, we observed systematic metabolic changes induced by radiotherapy treatment among both tumor and BAT samples. The metabolite patterns affected by treatment were different between tumor and BAT, both containing highly discriminating information, ROC values of 0.896 and 0.821, respectively. Our findings contribute to increased molecular knowledge of basic glioblastoma pathophysiology and point to the possibility of detecting metabolic marker patterns associated to early treatment response.

T(2) determination of the J-coupled methyl protons of lipids: In vivo ilustration with tibial bone marrow at 3 T

PURPOSE

To demonstrate how J-coupling modulations of the CH(3) lipid resonance can be minimized enabling a representative T(2) to be measured.

MATERIALS AND METHODS

Experiments were conducted on canola oil and in vivo on tibial bone marrow of four volunteers at 3 T. The T(2) of the CH(2) protons was measured with a standard point resolved spectroscopy (PRESS) sequence, whereas the T(2) of the CH(3) protons was determined with a PRESS sequence composed of narrow bandwidth refocusing pulses designed to exploit the chemical shift displacement effect and rewind the J-coupling evolution of the CH(3) protons in the desired voxel. Spectra were acquired at five echo times.

RESULTS

The narrow bandwidth PRESS sequence rewound the J-evolution of the CH(3) protons resulting in a T(2) curve that was well described by a monoexponential function. The mean T(2) of the bone marrow CH(3) protons was calculated to be 132.6 msec. The mean T(2) of the bone marrow CH(2) protons was estimated with a regular PRESS sequence to be 88.0 msec. The mean CH(2):CH(3) tibial bone marrow composition was estimated to be 12.0:1.

CONCLUSION

The presented technique permits the T(2) of the methyl protons of lipids to be determined with more accuracy by minimizing contributions from J-coupling.

Intracranial meningiomas of atypical (WHO grade II) histology

Atypical (WHO grade II) meningiomas occupy an intermediate risk group between benign (WHO grade I) and anaplastic (WHO grade III) meningiomas. Although grade II meningiomas have traditionally been recognized in only about 5% of cases, after changes in diagnostic criteria with the current 2007 WHO standards, they now comprise approximately 20-35% of all meningiomas. Given the magnitude of this change, much work is now needed to solidify the adoption of these standards, to render inter-observer and inter-institutional comparisons more uniform, and to more carefully define the incidence of grade II histology. However, it is clear that they carry a several-fold increased risk of recurrence, as well as an increased rate of mortality. We will discuss the definition, diagnosis, and treatment of patients with atypical meningioma; review the current phase II cooperative trials; and draw attention to some questions timely for pre-clinical and clinical research.

Response assessment challenges in clinical trials of gliomas

Accurate, reproducible criteria for determining tumor response and progression after therapy are critical for optimal patient care and effective evaluation of novel therapeutic agents. Currently, the most widely used criteria for determining treatment response in gliomas is based on two-dimensional tumor measurements using neuroimaging studies (Macdonald criteria). In recent years, the limitation of these criteria, which only address the contrast-enhancing component of the tumor, have become increasingly apparent. This review discusses challenges that have emerged in assessing response in patients with gliomas and approaches being introduced to address them.

Updated response assessment criteria for high-grade gliomas: response assessment in neuro-oncology working group

Currently, the most widely used criteria for assessing response to therapy in high-grade gliomas are based on two-dimensional tumor measurements on computed tomography (CT) or magnetic resonance imaging (MRI), in conjunction with clinical assessment and corticosteroid dose (the Macdonald Criteria). It is increasingly apparent that there are significant limitations to these criteria, which only address the contrast-enhancing component of the tumor. For example, chemoradiotherapy for newly diagnosed glioblastomas results in transient increase in tumor enhancement (pseudoprogression) in 20% to 30% of patients, which is difficult to differentiate from true tumor progression. Antiangiogenic agents produce high radiographic response rates, as defined by a rapid decrease in contrast enhancement on CT/MRI that occurs within days of initiation of treatment and that is partly a result of reduced vascular permeability to contrast agents rather than a true antitumor effect. In addition, a subset of patients treated with antiangiogenic agents develop tumor recurrence characterized by an increase in the nonenhancing component depicted on T2-weighted/fluid-attenuated inversion recovery sequences. The recognition that contrast enhancement is nonspecific and may not always be a true surrogate of tumor response and the need to account for the nonenhancing component of the tumor mandate that new criteria be developed and validated to permit accurate assessment of the efficacy of novel therapies. The Response Assessment in Neuro-Oncology Working Group is an international effort to develop new standardized response criteria for clinical trials in brain tumors. In this proposal, we present the recommendations for updated response criteria for high-grade gliomas.

Sepsis-associated encephalopathy: a magnetic resonance imaging and spectroscopy study

Brain dysfunction is frequently observed in sepsis as a consequence of changes in cerebral structure and metabolism, resulting in worse outcome and reduced life-quality of surviving patients. However, the mechanisms of sepsis-associated encephalopathy development and a better characterization of this syndrome in vivo are lacking. Here, we used magnetic resonance imaging (MRI) techniques to assess brain morphology and metabolism in a murine sepsis model (cecal ligation and puncture, CLP). Sham-operated and CLP mice were subjected to a complete MRI session at baseline, 6 and 24 h after surgery. Accumulation of vasogenic edematic fluid at the base of the brain was observed in T(2)-weighted image at 6 and 24 h after CLP. Also, the water apparent diffusion coefficients in both hippocampus and cortex were decreased, suggesting a cytotoxic edema in brains of nonsurvival septic animals. Moreover, the N-acetylaspartate/choline ratio was reduced in brains of septic mice, indicating neuronal damage. In conclusion, noninvasive assessment by MRI allowed the identification of new aspects of brain damage in sepsis, including cytotoxic and vasogenic edema as well as neuronal damage. These findings highlight the potential applications of MRI techniques for the diagnostic and therapeutic studies in sepsis.

Potential of high field functional MRI in the neuroradiological diagnosis of brain tumours

Functional 3 tesla magnetic resonance imaging (MRI) techniques such as diffusion and perfusion imaging and MR spectroscopy (MRS) allow a more accurate diagnosis of central nervous system tumours. This retrospective study analysed the MRI scans of 121 consecutive patients with a diagnosis of glial brain tumours who underwent surgery and/or biopsy and whose histological reports were available. Our aim was to establish if and how functional MRI techniques had enhanced the diagnostic accuracy with respect to morphological examination. To quantify the diagnostic contribution of these techniques and their predictive value, a questionnaire was compiled by an observer blinded to the neuroradiological diagnosis and to the histological results after surgery/biopsy. Patients were divided into two groups based on the time of 3T MRI examination performed: before or after surgery/biopsy. In the group of non-operated patients low grade gliomas could be distinguished from high grade malignant tumours, whereas in the group of operated patients signs of tumour persistence or recurrence could be distinguished from the effects of previous treatments. Functional MRI techniques improved the accuracy of diagnosis with respect to morphological examination alone in both groups of patients: areas of increased cellularity, neoangiogenesis or metabolic changes were identified confirming diagnosis, whereas methodological errors were disclosed in cases of incorrect diagnosis.

N-acetyl resonances in in vivo and in vitro NMR spectroscopy of cystic ovarian tumors

An unassigned and prominent resonance in the region from delta 2.0-2.1 ppm has frequently been found in the in vivo MR spectra of cancer patients. We demonstrated the presence of this resonance with in vivo MRS in the cyst fluid of a patient with an ovarian tumor. (1)H-NMRS on the aspirated cyst fluid of this patient confirmed the observation. A complex of resonances was observed between 2.0 and 2.1 ppm. It was also present in 11 additional ovarian cyst fluid samples randomly chosen from our biobank. The resonance complex was significantly more prominent in samples from mucinous tumors than in samples from other histological subtypes. A macromolecule (>10 kDa) was found responsible for this complex of resonances. A correlation spectroscopy (COSY) experiment revealed cross peaks of two different types of bound sialic acid suggesting that N-glycans from glycoproteins and/or glycolipids cause this resonance complex. In the literature, plasma alpha-1 acid glycoprotein (AGP), known for its high content of N-linked glycans, has been suggested to contribute to the delta 2.0-2.1 spectral region. The AGP cyst fluid concentration did not correlate significantly with the peak height of the delta 2.0-2.1 resonance complex in our study. AGP may be partly responsible for the resonance complex but other N-acetylated glycoproteins and/or glycolipids also contribute. After deproteinization of the cyst fluid, N-acetyl-L-aspartic acid (NAA) was found to contribute significantly to the signal in this spectral region in three of the 12 samples. GC-MS independently confirmed the presence of NAA in high concentration in the three samples, which all derived from benign serous tumors. We conclude that both NAA and N-acetyl groups from glycoproteins and/or glycolipids may contribute to the delta 2.0-2.1 ppm resonance complex in ovarian cyst fluid. This spectral region seems to contain resonances from biomarkers that provide relevant clinical information on the type of ovarian tumor.

CNS complications of radiotherapy and chemotherapy

Treatment-induced CNS toxicity remains a major cause of morbidity in patients with cancer. Advances in the design of safe radiation procedures have been counterbalanced by widespread use of combined radiotherapy and chemotherapy, development of radiosurgery, and the increasing number of long-term survivors. Although classic radionecrosis and chemonecrosis have become less common, subtle changes such as progressive cognitive dysfunction are increasingly reported after radiotherapy (radiation-induced leukoencephalopathy) or chemotherapy (given alone or in combination). We review the most important and controversial complications of radiotherapy, chemotherapy, and combined treatments in the CNS, and discuss new diagnostic tools, practical management, prevention, and pathophysiological data that will affect future management of patients with cancer.

Imaging and spectroscopic findings in meningioangiomatosis

Meningioangiomatosis (MA) is an uncommon brain tumor. The role of imaging techniques is underscored in cases where the tumor location makes resection (or even biopsy) dangerous. We report the case of a child with an MA tumor located deep in the right sylvian fissure. A computed tomography (CT) scan showed calcifications in a highly vascular lesion with surrounding edema. Magnetic resonance spectroscopy (MRS) showed a distinct choline (Cho) peak, which usually suggests a proliferating tumor. Fluorodeoxyglucose positron emission tomography (FDG-PET) showed the lesion lacked hypermetabolic features. These radiological features should put MA in the differential diagnosis.

Towards oncological application of Raman spectroscopy

As the possibilities in the treatment of cancer continue to evolve, its early detection and correct diagnosis are becoming increasingly important. From the early detection of cancer to the guidance of oncosurgical procedures new sensitive in vivo diagnostic tools are much needed. Many studies report the Raman spectroscopic detection of malignant and premalignant tissues in different sites of the body with high sensitivities. The great appeal of this technique lies in its potential for in vivo clinical implementation. We present an overview of the in vitro and in vivo work on the oncological application of Raman spectroscopy and discuss its potential as a new tool in the clinico-oncological practice. Opportunities for integration of Raman spectroscopy in oncological cure and care as a real-time guidance tool during diagnostic (i.e. biopsy) and therapeutic (surgical resection) modalities as well as technical shortcomings are discussed from a clinician's point of view.

The use of magnetic resonance methods in translational cardiovascular research

Magnetic resonance methods are widely applicable to research questions posed in translational cardiovascular studies. The main intent of this review was to offer the cardiovascular translational research scientist a "menu" of magnetic resonance (MR) approaches that can be applied to answering research questions posed in a variety of experimental situations including those involving the use of human subjects. Obviously, this menu is not comprehensive and many other topics could have been selected for emphasis. However, we hope that the material presented encompasses a broad enough slice of the field to stimulate thinking about the possible applications of MR methods to specific research questions.

Monitoring response to chemotherapy of non-Hodgkin's lymphoma xenografts by T(2)-weighted and diffusion-weighted MRI

An effective method for in vivo detection of early therapeutic response of patients with non-Hodgkin's lymphoma would enable personalized clinical management of cancer therapy and facilitate the design of optimal treatment regimens. This study evaluates the feasibility of T(2)-weighted MRI (T2WI) and diffusion-weighted MRI (DWI) for in vivo detection of response of human diffuse large B-cell lymphoma xenografts in severe combined immunodeficient mice to chemotherapy. Each cycle of combination chemotherapy with cyclophosphamide, hydroxydoxorubicin, Oncovin, prednisone, and bryostatin 1 (CHOPB) was administered to tumor-carrying mice weekly for up to four cycles. T2WI and DWI were performed before the initiation of CHOPB and after each cycle of CHOPB. In order to corroborate the MRI results, histological analyses were carried out on control tumors and treated tumors after completion of all MRI studies. DWI revealed a significant (P < 0.03) increase in the mean apparent diffusion coefficient in CHOPB-treated tumors as early as 1 week after initiation of CHOPB. However, a significant (P < 0.03) decrease in mean T(2) was observed only after two cycles of CHOPB. Both MRI methods produced high-resolution (0.1 x 0.1 x 1.0 mm(3)) maps of regional therapeutic response in the treated tumors based on local apparent diffusion coefficient and T(2). Only a specific region of the tumors (in 3 of the 5 tumors) corresponding to about one third of the tumor volume exhibited a response-associate increase in ADC and decrease in T(2). An adjacent region exhibited an increase in T(2) and no change in ADC. The rest of the tumor was indistinguishable from sham-treated controls by MRI criteria. The therapeutic response of the treated tumors detected by MRI was accompanied by changes in tumor cell density, proliferation and apoptosis revealed by histological studies performed upon completion of the longitudinal study. The mechanism producing the regional response of the tumor remains to be elucidated.

Oral administration of choline does not affect metabolic characteristics of gliomas and normal-appearing white matter, as detected with single-voxel (1)H-MRS at 1.5 T

INTRODUCTION

The present study was done for evaluation of the possible influence of the oral administration of choline on metabolic characteristics of gliomas detected with proton magnetic resonance spectroscopy ((1)H-MRS).

MATERIALS AND METHODS

Thirty patients (22 men and eight women; mean age 38 +/- 15 years) with suspicious intracranial gliomas underwent single-voxel long-echo (TR 2,000 ms, TE 136 ms, 128-256 acquisitions) (1)H-MRS of the tumor, peritumoral brain tissue, and distant normal-appearing white matter before and several hours (median, 3 h; range, 1.2-3.7 h) after ingestion of choline with prescribed dose of 50 mg/kg (median actual dose, 52 mg/kg; range, 48-78 mg/kg). Investigations were done using 1.5 T clinical magnetic resonance imager. The volume of the rectangular (1)H-MRS voxel was either 3.4 or 8 cm(3). At the time of both spectroscopic examinations, similar voxels' positioning and size and technical parameters of (1)H-MRS were used. Surgery was done in 27 patients within 1 to 68 days thereafter. In all cases, more than 80% resection of the neoplasm was attained.

RESULTS

There were 12 low-grade gliomas and 15 high-grade gliomas. MIB-1 index varied from 0% to 51.7% (median, 13.8%). Statistical analysis did not disclose significant differences of any investigated metabolic parameter of the tumor, peritumoral brain tissue and distant normal-appearing white matter between two spectroscopic examinations.

CONCLUSION

Single-voxel (1)H-MRS at 1.5 T could not detect significant changes of the metabolic characteristics of gliomas, peritumoral brain tissue, and distant normal-appearing white matter after oral administration of choline.

Tumor cell metabolism imaging

Molecular imaging of tumor metabolism has gained considerable interest, since preclinical studies have indicated a close relationship between the activation of various oncogenes and alterations of cellular metabolism. Furthermore, several clinical trials have shown that metabolic imaging can significantly impact patient management by improving tumor staging, restaging, radiation treatment planning, and monitoring of tumor response to therapy. In this review, we summarize recent data on the molecular mechanisms underlying the increased metabolic activity of cancer cells and discuss imaging techniques for studies of tumor glucose, lipid, and amino acid metabolism.

Interleaved narrow-band PRESS sequence with adiabatic spatial-spectral refocusing pulses for 1H MRSI at 7T

Proton magnetic resonance spectroscopic imaging ((1)H MRSI) is a useful technique for measuring metabolite levels in vivo, with Choline (Cho), Creatine (Cre), and N-Acetyl-Aspartate (NAA) being the most prominent MRS-detectable brain biochemicals. (1)H MRSI at very high fields, such as 7T, offers the advantages of higher SNR and improved spectral resolution. However, major technical challenges associated with high-field systems, such as increased B(1) and B(0) inhomogeneity as well as chemical shift localization (CSL) error, degrade the performance of conventional (1)H MRSI sequences. To address these problems, we have developed a Position Resolved Spectroscopy (PRESS) sequence with adiabatic spatial-spectral (SPSP) refocusing pulses, to acquire multiple narrow spectral bands in an interleaved fashion. The adiabatic SPSP pulses provide magnetization profiles that are largely invariant over the 40% B(1) variation measured across the brain at 7T. Additionally, there is negligible CSL error since the transmit frequency is separately adjusted for each spectral band. in vivo (1)H MRSI data were obtained from the brain of a normal volunteer using a standard PRESS sequence and the interleaved narrow-band PRESS sequence with adiabatic refocusing pulses. In comparison with conventional PRESS, this new approach generated high-quality spectra from an appreciably larger region of interest and achieved higher overall SNR.

Differentiation of High-Grade and Low-Grade Gliomas Using Pattern Analysis of Long-Echo Single-Voxel Proton Magnetic Resonance Spectroscopy ((1)H-MRS)

The usefulness of proton magnetic resonance spectroscopy ((1)H-MRS) for glioma grading is not clear, particularly due to the absence of standard criteria for data analysis. Previously we had developed an original classification of the pathological (1)H-MRS spectra based on the identification of the predominant metabolite peak, N-acetylaspartate (NAA) for Type I, choline-containing compounds (Cho) for Type II, and mobile lipids (Lip) for Type III, and presence or absence of other metabolite peaks: lactate (Lac), Lip, or Cho. The present study evaluated the effectiveness of this classification in grading of previously non-treated gliomas. A total of 38 low-grade and 33 high-grade neoplasms were investigated. Four tumors had (1)H-MRS spectra Type I, and all of those were low-grade. Three tumors had (1)H-MRS spectra Type III, and all those were glioblastomas. Fifteen tumors with (1)H-MRS spectra Type II had a Lip/NAA ratio more than 1 (Type II C with moderate elevation of lipids), and 12 of those neoplasms were high-grade. The differences in distribution of high-grade and low-grade gliomas among another 49 gliomas with (1)H-MRS spectra Type II did not depend on the presence of Lac and/or Lip peaks, and in this subgroup NAA/Cho ratio was also evaluated. Inclusion of both characteristics (type of the (1)H-MRS spectrum and NAA/Cho ratio with defined cut-off level of 0.6) into the diagnostic algorithm yielded 72% diagnostic accuracy (95% confidence interval: 62%-82%) in discriminating high-grade and low-grade neoplasms. In conclusion, pattern analysis of the pathological (1)H-MRS spectra using the proposed classification along with evaluation of NAA/Cho ratio might be helpful for non-invasive glioma grading.

Performance evaluation of radiologists with artificial neural network for differential diagnosis of intra-axial cerebral tumors on MR images

BACKGROUND AND PURPOSE

Previous studies have suggested that use of an artificial neural network (ANN) system is beneficial for radiological diagnosis. Our purposes in this study were to construct an ANN for the differential diagnosis of intra-axial cerebral tumors on MR images and to evaluate the effect of ANN outputs on radiologists' diagnostic performance.

MATERIALS AND METHODS

We collected MR images of 126 patients with intra-axial cerebral tumors (58 high-grade gliomas, 37 low-grade gliomas, 19 metastatic tumors, and 12 malignant lymphomas). We constructed a single 3-layer feed-forward ANN with a Levenberg-Marquardt algorithm. The ANN was designed to differentiate among 4 categories of tumors (high-grade gliomas, low-grade gliomas, metastases, and malignant lymphomas) with use of 2 clinical parameters and 13 radiologic findings in MR images. Subjective ratings for the 13 radiologic findings were provided independently by 2 attending radiologists. All 126 cases were used for training and testing of the ANN based on a leave-one-out-by-case method. In the observer test, MR images were viewed by 9 radiologists, first without and then with ANN outputs. Each radiologist's performance was evaluated through a receiver operating characteristic (ROC) analysis on a continuous rating scale.

RESULTS

The averaged area under the ROC curve for ANN alone was 0.949. The diagnostic performance of the 9 radiologists increased from 0.899 to 0.946 (P < .001) when they used ANN outputs.

CONCLUSIONS

The ANN can provide useful output as a second opinion to improve radiologists' diagnostic performance in the differential diagnosis of intra-axial cerebral tumors seen on MR imaging.

Basal ganglia germinoma: diagnostic value of MR spectroscopy and (11)C-methionine positron emission tomography

We herein report a 12-year-old girl with a basal ganglia germinoma who presented with right-sided hemiparesis after a minor head trauma. Magnetic resonance (MR) imaging revealed a minimally enhanced lesion involving the left putamen, thalamus, and corona radiata. The lesion showed low-signal intensity on T1-, and high intensity on T2- and diffusion-weighted imaging. The MR signal in the adjacent globus pallidum was also low on T2-weighted imaging. MR spectroscopy on the lesion showed a large lactate/lipid/macromolecule peak with a decreased NAA/Cr ratio, but no increase in the Cho/Cr ratio. However, posttraumatic infarction at the territory of lateral lenticulostriate artery was ruled out 1 month later. This was based on progression of the hemiparesis and neuroimaging results, including an increased Cho/Cr ratio and weak uptake on (11)C-methionine positron emission tomography of the basal ganglia lesion. Stereotaxic brain biopsy confirmed the diagnosis of germinoma.

Progress in magnetic resonance imaging of brain tumours

PURPOSE OF REVIEW

Advances in magnetic resonance based techniques have yielded improvements in both high-resolution anatomical imaging and methods to evaluate physiology and function. This review focuses on recent developments in these techniques as applied to pretreatment staging and post-treatment evaluation of brain tumours.

RECENT FINDINGS

High-resolution spectroscopic imaging may contribute to pre-therapeutic grading and characterization of gliomas, as can diffusion techniques. The latter also hold promise in predicting survival in malignant supratentorial astrocytoma and could help to define areas for biopsy. Both methods can differentiate recurrent tumour from radiation injury. Perfusion-weighted magnetic resonance techniques offer potential markers of tumour angiogenesis and capillary permeability, and correlate well with vascular endothelial growth factor expression in grade II and grade III tumours. Functional magnetic resonance imaging can assess whether surgical treatment is feasible and select patients for intraoperative cortical stimulation. Combining multiple parameters in a magnetic resonance based diagnostic strategy could improve overall performance.

SUMMARY

Magnetic resonance imaging provides insights into the physiology of human tumours in a way that is both noninvasive and radiation free. We may expect from these new imaging methods greater specificity in diagnosis and useful tools with which to predict and assess response to therapy.

In vivo monitoring response to chemotherapy of human diffuse large B-cell lymphoma xenografts in SCID mice by 1H and 31P MRS

RATIONALE AND OBJECTIVES

A reliable noninvasive method for in vivo detection of early therapeutic response of non-Hodgkin's lymphoma (NHL) patients would be of great clinical value. This study evaluates the feasibility of (1)H and (31)P magnetic resonance spectroscopy (MRS) for in vivo detection of response to combination chemotherapy of human diffuse large B-cell lymphoma (DLCL2) xenografts in severe combined immunodeficient (SCID) mice.

MATERIALS AND METHODS

Combination chemotherapy with cyclophosphamide, hydroxy doxorubicin, Oncovin, prednisone, and bryostatin 1 (CHOPB) was administered to tumor-bearing SCID mice weekly for up to four cycles. Spectroscopic studies were performed before the initiation of treatment and after each cycle of the CHOPB. Proton MRS for detection of lactate and total choline was performed using a selective multiple-quantum-coherence-transfer (Sel-MQC) and a spin-echo-enhanced Sel-MQC (SEE-Sel-MQC) pulse sequence, respectively. Phosphorus-31 MRS using a nonlocalized, single-pulse sequence without proton decoupling was also performed on these animals.

RESULTS

Significant decreases in lactate and total choline were detected in the DLCL2 tumors after one cycle of CHOPB chemotherapy. The ratio of phosphomonoesters to beta-nucleoside triphosphate (PME/betaNTP, measured by (31)P MRS) significantly decreased in the CHOPB-treated tumors after two cycles of CHOPB. The control tumors did not exhibit any significant changes in either of these metabolites.

CONCLUSIONS

This study demonstrates that (1)H and (31)P MRS can detect in vivo therapeutic response of NHL tumors and that lactate and choline offer a number of advantages over PMEs as markers of early therapeutic response.

Heroin-induced leukoencephalopathy: characterization using MRI, diffusion-weighted imaging, and MR spectroscopy

AIM

To describe the magnetic resonance imaging (MRI) characteristics of heroin-induced leukoencephalopathy or "chasing the dragon syndrome" and, in particular, the diffusion-weighted imaging (DWI) and MR spectroscopy (MRS) features.

MATERIAL AND METHODS

Six patients with a clinical or histopathological diagnosis of heroin-induced leukoencephalopathy were identified and MRI examinations, including DWI and single-voxel MRS, reviewed.

RESULTS

Cerebellar white matter was involved in all six cases demonstrating similar symmetrical distribution with sparing of the dentate nuclei. Brain stem signal change was evident in five of the six patients imaged. Supratentorial brain parenchymal involvement, as well as brain stem involvement, correlated anatomically with corticospinal tract distribution. None of the areas of signal abnormality were restricted on DWI. Of those patients subjected to MRS, the areas of parenchymal damage demonstrated reduced N-acetylaspartate, reduced choline, and elevated lactate.

CONCLUSION

Heroin-induced leukoencephalopathy results in characteristic and highly specific signal abnormalities on MRI, which can greatly aid diagnosis. DWI and MRS findings can be explained by known reported neuropathological descriptions in this condition and can be used to support a proposed mechanism for the benefit of current recommended drug treatment regimes.