What is MRI? Magnetic Resonance Imaging (MRI) is a safe and non-invasive scanning procedure that is commonly used for medical and research purposes. The MRI scanner is like a very motion-sensitive camera that can take pictures of our body, including our brain! MRI is unlike other neuroimaging techniques, such as X-rays and CT scans, that use radiation to obtain images of our body parts. Rather, it utilises magnets and radio waves to produce detailed pictures of brain structures, body organs and more (Hirsch, 2022). MRI is now one of the more commonly used tools that help neuroscientists study brain structures and functions.

How does MRI produce scanned images of our brain? To produce a high resolution 3-Dimensional (3D) image of the brain, the MRI scanner first obtains brain images in slices. It works like a camera, but instead of taking 2-Dimensional (2D) photos in pixels, the MRI scanner creates a 3D view of the brain in voxels (a tiny cube with edges of 1-3mm). The more voxels obtained and the smaller the voxel size is, the clearer and more detailed the 3D image can be. As MRI is very sensitive to motion, participants going into the MRI scanner play an important role in staying as still as possible while the MRI obtains images of brain slices to form a high-quality image. These high-resolution 3D images shed light on several aspects of brain structures such as their sizes and shapes.

Figure 1 – The importance of pixels and voxels in formation of clear and detailed images. (A) For the same object, large and small numbers of pixels give rise to high-resolution (left) and low-resolution (right) images, respectively. (B) The voxel is used to form 3D images, while the pixel is used for 2D.

What about functional MRI (fMRI)? Neurons in different areas of the brain are activated when individuals engage in different tasks. For example, researchers can ask participants to read a text or watch a video while they undergo an fMRI scan. When neurons in certain brain areas are activated, they consume energy and induce an influx of blood flow that carries oxygen in the nearby blood vessels. An fMRI scan detects changes in the oxygen level of blood flow in different areas of the brain. It can be used to identify the areas that are more actively working, thus aiding researchers in studying brain functions.

How is MRI used? MRI scanners have a plethora of uses in scientific and medical fields. For instance, scientists can study how different brain structures change in size and shape as a person ages. Medical professionals can also check for abnormalities in a patient’s brain to aid the diagnosis and planning of surgeries. Furthermore, fMRI scans also allow scientists to measure brain activity and study their specialised functions. Figure 2 shows an fMRI scan of a person’s brain while he/she is doing a task in the MRI scanner – the activated areas (highlighted in red) can be identified and mapped. Thus, MRI is and continues to be a powerful and important tool in studying the structures and functions of a human brain.

Figure 2 – An example fMRI scan showing brain activity (Tian, 2010). Brain areas that are relatively more active (highlighted in the images) during a functional MRI scan will be identified due to its higher Blood Oxygenation Level Dependent (BOLD) signal detected by the MRI scanner.

References

Hirsch, L. H. (2022, February). Magnetic Resonance Imaging (MRI): Brain (for Parents) – Nemours KidsHealth. KidsHealth. https://kidshealth.org/en/parents/mri-brain.html

Hoyos, P. M. H., Kim, N. Y. K., & Kastner, S. K. (2019, June 28). How Is Magnetic Resonance Imaging Used to Learn About the Brain? Frontiers for Young Minds. https://kids.frontiersin.org/articles/10.3389/frym.2019.00086

Tian, T. S. (2010). Functional Data Analysis in Brain Imaging Studies. Frontiers in Psychology, 1. doi:10.3389/fpsyg.2010.00035

Drafted by Claire & Kah Xuan

Edited by Michelle, Phoebe & Joyce