How do time-varying gradient fields produce clinical effects?

Time-varying gradient fields play a crucial role in Magnetic Resonance Imaging (MRI) by varying the magnetic field strength in a controlled manner during the imaging process. These changes in the magnetic field create spatial variations that are essential for encoding the positions of the signals generated from protons in the tissue. This encoding enables the reconstruction of images with high spatial resolution.

When gradients are applied, they affect the precession frequency of the hydrogen nuclei at different locations, allowing MRI to distinguish between various tissue types based on their characteristics. In this way, clinical effects are produced as the varying gradients can influence the signals received from different areas of the body, which is vital for producing detailed diagnostic images.

The other options do not accurately describe the mechanism through which time-varying gradient fields operate in the clinical setting. Static fields alone do not produce the necessary imaging effects, radiation does not result from the gradient fields themselves, and cooling does not pertain to the operation of gradient fields in MRI.