Information for patients

This site contains information for patients who wish to learn more about the diagnostic and therapeutic possibilities of Neuroradiology. We have attempted to present the information in generally understandable, not too-technical medical language. The information is not intended to make personal discussion with the doctor unnecessary, but rather to present basic information as a foundation for each patient’s personal questions and needs.

What is Neuroradiology?

Neuroradiology is a subspecialty section within radiology. Neuroradiology is divided into diagnostic and interventional radiology. Diagnostic neuroimaging techniques are used for diagnosis of diseases of the central and peripheral nervous system, head and neck and spine. In interventional neuroradiology tools are used for imaging and minimally invasive treatment of mainly vascular abnormalities.

What modalities are used in Neuroradiology?

Diagnostic imaging tools include X-ray, Computed Tomography (CT), Magnetic Resonance Imaging (MRI) with particular techniques like Magnetic Resonance Angiography (MRA), diffusion and perfusion weighted imaging. The use of conventional imaging and ultrasound is limited and only used for certain indications. With Digital Subtraction Angiography (DSA) vascular abnormalities are visualised (e.g. aneurysm and vascular stenosis) and treated.

X-ray

Traditional X-ray pictures of the head and spine have lost their importance these days. They are mainly used now following accidents, in chronic diseases of the spine, tumours arising in the bones or following surgery. They have largely been replaced by computer tomography and magnetic resonance tomography.

1. Computed tomography (CT)

Computed tomography (CT) is an X-ray procedure: during the examination, an X-ray tube circles the supine patient while at the same time detectors opposite the tube and rotating with it measure the radiation. These radiation values are converted in computer calculations to layered images. The patient lies on a special table, which is placed in the CT unit to the level of the body part to be examined. Numerous cross-sections only a few millimeters thick of the area to be examined are imaged. Unlike traditional X-ray examinations, the organs can be imaged without the overlying structures and are thus better visible. Even slight differences in tissues become visible and can be made additionally clearer by injection of contrast agent.

The CT is a quick and reliable examination method which is eminently suitable for both emergency diagnostics and the diagnostics of several diseases of the nervous system (head, spine, spinal cord or nerves), for example in stroke, cerebral bleeding, accidents, malformations, tumours, vertebral disc prolapse. Additional application of contrast agent enables direct imaging of blood vessels and of blood flow in the brain: thus stroke can be accurately diagnosed, when brain tissue can be saved by prompt initiation of therapy. Narrowing of blood vessels ("stenoses") or vessel occlusion, which may be causes of stroke, can be detected. After cerebral bleeding, the pathological changes in vessels (vascular bulging = aneurysms) can also be detected quickly and with high spatial resolution.

The advantages of the CT are the widespread use of the equipment, making the examination readily available, the short examination time, the reliability of results in emergency examinations; moreover, the units are generously constructed so that even people who are fearful in closed spaces can be examined, and unlike the magnetic resonance tomography (MRT), patients with pacemakers and other metal foreign bodies can be examined.

The disadvantages of the CT are based on the exposure to radiation (although this is slight and further minimized by current technical developments), and the lower tissue contrast compared to MRT. In applying the contrast agent, allergic reactions or critical overfunction of the thyroid ("thyreotoxic crisis") may occur in very rare cases.

In summary, computed tomography is the first choice in a number of emergency and routine examinations, making MRT unnecessary in these patients.

2. Magnetic Resonance Image

Magnetic resonance tomography (MRT or MRI) is a medical imaging procedure to depict organs and tissues using magnetic fields and radio waves. Unlike computer tomography , the MRT can be used to produce not only horizontal views, but also other levels without changing the position of the patient.

Magnetic resonance tomography has a number of advantages over other imaging procedures, such as:

- No exposure to radiation.

- Very high soft-tissue contrast, even in the vicinity of bones. This makes it possible, for example, to image small pathological processes in the spinal cord, which cannot be recorded in computer tomography due to the adjacent spinal column. Images of any desired level and view without changing the patient's position.

However, the MRT is not generally "better" than CT. There are questions which can be better answered by CT, such as bone lesions, for example at the skull base, bone fractures (breaks), fresh blood. Moreover, monitoring and examining is simpler in unconscious patients. Also, patients with pacemakers can usually not be examined because of possible disruption caused by the magnetic field in the magnetic resonance tomography. Patients with claustrophobia can experience fear in the MRI scanner. Various procedures can minimize anxiety in these patients, for example lightning and using headphones and also medication can help.

Finally, an MRT examination is considerably more expensive than a CT examination.

Where is magnetic resonance image used in neuroradiology?

MRT is especially well-suited for examination of the brain and spinal cord. Flowing blood in the arteries and veins can be imaged, as can e.g. diseases of the spinal column and vertebral discs.

Thus, for example, in stroke, the brain tissue in which blood flow in interrupted, as well as the vessels leading to the brain and possible occlusions in these vessels can be imaged by MR angiography .

How is magnetic resonance image performed?

This depends essentially on the type of equipment and the purpose of the individual examination. Usually, the patient is placed on a gurney and pushed into a "tube" with a diameter of about 60 cm. During the examination, taps can be heard which are caused by the electromagnetic switches (gradient fields). In order to exclude excessive noise, the patient wears hearing protection (headset, ear-plugs, small pillows at the ears). The average examination lasts about 15-30 minutes. It is sometimes necessary to administer a contrast agent.

What must you do if you are to undergo magnetic resonance tomographic examination?

1. Do you have a pacemaker, insulin pump, artificial heart valve or other implants?

2. Do you know of any metal parts remaining in your body after surgery or accident? (for example after broken bones, clips, spirals, metal splinters in the eye, gunshots?)

3. Do you have any allergies or intolerance to medications?

4. Did any problems arise after other examinations with contrast agents?

5. Do you suffer from a disease of the kidney?

If any of these apply to you, a magnetic resonance tomography may not be possible, or only possible without contrast agent!

a. ADVANCED MRI

Functional MRT (fMRT)

The basis of the fMRT is the fact that the activity of nerve cells results in local changes in the blood flow in the brain. These can be made visible using special examination sequences, since blood containing oxygen has other magnetic properties than blood from which brain activity has depleted the oxygen. This makes it possible to visualize the activation area in the brain in a wide variety of motor, sensory and cognitive processes without using contrast agent. This procedure is performed, for example, prior to neurosurgical operations in which tumours are located near functionally-important areas of the brain (for example for movement or speech) which must be spared during the operation.

Diffusion and perfusion imaging:

In so-called diffusion-weighted examinations, the diffusion (molecular movement) of water in the tissues can be made visible. In stroke, there is an early disruption in this diffusion in brain tissue without blood flow. Thus, diffusion-weighted MRT is a very sensitive procedure to diagnose stroke. When the diagnosis is made early enough, destruction of brain tissue can be prevented or limited by means of appropriate therapy. The flow of blood in the brain can be imaged with perfusion imaging, which also provides additional information, for example in stroke.

MR angiography

Here, special examination sequences are used which are particularly sensitive to movements of small particles, such as flowing blood. This enables direct visualization of vessels through which blood is flowing, without the use of contrast agent. Correspondingly, narrowing or blockage of arteries and veins is also visible. Some of the examinations which used to be performed only invasively, using catheter angiography, can be replaced with this less-stressful MR angiography

MR spectroscopy

Brain metabolic products in the living body can be determined with this procedure. The procedure is useful for example for preoperative characterization of brain tumours, and also in the diagnostics of metabolic diseases of the brain.

3. Angiography (vascular imaging):

Angiography is a routine procedure with which vessels supplying the brain or spinal cord can be imaged. The classical angiography via catheter has been replaced in part in recent years by computed tomographic or magnetic resonance tomographic angiography techniques which are non-invasive. The catheter angiography is used these days in a computer-supported form, the so-called digital subtraction angiography, in which only arteries and veins are imaged and bone is not visible and does not cover the vessel. Modern angiography equipment can make images at two planes simultaneously

Angiography enables imaging and evaluation of, for example, narrowing in the neck arteries (stenoses), vascular occlusion (for example in stroke), aneurysms in the neck or brain vessels, vascular malformations (fistulas, arterio-venous malformations) or tumours. This may be necessary for diagnosis and planning of possibly required operations or minimal-invasive treatment.