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At least 289 records · Page 16Linked to original sources
PubMed1990

Portal dose images. II: Patient dose estimation.

Due to the many sources of uncertainties in radiotherapy, conventional treatment planning can only provide a nominal presentation of the dose delivered to the patient. Provided that large setup errors can be detected and corrected, we propose that measured and calculated portal dose images can be used to improve estimation of patient dose. The iterative approach described in this paper requires an accurate method of dose calculations, 3-dimensional CT data that closely represents the patient and the measured portal dose image. From the CT data, a portal dose image is calculated for comparison with the measured one. The differences are then used to modify the original CT data so that a new image can be calculated. The process is repeated until the calculated and measured images agree to satisfaction. At that point, the internal dose is calculated using the modified CT data. If the method is successful, daily portal dose images could be used to cumulatively estimate patient dose throughout the course of treatment. This manuscript describes 60Co simulation results to demonstrate the feasibility of the approach.

Cobalt Radioisotopes↗
PubMed1990

On-line radiotherapy imaging with an array of fiber-optic image reducers.

In the optical approach for on-line radiotherapy imaging, a large metal sheet-fluorescent screen combination is used to convert the radiation intensity distribution into a visible light image. Data are then captured via a mirror with a camera located out of the beam. Although usable portal images can be acquired, presence of the large mirror renders the system impractical in many treatment geometries. We have overcome this limitation by replacing the mirror with an array of 16 by 16 bundles of plastic fiber-optic image reducers. Each bundle, in turn, is made up of 16 by 16 individual optical fibers. The total of 256 by 256 fibers spans an input area of 40 cm by 40 cm with each individual fiber viewing an area of 1.6 mm by 1.6 mm. Within a height of 12 cm, each fiber is reduced to an area of 0.1 mm by 0.1 mm. The reduced portal image is then turned and "piped" to a final 3.0 cm by 3.0 cm output area. For data acquisition and digitization, the fiber output is directly coupled to the sensor of a TV camera interfaced to a small computer via a 512 by 512 frame grabber. In this initial evaluation, the imaging system has been characterized in terms of its line spread function, noise and resistance to radiation damage. Adequate phantom and patient images are presented.

Fiber Optic Technology↗
PubMed1990

Full integration of the beam's eye view concept into computerized treatment planning.

A complete set of beam's eye view (BEV) and beam portal design features have been integrated into a computerized 3-dimensional radiotherapy treatment planning system. Among the features implemented is the ability to mix BEV graphics with gray-scale images such as simulator and verification radiographs, and digital reconstructed radiographs. Image processing techniques have been developed to both enhance verification images and to detect radiation field boundaries. These portal simulation and presentation techniques are being used clinically to design and verify radiation fields with manual or automatically-designed field shaping blocks. The ability to perform computer dose calculations for planes which are parallel or perpendicular to a specified beam's central axis is available and this feature has also proven useful for treatment plan evaluation and optimization. Finally, direct comparison of computer-generated portal images with actual simulation and verification radiographs is also possible. These techniques allow the direct integration of "CT-directed treatment planning" with block design, simulator films and port films, and other Beam's Eye View-type displays.

Computer Simulation↗
PubMedDate not supplied

3D base: a geometrical data base system for the analysis and visualisation of 3D-shapes obtained from parallel serial sections including three different geometrical representations.

In this paper we discuss a geometrical data base that includes three different geometrical representations of one and the same reconstructed 3D shape: the contour-pile, the voxel enumeration, and the triangulation of a surface. The data base is tailored for 3D shapes obtained from plan-parallel serial sections. It is explained how this geometrical data base is useful with the different processing approaches of a 3D shape, such as analysis and visualisation. Methods of conversion between the geometrical representations are discussed. Examples of the operation of the data base as it is embedded in a data base management system are given by illustrations of retrieval of geometrical information.

Algorithms↗
PubMedDate not supplied

A gray-level thinning method for delineation and representation of arteries.

The quantification of three dimensional (3D) properties of coronary arteries is of significant importance. The performance of the 3D analysis is critically based on low-level representation of the arterial tree for different projections. A skeletal representation of arteries can provide appropriate data structure for registration of multiple angiographic projections and it can be further utilized for 3D reconstruction of the arterial tree. This paper presents an automated method for extracting the skeletal points of an arterial tree directly from the gray-level information without determining the edges a priori. It offers the advantage of improved reliability compared to methods based on detecting dual edges of the arteries. Novel application of filtering techniques provide accurate estimates of the statistics of the background. A recursive search scheme is used to aggregate the skeletal representation at multiple resolutions. Results on a set of Digitally Subtracted Angiograms (DSA) have been presented.

Algorithms↗
PubMed1995

Software control procedures for treatment planning systems.

In radiotherapy treatment planning systems, the software programs as well as the beam data have to be updated frequently, when new software versions are released or as beam data change. This update procedure has to be carried out carefully, to ensure the integrity of the system software and data. Moreover, the version of software used for a particular patient treatment plan is important, not only as a record to be retrieved when necessary, but also when there are multiple terminals connected to the same computer. This process of version control is not always carried out in a systematic and standardized fashion. Most clinics often have their own systems to implement this procedure, but while some systems are comprehensive, others may not necessarily incorporate enough safeguards for errors. In addition, treatment planning system manufacturers often do not offer well-designed and fail-safe facilities for this important issue. This report describes the software update control procedures we have implemented on our treatment planning system as well as suggests some general principles that could be applied to other planning systems.

Computer Systems↗
PubMed2001

The ergonomics of flight management systems: fixing holes in the cockpit certification net.

Recent air traffic control regulations mandate the installation of computer-based flight management systems in airliners across Europe. Integrating and certifying add-on cockpit systems is a long and costly process, which in its current form cannot meaningfully address ergonomics aspects. Two levels of problems occur: add-on systems carry many "classic" HCI failures, which could easily be addressed with modified certification requirements. Further, adding new technology changes practice, creates new skill and knowledge demands and produces new forms of error, which are more difficult to assess in advance. However, one innovative certification approach for add-on cockpit systems, based on the use of a representative population of user pilots, was found to be promising. This method minimizes the subjective bias of individual pilots in addition to defining pass/fail criteria in an operational environment.

Aviation↗
PubMed2001

Java-based graphical user interface for MRUI, a software package for quantitation of in vivo/medical magnetic resonance spectroscopy signals.

This article describes a Java-based graphical user interface for the magnetic resonance user interface (MRUI) quantitation package. This package allows MR spectroscopists to easily perform time-domain analysis of in vivo/medical MR spectroscopy data. We have found that the Java programming language is very well suited for developing highly interactive graphical software applications such as the MRUI system. We also have established that MR quantitation algorithms, programmed in the past in other languages, can easily be embedded into the Java-based MRUI by using the Java native interface (JNI).

Algorithms↗
PubMed1997

DullRazor: a software approach to hair removal from images.

Recently, there has been a growing number of studies applying image processing techniques to analyze melanocytic lesions for atypia and possible malignancy and for total-body mole mapping. However, such lesions can be partially obscured by body hairs. None of these studies has fully addressed the problem of human hairs occluding the imaged lesions. In our previous study we designed an automatic segmentation program to differentiate skin lesions from the normal healthy skin, and learned that the program performed well with most of the images, the exception being those with hairs, especially dark thick hairs, covering part of the lesions. These thick dark hairs confused the program, resulting in unsatisfactory segmentation results. In this paper, we present a method to remove hairs from an image using a pre-processing program we have called DullRazor. This pre-processing step enables the segmentation program to achieve satisfactory results. DullRazor can be downloaded as shareware from http:/(/)www.derm.ubc.ca.

Algorithms↗
PubMed2000

Volumetric measurements of right cerebral hemisphere infarction: use of a semiautomatic MRI segmentation technique.

The applications of a new segmentation software, Anatomatic, in the evaluation of volumetric measurements of brain infarctions and the new Medimag 3D software in the evaluation of 3D image representation of infarctions are described. These programs are applied to magnetic resonance imaging. The aim of this study is to evaluate the use of these software packages in making accurate volumetric measurements in 40 patients with right cerebral infarctions, in determining the correlations between the quantitated lesions and neurological/neuropsychological dysfunctions and in creating realistic 3D views of the infarctions. Using Anatomatic, reproducible infarction volumes were achieved with ease and within a reasonably fast time. Medimag helped achieve realistic 3D representations of the infarctions. When compared, the semiautomatic segmentation proved to be much faster and yielded higher infarction volumes than the manual segmentation technique. Significantly positive correlations between the infarction volumes and neurological dysfunctions and neuropsychological deficit (neglect) helped to explain the effect of volumes on the clinical status of the patients.

Adult↗
PubMed2000

Soft-testing of industrial control systems programmed in IEC 1131-3 languages.

This paper presents a technique and the means for testing PLC-based control software outside the actual plant environment with the purpose of increasing the confidence level on the compliance of the software to functional and temporal requirements. The need to obtain a high confidence level on the correct software operation arises from the fact that in most of the cases it is quite dangerous and expensive to test unproved PLC operation by linking it with the actual facilities that it is going to control. The proposed technique relies on a combined simulation of the controlled plant and the PLC system and an analysis of the plant responses. The PLC system simulation imitates the way software is executed on a PLC that is programmed in the languages of the IEC1131-3 standard. It is based on the programming model of the IEC standard and analytical formulae for estimating the program runtime. The simulation of the plant is based on a discrete convolution model that is solved at the same rate with the rate determined by the control algorithms. A tool realizing these concepts has been developed and its use in testing the control software of three critical outputs of a distillation column is demonstrated.

Computer Simulation↗
PubMed2002

Improving the development of event-driven control systems in the batch processing industry. A case study.

This paper presents the results of an academia-industry collaborative project whose main objective was to test novel techniques for the development of event-driven control systems in the batch processing (e.g., pharmaceutical, fine chemicals, food) industries. Proposed techniques build upon industrial standards and focus on (i) formal synthesis of phase control logic and its automatic translation into procedural code, and (ii) verification of the complete discrete-event control system via dynamic simulation. In order to test the techniques in an engineering environment, a complete discrete-event control system was produced for a benchmark batch process plant based on a standard development method employed by one of the industrial partners. The control system includes functional process specification, control architecture, distributed control system (DCS) proprietary programming code for procedural control at equipment, unit, and process cell levels, and human-machine interfaces: A technical assessment of the development method and the obtained control system was then carried out. Improvements were suggested using the proposed techniques in the specification, code generation and, verification steps. The project assessed the impact of these techniques from both an engineering and economic point of view. Results suggest that the introduction of computer aided engineering (CAE) practices based on the benchmarked techniques and a structured approach could effect a 75% reduction of errors produced in the development process. This translates into estimated overall savings of 7% for green-field projects. Figures were compared with other partners' experience. It is expected that the work load on a given project will shift, increasing the load on process engineers during the specification stage and decreasing the load on the software engineers during the code writing.

Algorithms↗
PubMed1999

Three-dimensional dynamical capabilities of the human masticatory muscles.

Many habitual human jaw movements are non-symmetrical. Generally, it is observed that when the lower incisors move to one side the contralateral condyle moves forwards onto the articular eminence, whereas the ipsilateral condyle stays in the mandibular fossa, moving slightly to the ipsilateral side. These jaw movements are the result of contractions of active masticatory muscles and guided by the temporomandibular joints, their ligaments and passive elastic properties of the muscles. It is not known whether the movements are primarily dependent on passive guidance, active muscle control or both. Therefore, the objective of this study was to analyse the interplay between these factors during non-symmetrical jaw movements. A six-degrees-of-freedom dynamical biomechanical model of the human masticatory system was used. The movements were not restricted to a priori defined joint axes. Jaw movement simulations were performed by unilateral activity of the muscles. The ligaments or the passive elastic properties of the muscles could be removed during these simulations. Laterodeviations conform to naturally observed ones could be generated by unilateral muscle contractions. The movement of the lower incisors was hardly affected by the absence of passive elastic muscle properties or temporomandibular ligaments. The latter, however, influenced the movement of the condyles. The movements could be understood by analysing the combination of forces and torques with respect to the centre of gravity of the lower jaw. In addition, the loading of the condyles appeared to be an important determinant for the movement. This analysis emphasizes that the movements of the jaw are primarily dependent on the orientation of the contributing muscles with respect to this centre of gravity and not on the temporomandibular ligaments or passive elastic muscle properties.

Biomechanical Phenomena↗
PubMed1998

Detecting subtle differences in behavior using waveform display analysis.

We have devised a method, behavioral waveform display analysis, to analyze complex ethological information by measuring behavior in real time and visualizing it as a time-dependent, multistate waveform. To facilitate the generation and statistical analysis of behavioral waveform displays, we have designed a simple Macintosh-based software program. When keystrokes coded to particular behavioral states are entered in real time, this software measures and collates the time, frequency, and duration of each behavioral state. These data can then be displayed either in a tabular format for statistical analysis of behavioral duration and frequency or as graphical coordinates for creating waveform displays by direct importing into graphing programs. An illustration of the use of waveform display analysis to detect anomalous behaviors in cocaine- and amphetamine-treated mice, some of which are not detectable by a standard time-sampling assay, is shown. Both waveform display and time-sampling analysis detected drug-induced changes in sniffing, bar hanging, digging, and rearing. However, unlike time-sampling analysis, waveform display analysis also detected changes in the total duration, frequency, and average duration of these behaviors as well as additional changes in gnawing and locomotion. Additionally, visual scanning of behavioral waveform displays detected drug-induced changes in the patterns of behavior not detectable by time-sampling, including 1) a staged progression to a limited behavioral repertoire consisting of sniffing, locomotion, and rearing; 2) rapid switching between these remaining few behaviors; 3) a delayed onset of postinjection rearing relative to sniffing and locomotion; and 4) the absence of other transient stereotypies during the onset of drug action. These data indicate that behavioral waveform display provides an approach for the detection, visualization, and statistical analysis of aspects of complex behavior not amenable to detection by time-sampling methods.

Amphetamine↗
PubMed1996

Evaluation of iohexol as a marker for the clinical measurement of glomerular filtration rate in dogs.

The contrast medium iohexol can be used as a marker for the measurement of glomerular filtration rate. It has the advantages of sample stability and the availability of a simple, automated (though expensive) analyser. The clearance of iohexol was compared with the clearance of Tc-DTPA in 24 dogs with known or suspected renal impairment. The results were comparable but fractionally lower with iohexol. The correction factors developed for human beings were found to be satisfactory in the dogs, thus validating the software routines used in the automated analyser with the canine samples.

Animals↗
PubMed2001

Prediction of the subcellular location of prokaryotic proteins based on the hydrophobicity index of amino acids.

An algorithm of predicting the subcellular location of prokaryotic proteins is proposed in this paper. In addition to the amino acid composition, the auto-correlation functions based on the hydrophobicity profile of amino acids along the primary sequence of the query protein have been used. Consequently, the best predictive accuracy to date has been achieved. Of the 997 prokaryotic proteins in the database used here, 688 cytoplasmic, 107 extracellular and 202 periplasmic proteins, the overall predictive accuracies are as high as 97.7 and 90.4% in the resubstitution and jackknife tests, respectively, using the hydrophilicity value of Hopp and Woods. The underlying mechanism of the improvement is also discussed. This work would be useful for a systematic analysis of the great amounts of prokaryotic genome sequences. The computer programs used in this paper are available on request via email.

Algorithms↗