Current Issue : October - December Volume : 2012 Issue Number : 4 Articles : 6 Articles
The aim of this study was to eliminate the effect of Poisson noise in scintigrams with a wavelet thresholding method.We developed\r\na new noise reduction method with a wavelet transform. The proposed method was a combination of the translation-invariant\r\ndenoising method and our newly introduced denoising filter which was applicable for Poisson noise. To evaluate the validity of our\r\nproposed method, phantom images and scintigrams were used. The results with the phantom images showed that our method was\r\nbetter than conventional methods in terms of the peak signal-to-noise ratio by 3 dB. Quality of the scintigrams processed with our\r\nmethod was better than that with the conventional methods in terms of reducing Poisson noise while preserving edge components.\r\nThe results demonstrated that the proposed method was effective for the reduction of Poisson noise in scintigrams....
Fracture detection in pelvic bones is vital for patient diagnostic decisions and treatment planning in traumatic pelvic injuries.\r\nManual detection of bone fracture from computed tomography (CT) images is very challenging due to low resolution of the\r\nimages and the complex pelvic structures. Automated fracture detection from segmented bones can significantly help physicians\r\nanalyze pelvic CT images and detect the severity of injuries in a very short period. This paper presents an automated hierarchical\r\nalgorithm for bone fracture detection in pelvic CT scans using adaptive windowing, boundary tracing, and wavelet transform\r\nwhile incorporating anatomical information. Fracture detection is performed on the basis of the results of prior pelvic bone\r\nsegmentation via our registered active shape model (RASM). The results are promising and show that the method is capable of\r\ndetecting fractures accurately....
Multisection magnetic resonance spectroscopic imaging is a widely used pulse sequence that has distinct advantages over other\r\nspectroscopic imaging sequences, such as dynamic shimming, large region-of-interest coverage within slices, and rapid data\r\nacquisition. It has limitations, however, in the number of slices that can be acquired in realistic scan times and information loss\r\nfrom spacing between slices. In this paper, we synergize themulti-section spectroscopic imaging pulse sequence withmultichannel\r\ncoil technology to overcome these limitations. These combined techniques now permit elimination of the gaps between slices and\r\nacquisition of a larger number of slices to realize the whole brain metabolite mapping without incurring the penalties of longer\r\nrepetition times (and therefore longer acquisition times) or lower signal-to-noise ratios....
Compressive sensing (CS) has been shown to enable dramatic acceleration of MRI acquisition in some applications. Being\r\nan iterative reconstruction technique, CS MRI reconstructions can be more time-consuming than traditional inverse Fourier\r\nreconstruction. We have accelerated our CS MRI reconstruction by factors of up to 27 by using a split Bregman solver combined\r\nwith a graphics processing unit (GPU) computing platform. The increases in speed we find are similar to those we measure for\r\nmatrix multiplication on this platform, suggesting that the split Bregman methods parallelize efficiently. We demonstrate that the\r\ncombination of the rapid convergence of the split Bregman algorithm and the massively parallel strategy of GPU computing can\r\nenable real-time CS reconstruction of even acquisition data matrices of dimension 40962 or more, depending on available GPU\r\nVRAM. Reconstruction of two-dimensional data matrices of dimension 10242 and smaller took ~0.3 s or less, showing that this\r\nplatform also provides very fast iterative reconstruction for small-to-moderate size images....
Imaging processes built on the Compton scattering effect have been under continuing investigation since it was first suggested\r\nin the 50s. However, despite many innovative contributions, there are still formidable theoretical and technical challenges to\r\novercome. In this paper, we review the state-of-the-art principles of the so-called scattered radiation emission imaging. Basically,\r\nit consists of using the cleverly collected scattered radiation from a radiating object to reconstruct its inner structure. Image\r\nformation is based on the mathematical concept of compounded conical projection. It entails a Radon transform defined on\r\ncircular cone surfaces in order to express the scattered radiation flux density on a detecting pixel. We discuss in particular\r\ninvertible cases of such conical Radon transforms which form a mathematical basis for image reconstruction methods. Numerical\r\nsimulations performed in two and three space dimensions speak in favor of the viability of this imaging principle and its potential\r\napplications in various fields....
Current neuronavigation systems cannot adapt to changing intraoperative conditions over time. To overcome this limitation,\r\nwe present an experimental end-to-end system capable of updating 3D preoperative images in the presence of brain shift and\r\nsuccessive resections. The heart of our system is a nonrigid registration technique using a biomechanical model, driven by the\r\ndeformations of key surfaces tracked in successive intraoperative images. The biomechanical model is deformed using FEM or\r\nXFEM, depending on the type of deformation under consideration, namely, brain shift or resection. We describe the operation\r\nof our system on two patient cases, each comprising five intraoperative MR images, and we demonstrate that our approach\r\nsignificantly improves the alignment of nonrigidly registered images....
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