Abstract: A magnetic particle imaging system that includes a magnetic field generating system with at least one magnet and providing a gradient magnetic field within an observation region such that the gradient magnetic field has a dynamic field-free region (FFR) for an object under observation having strongly-interacting magnetic particles distributed therein. The magnetic field generating system also includes a drive field and a slow shift field that dynamically shifts the FFR across a field of view (FOV) within the observation region, where the trajectory of the drive field accommodates for a coercivity of the strongly-interacting magnetic particles by ensuring that the particles in the FOV are saturated to a full coercivity field prior to traversing to an opposite-polarity of coercivity. The magnetic particle imaging system also includes a detection system proximate the observation region and configured to detect a signal from the strongly-interacting magnetic particles.

Abstract: Off-resonance imaging uses two complementary contrast agents with the first agent (iron-oxide) particles transfected into cells which provide localized signals. The second agent is detected from a change in the off-resonance signal when present in the cells labeled by the first agent.

Abstract: In imaging a first species having a short T2 magnetic resonance parameter in the presence of a second and third species having longer T2 parameters, a method of suppressing signals from the longer T2 species comprises the steps of: a) applying a RF saturation pulse with multiple suppression bands for the second and third species to excite nuclei spins of the longer T2 species with the magnitude of the RF pulse being sufficiently low so as not to excite nuclei spins of the short T2 species, the RF saturation pulse being sufficiently long to rotate the longer T2 species nuclei spins into a transverse plane, and b) dephasing the longer T2 species nuclei spins in the transverse plane. An imaging pulse sequence is then applied to image the short T2 species.

Abstract: A pulse sequence for use in steady state free precession (SSFP) imaging sequences includes a RF pulse and a time-varying gradient pulse based on a conventional design algorithm such as the Shinnar-LeRoux (SLR) pulse design algorithm and in which amplitude of the RF pulse and gradient pulse are increased while pulse time is decreased thereby reducing imaging time and improving slab profiles.

Abstract: Contrast agents incorporating super-paramagnetic iron-oxide (SPIO) nanoparticles have shown promise as a means to visualize labeled cells using MRI. Labeled cells cause significant signal dephasing due to the magnetic field inhomogeneity induced in water molecules near the cell. With the resulting signal void as the means for detection, the particles are behaving as a negative contrast agent, which can suffer from partial-volume effects. Disclosed is a new method for imaging labeled cells with positive contrast. Spectrally-selective RF pulses are used to excite and refocus the off-resonance water surrounding the labeled cells so that only the fluid and tissue immediately adjacent to the labeled cells are visible in the image. Phantom, in vitro, and in vivo experiments show the feasibility of the new method. A significant linear correlation (r=0.87, p<0.005) between the estimated number of cells and the signal has been observed.

Abstract: A time-optimal MRI gradient design method utilizes constrained optimization to design minimum-time gradient waveforms that satisfy gradient amplitude and slew-rate limitations. Constraints are expressed as linear equations which are solved using linear programming, L1-norm formulation, or second-order cone programming (SOCP).

Abstract: Perturbations in a static magnetic field of magnetic resonance imaging apparatus are compensated by creating magnetic fields near an object creating the perturbations with the magnetic fields adjusted to offset the perturbations in the static magnetic field. In an embodiment where the perturbations are caused by an x-ray detector in a combined modality imaging apparatus, the coils are positioned to surround the x-ray detector and create magnetic fields in the static magnetic field outside of the detector which compensate for the perturbations caused by the x-ray detector.

Abstract: Perturbations in a static magnetic field of magnetic resonance imaging apparatus are compensated by creating magnetic fields near an object creating the perturbations with the magnetic fields adjusted to offset the perturbations in the static magnetic field. In an embodiment where the perturbations are caused by an x-ray detector in a combined modality imaging apparatus, the coils are positioned to surround the x-ray detector and create magnetic fields in the static magnetic field outside of the detector which compensate for the perturbations caused by the x-ray detector.

Abstract: Method of making Optimized electromagnets. The electromagnets have at least three coaxial coils and can be symmetric or asymmetric. The coils can be circular or elliptical. The electromagnets have a coil region in which the coils are located. The coil region can have a bore of any rotationally symmetric shape or any elliptical shape. The coil region is shaped to allow an object to access a predetermined axial magnetic field produced by the magnet. The magnets are optimized in that they require the least amount of power (for resistive electromagnets) or wire length (for superconducting magnets) for the given predetermined axial magnetic field and the shape of the predetermined coil region. The method of present invention restricts the current density in each coil to the same value. This simplification allows the magnet design optimization problem to be cast as a L1-norm minimization linear programming calculation for which a global solution can always be found.

Abstract: A homogeneous field electromagnet having at least two coils in each of two regions. One region has a smaller inner radius than the other region so that the magnet is asymmetrical. The magnet has coils with a smaller radius on one side compared to the other side. This provides the benefit of allowing the magnet to be shorter for a given field of view size (compared to a uniform-radius cylindrical magnet). In a preferred embodiment the magnet is short enough so that a patient's heart can be located within the field of view (FOV) while visual access is provided to the patient's face. Specific dimensions are given for the two regions, including lengths, inner radii, and outer radii. The magnet can also include gradient coils and RF electronics for magnetic resonance imaging.

Abstract: A pulsed strong magnetic field, created with a superconductive coil, is applied to a selected region of the anatomy. Following the pulse a relatively low readout field is used along with a set of spatially orthogonal gradient fields parallel to the readout field. The readout field is chosen such that the noise arises primarily from body losses, and results in negligible susceptibility effects. Following excitation, the resultant signals from the precessing moments are detected, processed and used to make magnetic resonance images of the object. The field pulsing is made efficient using energy recovery.