High peak and high average radiofrequency power transmit/receive switch for thermal magnetic resonance

Ji, Yiyi; Hoffmann, Werner; Pham, Michal; Dunn, Alexander E.; Han, Haopeng; Özerdem, Celal; Waiczies, Helmar; Rohloff, Michael; Endemann, Beate; Boyer, Cyrille; Lim, May; Niendorf, Thoralf; Winter, Lukas

doi:10.1002/mrm.27194

Cited by 10 publications

(7 citation statements)

References 27 publications

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“…This level of insertion loss was considered acceptable in our prototype design, but the phase shifter insertion loss could be improved by using a more compact circuit design with less parasitic effects. Alternate designs for the T/R switch have shown about 0.2 dB lower insertion loss 37 …”

Section: Resultsmentioning

confidence: 99%

A retrofit to enable dynamic steering for transmit arrays without multiple amplifiers

Sun

Patel

Wilcox

et al. 2020

Magnetic Resonance in Med

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Purpose B1+ shimming is an important method for mitigating B1 inhomogeneity in high‐field MRI. Using independent power amplifiers for each transmit (Tx) element is the preferred method for B1 shimming but comes with a high cost. Conversely, the simplest approach to control a Tx array is by using coaxial cables of varying length in the Tx chain, but this approach is cumbersome and impractical for dynamic shimming. In this article, a system is described that enables dynamic, phase‐only, eight‐channel B1+ steering on a 7T MR scanner with only two power amplifiers. Methods Power dividers were utilized to first split the existing two‐channel Tx signal into eight channels. Digitally controlled phase shifters on each channel were designed to provide independent phase shifts with a resolution of 22.5° (from 0°, 22.5° … 337.5°). To validate the system, an eight‐channel body dipole array was simulated and constructed for bench and 7T imaging and evaluation. Results The phase conjugate B1+ steering method was employed at three different spatial positions in simulation, bench measurements, and scanner measurements—all with matching results. At the desired points, regions with homogenous B1+ were generated, indicating good Tx steering to the selected region. Conclusion The described system can be used as a simple retrofit to existing hardware to provide phase control while avoiding the need to manually switch cables and without requiring independent power amplifiers for each channel, thus demonstrating the ability to perform dynamic B1+ shimming with increased degrees of freedom but without significantly increased hardware cost.

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Section: Resultsmentioning

confidence: 99%

A retrofit to enable dynamic steering for transmit arrays without multiple amplifiers

Sun

Patel

Wilcox

et al. 2020

Magnetic Resonance in Med

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“…The experimental setup for RF heating in an MR system included (i) three Vivaspin filters with 400 μL of the nanogel–(BSA-FITC) solution, (ii) the agarose gel phantom, (iii) the water box connected to a water bath to keep the background temperature at 37 °C, (iv) a bow tie dipole RF antenna for imaging and RF energy delivery, (v) a customized high-power transmit/receive (Tx/Rx) switch [ 65 ] to support high-power RF pulses, and (vi) fiber optic temperature sensors (Omniflex, Neoptix, Quebec, Canada) used as an external temperature reference.…”

Section: Methodsmentioning

confidence: 99%

“…The bow tie dipole RF antenna was placed on the lid of the water box centered to the middle sample holder of the phantom ( Figure 7 ). The bow tie dipole RF antenna was tuned and matched to the B 0 field frequency of the MRI scanner (f = 297.2 MHz) and connected over a high-power Tx/Rx switch [ 65 ] to the RF transmission and RF signal reception chain of the MR system.…”

Section: Methodsmentioning

confidence: 99%

Controlled Release of Therapeutics from Thermoresponsive Nanogels: A Thermal Magnetic Resonance Feasibility Study

Winter

Navarro

et al. 2020

Cancers

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Thermal magnetic resonance (ThermalMR) accommodates radio frequency (RF)-induced temperature modulation, thermometry, anatomic and functional imaging, and (nano)molecular probing in an integrated RF applicator. This study examines the feasibility of ThermalMR for the controlled release of a model therapeutics from thermoresponsive nanogels using a 7.0-tesla whole-body MR scanner en route to local drug-delivery-based anticancer treatments. The capacity of ThermalMR is demonstrated in a model system involving the release of fluorescein-labeled bovine serum albumin (BSA-FITC, a model therapeutic) from nanometer-scale polymeric networks. These networks contain thermoresponsive polymers that bestow environmental responsiveness to physiologically relevant changes in temperature. The release profile obtained for the reference data derived from a water bath setup used for temperature stimulation is in accordance with the release kinetics deduced from the ThermalMR setup. In conclusion, ThermalMR adds a thermal intervention dimension to an MRI device and provides an ideal testbed for the study of the temperature-induced release of drugs, magnetic resonance (MR) probes, and other agents from thermoresponsive carriers. Integrating diagnostic imaging, temperature intervention, and temperature response control, ThermalMR is conceptually appealing for the study of the role of temperature in biology and disease and for the pursuit of personalized therapeutic drug delivery approaches for better patient care.

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“…Just as shown in Table 2, choosing the appropriate coupling capacitor can make the switching speed of the FET switch faster, but at the same time, the insertion loss, isolation and working bandwidth of the FET switch will become worse, so the comprehensive performance of the FET switch can’t meet the expectations for this switching system. Because of its flexible design, fast switching speed, high power handling and low cost, the PIN diode is used in many applications [34]. Therefore, this paper will design a solid-state switch as the switch of atomic clocks redundant configuration and specifically select the PIN switch as the design reference.…”

Section: Comparison Of Different Rf Switchesmentioning

confidence: 99%

Design of a RF Switch Used in Redundant Atomic Clock Configurations

Hou

Wang

Tang

et al. 2019

Sensors

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Atomic clocks provide frequency reference signals for communication, aerospace, satellite navigation and other systems. The redundant configuration of atomic clocks is necessary for ensuring the continuity and stability of the system. A radio frequency (RF) switch is usually used as a switching device in the switching system of the host atomic clock and the backup atomic clock. When the atomic clock fails, the switching between the host and the backup clock can be carried out quickly. Aiming at the fast switching requirements of atomic clock RF signals, this paper proposes a new series-shunt Positive Intrinsic Negative (PIN) switch design. In this paper, the evaluation of the RF switches is conducted by using the metrics of switching speed, insertion loss, isolation, return loss at on state and return loss at off state. Experimental result shows that the new PIN switch has better and more comprehensive performance metrics than the electromechanical switch, FET switch and conventional PIN switch. In particular, the switching speed is 53 ns faster than the conventional series-shunt PIN switch.

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High peak and high average radiofrequency power transmit/receive switch for thermal magnetic resonance

Abstract: The high-power Tx/Rx switch enables thermal MR applications at 7 T, contributing to the study of the role of temperature in biological systems and diseases. All design files of the switch will be made available open source at www.opensourceimaging.org.

Cited by 10 publications

References 27 publications

A retrofit to enable dynamic steering for transmit arrays without multiple amplifiers

A retrofit to enable dynamic steering for transmit arrays without multiple amplifiers

Controlled Release of Therapeutics from Thermoresponsive Nanogels: A Thermal Magnetic Resonance Feasibility Study

Design of a RF Switch Used in Redundant Atomic Clock Configurations

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