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At least 1,711 records · Page 95Linked to original sources
PubMed1996

Evaluation of dose calculation algorithm of the peacock system for multileaf intensity modulation collimator.

PURPOSE: To evaluate the dose calculation algorithm used in the inverse treatment planning computer system for the intensity modulation multileaf collimator. METHODS AND MATERIALS: The inverse treatment-planning computer system calculates the intensities of multiple pencil beams to achieve an optimal distribution and modulates the beam intensity through the special multileaf collimator. The system's dose calculation algorithm made the two basic assumptions: (a) The tissue-maximum ratios (TMRs) of a single pencil beam have the same values as TMRs for raylines through each pencil beam that are determined from percentage depth dose isodose curves along the long axis of the 2 x 20 cm2 field with all leaves open; and (b) the relative output factors (ROF) of each pencil beam also have the same values as the rayline TMR at d(max) of the 2 x 20 cm2 field. To verify these two assumptions, a special multileaf collimator was installed to our linear accelerator which produces 4 MV x-rays. The TMRs and ROFs for the single leaves 1 through 10 were measured using an ion chamber and TLD dosimeter in either a water or a polystyrene phantom. The values of rayline TMRs were calculated from the measured crossplane isodose curves of the 2 x 20 cm2 field. Comparisons were made between these two sets of data. RESULTS: Based on our measurements, we found that the ROFs of a pencil beam obtained from the rayline TMRs at d(max) are as much as 7.6% greater than that of single pencil beams. The ROF of the 1 x 1 cm2 pencil beam is 4 and 6.5% less than that of a cluster of four neighboring pencil beams forming a 2 x 2 cm2, and a 2 x 20 cm2 field respectively. However, the rayline TMRs are generally larger than the TMRs of a single pencil beam. At a depth of 8 cm, the average depth in the middle of intracranial space, the rayline TMRs of the pencil beams of leaves 1 and 10 are 5.4 and 9% higher than a single pencil beam TMR at the same depth, respectively. Also interesting is to note that the TMRs of each of the single pencil beams were found to be equal. CONCLUSIONS: In our article, evaluations and comparisons of TMRs and ROFs were made for two extreme conditions. The measured values of TMRs and ROFs of a single beam have been shown to be significantly different from those used in the calculations. Because both the TMR and ROF are influenced by the scattering radiation in the same direction, the deviations for these two factors would be expected to be magnified. Thus, for the two extreme situations we have investigated, dose deviations would be on the order of 15%. In real patient treatment; of course, these deviations may be somewhat less, but still significant. Our results, however, show that further investigations are warranted.

Algorithms↗
PubMed1997

Evolution of computer-based information systems and networks to support integrated health care delivery systems.

As health care delivery systems become more integrated with an emphasis on community wellness and prevention, well-developed information infrastructures will be needed to support their activities. The article introduces several previously published independent models for the evolution of integrated delivery systems, computer-based patient records (CPRs), and health information networks as well as a summary model that illustrates the relationship among these entities and their somewhat parallel development.

Chronic Disease↗
PubMed1975

The automated assessment of the effect of flurazepam and nitrazepam on mood state.

Some further results on the effects of the two hypnotic drugs, nitrazepam and flurazepam monohydrochloride, on mood state are described. An automated assessment and scoring system, Computer Assisted Psychometric System (C.A.P.S.), was used to assess mood state and showed that both hypnotics had a mild euphoriant effect even when administered to healthy volunteers during the daytime. This was most marked in the case of nitrazepam. It is argued that such euphoriant side effects should be further investigated as they can occur when hypnotics are administered on a long-term nightly basis, and there may therefore be a dependency aspect for those patients who habitually take such hypnotic drugs. The broad scope of the C.A.P.S. system is also discussed.

Anti-Anxiety Agents↗
PubMed1993

Audit in infection control--data analysis and infections in the intensive care unit.

The importance of high standards of infection control practices in intensive care units is widely accepted. Despite this, few objective measures of the efficacy of such practices have been developed. This hampers clinical audit, which is essential if nosocomial infections are to be kept to a minimum. Small sample size, multiple dependent variables, difficulty in matching populations, and the covert effects of confounding factors and bias, all add to the problems of designing meaningful audit programmes in intensive care settings. Nevertheless, useful analysis can be attempted now that appropriate standards and scoring systems are available. Computer systems can simplify data collection, analysis and reporting but they are no substitute for careful preparation and good statistical technique.

Computers↗
PubMedDate not supplied

Validation of a high-resolution X-ray computed tomography system to measure murine adipose tissue depot mass in situ and longitudinally.

INTRODUCTION: Obesity is a significant public health concern with considerable academic and industrial research effort underway to discover novel drugs to treat this disease. The aim of this study was to validate a recently developed high-resolution X-ray computed tomography (micro CT) system capable of measuring murine adipose tissue depot mass in situ. METHODS: The micro CT was used to generate a series of cross-sectional X-ray images from which individual adipose tissue depot mass was quantified. Four individual adipose tissue depots were studied: inguinal subcutaneous, epididymal, retroperitoneal, and mesenteric. The relationship between micro CT-derived adipose tissue mass and adipose mass measured gravimetrically was determined. The effect of strain (C57/Bl6, C3H/HeNCR1BR, and db/db) and age (49 vs. 99 days) on adipose tissue depot mass was studied. RESULTS: Validation studies in which adipose tissue depot mass was determined by micro CT and by gravimetry were conducted in the three strains of mice at 49 and 99 days of age. The correlation of micro CT and gravimetric measures of adipose tissue mass exceeded 90% in all strains at 99 days, and in the C57/Bl6 and C3H/HeNCR1BR strains at 49 days. At 49 days, the correlation in the db/db strain was 82%. Micro CT methodology distinguished both age and strain differences in the adipose tissue depots studied (P<.0001, in all cases). DISCUSSION: Micro CT is a valid method to quantify the mass of individual adipose tissue depots in mice. This method of determining adipose tissue mass is not a terminal procedure; thus, this methodology may be particularly useful for the longitudinal assessment of the effects of drug intervention on adipose tissue depot mass.

Adipose Tissue↗
PubMed1987

The construction of a simultaneous functional order in nervous systems. II. Computing geometrical structures.

The functional order of a collection of nervous elements is available to the system itself, as opposed to the anatomical geometrical order which exists only for external observers. It has been shown before (Part I) that covariances or coincidences in the signal activity of a neural net can be used in the construction of a simultaneous functional order in which a modality is represented as a concatenation of districts with a lattice structure. In this paper we will show how the resulting functional order in a nervous net can be related to the geometry of the underlying detector array. In particular, we will present an algorithm to construct an abstract geometrical complex from this functional order. The algebraic structure of this complex reflects the topological and geometrical structure of the underlying detector array. We will show how the activated subcomplexes of a complex can be related to segments of the detector array that are activated by the projection of a stimulus pattern. The homology of an abstract complex (and therefore of all of its subcomplexes) can be obtained from simple combinatorial operations on its coincidence scheme. Thus, both the geometry of a detector array and the topology of projections of stimulus patterns may have an objective existence for the neural system itself.

Animals↗
PubMed2002

[Image fusion, virtual reality, robotics and navigation. Effects on surgical practice].

In the new minimally invasive surgical era, virtual reality, robotics, and image merging have become topics on their own, offering the potential to revolutionize current surgical treatment and assessment. Improved patient care in the digital age seems to be the primary impetus for continued efforts in the field of telesurgery. The progress in endoscopic surgery with regard to telesurgery is manifested by digitization of the pre-, intra-, and postoperative interaction with the patients' surgical disease via computer system integration: so-called Computer Assisted Surgery (CAS). The preoperative assessment can be improved by 3D organ reconstruction, as in virtual colonoscopy or cholangiography, and by planning and practicing surgery using virtual or simulated organs. When integrating all of the data recorded during this preoperative stage, an enhanced reality can be made possible to improve intra-operative patient interactions. CAS allows for increased three-dimensional accuracy, improved precision and the reproducibility of procedures. The ability to store the actions of the surgeon as digitized information also allows for universal, rapid distribution: i.e., the surgeon's activity can be transmitted to the other side of the operating room or to a remote site via high-speed communications links, as was recently demonstrated by our own team during the Lindbergh operation. Furthermore, the surgeon will be able to share his expertise and skill through teleconsultation and telemanipulation, bringing the patient closer to the expert surgical team through electronic means and opening the way to advanced and continuous surgical learning. Finally, for postoperative interaction, virtual reality and simulation can provide us with 4 dimensional images, time being the fourth dimension. This should allow physicians to have a better idea of the disease process in evolution, and treatment modifications based on this view can be anticipated. We are presently determining the accuracy and efficacy of 4 dimensional imaging compared to conventional evaluations.

Computer Systems↗
PubMed1987

The development of a system for transillumination computed tomography.

A transillumination computed tomography system has been developed for studies of the breast, testes, neonatal skull and peripheral limbs. Initial experiments on test objects have emphasised the problems of scattering and geometrical dependence of lesion detection that are likely to be encountered in conventional diaphanography, but have demonstrated the feasibility of computed tomography as a means of improving the sensitivity of the transillumination technique. The problems of transillumination computed tomography have been addressed and further areas of research identified.

Humans↗
PubMed2000

Robot-assisted computer enhanced closed-chest coronary surgery: preliminary experience using a Harmonic Scalpel and ZEUS.

BACKGROUND: Successful endoscopic harvesting of arterial conduits is critical to the performance of totally endoscopic bypass grafting. Recent success with computer-enhanced robotic systems in the performance of endoscopic single vessel coronary artery bypass (ENDOCAB) has paved the way for developing techniques for multivessel ENDOCAB. The Harmonic Scalpel (Ethicon Endo-Surgery, Cincinnati, OH) has previously demonstrated versatility and efficacy in manual endoscopic internal thoracic artery (ITA) harvesting. This study was undertaken to determine the feasibility of adapting this technology to a robotic telemanipulation system and its safety and efficacy in telerobotic ITA harvesting. METHODS: The Harmonic Scalpel was adapted to the ZEUS robotic surgical system (Computer Motion, Goleta, CA) and used to harvest the ITA in 19 patients undergoing multivessel off-pump coronary artery bypass (OPCAB) surgery. With the left lung collapsed, the ITA was harvested in all patients with CO2 insufflation through three 5 mm ports in the left chest. Postoperative angiography and transthoracic Doppler studies were performed in all patients. RESULTS: There were no ITA injuries and patients tolerated insufflation without hemodynamic compromise. Side branches were controlled easily without bleeding. Average ITA harvest time was 65 +/- 21 minutes. All vessels were patent after harvesting and demonstrated no angiographic evidence of injury. CONCLUSIONS: This paper demonstrates a technique by which the Harmonic Scalpel can be readily adapted to the ZEUS robotic telemanipulation system. Using this system, ITA's can be safely harvested totally endoscopically within a reasonable time frame for patients undergoing ENDOCAB.

Coronary Angiography↗
PubMed1993

Medical audit: the problem of missing case-notes.

This paper reports the results of a case-note audit undertaken to detect the antenatal risk factors found at the initial booking visit, including the subsequent clinical action taken. From a total of 2,139 case-notes of women booked via an obstetric computer system, and delivered between March 1990 and March 1991, 136 (6.4%) were missing. The results showed that these 136 mothers experienced significantly worse delivery outcomes, ie higher incidence of perinatal death; preterm labour; a baby with a low Apgar score and low birth weight. There was also a higher incidence of perinatal death and babies with a low Apgar score for women booked manually compared with those booked via the computer system. These results show that many audit procedures may be the subject of substantial bias due to the problem of missing information. The extended use of a computer-based medical record system should help to resolve this problem, although hybrid information systems can themselves be biased.

Bias↗
PubMed2000

A guideline implementation system using handheld computers for office management of asthma: effects on adherence and patient outcomes.

OBJECTIVE: To evaluate effects on the process and outcomes of care brought about by use of a handheld, computer-based system that implements the American Academy of Pediatrics guideline on office management of asthma exacerbations. DESIGN: A before-after trial with randomly selected, office-based Connecticut pediatricians. In both the control and intervention phases, physicians collected data from 10 patient encounters for acute asthma exacerbations. During the intervention phase, the computer provided for structured encounter documentation and offered recommendations based on the guideline of the American Academy of Pediatrics. Patients were contacted by telephone 7 to 14 days after the visit to assess outcomes. RESULTS: Nine study-physicians enrolled 91 patients in the control phase and 74 in the intervention phase. Follow-up information was available for 93% of encounters. Use of the intervention was associated with increased mean frequency/visit of: 1) measurements of peak expiratory flow rate (2.18 vs 1.57) and oxygen saturation (1.12 vs.42), and 2) administration of nebulized beta2-agonists (1.25 vs.71). Visits in the intervention phase lasted longer and fees were higher ($145.61 vs $103.11). There were no significant differences in immediate disposition or subsequent emergency department visits, hospitalizations, missed school, or caretaker's missed work during the 7 days post visit. CONCLUSION: Use of handheld computers that provide guideline-based decision support was associated with increased physician adherence to guideline recommendations; however, visits were prolonged, fees were higher, and no improvement could be demonstrated with regard to the observed intermediate-term patient outcomes. Guideline implementers (and users) should be cautious about putting unvalidated recommendations into practice.

Adolescent↗
PubMed1996

A comparison of intensity modulated conformal therapy with a conventional external beam stereotactic radiosurgery system for the treatment of single and multiple intracranial lesions.

PURPOSE: To compare the stereotactic radiosurgery treatment plans generated by a conventional radiosurgery treatment system with the plan generated by a system using intensity modulated beams. METHODS AND MATERIALS: Optimized conformal radiation treatment plans were generated for both single and multiple intracranial lesions using a conventional radiosurgery treatment-planning system computer and the Peacock treatment-planning computer. The Peacock system is a conformal therapy system that uses intensity modulated beams, back projection, and the simulated annealing optimization technique. The dose delivered to critical structures and the target volume were compared by means of dose volume histograms between plans generated by the two different systems. The Radiation Therapy Oncology Group (RTOG) stereotactic radiosurgery criteria were also used to evaluate each plan. RESULTS: (a) For a single small target, radiosurgery plans generated by the conventional radiosurgery system and the Peacock system were comparable. (b) For two separate small targets, where nonoverlapping arcs could be used, plans generated by the two systems were also comparable. (c) For a single large (>4 cm) irregular-shaped target, the Peacock system appeared to be able to generate a treatment plan superior to that of the conventional radiosurgery system. CONCLUSIONS: A treatment plan generated using intensity modulated beams appears to be superior to a multiple isocenter plan using a conventional radiosurgery system, for the treatment of a large irregular shaped intracranial target.

Radiosurgery↗
PubMed2003

Computer simulation system for orthognathic surgery.

OBJECTIVE: The system aimed to make a simulation model of an orthognathic patient without using his/her computed tomography data. DESIGN: The morphological data of the teeth and face were obtained by laser scanner. All the data were integrated in the reference coordinate system of frontal and lateral cephalograms using projection matching technique. SETTING: A case of mandibular prognathism was analyzed and presented. EXPERIMENTAL VARIABLE: About 7 mm (left side) to 6 mm (right side) of mandibular setback with a small rotation was performed on this case. RESULTS: Simulated osteotomies and bone movements help us to analyze the movement of bone and soft tissue. Collisions and gaps generated between bone segments and facial changes are shown. CONCLUSION: This simulation system will be particularly useful for the selection of an optimal operative method in cases in which the change in facial soft tissue shape should be carefully deliberated.

Cephalometry↗
PubMed1966

A computer-oriented system for high-speed recording of operant behavior.

A method is described by which large quantities of data, generated at high and variable rates from a large number of test boxes, are recorded on a single eight-channel punched paper tape. The data, which include a record of the occurrence time of each event in 1/10-sec units, are in a compact form, suitable for conversion to standard Hollerith punched card codes and for decoding and summarizing by a large digital computer. Experience with the system has demonstrated a high degree of accuracy and reliability, and low operating cost.

Animals↗
PubMed2000

CardioOp: an integrated approach to teleteaching in cardiac surgery.

INTRODUCTION/PURPOSE: The complexity of cardiac surgery requires continuous training, education and information addressing different individuals: physicians (cardiac surgeons, residents, anaesthesiologists, cardiologists), medical students, perfusionists and patients. Efficacy and efficiency of education and training will likely be improved by the use of multimedia information systems. Nevertheless, computer-based education is facing some serious disadvantages: 1) multimedia productions require tremendous financial and time resources; 2) the obtained multimedia data are only usable for one specific target user group in one specific instructional context; 3) computer based learning programs often show deficiencies in the support of individual learning styles and in providing individual information adjusted to the learner's individual needs. In this paper we describe a computer-system, providing multiple re-use of multimedia-data in different instructional sceneries and providing flexible composition of content to different target user groups. TOOLS AND METHODS: The ZYX document model has been developed, allowing the modelling and flexible on-the-fly composition of multimedia fragments. It has been implemented as a DataBlade module into the object-relational database system Informix Dynamic Server and allows for presentation-neutral storage of multimedia content from the application domain, delivery and presentation of multimedia material, content based retrieval, re-use and composition of multimedia material for different instructional settings. Multimedia data stored in the repository, that can be processed and authored in terms of our identified needs is created by using a next generation authoring environment called CardioOP-Wizard. High-quality intra-operative video is recorded using a video-robot. Difficult surgical procedures are visualized with generic and CT-based 3D-animations. RESULTS: An on-line architecture for multiple re-use and flexible composition of media data has been established. The system contains the following instructional applications (prototypically implemented): a multimedia textbook on operative techniques, an interactive module for problem based-training, a module for creation and presentation of lectures and a module for patient information. Principles of cognitive psychology and knowledge management have been employed in the program. These instructional applications provide information ranging from basic knowledge at the beginner's level, procedural knowledge for the advanced level to implicit knowledge for the professional level. For media-annotation with meta-data a metainformation system, the CardioOP-Clas has been developed. The prototype focuses on aortocoronary bypass grafting and heart transplantation. CONCLUSION: The demonstrated system reflects an integrated approach in terms of information technology and teaching by means of multiple re-use and composition of stored media-items to the individual user and the chosen educational setting on different instructional levels.

Computer Simulation↗
PubMed1996

A simple computer based system to analyze Morris water maze trials on-line.

The development of a system for the acquisition, analysis and storage of data from open-field water-maze procedures in which rats learn to escape from water onto a hidden platform is described. The use of an object-oriented programming language simplifies the programming of the application and provides scientists without formal training in computer programming the ability to create their own software application. The core hardware is an IBM-compatible AT 486 computer and a video capture board. The Microsoft Windows compatible software is written in G (LabVIEW) and presents the user a graphically based 'virtual instrument' thus simulating functions of real instruments which can be interactively accessed. The graphical approach allows the programmer to make fast and simple adaptations of the software to suit the specific experimental problem. Image analysis software tools (Concept V.i) were integrated into this system which has been used successfully for over 2 years in our lab.

Animals↗