CT or MRI: choose the best method of hardware diagnostics. What is the difference between CT and MRI Mri or who is better

Chief Freelance Specialist in Radiation Diagnostics of the Moscow Department of Health, Director of the Scientific and Practical Center for Medical Radiology of the Moscow Department of Health, President of EuSoMll and the Moscow Branch of POPP, Doctor of Medical Sciences, Professor

Hardware diagnostics allows you to see the organs from the inside. This makes it possible to more accurately determine the degree of damage and the course of therapeutic manipulations. Medical errors and incorrect diagnoses are a thing of the past: modern medicine has several types of diagnostic devices. Consider the difference between CT and MRI. Which type of scan is more informative, and which is safer for health?

Computed and resonance tomography

A CT scan is a computed tomography scan that scans the internal organs of the body using x-rays. Unlike conventional radiography, the device gives a three-dimensional image instead of a two-dimensional one. The device takes a whole series of images from different viewing angles, which are processed by a computer program. As a result, the doctor receives a three-dimensional image of the organ under study.

The patient is placed on a special couch, around which there is a ring-shaped device. X-rays scan the patient from all sides. Depending on the program settings, you can get not only an image of the whole organ, but also its section. All this allows you to get the most accurate picture of the state of the organs.

MRI is magnetic resonance imaging. How is CT different from MRI? The difference between an MRI and a CT scan is the nature of the waves used - a CT scan is done using a magnetic field. Otherwise, the operating principle of the devices is similar: a computer program transforms wave signals into a three-dimensional image.

Note! The difference between CT and MRI lies in the different nature of the waves used to scan the organs of the body.

However, differences in the nature of the waves are not the whole story. CT and MRI are used to diagnose various types of pathology. For example, MRI of the liver or computer diagnostics of the joints.

CT is more often used to detect the following diseases:

• joints, spine, bones and teeth;
• injury to internal organs;
• brain;
• thyroid gland;
• chest;
• abdominal organs;
• urinary organs;
• vessels.

CT scans neoplasms, cysts, stones in organs well. The study of vessels and hollow organs is carried out with the help of the introduction of a contrast agent, which highlights them in the picture and allows you to better see the lesions.

Resonance diagnostics is used mainly for scanning the soft tissues of the body:

• neoplasms;
• spinal cord and brain;
• muscles and ligaments;
• MRI of the liver;
• joint sheaths.

Sometimes a hardware examination of an organ can be performed on both tomographs - CT and MRI, for example, MRI and CT of the brain. What to choose - MRI or CT, which tomography is better? If there is no fundamental indication for conducting diagnostics on a particular device, patients choose CT scans: resonant examinations are more expensive.

Health safety

We found out what is the difference between CT and MRI. It consists in using various physical phenomena. Everyone knows what an x-ray is: it has long been used in medicine. X-ray radiation is harmful to health, so you should not take pictures often. X-rays are used in CT, which brings undoubted harm to health.

The magnetic field used in resonance diagnostics is completely safe for health. The difference between an MR Tomograph and a CT scan allows you to examine the tissues of the lungs and other organs of the body for pregnant women and young children from birth. The only disadvantage of resonance diagnostics is the high price.

X-ray diagnostics (RKT) is much cheaper, but it should not be used too often. Magnetic examination can be carried out repeatedly, for example, MRI of the liver during the course of therapy or in the postoperative period.

Disadvantages and contraindications

Despite the differences and similarities, both types of hardware scanning have their own advantages and disadvantages. Let's consider in more detail.

Disadvantages of resonance examination:

• it is impossible to conduct an examination of a patient with metal implants;
• insufficiently good result of scanning of hollow organs (CT of the abdominal cavity is more effective, as well as CT of the lungs);
• the patient must be immobile for a long time.

Disadvantages of a computer survey:

• differs from MRI by harmful X-rays;
• does not characterize the functionality of organs - only an image;
• it is impossible to examine pregnant women and small children;
• frequent use is contraindicated.

Before the appointment of the examination, laboratory tests are carried out to ensure the safety of both types of diagnostics. Although MRI is better than CT, patients are more likely to choose a computer-assisted examination.

Contraindications to computer diagnostics:

• pregnancy / lactation;
• small children under 5 years old;
• plastered limb;
• kidney failure.

Contraindications to resonance diagnostics:

• mental disorders;
• claustrophobia - fear of closed spaces;
• implants of their metal;
• obesity (more than 100 kg);
• first trimester of pregnancy;
• kidney failure.

Note! Renal failure is an obstacle to both diagnostics, if the introduction of contrast agents into the body is implied.

Preparation for the procedure

How to prepare for a CT scan correctly? There are no special restrictions before the examination. Doctors recommend to refrain from heavy and coarse food the night before and not to drink alcohol. Before visiting the diagnostic room, you need to remove any jewelry. The examination is carried out without outerwear.

Important! Computer examination does not provoke cancer.

How to prepare for a resonant examination? Here, the conditions for preliminary preparation are the same - do not drink alcohol on the eve of a visit to the doctor and do not eat hard-to-digest and solid food. Before visiting the office, you must remove all accessories and jewelry from the body and from the pockets of clothing. In the presence of metal implants, the procedure is not performed - keep this in mind.

A contraindication to MRI is the presence of a tattoo with iron pigments, a pacemaker, and permanent makeup. Find out all the details of the resonant scan in advance.

Outcome

Medicine has taken a big step forward in the field of diagnosing diseases, thanks to the invention of perfect scanning devices. The modern age, characterized by an innovative approach to the examination of body systems and organs, was marked by new discoveries in the field of radiography and tomography. How do new technologies differ from old ones? First of all, obtaining a three-dimensional three-dimensional image of organs and their sections.

Now it has become possible to study the pathology in detail, visually observing deviations in the structure of organs. It also became possible to study the pathology of the functioning of the organ, for example, MRI of the liver shows its current state. However, there are differences between scanning devices: computer diagnostics better shows the image of solid and hollow structures of the body, and resonant diagnostics shows the soft tissues of the body.

The choice of one or another hardware examination largely depends on the organ or part of the body being examined. If diagnostics can be carried out on both devices, for example, CT and MRI of the brain, it is better to choose resonance scanning. The price of MRI is higher, but it is safer for health.

The effect of X-rays in diagnostic terms cannot be overestimated. Despite the fact that their properties were discovered many years ago, even more informative techniques - MRI and computed tomography - appeared much later. However, scientists have managed to improve the above devices, having made a revolutionary breakthrough in the study of internal organs and systems of the human body, identifying possible pathologies. Standard x-rays are not as accurate. Often, with this method of examination, inflammatory processes or neoplasms are still hidden from the keen eyes of doctors. With the invention of new devices, diagnostic medicine has reached a new level of development.

CT and MRI are two different research methods

In this article you will learn:

There is a difference between MRI and CT, despite the fact that these devices seem identical to the average person. It's all about different types of radiation, with the help of which doctors determine the presence of certain diseases in the patient's body. The basis of CT is X-rays, MRI is an electromagnetic field.

So, in the case of CT, you can study some organs and systems, and through MRI, others. The MRI machine responds to the “recall” of an organ when exposed to electromagnetic radiation. Comparison of CT and MRI also lies in the methods of preparation for examinations and possible consequences, side effects.

What is the purpose of MRI

The doctor receives the data already modeled. Three-dimensional images of organs are displayed on the screen of the device. At the same time, the principle of obtaining information is similar to computed tomography, but the nature of the waves varies significantly. Due to this, it is possible to study certain organs by means of apparatuses. Therefore, the question of what is more informative - CT or MRI - cannot take place. For some diseases, CT is indicated, for others, MRI.

The MRI machine works on the basis of magnetic radiation

Under the influence of the radiation of the magnetic resonance imaging device, each of the organs of the human body gives a kind of "answer". Information is recorded and properly processed. All signals are converted. A three-dimensional image of the organ is obtained. At the same time, the doctor of the diagnostic center has an idea not only of the size of the organs, but also of the existing pathologies, since the system provides data in literally detail. The doctor easily rotates images, zooms in and out.

What is CT

This abbreviation stands for computed tomography. The examination consists in the action of x-rays. However, this is not an x-ray in our usual sense. The old method involves imprinting the organ on a specialized film. The picture is often incomprehensible even to the radiologists themselves.

CT provides a three-dimensional image of the desired organ, since it is based on the activity of a three-dimensional system. The device "removes" information at the moment when the patient is on the couch. At the same time, a lot of pictures are taken from different angles. After the received information is processed and issued in the form of a three-dimensional picture on the screen of the device.

The information content of this technique directly depends on the features of the device settings.

When is an MRI performed?

This diagnostic method is good when you need to look at the state of blood vessels and body tissues. Patients come for MRI with suspected neoplasms in any organs. Often, by means of magnetic resonance imaging, the state of the vessels of the brain, the features of the work of the heart are assessed. At the same time, no one canceled ultrasound, but it is important for doctors to have a complete and versatile picture of the patient's condition.

MRI is often used to study the condition of the spinal cord.

With the help of MRI, the activity of the structures of the spinal cord and nerves is assessed. It is important to be screened for stroke patients. Patients suffering from arthrosis and arthritis have the right to demand from the attending doctor a referral for an MRI. Diagnostics will look at the condition of muscle structures, as well as joints and cartilage.

What are the indications for CT

This machine helps doctors understand if a patient is bleeding internally. In injured patients, surgeons look at the type of damage, their volume. CT provides important information about the condition of the teeth, bones, and joints. The presence of osteoporosis and other ailments of the skeletal system and spine is clearly visible.

Computed tomography is an excellent way to detect tuberculosis, pneumonia, anomalies in the development and activity of the thyroid gland. Diagnostics on CT is indispensable when you need to find out about the state of the gastrointestinal tract or urinary system.

CT helps diagnose various lung diseases

Is CT dangerous?

Computed tomography is contraindicated for pregnant women, since the examination is based on x-rays that are dangerous to the fetus. Nursing mothers are also asked to refrain from this diagnosis, or not to feed the baby for some time, expressing harmful milk.

CT scans are done for children when other methods are powerless, and the harm from the diagnostics on the equipment itself is less than what the disease can cause.

Computed tomography is contraindicated in patients with pathologies of the kidneys, thyroid gland, unstable blood sugar levels. CT diagnostics is useless when the patient is overweight - over 200 kg. And the table itself, where the sick are placed, will not withstand such a load. Another nuance: CT scans should not be done for epileptics, since a seizure can begin at any time. Examination on the apparatus is carried out in complete rest. Nervousness, tremor is not allowed.

As for harmful X-ray radiation, except for those categories of citizens for whom examination is completely contraindicated, for the rest it is possible to undergo it even once every six months.

CT is a type of X-ray, so it is often not possible to do it.

What are the consequences of MRI

If there are metal implants, plates, prostheses with metal inserts, braces in the body of the subject, MRI diagnostics is contraindicated. The magnetic waves will resonate during the examination. As a result, the consequences will be expressed not only in inaccurate diagnosis, but also in danger to the body.

It is important to remember that even tattoo ink containing metallic impurities can be harmful in the diagnosis of MRI. This is worth considering for owners of beautiful patterns on the skin.

There is also a contraindication for "carriers" of pacemakers. This device in the process of magnetic resonance imaging can simply stop, which leads to disastrous consequences.

In this video you will find information about the differences between CT and MRI, as well as the main parameters of both procedures:

During the examination for more than half an hour, the patient must lie still. This is undesirable for epileptics, patients with claustrophobia and pathologies of the nervous system (Parkinson's disease).

MRI can be done without consequences for pregnant and lactating women. This device does not cause harm to other categories of subjects.

What is the difference in preparation

You can drink a sedative. Special preparation is needed only when the procedure involves the introduction of contrast solutions into the blood for a more accurate diagnosis. With this in mind, doctors are warned not to eat 6-8 hours before procedures, regardless of whether a CT or MRI is done.

Before the CT scan, the patient must remove all metal objects: prostheses, hearing aids, earrings, rings, chains, bracelets. The procedure is carried out in clothes, so it is worth making sure that metal objects are not “littered” in the pockets.

When an MRI of the gastrointestinal tract or urinary system is scheduled, it is better for patients not to eat or drink 8 hours before the procedure, and to follow a special diet in the earlier period. You can not eat foods that cause increased formation of gases in the intestines. These are any vegetables, legumes, bread.

Before an MRI, you can drink activated charcoal, which extinguishes gases in the intestines. It is advisable to drink antispasmodic drugs as prescribed by a doctor. This will help you get the most accurate test result.

Modern diagnostic methods make it possible to detect diseases at the 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 of 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 scanner 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:

• Find 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 patients with 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
• Detect internal bleeding, trauma
• Examine the brain 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 is used when it is really caused by a medical need.

• 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 large or small intestine, the stomach, the patient is given a barium suspension in an aqueous solution. However, non-hollow organs and vascular zones will 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. So, MRI is a diagnostic method that gives the best results when studying organs with a high content of fluid, pelvic organs, and intervertebral discs. CT is prescribed to study the bone skeleton and lung tissues.

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 a faster diagnostic method and is suitable for cases where 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 has 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.

Identifying the causes of the disease, as well as making a diagnosis, is very important. They precede any treatment and are of particular importance - a correctly diagnosed diagnosis affects the speed of recovery. Sometimes a therapeutic examination is enough, but in complex cases, special diagnostic equipment cannot be dispensed with, which includes computer and magnetic resonance imaging scanners, which allow to detect a significant number of diseases of various parts of the body. Let's take a look at each study and determine which way is best?

How is CT different from MRI?

The main difference between these two diagnostic procedures is the method, or rather, the principle of the study.

Computed tomography involves the use of x-rays. They penetrate the area of ​​the body under study, and the received data is processed by a special powerful computer. Unlike a conventional x-ray, a tomograph has several emitting sensors, which allows you to take pictures in two or more planes. Thus, a three-dimensional picture of the examined organs is obtained. The CT examination itself lasts about a minute (the time depends on the type of device).

Externally, the devices for diagnostics, CT and MRI, are not much different, representing a long movable couch with a special “pipe” or “tunnel”. But these two methods use completely different kinds of physical phenomena.

The principle of operation of MRI diagnostics is reduced to the effect of a strong magnetic field on the human body. It causes the protons of hydrogen atoms in the human body to give a weak radio signal, which is picked up by powerful built-in sensors. The information is fed into a special computer, which, in turn, makes a detailed 3D model of the studied area of ​​the body. Sometimes MRI is used as an auxiliary procedure right during a surgical operation, because the tomograph device allows you to observe the processes occurring inside the body in real time. A standard MRI examination takes 30-40 minutes. Before the procedure, the patient removes all metal objects in order to avoid their interaction with the magnetic field. The tomograph takes several consecutive images, between which there are small pauses - at this time the patient may move a little (but movement in the region of the study area is excluded).

Which method is more informative and accurate?

The accuracy of hardware diagnostics is determined by the appropriateness of using a particular method. MRI is relevant in cases where it is necessary to examine soft tissues, the nervous system, muscles, joints, etc. But the skeletal system is visualized with less clarity compared to CT, because skeletal tissues contain only a small amount of hydrogen protons.

Therefore, in diseases associated with tumors, the brain and spinal cord, ligaments, muscles, joints, the doctor will most likely prescribe an MRI. And when it comes to diagnosing pathologies of the skull bones, teeth, blood vessels, chest (for example, tuberculosis and pneumonia), thyroid gland and spine, then computed tomography will be the preferred method.

Which is safer - computed or magnetic resonance imaging?

The principle of operation of a CT scanner is associated with X-ray radiation, which causes, though insignificant, but still harm to health. The radiation load on the body during diagnostic procedures using a tomograph ranges from 2 to 10 mSv (depending on the part of the body being studied). The same amount is the dose of background radiation, on average received by a person for 1-4 years, respectively. That is why doctors recommend undergoing several CT examinations in a row only in cases of emergency.

An examination using a magnetic resonance imaging scanner is considered an absolutely safe procedure. Sometimes you can hear talk about the dangers of MRI, which manifests itself after a few years, but this fact has not been proven by science. Therefore, the procedure can be repeated as many times as required.

But each diagnostic method has its limitations. CT is contraindicated in pregnant women and young children due to the special susceptibility of growing tissues to radiation. The study is often performed using an iodine-containing contrast agent - such a procedure should be avoided in patients with thyroid diseases, renal failure, and severe diabetes mellitus. Computed tomography is rarely prescribed for women during lactation. But if research cannot be avoided, then after it a break in feeding should be at least one day.

Note!
If you have tattoos on your body, you should inform your doctor before the MRI scan. The fact is that some types of paint contain microscopic metallic elements that can distort the results of the study or even cause pain in the patient.

A contraindication to MRI is the presence of ferromagnetic and metallic objects in the patient's body. Under the influence of a magnetic field, they can change their position and harm human health. Therefore, magnetic resonance imaging is not prescribed for people with Ilizarov devices, pacemakers, metal implants, and intracranial metal hemostatic clips.

CT and MRI studies: which is cheaper?

MRI is a “younger” diagnostic method; a modern device with a complex structure and operating rules is used for the procedure. In addition, the amount of time spent on one study is ten times higher compared to CT. Therefore, the method of magnetic resonance imaging is considered more expensive. On average, the difference in price between examinations of the same body part using these two diagnostic methods will be about 1000-2000 rubles. For example, the cost of a CT scan of one segment of the spine will cost 4,000 rubles, and an MRI of this area will cost you 5,000 rubles.

MRI or CT - which is better?

Summing up, we can conclude that, in terms of safety, the undoubted leader is research using magnetic resonance imaging. If we compare both methods in terms of the accuracy of the obtained images, then the result depends on the area under study: organs with a high calcium content are better examined using CT, and MRI is a more suitable procedure for diagnosing soft tissue diseases. In terms of cost, computed tomography remains the preferred option - this method of examination is cheaper.

Tuesday, 04/10/2018

Editorial opinion

Both MRI and CT scans are complex procedures that are not recommended to be performed frequently. Therefore, you should not engage in "self-appointment" or undergo an examination "for prevention." Such studies should be prescribed only by a doctor and only with good reasons for this.