Real-time specific absorption rate supervision for a 32-channel RF transmit system with virtual observation points

Area of Science:

• Medical Imaging
• Radiofrequency Engineering
• Computational Electromagnetics

Background:

• Real-time supervision is essential for parallel transmit (pTx) systems in MRI to ensure subject safety and optimize RF array performance.
• High channel counts in pTx systems significantly increase computational demands for specific absorption rate (SAR) calculations.
• Accurate local SAR supervision requires a high number of virtual observation points (VOPs), further intensifying computational load.

Purpose of the Study:

• To develop a real-time RF transmit supervision system for a 32-channel pTx MRI system.
• To implement local SAR calculation with a high number of VOPs for enhanced supervision accuracy.
• To ensure subject safety and maximize the utility of advanced RF arrays in MRI.

Main Methods:

• The system utilizes 64 digitizer channels to acquire real and imaginary parts of 32 transmit channels.
• Local SAR calculation is offloaded to a graphics processing unit (GPU) to manage computational intensity.
• The system operates independently, capable of shutting down RF power amplifiers if SAR limits are breached.

Main Results:

• The developed system can monitor 32 transmit channels and perform real-time SAR calculations using up to 165,000 VOPs.
• With fewer channels (16 or 8), the number of VOPs increases to 730,000 and 2,300,000, respectively, demonstrating scalability.
• The system successfully monitors relative phases of each RF channel in the pTx system.

Conclusions:

• A real-time RF supervision system for 32-channel pTx systems has been successfully developed.
• The system performs local SAR calculation based on VOPs derived from numerical simulations.
• This advancement supports safer and more effective utilization of high-channel-count RF arrays in MRI.