The balanced steady state free precession (bSSFP) sequence is comprised of RF pulses with alternating positive and negative flip angles. It is a very efficient sequence, however, it is sensitive to off-resonance effects which is illustrated in the figure below. The different magnetization vectors have different resonance frequences and at a certain frequency the steady state condition yields a zero signal. This gives rise to so-called "banding artefacts".
The code for this figure is found here
- Bieri, Oliver, and Klaus Scheffler. "Fundamentals of balanced steady state free precession MRI." Journal of Magnetic Resonance Imaging 38.1 (2013): 2-11.