Abstract: A magnetic particle imaging apparatus includes magnets [106,107] that produce a gradient magnetic field having a field free region (FFR), excitation field electromagnets [102,114] that produce a radiofrequency magnetic field within the field free region, high-Q receiving coils [112] that detect a response of magnetic particles in the field free region to the excitation field. Field translation electromagnets create a homogeneous magnetic field displacing the field-free region through the field of view (FOV) allowing the imaging region to be scanned to optimize scan time, scanning power, amplifier heating, SAR, dB/dt, and/or slew rate. Efficient multi-resolution scanning techniques are also provided. Intermodulated low and radio-frequency excitation signals are processed to produce an image of a distribution of the magnetic nanoparticles within the imaging region. A single composite image is computed using deconvolution of multiple signals at different harmonics.

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: The present invention provides a radiotherapy treatment apparatus that includes a treatment beam, a magnetic field disposed parallel collinear to the treatment beam, and a target that is disposed along the treatment beam. The treatment beam can be a charged particle beam, a proton beam, an electron beam, or a linear accelerator (Linac) beam. The magnetic field is from a magnetic resonance imager (MRI), a megavolt x-ray imager, or a kilovolt x-ray imager and is disposed to operate in coordination with operation of the treatment beam and to narrow the beam. The tumor is disposed to rotate with respect to the treatment beam and the magnetic field, or the treatment beam and the magnetic field are disposed to rotate up to 360° with respect to the target when mounted to a ring gantry. The apparatus can include a rotation angle dependent shim disposed to account for Earth's magnetic field.

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: 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: The present invention provides biplanar, symmetrical electromagnets for providing a homogeneous magnetic field. The magnets have coils disposed in two parallel planes. The coils in the two planes are identical. The radii and Ampere-turns of the coils are selected so that a magnetic field between the planes is homogeneous. One preferred embodiment has 6 coils, with 3 coils in each plane. Other embodiments have 8, 10, 10, 12, or more coils. The method of making the coils begins with an equation for the spherical harmonic coefficients describing the fields from a coil as a function of radius, position and Ampere-turns. For a magnet with K coils, the first K−1 even spherical harmonic coefficients are set equal or close to zero (the odd coefficients are zero due to symmetry of the magnet). This produces a set of equations that, when solved, provides the radii, positions, and Ampere-turns of the K coils. The method can be used to design a biplanar, symmetrical electromagnet with any even number of coils.

Abstract: Biplanar, symmetrical electromagnets for providing a homogeneous magnetic field. The magnets have coils disposed in two parallel planes. The coils in the two planes are identical. The radii and Ampere-turns of the coils are selected so that a magnetic field between the planes is homogeneous. One preferred embodiment has 6 coils, with 3 coils in each plane. Other embodiments have 8, 10, 12, or more coils. The method of making the coils begins with an equation for the spherical harmonic coefficients describing the fields from a coil as a function of radius, position and Ampere-turns. For a magnet with K coils, the first K-1 even spherical harmonic coefficients are set equal to zero (the odd coefficients are zero due to symmetry of the magnet). This produces a set of equations that, when solved, provides the radii, positions, and Ampere-turns of the K coils. The method can be used to design a biplanar, symmetrical electromagnet with any even number of coils.

Abstract: A method of designing a minimum total annual cost solenoidal electromagnet. The magnets are designed using dimensionless shape ratios .alpha. and .beta.. A quantity of conductor material required for a solenoidal magnet is expressed in terms of .alpha. and .beta.. A cost of the conductor material and cost of magnet fabrication are dependent upon the quantity of conductor material. The conductor material cost is depreciated over a number of years to provide a cost per year of conductor material. Similarly, the power consumption of the magnet results in an annual power cost which is dependent upon power consumption. The power consumption is expressed in terms of .alpha. and .beta.. The power cost and conductor material cost are summed and the resulting total annual cost expression can be minimized by appropriately selecting values for .alpha. and .beta.. Magnets built according to such values of .alpha. and .beta. will have low total cost (power cost plus material cost).

Abstract: A very flexible method for designing electromagnets which produce an arbitrary magnetic field. The conductors of the magnet can be constrained to an arbitrary surface or volume. The method provides the lowest power (or shortest wire-length) design given constraints on the desired magnetic field and constraints on where the coils can be located with respect to the desired magnetic field. The method begins with establishing a mesh of nodes and current elements connecting the nodes. The mesh can have any 2 or 3 dimensional shape (e.g. a rectangular grid on a cylinder). The magnet conductors can only be located where current elements are defined. A number of target points are established and a desired magnetic field is defined for each target point. Next, a matrix of coefficients is defined which relates the current in each current element with the magnetic field at each target point. Also, a total power expression is defined for the power consumed in the current elements.

Abstract: Multiple inversion recovery flow imaging employs at least four spin inversion pulses following saturation of static nuclei spins to null nuclei in static material having different spin-lattice relaxation times (T.sub.1) with the inversion pulses being spaced in time to substantially reduce the longitudinal magnetization of the T.sub.1 species present. The saturation of static nuclei spins includes applying a sequence of saturation pulses with adjacent pulses being separated by a diphasing gradient to avoid refocusing coherence. The detection of signals includes applying at least one RF read-out pulse near the nulling point.

Abstract: Disclosed is a method of detecting NMR signals indicative of a short T.sub.2 species in the presence of a long T.sub.2 species by utilizing magnetization transfer between species without requiring an auxiliary RF amplifier and with reduced power deposition (SAR). One or more zero degree RF pulses are applied to a body containing the short T.sub.2 species and the long T.sub.2 species with the pulses being at the resonant frequency. The RF pulses provides selective magnetization saturation of the short T.sub.2 species, and the RF pulses are spaced in time to allow magnetization transfer from the short T.sub.2 species to the long T.sub.2 species. Gradients can then be applied to the body for signal localization with signals detected from the long T.sub.2 species due to magnetization transfer from the short T.sub.2 species being indicative of the presence of the short T.sub.2 species. The signals are indicative also of the magnetization transfer between species.

Abstract: Two-dimensional selective adiabatic pulses invert magnetization from a square region in the xy plane with insensitivity to RF variations. Two-dimensional adiabatic pulses can also invert selectively in frequency and in one spatial dimension. The pulses are useful for both MR imaging and spectroscopy.

Abstract: Magnetic resonance signals for imaging species having short spin-spin relaxation times (T.sub.2) are obtained without the need for a refocusing lobe. A series of RF excitation pulses are applied to the species with magnetic resonance signals being detected after each RF excitation pulse is applied. The magnetic resonance signals are then combined to provide the imaging signals. In one embodiment, each RF excitation pulse is half of a conventional slice-selective pulse with each pulse being slewed to zero. Contrast between the imaged short T.sub.2 species and longer T.sub.2 species can be enhanced by first applying an RF signal having sufficient amplitude to excite the longer T.sub.2 species but insufficient amplitude to excite the short T.sub.2 species whereby the longer T.sub.2 species are tipped by the RF signal. A magnetic gradient can then be applied to dephase the tipped nuclei of the longer T.sub.2 species. The imaging signals are then obtained from magnetic resonance signals from the short T.sub.

Abstract: An adiabatic pulse suitable for generating selective spin echoes for both MR imaging and spectroscopy is described. The pulse requires no gradient reversal to achieve phase compensation. Like adiabatic inversion pulses the new pulse performs a .pi. rotation for any amplitude exceeding a threshold. Unlike inversion pulses, this pulse leaves no phase variation across the slice. The pulse is actually a composite consisting of a 2.pi. and a .pi. pulse. The 2.pi. pulse merely compensates for the phase of the .pi. phase; it performs no net rotation. This compensation is immune to RF inhomogeneity and nonlinearity.

Abstract: In magnetic resonance imaging where a subject is placed in a static field and the subject is selectively excited by applying an RF magnetic field in the presence of a gradient magnetic field, the peak RF power of the RF magnetic field is reduced by decreasing the peak amplitude of the RF magnetic field while concurrently reducing the magnitude of the gradient magnetic field. The incremental time duration for the RF magnetic field portion which is reduced in amplitude is proportionately increased. In using an RF pulse having front and back sidelobes with a positive lobe therebetween, the duration of the RF pulse can be reduced by increasing the magnitudes of the sidelobes and concurrently reducing the time periods of the sidelobes. A minimum SAR embodiment can be realized.