A method and apparatus are provided for limiting a B1 field used for magnetic resonance imaging (MRI). The techniques described herein reduce a waste of performance of the B1 field while ensuring patient safety and improving the MR imaging quality.

A local coil apparatus, a magnetic resonance imaging apparatus, and a control method of the local coil apparatus are provided. The local coil apparatus includes a radio frequency (RF) receiving coil configured to receive an RF signal from an object, a temperature sensor configured to sense a temperature of the local coil apparatus, and a reactance controller configured to control a reactance of the RF receiving coil in response to the temperature of the local coil apparatus being greater than or equal to a reference value.

An electrical circuit with one or more semiconductor components (10) is characterized in that at least one semiconductor junction of at least one of the semiconductor components of the electrical circuit is disposed such that the average direction of motion of the charge carriers in the semiconductor junction is essentially parallel to the lines of force of the magnetic field B.sub.0, wherein the corresponding semiconductor component is disposed directly on a substrate (12), which is made of a material with good thermal conduction properties. In this way, undistorted characteristics of the semiconductor component used can be ensured despite the very strong magnetic field and the low operating temperatures.

An RF coil has an improved structure to prevent an excessive heat from being transferred to an object, and a magnetic resonance imaging apparatus includes the same. The MRI apparatus includes an RF coil configured to receive an RF signal, wherein the RF coil may include a first cover configured to allow thermal insulation material to be injected into the inside thereof, a second cover configured to allow thermal insulation material to be injected into the inside thereof and detachably coupled to the first cover to form an inner space with the first cover, and at least one circuit board disposed in the inner space and on which a circuit element configured to receive the RF signal is mounted.

New method of cooling of MRI coil and resonators is disclosed and described. MRI coil designs showed in the disclosure are based solely on the use of copper tube elements filled with liquid nitrogen. Inside the conducting tubes at rf frequency there is no rf electric field, thus the liquid nitrogen presence inside such coils will not have any influence on MRI coil dielectric losses and on the resonant frequency modulation. Liquid nitrogen cooled coils, when in the coil noise regime, demonstrate 2-3 gain of signal-to-noise ratio comparing with room temperature equivalent coils. Methods for making and using both superconducting and normal metal MRI coils and/or arrays in such configurations are also disclosed.

An MRI coil testing system includes a frequency response monitoring subsystem and a temperature monitoring subsystem. The frequency response monitoring subsystem includes an embedded receiver probe configured to measure each individual coil's resonant frequency and nng-up/ring-down time, and a processor configured to output an alert if the resonant frequency or ring-up/ring-down time exceeds or violates respective thresholds. The temperature monitoring subsystem includes an embedded temperature probe configured to monitor the temperature of individual coils and the temperature of a magnetic resonance/radio frequency connector, and a processor configured to output an alert if either temperature exceeds a threshold.

Provided are a receive coil unit, a medical image diagnostic system, and a coil cover with which heat can be released from between the receive coil unit and a subject to an outside. A receive coil unit includes: a coil element that receives a nuclear magnetic resonance signal of a subject; a flexible coil cover that covers a periphery of the coil element; and a plurality of passage forming members disposed on an outer side surface of the coil cover that comes into contact with the subject, the plurality of passage forming members forming a first passage extending in a first direction and a second passage extending in a second direction different from the first direction between the subject and the coil cover.

In a general aspect, a magnetic resonance system is operated. In some examples, an amplifier circuit for a magnetic resonance system includes first and second switch devices, a high-power amplifier (HPA) device, and a power combiner device. The first switch device includes an input port and two output ports. The HPA device includes an HPA input port and an HPA output port. The HPA input port is coupled to a first output port of the first switch device. The second switch device includes input and output ports. The power combiner device includes two input ports and an output port. A first input port of the power combiner device is coupled to the output port of the second switch device. A second input port of the power combiner device is coupled to the second output port of the first switch device along a path that bypasses the HPA device.

In a general aspect, a magnetic resonance system is operated. In some examples, an amplifier circuit for a magnetic resonance system includes first and second switch devices, a high-power amplifier (HPA) device, and a power combiner device. The first switch device includes an input port and two output ports. The HPA device includes an HPA input port and an HPA output port. The HPA input port is coupled to a first output port of the first switch device. The second switch device includes input and output ports. The power combiner device includes two input ports and an output port. A first input port of the power combiner device is coupled to the output port of the second switch device. A second input port of the power combiner device is coupled to the second output port of the first switch device along a path that bypasses the HPA device.