Design and realization of a multi-coil array for B₀ field control in a compact 1.5T head-only MRI scanner

Area of Science:

• Magnetic Resonance Imaging (MRI)
• Hardware Engineering
• Medical Physics

Background:

• Developing advanced hardware is crucial for enhancing MRI capabilities.
• Head-only MRI scanners present unique design constraints.
• Precise B0 field control is essential for high-quality MR imaging and advanced techniques like shimming.

Purpose of the Study:

• To design and implement a 31-channel multi-coil (MC) array for B0 field generation.
• To enable simultaneous advanced shimming in a novel 1.5T head-only MRI scanner.
• To optimize image encoding and shimming for improved MRI performance.

Main Methods:

• Designed a 31-channel MC array considering the constraints of a short, vertically oriented magnet with a viewing window.
• Utilized simulations to optimize MC hardware, B0 field generation, and thermal behavior prior to construction.
• Validated B0 field generation and imaging performance on a 4T MR scanner by comparing experimental data with system linear gradients.

Main Results:

• The MC system generates linear gradients up to 10 kHz/cm (23.5 mT/m) with 5 A/channel.
• Water-cooled system supports up to 74% duty cycle and 500 μs ramp times.
• MR imaging experiments demonstrated largely artifact-free results, with predictable and correctable residual imperfections.

Conclusions:

• The compact MC array achieves image encoding field quality comparable to clinical systems at high duty cycles.
• The system enables high-order B0 shimming capabilities.
• The potential for nonlinear encoding fields offers future advancements in MRI techniques.