MRI differs from CT (computed tomography)?


  • Contraindications
    1. General contraindications
    2. Contraindications to computed tomography
    3. Contraindications to magnetic resonance imaging
  • Sensitivity to tissues and organs
  • Advantages of methods
    1. The advantages of CT
    2. The advantages of MRI
  • Conclusion
  • With the advent of MRI and CT, modern medicine has got the possibility of quick and accurate diagnosis of pathology of different organs that can detect the disease in its early stages, and accordingly, it is possible to treat them. A huge contribution to early diagnostics of oncological processes contributed to the emergence of a new method of PET CT, which opens up enormous opportunities for oncologists.

    The latest devices for MRI and CT studies have higher resolution and often compete with each other for leadership in the diagnosis of a disease, but having fundamental differences, each method has its niche and is indispensable in some situations.

    Similar in appearance to the devices for carrying out both diagnostic procedures sometimes lead to the fact that not having a medical education, people consider them one and the same study «in the pipe». However, research completely different way of obtaining diagnostic information and, accordingly, significantly different side effects and contraindications.

    The principle of operation

    The principle of computed tomography

    Method information on the computer tomograph based on the use of x-ray beam, as in the case of conventional radiographs. The x-ray beam penetrates the human body in a spiral, making a layered transverse images with a short interval, in modern CT scanners can obtain slices in two millimeter. Hence the second name – spiral computed tomography (SCT).

    The principle of operation of PET

    PET (positron emission tomography) combines two methods of data collection: the first is computed tomography, the second is the influence of radioactive elements that accumulate in certain tissues, allow you to assess the condition of the organ and the presence of pathology in it.

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    The principle of operation of magnetic resonance imaging

    Magnetic resonance imaging also allows to do cross-scans with the minimum interval, but the way information is fundamentally different from KT: working on the fabric by the pulse, by creating around you a strong electromagnetic field, analyze the return pulses.


    Because the effect on tissue during MRI and CT is completely different ways, and contraindications to the procedures are very different. Although there are General contraindications for both studies.

    General contraindications

    • Severe claustrophobia.

    • Obesity, the degree of which is limited by the size of the diagnostic cavity (pipe).
    • Serious mental disorders that do not allow the patient to lie still during the study.
    • Other reasons that do not allow the patient to be supine the supine position during the study.

    Contraindications to computed tomography

    As the study relates to x-ray methods, accompanied by high radiation exposure, CT has the following contraindications:

    • Pregnancy (absolute contraindication).
    • Breast feeding (absolute contraindication).
    • Children’s age (relative contraindication).

    Also because of the high radiation exposure, harmful to do SKT several areas of the body, and to repeat the study in a short period of time.

    PET CT has the same contraindications as conventional computed tomography.

    However, it should be borne in mind that the progress does not stand still, and modern devices make the load much less valid, which allows, if necessary, to evaluate several departments, as well as to make re-study after a short period of time.

    Contraindications to magnetic resonance imaging

    Creating a strong electromagnetic field carries its limit to perform MRI:

    • The presence of metallic structures in the human body (for example, the apparatus Elizarova).
    • The presence of metallic and electronic implants and prosthetics, including clips on cerebral vessels, artificial pacemaker, dentures, and even tattoos. It is possible to conduct the study if the implant is made of titanium.
    • The first trimester pregnancy (relative contraindication).
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    The negative impact on the human body for MRI does not carry, so it can be done several times within a short time, as well as in pregnant and nursing women and children.

    In the case of CT and PET CT, its negative effects on the body decreases with each new generation of CT scanners, reducing contraindications. Absolutely opposite situation with MRI: the effectiveness of the method increases in direct proportion to the strength of the electromagnetic field. If the first MRI machines creates a field of 0.5 Tesla and less, the latest generate a field of 3 Tesla. The stronger the electromagnetic field, the tighter the restriction for the procedure.

    Sensitivity to tissues and organs

    It is believed that MRI better visualizes the soft tissue, allowing to evaluate not only their structure but also chemical composition, blood flow in them, even without using contrast material. SKT as other x-ray diagnostic methods, more effective in the diagnosis of bone structures, as well as concretions.

    By medical standards adopted worldwide MRI, preference is given to the examination of brain and spinal cord, and it can replace CT in rheumatology and traumatology.

    CT is widespread in the diagnosis of diseases of internal organs and bone structures. PET CT is used in Oncology, allowing us to identify tumors smaller than one centimeter, without manifestations. PET CT scan – direction, which is still developing, and its scope is limited to the ability to choose a radioactive isotope for the respective tissues. But, besides cancer, now PET is used to assess the blood flow in organs such as the heart.

    Advantages of methods

    The advantages of CT

    • The value of computed tomography is much lower MRI apparatus, which affects the difference of the estimated cost of the procedure for the medical institution and the patient when the paid survey.
    • SKT takes much less time, which significantly improves the tolerability of the procedure patients.
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    Advantages of PET over conventional CT include the ability to better diagnose cancer processes in the early stages of development.

    The advantages of MRI

    • Better contrast images compared to CT.

    • You can do not only cross sections but also longitudinal.
    • You can evaluate the blood flow in the examined area and the chemical composition of the tissue.
    • The lack of radiation exposure.


    Currently, three areas of diagnosis are rapidly developing and their advantages and disadvantages, and the difference between them, are moved into the category of relative. Modern scanners, both computer and magnetic resonance, allow to obtain a clear picture of almost all structures of the human body, allowing you to replace the procedures with each other, in the presence of contraindications to one of the methods.

    The dynamic development of the three directions of diagnostics for a long time will find niche applications for each study.

    A huge plus the possibility of choosing between CT, PET and MRI, is not only the possibility to replace each other, but to complement if you are in doubt or controversial issues in the diagnosis. Thus allowing to better see the disease process as before therapy and during treatment.