39 results about "Inhomogeneous field" patented technology

Methods and pulse sequences for facilitating nuclear magnetic resonance (NMR) measurements in grossly inhomogeneous fields. Methods and pulse sequences according to the invention may be used to accurately measure variables such as transverse relaxation time, longitudinal relaxation time, and diffusion, without the need for data at long recovery time, thereby allowing for faster measurements. In addition, methods and pulse sequences according to embodiment of the invention may allow simultaneous encoding of information in both the amplitude and the shape of echoes, so as to allow a single-shot measurement of multiple variables, e.g., both transverse relaxation time (from the decay of echo amplitudes) and longitudinal relaxation time (from the echo shape). CPMG detection may be used to overcome the often limited signal-to-noise ratio in grossly inhomogeneous fields.

A method to separate two chemically-shifted components of water (w) and fat (f) signals by: (i) estimating the field inhomogeneity β through a treatment of the residuals of the Moore-Penrose solution of the following equations: cos(αnβ)*w+cos [αn(1+β)]*f=real (In) and sin(αnβ)*w+sin [αn(1+β)]*f=imaginary (In), and (ii) using the estimated β to determine the resulting solution for w and f from the original input signals In.

A method to separate two chemically-shifted components of water (w) and fat (f) signals by: (i) estimating the field inhomogeneity β through a treatment of the residuals of the Moore-Penrose solution of the following equations: cos(αnβ)*w+cos [αn(1+β)]*f=real (In) and sin(αnβ)*w+sin [αn(1+β)]*f=imaginary (In), and (ii) using the estimated β to determine the resulting solution for w and f from the original input signals In.

Methods for providing practical magnetic resonance imaging systems that utilize non-homogeneous background fields, B0, as well as, possibly non-linear, gradient fields G1, G2 to make non-invasive measurements to determine, among other things, a spin density function. Two types of non-homogeneous background fields are considered: background fields B0 in which the function |B0| does not have a critical point within the field of view, and background fields B0 such that the function |B0| has a single critical point within the field of view. In the first case, an MR-imaging device may be constructed by using the permanent gradient in the background field, B0, as a slice select gradient, so long as particular criteria are met. In the second case, magnets may be constructed so that |B0| has an isolated non-zero local minimum. Using selective excitation, one can excite only the spins lying in a small neighborhood of this local minimum.

The invention provides a two-dimensional inhomogeneous field experiment device for electrically repairing polluted soil. The two-dimensional inhomogeneous field experiment device comprises a soil sample trough, a gas measuring device, a liquid circulating and measuring device, an electrode control system and a data acquisition system, wherein the soil sample trough comprises a trough body, a top cover, a bottom cover and bolts; center nuts and a plurality of other nuts which are arranged around the center nuts and are in center symmetric and annular are arranged on the top cover and the bottom cover, electrodes are arranged between the upper nuts and the lower nuts, a plurality of probes are uniformly distributed on the top cover, a graded tube is used as the gas measuring device, the liquid circulating and measuring device comprises a connecting pipe, a total distributing pipe, a peristaltic pump and a liquid measuring device, the electrode control system is connected with the electrodes, and the data acquisition system is connected with the probes. The two-dimensional inhomogeneous field experiment device is capable of well simulating the repairing condition of the polluted soil, brings the convenience for monitoring various electric power parameters in real time in an experiment process, is beneficial to removal of pollutants and reduction of energy consumption, is high in system stability, and has an experiment value and an application prospect.

The invention provides an MRI (Magnetic Resonance Imaging) non-uniform field estimation method based on image gradient fitting. The method comprises the following steps: processing an image in a log-domain and decoupling a real image signal and a non-uniform field signal; obtaining the estimation of a non-uniform field through fitting a gradient in an organization region with more uniform grayscale in the image. As gradient processing is performed in the log-domain, a gradient value obtained by a certain pixel is not related to a pixel organization type but is related to the non-uniform field; a special objective function is designed during fitting, so that the estimation of the non-uniform field can be directly obtained through first-order derivatives of the image in an x direction and a y direction without integrating or calculating a second order gradient again.

The invention relates to the technical field of nuclear magnetic resonance imaging, and discloses a measurement method, device, computer equipment and non-uniform field magnetic resonance system of ADC‑T2 two-dimensional atlas, which can be used in extremely non-uniform magnetic fields or extremely short In the echo time NMR system, the ADC coefficient and T2 value are fitted from multiple sets of echo signals by acquiring multiple echo signals collected by CPMG sequences with different echo intervals, so that the ADC‑ The T2 spectrum eliminates the need for complex diffusion weighted sequences, has the advantages of simple algorithm and low system requirements, and can reduce the cost of hardware systems such as spectrometer equipment, RF power amplifiers, and RF coils. At the same time, the measurement method also has the characteristics of stable algorithm, is not easily affected by flowing liquid, and is also suitable for substances with small T1 / T2.

The invention discloses a method and testing device for reducing membrane pollution through an alternate inhomogeneous field. A lower filter cavity and an upper filter cavity are vertically symmetric about a flat plate micro-filtration membrane as a symmetric center, a needle point electrode device is arranged in the upper filter cavity, and a plate electrode is arranged in the lower filter cavity. The needle point electrode device is provided with array type needle point electrodes which are arranged in m rows from left to right and arranged in n lines from front to back, each needle point electrode is connected with a conductor wire, m conductor wires in each line of needle point electrodes pass through hollow pipes to be connected with a wire diverter, and the n wire diverters are connected to a MCU control box. A membrane hole is scoured by different angles through the alternately-changing field, foreign particles are made to move between the surface of the membrane and the electrodes, and the situation that the foreign particles are centralized on the surfaces of the electrodes or the surface of the membrane to cause pollution to the surfaces of the electrodes or the surface of the membrane can be avoided.