What are gradient coils responsible for in MRI imaging?

Gradient coils play a crucial role in MRI imaging by encoding spatial location and facilitating slice selection. These coils generate varying magnetic fields that change linearly with position, which allows for the manipulation of magnetic field gradients in different directions. This manipulation is essential for determining where within the body the MRI is acquiring data, as well as for selecting specific slices of tissue to be imaged.

When an MRI sequence is performed, the gradient coils are activated to create variations in the magnetic field strength that are spatially dependent. This spatial encoding allows the MRI system to differentiate signals coming from different locations within the imaged volume, effectively mapping the anatomy of the body in three-dimensional space. Additionally, during slice selection, the gradients help to ensure that only the desired slice of tissue is excited and imaged while other slices are effectively ignored.

This contrast with the other potential functions of the coils. For example, although enhancing image clarity might be an overall goal of the MRI process, it is not the direct responsibility of the gradient coils. Filtering noise from the signal, while important in MRI, is primarily achieved through different processing techniques rather than the function of gradient coils. Adjusting the magnetic field strength is managed by the main magnetic field and the shim coils, not primarily by the gradient