On-coil multiple channel transmit system based on class-D amplification and pre-amplification with current amplitude...

Area of Science:

• Engineering
• Medical Imaging
• Electronics

Background:

• On-coil transmit arrays are crucial for advanced magnetic resonance imaging (MRI) applications.
• Existing transmit amplifiers face challenges in power efficiency, heat dissipation, and cost for array integration.

Purpose of the Study:

• To develop a high-efficiency transmit amplifier unit for on-coil transmit arrays.
• To meet requirements of high power capability, low power dissipation, scalability, and cost minimization.

Main Methods:

• The system integrates a current-mode class-D output stage and a voltage-mode class-D preamplification stage.
• A custom DC-DC converter with current feedback modulates radio frequency pulse amplitude.
• Performance was evaluated using benchtop measurements and MRI experiments at 1.5T.

Main Results:

• Direct control of the B1 field was achieved with reduced load sensitivity (<10% variation).
• Isolation above 20 dB was demonstrated between neighboring coils in an array configuration.
• High output current operation was validated through power measurements and flip angle quantification.

Conclusions:

• The developed transmit amplifier unit is suitable for on-coil transmit arrays in MRI.
• The design offers improved performance metrics including efficiency, B1 control, and coil isolation.
• Demonstrated single and multi-channel excitations confirm the hardware's practical utility.