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Pulsation artifact in short TR MR imaging and angiography: exacerbation with signal averaging
D G Mitchell1, T Tasciyan, H V Ortega
1Department of Radiology, Thomas Jefferson University Hospital and Jefferson Medical College, Philadelphia, PA 19107.
Abstract:
Averaging the signals from more than one excitation per phase-encoding view increases the signal-to-noise ratio and, in conventional spin-echo magnetic resonance imaging, reduces most motion artifacts. To determine the effects of signal averaging on two-dimensional gradient-echo images, acquisitions with different TRs and with no averaging versus multiple-signal averaging were compared in a pulsatile flow phantom and the human abdominal aorta. Intraview (each view repeated before changing the phase-encoding value) and interview (obtaining all views sequentially and then repeating the entire set) averaging methods were used. Pulsation artifacts were present on all images of the flow phantom and the aorta. Intraview signal averaging, the method most commonly used, exacerbated rather than ameliorated pulsation artifacts with short TR sequences. Pulsation artifacts on two-dimensional images obtained with a short TR can be minimized by completing the acquisition as rapidly as possible, avoiding signal averaging. If signal averaging is used for short TR images, it should be interview averaging.
Insights
Signal averaging in magnetic resonance imaging (MRI) can worsen pulsation artifacts on fast, two-dimensional gradient-echo sequences. For short repetition time (TR) imaging, avoid signal averaging or use interview averaging to minimize artifacts.
Area of Science:
- Medical Imaging
- Biophysics
Background:
- Signal averaging in magnetic resonance imaging (MRI) typically enhances signal-to-noise ratio and reduces motion artifacts.
- Conventional spin-echo sequences benefit from signal averaging.
- The impact of signal averaging on gradient-echo sequences, particularly concerning motion artifacts, requires specific investigation.
Purpose of the Study:
- To evaluate the effect of signal averaging on two-dimensional gradient-echo MRI images.
- To compare intra-view and interview averaging methods in the presence of pulsatile flow.
- To determine optimal strategies for minimizing pulsation artifacts in gradient-echo imaging.
Main Methods:
- Acquisitions were performed using varying repetition times (TR) and with/without signal averaging.
- A pulsatile flow phantom and the human abdominal aorta were imaged.
- Intra-view and interview averaging techniques were applied and compared.
Main Results:
- Pulsation artifacts were observed in all tested conditions, including the flow phantom and aorta.
- Intra-view signal averaging, a common technique, intensified pulsation artifacts in short TR sequences.
- Rapid acquisition without signal averaging was most effective in minimizing artifacts for short TR images.
Conclusions:
- Signal averaging does not universally reduce artifacts in MRI; its effect is sequence-dependent.
- For two-dimensional gradient-echo sequences with short TR, intra-view averaging can worsen pulsation artifacts.
- Minimizing acquisition time or employing interview averaging are recommended strategies to mitigate artifacts in such scenarios.