Flow compensation in non-balanced SSFP
نویسندگان
چکیده
Introduction. Non-balanced steady-state free precession sequences (SSFP-FID and SSFP-echo) are gradient-spoiled pulse sequences that provide high signal even in presence of long T1 values, because the transverse magnetization is not completely incoherent by means of radiofrequency spoiling. Contrary to balanced SSFP sequences they do not suffer from off-resonance banding artifacts, making them more suitable for clinical applications in some regions. However, these sequences are extremely sensitive to flow and motion, because of spoiler gradients that produce large first moments. The steady state is perturbed by moving isochromats and this phenomenon results in artifacts and signal loss, mostly noticeable in the presence of moving tissues with long T2, like the cerebro-spinal fluid around the brain. In this work, we present a theoretical explanation for this phenomenon by means of numerical simulation of the Bloch equations, and completely flow-compensated SSFP-FID and SSFP-echo implementations that eliminate this source of artifacts.
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