[Technique of proton and phosphorous MR spectroscopy]. / Technik der Protonen- und Phosphor-MR-Spektroskopie.

CLINICAL/METHODICAL ISSUE: Magnetic resonance spectroscopy (MRS) is an important non-invasive method that can reveal the concentration and spatial distribution of particular biochemically relevant tissue metabolites. STANDARD RADIOLOGICAL METHODS: Proton MRS is routinely applicable in the clinical setting providing good quality results even with a moderate magnetic field strength of 1.5 T. Relative values of metabolite concentrations are mostly used for the assessment of metabolic disorders. METHODICAL INNOVATIONS: Absolute quantification of metabolites can be achieved by means of internal or external reference scans. Phosphorous MRS extends the range of detectable molecules to energy and cell membrane metabolism. PERFORMANCE: The lower detection limit of metabolite concentrations is in the range of some mmol/kg. Depending on the magnetic field strength, MRS enables a spatial resolution of a few milliliters. ACHIEVEMENTS: The use of phosphorous MRS is considerably limited because higher field strengths of at least 3.0 T and additional expensive hardware for signal processing are required.

[Basic principles and technique of diffusion-weighted imaging and diffusion tensor imaging]. / Grundlagen und Technik der diffusionsgewichteten MR­Bildgebung und der Diffusions­Tensor­Bildgebung.

BACKGROUND: Due to their thermal energy, water molecules in tissue are in continuous random motion called diffusion. Water diffusion in pathologically modified tissue (e. g. ischemia, inflammation and neoplasia) is different from normal conditions. Diffusion-weighted magnetic resonance (MR) imaging (DWI) can measure the local strength and main direction of the diffusional motion in any picture element, thus providing diagnostic tissue information exceeding the morphological depiction. METHODS: Diffusion-weighted MR sequences are based on the echo planar imaging (EPI) technique which is very rapid but also susceptible to artefacts. Using especially strong magnetic field gradient pulses the MR signal is sensitized to microscopic motion of water molecules resulting in a unique image contrast in addition to T1 and T2. Local deviations of the diffusion strength from normal values indicate pathological processes. The DWI sequences can measure diffusion along any direction; however, in the clinical routine only directionally averaged DWI images (trace maps) are used. Diffusion tensor imaging (DTI) represents an advanced DWI method which specifically explores diffusional anisotropy in order to obtain additional information about tissue microstructure. CONCLUSION: Diffusion-weighted MRI is an established technique for the assessment of pathological processes. Although DWI is mainly applied in stroke diagnostics, it is increasingly being used to detect and characterize various lesions in the brain as well as in the whole body. With new sequence techniques imaging artefacts can be significantly reduced. In addition, DTI allows the reconstruction and 3-dimensional visualization of tissue fibre structure. This method has proven to be clinically important primarily for the depiction of nerve tracts in the brain and spinal cord when planning surgical interventions and radiation therapy.

Influence of DGKH variants on amygdala volume in patients with bipolar affective disorder and schizophrenia.

The diacylglycerol kinase eta (DGKH) gene, first identified in a genome-wide association study, is one of the few replicated risk genes of bipolar affective disorder (BD). Following initial positive studies, it not only was found to be associated with BD but also implicated in the etiology of other psychiatric disorders featuring affective symptoms, rendering DGKH a cross-disorder risk gene. However, the (patho-)physiological role of the encoded enzyme is still elusive. In the present study, we investigated primarily the influence of a risk haplotype on amygdala volume in patients suffering from schizophrenia or BD as well as healthy controls and four single nucleotide polymorphisms conveying risk. There was a significant association of the DGKH risk haplotype with increased amygdala volume in BD, but not in schizophrenia or healthy controls. These findings add to the notion of a role of DGKH in the pathogenesis of BD.

[Functional MRI of speech]. / Funktionelle MRT der Sprache.

Speech is a multifactorial term. In relationship with our central organ, speech is a communication medium which in a complex manner includes the production and perception of verbal information. Even within this limitation, imaging exploration of the neuronal basis of verbal communication offers an extensive investigative field which can only be presented in this article as highlights. The main focus is on the technical hurdles of investigations into speech production using functional magnetic resonance imaging (fMRI) and solution options will be presented. The difficulties contained in this aspect are that spoken words can only be poorly assessed in the noise level of the measurements and that the movements of the mouth necessary for speech motoric can lead to technical imaging artefacts. Investigation techniques and designs will be discussed which allow a representation of speech-relevant brain centers despite these problems.

[Neuroimaging of color and spatial perception]. / "Neuroimaging" der Farb- und Raumwahrnehmung.

Spatial orientation and perception of distance are anchored in the visual system in the same way as color perception. However, different centers with different levels of expression are involved in the various aspects of visual processing starting from the primary visual cortex in the occipital lobes. In this article the investigation methods and designs are described by which the various functions within the visual system can be assigned to the appropriate specialized center in the parietal and temporal lobes using functional magnetic resonance imaging (fMRI).

[Functional MRI of the hearing center]. / Funktionelle MRT des Hörzentrums.

Examination of the sense of hearing is a technically difficult undertaking especially with functional magnetic resonance imaging because the machine causes a high noise level during the measurement. This article describes the technical conditions which, nevertheless, allow the auditory capabilities to be tested. Furthermore, every switch point of the auditory pathway and the cortical areas involved, which are technically accessible in an investigation of the sense of hearing are pictorially described.

[Basic principles of MR spectroscopy]. / Grundlagen der MR-Spektroskopie.

MR spectroscopy (MRS) is a non-invasive method for investigating tissue metabolism. In the clinical setting proton spectroscopy based on the hydrogen nucleus ((1)H) is primarily used for determining concentrations of important brain metabolites. This paper illustrates the physicochemical principles of MRS and the requirements for high quality spectra. Moreover, different techniques for acquiring localized spectra are demonstrated.

[Multiple sclerosis]. / Multiple Sklerose.

Multiple sclerosis is the most common chronic inflammatory disease of myelin with interspersed lesions in the white matter of the central nervous system. Magnetic resonance imaging (MRI) plays a key role in the diagnosis and monitoring of white matter diseases. This article focuses on key findings in multiple sclerosis as detected by MRI.

Neurochemical pathology in hippocampus in euthymic patients with bipolar I disorder.

OBJECTIVE: Subcortical regions such as hippocampus, thalamus and ventral putamen are assumed to be involved in the pathophysiology of mood regulation. Disturbed hippocampal neuronal function indicated by reduced N-acetyl-aspartate (NAA) levels in bipolar patients was shown by several studies. Results in thalamus and putamen are inconsistent. METHOD: N-acetyl-aspartate, choline (Cho), creatine (Cr) and myo-inositol (Ins) were measured in left hippocampus, left thalamus and left putamen using proton magnetic resonance spectroscopy in 13 euthymic patients with bipolar I disorder and 13 pairwise matched healthy control subjects. Metabolic ratios NAA/Cr, NAA/Cho, Cho/Cr and Ins/Cr were calculated. RESULTS: Patients with bipolar I disorder demonstrated significantly reduced NAA/Cr in the left hippocampus compared with healthy control subjects. No alterations were found in thalamus or putamen. CONCLUSION: We hypothesize that this NAA/Cr reduction might reflect neuronal dysfunction in the left hippocampus in patients with bipolar disorder.

[Supratentorial tumors]. / Supratentorielle Tumoren.

Magnetic resonance imaging is a routine diagnostic measure for a suspected intracerebral mass. Computed tomography is usually also indicated. Further diagnostic procedures as well as the interpretation of the findings vary depending on the tumor location. This contribution discusses the symptoms and diagnostics for supratentorial tumors separated in relation to their intra- or extracranial location. Supratentorial tumors include astrocytoma, differentiated by their circumscribed and diffuse growth, ganglioglioma, ependyoma, neurocytoma, primitive neuroectodermal tumors (PNET), oligodendroglioma, dysem-bryoplastic neuroepithelial tumors (DNET), meningoangiomatosis, pineal tumors, hamatoma, lymphoma, craniopharyngeoma and metastases. The supratentorial extracranial tumors include the choroid plexus, colloid cysts, meningeoma, infantile myofibromatosis and lipoma. The most common sub-forms, especially of astrocytoma, will also be presented.

[Infratentorial tumors]. / Infratentorielle Tumoren.

This article gives an overview concerning the typical infratentorial tumors of adults.

[MR spectroscopy in brain tumors]. / MR-spektroskopie bei Hirntumoren.

MRT allows the anatomical visualization of intracerebral space-occupying lesions, and when magnetic resonance spectroscopy (MRS) is used in routine clinical practice it can give more information and be helpful in the diagnosis of such lesions. In MRS with long echo times for nerve tissue there are five metabolites that are particularly significant: N-acetyl aspartate (NAA), creatine, choline, lactate, and lipids. NAA levels are lowered in the presence of intracerebral tumors. Creatine is lowered in situations of hypermetabolic metabolism and elevated in hypometabolic conditions, but remains constant in many pathologic states and can be used as a reliable reference value. With malignant tumors there are usually elevated choline concentrations, reflecting increased membrane synthesis and a higher cell turnover. The lactate level rises following a switch in metabolism from aerobic to anaerobic glycolysis, and this is frequently observed in the presence of malignant tumors. The occurrence of lipid peaks in a tumor spectrum suggests the presence of tissue necroses or metastases. There are typical constellations that are seen on MRS for individual tumors, which are discussed in detail in the present paper.

[Imaging of spinal tumors]. / Bildgebung intraduraler Raumforderungen.

Spinal tumors are often categorized into extradural, intradural extramedullary, or intramedullary. Although this classification represents somewhat of an overgeneralization as a lesion may reside in two compartments, it still helps to characterize spinal tumors. In the intradural, extramedullary space, primary tumors, such as neurofibroma and meningioma, are relatively common. Secondary tumors or leptomeningeal enhancement also occur. In the intramedullary space, primary tumors are far more common than secondary tumors or metastases.

[Spinal infections]. / Entzündliche Wirbelsäulenerkrankungen.

Regardless of the compartment involved, imaging of spinal infections and other spinal inflammatory diseases must be performed by magnetic resonance imaging (MRI). This allows early detection of changes in disk space or vertebral bodies. Associated paraspinal and epidural masses are depicted. However, in spinal cord inflammation MRI has a very limited specificity and cannot usually differentiate between the wide array of possible causes of intramedullary lesions. This article covers a spectrum of inflammatory lesions of the spinal cord.

Cognitive changes after carotid artery stenting.

INTRODUCTION: We aimed to test changes in cognitive performance after carotid artery stenting (CAS). METHOD: Ten patients were neuropsychologically tested at least 24 h before and 48 h after CAS. To diminish thromboembolic events, we used a proximal protection device. The following neuropsychological tests were selected: The Mini Mental State Examination (MMSE), symbol digit test and subtests of the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) battery (verbal fluency, constructional practice, word list memory and delayed recall). Affective state was determined by the Beck Depression Score (BDS). RESULTS: No patient suffered from depression (BDS <1) or dementia (MMSE 29.9+/-1.5). Nine of the ten patients (P=0.12) showed increased speed in the Number Connection Test (NCT) (corresponding to trail making test). Most patients showed better or similar results concerning delayed recall (P=0.31). No change was observed in the symbol digit test, word list memory, verbal fluency or constructional practice. Better results concerning NCT and delayed recall after carotid stenting might be due to improved brain perfusion. CONCLUSION: After CAS, cognitive and memory performance seem to improve. Further studies with different time intervals and more refined testing, as well as perfusion-weighted imaging, are needed.

Time course of the apparent diffusion coefficient after cerebral infarction.

The purpose of this study was to evaluate quantitative apparent diffusion changes in the center of infarction by measurement of the apparent diffusion coefficient (ADC), and to investigate the influence of ischemia on the contralateral hemisphere. By diffusion echo-planar imaging (EPI) 52 patients showing cerebral infarction were studied within 5 h to >12 months after onset of clinical symptoms. Using three diffusion gradient strengths (b1=30 s/mm(2); b2=300 s/mm(2), b3=1100 s/mm(2)) ADC maps were generated. After onset of ischemia, ADC in the center of infarction was lower than in the contralateral regions of human brain. At first ADC declined for approximately 28 h to a minimum of approximately 150x10(-8) cm(2)/s. Then the ADC reincreased and reached a "pseudonormalization" after approximately 5 days. Chronic infarctions did show much higher ADC values (2000x10(-8) cm(2)/s) than unaffected areas. Neither localization nor size of infarctions showed a significant influence on this time course. In the center of infarction diffusion is isotropic. Even brain regions of the contralateral hemisphere are influenced by cerebral ischemia. In these regions ADC is higher than for physiological conditions. The ADC also declines especially for the first 2-3 days after onset of symptoms, also followed by reincrease. The ADC calculation enables determination of the onset of infarction more exactly than is possible using only diffusion-weighted imaging. Diffusion in the center of infarction is isotropic; hence, orientation of the diffusion gradients has no significant influence on sensitivity of measurements. The calculation of the ADC ratio based on data derived from the center of infarction and the contralateral hemisphere seems to be critical because the ADC in the unaffected contralateral hemisphere also changes.

[Image fusion of MRI and immunoscintigraphy with MAb-170 in ovarian tumors]. / Bildfusion von KST und Immunszintigraphie mit MAb-170 bei Ovarialtumoren.

In recent years multimodality imaging achieved growing importance. It is mostly performed by means of quite expensive software and hardware solutions. In the present pilot study a simple and low-cost procedure was developed to achieve image fusion in the pelvis. The image data of immunoscintigraphy (SPECT) and MRI were transferred to a personal computer and combined by standard software for image manipulation. The results in eleven patients with space-occupying lesions in the pelvis showed that adequate anatometabolic slices could be achieved. The results show a tendency to increased specificity and precision of multimodality imaging in comparison with SPECT and MRI alone. In conclusion, the low-cost solution, as developed by us, is feasible in clinical practice. Its results are reliable in clinical decision making.

[Proton spin tomography of the orbit in post-traumatic motility disorders]. / Kernspintomographie der Orbitae bei posttraumatischen Motilitätsstörungen.

AIM: To analyse the value of MRI for the assessment of posttraumatic disturbances of eye motility. MATERIAL AND METHODS: We analysed retrospectively the results of 38 MR examinations of the orbit in 31 patients with posttraumatic motility impairment with preserved visus. 18 patients underwent MRI preoperatively. From this group 5 patients were additionally examined postoperatively. Another 5 patients who had not been examined prior to surgery were controlled postoperatively. Hence, a total of 10 patients with persisting disturbances was examined postoperatively. 8 patients who underwent MRI were not treated by surgery because of only minor disturbances. In all patients conventional radiography of the orbit was performed prior to MRI. Additional CT imaging was carried out in 12 patients. RESULTS: In 18 patients examined preoperatively we found displacement of orbital fat tissue, displacement and entrapment of orbital muscles, swelling of muscles and oedema in retrobulbar fat tissue. 10 patients from the postoperative group exhibited remaining prolapsed fat tissue, oedema in fat tissue and/or swelling of muscles. 8 patients had only small soft tissue changes which did not require surgery. CONCLUSION: Since it can image soft tissue precisely, MRI provides the decisive information in the assessment of motility impairment of the eye. In case of isolated orbital fracture with motility impairment, CT is not absolutely necessary for surgical therapy.