ECLIPSE utilizing gradient-modulated offset-independent adiabaticity (GOIA) pulses for highly selective human brain...

Area of Science:

• Magnetic Resonance Imaging
• Spectroscopy
• Biomedical Engineering

Background:

• Extracranial lipid suppression is crucial for proton MRSI (Magnetic Resonance Spectroscopic Imaging).
• Existing methods have limitations in lipid suppression levels, RF power deposition, and spatial selectivity.
• Elliptical localization with pulsed second order fields (ECLIPSE) offers good lipid suppression but is sensitive to chemical shift displacement (CSD) errors.

Purpose of the Study:

• To enhance the ECLIPSE technique for improved lipid suppression and reduced CSD errors in proton MRSI.
• To develop and validate a novel GOIA-ECLIPSE (Gradient Offset-Independent Adiabaticity-ECLIPSE) method.
• To assess the performance of GOIA-ECLIPSE for in vivo MRSI applications, particularly at high magnetic fields (≥3 T).

Main Methods:

• Implementation of GOIA-ECLIPSE using 15 kHz bandwidth gradient-modulated RF pulses.
• Development of two MRSI sequences: an adiabatic double spin-echo inner volume selection and an outer volume suppression FID-MRSI sequence.
• Evaluation of lipid suppression, CSD, transition width, and RF power deposition in vivo.

Main Results:

• GOIA-ECLIPSE achieved over 100-fold lipid suppression with less than 2.6 mm in-plane CSD.
• Demonstrated an approximately 5-fold improvement in spatial selectivity and reduced CSD compared to the parent method.
• Required only a 1.9-fold increase in RF power despite a 5-fold larger bandwidth, with artifact-free metabolite spectra.

Conclusions:

• GOIA-ECLIPSE offers robust lipid suppression, low CSD, and sharp ROI edge transitions, making it a superior alternative to existing methods.
• The technique is well-suited for high-field MRSI due to its low RF power deposition.
• This advancement improves the reliability and applicability of proton MRSI for in vivo metabolic profiling.