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Biomedical subjects

M O'Sullivan

Publications and source records attributed to M O'Sullivan.

At least 19 recordsLinked to original sources
PubMed1995

Evaluation of mitral stenosis with velocity-encoded cine-magnetic resonance imaging.

Velocity-encoded cine-magnetic resonance imaging (VEC-MRI) is a new method for quantitation of blood flow with the potential to measure high-velocity jets across stenotic valves. The objective of this study was to evaluate the ability of VEC-MRI to measure transmitral velocity in patients with mitral stenosis. Sixteen patients with known mitral stenosis were studied. A 1.5 Tesla superconducting magnet was used to obtain velocity-encoded images in the left ventricular short-axis plane. Images were obtained throughout the cardiac cycle at 3 consecutive slices beginning proximal to the mitral coaptation point. To determine the optimal slice thickness for MRI imaging, both 10 mm and 5 mm thicknesses were used. Echocardiography including continuous-wave Doppler was performed on every patient within 2 hours of MRI imaging. Peak velocity was determined for both VEC-MRI and Doppler-echo images. Two observers independently measured the VEC-MRI mitral inflow velocities. Of the 16 patients, imaged data were incomplete in only 1 study, and all images were adequate for analysis. Strong correlations were found for measurements of mitral valve gradient for both 10 mm (peak r = 0.89, mean r = 0.84) and 5 mm (peak r = 0.82, mean r = 0.95) slice thicknesses. Measurements of peak velocity with VEC-MRI (10 mm) agreed well with Doppler: mean 1.46 m/s, mean of differences (Doppler MRI) 0.38 m/s, standard deviation of differences 0.2 m/s. These findings suggest that VEC-MRI can noninvasively determine the severity of mitral stenosis.

Adult↗
PubMed1995

Quantitative comparison of asbestos and talc bodies in an individual with mixed exposure.

Tissue from an individual with a history of exposure to asbestos and other dust was referred for particulate analysis. The digested material was reviewed by light microscopy to establish the numbers of ferruginous bodies per gram of tissue. Typical asbestos bodies were found at levels consistent with occupational exposure. A second type of elongated ferruginous body was formed on a thicker transparent core which suggested the minerals were sheet silicates. The number of ferruginous bodies with nonasbestos cores was over four times the number of asbestos cored ferruginous bodies. Electron microscopy was used to confirm the core composition of both populations and also to establish the levels of uncoated fibers. The nonasbestos ferruginous bodies were predominantly formed on talc.

Adenocarcinoma↗
PubMed1995

Comparative induction of cytochrome P4504A in rat hepatocyte culture by the peroxisome proliferators, bifonazole and clofibrate.

1. The influence of imidazole and triazole antifungal drugs on cytochrome P450 levels in male Wistar primary rat hepatocyte culture for 70 h has been investigated and compared with clofibrate. 2. Bifonazole, clotrimazole, geniconazole clofibrate induced total P450 in hepatocytes, whereas itraconazole, miconazole and UK-47,265 did not. 3. When the CYP4A subfamily was examined, only bifonazole and clofibrate induced CYP4A as assessed by both Western blot analysis and the 11- and 12-hydroxylation of lauric acid. 4. By analysis of concentration-response curves in hepatocyte culture, bifonazole was 160 and 40 times more potent than clofibrate for induction of the 11- and 12-hydroxylation of lauric acid respectively. 5. Taken collectively, our data have identified bifonazole as a relatively potent, non-carboxylate inducer of CYP4A and the mechanism of induction and specificity of this azole is discussed.

Animals↗
PubMed1995

Psychosocial issues in breast cancer. Helping patients get the support they need.

Patients are becoming increasingly involved in making informed choices regarding their care. However, in the case of breast cancer, more than medical treatment of a body part is at stake. The breast is an important cultural symbol of femininity and an intimate part of the patient's self-esteem. The disease and its treatment may cause ongoing sadness, fear, anxiety, and anger. Primary care physicians, because of their close relationship with patients, are often in a position to notice when natural and reasonable emotional reactions go too far or last too long. Sensitive support and education of patients who are trying to choose a treatment method may minimize anxiety. Formal programs, such as the American Cancer Society's Reach to Recovery and Look Good... Feel Better, can be very supportive. For interested patients, support groups provide a chance to freely express their thoughts and feelings. However, not all women wish to participate in programs and groups. In some cases, careful listening on the part of the primary care physician is the most powerful intervention.

Adaptation, Psychological↗
PubMed1995

Myocardial infarction in a rural hospital.

Little is known of the outcome of myocardial infarction in patients managed in regional hospitals, where investigational and therapeutic modalities may have limited availability. Policies in place in the Intensive Care Unit of Wimmera Base Hospital for the management of myocardial infarction are designed to ensure that current 'best practice' is followed where possible. In order to audit our practices, and to ensure that these practices lead to patient outcomes similar to those published in cardiological literature, we performed a case note audit of patients admitted with myocardial infarction. We were keen to assess the risk factors of our patients, as it has been our impression that most patients with myocardial infarction have risk factors for ischaemic heart disease. Over a three year period (1991 to 1994) 88 persons with diagnosis of myocardial infarction were discharged from the intensive care unit. The in-hospital and 30 day mortality rates were 7.95%.

Aged↗
PubMed1994

Quantification of mitral regurgitation by velocity-encoded cine nuclear magnetic resonance imaging.

OBJECTIVES: The feasibility of velocity-encoded cine nuclear magnetic resonance (NMR) imaging to measure regurgitant volume and regurgitant fraction in patients with mitral regurgitation was evaluated. BACKGROUND: Velocity-encoded cine NMR imaging has been reported to provide accurate measurement of the volume of blood flow in the ascending aorta and through the mitral annulus. Therefore, we hypothesized that the difference between mitral inflow and aortic systolic flow provides the regurgitant volume in the setting of mitral regurgitation. METHODS: Using velocity-encoded cine NMR imaging at a magnet field strength of 1.5 T and color Doppler echocardiography, 19 patients with isolated mitral regurgitation and 10 normal subjects were studied. Velocity-encoded cine NMR images were acquired in the short-axis plane of the ascending aorta and from the short-axis plane of the left ventricle at the level of the mitral annulus. Two independent observers measured the ascending aortic flow volume and left ventricular inflow volume to calculate the regurgitant volume as the difference between left ventricular inflow volume and aortic flow volume, and the regurgitant fraction was calculated. Using accepted criteria of color flow Doppler imaging and spectral analysis, the severity of mitral regurgitation was qualitatively graded as mild, moderate or severe and compared with regurgitant volume and regurgitant fraction, as determined by velocity-encoded cine NMR imaging. RESULTS: In normal subjects the regurgitant volume was -6 +/- 345 ml/min (mean +/- SD). In patients with mild, moderate and severe mitral regurgitation, the regurgitant volume was 156 +/- 203, 1,384 +/- 437 and 4,763 +/- 2,449 ml/min, respectively. In normal subjects the regurgitant fraction was 0.7 +/- 6.1%. In patients with mild, moderate and severe mitral regurgitation, the regurgitant fraction was 3.1 +/- 3.4%, 24.5 +/- 8.9% and 48.6 +/- 7.6%, respectively. The regurgitant fraction correlated well with the echocardiographic severity of mitral regurgitation (r = 0.87). Interobserver reproducibilities for regurgitant volume and regurgitant fraction were excellent (r = 0.99, SEE = 238 ml; r = 0.98, SEE = 4.1%, respectively). CONCLUSIONS: These findings suggest that velocity-encoded NMR imaging can be used to estimate regurgitant volume and regurgitant fraction in patients with mitral regurgitation and can discriminate patients with moderate or severe mitral regurgitation from normal subjects and patients with mild regurgitation. It may be useful for monitoring the effect of therapy intended to reduce the severity of mitral regurgitation.

Adult↗
PubMed1994

Evaluation of the optimal hand-scrub duration prior to total hip arthroplasty.

Orthopaedic surgeons in many major arthroplasty centres advocate the use of a prolonged surgical hand-scrub prior to total joint replacement. In this study we evaluated the antimicrobial efficacy of a 5 compared with a 10 min scrub before both long (> 90 min) and short (< 90 min) operations for total hip arthroplasty. Surgical hand disinfection was performed on one occasion for 5 min and on a second for 10 min by 41 surgeons and theatre nurses using 4% chlorhexidine gluconate as a detergent formulation ('Hibiscrub', ICI Pharmaceuticals). None of the subjects had previously scrubbed on the day of each test. Bacterial colony counts on the fingers were measured using the method described by Rotter (vide infra) before scrubbing, immediately after scrubbing, and at the end of each operation. Our results showed that for arthroplasty procedures lasting less than 90 min (35 operations) a 5 min hand-scrub was equally as effective as one of 10 min. However, following longer procedures (36 operations) colony counts were significantly higher on subjects who had scrubbed for 10 min than on those who only scrubbed for 5 (P < 0.05, Mann-Whitney U-Test). This study suggests that the practice of a prolonged scrub before total joint replacement does not have a scientific basis and that such a policy should be discontinued where it is still practised.

Aerosols↗
PubMed1994

Effect of magnetic susceptibility contrast medium on myocardial signal intensity with fast gradient-recalled echo and spin-echo MR imaging: initial experience in humans.

PURPOSE: To show the effect of dysprosium diethylenetriaminepentaacetic acid bis-methylamine injection on the images of normal human myocardium. MATERIALS AND METHODS: T2-sensitive fast gradient-recalled echo (GRE) (repetition time [TR], 10.8 msec; echo time [TE], 4.2 msec) and spin-echo (SE) (TR, three RR intervals; TE, 60 msec) magnetic resonance (MR) imaging with driven equilibrium-preparation pulse was used to produce T2 contrast material enhancement. The contrast agent was injected into 12 healthy subjects at doses of 0.05, 0.1, 0.2, 0.4, and 0.6 mmol/kg. RESULTS: Driven equilibrium-prepared GRE images showed a transient decrease of myocardial signal intensity at doses of 0.2-0.6 mmol/kg. Postcontrast T2-weighted SE images showed a myocardial signal attenuation (30%-45% decrease) at a dose of 0.4 mmol/kg or higher. CONCLUSION: Dynamic MR imaging with a magnetic susceptibility contrast medium can be used to monitor the first pass of contrast media through human myocardium with a conventional MR imager and a fast GRE sequence.

Adult↗
PubMed1994

Quantification of collateral blood flow in coarctation of the aorta by velocity encoded cine magnetic resonance imaging.

BACKGROUND: Knowledge about the volume of collateral flow provides insight into the severity of coarctation of the aorta and may be critical in planning the operative approach. There is currently no method for the quantification of collateral flow in coarctation of the aorta. In this study, we applied velocity encoded cine magnetic resonance imaging (VENC-MR) to establish the flow pattern and volume of collateral flow in the descending thoracic aorta in normal subjects and patients with coarctation, introducing a new possibility to quantify the severity of the coarctation by determining the amount of collateral flow. METHODS AND RESULTS: VENC-MR was used to measure flow in the proximal and distal descending thoracic aorta in 10 normal subjects. In 23 patients with coarctation, flow was measured near the coarctation site and above the diaphragm. Patients were divided into a group with moderate to severe coarctation and a group with mild coarctation on the basis of clinical gradient between upper and lower extremities and the estimation of the gradient across the coarctation by Doppler echocardiography. The gradient across the coarctation and the degree of anatomic narrowing were also assessed by MR imaging. In normal volunteers, VENC-MR showed a 7 +/- 6% decrease in total flow, from proximal to distal aorta. The interobserver reproducibility was 3.9% to 4.9% (mean, 4.4%). In patients with moderate to severe coarctation, VENC-MR demonstrated an 83 +/- 50% increase in total flow from proximal to distal aorta, yielding a significant change compared with normal subjects (P < .01). Patients with mild coarctation showed a normal flow pattern and no significant change in total flow. There was a significant relation between the amount of flow increase in the distal aorta and the reduction in luminal diameter at the coarctation site (r = .94) as well as the clinical gradient (r = .84). CONCLUSIONS: This study shows the normal flow pattern in the descending thoracic aorta and its reversal in coarctation due to collateral flow. Thus, VENC-MR can measure collateral flow in coarctation and serves as a unique method for providing this important measurement of the severity of coarctation of the aorta.

Aorta, Thoracic↗
PubMed1994

Breath-hold MR cine angiography of coronary arteries in healthy volunteers: value of multiangle oblique imaging planes.

OBJECTIVE: Breath-hold MR cine angiography was used to depict the coronary arteries in healthy volunteers. Multiangle oblique imaging planes were evaluated for feasibility in showing continuous segments of the proximal and middle portions of the left anterior descending and right coronary arteries. SUBJECTS AND METHODS: Eighteen healthy subjects were examined with a 1.5-T MR imager. Fat-suppressed fast gradient-echo images (TR = 9.8 msec, TE = 3.5 msec) were acquired with a 13-cm receive surface coil. A segmented k-space data acquisition was used to obtain images of the coronary arteries at several phases of the cardiac cycle within a single breath-hold. Multiangle double oblique images that were tangential and sequential to the epicardial surface of the left ventricle were used to show the left anterior descending artery, and oblique coronal images were used to show the right coronary artery. Images of consecutive slice locations were shown in a cine format, and the length of each major coronary artery that was continuously visualized was measured. RESULTS: The left main coronary artery, proximal left anterior descending artery, and right coronary artery were demonstrated in all subjects. The mid and distal portions of the left anterior descending artery and diagonal branches were visualized best on multiangle oblique imaging planes. Continuous segments (> 6 cm) of the left anterior descending artery and right coronary artery were imaged in 14 subjects (78%) and 12 subjects (67%), respectively. Cine display was useful for showing the continuity of the coronary arterial segments and also for distinguishing arteries from veins. CONCLUSION: Double oblique imaging planes were useful in showing long segments of left anterior descending and right coronary arteries on coronary MR angiograms. Further work is necessary to improve detection of the left circumflex artery.

Adult↗
PubMed1994

An experimental study to evaluate the accuracy of diencephalic and pallidal target localization using the Brown-Roberts-Wells stereotactic system and unreformatted axial GE8800 CT scanning.

An experimental study was undertaken to evaluate the accuracy with which the intercommissural line (IL) length and anterior-posterior commissural (AC-PC) plane could be selected using unreformatted axial CT8800 imaging. Using these reference points, the Schaltenbrandt and Bailey stereotactic atlas and the Brown-Roberts-Wells (BRW) stereotactic system 1.82 mm ball bearings were deposited at selected diencephalic and pallidal targets in cadaver brains. There were errors in both IL length (median 1.5 mm) and AC-PC plane (median forward angulation of 9 degrees) estimation. Ball bearing deposition into large nuclei such as the pulvinar and globus pallidus and those in proximity to the mid IL such as the nuclei ventro oralis anterior (Voa), ventro oralis posterior (Vop) and ventro intermedius (Vim) was generally good; however, localization of the relatively small intralaminar nucleus was poor. This study suggests that when the AC and PC are not well imaged on sagittal reformations of axial diencephalic CT scans estimation of the AC-PC plane and IL from axial CT scans may be accurate enough for anatomical localization of certain functional stereotactic targets. The implications of this experimental study to operative functional stereotaxy are discussed.

Biopsy↗
PubMed1994

Teaching image-guided stereotactic methodology and functional neuroanatomy of the thalamus and pallidum: a simple ex vivo technique.

A simple and cheap model that enables on site, ex vivo, but very practical, learning of frame-based image-guided stereotactic technique and methodology, and the functional anatomy of the pallidum and thalamus is described. Using a cadaver skull, a specially prepared, formalin-fixed cadaver brain, and a modified stereotactic probe application of a stereotactic frame to the cranium, fiducial point acquisition, target point acquisition, computation of both arc and probe depth settings, and verification of target point accuracy can all be practiced. If diencephalic targets are selected for targeting with ball bearings then section of the cadaver brains, and study of a human thalamic stereotactic atlas provides an excellent and clinically relevant method of learning functionally important thalamic and pallidal anatomy. The method and techniques are described for CT imaging using the Brown-Roberts-Wells frame, but they are equally applicable to other frame types.

Brain Mapping↗
PubMed1993

Analysis of ferruginous bodies in bronchoalveolar lavage from foundry workers.

Classical ferruginous bodies in tissue samples are considered to be markers of past exposure to asbestos. Recent studies have shown that the presence of ferruginous bodies in bronchoalveolar lavage (BAL) fluid correlates with past exposure to asbestos and offers a more sensitive reference than occupational history. Lavage samples from five subjects who had worked in foundries were evaluated by light microscopy for the presence of ferruginous bodies and by transmission electron microscopy for both characterisation of the uncoated fibre burden and analysis of the cores of the ferruginous bodies. All samples at lower magnification (light microscopy (200 x)) contained ferruginous bodies that were externally consistent with asbestos bodies. At higher magnification (400 x), a separate population from this group could be identified by the presence of a thin black ribbon. Transmission electron microscopy of the core materials of ferruginous bodies and comparable uncoated particulates supported the reliability of higher magnification light microscopy for distinguishing most of those non-asbestos cores; however, a population of transparent non-asbestos cored ferruginous bodies were also shown to exist.

Aged↗
PubMed1992

Quantification of left to right atrial shunts with velocity-encoded cine nuclear magnetic resonance imaging.

OBJECTIVES: The purpose of this study was to evaluate the ability of velocity-encoded nuclear magnetic resonance (NMR) imaging to quantify left to right intracardiac shunts in patients with an atrial septal defect. BACKGROUND: Quantification of intracardiac shunts is clinically important in planning therapy. METHODS: Velocity-encoded NMR imaging was used to quantify stroke flow in the aorta and in the main pulmonary artery in a group of patients who were known to have an increased pulmonary to systemic flow ratio (Qp/Qs). The velocity-encoded NMR flow data were used to calculate Qp/Qs, and these values were compared with measurements of Qp/Qs obtained with oximetric data derived from cardiac catheterization and from stroke volume measurements of the two ventricles by using volumetric data from biphasic spin echo and cine NMR images obtained at end-diastole and end-systole. RESULTS: Two independent observers measured Qp/Qs by using velocity-encoded NMR imaging in 11 patients and found Qp/Qs ranging from 1.4:1 to 3.9:1. These measurements correlated well with both oximetric data (r = 0.91, SEE = 0.35) and ventricular volumetric data (r = 0.94, SEE = 0.30). Interobserver reproducibility for Qp/Qs by velocity-encoded NMR imaging was good (r = 0.97, SEE = 0.20). CONCLUSIONS: Velocity-encoded NMR imaging is an accurate and reproducible method for measuring Qp/Qs in left to right shunts. Because it is completely noninvasive, it can be used to monitor shunt volume over time.

Adolescent↗
PubMed1992

Application of cine nuclear magnetic resonance imaging for sequential evaluation of response to angiotensin-converting enzyme inhibitor therapy in dilated cardiomyopathy.

Cine nuclear magnetic resonance (NMR) imaging was used to serially measure cardiovascular function in 17 patients with New York Heart Association class II or III heart failure and left ventricular ejection fraction less than or equal to 45% who were treated for 3 months with benazepril hydrochloride, a new angiotensin-converting enzyme inhibitor, while continuing treatment with diuretic agents and digoxin. Interobserver reproducibilities for ejection fraction (r = 0.94, SEE 3.3%), end-systolic volume (r = 0.98, SEE 10.6 ml), end-diastolic volume (r = 0.99, SEE 8.29 ml), end-systolic mass (r = 0.96, SEE 15.4 g), end-systolic wall stress (r = 0.91, SEE 10 dynes.s.cm-5) and end-systolic stress/volume ratio (r = 0.85, SEE 0.13) demonstrated applicability of cine NMR imaging for the serial assessment of cardiovascular function in response to pharmacologic interventions in patients with heart failure. During 12 weeks of treatment with benazepril, ejection fraction increased progressively from 29.7 +/- 2.2% (mean +/- SEM) to 36 +/- 2.2% (p less than 0.05), end-diastolic volume decreased from 166 +/- 14 to 158 +/- 12 ml (p = NS), end-systolic volume decreased from 118 +/- 12 to 106 +/- 11 ml (p less than 0.05), left ventricular mass decreased from 235 +/- 13 to 220 +/- 12 g (p less than 0.05), end-systolic wall stress decreased 29% from 90 +/- 5 to 64 +/- 5 dynes.s.cm-5 (p less than 0.05), end-systolic pressure decreased from 92.6 +/- 3.7 to 78.8 +/- 5.3 (p less than 0.05) and end-systolic stress/volume ratio, a load-independent index of contractility, decreased from 0.83 +/- 0.05 to 0.67 +/- 0.06 (p less than 0.05), demonstrating that improved ejection fraction is due to afterload reduction.

Analysis of Variance↗
PubMed1992

What undergraduate physical education majors learn during a field experience.

Early field experiences and student teaching have a significant impact on the development of prospective teachers' perceptions of teaching and themselves as teachers (Dodds, 1989). The purpose of this study was to describe what happened to physical education majors during a secondary physical education methodology course that included two field experiences in which the undergraduates taught at least one lesson a day. The four research questions that guided the study were (a) What issues did the majors attend to as significant incidents from their teaching, and did these issues change during their field experiences? (b) What were the characteristics of field experience lessons they perceived as successful? (c) What were the characteristics of field experience lessons they perceived as unsuccessful? and (d) What were the physical education majors' conceptions of teaching? Participants in the study were 39 junior-year physical education teacher education majors. Data were collected using the critical incident technique (Flanagan, 1954) and an open-ended, written questionnaire that was designed to encourage the majors to reflect on various aspects of their teaching experience. The questionnaire and critical incidents were analyzed using an inductive analytical procedure and a series of categories developed from several readings of students' writings. The teacher preparation program affected how these trainees defined and evaluated their teaching experiences. In contrast to some of the earlier work in physical education, the results indicated pupil learning, quality lesson planning to ensure pupil learning, and efficient lesson management were major characteristics of successful lessons for these trainees. The trainees presented "theories of knowledge" that emphasized technical concepts of teaching with little attention to the social or ethical dimensions of their work or the content knowledge of their field. Additional research is needed to examine appropriate programmatic efforts to help preservice teachers reflect not only on teaching, learning, and schooling as a technical enterprise but also as a moral and ethical enterprise.

Attitude↗