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M-A Weber

Publications and source records attributed to M-A Weber.

18 recordsLinked to original sources
PubMed2007

[MR perfusion and spectroscopic imaging in WHO grade II astrocytomas].

BACKGROUND: This study evaluates whether MR perfusion imaging and spectroscopic imaging (MRSI) can depict anaplastic areas in WHO grade II astrocytomas, whether these areas are co-localized, and whether the prognosis can be better predicted. MATERIAL AND METHODS: Fifteen patients (nine female, six male, aged 42+/-14 years) with WHO grade II astrocytomas but without preceding radio- or chemotherapy were examined every 3 months with MR perfusion imaging and MRSI (mean follow-up 18 months). Using a region of interest analysis, the regional relative cerebral blood volume (rrCBV) and blood flow (rrCBF) were measured in tumor tissue. In the same areas, choline/creatine (Cho/Cr) and choline/N-acetyl-aspartate (Cho/NAA) ratios were quantified. RESULTS: During follow-up, nine patients had stable disease. In six patients, the tumor showed progression and contrast-enhancement. The progressing tumors had already had higher perfusion (rrCBF 2.1+/-1.4; rrCBV 1.9+/-1.1) parameters than the stable astrocytomas (rrCBF 1.2+/-0.6, p=0.01; rrCBV 1.4+/-0.8, p=0.05) at first examination. However, the Cho/NAA and Cho/Cr ratios only tended to be higher than in stable astrocytomas (Cho/NAA 2.4+/-1.0 vs. 2.0+/-1.5, p=0.23; Cho/Cr 1.7+/-0.6 vs. 1.4+/-0.5, p=0.06). In all six progressing tumors, areas of maximum perfusion and maximum Cho/NAA and Cho/Cr ratio were co-localized. During follow-up, contrast-enhancement was observed in these areas. CONCLUSIONS: MR perfusion imaging can depict anaplastic areas in WHO grade II astrocytomas earlier than conventional MRI and thus enables a better prediction of prognosis.

Adult↗
PubMed2006

Muscle Na+ channelopathies: MRI detects intracellular 23Na accumulation during episodic weakness.

BACKGROUND: Muscle channelopathies such as paramyotonia, hyperkalemic periodic paralysis, and potassium-aggravated myotonia are caused by gain-of-function Na+ channel mutations. METHODS: Methods: Implementation of a three-dimensional radial 23Na magnetic resonance (MR) sequence with ultra-short echo times allowed the authors to quantify changes in the total muscular 23Na signal intensity. By this technique and T2-weighted 1H MRI, the authors studied whether the affected muscles take up Na+ and water during episodes of myotonic stiffness or of cold- or exercise-induced weakness. RESULTS: A 22% increase in the 23Na signal intensity and edema-like changes on T2-weighted 1H MR images were associated with cold-induced weakness in all 10 paramyotonia patients; signal increase and weakness disappeared within 1 day. A 10% increase in 23Na, but no increase in the T2-weighted 1H signal, occurred during cold- or exercise-induced weakness in seven hyperkalemic periodic paralysis patients, and no MR changes were observed in controls or exercise-induced stiffness in six potassium-aggravated myotonia patients. Measurements on native muscle fibers revealed provocation-induced, intracellular Na+ accumulation and membrane depolarization by -41 mV for paramyotonia, by -30 mV for hyperkalemic periodic paralysis, and by -20 mV for potassium-aggravated myotonia. The combined in vivo and in vitro approach showed a close correlation between the increase in 23Na MR signal intensity and the membrane depolarization (r = 0.92). CONCLUSIONS: The increase in the total 23Na signal intensity reflects intracellular changes, the cold-induced Na+ shifts are greatest and osmotically relevant in paramyotonia patients, and even osmotically irrelevant Na+ shifts can be detected by the implemented 23Na MR technique.

Adult↗
PubMed2006

Applications of MRS in the evaluation of focal malignant brain lesions.

Magnetic resonance spectroscopy (MRS) has clinically been most extensively used for assessing brain disorders, particularly tumors. With 1-H spectroscopy at intermediate echo times, resonances from choline, creatine, N-acetyl-aspartate (NAA), lactate, and free fatty acids can be resolved well enough to assist in diagnosis under routine conditions. Generally, an increased concentration of choline is found in all primary and secondary brain tumors, and the degree of increase correlates with the degree of anaplasia. Further indicators of anaplasia are the presence of lactate, indicating hypoxia, and of fatty acids, indicating necrosis. According to literature, the sensitivity of a combination of proton spectroscopy with contrast-enhanced dynamic susceptibility-weighted imaging for high-grade components in gliomas is better than conventional contrast-enhanced imaging alone. Today, proton spectroscopy is clearly indicated for differentiating radiation-induced damage from recurrences of irradiated brain tumors.

Brain Neoplasms↗
PubMed2006

[Application of (1)H MR spectroscopic imaging in radiation oncology: choline as a marker for determining the relative probability of tumor progression after radiation of glial brain tumors].

PURPOSE: To determine the relative signal intensity ratios of choline (Cho), phosphocreatine (CR) and N-acetyl-aspartate (NAA) in MR spectroscopic imaging (proton-MRSI) for differentiating progressive tumors (PT) from non-progressive tumors (nPT) in follow-up and treatment planning of gliomas. Threshold values to indicate the probability of a progressive tumor were also calculated. MATERIAL AND METHODS: Thirty-four patients with histologically proven gliomas showing a suspicious brain lesion in MRI after stereotactic radiotherapy were evaluated on a 1.5 Tesla unit (Magnetom Vision, Siemens, Erlangen, Germany) using 2D proton MRSI (repetition time/echo time = 1500/135 msec, PRESS; voxel size 9 x 9 x 15 mm (3)). A total of 274 spectra were analyzed (92 voxel were localized within the suspicious brain lesion). Relative signal intensities Cho, Cr and NAA were measured and their ability to discern between PT and nPT was assessed using the linear discrimination method, logistic regression, and the cross-validation method. PT and nPT were differentiated between on the basis of clinical course and follow-up by MRI, CT and positron emission tomography. RESULTS: The Cho parameter and the relative signal intensity ratios of Cr and NAA were most effective in differentiating between PT and nPT. The logistic regression method using the parameter ln(Cho/Cr) and ln(Cho/NAA) had the best predictive results in cross-validation. A sensitivity of 93.8 % and specificity of 85.7 % were achieved in the differentiation of PT from nPT by proton-MRSI. CONCLUSION: (1)H-MRSI has a high sensitivity and specificity for differentiating between therapy-related effects and the relapse of irradiated gliomas. This method allows for assessment of the probability of radiotherapy response or failure.

Adult↗
PubMed2006

[Atypical monoclonal plasma cell hyperplasia. Infiltration of ZNS].

Atypical monoclonal plasma cell hyperplasia is extremely rare in the central nervous system without involvement of bone or other systemic disease. This neuropathological entity was first described by Weidenheim and colleagues in 1989. It is considered an inflammatory pseudotumor that can evolve into malignant myeloma. We report on an atypical monoclonal plasma cell hyperplasia with bilateral occipital and cerebellar involvement in a 38-year-old woman. The diagnosis was confirmed by brain biopsy immunohistochemical and molecular tests.

Adult↗
PubMed2005

[Imaging of sacral chordoma: comparison between MRI and CT].

AIM: Sacral chordoma is a primarily benign tumor with a high tendency to recur. A correct definition of tumor volume is a significant prognostic factor. We compared the value of CT and MRI in diagnosing a sacral chordoma. METHODS: 31 patients with a histologically proven sacral chordoma were included in this study. Following parameters were analyzed by two independent radiologists: septation, signs of blood and ossification in the tumor tissue, contrast enhancement, maximal tumor diameter, infiltration of the soft tissue, the dural salc and the cauda equina and multifocality. RESULTS: In CT all chordomas showed a hypodensity to the normal tissue and in MRI a hyperintensity on T2w images with a low level of contrast enhancement. On the basis of the more precise soft tissue contrast of MRI compared with CT, MRI was significantly more accurate in all tested parameters (p <0.05) besides in detecting tumor ossification. In CT tumor volume was frequently underestimated. CONCLUSION: MRI in sacral chordoma is an essential tool in the pretherapeutic diagnostic regimen and in a state of relapse.

Adult↗
PubMed2005

[Perfusion measurement using the T2* contrast media dynamics in neuro-oncology. Physical basics and clinical applications].

Perfusion imaging in the central nervous system (CNS) is mostly performed using the first-pass dynamic susceptibility-weighted contrast-enhanced (DSC) MRI. The first-pass of a contrast bolus in brain tissue is monitored by a series of T2*-weighted MR images. The susceptibility effect of the paramagnetic contrast agent leads to a signal loss that can be converted, using the principles of the indicator dilution theory, into an increase of the contrast agent concentration. From these data, parameter maps of cerebral blood volume (CBV) and flow (CBF) can be derived. Regional CBF and CBV values can be obtained by region-of-interest analysis. This review article describes physical basics of DSC MRI and summarizes the literature of DSC MRI in neurooncological issues.Studies, all with relatively limited patient numbers, report that DSC MRI is useful in the preoperative diagnosis of gliomas, CNS-lymphomas, and solitary metastases, as well as in the differentiation of these neoplastic lesions from infections and tumor-like manifestations of demyelinating disease. Additionally, DSC MRI is suitable for determining glioma grade and regions of active tumor growth which should be the target of stereotactic biopsy. After therapy, DSC MRI helps better assessing the tumor response to therapy, residual tumor after therapy, and possible treatment failure and therapy-related complications, such as radiation necrosis. The preliminary results show that DSC MRI is a diagnostic tool depicting regional variations in microvasculature of normal and diseased brains.

Algorithms↗
PubMed2004

[Postpolio syndrome. Neurologic and psychiatric aspects].

Postpolio syndrome is defined as a clinical syndrome of new pareses in individuals who had been affected by acute paralytic poliomyelitis years before. The objective of this study was to describe neurologic and psychiatric signs of the disease. We evaluated the clinical signs and treatment of 16 patients with postpolio syndrome. Possible symptoms of depression were evaluated by the Hamilton and Geriatric Depression Scales. Postpolio syndrome manifested at a median age of 57.5 years (range 25-73) in a median of 41 years (range 16-70 years) after acute poliomyelitis. Muscles already affected during acute poliomyelitis were affected in all patients with postpolio syndrome. Six of 16 patients (37.5%) developed paresis in muscles formerly not affected by acute poliomyelitis. In eight of 15 patients (53%), depressive episodes were recognized according to the ICD-10 criteria. Symptoms of depression should be recognized in patients with postpolio syndrome and incorporated in therapy based on physiotherapy.

Adult↗
PubMed2004

[Noninvasive measurement of relative cerebral blood flow with the blood bolus MRI arterial spin labeling: basic physics and clinical applications].

Knowledge of tumor blood flow is important for diagnosis and follow-up of brain tumors after therapy, especially to discriminate necrosis from tumor recurrence after radiation or chemotherapy. Meanwhile, perfusion and diffusion MRI, besides MR-angiography, are state of the art in stroke imaging. Until now, perfusion imaging was mostly performed using the first-pass dynamic susceptibility-weighted contrast-enhanced (DSC) MRI. The MRI-based arterial spin labeling technique (ASL) is a novel approach for measuring relative cerebral blood flow (rCBF) without using extrinsic contrast agents, by labeling spins of flowing arterial blood as intrinsic contrast agent. This article describes physical basics of ASL and shows clinical examples in neuroimaging such as in meningeoma, glioblastoma, oligodendroglioma, and cerebral ischemia, using the Q2TIPS ASL technique. Gray matter is clearly visible, while the observed white matter signal obtained by Q2TIPS is only slightly higher than background noise. Venous blood causes artefacts in the sagittal sinus and other large superficial veins in the subarachnoid space. Meningeoma and glioblastoma show elevated rCBF, whereas oligodendroglioma and cerebral ischemia have reduced rCBF values. Arterial-spin-labeling techniques are noninvasive tools for measuring rCBF within 5 min, using a standard MRI scanner.

Blood Flow Velocity↗
PubMed2004

Perfusion MRI in CNS disease: current concepts.

Today there are several indications for cerebral perfusion MRI. The major indications routinely used in increasing numbers of imaging centers include cerebrovascular disease, tumor imaging and recently psychiatric disorders. Perfusion MRI is based on the injection of a gadolinium chelate and the rapid acquisition of images as the bolus of contrast agent passes through the blood vessels in the brain. The contrast agent causes a signal change; this signal change over time can be analysed to measure cerebral hemodynamics. The quality of brain perfusion studies is very dependent on the contrast agent used: a robust and strong signal decrease with a compact bolus is needed. MultiHance (gadobenate dimeglumine, Gd-BOPTA) is the first of a new class of paramagnetic MR contrast agents with a weak affinity for serum proteins. Due to the interaction of Gd-BOPTA with serum albumin, MultiHance presents with significantly higher T1- and T2-relaxivities enabling a sharper bolus profile. This article reviews the indications of perfusion MRI and the performance of MultiHance in MR perfusion of different diseases. Previous studies using perfusion MRI for a variety of purposes required the use of double dose of contrast agent to achieve a sufficiently large signal drop to enable the acquisition of a clear input function and the calculation of perfusion rCBV and rCBF maps of adequate quality. Recent studies with Multi-Hance suggest that only a single dose of this agent is needed to cause a signal drop of about 30% which is sufficient to allow the calculation of high quality rCBV and rCBF maps.

Brain Diseases↗