ABSTRACT
A gradient calculation module based on high performance DSP was designed to meet the needs of digital MRI spectrometer. According to the requirements of users, this apparatus can achieve rotation transformation, pre-emphasis, shimming and other gradient calculation functions in a single chip of DSP. It then outputs gradient waveform data of channel X, Y, Z and shimming data of channel B0. Experiments show that the design has good versatility and can satisfy the functional, speed and accuracy requirements of MRI gradient calculation. It provides a practical gradient calculation solution for the development of digital spectrometer.
Subject(s)
Algorithms , Magnetic Resonance Imaging , Methods , Signal Processing, Computer-Assisted , Software DesignABSTRACT
Objective To design an automatic segmentation algorithm for lung region abstraction from CT images in computer-aided diagnosis(CAD) of lung diseases. Methods Based on the optimal threshold segmentation, an automatic region-growing method was adopted to eliminate the trachea and bronchi, the boundary tracking algorithm was modified for background elimination and lung boundary abstraction. Then, lung boundary repair was performed to obtain a fine boundary. To reduce the sensitivity of threshold selection, an iterative process was employed to find the optimal threshold. A trachea/bronchus extraction method based on position of trachea/bronchus in previous slice was introduced, which avoided selecting seed-point by handle in region-growing. Based on previous searching direction, 8-neighborhood searching method was improved to increase its efficiency. Results Experiments with four chest CT data sets showed that this algorithm was able to abstract the lung region automatically, quickly and with better precision. Conclusion The proposed algorithm is quite efficient for automated lung segmentation in the computed-aided diagnosis of lung diseases.
ABSTRACT
Objective: To develop a way of high-quality real-time three dimension surface reconstruction for high-resolution volume data.Method 3D surface point sets of single organ were using a method of binding the threshold and morphological operations.The normal vector of every surface point was calculated.According to the gray gradients of volume data,the triangle face was replaced by surface points to describe the organ surface,and the surface was displayed with OpenGL interface of display card after defining the color and transparent of the organ surface.Result Based on hardware platform of personal computer,the reconstruction of skeleton and skin for the digitized virtual Chinese man No.1(VCH-M1) from CT database was constructed,the rendering speed was faster than 25 F/s.Conclusion The algorithm is capable of realizing a real-time rendering for 512?512?1720 high resolution volume data.
ABSTRACT
In this paper a new direct volume rendering method is presented for fast extraction of iso-surface by adopting the idea from the Shear-Warp algorithm. By creating the sorted volumetric data from the original volume data and specifying a value range of data which determines the part of the sorted volumetric data traversed, the amount of volume data traversed would be reduced obviously and the extraction operation of iso-surface would be very fast. In addition, we can adjust the value range to obtain the different rendering speed and image quality according to the purpose in application. Moreover, the proposed algorithm will not output any intermediate data after the sorted volumetric data being produced. Therefore, it is possible to realize the rapid 3D surface reconstruction for medical images on the personal computer without the support of any hardware accelerator.
Subject(s)
Humans , Algorithms , Image Interpretation, Computer-Assisted , Image Processing, Computer-Assisted , Imaging, Three-Dimensional , Magnetic Resonance Imaging , Tomography, X-Ray ComputedABSTRACT
It is important to simulate the excitation propagation process of cardiac bio-electricity in the research of ECG forward problem. Traditional methods describe them with wave simulation algorithm such as LFX simulation algorithm and vector propagation algorithm etc, these methods have some problems to certain extent, due to the presence of discreteness of space and time and asymmetry of the myocardium. This paper discussed the simulation algorithm in 2-dimension space under the circumstance of layered and non-layered structure of myocardium. By calculating the theoretic values of simulating time based on Huygen's principle, we found that there were errors in LFX algorithm and no errors in vector propagation algorithm under the circumstance of non-layered structure of the myocardium, no mater what myocardium is isotropic or anisotropic. However, there exist errors from both algorithms when the myocardium has the layered structure. An improved algorithm is proposed and the simulations have been performed to examine the efficacy of the new algorithm, and the errors are reduced obviously. By increasing the number of myocardial blocks in the model, we also analyzed its influence on the error of simulation algorithm.