Limitations of fMRI for brain scanning

محدودیتهای fMRI

Limitations of fMRI for brain scanning

High-quality images can only be obtained if the subject is completely still during the imaging process and holds his breath, if he is told to do so. If you are nervous, confused, or in severe pain, you may lie down. It is very difficult to work inside the device during imaging. A person who is very big cannot be the subject of MRI devices. The presence of devices implanted in the body or other metal objects makes it difficult to take a clear image. The movement of the patient can also cause the same effect.

MRI is not recommended for severely injured patients. This is because many traction devices and many critical equipment must be kept away from the imaging areas. Additionally, fMRI is more time-consuming than other imaging modalities.) As usual, CT and X-ray imaging and the results may be available immediately, especially in a situation where the person has been traumatized.

Although no evidence has been reported so far indicating that magnetic resonance imaging is dangerous for the fetus, it is generally recommended that pregnant women not participate in fMRI examinations, except with the permission of a doctor and for the medical purposes of MRI. fMRI is often more expensive than other imaging methods in addition to taking longer. It is still a method in progress and improvement, and even though it seems to be much more suitable for finding the location of brain activities than other methods, overall there is less experience with fMRI than other MRI methods.

In order to make decisions in sensitive cases, the doctor may prescribe other related tests in addition to fMRI (such as brain surgery). Like any other method, fMRI has advantages and disadvantages, and for its usefulness, the tests that use it They should be carefully designed and should aim to maximize its strengths and minimize its weaknesses.

Advantages of fMRI limitations for brain scanning

In this method, brain signals are recorded without being exposed to the risk of ionization, which is unavoidable in other methods such as CT and PET. It has a high spatial resolution, typically 3-5 mm. Using this method, all Brain regions recorded the signal, unlike EEG or MEG, which are located around superficial cortical areas.

Disadvantages of fMRI limitations for brain scanning

BOLD signals are an indirect method of measuring neural activity and, as previously stated, can be influenced by parameters other than the experimental presentation. BOLD signals are strongly related to the input given to an area rather than its output. Therefore, it is possible is that the BOLD signal is present in a given region even if there is no activity. This method has a low time resolution. The peak of the BOLD response is approximately 5 seconds after neurons in a region start to fire.

Although the presence of layered stimuli can increase the temporal resolution, at the same time it causes a decrease in the collected data points. expands and also attention. Although there is no known long-term harmful effect of static magnetic field on biological tissues, it can cause injuries by pulling heavy metal objects and throwing them. The most common danger for people who fMRI test gives fear of closed environment.

Scan sessions cause the person to be exposed to audio noises caused by gradient wires. Switching gradients induces current in the body which can cause nerve irritation. Medical devices placed in the body can trigger pacemakers. due to the same currents, the radio frequency field of the stimulation of the SIM pages can cause the body to heat up, and people who have fever, diabetes or blood circulation problems should be carefully monitored for this possibility. Local burns Necklaces and jewelry are also dangerous due to the heating of metals.

Clinical applications of fMRI

fMRI data and images can be used in various fields where we need to examine brain function. These images are of great interest in the field of neuroscience and are mainly used to investigate and find out how a cognitive activity is presented in the brain. It is placed, in addition to this, it is of great interest to model cognitive activities and to investigate some brain and neurological diseases Is expressed.

Mapping of the areas related to speech before surgery, assessment of plasticity after brain damage, assessment of patients with disorders of consciousness (coma, vegetative state, minimal state of consciousness, and look-in syndrome) among the applications of fMRI in research fields. Mention the following.

Mapping of complex activities (such as sensation, motor control and specific linguistic functions and… in normal and sick state, monitoring of therapeutic responses, neurolabeling, lie detection, etc.) in the first decades of fMRI’s entry into the field of neuroimaging, this method had a great impact on The method used to study brain function by neuroscience researchers. Today, some of these works have entered the clinical fields. It seems that this transition will take place more rapidly in the next decade. Undoubtedly, before clinical fMRI has its full potential. If it is known and used, many problems must be solved in order to be able to obtain accurate and reliable signs of electrical activity through it. However, the possibility of identifying and treating disease and its benefits have led to efforts to turn fMRI into a clinical tool. has been


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