Understanding the MRI: What Does It Measure and is it Reliable?
Magnetic resonance imaging (MRI) is a key tool for understanding neurological functions, from diagnosing patients with traumatic brain injury (TBI) to investigating the role of speech and language in the brain. The functional MRI (fMRI), which measures brain activity by detecting changes in blood flow, is now widely used to study linguistic processes in particular. Because these complex technologies have developed rapidly over the last two decades, clinicians and consumers alike should be familiar with MRI methodology in order to make informed medical decisions.
On a basic level, an MRI functions by sending pulses of energy into a magnetic field and then measuring the brain’s responses to that energy. As the brain’s molecules recover from an electrical pulse, they send out energy of their own, which are measured as signals and compiled to create a two-dimensional scan of the brain’s structure. The fMRI, on the other hand, is used to measure the brain’s response to a specific stimulus, which aids in the study of speech and language. The fMRI measures blood flow to determine which areas of the brain become active in response to a given type of stimulus, representing this activity as areas of “light” or color on an image of the brain.
The reliability of MRI results can be improved if researchers recognize the limitations of this intricate technology. Clinicians first must be aware of hardware constraints and hitches, particularly when accounting for discrepancies in magnetic strength across trials. Beyond the more technical aspects of operating an MRI machine, researchers should design their experiments to simplify the MRI process. For example, researchers should account for MRI-specific concerns when they design task structure and difficulty, the presentation method of a given stimulus, and participant needs. They should understand how to reduce technological errors (such as signal loss or movement-related noise) that can confound MRI data. Finally, clinicians should be aware of methods for MRI data retrieval and analysis, which can require more complex treatment than some other experimental data.
Overall, neuroimaging is a powerful new tool for revealing the inner structure and function of the brain, particularly as it relates to language processes and injury. To ensure the integrity of MRI research, clinicians should be fully aware of the limitations and necessities of MRI use, from experimental design to data analysis.
Source: Chouinard B, Boliek C, & Cummine J. How to interpret and critique neuroimaging research: A tutorial on use of functional magnetic resonance imaging in clinical populations. American Journal of Speech-Language Pathology. (August 2016).