Mechanisms of Gradients - Video Lesson

Hey everybody. Welcome to today's lesson on spatial encoding. This lesson focuses on gradients and how they alter the main magnetic field in order to allow the MRI system to locate individual signals. Without the use of gradients, we would not be able to locate the signal within the body, so it is important that you understand these concepts. Spatial encoding is how the MRI scanner knows where in the body a particular signal is coming from. When creating an MRI image, the MRI scanner has to calculate the intensity of the signal coming from each three-dimensional location or voxel in the patient. However, when only the main magnetic field b sub zero is present, all of the hydrogen nuclei precess at the same frequency, which means the MRI system cannot differentiate between signal coming from the brain and signal coming from the abdomen.