MRI

MRI – (magnetic resonance imaging) – is the painless method of medical diagnostics that allows revealing a disease without radiation exposure. Reasonable advantage of this method is the possibility of use thereof for children of any age and pregnant women. Relative contraindication in claustrophobia.

In our department magnetic resonance imaging is being performed by apparatus Philips Achieva 1.5 tesla, channel (made in Netherlands). This apparatus combines all the necessary for high quality imaging.

In our center the following areas could be examined:

• spinal column;
• brain;
• vessels;
• joints;
• soft tissues.

All the studies could be made with contrast amplification, if required.

Magnetic resonance imaging (MRI) is the method of receiving images of internal organs and tissues using the phenomenon of nuclear magnetic resonance. The method is based on measuring of electromagnetic response of atom nucleus, the most frequently – those of hydrogen atoms, namely based on the distortion thereof by certain combination of electromagnetic waves in constant high magnetic field.

Information for patients

You are recommended to be examined by MRI/p>

This is complicated, but safe and efficient method of diagnostics, not connected with ionizing radiation or insertion of any radioactive substances. The ground for MR-images is magnetic field and radio-frequency impulses. During the study, the patient is placed inside of tunnel of the tomography.

Usually diameter of the tunnel is 70-80cm. It is opened at the both sides. Ventilation and lighting are designed for maximum possible comfort of a patient while examination.

MRI allows receiving clear images of internal bodies and prescribes correct treatment.

If your doctor prescribes you MRI, it doesn't mean that you have a disease; may be your doctor wants to clarify your health conditions.

History of MRI method

MR imaging is based on the phenomenon of nuclear magnetic resonance (NMR). This phenomenon was discovered in year 1946 by the scientists of Stanford and Harvard Universities. NMR means the possibility to absorb or emit energy of radio-frequency impulses by nucleus of some substances (mostly hydrogen), located in magnetic field in case of coincidence of frequency of impulses with frequency of nuclear rotations. In year 1952 F. Blokh and E. Purselia received Nobel Award for this discovery.

In year 1973 Paul Lauterbur received the first MR image. It was the image of two tubules filled with liquid. In year 2003 Paul Lauterbur and Peter Mansfield received Nobel Award for development of MRI method. Peter Mansfield demonstrated who the radio signal received from MR-spectrometer could be transformed into image. The first MR tomography in the USSR was installed in the year 1984 at the Institute of Clinical Cardiology named after A.L. Miasnikov.

Possibilities and advantages of MRI method

MRI is of the most efficient methods for diagnostics of diseases of brain and spine cord, joints, abdominal cavity organs (except for stomach and intestine) and pelvic organs, as well as heart and vessels. Most frequently MRI is applied as a method for clarification diagnostics. The main advantages of MRI are: high soft tissue contrast (ensuring high quality of images of different soft tissues without contrast media) and absence of radiological load.

As a rule, MRI is not applied for examination lungs, stomach, intestine, bones.

Counter indications

Absolute contraindications to MRI are: cardio stimulator (artificial rhythm driver, cardioverter, and pacemaker) or other implanted devices, and presence of metal near to brain or an eye.

In other cases, as a rule, the examination is allowed. Although, before the examination starts, you must notify your doctor of nurse about the following:

Do you have artificial rhythm drivers, prostheses of cardiac valves, artificial joints, claims, filters or other medical devices made of metal inside of your body?

Have you ever undergone surgical operations of brain, heart or other bodies before?

Do you have any other non-medical metal objects inside of your body (chips, shavings)?

Do you suffer from epilepsy, convulsionary attacks, and cases of loss of consciousness?

If you are pregnant, please inform the doctor before examination.

Preparation

You or your doctor will appoint time and date of examination in advance. Usually no special preparation to the examination is required; there are no limitations in food consumption.

Exceptions are MRI examinations of abdominal cavity with MR-cholangiography (it should be performed in fasting state, i.e. not to eat at least 4 hours before examination) and MRI of pelvic organs (it is more efficient if bladder is full - before examination you would better drink several glasses of water). Eating signification amount of food is undesirable, although light breakfast or lunch doesn’t hurt.

Process of examination

Before examination you should take off and leave in specially designed place all items and parts of clothing that are made of or contain metal (hooks, buttons, zippers, buckles etc.). Please check your pockets and remove all metal items (keys, coins etc.), magnetic bearers (cassettes, discs, credit cards). Take off metal jewelry, watch. If your wear cosmetics with metal particles wash it off. Metal teeth as always do not influence reasonably of the quality of image.

A nurse or doctor will invite you to the cabinet for MRI examinations. You will be asked to lie on a table and then you shall be placed inside of a metal tube (magnetic tunnel). During the whole period of examination, the doctor will observe you through video camera. In case of necessity you shall be able to contact the doctor using a special communication device.

In process of examination the necessity could arise to insert contrast media. It is required to better “lighting” of areas that the doctor is interested in. Contrast media for MRI are compounds on the basis of gadolinium, for intravenous insertion of 5-20 ml thereof. Usually this procedure is not followed with any unpleasant feelings or side reactions.

Your main task is to be motionless during the whole period of examination (it usually lasts 20-30 munities). Quality of images depends strongly thereon.

While the examination you will hear rhythmic loud sound of different tones and levels. It is connected with normal functioning of the device.

Results of the examination could be obtained at the next day, or they will be provided to your doctor or to the expert who sent you to the examination. If case of urgent necessity and upon agreement with a doctor, results could be received in 1 hour after the examination.

Before and during the MRI procedure

Before scanning you must take off all metal items, check the presence of tattoos and medical dressings. Duration of MRI scanning is usually 20-30 minutes, but is could last more. Namely, scanning of abdominal cavity requires more time than scanning of a brain.

Inasmuch MRI tomography produce loud noise, one must apply ear protectors (ear muffs or ear plugs).

For some types of examinations intravenous insertion of contrast media could be required.

Before start of MRI, the patients are recommended to be aware of the following: which information shall be received by scanning and how the strategy of treatment shall in influence, are there any contradictions against MRI, will contrast media be applied and for what reasons. Before beginning of the procedure: how long shall last the scanning, where the signal button is and how could you call for stud during the procedure.

Peculiarities of use of medical equipment in the premises, where MRI scanning is performed.

Combination of intensive magnetic field applied for MRI scanning and intensive radio-frequency field makes challenging demands to medical equipment used to examination. It must be of special design and have additional limitations regards using thereof near MRI installation.

Contraindications

There are relative contraindications, in which examination is possible upon certain conditions, are absolute ones, in which examination is unallowable.

Absolute contraindications

• Installed cardio stimulator (changes of magnetic field could imitate cordial rhythm).
• Ferromagnetic or electronic implants of middle ear.
• Big metal implants, ferromagnetic chips.
• Ferromagnetic Ilizarov devices

Relative contraindications

• Insulin pumps;
• Nerve stimulators
• Non-ferromagnetic implants of internal ear;
• Prostheses of cardiac valves (in high fields, in case of suspected dysfunction);
• Blood stoppers (except for those on brain vessels);
• Decompensated heart insufficiency;
• First trimester of pregnancy (nowadays there are not enough evidences of the absence of teratogenic effect of magnetic field, although this method is better compared to X-Ray and CT examinations);
• Claustrophobia (panic attacks while being inside of tunnel of the installation could hinder the examination);
• Necessity of physiology immunity;
• Non-adequacy of the patient;
• Severe / extremely severe condition of the patients by his/her main/concomitant disease;
• Presence of tattoos, made by dyes with high content of metal compounds (could cause burns).

Relative contraindications against MRI are also prostheses of teeth and bracket systems, as they are possible artifacts of field un-homogeneity.

Titanium, widely used for prostheses is not ferromagnetic and is actually safe while MRI; exception is the presence of tattoos, made with dyes containing titanium compounds (i.e. titanium dioxide).

Additional counter indication against MRI is the presence of cochlear implants – prostheses of internal ear. MRI is not allowed in several types of internal ear prostheses, because cochlear implants contain ferromagnetic materials.

If MRI examination is performed with contrast agent, the following counter indications are added:

• Hematopoietic anemia;
• Idiosyncrasy to components of the contrast agent;
• Chronic kidney disease, as in such case the contrast agent could retain in the body;
• Pregnancy of any term, because the contrast agent could overcome placenta barrier, and its influence on baby is still understudied.