BLADE/ PROPELLER Artifacts
The BLADE/ PROPELLER acquisition pattern, which involves acquiring data in a rotating blade-like pattern, can introduce aliasing artifacts under certain circumstances. The most common cause of aliasing artifacts in BLADE/ PROPELLER imaging is insufficient coverage of k-space, which can occur due to factors such as:
Inadequate FOV: If the field of view (FOV) is not properly planned or set too small, it may not fully encompass the anatomy of interest. This can lead to aliasing artifacts as the information beyond the FOV is folded back into the image.
Motion-induced aliasing: If there is significant motion during the acquisition, such as patient movement or pulsatile flow, the motion-related signal can cause aliasing artifacts due to undersampling or mismatches between consecutive blades.
Incomplete blade coverage: If the blades do not fully cover the desired field of view (FOV), areas outside the blade coverage may exhibit artifacts or reduced image quality.
Absence of phase oversampling: The absence of phase oversampling means that not enough data points are acquired in the phase-encoding direction. As a result, high-frequency information in the image may exceed the Nyquist limit and fold back into the image as low-frequency information, leading to streak-like patterns or distortion.
BLADE Artifact in Brain MRI
BLADE Artifact in spine MRI
To reduce or eliminate aliasing artifacts in BLADE/PROPELLER imaging, the following strategies can be employed:
Increase FOV: Ensuring that the FOV is adequately sized to encompass the entire region of interest, accounting for potential motion or pulsatile flow, can help reduce aliasing artifacts
Increase phase oversampling: By acquiring additional data points in the phase-encoding direction, more high-frequency information can be captured, reducing the likelihood of aliasing artifacts
Adjust blade parameters: Optimizing the blade parameters, including the number of blades, rotation angle, or blade width, can affect the amount of k-space coverage and help mitigate aliasing artifacts. Increasing the number of blades or adjusting the blade overlap can improve spatial sampling and reduce aliasing effects.
Blade coverage 83%
Blade coverage 150%
Place saturation bands outside FOV in the phase-encoding (PE) direction: Saturation bands are radiofrequency pulses applied to selectively saturate the signal from tissues outside the region of interest. By placing saturation bands outside the FOV in the PE direction, you can effectively suppress the signal from those regions, reducing the likelihood of wrap-around artifacts.
Use of saturation bands: By applying saturation bands strategically, specifically targeting the areas where the artifact is likely to occur, the signal contribution from those regions can be reduced or eliminated. This can effectively mitigate the appearance of the BLADE/propeller artifact.
- Kojima, S., Morita, S., Ueno, E., Hirata, M., Shinohara, H., & Komori, A. (Year). Aliasing Artifacts With the BLADE Technique: Causes and Effective Suppression. Journal of Magnetic Resonance Imaging.