Fast water concentration mapping to normalize (1)H MR spectroscopic imaging.

Area of Science:

• Medical Imaging
• Biophysics
• Quantitative MRI

Background:

• Magnetic Resonance Spectroscopic Imaging (MRSI) provides crucial metabolic information.
• Standardization of MRSI data is essential for accurate inter-subject and longitudinal analysis.
• Quantitative proton density (ρ) mapping is vital for normalizing metabolic data.

Purpose of the Study:

• To develop a rapid and robust pipeline for acquiring and processing proton density (ρ) maps.
• To enable time-compatible clinical explorations for MRSI data normalization.
• To facilitate inter-subject comparisons and longitudinal follow-up of MRSI data.

Main Methods:

• Utilized a multi-echo T2(*) mapping sequence, XEP for B1(+) mapping, and optimized variable flip angle for T1 mapping.
• Determined correction factors for quantitative water proton density (ρ) maps at 3 Tesla.
• Acquired normalized metabolite maps from a phantom and nine healthy volunteers, including one glioma patient.

Main Results:

• Generated accurate ρ maps for both phantom and volunteer datasets.
• Metabolic concentrations on the phantom showed <7% deviation from theory after normalization.
• Normalized metabolic values in a glioma patient revealed abnormalities in N-acetyl aspartate, choline, and creatine levels.

Conclusions:

• The proposed MRSI pipeline robustly generates ρ maps suitable for normalizing metabolic maps.
• This technique supports clinical MRSI studies by enabling reliable data comparison.
• The method demonstrates potential for direct clinical application in analyzing metabolic abnormalities.