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Pré-Publication, Document De Travail Année : 2019

A fast MOSFET RF switch for low-field NMR and MRI

Résumé

TRansmit Array Spatial Encoding (TRASE) MRI uses trains of rf pulses alternatively produced by distinct transmit coils. Commonly used coil switching involving PIN diodes is too slow for low-field MRI and would introduce wait times between pulses typically as long as each individual pulse in a few mT. A MOSFET-based rf switch is described and characterised. Up to hundreds of kHz, it allows for sub-$\mu$s switching of rf currents from a single amplifier to several coils with sufficient isolation ratio and negligible delay between pulses. Additionally, current switching at null current and maximum voltage can be used to abruptly stop or start pulses in series-tuned rf coils, therefore avoiding the rise and fall times associated with the $Q$-factors. RF energy can be efficiently stored in tuning capacitors for times as long as several seconds. Besides TRASE MRI, this energy storage approach may find applications in fast repeated spin-echo experiments. Here, a three-fold acceleration of TRASE phase-encoding is demonstrated when MOSFET switches are used instead of fast reed relays.
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Dates et versions

hal-02266979 , version 1 (02-09-2019)
hal-02266979 , version 2 (31-10-2019)
hal-02266979 , version 3 (31-05-2022)

Identifiants

  • HAL Id : hal-02266979 , version 1

Citer

Pierre-Jean Nacher, Sashika Kumaragamage, Geneviève Tastevin, Christopher P. Bidinosti. A fast MOSFET RF switch for low-field NMR and MRI. 2019. ⟨hal-02266979v1⟩
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