Magnetic resonance imaging with high-field devices with a base magnetic field strength of 3 Tesla represents a current advancement in clinical imaging that has so far only been used in a few centres. only available in a few centres centres.

In co-operation with the Department of Psychiatry, the Department of Diagnostic and Interventional Radiology has a 3 Tesla magnetic resonance tomograph specifically for brain examinations.

Vascular imaging using magnetic resonance imaging is a non-invasive diagnostic method that can replace diagnostic catheter angiography in many cases. This method can be used with high quality for almost every vascular province of the human body.

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Visualisation of the arterial vessels at the base of the skull using MRI (time-of-flight sequence (tof))

fMRI has been used for about ten years and allows us to visualise areas of the brain that are active when performing certain tasks. This means that we can show you which part of the brain is doing something when you speak, learn something or simply move your hand, for example. In patients with brain tumours, we are thus able to provide the surgeon with important information for planning the operation - so that these areas can be spared during the operation if they are close to a tumour to be removed. In addition, this method can be used to investigate how the brain functions in healthy individuals.

For the fMRI examination, it is important that the brain is continuously imaged over a longer period of time - i.e. you watch it at work, so to speak. The entire brain is imaged approximately every three seconds. This usually takes several minutes. This means that with fMRI we have to work with very fast (and therefore unfortunately noisy) examination sequences, and we also have to make do with a lower resolution. This is also acceptable, as the areas of the brain we are looking for are quite large.

Strictly speaking, we only "see" the difference between what the brain cells are doing and not doing. The tasks are structured accordingly so that you alternate between doing something, e.g. moving your hand, and doing nothing, i.e. keeping your hand still. With language, it is sometimes not so easy to "switch it off", so we have to put a lot of thought into the design of the tasks.

In the graphic below, the change is indicated by the beautiful new German words "on" for doing and "off" for not doing. Below this you can see the stylised images that are recorded, blue for rest and red for activation. To the right is a white area calculated from these images showing where the brain is doing something. A black line in the white field shows how the grey value of the actual MR images behaves at this point. These signal fluctuations ultimately reveal the active brain area!

Do you want to know where these signal changes come from? This has to do with the fact that the blood flow in the brain is regulated depending on how much the corresponding grey cells have to do. The magnetic properties of blood are different to those of brain tissue and, as its name suggests, magnetic resonance imaging is, of course, exactly the right tool to uncover these differences.

The success of this procedure can be explained by its advantages over conventional techniques: non-invasive, no exposure to radiation or contrast agents, high temporal and spatial resolution and repeatability. The fMRI data not only shows neurosurgeons how far they can operate without impairing important functions, but also how they can best reach the tumour without destroying too much on the way. The data from neuronavigation is not only helpful in the planning phase, but also during the operation. For the patient, this examination method means more information about the surgical risk even before the operation.

Of course, the same restrictions apply as for conventional MRI, i.e. patients with metallic implants, pacemakers or foreign bodies that have entered the body as a result of accidents, such as shrapnel, may not be able to be examined. Due to the particularly fast sequences and the fact that we examine the head, fixed braces can sometimes be a problem. The same applies if a large number of fillings or dental implants have been inserted. Furthermore, fMRI is more dependent on the patient's co-operation than any other MR examination. The execution of the stimulation tasks can strongly influence the examination result. The technique is also susceptible to image artefacts. Involuntary movements during the examination, especially small head movements, are still the most common cause of non-analysable examinations.