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Fast TR switches for ultra high field MRI
Short T2 MRI measurements opened up new possibilities in studying essential factors related to many neurodegenerative diseases. To perform such measurements cutting edge hardware is required that overcomes current limitations. One important device is the TR switch that shall be improved on in this work.
Magnetic resonance imaging (MRI) measurements typically are based on pulsed RF excitation of proton spins followed by encoded signal reception. For a particular set of experiments, the same RF antenna, typically referred to as MR coil, is used for excitation and reception. Such setup requires a transmit-receive (TR) switch, switching the antenna between the excitation path and the reception RF chain. Prevalent MRI TR switches do so with a switch time in the range of ten to hundreds of microseconds. While this is sufficient for regular MRI measurements for short T2 such long switch times are unacceptable. Myelin is involved in many neurodegenerative diseases and has signal fractions with decay time less than ten microseconds which would be entirely missed by long switching. To enable cutting edge short T2 measurement, switches with less than one microsecond switch time are required. The additional requirements make this a challenge: handling multiple kW of RF power during transmission, minimal insertion loss during the reception and switching transients that do not overload the sensitive RF receive chain.
Such switches have been developed and successfully tested for high field MRI (3T, 128MHz). In this work, one shall transfer such switch technology to 7T (298MHz). Further expansion on switch topology and implementation is warmly welcome. If one desires, this work is open for innovation or focuses more on technology transfer and external manufacturing.
Knowledge of RF circuitry, PCB design, and electronics prototyping is a strong plus for a potential applicant.
Magnetic resonance imaging (MRI) measurements typically are based on pulsed RF excitation of proton spins followed by encoded signal reception. For a particular set of experiments, the same RF antenna, typically referred to as MR coil, is used for excitation and reception. Such setup requires a transmit-receive (TR) switch, switching the antenna between the excitation path and the reception RF chain. Prevalent MRI TR switches do so with a switch time in the range of ten to hundreds of microseconds. While this is sufficient for regular MRI measurements for short T2 such long switch times are unacceptable. Myelin is involved in many neurodegenerative diseases and has signal fractions with decay time less than ten microseconds which would be entirely missed by long switching. To enable cutting edge short T2 measurement, switches with less than one microsecond switch time are required. The additional requirements make this a challenge: handling multiple kW of RF power during transmission, minimal insertion loss during the reception and switching transients that do not overload the sensitive RF receive chain. Such switches have been developed and successfully tested for high field MRI (3T, 128MHz). In this work, one shall transfer such switch technology to 7T (298MHz). Further expansion on switch topology and implementation is warmly welcome. If one desires, this work is open for innovation or focuses more on technology transfer and external manufacturing. Knowledge of RF circuitry, PCB design, and electronics prototyping is a strong plus for a potential applicant.
This work aims to develop new TR switches for the 7T ultra high field MRI system based on previous work done for 3T.
Such switches shall have cutting edge RF performance and be reliable enough to be deployed for regular use.
The design of the switches shall further be made ready for external fabrication (PCB and assembly) so that they can be fabricated on demand by established manufacturers.
This work aims to develop new TR switches for the 7T ultra high field MRI system based on previous work done for 3T. Such switches shall have cutting edge RF performance and be reliable enough to be deployed for regular use. The design of the switches shall further be made ready for external fabrication (PCB and assembly) so that they can be fabricated on demand by established manufacturers.
Christoph Schildknecht
schildknecht@biomed.ee.ethz.ch
+41 44 632 30 69
ETZ F88
Christoph Schildknecht schildknecht@biomed.ee.ethz.ch +41 44 632 30 69 ETZ F88