What are the three main functions of MRI gradients?

The three main functions of MRI gradients are slice excitation, phase encoding, and frequency encoding.

Slice excitation refers to the ability of gradients to define the specific area of the body that will be imaged. By applying a gradient in the direction of the slice, only a particular 'slice' of tissue is excited, allowing for thin layers to be imaged separately, which is essential for producing detailed images.

Phase encoding is utilized to distinguish between locations in the direction of that particular gradient. By varying the phase of the signal based on gradient strength, it allows for spatial localization of the signals received from different areas in the slice. This technique is crucial for forming the final image because it helps differentiate signals that arise from various positions within the imaged slice.

Frequency encoding works by altering the frequency of the magnetic resonance signals in relation to the gradient applied. This allows for spatial localization in the direction perpendicular to the phase-encoding direction. In practice, frequency encoding contributes to the ability to create images with high spatial resolution by resolving signals from various spatial locations based on their frequency differences.

The other combinations presented in the choices either incorporate incorrect terms or omit crucial aspects of the MRI gradient functions, which diminishes their accuracy in describing the core roles played by gradients in MRI