Magnetic resonance

In September 2009 a new magnetic resonance machine was installed in the PMT Clinic Brno – a Magnetom Essenza 1.5 T from the company Siemens. This is a cutting-edge instrument of this renowned manufacturer.

With the Magnetom Essenza machine we installed a radiology information system from the company ICZ allowing the sharing and sending of results of examinations by secure electronic route e-PACS.

1. Ordering times up to 14 days
2. Capacity reserved for acute cases every day
3. Comfortable clinic with modern fittings
4. Diagnostics at the highest level
5. Expansion of examination spectrum to include MR angiography and possibility of oncology screening

The personnel have a very high level of knowledge and are capable of utilising the possibilities of the technology in favour of the patient.

What is magnetic resonance - MR

Magnetic resonance is a modern examination method which displays an image of the required area of the human body very precisely and in detail. The individual organs of the human body scanned in thin layers (slices) usually 1-5mm thick. This imaging method does not work on the principle of X-rays, but it uses a very powerful magnetic field. This examination is safe and is conducted without potential harmful ionising radiation.

The results provide doctors with very important information about practically all the organs in the body. Magnetic resonance - this method is very often used when examining the brain, spinal column and is irreplaceable for neurological, orthopaedic and oncological examinations. This imaging method is used in particular if there is a suspicion of vascular or tumourous diseases of the brain, in the case of various spinal injuries and prolapsed intervertebral disks. It plays an equally important role in examination of the locomotive organs. The one thing which magnetic resonance cannot provide a good image of are bones, which contain virtually no water.

Principle for functioning of magnetic resonance - MR

Two thirds of the human body consists of water, so water is present in all tissues. MR only works with tissues containing water, and therefore hydrogen. A water molecule consists of two hydrogen atoms and one oxygen atom. A hydrogen nucleus consists of a single proton. This proton rotates very rapidly, and the combination of the proton’s charge and its rapid rotation generates a magnetic field. Due to its magnetic field a hydrogen proton has a strong magnetic moment. This means that if a proton ends up in an external magnetic field, its magnetic field will orient itself in parallel with the lines of force of the external field. Moreover the proton revolves around the axis.

If we put a person in a strong, homogenous magnetic field, all the hydrogen atoms in the person’s body have a processional movement in parallel with the external magnetic field. Why? The protons conform to the field as a result of the magnetic field. Naturally some atoms line up their axis in the direction of the external field, and others in the opposite direction. The magnetic fields of such a pair of protons cancel each other out. Magnetic resonance can only work with those solitary atoms which do not cancel out each others’ magnetic field. Out of a million atoms there are only a few, but in spite of this they are sufficient for perfect scanning of human tissues. The MR scanner “sees” them, and its eyes are radiofrequency energy (RF) impulses. They are nothing but radio waves (which we know, for example, from the use of radio and television).

The MR scanner also has transmitting and receiving antennae. Both of these roles are taken by special coils which are located as close as possible to the patient’s body. Every scanner is equipped with body coils and head coils, but there are also knee coils, for example. The coil antennae transmit RF waves at a specific frequency, the energy of which is absorbed by the hydrogen atoms. The transmission forces the atoms to perform a processional motion in a certain other frequency and in a certain other vector. When the coils stop transmitting, the vectors of the atoms return to the original position (they are forced to do this by the strong external magnetic field), and at this moment the atoms radiate the absorbed energy. The tissue “lights up” for a moment and the atoms transmit “resonance waves” This “weak light” – in reality an unbelievable amount of unbelievably weak high-frequency signals – is detected by the coils, which have been turned from transmitting antennae to receiving ones. This process is repeated periodically once every 30 to 3000 milliseconds.

Magnetic resonance - imaging

An image is gained by the action of the magnetic field and radio frequency pulses on the nuclei of hydrogen atoms, which are part of every water molecule - H2O - and water is contained to a greater or lesser extent by all tissues in the human body.

The hydrogen contained in a water molecule rotates constantly around its axis, and it has its own magnetic moment. As a result of the magnetic field and short radio frequency pulses this hydrogen nucleus deviates from the axis of its rotation, and when the radio frequency pulse is halted, it returns to its original state, and during this return it emits a weak but measurable signal of electromagnetic energy.

These signals are processed by a computer to make a final image – a cross-section of the examined part of the body where the structures of the organs and tissues are differentiated from each other in a wide range of grey tones (from white to black).