7 results about "Diffusion weighting" patented technology

The invention discloses a flow field gradient determination method and device based on iterative diffusion, equipment, a medium and a product, and belongs to the technical field of numerical simulation. The method comprises the following steps: dividing a flow field area into a shock wave area and a smooth area; prior units are selected from the shock wave area and the smooth area, and gradient values of the prior units are calculated; marking the gradient value of the prior unit as a frozen state as a reference value of neighborhood diffusion so as to iteratively update the gradient value of the non-prior unit; in the diffusion process, based on the geometrical relationship between the non-priori unit and each adjacent unit, the anisotropic diffusion weight between the non-priori unit and each adjacent unit is calculated; iteratively updating the gradient value of the non-prior unit by using the diffusion weight and the gradient value of each adjacent unit until a convergence condition is reached; and determining the gradient value of each unit after convergence as the flow field gradient. The precision and stability of gradient calculation can be improved.

The invention relates to the technical field of magnetic resonance imaging, in particular to a two-dimensional magnetic resonance diffusion imaging method and device for inhibiting metal artifacts, and the method comprises the steps: rearranging three-dimensional k-space data corresponding to a magnetic resonance signal based on a frequency band separation algorithm of echo migration, carrying out the conversion to obtain a two-dimensional image arranged in a target direction, separating frequency band components, and obtaining a two-dimensional image; therefore, a frequency band graph capable of reflecting the partial resonance frequency space distribution caused by the metal is generated; and on the basis, inter-layer and intra-layer signal offset is further corrected, and finally a two-dimensional magnetic resonance diffusion imaging image after correction of the metal artifacts is obtained. According to the invention, the metal artifacts can be reduced and inhibited while the scanning time, the imaging resolution, the diffusion weighting intensity and the scanning coverage range are ensured and maintained, so that rapid and high-fidelity magnetic resonance diffusion imaging is realized in the presence of a metal implant.

The invention discloses a method for adjusting ultra-high contrast accurate partition array backlight, and relates to the field of liquid crystal display backlight control. The method comprises the following steps: firstly, generating initial target brightness of a backlight partition based on image content statistics, and calculating a simulated receiving light field containing neighborhood crosstalk by using a pre-constructed optical diffusion weight matrix; on the basis of the deviation between the simulated light field and the target brightness, calculating a correction gain coefficient by using a nonlinear formula containing a halo suppression factor, and adaptively adjusting the suppression intensity in combination with a boundary brightness gradient; and generating a driving signal through time domain smoothing and nonlinear mapping, and reversely compensating the liquid crystal transmittance. Through accurate light field simulation and nonlinear correction, the problems of halo effect and brightness distortion generally existing in the traditional partition backlight technology are effectively solved, and the contrast ratio and uniformity of a display picture are remarkably improved.

The application discloses a flow field gradient determination method and device based on iterative diffusion, equipment, medium and product, and belongs to the technical field of numerical simulation. The method comprises the following steps: dividing a flow field region into a shock region and a smooth region; selecting prior units from the shock region and the smooth region respectively, and calculating gradient values of the prior units; marking the gradient values of the prior units as a frozen state as reference values for neighborhood diffusion, so as to iteratively update gradient values of non-prior units; in the diffusion process, based on the geometric relationship between the non-prior unit and each adjacent unit, the anisotropic diffusion weight between the non-prior unit and each adjacent unit is calculated; the gradient value of the non-prior unit is iteratively updated by using the diffusion weight and the gradient value of each adjacent unit until a convergence condition is reached; and the gradient value of each unit after convergence is determined as the flow field gradient. The application can improve the accuracy and stability of gradient calculation.

This invention relates to a method and system for denoising phase-shifted shear speckle interferograms, specifically within the field of phase-shifted shear speckle interferogram denoising technology. The method includes: acquiring several phase-shifted shear speckle interferograms; calculating discrete complex phase quantities based on the several phase-shifted shear speckle interferograms, and calculating discrete wrapped phases based on the discrete complex phase quantities; calculating phase confidence weights based on the discrete complex phase quantities and discrete wrapped phases; constructing diffusion weight coefficients based on the phase confidence weights; calculating discrete phase gradients based on the discrete wrapped phases using a finite difference method, and performing weighted diffusion processing on the discrete phase gradients based on the diffusion weight coefficients; and reconstructing the phase of the phase-shifted shear speckle interferograms based on the weighted diffusion processed discrete phase gradients to obtain the denoised phase distribution. This invention can effectively denoise phase-shifted shear speckle interferograms.

The invention relates to a splicing seam repairing method and device, electronic equipment and a readable medium, and the method comprises the steps: obtaining an original DR image collected by DR equipment, and determining a first candidate region corresponding to the position of a grid of the DR equipment on the original DR image; performing multi-algorithm joint calculation on the original DR image based on the first candidate region to determine a splicing seam region in the first candidate region; performing local statistics on the splicing seam region and the neighborhood thereof to obtain local gray feature information, and taking the local gray feature information as a dynamic threshold constraint; and under the constraint of a dynamic threshold value, a weighted diffusion equation is constructed based on the main structure direction and the diffusion weight determined by a structure tensor, iterative repair is carried out on the splicing seam area according to the weighted diffusion equation, and the structure tensor is obtained by calculating gradient information of the splicing seam area and a neighborhood of the splicing seam area. The problem of how to ensure the structure continuity and the detail integrity while repairing the splicing seam of the DR image is solved.

Various systems and methods for T2 weighted and / or diffusion weighted chirp CPMG sequences are disclosed herein. In one aspect, a method may include projecting a magnetic field along a longitudinal axis and toward an object of interest and transmitting a sequence of radio frequency pulses to a radio frequency coil assembly configured to selectively excite magnetization in the object of interest. The radio frequency pulse sequence may include a sweep excitation pulse and a series of sweep refocusing pulses following the excitation pulse. In some aspects, the radio frequency pulse sequence may include a sweep recovery pulse following a series of refocusing pulses. In some aspects, a method may include transmitting a preparation radio frequency pulse sequence to a radio frequency coil assembly.