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Strategic approaches to drug design. I. An integrated software framework for molecular modelling.

An integrated molecular graphics and computational chemistry framework is described which has been designed primarily to handle small molecules of up to 300 atoms. The system provides a means of integrating software from any source into a single framework. It is split into two functional subsystems. The first subsystem, called COSMIC, runs on low-cost, serial-linked colour graphics terminals and allows the user to prepare and examine structural data and to submit them for extensive computational chemistry. Links also allow access to databases, other modelling systems and user-written modules. Much of the output from COSMIC cannot be examined with low level graphics. A second subsystem, called ASTRAL, has been developed for the high-resolution Evans & Sutherland PS300 colour graphics terminal and is designed to manipulate complex display structures. The COSMIC minimisers, geometry investigators, molecular orbital displays, electrostatic isopotential generators and various interfaces and utilities are described.

Computer Graphics↗

Fitting nonlinear regression models with correlated errors to individual pharmacodynamic data using SAS software.

Nonlinear regression is widely used in pharmacokinetic and pharmacodynamic modeling by applying nonlinear ordinary least squares. Although the assumption of independent errors is frequently not fulfilled, this has received scant attention in the pharmacokinetic literature. As in linear regression, leaving correlation of errors out of account leads to an underestimation of the standard deviations of parameter estimates. On the other hand, the use of models that accommodate correlated errors requires more care and more computation. This paper describes a method to fit log-normal functions to individual response curves containing correlated errors by means of statistical software for time series. A sample computer program is given in which the SAS/ETS procedure MODEL is used. In particular, the problem of finding appropriate starting values for nonlinear iterative algorithms is considered. A linear weighted least squares approach for initial parameter estimation is developed. The adequacy of the method is investigated by means of Monte Carlo simulations. Furthermore, the statistical properties of nonlinear least squares with and without accommodating correlated errors are compared. Time action profiles of a long-acting insulin preparation injected subcutaneously in humans are analyzed to illustrate the usefulness of the method proposed.

Dose-Response Relationship, Drug↗

Software for genetic linkage analysis: an update.

Recent developments in human genetic linkage analysis have included the appearance of new software and collections of data and program resources, accessible by means of the Internet. Many of these new programs and collections are described, including their availability, literature background, and specific technical information.

Computer Communication Networks↗

Hardware and software requirements for a picture archiving and communication system's diagnostic workstations.

Electronic systems (picture archiving and communications systems [PACS]) for image and multimedia data distribution, archiving, and transmission, represent the future of radiology. The workstation is the point of contact between a PACS and the radiologist or referring physician. Therefore, the acceptance of PACS is highly dependent on workstation functionality and performance. This paper, based on our experience in evaluating commercial workstations and on a review of recent literature, describes hardware and software requirements for diagnostic workstations that could be used for making primary diagnoses in a radiology department. Requirements for PACS workstations for use in referring clinics are also briefly described. These workstations must be able to handle the large volume of images to be viewed efficiently, add new functionality to improve the productivity of physicians, technologists, and other health care providers, and provide enough flexibility to allow the electronic systems to grow as medical imaging technology evolves.

Computer Systems↗

The cardiovascular magnetic resonance machine: hardware and software requirements.

The flexibility of cardiac magnetic resonance imaging (MRI) includes faster imaging for applications such as stress tests, ventricular function, myocardial perfusion and coronary artery imaging. Faster imaging makes greater demands on the hardware and software. Although some cardiac imaging can be performed at 0.5 T, some of the faster techniques demand the higher signal-to-noise ratio of higher main field, and fat suppression in cardiac images is more easily achieved at higher field. Main field inhomogeneity affects rapid imaging and performance in open-access magnets. High gradient performance, low eddy currents and surface receiver coils are essential for fast cardiac imaging and the hardware of these systems including interventional imaging is discussed. The use of ECG signals for prospective and retrospective cardiac synchronization of MRI is examined. Techniques for reducing the major problem of respiratory motion in MRI are surveyed. Flexibility in the computer architecture of the scanner and the electronics generating the pulse sequence and controlling data acquisition is vital in cardiac imaging, for retrospective cardiac gating, respiratory navigator-controlled imaging and "real-time interactive" imaging in a similar manner to ultrasound imaging. Automated measurements from MR images remain under development. The pulse sequences and image display functions a cardiovascular MRI system should support for basic cardiac imaging applications and current clinical research areas are summarized.

Cardiovascular System↗

Comparison of CT- and radiograph-based post-implant dosimetry for transperineal 125I prostate brachytherapy using single seeds and a commercial treatment-planning software.

BACKGROUND AND PURPOSE: The objective of this investigation was a direct comparison of the dosimetry of CT-based and radiograph- based postplanning procedures for seed implants. PATIENTS AND METHODS: CT- and radiograph-based postplans were carried out for eight iodine-125 ((125)I) seed implant patients with a commercial treatment-planning system (TPS). To assess a direct comparison of the dosimetric indices (D90, V100, V400), the radiograph-based seed coordinates were transformed to the coordinate system of the CT postplan. Afterwards, the CT-based seed positions were replaced by the radiograph-based coordinates in the TPS and the dose distribution was recalculated. RESULTS: The computations demonstrated that the radiograph-based dosimetric values for the prostate (D(p)90, V(p)100, and V(p)400) were on average lower than the values of the CT postplan. Normalized to the CT postplan the following mean values were found: D(p)90: 90.6% (standard deviation [SD]: 9.0%), V(p)100: 86.1% (SD: 14.7%), and V(p)400: 79.4% (SD: 14.4%). For three out of the eight patients the D(p)90 decreased to 90% of the initial CT postplan values. The reason for this dosimetric difference is supposed to be evoked by an error of the reconstruction software used. It was detected that the TPS algorithm assigned some sources to wrong coordinates, partly out of the prostate gland. CONCLUSION: The radiograph-based postplanning technique of the investigated TPS should only be used in combination with CT postplanning. Furthermore, complex testing procedures of reconstruction algorithms are recommended to minimize calculation errors.

Algorithms↗

[Guidelines based on decision support software. Quality management in neurological outpatient schizophrenia treatment].

The positive effect of greater adherence to evidence-based guidelines on possibilities of optimizing diagnosis and therapy has been shown various times. Electronic systems for interactive support and systematization of physicians' decision-making represent a relatively new method for implementing guidelines. Introducing the "schizophrenia module", newly developed decision support software is presented combining electronic data processing-based, quality-oriented documentation and interactive decision support in the outpatient treatment for schizophrenic disorders. Structure, functionality, and options of use are presented. Besides classic measures of quality management (benchmarking), electronic decision support systems can contribute to improve process quality and outcome in the treatment of mental diseases.

Ambulatory Care↗

[Definition and specification requirements for PAC-systems (picture archiving and communication system). A performance index with reference to the standard "IEEE Recommended Practice for Software Requirement Specifications"].

PROBLEM: The formulation of requirements is necessary to control the goals of a PACS project. Furthermore, in this way, the scope of functionality necessary to support radiological working processes becomes clear. METHOD: Definitions of requirements and specification are formulated independently of systems according to the IEEE standard "Recommended Practice for Software Requirements Specifications". Definitions are given in the Request for Information, specifications in the Request for Proposal. Functional and non-functional requirements are distinguished. The solutions are rated with respect to scope, appropriateness and quality of implementation. RESULTS: A PACS checklist was created according to the methods described above. It is published on the homepage of the "Arbeitsgemeinschaft Informationstechnologie" (AGIT) within the "Deutsche Röntgengesellschaft" (DRG) (http://www.uni-marburg.de/mzr/agit). CONCLUSION: The checklist provides a discussion forum which should contribute to an agreement on accepted basic PACS functionalities.

Humans↗

Calculation of residence times and radiation doses using the standard PC software Excel.

We developed a program which aims to facilitate the calculation of radiation doses to single organs and the whole body. IMEDOSE uses Excel to include calculations, graphical displays, and interactions with the user in a single general-purpose PC software tool. To start the procedure the input data are copied into a spreadsheet. They must represent percentage uptake values of several organs derived from measurements in animals or humans. To extrapolate these data up to seven half-lives of the radionuclide, fitting to one or two exponentional functions is included and can be checked by the user. By means of the approximate time-activity information the cumulated activity or residence times are calculated. Finally these data are combined with the absorbed fraction doses (S-values) given by MIRD pamphlet No. 11 to yield radiation doses, the effective dose equivalent and the effective dose. These results are presented in a final table. Interactions are realized with push-buttons and drop-down menus. Calculations use the Visual Basic tool of Excel. In order to test our program, biodistribution data of fluorine-18 fluorodeoxyglucose were taken from the literature (Meija et al., J Nucl Med 1991; 32:699-706). For a 70-kg adult the resulting radiation doses of all target organs listed in MIRD 11 were different from the ICRP 53 values by 1%+/-18% on the average. When the residence times were introduced into MIRDOSE3 (Stabin, J Nucl Med 1996; 37:538-546) the mean difference between our results and those of MIRDOSE3 was -3%+/-6%. Both outcomes indicate the validity of the present approach.

Adult↗

Radiological imaging as the basis for a simulation software of ventilation in the tracheo-bronchial tree.

The inhaled route is a promising new way for administering drugs to the human body. Flow and particle deposition in the human respiratory tract depends on the individual's anatomy as well as on the drug composition. A European Framework V Program supported project is currently developing a simulation tool for assessment of drug distribution and deposition. This tool relies heavily on the input of radiological data sets, which are obtained in humans. Both high temporal and spatial resolutions are required, and CT and MRI (including hyperpolarized helium-3 MRI) are applied. The radiological data are integrated into computation fluid dynamics software, which is capable of assessing air-flow profiles and compartmental behaviours. This is complemented by pharmacokinetic models, which should result in a simulation tool that will be of use for the theoretical design of new inhaled therapies. This article describes the special imaging requirements of each region of the respiratory tract and the feasibility of these sophisticated radiological techniques with a view of using these data in a simulation model of the lung.

Administration, Inhalation↗

Fully automated software to monitor wear in prosthetic knees using fluoroscopic images.

Total knee arthroplasty is now a widely accepted treatment for late-stage arthritis. Wear of the polyethylene layer in prosthetic knees is a known cause of implant failure. Early detection of wear may allow prediction of device failure. In this paper we describe a fully automated image processing algorithm to measure the minimum tibiofemoral joint space width (mJSW) for monitoring prosthesis wear radiographically. The femoral portion and tibial plate were automatically delineated and mJSW was calculated in each compartment. The software also delineated the tip of the prosthesis pin in order to make a magnification correction. The algorithm was tested with a set of triplicate acquisitions of 18 fluoroscopic knee images. The RMS standard deviation (RMSSD) for the triplicate measurements was calculated as a figure of merit. The RMSSD was 0.077 and 0.087 mm for the lateral and medial compartments. The computer successfully found the minimum JSW for both compartments in all 54 images. A single case (2% of total) required user interaction to correct for an obvious failure to delineate the prosthesis pin. We document a robust and precise tool for quantifying mJSW to monitor prosthesis wear.

Algorithms↗

Growing Region Segmentation Software (GRES) for quantitative magnetic resonance imaging of multiple sclerosis: intra- and inter-observer agreement variability: a comparison with manual contouring method.

Lesion area measurement in multiple sclerosis (MS) is one of the key points in evaluating the natural history and in monitoring the efficacy of treatments. This study was performed to check the intra- and inter-observer agreement variability of a locally developed Growing Region Segmentation Software (GRES), comparing them to those obtained using manual contouring (MC). From routine 1.5-T MRI study of clinically definite multiple sclerosis patients, 36 lesions seen on proton-density-weighted images (PDWI) and 36 enhancing lesion on Gd-DTPA-BMA-enhanced T1-weighted images (Gd-T1WI) were randomly chosen and were evaluated by three observers. The mean range of lesion size was 9.9-536.0 mm(2) on PDWI and 3.6-57.2 mm(2) on Gd-T1WI. The median intra- and inter-observer agreement were, respectively, 97.1 and 90.0% using GRES on PDWI, 81.0 and 70.0% using MC on PDWI, 88.8 and 80.0% using GRES on Gd-T1WI, and 85.8 and 70.0% using MC on Gd-T1WI. The intra- and inter-observer agreements were significantly greater for GRES compared with MC ( P<0.0001 and P=0.0023, respectively) for PDWI, while no difference was found between GRES an MC for Gd-T1WI. The intra-observer variability for GRES was significantly lower on both PDWI ( P=0.0001) and Gd-T1WI ( P=0.0067), whereas for MC the same result was found only for PDWI ( P=0.0147). These data indicate that GRES reduces both the intra- and the inter-observer variability in assessing the area of MS lesions on PDWI and may prove useful in multicentre studies.

Algorithms↗

[Final clinical indications and etiology in 1,023 enucleations. Descriptive databank evaluation with SPSS software in variable response mode with dummy variables].

BACKGROUND: A new data bank developed for ophthalmopathology using a computer-generated, multidigital data code is expected to be able to accomplish complex clinicopathologic correlations of diagnoses and signs, as provided by (multiple) clinical events and histopathologically proven etiologies, and to facilitate the documentation of new data. PATIENTS AND METHODS: In the ophthalmopathology laboratory 2890 eyes were examined between January 20, 1975 and December 12, 1996. The main diagnoses and patient data from this 22-year period were recorded. To facilitate the presentation of data, a 10-year period with eyes of 976 patients enucleated from December, 1986 to December, 1996 was chosen. Principal and secondary diagnoses served for establishing the data bank. The frequencies of successive histologic and clinical diagnoses were evaluated by a descriptive computing program using an SPSS-multi-response mode with dummy variables and a categorical variable listing of the software (SPSS version 10.0) classified as (a) non-filtered random, (b) filtered by multiple etiologies, and (c) filtered by multiple events. RESULTS: The principal groups (e.g., histologic diagnoses concerning etiology) and subgroups (e.g., trauma, neoplasia, surgery, systemic diseases, and inflammations) were defined and correlated with 798 separate diagnoses. From 11 diagnoses/events ascribed to the clinical cases, 11,198 namings resulted. CONCLUSIONS: Thus, a comparative study of complex etiologies and events leading to enucleation in different hospitals of a specific area may be performed using this electronic ophthalmopathologic data bank system. The complexity of rare disease and integration into a superimposed structure can be managed with this custom-made data bank. A chronologically and demographically oriented consideration of reasons for enucleation is thus feasible.

Causality↗

A new user-friendly software platform for systematic classification of skin lesions to aid in their diagnosis and prognosis.

BACKGROUND AND AIMS: The field of much less invasive nonablative aesthetic surgery continues to grow, but consistent and truly objective evaluation of the sometimes comparatively small improvements in the treated skin remains a problem for both clinicians and patients. In this work, we present the development of a generic, modular and expandable platform to allow user-friendly image manipulation, sampling extraction and computer-assisted evaluation of tissue features in the dermatological/aesthetic field of clinical medicine. MATERIALS AND METHODS: The unique characteristic of the platform is the modular extension of the algorithm gallery by the use of extended value added services, which enables the easy incorporation of new image processing procedures to customise the gallery for specific concerns. A novel algorithm to evaluate skin wrinkles is also presented as a demonstration of this integration process. The software platform is designed to evaluate image-tissue indices and to identify individual or combined descriptors which will more accurately represent differences in skin quality. It is based on a set of indices correlating clinical expert and computer classifications, which build up a constantly expanding tissue catalogue. By means of this catalogue, the different tissue qualities of photographic samples can be assessed according to the different positions of the samples in the catalogue. CONCLUSIONS: This new platform can be used to generate sensitive and objective comparative measurement not only for diagnostic reports on the pre-treatment condition of samples but also for demonstrating the improvement and efficacy of the prescribed treatment to both the clinician and colleagues and the patient, thereby helping to increase the patient satisfaction index.

Algorithms↗

Establishing a Web-based DICOM teaching file authoring tool using open-source public software.

Online teaching files are an important source of educational and referential materials in the radiology community. The commonly used Digital Imaging and Communications in Medicine (DICOM) file format of the radiology community is not natively supported by common Web browsers. The ability of the Web server to convert and parse DICOM is important when the DICOM-converting tools are not available. In this paper, we describe our approach to develop a Web-based teaching file authoring tool. Our server is built using Apache Web server running on FreeBSD operating system. The dynamic page content is produced by Hypertext Preprocessor (PHP). Digital Imaging and Communications in Medicine images are converted by ImageMagick into Joint Photographic Experts Group (JPEG) format. Digital Imaging and Communications in Medicine attributes are parsed by dicom3tools and stored in PostgreSQL database. Using free software available from the Internet, we build a Web service that allows radiologists to create their own online teaching file cases with a common Web browser.

Computer Communication Networks↗

Toward a user-driven approach to radiology software solutions: putting the wag back in the dog.

The relationship between healthcare providers and the software industry is evolving. In many cases, industry's traditional, market-driven model is failing to meet the increasingly sophisticated and appropriately individualized needs of providers. Advances in both technology infrastructure and development methodologies have set the stage for the transition from a vendor-driven to a more user-driven process of solution engineering. To make this transition, providers must take an active role in the development process and vendors must provide flexible frameworks on which to build. Only then can the provider/vendor relationship mature from a purchaser/supplier to a codesigner/partner model, where true insight and innovation can occur.

Health Personnel↗