Kote research. The difference between computed tomography and magnetic resonance imaging
The main difference between CT and MRI lies in the different physical phenomena that are used in the devices. In the case of CT, this x-rays, which gives an idea of physical state of matter, and with MRI - constant and pulsating magnetic fields, as well as radio frequency radiation, which provides information about the distribution of protons (hydrogen atoms), i.e. about chemical the structure of tissues.
In the case of CT, the doctor not only sees tissues, but can study their X-ray density, which changes with diseases; in the case of MRI, the doctor evaluates the images only visually. Quite often, an MRI or CT scan is prescribed by the attending physician, but, as a rule, it would be better if he did this after consulting with a radiation diagnostician: in a number of cases, instead of expensive MRI, you can use cheaper, but no less informative computed tomography.
In general, MRI is better at distinguishing soft tissues. In this case, the bones cannot be seen - there is no resonance from calcium, and the bone tissue on MRI scans is only indirectly visible. It can be stated that today MRI is more informative in diffuse and focal damage to brain structures, pathology of the spinal cord and craniospinal junction (here CT is not at all informative), and damage to cartilage tissue. CT is preferred in diseases chest, abdomen, pelvis. base of the skull. In some cases, in order to establish correct diagnosis, it is necessary to resort simultaneously to MRI and CT.
MRI more informative:
- Intolerance to a radiopaque agent when its administration is indicated on CT;
- brain tumor, brain tissue inflammation, stroke, multiple sclerosis;
- All lesions of the spinal cord, diseases of the spine, mainly in young and mature people;
- Orbital contents, pituitary gland, intracranial nerves;
- Articular surfaces, ligamentous apparatus, muscle tissue;
- Staging of cancer (with the introduction of a contrast agent, for example - Gadolinium).
- Acute intracranial hematomas, injuries of the brain and skull bones;
- Brain tumors, cerebrovascular accidents (MSCT);
- Damage to the bones of the base of the skull, paranasal sinuses, temporal bones;
- Damage to the facial skeleton, teeth, jaws, thyroid and parathyroid glands;
- Aneurysms and atherosclerotic lesions of vessels of any localization (MSCT);
- Sinusitis, otitis, damage to the pyramids of the temporal bones;
- Spinal diseases, including osteoporosis, herniated discs, degenerative and dystrophic diseases spine, scoliosis, etc. Contrary to popular belief, computed tomography is much more informative for diagnosing lesions of the vertebrae and discs, however, attending physicians are not able to see changes on computed tomograms and recommend patients to have a more descriptive MRI;
- It is preferred for lung cancer, tuberculosis, pneumonia and for clarifying chest radiographs that are difficult to interpret, with pathology of the chest and mediastinum;
- The most sensitive technique for recognizing interstitial changes in the lung tissue, fibrosis and to search for peripheral lung cancer at the preclinical stage (MSCT);
- With almost the entire spectrum of pathological changes in the abdomen;
- Bone injuries and diseases, examination of patients with metal implants (joints, internal and external fixation devices, etc.);
- Preoperative MSCT with three-phase angiography allows obtaining an optimal anatomical picture in the area surgical intervention and recognize the majority pathological processes in the abdominal organs and abdominal cavity.
- metal fragments;
- pregnancy;
- Artificial pacemaker;
- Hearing aid or implants in the cochlea;
- metal implants;
- Fixed metal dental bridges and/or crowns;
- Surgical clips, for example, in the area of an aneurysm;
- Surgical braces;
- Side pillar stimulators;
- Kava filters.
Usage the latest techniques in the diagnosis of the body make it possible to identify on early stages various pathological changes in the work of human systems and organs. Today it is difficult to imagine the development of medicine without non-invasive methods for diagnosing various diseases, namely computed tomography and magnetic resonance imaging. But, faced with the choice of one or another diagnostic technique, it is important to know not only the main differences between MRI and CT, as well as their pros and cons, but it is also necessary to understand under what conditions their use would be appropriate.
Principles of operation and main differences between CT and MRI
For a simple understanding of the main differences between MRI and CT, you first need to understand how they work.
When examining parts of the body using MRI, the patient is affected by both pulsating constant magnetic fields and radio frequency radiation. They are formed by a special apparatus - a tomograph. In a matter of seconds, the device sends a radio frequency pulse to a certain area, which causes the hydrogen atoms in the cells of the body to sway and resonate. Further, special equipment collects the received signals, processes them and outputs a three-dimensional image with chemical structure tissues in this area.
In the case of using the CT technique, the examined part of the patient is exposed in layers to an X-ray beam, which is sent from a special apparatus. Due to the different density of the tissue, the rays are absorbed differently by them, which is fixed by special devices. They process the received data and then issue a layered image of tissue sections, that is, their the physical state.
Which is better, MRI or CT?
Since the method of computed tomography is based on x-rays, the patient is exposed to direct radiation during the study, which is the main disadvantage of CT. New developments of designers made it possible to reduce the radiation dose to a minimum, but still the effect on the patient of radiation remained. This cannot be called a plus.
Unlike CT, when diagnosing the body using MRI, the patient is not affected by any radiation at all, which allows doctors to prescribe it even to pregnant women and children. This is the main difference between MRI and CT. Thanks to him, magnetic resonance imaging has become one of the most safe techniques for research. This is her absolute plus.
In all other respects, MRI differs from CT only in its scope. After reading the information on the site prokishechnik.ru, one can easily understand that MRI is more preferable for focal and diffuse lesions of various parts of the brain, pathologies of the craniospinal junction and spinal cord, as well as for lesions of human cartilage tissue. CT, in turn, is best in diagnosing diseases of the abdomen, chest, base of the skull, pelvis, in detecting tumors, bleeding, etc. Also on the site "about the intestines" the main pros and cons of magnetic and computed tomography are described in more detail, so you special problems find out the answer to the age-old question “Which is better? MRI or CT?
MRI is more informative for
- Inflammation of the brain tissue, brain tumors, strokes, multiple sclerosis;
- Diseases of the spine and any lesions of the spinal cord;
- Muscular tissue and articular surfaces;
- Diagnosis of the contents of the pituitary gland, orbit and intracranial nerves;
- cancer research at different stages;
CT is more informative for
- Diagnosis of circulatory disorders, brain tumors;
- Damage to the teeth, facial skeleton, thyroid and parathyroid glands, as well as jaws;
- Injuries to the bones of the skull, brain and intracranial hematomas;
- Damage to the temporal bones, paranasal sinuses and bones of the base of the skull;
- Diagnosis of otitis, sinusitis and pyramids of the temporal bones;
- For almost all pathologies in the abdomen;
- Atherosclerotic lesions of blood vessels and aneurysms;
- Research on tuberculosis, lung cancer, pneumonia and other chest pathologies;
- Diseases of the spine (herniated discs, osteoporosis, scoliosis, etc.);
- Observation of metal implants, damaged bones and their diseases.
Both of these procedures have identical goals - they are designed for step-by-step scanning of the body, as a result of which the doctor has the opportunity to study the necessary area “in section”. However, the principles of operation of computed tomography and magnetic resonance imaging are completely different, which affects the capabilities of each of these devices.
Physical and functional features of CT and MRI: what is the difference?
The common point for both methods under consideration is that the necessary information is displayed on a computer, so that the doctor has the opportunity to obtain a three-dimensional image internal organs and fabrics.
The main difference in the principle of operation of MRI and CT is in the nature of the waves that are produced by tomographs.
- Computed tomography involves the use x-rays , which emanate from the domed outline. The couch with the patient is placed inside this very contour, which makes it possible to shoot the desired area from a variety of angles.
- The magnetic resonance device operates on the basis of electromagnetic waves . Radio frequency coils, which are located in the field of study, fix the transformations that occur with hydrogen atoms.
Video: Which is better - CT or MRI?
In connection with the application various types radiation, the capabilities of CT and MRI differ.
These differences are detailed in the table below:
|
CT scan |
|
| The best method to date for studying bone structures. Helps to identify pathological neoplasms on the bone, inside it. | Poorly copes with the recognition of fractures. Ideal for identifying injuries associated with ligaments, joints, menisci. |
| Effective in the study of the lungs. | Ineffective in the study of the lungs. |
| Detects calcifications of various parameters. | Small calcifications are not captured by electromagnetic fields. |
| Good for detecting "fresh" brain injuries. | Not always able to recognize hemorrhages in the brain. Does the job perfectly general survey brain states. |
| Can be used for soft tissue diagnostics. | Much better at detecting pathological conditions in soft tissues than any other diagnostic technique. |
| It is applicable to check the organs of the peritoneum and small pelvis, as well as the chest. | Used to study the spinal column. |
Indications for CT and MRI - are there any contraindications?
Magnetic resonance imaging will be more effective in the following situations:
- Impossibility of CT scan due to intolerance of the staining substance by the patient.
- Inflammatory processes in brain tissues.
- Diseases muscle tissue, joints, ligaments.
- Diagnosis of multiple sclerosis.
- Pathological neoplasms of the spinal cord, brain.
- The study of the structure of the pituitary gland, intracranial nerves.
- Determination of the exact stage of cancer.
Despite the information content of both considered diagnostic techniques, in some cases they cannot be assigned. This is due to the specifics of the waves on the basis of which the devices operate.
CT is not performed in the following situations:
- The period of bearing a child.
- Serious errors in the work of the kidneys, thyroid gland.
- Diabetes.
- Patients weighing more than 200 kg. This is due to the fact that the table of the apparatus is designed for a certain body weight.
In addition, CT scans are prescribed for children only if other diagnostic measures have failed.
There are many contraindications for MRI:
- The presence of metal structures in the patient's body, as well as on the surface of the body: metal dental implants,. When using paint for a previously applied tattoo containing metal grains, this procedure is also not prescribed.
- Electrical appliances implanted in the body: hearing aid, pacemaker, insulin pump. Electromagnetic radiation can cause damage to these devices.
- Bouts of claustrophobia.
- Nervous disorders in which the patient cannot long time stay in a stationary position.
For women who are carrying a child, the procedure in question can be carried out from the second trimester of pregnancy.
Video: What is the difference between CT or MRI, for which diseases?
Features of the preparation and conduct of CT and MRI - which type of diagnosis is safer?
- Since both of the manipulations under consideration involve the patient staying a certain amount of time in a stationary state, sedatives may be used before the start of the examination.
- Before any of these procedures, it is necessary to remove all metal objects, incl. Removable dentures, hearing aids. Clothing should be without zippers.
- Due to the use of a contrast medium, it is forbidden to eat and drink before a CT scan.
- Upon completion of the diagnosis, it is necessary to drink more so that the contrast quickly leaves the body.
- In case of hypersensitivity to certain drugs, the patient should notify the doctor in advance. The fact is that iodine-containing contrast agent, through which you can view the internal organs, can cause an allergic reaction.
- With magnetic resonance imaging you need to prepare in advance only when examining the condition of the internal organs of the peritoneum and small pelvis.
In the first case, a couple of days before the manipulation, you should minimize the amount of products that can provoke gas formation.
On the day of the MRI, eating and drinking is prohibited. You should come to the diagnosis of the pelvic organs with a full bladder.
- CT scan takes much less time than MRI: 10 and 40 minutes, respectively.
In some cases, both procedures may be delayed: for example, when using sedatives before diagnosis.
- In terms of security, a kind of "gold standard" is considered Magnetic resonance imaging . The rays produced by the device do not cause any harm to health. This explains the possibility of its use in children and the elderly. In addition, this diagnosis can be carried out as many times as required.
- Functioning computed tomography is directly related to X-ray radiation, which leaves a certain negative imprint on health. Although the dose received by the patient is insignificant, but this is the basis for limiting the passage of several sessions of CT diagnostics in a row.
Each of the considered methods has a number of advantages:
- Low chance of developing side effects upon completion of the survey.
- Absence pain at the time of the research.
- Obtaining accurate and reliable information regarding the state of internal organs, tissues and bone structures.
Modern diagnostic methods make it possible to detect diseases on initial stages. Today it is impossible to imagine medicine without two important acronyms - CT and MRI. Given that both diagnostic methods go hand in hand, people ignorant in medicine constantly confuse them and do not know which method to give preference to.
Many people believe that computed tomography and magnetic resonance imaging are identical. This is an erroneous statement.
In fact, they have only the word "tomography" in common, which means the issuance of images of layered sections of the analyzed area.
After scanning, the data from the device is sent to a computer, as a result, the doctor examines the images and draws conclusions. This is where the similarities between CT and MRI end. The principle of action and indications for their implementation are different.
How are both of these methods different?
To understand the differences, you need to understand the technique of conducting.
Computed tomography is based on x-rays. That is, CT is akin to X-ray, but the tomograph has a different way of recognizing data, as well as increased radiation exposure.
During CT, the selected area is treated with x-rays in layers. They pass through the tissues, alternating density, and are absorbed by the same tissues. As a result, the system receives layer-by-layer images of sections of the whole body. The computer processes this information and produces three-dimensional images.
MRI diagnostics is characterized by the influence nuclear magnetic resonance . The tomograph sends electromagnetic pulses, after which an effect occurs in the area under study, which scans and processes the equipment, then displaying a three-dimensional image.
From the above, it follows that MRI and CT have a significant difference. In addition, computed tomography cannot be performed repeatedly due to the large radiation exposure.
Another difference is the research time. If 10 seconds is enough to obtain a result using CT, then during an MRI a person is in a closed “capsule” from 10 to 40 minutes. And it is important to maintain complete immobility. That is why magnetic resonance imaging is not performed on people suffering from claustrophobia, and children are often given anesthesia.
Equipment
Patients cannot always immediately determine which device is in front of them - MRI or CT. Outwardly, they are similar, but differ in design. The main component of a CT scanner is a beam tube, MRI is an electromagnetic pulse generator. Magnetic resonance imaging scanners are of closed and open type. CT does not have divisions of this kind, but has its own subtypes: positive emission, cone beam, multilayer spiral tomography.
Indications for MRI and CT
Often, the patient prefers the more expensive MRI method, believing that it is more effective. In fact, there are certain indications for conducting these studies.
MRI is prescribed to:
- Detect tumors in the body
- Determine the condition of the membranes of the spinal cord
- To study the nerves located inside the skull, as well as the structures of the connective tissues of the brain
- Analyze muscles and ligaments
- Examine the sick multiple sclerosis
- To study the pathology of the surface of the joints.
CT is prescribed in order to:
- Examine bone defects
- Determine the degree of joint damage
- Reveal internal bleeding, injury
- Examine the head or spinal cord for damage
- Detect pneumonia, tuberculosis and other pathologies of the chest cavity
- Establish a diagnosis in the genitourinary system
- Define vascular pathologies
- Examine hollow organs.
Contraindications
Considering that computed tomography is nothing but radiation, it is not recommended pregnant women and during lactation.
Magnetic resonance imaging is not performed in the following situations:
- presence metal parts in the body and on the human body;
- claustrophobia;
- located in tissue pacemakers and other electronic devices;
- sick, suffering nervous pathologies who, due to illness, are not able to be immobile for a long time;
- patients weighing over 150-200 kg.
MRI and CT in questions and answers
- Is CT always better than X-ray?
If the patient has pulpitis in the tooth or a normal bone fracture, an x-ray is sufficient. If it is necessary to clarify the diagnosis of an unclear nature, to determine the exact location of the pathology, more information will be needed. And here is already shown computed tomography. But the doctor makes the final decision.
- CT does not emit radiation?
On the contrary, when performing computed tomography, the radiation exposure is even higher than with a simple x-ray. But this type of research is prescribed for a reason. This method used when it is truly medically necessary.
- Why is a contrast agent injected into a patient during a CT scan?
In black and white images, contrast helps to create clear boundaries of organs and tissues. Before studying the colon or small intestine, the patient's stomach is injected with a barium suspension into aqueous solution. However, non-hollow organs and vascular zones require a different contrast. If the patient needs an examination of the liver, blood vessels, brain, urinary tract and kidneys, he is shown a contrast in the form of an iodine preparation. But first, the doctor must make sure that there is no allergy to iodine.
- Where is the efficiency higher: with MRI or CT?
These methods cannot be called substitutes for each other. They differ in the degree of sensitivity to certain systems of our body. Yes, MRI is diagnostic method, which gives the best results when studying organs with a large content of fluid, pelvic organs, intervertebral discs. CT is prescribed for research bone skeleton and lung tissue.
To establish an accurate diagnosis for problems with the digestive organs, kidneys, neck, CT and MRI are often of equal importance. But CT is considered more fast way diagnostics and is suitable for cases when there is no time to scan with a magnetic resonance tomograph.
- Is MRI safer than CT?
With magnetic resonance imaging, radiation exposure is excluded. But it should be understood that this is a young diagnostic method, so it is still difficult to determine what consequences it has for the body. In addition, MRI more contraindications(the presence of metal implants in the body, claustrophobia, a pacemaker installed).
And finally, once again briefly about the difference between CT and MRI:
- CT involves x-rays, MRI - affects the electromagnetic field.
- CT examines the physical state of the selected area, MRI - chemical.
- MRI should be chosen for scanning soft tissues, CT for bones.
- With the behavior of CT, only the part under study is in the scanned device, with MRI - the entire body of a person.
- MRI may be performed more frequently than CT.
- MRI is not performed with claustrophobia, the presence of metal objects in the body, body weight over 200 kg. CT is contraindicated in pregnant women.
- MRI is safer in terms of the degree of impact on the body, but the consequences of the influence of a magnetic field are not yet fully understood.
So, we have analyzed the differences between MRI and CT. In any case, the choice in favor of one or another research method is made by the doctor based on the patient's complaints and the clinical picture.