Systems and methods for a hierarchical mapping framework (HMF} for coil compression are provided. The HMF-based coil compression can be applied to existing coil compression algorithms to improve their performance. The receive channels associated with a coil array are divided into subgroups based on the strength of their mutual correlation. In each subgroup, one or more virtual channels are produced based on the channels not in the subgroup. The virtual channels are produced using a coil compression algorithm subject to a hierarchically semiseparable channel mixing across the subgroups. Images are reconstructed for the subgroups and then combined to produce the final image of the subject.

Described here are a system and method for designing radio frequency (RF) pulses for parallel transmission (pTx) applications, and particularly pTx applications in magnetization transfer (MT) magnetic resonance imaging (MRI). The concept of SAR hopping is implemented using a constrained optimization problem that simultaneously designs multiple RF sub-pulses to maximize power deposition in a bound proton pool while also minimizing local SAR across multiple bound proton pool excitation frequencies. This results in the set of RF waveforms that yield the best excitation profiles for all pulses while ensuring that the local SAR of the average of all pulses is below the regulatory limit imposed by the FDA. Pulses are designed simultaneously while constraining local SAR, global SAR, and peak voltage, explicitly.

A method for determining a global and regular parameterization for a family of spin-excitation pulse sequences in magnetic resonance imaging, with each pulse sequence of the family being a multi-spoke type sequence suitable for selectively exciting nuclear spins in a slice of a volume of interest of a body immersed in a static magnetic field and comprising radiofrequency pulses at a Larmor frequency of the nuclear spins alternated with magnetic gradient pulses. The global parameterization minimizes a function representing a mean deviation from a setpoint of the excitation of the nuclear spins, with the mean being computed for the volume of interest and for all the possible orientations and positions of the slices. It allows a selective excitation sequence to be simply designed for a slice with a random orientation and position.

A method of determining a decoupling matrix of a decoupling system for an array of coils of a parallel transmission magnetic resonance imaging (MRI) system includes obtaining impedance matrix data for the array of coils without the decoupling system, determining, based on the impedance matrix data for the array of coils, an objective function representative of deviation from a decoupled operating condition for the array of coils in which the array of coils are decoupled via the decoupling system, and defining, with a processor, a decoupling matrix representative of a set of impedances of the decoupling system with an iterative procedure that optimizes elements of the decoupling matrix to minimize the objective function and reach the decoupled operating condition.

Parallel transmit Magnetic Resonance MR scanner used to image a conductive object such as an interventional device like a guidewire within a subject. This is achieved by determining which Radio Frequency RF transmission modes produced by the parallel RF transmission elements couple with the conductive object and then transmitting at significantly reduced power so as to prevent excessive heating of the conductive object to an extent that would damage the surrounding tissue of the subject, for example, the coupling RF transmission modes may be generated at less than 30%, preferably around 10% of the normal power levels that would conventionally be used for MR imaging. However, even at these low power levels sufficient electric currents are induced in the conductive device to cause detectable MR signals; the location of the conductive object within the subject can thus be visualised. By fast alternate, or simultaneous, iterative application of low-power coupling mode and normal-power non-coupling modes, both the subject and the conductive object can be imaged. During the calibration step of determining which RF transmission modes couples with the conductive object, instead of physically measuring the current induced in the conductive object using sensors, imaging the conductive object using additional very short series of flip angle RF pulses (vLFA) gives a good approximation of the coupling matrix.

A router (60), for use with magnetic resonance systems (10), selectively routes unique excitation signals, generated by a multi-channel radio-frequency (RF) amplifier, over transmission lines (Tx) to any one of a plurality of connection panels (66) which each accepts at least one RF coil assembly having multiple coil elements (20). Each connection panel (66) includes transceiver ports (68) for connecting at least one conductor (22,24) of the coil elements (20) to a corresponding transceiver channel (T/R). The router (60) selectively routes magnetic resonance signals received by the conductors (22,24) from the transceiver channels (T/R) to a multi-channel RF receiver (41). The coin elements may carry sine-mode currents or uniform currents.

Systems and methods for designing and/or using radio frequency (RF) pulses for in-vivo MRI applications, where the RF pulses are robust against errors due to physiological motion of organs during the respiratory cycle. For example, RF pulses are designed based on multi-channel B1+ maps correlated to different positions of the respiratory cycle.

Provided is a technique capable of achieving safety and image quality at the same time in an MRI device using a transmission coil including plural channels. An SAR distribution is calculated, and an imaging parameter is determined for optimizing a radio frequency magnetic field distribution in an imaging region while suppressing a maximum value of an SAR to be equal to or smaller than a predetermined threshold value. The determined imaging parameter includes a radio frequency magnetic field parameter for specifying radio frequency pulses to be transmitted through each of the plural channels. The SAR distribution is calculated using a database that retains an electric field distribution of each of the plural channels for each subject model retained in advance.

A method and system for reducing Nyquist ghost artifact is provide. The method may include: obtaining a plurality of measured data sets; determining, based on the plurality of measured data sets, in a data space, a plurality of convolution kernels, each convolution kernel relating to all of the plurality of measured data sets; generating, based on the plurality of convolution kernels and the plurality of measured data sets, in the data space, a plurality of synthetic data sets; generating, based on the plurality of synthetic data sets and the plurality of measured data sets, in the data space, a plurality of combined data sets, each combined data set relating to one of the plurality of synthetic data sets and a corresponding measured data set of the plurality of measured data sets; and reconstructing, based on the plurality of combined data sets, an image.

A magnetic resonance imaging apparatus according to the present embodiment includes processing circuitry and imaging control circuitry. The processing circuitry selects a human body model corresponding to a subject from human body models. The processing circuitry estimates local specific absorption rates (SARs) at evaluation points determined using the selected human body model, based on the selected human body model and an amplitude and/or phase of the RF pulse in an imaging protocol for magnetic resonance imaging scheduled to be performed on the subject. The processing circuitry determines whether or not the estimated local SARs fall below a local reference value. The imaging control circuitry executes the imaging protocol by using an amplitude and phase of the RF pulse which make the local SARs fall below the local reference value.