University of California

John Van Heteren

Mitsuaki A Arakawa

Hsu Chang

Lawrence E Crooks

John C Hoenninger, Iii

Keiji Furui

Thomas McDermott

A front end unit (32) for a magnetic resonance imaging (MRI) system (20) comprises a plurality of coil attachment ports (46) to which an RF signal or tuning signal is selectively routed thereby permitting, during operation, coils (22) to remain attached to each of the plurality of ports. A signal routing controller (28, 30) selects to which of the ports the RF signal or tuning signal is to be routed. The RF front end unit (32) is also known as the relay switch board assembly or RSB. Each port of the RF front end is attached to a different RF coil or RF coil combination. Tuning and imaging operations can be conducted for a plurality of coils in succession, without coils having to be detached from the RF front end. The signal routing controller selectively applies the RF signal (from an RF unit) or the tuning signal (from a tuning controller) to the selected coil through a signal path unique to the selected coil. Coils not selected to be operative can be detuned.

MRI front end apparatus and method of operation

An RF front end unit (32) for a magnetic resonance imaging (MRI) system (20) has transmit and receive channels to which a plurality of coils (22) can remain attached during operation (including RF coils having differing types of matching circuits), and facilitates switching between a plurality of attached coils. Methods and apparatus are additionally provided for selectively tuning differing RF coils, including both high power coils (22B, 22C) and varactor-tuned coils (22D). The tuning of a high power coil involves using a remote impedance match tuning network (RTU) (26) for a coarse tuning operation and, if necessary, a fine tuning operation. In performing the coarse tuning operation separately for In-Phase ('I') and Quadrature ('Q') channels, a tuning controller (60) determines the effective load impedance of each of the RF coil channels by quadrature demodulation of their reflected signals. The tuning controller (60) then evaluates a computerized model of the impedance match tuning network in order to determine and set coarse values for the adjustable impedances of the RTU. In tuning varactor coils, the tuning controller chooses a starting point for the varactor coil tune and then executes a two-dimensional bisection search operation to locate a candidate for the tuned point. The bisection search is followed by a starburst operation for examining the magnitude of reflected signals at points in a starburst or asterisk pattern about the candidate point.

Method and apparatus for tuning MRI RF coils

A front end unit (32) for a magnetic resonance imaging (MRI) system (20) comprises a plurality of coil attachment ports (46) to which an RF signal or tuning signal is selectively routed thereby permitting, during operation, coils (22) to remain attached to each of the plurality of ports. A signal routing controller (28, 30) selects to which of the ports the RF signal or tuning signal is to be routed. The RF front end Knit (32) is also known as the relay switchboard assembly or RSB. Each port of the RF front end is attached to a different RF coil or RF coil combination. Tuning and imaging operations can be conducted for a plurality of coils in succession, without coils having to be detached from the RF front end. The signal routing controller selectively applies the RF signal (from an RF unit) or the tuning signal (from a tuning controller) to the selected coil through a signal path unique to the selected coil. Coils not selected to be operative can be detuned.

A local frequency generator employing a single crystal oscillator, latches and direct digital synthesizer circuits digitally produces all signals needed in the transmitter channel of a MRI system to generate MRI transmitter RF pulses. The local frequency generator is operable in both the single side band and double side band modes and has the capability of switching between the modes. The generator is constructed with a phase resetting capability for providing the plural output frequencies needed for making plural MRI slices.

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San Francisco, CA, United States of America

John Van Heteren