Composite slice-selective adiabatic excitation for prostate MRSI

Area of Science:

• Magnetic Resonance Imaging
• Spectroscopic Imaging
• Prostate Cancer Diagnostics

Background:

• Higher magnetic field strengths (7 T) enhance MRSI spectral resolution and signal-to-noise ratio.
• RF field nonuniformities at 7 T, exacerbated by surface coils, challenge accurate MRSI.
• Conventional adiabatic MRS sequences like LASER have long echo times (TEs), limiting prostate citrate measurement.

Purpose of the Study:

• To develop adiabatic MRSI sequences with shorter TEs for improved prostate imaging at 7 T.
• To maintain adiabatic spin excitation while reducing TEs compared to conventional methods.
• To address RF field nonuniformities and chemical shift artifacts in high-field MRSI.

Main Methods:

• Proposal of adiabatic semi-LASER (sLASER) sequences: composite adiabatic slice-selective (cLASER) and non-slice-selective (nsLASER).
• Evaluation of sequence performance using phantom and in vivo prostate imaging.
• Utilizing transceiver technology at high magnetic field strengths.

Main Results:

• Adiabatic sLASER sequences (cLASER, nsLASER) achieve shorter TEs while preserving adiabatic excitation.
• High slice excitation bandwidth in cLASER minimizes chemical shift displacement artifacts.
• Both cLASER and nsLASER demonstrated suitability for prostate MRSI at 7 T.

Conclusions:

• Adiabatic cLASER and nsLASER sequences are effective for high-field MRSI of the prostate.
• These sequences overcome limitations of conventional methods, enabling more accurate measurements.
• The developed sequences show promise for advanced prostate cancer diagnostics using 7 T MRSI.