A magnetic resonance (MR) imaging system includes a transmit radio frequency (RF) coil assembly comprising multiple capacitor banks each coupled to at least one diode that is characterized by a high breakdown voltage such that when the transmit RF coil assembly applies at least one slice-selecting RF pulse to a portion of a subject placed in the magnet to select a particular slice for MR imaging, the capacitor banks are selectively adjusted to improve an RF transmission characteristics of the RF coil assembly in transmitting the at least one slice-selecting RF pulse. The MR imaging system may further include a receive radio frequency (RF) coil assembly configured to, in response to at least the slice-selecting RF pulse, receive at least one response radio frequency (RF) pulse emitted from the selected slice of the portion of the subject; a housing; a main magnet; gradient coils; and a control unit.

A method for shaping an RF pulse for use with an MRI system includes shaping an RF pulse for use with an MRI system that uses an RF coil. The RF pulse is shaped to reduce changes in B1 amplitude and in an off-resonance effect with respect to Larmor frequency as a function of distance from the RF coil.

In a Method and a device for magnetic resonance imaging of a subject using a spoiled gradient echo sequence, a B.sub.0 magnetic field strength of at most 1.5 T is used during the sequence. As part of the sequence a slice select gradient acting as a spoil gradient is played out. Substantially simultaneously with the slice select gradient a predetermined RF pulse is played out in the sequence, wherein a time-bandwidth product of the RF pulse is set so that a majority of the energy of the RF pulse is transmitted in its central main lobe.

An excitation region setting method according to an embodiment includes: receiving a designation of a first region from a user, the first region being designated in a distortion-corrected image that is a magnetic resonance image in which an effect of a distortion of a magnetic field has been corrected; calculating an actual excitation region where a subject is to be excited, based on the designated first region and the effect of the distortion of the magnetic field; and correcting imaging conditions including at least one of an orientation of a slice plane that defines the actual excitation region, or a frequency of a high-frequency magnetic field applied to the subject, in such a manner that the calculated actual excitation region becomes closer to an ideal excitation region represented as the first region.

A novel radio frequency sequence, suitable for performing Magnetic Resonance Imaging (MRI) of 2-dimensional (2D) slices of samples exhibiting short magnetization coherence times (i.e., hard tissues). The SS-ZTE pulse sequence contains the following steps: a) magnetizing all spins in the sample from a longitudinal direction to the transverse plane; b) exciting the 2D slice of interest, which comprises the selective locking of said 2D sample slice magnetization while spoiling the magnetization in the rest of sample volume; c) making the magnetization of the selected 2D slice impervious to reconfigurations of the magnetic field gradients from slice selection to encoding and readout; d) reading out of the free induction decay signal of the sample; e) repeating steps (a-d) with different readout directions, so as to gather a corresponding number of radial spokes of the plane defined by the 2D sample slice.

A method includes displaying a position of a distal end of a medical probe that is being navigated in an organ of a patient on a three-dimensional (3D) map of the organ. In response to an event, a plane of interest including the distal end is selected, a real-time Magnetic Resonance Imaging (MRI) slice of the organ is acquired at the selected plane, and the MRI slice is displayed overlaid on the 3D map.

Apparatus and techniques are described herein for nuclear magnetic resonance (MR) projection imaging. Such projection imaging may be used to control radiation therapy delivery to a subject, such as including receiving reference imaging information, generating a two-dimensional (2D) projection image using imaging information obtained via nuclear magnetic resonance (MR) imaging, the 2D projection image corresponding to a specified projection direction, the specified projection direction including a path traversing at least a portion of an imaging subject, determining a change between the generated 2D projection image and the reference imaging information, and controlling delivery of the radiation therapy at least in part using the determined change between the obtained 2D projection image and the reference imaging information.

In one embodiment, an MRI apparatus includes: a scanner equipped with at least a static magnetic field magnet, a gradient coil, and an RF coil configured to apply RF pulses to an object and receive magnetic resonance signals from the object; and processing circuitry configured to set a pulse sequence in which refocusing pulses are sequentially applied subsequent to application of one excitation pulse and a predetermined number of magnetic resonance signals are acquired in each period between adjacent two refocusing pulses by using a water/fat separation method, such that the magnetic resonance signals are different in echo time TE for each of the plurality of refocusing pulses, cause the scanner to acquire the magnetic resonance signals under the pulse sequence, and generate a computed image from the magnetic resonance signals, the computed image being a magnetic resonance image of the object obtained by computation.

In a structural analysis using NMR techniques, a method for gathering k-value data from frequency encoded spin echoes generated from internal volumes selectively excited by intersecting 90° and 180° slice selective and refocusing RF pulses and subjected to a read gradient for the purpose of quantifying the spatial frequency content of the selected internal volume without contamination by a FID signal, comprising: acquiring spin echo data such that the FID signal generated by imperfections in the 180° slice selective refocusing RF pulse is attenuated by the read gradient such that any remaining FID signal is spatially encoded with higher k-values than the frequency encoded k-values being recorded for subsequent structural analysis while simultaneously providing for t2 t2* and t1 contrast. Other aspects of the invention are disclosed.

Magnetic resonance imaging (MRI) systems and methods to effect MRI data acquisition with reduced noise in fast spin echo (FSE) and spin echo (SE) implementations are described. The improved MRI data acquisition is performed by acquiring k-space data while maintaining a constant or near constant slice select gradient amplitude throughout a sequence kernel. The acquired k-space data can then be used to generate an MR image.