A high duty-cycle, multi-channel, power amplifier for high-resolution radiofrequency encoded magnetic resonance imaging
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A radiofrequency (RF) power amplifier is an essential component of any magnetic resonance imaging (MRI) system. Unfortunately, no commercial amplifier exists to fulfill the needs of the transmit array spatial encoding (TRASE) MRI technique, requiring high duty cycle, high RF output power and independently controlled multi-channel capability. Thus, an RF amplifier for TRASE MRI is needed.
Materials and methods
A dual-channel RF power amplifier dedicated for TRASE at 0.22 T (9.27 MHz) was designed and constructed using commercially available components. The amplifier was tested on the bench and used a 0.22 T MRI system with a twisted solenoid and saddle RF coil combination capable of a single-axis TRASE.
The amplifier is capable of sequential, dual-channel operation up to 50% duty cycle, 1 kW peak output and highly stable 100 μs RF pulse trains. High spatial resolution one-dimensional TRASE was obtained with the power amplifier to demonstrate its capability.
The constructed amplifier is the first prototype that meets the requirements of TRASE rectifying limitations of duty cycle and timing presented by commercial RF amplifiers. The amplifier makes possible future high resolution in vivo TRASE MRI.
KeywordsMRI TRASE RF RF power amplifiers
An abstract for this work was accepted for poster presentation at the International Society for Magnetic Resonance in Medicine (ISMRM) 27th Annual Meeting and Exhibition in Montreal, Canada (2019). We thank Curtis Osinchuk and Lance Spiridon, Cross Cancer Institute, Edmonton, Alberta, Canada for constructing enclosure for the TRASE amplifier and Vyacheslav Volotovskyy and the Technology Management Group (TMG), Cross Cancer Institute, Edmonton, Alberta, Canada for technical support.
Design: ARP, TP, JCS and BT. Construction and bench performance testing: ARP, TP and BT. MRI testing and TRASE acquisition: ARP, HS and JCS. Manuscript drafting and revision: ARP, TP, JCS and BT. Critical revisions: ARP, JCS and BT.
This study was funded by the Natural Sciences and Engineering Research Council of Canada (N-SERC), Grant/Award number: RGPIN-03992.
Compliance with ethical standards
Conflict of interest
Aaron R. Purchase declares that he has no conflict of interest. Tadeusz Pałasz declares that he has no conflict of interest. Hongwei Sun declares that he has no conflict of interest. Jonathan C. Sharp declares that he has no conflict of interest. Boguslaw Tomanek declares that he has no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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