General information about the MRT
Magnetic resonance imaging (MRI) is based on the magnetic properties of tissue, especially tissue water. To display MRI images, a very strong magnetic field is required, which is more than 100,000 times stronger than the magnetic field of the earth. This magnetic field is generated by the MR tomograph.
In addition, high-frequency electromagnetic waves (radio wave range) are required, which are generated by special coils. These coils also receive the signal emitted by the body tissue. By additional application of location-dependent magnetic fields, the signals can be assigned to different body regions and in this way the MRI images can be calculated.
If the safety measures are observed, the MRI of the hand, in contrast to X-rays, is a completely harmless examination method. Diagnostically, an MRI examination of the hand is used to differentiate between traumatic, degenerative, inflammatory and tumorous diseases of the hand skeleton, including the wrists and surrounding soft tissues, or to clarify in general whether a pathological finding is present. In most cases, the MRI examination is preceded by X-ray diagnostics.
The disadvantage of MRI is the high costs associated with an examination. It is about four times more expensive than computed tomography and about ten times more expensive than an X-ray examination. Before a magnetic resonance tomography can be performed, it must first be ensured that the patient is not carrying any ferromagnetic substances on or in himself.
Ferromagnetic materials either trigger a magnetic field themselves or are attracted by an external magnetic field. This applies to certain implants, dentures and pacemakers, which is why such patients are generally excluded from MRI examinations. Due to the ferromagnetic potential, all metal-containing clothing, watches, jewelry, etc.
must therefore be removed before the examination. Before the examination, the patient is given an indwelling cannula in a vein through which the contrast medium is administered during the examination. When performing a hand MRI, the patient is either placed in a prone position with the arm stretched out above the head or in a supine position with the arm placed sideways. For the best possible image quality, the hand is fixed and a receiving coil is placed over the hand. An MRI examination usually takes between 25 and 30 minutes.
