In a gradient-echo sequence, which element is not typically used?

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Multiple Choice

In a gradient-echo sequence, which element is not typically used?

Gradient-echo imaging relies on a single RF excitation pulse and uses magnetic field gradients to rephase transverse magnetization, rather than a 180-degree RF pulse. After excitation, the dephasing of spins is counteracted by switching the gradients, which creates an echo at the echo time. The readout gradient collects signal during the readout period, and the phase-encoding gradient provides spatial encoding in the other axis. Because there is no 180-degree refocusing pulse, this sequence behaves differently from a spin-echo sequence and tends to be more sensitive to magnetic field inhomogeneities. Therefore, the element not typically used is the 180-degree refocusing pulse.

Gradient-echo imaging relies on a single RF excitation pulse and uses magnetic field gradients to rephase transverse magnetization, rather than a 180-degree RF pulse. After excitation, the dephasing of spins is counteracted by switching the gradients, which creates an echo at the echo time. The readout gradient collects signal during the readout period, and the phase-encoding gradient provides spatial encoding in the other axis. Because there is no 180-degree refocusing pulse, this sequence behaves differently from a spin-echo sequence and tends to be more sensitive to magnetic field inhomogeneities. Therefore, the element not typically used is the 180-degree refocusing pulse.

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