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Results for “The Right to Reproduce”

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At least 469 records · Page 26Linked to original sources

PubMed1982

Low radiation iridium 191m radionuclide angiography: detection and quantitation of left-to-right shunts in infants.

Radionuclide angiography using iridium 191m was carried out in 34 premature infants and young children for detection and quantitation of left-to-right shunts. Ir-191m has a physical half-life of 4.96 seconds and can be imaged with conventional gamma scintillation cameras. The whole body radiation absorbed dose from Ir-191m is 3.5 mrad/mCi, which is about 40 times less radiation than with technetium 99m. Other advantages of Ir-191m include high photon flux for improved imaging and the possibility of multiple studies within a short period of time without background. Nine patients had simultaneous measurement of pulmonary-to-systemic flow ratio by Ir-191m angiography and oxymetry during cardiac catheterization; the correlation coefficient was 0.90. Radionuclide angiography with Ir-191m is a method with virtually no risk, rapid, accurate, and reproducible, and is ideally suited for the evaluation of left-to-right shunts in small children.

Angiography↗

PubMed1998

Magnetocardiographic pacemapping for nonfluoroscopic localization of intracardiac electrophysiology catheters.

The purpose of the study was to validate, in patients, the accuracy of magnetocardiography (MCG) for three-dimensional localization of an amagnetic catheter (AC) for multiple monophasic action potential (MAP) with a spatial resolution of 4 mm2. The AC was inserted in five patients after routine electrophysiological study. Four MAPs were simultaneously recorded to monitor the stability of endocardial contact of the AC during the MCG localization. MAP signals were band-pass filtered DC-500 Hz and digitized at 2 KHz. The position of the AC was also imaged by biplane fluoroscopy (XR), along with lead markers. MCG studies were performed with a multichannel SQUID system in the Helsinki BioMag shielded room. Current dipoles (5 mm; 10 mA), activated at the tip of the AC, were localized using the equivalent current dipole (ECD) model in patient-specific boundary element torso. The accuracy of the MCG localizations was evaluated by: (1) anatomic location of ECD in the MRI, (2) mismatch with XR. The AC was correctly localized in the right ventricle of all patients using MRI. The mean three-dimensional mismatch between XR and MCG localizations was 6 +/- 2 mm (beat-to-beat analysis). The co efficient of variation of three-dimensional localization of the AC was 1.37% and the coefficient of reproducibility was 2.6 mm. In patients, in the absence of arrhythmias, average local variation coefficients of right ventricular MAP duration at 50% and 90% of repolarization, were 7.4% and 3.1%, respectively. This study demonstrates that with adequate signal-to-noise ratio, MCG three-dimensional localizations are accurate and reproducible enough to provide nonfluoroscopy dependant multimodal imaging for high resolution endocardial mapping of monophasic action potentials.

Action Potentials↗

PubMed2006

Quantitative analysis of the variability of unilateral chewing movements in young adults.

Kinesiography can be used as a diagnostic tool in a dental clinic context. In the current study, a kinesiograph was used to detect and record the three-dimensional motion of the mandibular mid-incisor point during unilateral chewing as a function of time. The aim of the study was to quantify the within-subject short-term reproducibility of the kinesiographic recordings in normal, healthy subjects. Ten seconds of unilateral (right and left) gum chewing were recorded in 20 control subjects using computerized kinesiography. Each subject performed 18 chewing sequences (three repetitions x three sessions x two sides). Chewing cycle duration, volume, standardized depth and width, and the number of reversed cycles were calculated. Intraclass correlation coefficients (two-way random effects analysis of variance with interactions) and paired t-tests were used to compare sessions. For each subject and side, chewing variability was expressed as the coefficient of variation (percentage ratio of standard deviation to mean) of each variable. Mean left and right side mastications were computed over all sessions and subjects. For all the analyzed variables, larger variations between subjects (analysis of variance, p < 0.001) than between sessions were found, with intraclass correlation coefficients ranging between 0.432 (left side cycle duration) and 0.989 (right side standardized width). No systematic errors between the three measurement sessions were found for cycle volume and shape (paired t, p > 0.05). The highest between subjects/ between sessions variance ratios (up to 223.28) were found for cycle duration and shape. In all subjects, chewing cycle volume was very variable, with mean coefficients of variation up to 47% (left side in females). Cycle duration and standardized depth and width were more reproducible, with mean coefficients of variation up to 10% (duration), 14% (standardized width), and 18% (standardized depth). The spatial characteristics of gum chewing cycles had a large within-subject variability. The temporal and size-standardized (shape) characteristics were more consistent within subject. The results should allow selection of a set of relatively more consistent variables for the definition of normality and the comparison of patients.

Adult↗

PubMed1994

Human corpus callosum: a stable mathematical model of regional neuroanatomy.

The functional utility of regional parameters of the corpus callosum (CC) derived from factor analysis has been demonstrated in the rat and the human. In this study, we have utilized factor analysis to compare CC structure between two independent groups of human subjects. Tracings of the CC were taken from the midsagittal MRIs of two human samples consisting of 103 healthy volunteers and 146 neurological patients. CCs were digitized and factor analyses were performed on 99 widths, area, axis length, and perimeter. The factor structures of these two data sets were highly congruent except that one factor analysis yielded a seven-factor solution, whereas the factor analysis of the other subject population gave six factors. Further study determined that the six-factor structure could be attributed to the presence of non-consistent right-handed males whose wider CCs in the isthmus region biased the correlations. When CC parameters of consistent and non-consistent right-handed subjects were standardized, a seven-factor structure resulted. Reproducibility of the factor structure indicates that there are shared neuroanatomical characteristics of CC morphology among two disparate populations of humans in spite of variability in CC size due to sex, age, hand preference, and hand consistency.

Adolescent↗

PubMed1995

Hemispace asymmetries and laterality effects in arm positioning.

Hemispace asymmetries and laterality effects were examined on an arm positioning reproduction task. Sixteen male subjects were asked to reproduce both abductive and adductive positioning movements with the left or right arm within either the left or the right hemispace. Hemispace was manipulated using a 90 degrees head-rotation paradigm. A left hemispace advantage in positioning accuracy was predicted for both left and right arm movements on the grounds that the perceptual-motor control of positioning movements made in left hemispace is primarily mediated by the right hemisphere which is known to be advantageous for tasks which are spatial in nature (Heilman, Bowers, & Watson, 1984). No arm laterality effects were predicted to occur because the proximal musculature involved in the control of arm movements is innervated from both contralateral and ipsilateral cerebral hemispheres (Brinkman & Kuypers, 1973). Results showed that the predicted left hemispace advantage was evident for the right arm on the positioning variability measure alone, whereas it was absent for all other possible conditions on all error measures. Laterality (arm) effects were absent as predicted. The experiment also demonstrated a greater degradation of reproduction performance under the "crossed" arm-hemispace conditions than under the "uncrossed" conditions. A plausible explanation for the uncrossed advantage for the task is that under normal conditions, a single hemisphere is primarily responsible for both controlling the contralateral arm and directing attention to the contralateral hemispace, and consequently potential interhemispheric interference is minimized. A clear response bias effect in movement reproduction was also evident as a function of the direction of concurrent arm movement and head rotation. Arm movements made in the same direction as head rotation were systematically undershot in reproduction to a much greater degree than arm movements made in the opposite direction to head rotation.

Adolescent↗

PubMed1990

81mKr equilibrium radionuclide ventriculography for the assessment of right heart function.

Right heart 81mKr equilibrium radionuclide ventriculography was used to derive right ventricular ejection fraction (RVEF) in 12 healthy male volunteers. Anatomical lung subtraction using 99mTc-MAA perfusion scintigraphy was compared with conventional background correction and the effect of imaging projection on the techniques of image analysis evaluated. Both intra and inter observer variability were reduced by anatomical lung subtraction when compared to conventional background correction. In the right anterior oblique (RAO) projection, background corrected RVEF was lower than lung subtracted RVEF - 0.544 +/- 0.05 and 0.612 +/- 0.08 (mean +/- SD) (P less than 0.02). Lung subtracted RVEF in the anterior projection was lower than that with background correction (P less than 0.05) and lower than lung subtracted RVEF in the RAO projection (P less than 0.001). We conclude that optimal separation of right heart structures is achieved in the RAO projection and that reproducibility of the analytical technique is improved by anatomical lung subtraction.

Adult↗

PubMed1986

The effectiveness of CO2 laser and electromicrosurgery in adhesiolysis: a comparative study.

This study was undertaken to assess the relative effectiveness of the CO2 laser and electromicrosurgery in adhesiolysis. Intraperitoneal adhesions were produced in 44 female white rats by inflicting a standard and reproducible injury to the serosa of a specific area of the right uterine horn. At a second intervention, 2 weeks later, the adhesions formed by the initial injury were assessed and division of adhesions effected in a random manner, either with the use of the CO2 laser or with electromicrosurgery, adhering to accepted microsurgical techniques. At a third intervention, results were assessed. The results demonstrate that electromicrosurgery and the CO2 laser are equally effective for adhesiolysis in the rat model.

Animals↗

PubMed1996

Assessing the clinical utility of the magnetic stimulator for measuring response latencies in the laryngeal muscles.

Our purpose was to assess the use of magnetic stimulation for measuring conduction time of the recurrent and superior laryngeal nerves In 10 normal volunteers (7 male, 3 female). Subjects underwent laryngeal electromyography and magnetic stimulation of the vagus nerve bilaterally at the mastoid tip with a figure 8 coil. Mean muscle response latencies were measured and examined for consistent differences. Thyroarytenoid muscle response latencies were consistently longer than those in the cricothyroid muscle. Left thyroarytenoid muscle latencies were consistently longer than those on the right in agreement with bilateral asymmetry of these nerves. No appreciable differences were observed in cricothyroid muscle latencies when the right side was compared with the left. Results were consistent and reproducible within a broad range, but appreciable intersubject variability was observed. The limited sample size was unable to support a correlation with anthropometric variables, although an association was indicated. Magnetic stimulation with this technique has great potential for use in neurolaryngologic studies.

Adult↗

PubMed1998

Integrated MR imaging approach to valvular heart disease.

With development of cine and velocity encoded magnetic resonance imaging, it is now feasible to detect and quantify aortic and mitral stenosis and regurgitation accurately. In addition, magnetic resonance imaging has the capabilities to assess simultaneously left and right ventricular mass, volumes, and function precisely. The high accuracy and reproducibility of magnetic resonance imaging in quantification of regurgitation and ventricular function has the potential to provide improved monitoring of therapy and optimal timing of surgery in patients with valvular dysfunction. In comparison to echocardiography and angiography, some current limitations of magnetic resonance imaging to an integrated approach of valvular heart disease exist, which may be removed with future refinement of magnetic resonance imaging technology for cardiovascular imaging.

Heart Valve Diseases↗

PubMed1999

Experimental wound healing with electrical stimulation.

The effect of alternating current (AC) and direct current (DC) stimulation was studied on experimental pressure ulcer healing in a new monoplegic pig model. The study was conducted in 30 healthy young Hanford minipigs. The rate of wound healing, histology, vascularization, collagen formation, microbiology, perfusion, and the mechanical strength of the healed wounds were studied. Normal pigskin was compared to denervated control and denervated AC and DC stimulated healed skin. Hind limb denervation was by right unilateral extradural rhizotomies from the L2 to S1 nerve roots. Reproducible uniformly controlled Stage III or higher tissue ulcers were created. When compared to the control wounds, both the AC and DC stimulated wounds showed reduced healing time and increased perfusion in the early phases of healing. DC stimulation reduced the wound area more rapidly than AC, but AC stimulation reduced the wound volume more rapidly than DC. The electrical stimulation did not reduce the strength of the healing wounds below those of the nonstimulated controls. The applied current appears to orient new collagen formation even in the absence of neural influences.

Animals↗

PubMed2002

Importance of right and left atrial dilation and linear ablation for perpetuation of sustained atrial fibrillation.

INTRODUCTION: Atrial dilation associated with increasing atrial pressure plays an apparent role in the development of atrial fibrillation (AF). We characterized a new model of separate and biatrial dilation in the Langendorff-perfused rabbit heart. The aim of this study was to examine if sustained AF in this model (1) would be inducible by separate right atrial (RA) and left atrial (LA) dilation; (2) would be reproducibly inducible at the same pressure level; and (3) could be suppressed by RA, LA, or biatrial ablation. METHODS AND RESULTS: Intra-atrial pressure was increased stepwise in the RA (n = 13), LA (n = 12), or both atria (n = 25) until sustained AF could be induced or a pressure of 20 cm H2O was reached. The stimulation protocol was repeated once in RA and LA dilation (n = 9) and three times in biatrial dilation (n = 7). Then, RA orifices (superior and inferior caval veins, tricuspid valve annulus, and foramen ovale) or LA orifices (pulmonary veins, mitral valve annulus, and foramen ovale) were connected by radiofrequency (RF) lesions. Sustained AF was rendered inducible in 100% of hearts with biatrial dilation, but in only 92% of hearts with RA dilation and 67% with LA dilation. Inducibility of sustained AF was reproducible. Under biatrial dilation, not RA ablation (0/10 hearts; P = NS) but LA ablation (4/11 hearts; P < 0.05) and biatrial ablation (16/21; P < 0.01) reduced the inducibility of sustained AF. CONCLUSION: The inducibility of sustained AF due to increased intra-atrial pressure differs between the RA and LA. LA and biatrial lesions, not RA RF lesions, reduce the ability to perpetuate sustained AF.

Animals↗

PubMed1991

Right ventricular function assessed by thermodilution technique during apnea and mechanical ventilation.

OBJECTIVES: To evaluate strategies for thermodilution-based measurement of cardiac output and right ventricular (RV) ejection fraction and to assess the effects of controlled mechanical ventilation in patients. Furthermore, to compare strategy-associated reproducibility with reference values obtained during long-term apnea. DESIGN: Crossover trial in patients; reference values from apneic animals. SETTING: University ICU and physiology laboratory. PATIENTS: Six consecutive male ICU patients (48 to 70 yrs) after major abdominal vascular surgery. ANIMALS: two adult female sheep. INTERVENTIONS: Three ventilatory rates (8, 16, and 24 cycles/min) and 15-sec periods of apnea were selected for measurements in patients. In animals, continuous apnea was achieved with extracorporeal CO2 removal and apneic oxygenation. MEASUREMENTS: Measurements were performed using an appropriate pulmonary artery catheter and an ejection fraction/cardiac output computer prototype. The thermal indicator was injected automatically at four defined points of the ventilatory cycle, but triggered manually during apnea. MAIN RESULTS: At 8 cycles/min, there was a wide mean range of cyclic variable modulation, with a coefficient of variation of 11.6% and 23.2% for cardiac output and RV ejection fraction, respectively. Allowing for ventilatory phase or changing from 8 to 16 cycles/min reduced errors by half. Combining both procedures resulted in a coefficient of variation of 4.7% and 6.6% for cardiac output and RV ejection fraction, respectively. The best coefficient of variation values obtained during 15 secs of apnea in patients approached those variations in experimental apnea (coefficient of variation of 2.1% and 4.5% for cardiac output and RV ejection fraction, respectively). CONCLUSIONS: At low ventilatory rates, best results are achieved by averaging four phase-selected measurements. One-point measurements were less accurate and random point measurements less reproducible.

Aged↗

PubMed2004

Wolff-Parkinson-White syndrome concomitant with asymptomatic Brugada syndrome.

A 29-year-old man was referred for electrophysiological testing and radiofrequency ablation because of repeated episodes of palpitation over 2 years. A 12-lead electrocardiogram during sinus rhythm showed manifest Wolff-Parkinson-White syndrome and during palpitation showed narrow QRS tachycardia at a rate of 213 beats/min. Following successful radiofrequency ablation of the left anterolateral accessory pathway, sustained atrial fibrillation was induced by atrial extrastimulation. Cibenzoline (2 mg/kg body weight) was injected to terminate atrial fibrillation. ST-T segment elevation in the right precordial leads was observed following cibenzoline administration. Ventricular fibrillation was reproducibly induced by ventricular extrastimuli (S1: 600 ms, S2: 220 ms, S3: 210 ms).

Adult↗

PubMed2000

Coronary artery spasm induced by carotid sinus massage.

A 60 year old man with a history of frequent episodes of chest pain and dizziness was referred for evaluation of coronary artery disease. He had no significant coronary artery stenosis at baseline coronary angiography. A carotid sinus massage was performed for evaluation of carotid sinus hypersensitivity in the patient. Both heart rate and blood pressure decreased a little, and returned to baseline level immediately after carotid sinus massage. However, 2.5 minutes after carotid sinus massage, ECG showed ST segment elevation in leads II, III, and aVF. Four minutes after carotid sinus massage, he had chest pain with a progressive elevation in the ST segment in the same leads, when he had 99% focal spasm in the right coronary artery. The vasospasm induced by carotid sinus massage was reproducible over several minutes and resolved spontaneously. Coronary artery spasm may be provoked by the enhanced vagal activation due to carotid sinus massage.

Carotid Sinus↗

PubMed1996

Heart disease: functional evaluation with MR imaging.

Diagnosis of cardiovascular disease requires precise assessment of both morphology and function. Nearly all aspects of cardiovascular function can be quantified with fast magnetic resonance (MR) imaging techniques. Conventional and breath-hold cine MR imaging can provide precise and highly reproducible measurements of global and regional function of the left and right ventricles. Velocity-encoded cine (VEC) MR imaging provides measurements of blood flow in the heart and great vessels. Contrast-prepared fast gradient-echo sequences can be used to monitor the first-pass dynamics of contrast media, thus defining selective regional myocardial perfusion. Recently, the feasibility of using breath-hold VEC MR imaging to measure flow velocity in native coronary arteries and coronary revascularization conduits has been shown. This will most likely provide a noninvasive method for testing coronary vasodilator reserve and may emerge as a new method for detecting asymptomatic coronary artery disease.

Coronary Circulation↗

PubMed2005

Catheter-based antegrade intracoronary viral gene delivery with coronary venous blockade.

The purpose of this study is to evaluate the feasibility of percutaneous antegrade myocardial gene transfer (PAMGT). A consistent and safe technique for in vivo gene transfer is required for clinical application of myocardial gene therapy. PAMGT with concomitant coronary venous blockade was performed in 12 swine. The myocardium was preconditioned with 1 min of occlusion of the left anterior descending and left circumflex arteries. The anterior interventricular vein was occluded during left anterior descending artery delivery, and the great cardiac vein at the entrance of the middle cardiac vein was occluded during left circumflex artery delivery. With arterial and venous balloons inflated (3 min) and after adenosine (25 mug) injection, PAMGT was performed by antegrade injection of an adenoviral solution (1 ml of 10(11) plaque-forming units in each coronary artery) carrying beta-galactosidase or saline through the center lumen of the angioplasty balloon. In one set of animals, PAMGT was performed with selective coronary vein blockade (n = 9); in another set of animals, PAMGT was performed without coronary vein blockade (n = 5). At 1 wk after gene delivery, the animals were killed. Quantitative beta-galactosidase analysis was performed in the left and right ventricular walls. PAMGT was successfully performed in all animals with and without concomitant occlusion of the coronary veins. Quantitative beta-galactosidase analysis showed that PAMGT with coronary blockade was superior to PAMGT without coronary blockade. beta-Galactosidase activity increased significantly in the beta-galactosidase group compared with the saline group: 1.34 +/- 0.18 vs. 0.81 +/- 0.1 ng (P </= 0.01) in the left ventricular wall and 0.91 +/- 0.1 vs. 0.66 +/- 0.07 ng (P </= 0.05) in the right ventricular wall. PAMGT with selective coronary venous blockade is feasible, reproducible, and safely achieved in a large-animal model.

Adenoviridae↗

PubMed1980

The reproducibility of two methods of studying granulopoiesis: agar culture and labelling index.

The overall reproducibility of two methods of studying granulopoiesis has been investigated, i.e. study of the granulocytic progenitor cells by the agar-culture technique and study of the myeloblast labelling index by autoradiography. The results obtained indicate that these two methods are reproducible for each step involved, from the time of marrow sampling right through to the final interpretation of the results.

Agar↗

PubMed1999

In vivo human brachial artery elastic mechanics: effects of smooth muscle relaxation.

BACKGROUND: The effects of smooth muscle relaxation on arterial wall mechanics are controversial. We used a new, in vivo, noninvasive technique to measure brachial artery wall mechanics under baseline conditions and following smooth muscle relaxation with nitroglycerin (NTG). METHODS AND RESULTS: Eight healthy, normal subjects (6 male, 2 female; age 30+/-3.1 years) participated in the study. The nondominant brachial artery was imaged through a water-filled blood pressure cuff using an external ultrasound wall-tracking system at baseline and following 0.4 mg sublingual NTG. Simultaneous radial artery pressure waveforms were recorded by tonometry. Transmural pressure (TP) was reduced by increasing water pressure in the cuff. Brachial artery area, unstressed area, compliance, stress, strain, incremental elastic modulus (Einc), and pulse wave velocity (PWV) were measured over a TP range from 0 to 100 mm Hg. Baseline area versus TP curves generated 30 minutes apart were not significantly different. NTG significantly shifted area versus TP (P<0.0001) and compliance versus TP (P<0.001) curves upward, whereas the Einc versus TP (P<0.05) and PWV versus TP (P<0. 01) curves were shifted downward. NTG also significantly shifted stress versus strain (P<0.01) and Einc versus strain (P<0.01) curves to the right. CONCLUSIONS: We conclude that brachial artery elastic mechanics can be reproducibly measured over a wide range of TP and smooth muscle tone using a new noninvasive ultrasound technique. Smooth muscle relaxation with NTG increases isobaric compliance and decreases isobaric Einc and PWV in the human brachial artery.

Adult↗