A comparison of selective saturation and selective echo chemical shift imaging techniques

Area of Science:

• Medical Imaging
• Magnetic Resonance Imaging

Background:

• Chemical shift imaging enables selective visualization of fat and water within biological tissues.
• Accurate B0 field homogeneity is crucial for resolving distinct spectral lines of methylene (fat) and water.
• Both CHESS and SECSI techniques rely on precise B1 radiofrequency field calibration and homogeneity.

Purpose of the Study:

• To comparatively evaluate two chemical shift imaging methods: CHESS and SECSI.
• To analyze the B1 field error sensitivity of each method for spectral line suppression.
• To determine the optimal method for in vivo fat and water selective imaging.

Main Methods:

• CHESS (Chemical Shift Selective) imaging utilizes a selective pulse to saturate the unwanted spectral line.
• SECSI (Simultaneous）.achieved by incorporating a soft 180-degree radiofrequency pulse within a spin echo sequence.
• Theoretical analysis of B1 error impact on spectral line suppression, followed by phantom and in vivo experiments.

Main Results:

• Theoretical analysis indicated B1 errors affect CHESS linearly and SECSI quadratically.
• Phantom experiments confirmed SECSI's non-linear behavior and superior water suppression.
• In vivo experiments with a rabbit model showed SECSI yielding better results than CHESS.

Conclusions:

• SECSI offers more robust spectral line suppression against B1 field inhomogeneities compared to CHESS.
• The combination of CHESS and SECSI techniques provides the best performance for selective fat and water imaging.
• SECSI is a promising method for in vivo chemical shift imaging applications.