A multi spin echo pulse sequence with optimized excitation pulses and a 3D cone readout for hyperpolarized ¹³ C...

Area of Science:

• Magnetic Resonance Imaging
• Metabolic Imaging
• Medical Physics

Background:

• Hyperpolarized [1-¹³ C]pyruvate imaging is crucial for detecting diseases and monitoring treatment response.
• The limited lifetime of hyperpolarization restricts imaging time, posing a challenge for dynamic studies.

Purpose of the Study:

• To develop and validate a novel single-shot multi spin echo sequence for enhanced in vivo imaging of hyperpolarized [1-¹³ C]pyruvate.
• To overcome the limitations of transient hyperpolarization by improving readout time, spatial resolution, and signal-to-noise ratio.

Main Methods:

• A single-shot multi spin echo sequence utilizing numerically optimized spectrally selective excitation pulses and a 3D cone gradient readout trajectory.
• The sequence incorporates hyperbolic secant adiabatic refocusing pulses, designed for robustness against B₀ and B₁ field inhomogeneities.
• Gradient parameters were optimized for clinical translation, with maximal gradient amplitude of 4 G/cm and slew rate of 20 G/cm/ms.

Main Results:

• The developed pulse sequence achieved an isotropic point spread function (PSF) of 2.8 mm.
• A significant 46.10 ± 0.04% gain in image signal-to-noise ratio (SNR) was observed compared to conventional excitation pulses.
• Successful dynamic in vivo imaging of hyperpolarized [1-¹³ C]pyruvate and [1-¹³ C]lactate was demonstrated.

Conclusions:

• The novel pulse sequence enables dynamic in vivo imaging of hyperpolarized ¹³ C labeled metabolites with high spatial and temporal resolution.
• The sequence exhibits robustness against system imperfections, enhancing its clinical applicability.
• This technique holds promise for improved disease detection and treatment monitoring through advanced metabolic imaging.