Computer tomography and NMR tomography
Imaging has been developing into a central component of neurological diagnostic investigation. The RKU offers both, nuclear magnetic resonance tomography (NMR tomography) and computer tomography (CT) performed using tomographs of the latest generation (NMR: Siemens MAGNETOM Symphony 1.5 Tesla; CT: Siemens SOMATOM Plus 4).
NMR generates tomograms of the human body by provoking magnetic nuclear resonance in any direction. The method is based around radio waves which excite specific nuclear elements (protons): the response from these nuclei in the tissue impacts the signals received and transformed into images by the NMR unit. Smallest tissue changes and functional disorders of inner organs can be detected (neurology mainly applies NMR to investigating the brain or the spinal cord). As opposed to other methods, NMR and the technology it is based on causes patients neither x-ray stress nor, as far as can be said today, any other risk.
CT also generates tomograms of the human body by x-raying layers of the area of interest and using a computer to compose accurate tomograms of the scans. This is another method which allows the visualisation of smallest tissue changes in the body (e.g. in the brain). Despite the fact that NMR produces higher-resolution images, CT still takes its stand among clinical neurological diagnostic methods of investigatingt cerabral hemorrhage and bone tissue, for example.
Contact:
PD Dr. J. Kassubek
Director & Senior Physician and Head of the Imaging Team
Phone: 0731/177-1206
Email: jan.kassubek@rku.de
Emergency diagnostics
Acute neurological disorders (specifically strokes) can be immediately investigated by means of imaging techniques in order to take optimised therapeutic steps on the spot. The RKU has its NMR and CT units on stand-by all around the clock (24x7) - which not even today is a matter of course everywhere.
Stroke
Due to their large number of incidents, strokes are the most frequent reason for starting emergency investigations by means of NMR/CT. Nowadays, imaging is a key instrument of acute stroke diagnostics. It allows
- distinguishing between cerebrovascular insufficiencies (ischemia) and cerebral hemorrhage (possible with CT also)
- an early detection of the ischemia zone (by means of techniques such as NMR diffusion weighting, DW)
- finding indications for fibrinolytic therapy
- a visualisation of the brain tissue at risk in the vicinity of the tissue previously damaged by the stroke in order to more accurately assess the risks and benefits of fibrinolytic therapy (DW and perfusion weighting, PW)
- MR angiography (MRA) which supplements ultrasound as another element of diagnosis for visualising not only cerebral arterial blood vessel obstructions/occlusions but also cerebral venous blood vessels in order to find sinus thromboses
- the diagnosis of vessel deformities in the brain
Other emergency investigations
Apart from strokes, the above methods provide a central diagnostic means for other acute neurological disorders such as space requirements which have become symptomatic (tumours) or described inflammations of the central nervous system (e.g. encephalites, abscesses).
Imaging and its importance for the diagnosis of neurological disorders
Chronic inflammatory CNS disorders
NMR imaging, apart from cerebrospinal fluid diagnosis (>>link to 2.2.1.3 CSF laboratory), is the central component of diagnosis and therapy control of cases of multiple sclerosis (MS, enzephalomyelitis disseminata). Clinic employees contribute to various international studies on the NMR control of novel MS therapeutic methods.
Epilepsy
Investigations of epileptic attacks are nowadays very much focussed on identifying defined smallest changes of the brain tissue assumed to be the origin of an attack, thus aiming at establishing surgery as a causal option of epilepsy treatment (see section 2.2.4.3 Epileptology for details). NMR techniques are at the core of this approach:
- high-resolution layers with T2 and proton weighting are scanned parallel and vertical to the temporal lobe to find even the smallest temporal processes or a mesial sclerosis, or
- high-resolution 3D records of 1 mm layers and reconstruction to show focal dysplasias and other lesions.
Image data analysis is backed up by years of expert knowledge reports and computer-based, standardised analysis methods used in conjunction or as an alternative.
Special NMR methods
Functional NMR (fNMR)
fMRT is a NMR method allowing to identify and visualise the cerebral areas involved in completing a specific task. It combines neuronal activation and associated super-proportional increase of regional blood flow compared with oxygen consumption and the ensuing increase in oxygenated hemoglobin in the capillaries of the activated brain tissue that the signals of the so-called BOLD contrast are based upon. Tests are done based on different paradigms (e.g. motor, somato-sensor or cognitive) to localise eloquent areas and to determine their interconnections (connectivity).
Apart from being extensively used in science, the method also has an increasing set of clinical indications mostly concerned with "pre-surgical brain mapping", i.e. with the pre-surgical localisation of functionally relevant areas. These applications aim at improving the planning of neurosurgery (for example for surgical treatment of epilepsy) and the intra-operative 3D orientation in conjunction with special neuro-navigation systems.
Spectroscopy
MR (proton) spectroscopy allows the in vivo visualisation of chemical factors (metabolites) located in specified regions of the brain which change in the process of diseases. Clinics are increasingly applying this method for differential diagnostics.
Examples of scientific interests:
Standardised methods of assessment of regional changes of cerebral structures
fNMR examination of functional networks and how they are changed by diseases
Diffusion tensor imaging of neurodegenerative disorders
Imaging as a control tool of MS and stroke therapies