Brain and spinal cord imaging tests

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Imaging provides useful information about processes that take place in the human body. Neuroradiology makes it possible to visualize the nervous system, in particular the central nervous system (brain and spinal cord) and its blood supply. The main radiological examinations available areultrasound, CT scan, MRI, angiography and scintigraphy. Conventional x-rays give mostly information on solid tissues, such as bones, and less on soft tissues and blood vessels. Even on a photograph of the spine, a compression of nerve tissue can go unnoticed.

Ultrasound

Ultrasound is a test that uses sound waves to get a picture of organs in the body. A probe emits this ultrasound. They are then sent back to the probe after having “bounced” (reflected waves) off the elements present in the body. These reflected waves are converted into images on a screen. This technique does not use radioactive rays. It is therefore safe.

It is a good test to check for narrowing of the arteries that bring blood to the brain (carotid arteries). In children in whom the fontanelles (the soft parts of the newborn’s skull) are still open, ultrasound is useful to assess brain tissue, a possible bleeding (haemorrhage) and the amount of fluid in the brain.

CT scan (scanner, computed tomography)

The CT scan makes it possible to see the body as if it were cut into thin slices. The size and exact location of a lesion can thus be accurately estimated. A disadvantage is that it is necessary to record a large number of images, and that this technique uses radioactive rays, which means that the radiation dose is relatively large.

Recordings can be made after administration of a contrast medium, which increases image quality. Finally, this examination can be combined with other techniques such as angiography (angiography or CT angiography: CT scan with injection of contrast product) and isotopic examinations (perfusion imaging).

The CT scan is currently the exam of choice. It can be executed very quickly and allows you to know whether or not it is a cerebral hemorrhage or a brain infarction. It is less suitable for examining the spinal cord.

MRI (NMR)

MRI (Magnetic Resonance Imaging) or NMR (Nuclear Magnetic Resonance) uses a strong magnetic field. The device does not use spokes. The images are formed in 3 dimensions (height, width and depth): thus, a very precise image is created, and a lesion can be perfectly localized. Headphones are put on your ears because this exam makes a lot of noise. MRI cannot be performed if metal is present in the body (pacemaker, clips from previous procedures, metal prosthesis, etc.).

The exam is expensive and time consuming. The number of MRI machines is limited, so it sometimes takes a long time to get an appointment.

MRI provides the images with the most precise details. It can be used for both a brain exam and for examining the spine and spinal cord. For this last examination, it is even possible to obtain a vertical (longitudinal) image which gives information on the entire length of the spine.

Combined with an angiogram (angiography-MRI: MRI with injection of contrast product), this gives very precise images of the blood vessels. The exam is therefore very suitable for preparing for an operation on an artery.

Angiography (arteriography)

Angiography makes it possible to obtain images of the arteries and of the heart after injection of a contrast product. Injecting a contrast medium into the artery causes stroke during the examination in about 1 in 100 people. For an angiogram, hospitalization is necessary.

This examination gives an accurate picture of the blood vessels and their possible enlargements (aneurysms) and strictures (strictures). It is mainly used to visualize the arteries which bring blood to the brain (carotid arteries) and their branches in the brain, the arteries of the spine and the spinal cord, as well as the large artery which starts from the heart and goes down in the thorax and abdomen (aorta). It is especially useful for detecting abnormalities in blood vessels (narrowing and dilation), bleeding and tumors.

Scintigraphy

Scintigraphy requires the injection of a radioactive substance. As this contrast medium spreads throughout the body, the scan provides images of the entire body. This product will concentrate in the places where there are certain anomalies. Scintigraphy is usually complementary to other tests when the diagnosis is not entirely clear, and to obtain additional information.

This technique makes it possible to visualize tumors and possible metastases, for example.

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Source

Foreign clinical practice guide ‘Clinical use of neuroradiological imaging’ (2000), updated on 08/28/2017 and adapted to the Belgian context on 11/06/2019 – ebpracticenet