| 1. |
- Dewaraja, YK, et al.
(författare)
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A parallel Monte Carlo code for planar and SPECT imaging: implementation, verification and applications in I-131 SPECT
- 2002
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Ingår i: Computer Methods and Programs in Biomedicine. - 0169-2607. ; 67:2, s. 115-124
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports the implementation of the SIMIND Monte Carlo code on an IBM SP2 distributed memory parallel computer. Basic aspects of running Monte Carlo particle transport calculations on parallel architectures are described. Our parallelization is based on equally partitioning photons among the processors and uses the Message Passing Interface (MPI) library for interprocessor communication and the Scalable Parallel Random Number Generator (SPRNG) to generate uncorrelated random number streams. These parallelization techniques are also applicable to other distributed memory architectures. A linear increase in computing speed with the number of processors is demonstrated for Lip to 32 processors. This speed-up is especially significant in Single Photon Emission Computed Tomography (SPECT) simulations involving higher energy photon emitters, where explicit modeling of the phantom and collimator is required. For I-131, the accuracy of the parallel code is demonstrated by comparing simulated and experimental SPECT images from a heart/thorax phantom. Clinically realistic SPECT simulations using the voxel-man phantom are carried out to assess scatter and attenuation correction.
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| 2. |
- Ljungberg, Michael, et al.
(författare)
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A Monte Carlo program for the simulation of scintillation camera characteristics
- 1989
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Ingår i: Computer Methods and Programs in Biomedicine. - : Elsevier BV. - 0169-2607. ; 29:4, s. 257-272
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Tidskriftsartikel (refereegranskat)abstract
- There is a need for mathematical modelling for the evaluation of important parameters for photon imaging systems. A Monte Carlo program which simulates medical imaging nuclear detectors has been developed. Different materials can be chosen for the detector, a cover and a phantom. Cylindrical, spherical, rectangular and more complex phantom and source shapes can be simulated. Photoelectric, incoherent, coherent interactions and pair production are simulated. Different detector parameters, e.g. the energy pulse-height distribution and pulse pile-up due to finite decay time of the scintillation light emission, can be calculated. An energy resolution of the system is simulated by convolving the energy imparted with an energy-dependent Gaussian function. An image matrix of the centroid of the events in the detector can be simulated. Simulation of different collimators permits studies of spatial resolution and sensitivity. Comparisons of our results with experimental data and other published results have shown good agreement. The usefulness of the Monte Carlo code for the accurately simulation of important parameters in scintillation camera systems, stationary as well as SPECT (single-photon emission computed tomography) systems, has been demonstrated.
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| 3. |
- Edvardsson, Hannes, et al.
(författare)
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Compact and efficient 3D shape description through radial function approximation
- 2003
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Ingår i: Computer Methods and Programs in Biomedicine. - 0169-2607 .- 1872-7565. ; 72:2, s. 89-97
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Tidskriftsartikel (refereegranskat)abstract
- A fast and simple method for three-dimensional shape description is described. The method views a 3D object as a radial distance function on the unit sphere, and thus reduces the dimensionality of the description problem by one. The radial distance function is approximated by Fourier methods in the basis of the spherical harmonic polynomials. The necessary integration is carried out on the object boundary, rather than on the unit sphere. Consequently, there is no need of a parameterisation of the object surface. The description makes it possible to compare shapes in a computationally very simple way. Solutions on how to cope with translated and rotated objects are discussed. The method is developed for star-shaped objects, but is stable even if the input image is non-star-shaped. The method is tested in a data set from magnetic resonance imaging (MRI) of the brain. Potential medical applications are discussed. ⌐ 2002 Elsevier Science Ireland Ltd. All rights reserved.
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| 4. |
- Foracchia, Marco, et al.
(författare)
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POPED, a software for optimal experiment design in population kinetics.
- 2004
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Ingår i: Computer Methods and Programs in Biomedicine. - 0169-2607 .- 1872-7565. ; 74:1, s. 29-46
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Tidskriftsartikel (refereegranskat)abstract
- Population kinetic analysis is the methodology used to quantify inter-subject variability in kinetic studies. It entails the collection of (possibly sparse) data from dynamic experiments in a group of subjects and their quantitative interpretation by means of a mathematical model. This methodology is widely used in the pharmaceutical industry (where it is termed "pharmacokinetic population analysis") and recently it is becoming increasingly used in other areas of biomedical research. Unlike traditional kinetic studies, where the number of subjects can be quite small, population kinetic studies require large numbers of subjects. It is, therefore, of great interest to design these studies in the most efficient manner possible, to maximize the information content provided by the data. In this paper we propose an algorithm and a computer program, POPED, for the optimal design of a population kinetic experiment. In particular, the number of samples for each subject and the design of the individual sampling strategies, i.e. the number and location of the time points at which the output variable is sampled, will be considered. Among the various criteria proposed in the literature, D and ED optimality are the ones implemented in our software program, since they are the most widely used. A brief description of the techniques employed to perform design optimization is given, together with some details on their actual implementation. Some examples are then presented to show the program usage and the results provided.
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| 5. |
- Gustafsson, Mikael, et al.
(författare)
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A distributed image-processing system for measurements of intracellular calcium in living cells
- 1991
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Ingår i: Computer Methods and Programs in Biomedicine. - : Elsevier. - 0169-2607 .- 1872-7565. ; 36:4, s. 199-221
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Tidskriftsartikel (refereegranskat)abstract
- During the last decade, image-processing techniques have been introduced as a valuable tool in biologically oriented research. In combination with novel fluorescent probes, these techniques permit assessment of subcellular distributions of several intracellularly important cations, such as free calcium ions and protons. Typically, systems used for image processing are located centrally around the experimental setup. This configuration has drawbacks, mainly because the laborious extraction and processing of data that generally follow an experimental session limits the access to the system for other investigators. We describe here the principles of a distributed image processing system, based on IBM-compatible personal computers (PCs), that without extra hardware can cope with all the necessary image processing involved in imaging of intracellular cations. The potential of the PC as an image processor, however, reaches beyond this specific application and many image processing tasks can be carried out successfully on a standard PC. Thus, the centrally located dedicated image processor is used only for image acquisition in the experimental situation. This in turn optimizes the utilization of expensive resources and increases efficiency. The mouse-operated software is described in detail, so that interested investigators can extract useful parts for integration into their own applications and experimental environment.
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| 6. |
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| 7. |
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| 8. |
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| 9. |
- Knutsson, Hans, et al.
(författare)
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Spatio-temporal filtering of digital angiography image data
- 1998
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Ingår i: Computer Methods and Programs in Biomedicine. - 0169-2607 .- 1872-7565. ; 57:1-2, s. 115-123
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Tidskriftsartikel (refereegranskat)abstract
- As welfare diseases become more common all over the world the demand for angiography examinations is increasing rapidly. The development of advanced medical signal processing methods has with few exceptions been concentrated towards CT and MR while traditional contrast based radiology depend on methods developed for ancient photography techniques despite the fact that angiography sequences are generally recorded in digital form. This article presents a new approach for processing of angiography sequences based on advanced image processing methods. The developed algorithm automatically processes angiography sequences containing motion artifacts that cannot be processed by conventional methods like digital subtraction angiography (DSA) and pixel shift due to non uniform motions. The algorithm can in simple terms be described as an ideal pixelshift filter carrying out shifts of different directions and magnitude according to the local motions in the image. In difference to conventional methods it is fully automatic, no mask image needs to be defined and the manual pixelshift operations, which are extremely time consuming, are eliminated. The algorithm is efficient and robust and is designed to run on standard hardware of a powerful workstation which excludes the need for expensive dedicated angiography platforms. Since there is no need to make additional recordings if the patient moves, the patient is exposed to less amount of radiation and contrast fluid. The most exciting benefits by this method are, however, that it opens up new areas for contrast based angiography that are not possible to process with conventional methods e.g. nonuniform motions and multiple layers of moving tissue. Advanced image processing methods provide significantly better image quality and noise suppression but do also provide the means to compute flow velocity and visualize the flow dynamics in the arterial trees by e.g. using color. Initial tests have proven that it is possible to discriminate capillary blood flow from angiography data which opens up interesting possibilities for estimating the blood flow in the heart muscle without use of nuclear methods.
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| 10. |
- Koch, Sabine, et al.
(författare)
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Controlled Diagnosis-Oriented Enhancement of Automatically Segmented Radiographs in Dentistry
- 1998
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Ingår i: Computer Methods and Programs in Biomedicine. - 0169-2607 .- 1872-7565. ; 57:1-2, s. 125-131
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Tidskriftsartikel (refereegranskat)abstract
- A method for controlled diagnosis-oriented enhancement of selected regions of interest in intraoral radiographs is presented. Image enhancement is accomplished by adaptive non-linear grey scale transformation depending on the result of objective quality measurement. In order to assure reliable image duality measurement as well as controlled image enhancement, automatic image segmentation is applied to avoid the influence of disturbing factors (e.g. metallic restorations) on quality measurement and image enhancement. Based on existing a-priori knowledge about object structure and composition of the selected regions of interest in intraoral radiographs, different image segmentation algorithms and image enhancement procedures were developed for different types of diagnosis. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.
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