38 results about "Inhomogeneous field" patented technology

A method for determining a location of an object in a three-dimensional localization field created by a localization system includes the following steps: providing a catheter having known spacing between electrodes; providing a lookup table of data correlating locations of an object within the localization field with measurements made by the localization system; placing the catheter into the localization field; using the localization system to determine the location of the electrodes based on the lookup table; calculating an observed distance between electrodes; comparing the observed distance to the known electrode spacing; and adjusting the lookup table to more accurately measure the spacing of the electrodes. A Kernel function, such as the derivative of a Gaussian function, may be used to update the lookup table.

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(α_nβ)*w+cos [α_n(1+β)]*f=real (I_n) and sin(α_nβ)*w+sin [α_n(1+β)]*f=imaginary (I_n), and (ii) using the estimated β to determine the resulting solution for w and f from the original input signals I_n.

The invention provides an MRI image inhomogeneity correction method based on regularization. A lowpass filtering method is improved, part of an area with low grey-value difference is selected and is subjected to lowpass filtering to obtain an initial estimate for a inhomogeneous field, and then extrapolation is performed through a regularized polynomial fitting method to obtain an estimate for an inhomogeneous field of a whole image. According to the method provided by the invention, an area-of-interest is determined and is subjected to filtering, so the boundary effect in the global image filtering method can be avoided, and fitting is performed through a regularization method, thus overfitting is guaranteed not to happen under the condition of improving the fitting order.

A method for determining number of multi-carrier microdischarge secondary electrons distributed in an inhomogeneous field includes: firstly, equally dividing a cross section of an inhomogeneous field distribution area; secondly, subjecting each subdivided area to statistics and accumulation of multi-carrier microdischarge secondary electrons to acquire the electron number of each subdivided area; thirdly, subjecting different areas to redistribution of the secondary electron number according to the diffusion property of the secondary electrons; fourthly, taking the distributed secondary electron number as an initial number to subject each area to statistics and accumulation of secondary electrons again, thereby obtaining the number of the multi-carrier microdischarge secondary electrons distributed in the inhomogeneous field.

The invention relates to the technical field of nuclear magnetic resonance imaging, and discloses a correction measurement method and device for a transverse magnetization vector decay time constant,computer equipment and a non-uniform field magnetic resonance system. In an extremely non-uniform magnetic field or a nuclear magnetic resonance system which cannot realize extremely short echo time,an ADC-T2 two-dimensional atlas is fitted firstly through the acquired echo signals acquired by applying the SE-CPMG sequences with different b values, and then a transverse magnetization vector decaytime constant T2 is corrected so that the problem of a small T2 measurement value caused by diffusion can be avoided. Besides, an accurate ADC-T2 two-dimensional atlas can be further obtained based on the corrected T2 measurement value, T2 value measurement is ensured not to be affected by echo time and molecular diffusion, the requirement for the system is low, and system cost can be reduced.

The invention relates to a field intensity compensation method for constructing an inhomogeneous field through an auxiliary electrode. The field intensity compensation method includes the following steps that the distribution position of the auxiliary electrode is designed in a matrix electrode unit according to the pollutant concentration spatial distribution; the polarity of the auxiliary electrode is designed according to the position relationship between the auxiliary electrode and a matrix electrode; and the inhomogeneous field is constructed through the auxiliary electrode and the matrix electrode, and space compensation for the intensity of the field is achieved. According to the pollutant concentration spatial distribution, on the basis of the matrix electrode, the inhomogeneous field matched with a pollutant concentration field is constructed through space distribution and polarity setting of the auxiliary electrode, the contradiction between the pollutant spatial distribution heterology and the homogeneous field removal efficiency consistency is overcome, the spatial difference of the organic contaminated soil electrokinetic remediation efficiency is avoided, and the overall electrokinetic remediation spatial remediation efficiency is accordingly improved.

The invention relates to a physical system for establishing a complex and multi-domain inhomogeneous field. The physical system comprises a cavity, wherein electric field distribution generated inside and/or applied outside is arranged inside the cavity; one or more visible sub area substances which are capable of changing the electric field distribution according to demands are accommodated inside the accommodation space of the cavity; gaps are formed between a part of or all of the adjacent sub area substances and/or inside sub area substances; gaps can also be formed between the sub area substances and the wall of the cavity; a new electric field can be generated from the sub area substances inside the cavity or partial electric field distribution can be merely changed, so that complex multi-domain electric field distribution can be formed inside the cavity. By adopting the physical system for establishing the complex and multi-domain inhomogeneous field, an expected complex inhomogeneous field can be formed around the sub area substances inside the cavity.

The invention discloses a method for measuring the gradient field of a magnetic resonance system based on a diffusion effect, which consists of a non-uniform field magnet, a nuclear magnetic resonance spectrometer, a radio frequency power amplifier, a radio frequency coil, and a standard quantitative water model with known ADC coefficients and T2 relaxation time constants, etc. composition. Multiple sets of signals are acquired through magnetic resonance sequences with different diffusion-sensitive gradient durations or different echo intervals, and the gradient field size is fitted from the multiple sets of signals. This method does not require additional special magnetic field detection equipment, the measurement time is short, and it is easy to integrate into the magnetic resonance system, which makes it very convenient to complete the gradient field measurement at the installation site, and improves the efficiency of installation and service.

A protocol to determine chemical shift-specific T₁ constants in inhomogeneous fields. Based on intermolecular double-quantum coherences and spatial encoding techniques, the method can resolve overlapped peaks in inhomogeneous fields using the conventional method. With inversion recovery involved, the amplitude of peaks will be modulated by the time of inversion recovery. After fitting the amplitude curves, the corresponding longitudinal relaxation time can be achieved. With the measured T₁ values in inhomogeneous fields, we can have insights into the chemical exchange rates, signal optimization and data quantitation.