426 research outputs found
Three dimensional images of the brain surface from standard CT examination
No full textThree-dimensional (3D) image rendering was performed using data from standard CT examinations of the head. In this new method for 3D imaging of the brain surface interactive image segmentation and integral rendering were combined. Interactive segmentation operations meant that 3D images could be obtained within a short period of time. When combined with integral rendering this permits good-quality 3D views, even when generated from standard thick slices, together with visualisation of both the shape and densities of the brain surface. Surface infarctions can be evaluated in terms of their anatomical localisation to gyri and sulci, thus allowing their relationship to functional areas to be better defined. The technique can be an additional, easily obtainable tool, even in routine practice, for a better understanding of neurological signs
Optimization of scanning and processing parameters for the three-dimensional reconstruction in computerized tomography of the facial bones
No full textThe evolution of computer technology has significantly improved the performances of three-dimensional reconstructions from Computed Tomographic images. The authors discuss the examination technique and the modalities of three-dimensional reconstruction based upon a new advanced workstation. This unit is based on a Sun Sparkstation linked with the main computer of the CT scanner. The workstation is extremely fast, the processing time for a high resolution three-dimensional image of the maxillofacial region being about 3 minutes. The scanning parameters, image reconstruction and visualization were investigated on cases of maxillofacial (mainly posttraumatic) conditions. The most important scanning parameters are slice thickness, table incrementation, dose, scan plane. Slice thickness and table incrementation are the parameters bearing the greatest influence on the quality of the three-dimensional images. Dose is also important but bears no influence on image quality: therefore it can be kept as low as possible to reduce patient exposure. The scanning plane has some minor effect; coronal images have some advantages over axial images but in many cases only axial images can be acquired. The reconstruction parameters are the threshold and the matrix. The threshold may range 70 to 300 HU but in most cases ranges 120 to 200 HU. An advantage offered by this system is that it allows threshold values to be changed after the reconstruction has been completed, without performing a new reconstruction. The visualization parameters include four rendering methods, i.e. the surface mode, the integral mode, the maximum intensity projection and the ray sum. The surface mode is the one yielding the best results for bones while the others are used for the reconstruction of soft tissues and vessels. The workstation enables the three-dimensional images to be processed with shading parameters, and to be modified with cut planes, disarticulation methods and other interactive method
Three dimensional reconstructions of the carotid bifurcation from CT images: evaluation of the different rendering methods.
No full textRicostruzioni tridimensionali dei vasi arteriosi intra ed extracranici con tomografia computerizzata.
No full textRicostruzione tridimensionale dei vasi del collo. Valutazione comparativa di diverse tecniche TC
No full textComputed tomography and magnetic resonance in the preoperative staging of the spread of rectal cancer. A correlation with the anatomicopathological aspects
No full textApporto della Tomografia Computerizzata e della Risonanza Magnetica nel bilancio preoperatorio dell’ estensione del cancro del retto. Valutazione correlata con gli aspetti anatomo patologici
No full textTree Buffers
No full textIn runtime verification, the central problem is to decide if a given program execution violates a given property. In online runtime verification, a monitor observes a program’s execution as it happens. If the program being observed has hard real-time constraints, then the monitor inherits them. In the presence of hard real-time constraints it becomes a challenge to maintain enough information to produce error traces, should a property violation be observed. In this paper we introduce a data structure, called tree buffer, that solves this problem in the context of automata-based monitors: If the monitor itself respects hard real-time constraints, then enriching it by tree buffers makes it possible to provide error traces, which are essential for diagnosing defects. We show that tree buffers are also useful in other application domains. For example, they can be used to implement functionality of capturing groups in regular expressions. We prove optimal asymptotic bounds for our data structure, and validate them using empirical data from two sources: regular expression searching through Wikipedia, and runtime verification of execution traces obtained from the DaCapo test suite
A class of algorithms which require nonlinear time to maintain disjoint sets
No full textAbstractThis paper describes a machine model intended to be useful in deriving realistic complexity bounds for tasks requiring list processing. As an example of the use of the model, the paper defines a class of algorithms which compute unions of disjoint sets on-line, and proves that any such algorithm requires nonlinear time in the worst case. All set union algorithms known to the author are instances of the model and are thus subject to the derived bound. One of the known algorithms achieves the bound to within a constant factor
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