Patients, whose doctor orders them a functional magnetic resonance imaging (fMRI) study, may wonder what the difference is between a functional MRI and a conventional MRI or what it is used for. A conventional MRI uses a super-conducting magnet to control the magnetic field within and around the scanner. This is done with the use of pulse sequences, sequences which are designed specifically for MRI scans. Conventional MRI scans require a patient to lie still while they are being scanned. fMRI elevates this conventional scan a step further.1
What is fMRI?
The patient is still scanned in the same or similar MRI scanner that controls the magnetic field around them.1 The pulse sequences still happen, but may be different, and the patient still has to lie still. However, fMRI may show the areas of the brain that are activated while the patient is thinking of something. This is done by measuring the changes in blood flow at these times.1,2
In many cases, fMRI provides detailed information about the brain. It can show gray and white matter structures, as well as blood flow, which may aid physicians in long-term studies of changes. There are a number of things that can affect this information that are out of the control of the creators of the machine or of the radiographers. One variable that has the possibility of control: the noise of the scan.2 Noise during an MR scan can be caused by the vibration of the metallic coils inside the scanner and the objects placed near the patient's body, which are also called coils. The magnetic field causes this vibration as it is changed during the pulse sequences.
What are the trends?
fMRI may be used to research different diseases, such as Alzheimer's disease or dementia. In these cases, the evaluation of white matter in the brain is important, because the white matter may show deterioration associated with the disease. In other research studies, fMRI may be used to monitor what areas of the brain are activated by different tasks or thoughts. This may be difficult, however, if there are factors that can interfere with the patient's concentration or brain activity.
Doctor Peder Larson, an Associate Professor and a Principal Investigator in the Department of Radiology and Biomedical Imaging at the University of California in San Francisco, believes that the noise during the scan may have a biological effect on brain function as it is perceived by the patient.2 His team and the manufacturer of their scanners have been working together to develop a quieter fMRI sequence. This sequence may reduce the noise during the scan significantly. This sequence is still being researched.
Dr. Larson believes that the quieter scan has the potential to minimize the effects of the auditory stimulation.2 This could lead to better imaging of conditions that may produce their own stimuli, such as auditory hallucinations in schizophrenia or tinnitus. With this technology, physicians may learn more about certain diseases from fMRI, which may not have been possible with a traditional magnetic resonance imaging study.
For more information, please read SIGNA Pulse "The sound of silence."
1. Stephanie Watson. "What Are the Advantages and Disadvantages of fMRI?" howstuffworks.com. Web. 10 May 2019. <https://science.howstuffworks.com/fmri4.htm>.
2. Peder Larson. "The sound of silence." SIGNA Pulse. Autumn 2018. Web. 10 May 2019. <http://www.gesignapulse.com/signapulse/autumn_2018/MobilePagedArticle.action?articleId=1444529#articleId1444529>.