Cine Imaging in Cardiac MRI: SSFP Principles and Management of Banding Artifacts Part1
Cardiac MRI is a relatively complex examination, and in clinical practice we often encounter various challenges. Today, starting with cine imaging, we will provide a systematic introduction—from imaging principles to sequence optimization strategies.
First, cine imaging has two key aspects: "bright blood" and "cine." What we aim to image determines the techniques we choose. We use the steady-state free precession (SSFP) sequence (e.g., FIESTA) to achieve bright blood, and we use retrospective ECG gating or peripheral pulse gating to achieve the cine effect. As the saying goes, every choice has trade‑offs. The chosen techniques also lead to the two major drawbacks of cine imaging: SSFP sequences are prone to banding artifacts , and retrospective gating is intolerant to arrhythmias. Today is the first part of our discussion on cine imaging, focusing on the SSFP sequence and solutions for banding artifacts.
Most of you are already familiar with steady-state sequences, but let us briefly review their imaging principles:
At its core, the steady-state sequence is still a gradient-recalled echo (GRE) sequence, with the spoiled GRE sequence being its counterpart. The spoiled GRE sequence primarily acquires the free induction decay (FID) signal after a single RF excitation, avoiding interference from stimulated echoes. As shown in the figure below, after multiple RF pulses, a stimulated echo signal forms just before the next RF excitation.
However, the spoiled GRE sequence does not want this stimulated echo component, so it uses a series of spoiling measures (long TR, gradient spoiling, RF spoiling) to eliminate this signal, as shown below. Some may ask: why eliminate this signal? Because in most cases, when using spoiled GRE, we want T1-weighted images, while the stimulated echo has a complex composition containing a significant T2 component—clearly not what we want. Therefore, spoiled GRE sequences always remove this signal.
https://i.redd.it/lbkhp314catg1.gif
The steady-state sequence differs from the spoiled GRE sequence in that it preserves the stimulated echo and shortens the TR so that the FID and stimulated echo merge. As shown below, the steady-state sequence uses a shorter TR, allowing the FID and stimulated echo signals to overlap. The gradient application is more symmetric, maximizing the retention of both FID and stimulated echo signals.
A shorter TR reduces scan time, enabling higher temporal resolution for cardiac cine imaging. The superposition of FID and stimulated echo makes the signal more complex, approaching a T2/T1 contrast, which gives the steady-state sequence its characteristic bright water, bright blood, and bright fat—laying the foundation for bright-blood imaging.
Although the principle of steady-state sequences was proposed long ago, their demanding requirements for magnetic field homogeneity and gradient performance meant that it took a considerable time before they were widely used in clinical imaging. Even today, we frequently encounter the classic banding artifact of SSFP sequences. Next, let us discuss how to address banding artifacts when they occur:
- End-expiratory breath-holding – This is very important. The method is simple but often overlooked. At the end of expiration, most of the air in the lungs is expelled, making the magnetic field around the heart much more uniform. How to achieve this? Practice. I believe you all understand the importance of pre-examination preparation. Another tip: For patients who cannot exhale properly once in the scanner, do not hesitate—turn off the automated voice instructions, give manual commands, and wait until the patient has fully exhaled before asking them to hold their breath. After a few repetitions, they will be able to follow the automated instructions for end-expiratory breath-holding.
- Parameter optimization – I am sure many of you are looking forward to this. For modern scanners, the most important factor in reducing banding artifacts in bright-blood cine imaging is: shorten the TR as much as possible. Some may say that having TR equal to twice TE is also important. This is not entirely wrong, but there are two issues: First, TR cannot be exactly twice TE. It may appear equal in the parameter interface, but for the scanner, both TR and TE need to be precise to many decimal places—what we think is equal may be far from equal for the scanner. Second, we have partial echo techniques that can significantly reduce TR. That is, for each echo, we do not acquire an entire k-space line, but just over half of it, thereby saving sampling time and reducing TR. For these reasons, we aim for the shortest possible TR rather than strictly making TR equal to twice TE. How can we achieve the shortest TR through parameter adjustments? There are only a few parameters that affect TR in steady-state sequences. To shorten TR, we can reduce the flip angle, lower the frequency encoding matrix, or increase the bandwidth. You will notice this is a trade-off: a larger flip angle improves myocardial-to-blood pool contrast; a larger matrix gives higher resolution; a lower bandwidth provides higher SNR. In summary, to meet diagnostic requirements: use the smallest flip angle that still provides acceptable contrast (typically 40°–75°); use the smallest matrix that achieves sufficient resolution (in-plane voxel size >2.0 mm is not recommended); and adjust the bandwidth to the shortest TR while maintaining acceptable SNR (generally, higher bandwidth shortens TE, but too high a bandwidth increases gradient ramp-up time and may paradoxically lengthen TE).
- Adjusting the center frequency – I believe many of you know and have used this method. However, some may complain that without a "Frequency Scout" it is impossible to adjust. That is not true. In fact, we can see that whether we need to increase or decrease the frequency is related to where the artifact appears. The most common problem is a black band at the posterior wall of the left ventricle on the short‑axis view. In this case, we decrease the center frequency. If the black band does not completely cover the entire wall, we only need to decrease the frequency by 30 Hz. If it completely covers the wall, we decrease by 60 Hz. The larger the band, the more we need to decrease.
The following figure illustrates this well: In the 0 Hz image, there is a black band at the posterior wall of the left ventricle. As we decrease the frequency, at –75 Hz the artifact almost disappears. Looking at the 150 Hz image, there is a clear black band at the lateral wall of the left ventricle; as we increase the frequency, at 75 Hz the black band at the same location is gone. In summary: if a black band appears at the posterior wall of the left ventricle, we need to decrease the frequency; if it appears at the lateral wall, we need to increase the frequency. The amount of increase or decrease is determined by the size of the black band.
Regarding how to adjust the center frequency, you can use the Manual Prescan function.
Center frequency can be adjusted using the manual prescan function. In general, the direction of adjustment depends on the location of the black band: a band at the posterior wall of the left ventricle calls for a decrease in center frequency, whereas a band at the lateral wall calls for an increase. The magnitude of adjustment is determined by the size of the band. Once the adjustment is made, calibration may be performed as needed, after which imaging can proceed normally.
This concludes today's content. Feel free to discuss any questions. Thank you all!
Attribution & Acknowledgment:
The images used in this article are sourced from https://www.mriquestions.com, an outstanding educational resource. I have personally relied on this website since my student days to deepen my understanding of MRI, and I remain deeply grateful for its clarity and insight. My sincere thanks to the creator of MRI Questions and Answer for making complex MRI concepts so accessible to learners and practitioners around the world.
Figures adapted from: https://www.mriquestions.com
Atalar E, McVeigh ER. Minimization of dead-periods in MRI pulse sequences for imaging oblique planes. Magn Reson Med. 1994;32(6):773-777. doi:10.1002/mrm.1910320613
Rajiah PS, Sundaram B, Ng MY, Ranganath P, Araoz PA, Bolen MA. Artifacts at Cardiac MRI: Imaging Appearances and Solutions. Radiographics. 2025;45(1):e230200. doi:10.1148/rg.230200
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