33 results about "Fast marching method" patented technology

The invention discloses a blood vessel segmentation method for a liver CTA sequence image. Firstly contrast enhancement and noise smoothing preprocessing are performed on an inputted three-dimensional liver sequence image; then liver blood vessels and the boundary thereof are enhanced and blood vessel centers are thinned by adopting OOF and OFA algorithms; seed points of the blood vessel center lines are automatically searched according of the geometrical structure of the blood vessels, and the center lines of the liver blood vessels are extracted so as to construct a liver blood vessel tree; and finally the liver blood vessels are preliminarily segmented through combination of a fast marching method and corresponding blood vessel and background gray scale histograms are calculated, and accurate segmentation of the liver blood vessels is realized by adopting an image segmentation algorithm. The liver blood vessels can be effectively and accurately segmented by fully utilizing the geometrical shape and gray scale information of the blood vessels for aiming at the CTA sequence image which is low in contrast, high in noise and fuzzy in boundary. The blood vessel segmentation method for the liver CTA sequence image can be popularized to other three-dimensional blood vessel segmentation.

Aiming at the problems of video multi-target data association and tracking with a large monitoring range and few target appearance features, the invention provides a video multi-target fast tracking method based on a complex condition of improved joint probability data association (JPDA) by utilizing target movement features, that is, the video multi-target fast tracking method is based on the joint probability data association. The invention comprises the steps of calculating the optimal k joint events of JPDA by adopting simplified Murthy algorithm to greatly reduce the computational complexity; discussing movement conditions of targets according to association probability of JPDA, analyzing the current frame measurement and the data association problem of tracking targets in the event of complicated cases such as new appearance, shielding, disappearance, separation and the like of multi targets, and acquires the multi-target tracking trajectory of the complex movements. The method provided by the invention can achieve the video multi-target fast tracking under large monitoring range and greatly improve the tracking performance.

The invention discloses an improved SURF fast matching method, and belongs to the technical field of digital image processing. The improved SURF fast matching method comprises the steps that an original image and an integral image are converted and detection of feature points is conducted through a Hessian matrix; the feature points, obtained by using a scale space, are scale-invariant; positioning of the primary direction of the feature points are conducted by calculating the maximum value responded to a Harr small wave; the feature points are classified through an improved feature-point classifying method and feature describing is conducted on the feature points and a 66 dimension feature vector is formed; matching of feature points in a set is conducted finally. According to the improved SURF fast matching method, selected feature points in one image are not needed to be matched with all the feature points in another image, both matching speed and accuracy are greatly improved, and the improved SURF fast matching method has the advantages that the improved SURF fast matching method has properties, such as scale invariance and translation rotating resistance, of classic SURF (Speeded Up Robust Features).

The invention provides a complex-velocity-distribution regional rock micro-seismic seismic source positioning method. The method comprises the following steps: 1) defining a monitor region, establishing a three-dimensional rectangular coordinate system in the monitor region and dividing the monitor region into a three-dimensional mesh, and numbering each node of the three-dimensional mesh and recording space coordinate of each node; 2) arranging sensors in the monitor region, and grouping the each sensor to the three-dimensional mesh node closest to the sensor; 3) when the monitor region has microearthquake, using the sensors to collect waveform initial arriving moment of P wave generated in the microearthquake; 4) giving corresponding wave velocity values to the nodes of the three-dimensional mesh, and with each sensor being a start point, calculating first arrival traveltime between the node where each sensor locates and the node, of which the serial number is (l, m, n) through a second-order multiple-template fast marching method; and 5) establishing and solving a time difference function f(l, m, n) corresponding to each node, and ordering the obtained function values of the f(l, m, n) in a sequence from small to large, and carrying out arithmetic average based on the node coordinates of the nodes corresponding to the front k function values of the f(l, m, n) to obtain a seismic source coordinate.

The method includes following procedures. Anisotropy diffusion filtering is adopted to remove noise. Excessive segmentation is carried out for images by using Watershed method. Stack data structure is built to locate mesh point with minimum time T in narrow band. Fast marching method makes final segmentation for images. The invention raises speed of segmenting medical image greatly by using Watershed method and improved Fast Marching method, possessing wide adaptability no mater CT image or MR image. Thus, the invention has important application value in area of computer-aided diagnosis and treatment.

The present invention provides a time-optimal route planning method based on an improved level set algorithm. The method comprises: 1, constructing a three-dimensional route planning environmental space; 2, initializing a level set function as a symbol distance function, and setting the AUV navigation starting point on a zero level set; 3, constructing a level set evolution equation considering the influence of the ocean current on the AUV navigation, and constructing a narrow band at the starting point and setting a prohibited area; 4, evolving a level set function according to the level set equation established in the step 3, and storing the zero level set interface of each time step length; 5, determining whether a target point is in the current narrow-band range or not; 6, reconfiguring the narrow band, and employing an improved fast marching method to reinitialize the level set function to be a symbol distance function; and 7, employing a back iterative equation, obtaining the time-optimal route of the AUV, and outputting an optimal route. Through adoption of an ocean current reanalysis database, the time-optimal route planning method based on the improved level set algorithm generates an ocean current field and fully considers the influence of the ocean current in the route planning to allow the planning route to have high practicality.

A technique for calculating traveltime of a seismic wave in three dimensional tilted transversely isotropic (3D TTI) media includes determining a wave vector, defining a unit vector, calculating an angle of the wave vector from an axis and performing a slowness determination. The technique may be practiced as a computer implemented set of instructions, and may be incorporated into measurement equipment.

The invention belongs to the field of resonance diffusion imaging, in particular to a fast-marching fiber tracking method based on topology preservation, comprising the steps of: reading DTI (Diffusion Tensor Imaging) data; manually selecting a seed point and initializing; evoluting from the seed point to peripheral neighbor points by using a fast-marching method and adopting a curvature weighting speed function, recording topology information in an evolution process, i.e. a source node of each evoluting point; calculating all paths by adopting a time gradient descent method; and selecting a real fiber path by a link matrix. The invention has the advantages of more according with the real fiber path by fiber tracking and reducing urious positive branches; and the obtained fiber is smooth and better reflects the fiber direction.

The invention provides a blood vessel extraction method for a live tumor angiogenesis image under an optical resolution photo-acoustic microscope (OR-PAM), and belongs to the field of image processing. First, a tumor angiogenesis image is preprocessed using a variety of enhanced algorithms, which enhances the contrast of small blood vessels effectively and reduces the influence of noise to the greatest degree. Then, a threshold is selected automatically to binaryze the image using an Otsu algorithm, which reduces the mis-classification probability. Finally, the centerline of a blood vessel is measured using a two-step fast marching method, so the calculated centerline can be located in the blood vessel more accurately. Blood vessel extraction using the traditional level set blood vessel extraction algorithm is too slow, while the running speed of the blood vessel extraction algorithm based on the fast marching method is increased greatly. Experimental results show that the method can be used to extract the blood vessel information of a tumor angiogenesis image more effectively, and has a good extraction effect for the information of small blood vessels.

The present invention has disclosed a method and apparatus for lung nodule segmentation in a chest radiograph. The method comprises preprocessing the chest radiograph and propagating the segmentation in the image based on the fast marching method. The method further includes design of velocity function. With the present invention, a fast and robust segmentation can be achieved.

The invention discloses a directional FMM image restoration method for virtual viewpoint images. For a new viewpoint image obtained after depth image based rendering, image restoration is carried out by a directional fast marching method to obtain a new viewpoint image with clear foreground edge. A hole is repaired from left to right for a left virtual viewpoint image, and a hole is repaired from right to left for a right virtual viewpoint image. According to the method of the invention, first, two types of expansion nucleuses are used to perform similar T-shaped expansion and rectangular expansion of a hole marking mask figure, and an original mask figure is subtracted to obtain a narrow edge and a wide edge of a single side; then, the distance from each pixel in the broad edge of the single side to the hole edge is solved; and finally, image restoration is carried out in a particular direction from the narrow edge. Therefore, an effect different from that of a traditional fast marching method is achieved, namely, a large hole can be repaired well. Compared with the traditional fast marching method, the foreground edge information can be kept better by the method of the invention.

The invention relates to the technical field of wireless communication and particularly relates to a spatial characteristic estimation method based on a fast marching method. A signal transmitting source transmits a signal, a signal receiving node receives the signal, and the signal receiving node analyzes the received signal and extracts real transit time between the signal transmitting source and the signal receiving node. The fastest marching path between the transmitting source and the receiving node is searched in a coordinate system with the use of the fast marching method, simulation transit time between the transmitting source and the receiving node is calculated, and meanwhile, the simulation transit time is approached to the real transit time through iteration of an algebraic reconstruction method so as to obtain the spatial characteristics of each coordinate point on the fastest marching path. According to the invention, by making use of the ideas of the fast marching method, estimation and planning of a fast path in an environment are realized, and moreover, the spatial characteristics of a path are estimated by making full use of relevant TOF and speed distribution information acquired in path estimation so as to obtain an environment model, thus improving the accuracy of estimation on communication situation in an unknown environment.

The invention discloses a hybrid two-dimensional seismic travel time calculating method. The method comprises the steps of reading in relevant parameter and speed models; emitting ray to different directions along the seismic focus and calculating central ray information; using a wavefront construction method for calculating the seismic travel time of mesh points within the ray range; classifyingfull-space mesh point travel time attributes and building an initial narrow band on the basis of the attributes; using a fast marching method for calculating the remaining mesh point seismic travel time. By adopting the narrow band technology, the fast marching method and the wavefront construction method are connected, and the seismic travel time calculation precision of the small region near theseismic focus is improved through the wavefront construction method, so that the remaining region mesh node calculation precision of the fast marching method is improved, and two-dimensional seismictravel time calculation achieving the calculation efficiency and the calculation precision is achieved.