What does Gx indicate in a pulse sequence diagram?

In a pulse sequence diagram, Gx represents the gradient primarily used for frequency encoding. This occurs during the readout phase of imaging when the magnetic field gradient is applied along the x-axis. Frequency encoding is essential in MRI because it correlates the position of signals detected from the spins within the imaged volume to their respective frequencies. The application of Gx allows for the spatial localization of the frequencies received from the signals, enabling the distinction of different locations along that axis.

For instance, when the Gx gradient is applied, spins in different locations along the x-axis resonate at different frequencies due to the variation in the magnetic field strength. This principle is foundational for constructing images where each point in the image corresponds to a specific frequency, allowing for accurate representation of the anatomical structures being imaged. Understanding how Gx functions is crucial for interpreting pulse sequences and the subsequent imaging results in MRI.