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Comparison of respiratory triggering and gating techniques for the removal of respiratory artifacts in MR imaging
Abstract:
Respiratory movement degrades magnetic resonance (MR) images of the chest and abdomen by increasing noise through the production of "ghost" artifacts and by decreasing edge sharpness in moving structures. Respiratory gating, which limits data acquisition to end-expiration, is successful in restoring edge sharpness and reducing ghosts but increases imaging time two to three times, which limits its use to sequences with short repetition times (TRs). To overcome this limitation, an alternative technique, respiratory triggering, was developed, which triggers the acquisition of an MR section at a fixed point on the respiratory cycle. This technique restores edge sharpness and reduces ghosts, but unlike gating, it can be used to produce an image at any phase of the respiratory cycle. Triggering requires long TRs since the TR is limited to the respiratory period (TP) or one-half of TP, depending on whether the same section is triggered once or twice during a single respiratory cycle. Gating and triggering were evaluated and compared for single-section and multi-section imaging of both volunteers and patients. The authors conclude that when a chest or abdominal survey is required, triggering takes less time than gating if TRs are required that exceed one-fifth of TP.
Insights
Respiratory triggering improves magnetic resonance (MR) imaging quality by reducing artifacts and enhancing sharpness. This technique offers a faster alternative to respiratory gating for chest and abdominal imaging surveys.
Area of Science:
- Medical Imaging
- Radiology
- Biomedical Engineering
Background:
- Respiratory motion significantly degrades the quality of magnetic resonance (MR) images of the chest and abdomen.
- This degradation manifests as increased noise, "ghost" artifacts, and decreased edge sharpness in moving structures.
- Existing respiratory gating techniques, while effective, substantially increase imaging time, limiting their application.
Purpose of the Study:
- To evaluate and compare respiratory triggering and respiratory gating techniques for MR imaging.
- To assess the effectiveness of these techniques in improving image quality and reducing scan time.
- To determine the optimal technique for chest and abdominal imaging surveys.
Main Methods:
- Comparison of respiratory gating and respiratory triggering in single-section and multi-section MR imaging.
- Evaluation of image quality parameters including edge sharpness and artifact reduction.
- Assessment of imaging time efficiency for both techniques across various repetition times (TRs) relative to the respiratory period (TP).
Main Results:
- Both respiratory gating and triggering successfully restore edge sharpness and reduce ghost artifacts.
- Respiratory triggering allows image acquisition at any phase of the respiratory cycle, unlike gating which is limited to end-expiration.
- Triggering is more time-efficient than gating for chest and abdominal surveys when TRs exceeding one-fifth of the TP are required.
Conclusions:
- Respiratory triggering is a valuable alternative to gating, offering improved image quality with potentially reduced scan times.
- The choice between gating and triggering depends on the specific imaging requirements, particularly the necessary repetition times.
- Respiratory triggering provides greater flexibility in image acquisition timing compared to gating.