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Results for “Surgery, Computer-Assisted”

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At least 127 records · Page 7Linked to original sources

PubMed1992

Quantitation of the turbulent stress distribution downstream of normal, diseased and artificial aortic valves in humans.

Damage to blood corpuscles seems to be related to the magnitude and exposure time of the turbulent shear stresses (TSS). According to in vitro studies the critical TSS level for lethal erythrocyte and thrombocyte damage is 150-400 N/m2, for exposure times within physiological ranges. To study the distribution of TSS in the human ascending aorta, a hot-film anemometer needle probe was used to register blood velocities at 41 evenly distributed measuring points in the cross-sectional area 5-6 cm downstream of the aortic annulus. Measurements were made in the ascending aorta after normal aortic valves (prior to coronary bypass surgery), after stenotic aortic valves, and after implantation of either St. Jude Medical or Starr Edwards Silastic Ball valves. Three-dimensional visualization of velocity profiles were performed and Reynolds normal stresses (RNS) were calculated within 50-ms overlapping time windows in systole. By coordinating the mean RNS for each time window and for all 41 measuring points, 2-dimensional color-coded mapping of the RNS distribution was made. Based on the velocity profiles and the RNS distribution a relative blood damage index (RBDI) was calculated to incorporate the magnitude and exposure time for RNS in the entire cross-sectional area into one parameter. Turbulent shear stresses were estimated by using a previously determined correlation equation between RNS and TSS. After normal aortic valves, RNS was below 4 N/m2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1976

A symptomatic discriminant to identify recurrent ulcer in patients with dysperpsia after gastric surgery.

A questionnaire has been completed by 99 patients referred for investigation of symptoms after gastric operations. The replies were analysed in an attempt to distinguish patients with a recurrent peptic ulcer from those with no recurrent ulcer. All cases were investigated by barium meal, endoscopy, and oral cholecystography. All recurrent ulcers were confirmed by reoperation and patients with gastric carcinoma, gallstones, or symptomatic hiatus hernia were excluded. The study was retrospective in 40 patients in whom the diagnosis was already confirmed when the questionnaire was analysed and prospective in 59 in whom the diagnosis was originally unknown. The replies were analysed with (a) a small computer using Bayes' theorem, (b) weighted tables, and (c) a discriminant analysis. The computer prediction of the prospective data was 85% accurate. The results of simpler methods were almost as good as the computer prediction, and questions related only to the severity of pain and vomiting accurately distinguished recurrent ulcer from other causes of dyspepsia in 81% of patients.

Diagnosis, Computer-Assisted↗

PubMed1992

Calculating the surgically induced refractive change following ocular surgery.

Calculating the surgically induced refractive change following ocular surgery is important for evaluating the results of keratore-fractive procedures, smaller incisions and various wound closures for cataract surgery, and the effect of suturing techniques and suture removal following corneal transplant surgery. We present a ten-step method of calculating the spherical- and cylindrical-induced refractive change in a manner suitable for a programmable calculator or personal computer. Several applications are given including (1) adding the overrefraction to the spectacle correction, (2) determining the surgically induced refractive change from the preoperative and postoperative refractions, (3) determining the surgically induced refractive change from the K-readings, (4) rotating axes, (5) determining the power at meridians oblique to the principal meridians of a spherocylinder, (6) determining the coupling ratio, and (7) averaging axes. Standard methods for calculating and reporting aggregate results are also given.

Astigmatism↗

PubMed1992

Evaluation of a collagen/hydroxylapatite implant for orbital reconstructive surgery.

A variety of autogenous and alloplastic materials have been used to correct enophthalmos. Hydroxylapatite (HA), is a calcium-phosphate-based compound that has been extensively studied as a bone replacement material. We studied the properties of a new dense particulate form of HA in a collagen matrix (PFC/HA) implanted in the subperiosteal space of ten rabbit orbits for a period of 6 months. All animals were studied with pre- and postoperative computed tomography (CT) scans, and measurements of induced proptosis and implant volume were made. The proptosis induced by the implant averaged 2.2 mm and was stable over a 6-month period. Implant volume was constant throughout the study. Three-dimensional computer-generated images of the soft tissue, skeletal, and implant surfaces confirmed the implant stability. All animals were studied histologically with fluorochrome bone markers, which revealed minimal foreign body reaction to the implant, no evidence of infection, and marked fibrovascular ingrowth. We found the PFC/HA to possess properties that make it an ideal implant material: ease of availability, ease of handling, no resorption, minimal immunogenicity, infection resistance, no observed migration, biointegration, and no risk of disease transmission. PFC/HA may make an excellent implant material to manage orbital volume.

Animals↗

PubMed1992

Development of a real-time algorithm for predicting sufentanil plasma levels during cardiopulmonary-bypass surgery using a systems approach.

During cardiopulmonary-bypass (CB) procedures, anesthesiologists have traditionally based the administration of narcotics on general dosage recommendations and past experience. Initial doses are usually based on body weight and supplemental amounts are given in anticipation of, or in response to, the effects of surgical stimuli. There has been considerable recent interest in using the population pharmacokinetics of narcotics to optimize the attainment and maintenance of drug plasma concentrations at analgesic target levels which will blunt the hemodynamic responses to noxious stimuli. Moreover, the undershooting or overshooting of the target can be reduced by application of these principles making drug administration more effective and safer. The present study concerns the development of a model for the computer-guided administration of sufentanil throughout surgical procedures involving CB; there is a paucity of studies which have attempted to model the pharmacokinetics of drugs during CB because of the lack of information on the effects of bypass conditions on the pharmacokinetic parameters. We have attempted to approach the effects of hypothermia on sufentanil clearance by applying a continuous temperature correction to the ultimate elimination rate constant (the terminal eigenvalue). This correction is based primarily on the anticipated effects of temperature on the enzyme-catalyzed reactions which are essential for the elimination of drug from the body. An algorithm for the application of the model is also presented.

Algorithms↗

PubMed1975

Atraumatic evaluation of myocardial revascularization procedures with 43K1.

Least-squares regression analysis was computerized to provide functional color images of myocardial perfusion patterns. In 8 of the 9 patients studied, changes in pattern indicated that the revascularization procedure speeded the appearance time and/or net rate of 43K uptake. The functional images correlated well with coronary arteriograms made before and after surgery. This noninvasive isotope technique may prove to be clinically useful in (a) evaluating coronary artery disease, (b) defining the remaining viable myocardium when an aneurysm is present, and (c) determining the effectiveness of the revascularization procedure.

Adult↗

PubMed1992

Staircase assessment of the magnitude and time-course of 50% nitrous-oxide analgesia.

The analgesic effect of 50% nitrous oxide and oxygen on thermal pain sensations was evaluated in a placebo-controlled, double-blind crossover design. In a session immediately before oral surgery, 20 patients used a seven-point verbal scale to rate the intensity of pain sensations evoked by three-second thermal stimuli delivered to 14 sites on the volar forearm at 20-second intervals by a 1-cm-diameter contact thermode. Subjects rated 36 stimuli while breathing room air and then two additional sets of 36 stimuli while inhaling 50% nitrous oxide and oxygen during one set and oxygen placebo during the other. Each of these two stimulus sets was preceded by a two-minute induction of the agent, and the sets were separated by a three-minute washout period. Order of administration was randomized and counterbalanced. Stimulus temperatures were adjusted continuously by an interactive computer program so that response could be maintained at predetermined levels. This method resulted in a continuous measure of analgesia in units of stimulus intensity. Results showed that, in comparison with placebo, nitrous oxide significantly increased the stimulus temperatures (mean = 0.42 degrees C) required to make the same response [F (11,209) = 6.76, p less than 0.0001], indicating analgesia. This increase was one-third to one-half that observed with clinical doses of intravenous fentanyl. Analgesic effects were apparent at three min and wanted 10 min after termination of nitrous-oxide inhalation. These times closely correlated with previous measures of alveolar concentration, further supporting the fast but modest analgesic action of nitrous oxide.

Anesthesia, Dental↗

PubMed1992

A computerized intensive care unit order-writing protocol.

OBJECTIVE: To present a computerized intensive care unit order-writing protocol. DESIGN: Descriptive report. SETTING: Eight-bed surgical intensive care unit, Department of Surgery, Department of Veterans Affairs Medical Center, Bronx, NY. METHODS: IBM-based, computer network program that provides user-friendly, logical, and comprehensive organ-system order sequences for patient management. RESULTS: Since July 1988, an order program that stresses (1) improved and more efficient patient care, (2) the use of program-integrated automatic safety features, (3) the substitution of computer entry for handwriting, and (4) the assurance that physicians deliver obligatory care in a logical organ-system-based progression has been implemented. CONCLUSIONS: The order protocol system presented is simple to introduce and operate, has minimal training and technical requirements, and is demonstrably reliable.

Computer Security↗

PubMed1992

Evaluation of congenital heart disease with MR imaging: current and coming attractions.

Nearly 10 years of experience in the use of MR imaging for the diagnosis of congenital heart disease has accumulated. Although MR imaging is superior to other techniques in showing certain structures and abnormalities such as small central pulmonary arteries in tetralogy of Fallot, aortic coarctations, and venous connections in heterotaxia syndromes, it remains an ancillary tool to echocardiography and cardiac catheterization. In this review, we examine present limitations and advantages of conventional MR in the evaluation of congenital anomalies of the heart and great vessels and explore future developments that might bring MR imaging into the diagnostic mainstream. Key improvements now in development are ultrafast MR systems for acquisition of multiple real-time MR images (in 30 msec or less) and on-line three-dimensional computer reconstruction of the heart and great vessels. Improved display and understanding of complex anatomy, as well as more extensive functional analysis of hearts before and after surgery, should be the benefits of such developments.

Adolescent↗

PubMedDate not supplied

Refractive error changes following strabismus surgery.

Several uncontrolled, retrospective studies have suggested that permanent changes in refractive error can be seen following strabismus surgery. We prospectively enrolled 68 patients undergoing strabismus surgery for evaluation of pre- and postoperative cycloplegic refraction. In addition, the adult patients had computerized corneal topography recorded using the Corneal Modeling System, (Computed Anatomy, Inc, New York, NY). Pre- and postoperative refractions were compared using spherical equivalent and meridional equivalent (90- and 180-degree meridian). We found no significant change in the spherical equivalent between the pre- and postoperative measurements. However, a significant increase in the astigmatic power at 180 degrees (meridional equivalent at 180 degrees) was detected in both pediatric and adult patients. We did not observe any qualitative change in the corneal topography pre- and postoperatively. The change in astigmatic power at 180 degrees is equivalent to additional plus-cylinder correction at 90 degrees and was persistent throughout the 4-month postoperative period.

Adolescent↗

PubMedDate not supplied

Knowledge-based multi-modality three-dimensional image analysis of the brain.

With the recent advances in medical imaging, three-dimensional anatomical and metabolic images of the brain are now available through MR/CT and PET/SPECT imaging modalities. Computerized multi-modality three-dimensional brain image registration and analysis can provide important correlated information for improving diagnosis and studying the pathology of disease. Such analysis may also provide help in planning brain surgery. Further, an anatomical model based quantification and analysis of internal structure can be used to develop a computerized anatomical atlas. Conventional anatomical atlases provide rigid spatial distribution of internal structures extracted from a single subject. The proposed computerized anatomical atlas provides probabilistic spatial distributions which can be easily updated to incorporate the variability of brain structures of subjects selected from pre-defined groups. This paper first presents a review of the current trends in knowledge-based segmentation, labeling, and analysis of MR brain images and then describes the Principal Axes Transformation based registration of three-dimensional MR brain images to develop composite models of selected internal brain structures. The composite models can be used as a computerized anatomical atlas in model-based segmentation and labeling of MR brain images. Three-dimensional labeled MR images of the brain can also be registered and correlated with PET images for analyzing the metabolic activity in the anatomically selected volume of interest. On the other hand, a volume of interest can be selected using the metabolic information and then analyzed for correlated anatomical information using the registered MR-PET images.

Algorithms↗

PubMed1992

[Three-dimensional computerized tomography in trauma surgery. A case presentation].

Three-dimensional images of bone structures can easily be reconstructed from computed tomography data. The technique and the advantages of contemplating reconstructions of bone defects in different directions are described. A special software programme allows to combine all data which are given by the standard CT. The slice diameter is two millimetres. The reconstruction shows bone surfaces in all required views. In traumatic and orthopaedic surgery 3-D-CT is useful in the analysis, detection and preoperative planning of comminuted bone injuries of the spine, pelvis, knee, shoulder and the calcaneus. With this technique it is possible to see the bone in its topographic constellation, to observe fractures in unusual directions and to identify fragments from each other. The surgeon gets a lot of additional information which is helpful to decide on the incision, the reduction and the fixation of fragments. Undesirable effects during operation are reduced, which leads to a more accurate treatment and subsequent better results.

Accidents↗

PubMed1992

Expert computer program for the management of laser surgery.

Since 1960 when the first laser was produced, different types of lasers were developed and over one hundred of them are actually used in medicine. These facts makes very difficult for a surgeon to optimally utilize different types of laser in varying surgical circumstances, unless a laser expert is actually participating in the procedure. As this presence is impractical, if not impossible in every case, we are offering a computer program which presents information in a flexible and friendly way; it is self perfecting and greatly expandable.

Humans↗

PubMedDate not supplied

Computer assisted instruction for preoperative and postoperative patient education in joint replacement surgery.

This article describes a comprehensive system for preoperative and postoperative patient education. The system offers a cost-effective method of instruction which encourages patient interaction and practice with decision making. The system was designed for patients undergoing total joint replacement surgery and includes two preoperative lessons, and a third lesson presented postoperatively at the bedside. The computer lessons were developed using data collected by a patient assessment instrument, and collaboratively with input from a nurse clinical specialist, orthopedic surgeon, physical therapist, and computer programmer. In this project, several advantages for using computer assisted instruction for preoperative and postoperative patient education were identified.

Computer-Assisted Instruction↗

PubMed1992

Electronic imaging of the human body.

The Human Engineering Division of the Armstrong Laboratory (USAF); the Mallinckrodt Institute of Radiology; the Washington University School of Medicine; and the Lister-Hill National Center for Biomedical Communication, National Library of Medicine are sponsoring a working group on electronic imaging of the human body. Electronic imaging of the surface of the human body has been pursued and developed by a number of disciplines including radiology, forensics, surgery, engineering, medical education, and anthropometry. The applications range from reconstructive surgery to computer-aided design (CAD) of protective equipment. Although these areas appear unrelated, they have a great deal of commonality. All the organizations working in this area are faced with the challenges of collecting, reducing, and formatting the data in an efficient and standard manner; storing this data in a computerized database to make it readily accessible; and developing software applications that can visualize, manipulate, and analyze the data. This working group is being established to encourage effective use of the resources of all the various groups and disciplines involved in electronic imaging of the human body surface by providing a forum for discussing progress and challenges with these types of data.

Computer Simulation↗

PubMed1992

An analysis of vitreous tamponade effect in encircling surgery by means of finite element method.

The vitreous tamponade effect in encircling surgery was investigated by means of a finite element method. We performed the simulated encircling surgery on a computer program, which could have alternative band positions, i.e. anterior or posterior band position. Computed results revealed that the band position has a great influence on the vitreous stress distribution, and that the anterior band position is more advantageous than the posterior band position with regard to the vitreous tamponade effect. To our knowledge, this is the first numerical experiment to demonstrate the advantage of the anterior band position in encircling surgery.

Computer Simulation↗

PubMed1992

Digital imaging, image processing, and three-dimensional computer graphics for radiology.

The acquisition of medical images and their display, manipulation, and applications have advanced significantly in the recent past. MR imaging using ultrafast echo planar and fast gradient-echo techniques have expanded application in cardiovascular studies, as well as in the brain and spinal cord. Spiral CT has the potential to revolutionize a well-established modality, subject to several important limitations. The postprocessing of medical sectional images from MR imaging, CT, ultrasound, positron emission tomography, and single-photon emission CT has rapidly grown in importance. We have seen the emergence of renewed and expanded applications of these images, suitably processed, in directing planning and performance of therapeutic procedures on patients through stereotactic techniques, intravascular ultrasound, robot surgery, and integrated displays. This more central role of three-dimensional imaging to medical care is new and will continue to grow. Research applications have recently appeared in neuromorphometry, multimodality registration, functional neuroimaging, quantitative coronary angiography, and saturation MR techniques for myocardial tissue tagging.

Computer Graphics↗

PubMed1978

Enlarged acid-base and blood gas calculations by electronical data computing in the blood gas laboratory.

A rapid anaysis of parameters of the acid-base equilibrium and blood gases during open heart surgery and emergency therapy is absolutely necessary. Computing of the several parameters of the acid-base status by slide rules or nomograms is time consuming and can be shortened by computer applications. The central blood gas laboratory consists of a blood gas analyzer for PO2, PCO2 and pH, an electronic desktop calculator, a four color X-Y-plotter and two data lines to the cardiac surgery unit and to the intensive care unit. The time needed for computing and feedback of the parameters could be decreased to one quarter. In addition to numerical data printout, a graphical representation of the several parameters is possible on a X-Y-plotter and includes the Rahn-Fenn-O2-CO2-Diagram with venous admixture, ventilation perfusion ratio, alveolar dead space ventilation and the standard and actual oxygen dissociation curve as well as the pH/HCO3- Acid-Base nomogram. Furthermore, a computer diagnosis of the actual disturbances can be plotted.

Acid-Base Equilibrium↗