It is interesting
The main difference between CT and MRI is different physical phenomena which are used in the corresponding systems
During the СТ the X-ray scans is used radiation which provides a picture of a physical condition of substance.
During the MRI scan are used constant and pulsating magnetic fields, as well as radio-frequency radiation which gives information on the distribution of protons (hydrogen atoms), i.e. on the chemical structure of tissues.
During the CT scan the doctor not only sees the tissues, but can objectively determine their X-ray density, which varies with diseases; In the case of MRI, the image is evaluated only visually.
During the MRI scan, in general, soft tissues are better distinguished. Bones in this case can not be seen - there is no resonance from calcium and bone tissue and during the MRI scan it is visible only indirectly.
MRI is more informative:
- In cases of certain types of brain tumors, inflammation of the brain tissue, ischemic stroke (when there is no hemorrhage in the brain tissue), multiple sclerosis;
- In cases of lesions of the nervous tissue of the spinal cord (not the spine!);
- In cases of lesions of cartilage, ligamentous apparatus, muscle tissue.
CT is more informative:
- In acute intracranial hematomas, hemorrhagic strokes, brain trauma and skull bones;
- In lesions of the bones of the base of the skull, paranasal sinuses, orbits, temporal bones, as well as bones of the facial skeleton, jaws and teeth;
- In aneurysms and atherosclerotic lesions of vessels of any localization (CT angiography);
- In sinusitis, otitis, defeat of the pyramids of the temporal bones;
- In injuries and degenerative-dystrophic diseases of the spine (compression fractures, osteochondrosis, protrusion and disc herniation).
- When diagnosing lung tumors, tuberculosis, pneumonia, and also for clarifying difficult chest radiographs for treatment of chest radiographs;
- With the pathology of the chest and mediastinum;
- In the diagnosis of interstitial and fibrotic changes in the lung tissue, as well as for the detection of peripheral lung cancer at an early, preclinical stage;
- In the diagnosis the whole spectrum of abnormal changes in the abdominal cavity, retroperitoneal space and pelvic cavity;
- In injuries and diseases of the bones of the skeleton, which can not be detected with conventional radiography;
- In preparation for surgical interventions on internal organs. The preoperative three-phase CT scan which includes the angiographic phase, allows to obtain the optimal anatomical picture in the operative intervention zone.
It is very important to know that MRI is contraindicated in the presence of:
- Metal structures in bones or metal objects in soft tissues (e.g. bullets or foreign bodies requiring surgical removal);
- Artificial pacemaker;
- Internal hearing aid;
- Fixed metal dental bridges, pins or crowns;
- Metal staples or clips left in the body after surgical operations;
- Cava filters.
It should also be remembered that an MRI can not be performed:
- In people with a fear of confined space (claustrophobia) and in patients with inadequate behavior.
- Patients weighing over 100 kg.
For CT scan all of the above contraindications do not matter.
In addition, the duration of a CT examination is up to 1 min; the duration of a MRI examination is from 30 to 45 minutes (in confined space).
In accordance with this, the cost of MRI is 30-40% higher than that of CT.