Biology Forums - Study Force

Discuss the various types of neuroimaging, including the strengths and weaknesses of each.

•   Researchers developed imaging methods to meet clinical and research needs unmet by other techniques. Each imaging method offered some advantage over previous methods. As a group, these imaging methods enable us to peer inside the brain or body.
•   The CT scan is a three-dimensional reconstruction of many x-rays taken though a part of the body, such as the brain. It shows much more detail than an individual x-ray.
•   The MRI measures the release of energy from water in biological tissues following exposure to a uniform magnetic field. MRI images are superior to CT scans for detecting soft tissues, such as those in the brain. A brain tumor shows up particularly well on an MRI image because a tumor consists of soft tissue.
•   Positron emission tomography (PET) is a functional imaging technique, meaning that it measures changes in the brain’s activity levels. PET is an invasive tool that requires the injection of radioactive glucoselike molecules into the patient. Because PET is invasive, researchers later looked for functional imaging methods that wouldn’t require injections.
•   The fMRI measures the change in blood oxygen level and is an indirect correlate of neural activity. The fMRI relies on magnetic fields, as does MRI. Whereas MRI has a high resolution, fMRI operates at a low resolution so that researchers can snap many scans in rapid succession. Individual fMRI images aren’t very sharp, but the method shows changes in brain activity level over time because it creates a series of images.
•   Transcranial magnetic stimulation (TMS) uses strong and rapidly changing magnetic fields to induce electric fields in the brain. Depending on the level of stimulation, TMS can either enhance or interrupt brain function. Whereas TMS applies magnetic fields to the brain, magnetoencephalography (MEG) measures tiny magnetic fields, and in this way detects electrical activity in the brain and in the rest of the nervous system. MEG has good spatial resolution and better temporal resolution than PET and fMRI scans.