At 1.5 Tesla, what is the approximate difference in precessional frequency between fat and water?

The precessional frequency difference between fat and water at a magnetic field strength of 1.5 Tesla is approximately 224 Hz. This difference is a consequence of the distinct magnetic resonance characteristics of fat and water due to their differing chemical environments.

In magnetic resonance imaging (MRI), different types of tissues resonate at different frequencies because of their unique proton densities and the local magnetic environment established by the surrounding molecules. Specifically, fat protons precess at a slightly lower frequency than water protons. This frequency separation is a critical factor in MRI as it enables the differentiation of various tissues based on their signal characteristics.

At 1.5 Tesla, water has a precessional frequency of around 63.9 MHz, and fat, being influenced by its molecular structure, precesses at a frequency that is about 224 Hz lower. This 224 Hz difference allows imaging techniques to exploit the variations in signal when capturing images of tissues composed of varying ratios of fat and water, leading to clear delineation of structures in MRI scans.