PubMed Health⌕ Search

Biomedical subjects

A Kenny

Publications and source records attributed to A Kenny.

At least 19 recordsLinked to original sources
PubMed2003

Direct monitoring of soil and water nitrate by FTIR based FEWS or membrane systems.

The development of silver halide fibers that transmit with minimal loss into the mid-IR (MIR) paved the way to their successful utilization as effective ATR (Attenuated Total Reflectance) elements, promoting the implementation of Fiberoptic Evanescent Wave Spectroscopy (FEWS) for direct monitoring of nitrate in environmental systems. Samples containing nitrate in water, soil extracts, and pastes were used for the determination of nitrate concentration with a common ATR ZnSe crystal and with silver halide fibers (FEWS). Spectra of soil pastes and suspensions and those of phosphate, carbonate, sulfate, ammonium, and soil organic constituents were collected to study possible interference with nitrate determination. The standard error of estimate (SEE) and R2 values obtained with flat fibers, using the simple single-point correlation method, were superior to those obtained for cylindrical FEWS and ZnSe ATR crystals in pure water. A significant improvement in the SEE and R2 was achieved in most soil pastes by applying the simple mode of the Cross Correlation method. Direct transmission of MIR radiation through ion-exchange membranes, partially loaded with nitrate or carbonate, was found an effective alternative for MIR-FTIR determination of these ions. Further development and modification of the FEWS devices should allow in-situ and online determination of nitrate in soil and environmental systems.

Agrochemicals↗
PubMed2002

Surface integration of velocity vectors from 3D digital colour Doppler: an angle independent method for laminar flow measurements.

BACKGROUND: The study was designed to test the angle independence of a dynamic three-dimensional digital colour Doppler method for laminar flow measurement. The technique acquired three-dimensional data by rotational acquisition and used surface integration of Doppler vector velocities and flow areas in time and space for flow computation. METHOD: A series of pulsatile flows (peak flow 55-180 ml/s) through a curved tube were studied with reference flow rates obtained using an ultrasonic flow meter. Colour Doppler imaging was performed at three angles to the direction of flow (20 degrees, 30 degrees, 40 degrees), using a multiplane transoesophageal probe controlled by an ATL HDI5000 system. Integration of digital velocity vectors over a curved three-dimensional surface across the tube for each of the 11 flow rates at each angle was performed off-line to compute peak flow. RESULTS: Peak flow rates correlated closely (r=0.99) with the flow meter with the mean difference from the reference being -0.8+/-2 x 4 ml/s, 0.9+/-2.6 ml/s, 1.0+/-2 x 3 ml/s for 20 degrees, 30 degrees and 40 degrees respectively. Comparison of the three angle groups showed no significant differences (P=0.15, ANOVA). When sampled obliquely, the flow area on the curved surface increased while the velocities measured decreased. CONCLUSION: Surface integration of velocity vectors to compute three-dimensional Doppler flow data is less angle dependent than conventional Doppler methods.

Blood Flow Velocity↗
PubMed2002

Dobutamine stress echocardiography for the detection of myocardial viability in patients with left ventricular dysfunction taking beta blockers: accuracy and optimal dose.

OBJECTIVE: To assess the accuracy of dobutamine stress echocardiography (DSE) and the optimal dose of dobutamine to detect myocardial viability in patients with ischaemic left ventricular (LV) dysfunction who are taking beta blockers, using the recovery of function six months artery revascularisation as the benchmark. PATIENTS: 17 patients with ischaemic LV dysfunction (ejection fraction < 40%) and chronic treatment with beta blockers scheduled to undergo surgical revascularisation. SETTING: Regional cardiothoracic centre. METHODS: All patients underwent DSE one week before and resting echocardiography six months after revascularisation. A wall motion score was assigned to each segment for each dobutamine infusion stage, using the standard 16 segment model of the left ventricle. The accuracy of DSE to predict recovery of resting segmental function was calculated for low dose (5 and 10 microg/kg/min) and for a full protocol of dobutamine infusion (5 to 40 microg/kg/min). RESULTS: Of the 272 segments studied, 158 (58%) were dysfunctional at rest, of which 79 (50%) improved at DSE and 74 (47%) recovered resting function after revascularisation. Analysis of results with a low dose showed a significantly lower sensitivity and negative predictive value than with a full protocol (47% v 81%, p < 0.001 and 65% v 82%, p < 0.05, respectively). The accuracy in the full protocol analysis was comparable with that reported in patients no longer taking beta blockers but was significantly lower than that in the low dose analysis (78% v 66%, p < 0.001). CONCLUSIONS: Findings suggest that beta blocker withdrawal is not necessary before DSE when viability is the clinical information in question. However, a completed protocol with continuous image recording is required to detect the full extent of viability.

Adrenergic beta-Antagonists↗
PubMed2001

Validation of a digital color Doppler flow measurement method for pulmonary regurgitant volumes and regurgitant fractions in an in vitro model and in a chronic animal model of postoperative repaired tetralogy of Fallot.

OBJECTIVES: The purpose of this study was to validate a digital color Doppler (DCD) automated cardiac flow measurement method for quantifying pulmonary regurgitation (PR) in an in vitro and a chronic animal model of the right ventricular outflow tract of postoperative tetralogy of Fallot (TOF). BACKGROUND: There has been no reliable ultrasound method that can accurately quantitate PR. METHODS: We developed an in vitro model of mild pulmonary stenosis and wide-open PR that mimics the patterns of flow seen in patients with postoperative TOF. Thirteen different forward and regurgitant stroke volumes (RSVs) across the noncircular shaped cross-sectional outflow tract flow area were estimated using the DCD method in two orthogonal planes. In six sheep with surgically created PR, 24 different hemodynamic states with PR strictly quantified by electromagnetic probes were also studied. RESULTS: The RSVs and regurgitant fractions (RFs) obtained by the DCD method using average values from two orthogonal planes correlated well with reference values (RSV: r = 0.99, mean difference = 0.02 +/- 0.39 ml/beat for in vitro model; r = 0.97, mean differences = 1.79 +/- 1.84 ml/beat for animal model, RF: r = 0.98, mean difference = -1.10 +/- 4.34% for in vitro model; r = 0.94, mean difference = 2.73 +/- 6.75% for animal model). However, the DCD method using a single plane had limited accuracy for estimating pulmonary RFs and RSVs. CONCLUSIONS: The DCD method using average values from two orthogonal planes provides accurate estimation of RSVs and RFs and should have clinical importance for serially quantifying PR in patients with postoperative TOF.

Animals↗
PubMed2001

Impact of harmonic imaging and transducer frequency on 'ventricular volume' measurements using real-time three-dimensional echocardiography: studies in an in vitro model.

AIMS: Harmonic imaging has increased the yield of quantifiable scans in two-dimensional echocardiography. Although real-time three-dimensional echocardiography avoids geometric assumptions in volume analysis, accurate measurement can be limited by image quality. This study compared volumes from a balloon model mimicking the left ventricle, scanned with and without harmonic imaging, using real time three-dimensional echocardiography. METHODS: Two balloons separated by ultrasound gel were suspended in a water bath. To mimic different chamber volumes, 12 volumes of water within the inner balloon (40-180ml) were scanned using a 3.5MHz probe at fundamental frequency and using a 2.5MHz probe with and without harmonic imaging. RESULTS: Scanning at 3.5MHz, the long axis (B) scans did not significantly underestimate the balloon volume but the 'short axis' (C) scans did (mean difference from actual volumes -0.7-1.4ml, P=0.14 - 3.9 +/- 1.2 ml,P < 0.0001 for B and C scans, respectively). Scanning at 2.5MHz both B and C scans significantly underestimated even more the true volume, C scans to a greater extent (mean difference -6.9 +/- 2.4ml and -11.2 +/- 4.0ml for B and C scans respectively,P < 0.0001 in both cases). However with harmonic imaging, transmitting at 1.7MHz and receiving at 2-4MHz, there was no significant difference of either B or C scans from the reference values (mean difference of B scans -1.2 +/- 1.9ml, P=0.06 and C scans -0.6 +/- 2.2ml, P=0.4). CONCLUSION: The enhanced resolution provided by harmonic imaging improves accuracy of volume analysis by real-time three-dimensional echocardiography.

Analysis of Variance↗
PubMed2001

Quantification of aortic regurgitation by real-time 3-dimensional echocardiography in a chronic animal model: computation of aortic regurgitant volume as the difference between left and right ventricular stroke volumes.

BACKGROUND: The accuracy of conventional 2-dimensional echocardiographic and Doppler techniques for the quantification of valvular regurgitation remains controversial. In this study, we examined the ability of real-time 3-dimensional (RT3D) echocardiography to quantify aortic regurgitation by computing aortic regurgitant volume as the difference between 3D echocardiographic-determined left and right ventricular stroke volumes in a chronic animal model. METHODS: Three to 6 months before the study, 6 sheep underwent surgical incision of one aortic valve cusp to create aortic regurgitation. During the subsequent open chest study session, a total of 25 different steady-state hemodynamic conditions were examined. Electromagnetic (EM) flow probes were placed around the main pulmonary artery and ascending aorta and balanced against each other to provide reference right and left ventricular stroke volume (RVSV and LVSV) data. RT3D imaging was performed by epicardial placement of a matrix array transducer on the volumetric ultrasound system, originally developed at the Duke University Center for Emerging Cardiovascular Technology. During each hemodynamic steady state, the left and right ventricles were scanned in rapid succession and digitized image loops stored for subsequent measurement of end-diastolic and end-systolic volumes. Left and right ventricular stroke volumes and aortic regurgitant volumes were then calculated and compared with reference EM-derived values. RESULTS: There was good correlation between RT3D left and right ventricular stroke volumes and reference data (r = 0.83, y = 0.94x + 2.6, SEE = 9.86 mL and r = 0.63, y = 0.8x - 1.0, SEE = 5.37 mL, respectively). The resulting correlation between 3D- and EM-derived aortic regurgitant volumes was at an intermediate level between that for LVSV and that for RVSV (r = 0.80, y = 0.88x + 7.9, SEE = 10.48 mL). RT3D tended to underestimate RVSV (mean difference -4.7 +/- 5.4 mL per beat, compared with -0.03 +/- 9.7 mL per beat for the left ventricle). There was therefore a small overestimation of aortic regurgitant volume (4.7 +/- 10.4 mL per beat). CONCLUSION: Quantification of aortic regurgitation through the computation of ventricular stroke volumes by RT3D is feasible and shows good correlation with reference flow data. This method should also be applicable to the quantification of other valvular lesions or single site intracardiac shunts where a difference between right and left ventricular cavity stroke volumes is produced.

Animals↗
PubMed2000

Differential diagnosis and secondary causes of osteoporosis.

Secondary osteoporosis refers to osteoporosis in which an underlying cause or factor other than those attributable to the postmenopausal state or aging can be identified. Primary, or idiopathic, osteoporosis implies that a secondary cause cannot be found. Secondary osteoporosis occurs not only in postmenopausal women but also in men and premenopausal women. In series reported from specialized centers, as many as 30% of postmenopausal women and 50% to 80% of men have an identifiable secondary cause of osteoporosis, although the frequency of secondary osteoporosis is probably much lower in the general population. In assessing the patient with osteoporosis, it is important to look for secondary causes and aggravating factors that are reversible and amenable to therapy. In addition to secondary forms, 2 metabolic bone diseases, osteomalacia and primary hyperparathyroidism, can mimic or aggravate osteoporosis. This paper will summarize the differential diagnosis and management of osteoporosis, osteomalacia, and hyperparathyroidism and review the most common causes of secondary osteoporosis.

Adult↗
PubMed2000

Osteoporosis in older men.

Historically, the focus in osteoporosis has been on postmenopausal women. In the past few years, information about osteoporosis in other populations, including men, has begun to emerge. Although less common in older men, osteoporosis nonetheless represents a major health concern. Approximately 30% of hip fractures worldwide occur in men, resulting in significant mortality and loss of independence. The incidence of osteoporotic fractures in men is increasing. The reason for this is unclear, but improvement in longevity and better management of other chronic diseases most likely play a role. Two recent studies have addressed the question of fracture risk in men past middle age and have estimated that men > 50 years of age have a 19% to 25% lifelong risk of osteoporotic fracture. Mortality is higher following hip fracture and pain is more intense in men than in women following severe vertebral fracture.

Administration, Cutaneous↗
PubMed2000

Untangling the Web... barriers and benefits for nurse education... an Australian perspective.

The Internet... a Web of information technology. The potential exists now and increasingly in the future to use this technology to deliver widely distributed, creative, innovative learning to students across vast distances and at times which suit individual needs. The implications of this technology for nurse education, and indeed health care in general, are exciting. The technology is growing at such a vast rate that it would be easy to blindly accept it and promote its use. However, there is a need to stop and consider some of the practical barriers to the use of this technology, particularly for nursing education.

Attitude of Health Personnel↗
PubMed2000

A digital 3-dimensional method for computing great artery flows: in vitro validation studies.

BACKGROUND: Conventional 2-dimensional Doppler large vessels are prone to inaccuracy. Three-dimensional (3D) volume imaging provides the opportunity to make cross-sectional flow calculations through digital spatiotemporal integration of flow velocity, area, and profile. METHODS: A new digital 3D color Doppler reconstruction method was used to generate radially acquired flow data sets. Raw scanline data with digital velocity assignments, obtained by scanning parallel to flow, were transferred from a specially programmed but otherwise conventional ultrasonographic system, which controlled a multiplane transesophageal probe, to a computer workstation via an Ethernet link for assimilation into color 3D data sets. This configuration was used to study 20 pulsatile laminar flows (stroke volumes 30 to 70 mL and peak flow rates 65 to 205 mL/s) in a curved tube model with an oval cross-sectional geometry. After generation of the color 3D data set, flow velocity values from cross sections perpendicular to the tubes were analyzed to determine flow rate and stroke volume. RESULTS: The flows from 3D digital velocity profiles showed close correlation with peak instantaneous flow rates (r = 0.99, y = 1.01x-0.9, standard error of estimate 4.1 mL/s). When interpreted with pulsed wave Doppler data obtained through the cardiac cycle, they also allowed computation of stroke volume (r = 0.98, y = 1.44x-2.5, standard error of estimate 3.8 mL). CONCLUSION: The ability to compute laminar flows from 3D digital data sets obtained parallel to the direction of flow and without the need for geometric assumptions represents an important opportunity for and advantage of 3D color Doppler echocardiography.

Coronary Vessels↗
PubMed2000

Comparison of ventricular volume and mass measurements from B- and C-scan images with the use of real-time 3-dimensional echocardiography: studies in an in vitro model.

BACKGROUND: Real-time 3-dimensional (3D) echocardiography avoids geometric assumptions in volume analysis and permits immediate visualization in any plane without the need for cardiac or respiratory gating or computation time. This study compared the accuracy of volume and mass assessments between standard long-axis (B-scan) and short-axis (C-scan) views in a simplified but quantifiable left ventricular phantom. METHODS AND RESULTS: The model comprised an inner balloon within an outer balloon separated by ultrasonographic gel. First, to mimic different chamber volumes, 12 volumes (40 to 180 mL) of water within the inner balloon were scanned with a real-time 3D system. Second, 10 volumes (80 to 170 mL) of gel were inserted between the balloons to mimic varying cardiac mass, and the gel volume space (mass) was calculated by subtracting the inner from the outer balloon volume. "Chamber" and "mass" measurements for both B and C scans correlated closely with the actual values (r = 0.99). However, chamber volumes from C scans were consistently less than B-scan values (mean difference from reference for C scans: -5.2 +/- 1.2 mL, P <.0001; for the 2 orthogonal B scans: 0.03 +/- 1.4 mL and -0.9 +/- 1.5 mL, respectively, P = NS). Similarly, for gel volume measurements, B-scan results were closer to actual mass volumes (mean difference 0. 3 +/- 2.5 and 1.7 +/- 2.9 mL) than those of C scans, which tended to underestimate (-4.5 +/- 2.5 mL, P <.0001). CONCLUSION: Our study suggests that real-time 3D echocardiography should provide an accurate means of determining chamber volumes and cardiac mass. However, measurements performed from B-scan views may be closer to the actual values than those from C-scan views, presumably since they are less highly influenced by distortions related to lateral resolution.

Cardiac Volume↗
PubMed2000

Enhanced left ventricular endocardial border delineation with an intravenous injection of SonoVue, a new echocardiographic contrast agent: A European multicenter study.

The safety and efficacy of SonoVue (also referred to as BR1), a new contrast agent for delineating endocardial border of the left ventricle after intravenous administration, was assessed. Two hundred and eighteen patients with suspected coronary artery disease undergoing fundamental echocardiography for the assessment of left ventricle were enrolled in a prospective multicenter, single blind, cross-over study with random sequence allocation of four different doses of SonoVue. Endocardial border definition in the apical and parasternal views was scored as 0 = not visible, 1 = barely visible, and 2 = well visualized before and after contrast enhancement. Analysis was performed by two pairs of off-site observers. Safety of SonoVue was also assessed. Results of our study indicated that the mean improvements in the endocardial border visualization score were as follows: 3.1 +/- 7.8 (95% CI, 2.5 and 3.7) for 0.5 ml, 3.4 +/- 8.0 (95% CI, 2.8 and 4.0) for 1 ml, 3.4 +/- 7.9 (95% CI, 2.8 and 4.0) for 2 ml, and 3.7 +/- 8.0 (95% CI, 3.1 and 4.3) for 4 ml (P < 0.05 for all doses from baseline). Changes from baseline in endocardial visualization scores were also seen in the apical views (P < 0.05) and they were dose-dependent (P < 0.001). Similar enhancements of endocardial visualization scores were observed in the apical views in patients with suboptimal baseline echocardiographic images. Diagnostic confidence for assigning a score and image quality also were significantly better following contrast enhancement. No significant changes in the laboratory parameters and vital signs were noted following contrast enhancement, and the side effects were minimal. It was concluded that SonoVue is safe and effective in delineating endocardial border, including in patients with suboptimal baseline images.

Aged↗
PubMed2000

Hospital outpatient and emergency services in rural Victoria.

Outpatient and emergency services in rural hospitals have rarely been studied. This paper analyses routinely collected data, together with data from a survey of hospitals, to provide a picture of these services in Victorian public hospitals. The larger rural hospitals provide the bulk of rural outpatients and emergency services, particularly so for medical outpatients. Cost per service varies with the size of the hospital, possibly reflecting differences in complexity. Funding policies for rural hospital outpatient and emergency services should be sufficiently flexible to take into account the differences between rural hospitals.

Data Interpretation, Statistical↗