Maintaining the CPMG Conditions with Slice Accelerated Parallel Imaging in 2D Fast Spin Echo
Parallel imaging in the slice encoding direction is used with 3D pulse sequences to allow high acceleration while maintaining reasonable geometry factors via 2D acceleration. For T2-weighted imaging, 3D acquisition has relatively long scan time and consequently 2D pulse sequences are frequently favored. Slice direction acceleration can also be used with 2D pulse sequences such as Fast Spin Echo. With Fast Spin Echo, the CPMG conditions must be maintained by aligning the center of the cosine modulation with the time in the RF pulse where the transverse magnetization is effectively created (isodelay point), otherwise ghosting artifacts result.