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M Bourne

Publications and source records attributed to M Bourne.

15 recordsLinked to original sources
PubMed2005

Techniques and trouble-shooting in high spatial resolution thin slice MRI for rectal cancer.

MRI is increasingly advocated as an optimal method of staging rectal cancer. The technique enables depiction of the relationship of tumour to the mesorectal fascia and may thus identify tumours at risk of positive circumferential margin involvement at surgery. Depth of extramural spread may also be accurately measured and tumour deposits within the mesorectum are shown. It is important that a high spatial resolution technique is used in order to accurately depict these features and care should be taken in ensuring that images acquired cover the entire rectal tumour and mesorectum. This paper describes the technique of high spatial resolution rectal cancer imaging and the potential technical pitfalls in acquiring good quality images. Important factors to consider include: adequate scan duration to achieve high spatial resolution images with sufficient signal to noise ratio, careful positioning of the pelvic phased array coil, use of T2 weighted turbo spin-echo rather than T1 weighted imaging and careful planning of scans to ensure that images are obtained perpendicular to the rectal wall.

Humans↗
PubMed2001

Off-site evaluation of liver lesion detection by Gd-BOPTA-enhanced MR imaging.

The aim of this study was to determine the efficacy of Gd-BOPTA-enhanced MRI in liver lesion detection in comparison with unenhanced MRI and dynamic CT. The image sets of 148 of 151 patients enrolled in a multicenter German phase-III trial were evaluated by two independent radiologists unaffiliated with the investigating centers. Patients underwent a routine MRI protocol comprising T2- and T1-weighted spin-echo and T1-weighted gradient-echo (GE) sequences pre and 1 h post 0.1 mmol/kg Gd-BOPTA (Bracco-Byk Gulden, Konstanz, Germany). Additionally, a serial T1-weighted GE scan was performed after administration of the first half of the dose. All patients underwent dynamic contrast-enhanced CT. The evaluation was performed with regard to the number and size of lesions detected per patient by each modality or sequence. Furthermore, all pre CM and pre + post CM image sets were analyzed for number of lesions per patient. Both readers detected significantly more lesions in the contrast-enhanced image set compared with the unenhanced image set (32 and 39 %, respectively; p < 0.0001). While contrast-enhanced CT detected a similar number of lesions to unenhanced MRI, it was clearly inferior to contrast-enhanced MRI (reader 1: p = 0.0117; reader 2: p = 0.0225). Of the T1-weighted scans performed, the dynamic and late T1-weighted GE exams contributed most to the increased lesion detection rate (reader 1: p = 0.0007; reader 2: p = 0.0037). The size of the smallest lesion detected by means of MRI was significantly larger in the pre-CM image sets than in the pre + post CM image sets (reader 1: p = 0.001; reader 2: p < 0.0001). Gd-BOPTA-enhanced MRI detected significantly smaller lesions than contrast-enhanced CT (reader 1: p = 0.0117; reader 2: p = 0.0925). Gd-BOPTA-enhanced MR imaging improves liver lesion detection significantly over unenhanced MRI and dynamic CT.

Adult↗
PubMed2001

Efficacy of single-dose and multidose rofecoxib in the treatment of post-orthopedic surgery pain.

To determine the efficacy of rofecoxib in post-orthopedic surgery pain, we conducted a double-blind, randomized, placebo- and active-comparator-controlled, parallel-group trial. Two hundred eighteen patients enrolled. Day 1 patients received placebo, rofecoxib 50 mg, or naproxen sodium 550 mg. Days 2 through 5, the placebo and naproxen sodium groups received placebo, and the rofecoxib group received rofecoxib 25 or 50 mg. Rofecoxib 50 mg was superior to placebo (P < .05) and similar to naproxen sodium for all single-dose measures of pain relief. Days 2 through 5, the rofecoxib 50 mg group used less supplemental narcotic analgesia (P = .005) and reported less pain on global evaluations (P = .041) when compared with the placebo group; the efficacy of rofecoxib 25 mg fell between that of placebo and rofecoxib 50 mg for these endpoints (P < or = .267). Rofecoxib 50 mg once daily effectively treated post-orthopedic surgery pain.

Adult↗
PubMed2000

Numerical study of blood flow in an anatomically realistic aorto-iliac bifurcation generated from MRI data.

Magnetic resonance imaging and computational fluid dynamics (CFD) have been used in combination to simulate flow patterns at the human aorto-iliac bifurcation. Vascular anatomy was reconstructed from stacked two-dimensional (2D) time-of-flight images, and revealed asymmetric, nonplanar geometry with curvature in the abdominal aorta and right iliac artery. The left iliac artery was straight and exhibited a smaller take off angle than the right iliac artery. The anatomical reconstruction was used to generate a computational mesh and obtain CFD predictions of flow and wall shear stress (WSS) within the region of interest. The dynamic boundary conditions necessary were specified by 2D cine phase contrast measurements of velocity profiles in each component vessel. Predicted flow patterns were in good quantitative agreement with experiment and demonstrated major differences in WSS distributions between the iliac arteries. This noninvasive approach has considerable potential to evaluate local geometries and WSS as risk factors for arterial disease in individual subjects.

Adult↗
PubMed1999

Reconstruction of blood flow patterns in human arteries.

Local haemodynamic factors in large arteries are associated with the pathophysiology of cardiovascular diseases such as atherosclerosis and strokes. In search of these factors and their correlation with atheroma formation, quantitative haemodynamic data in realistic arterial geometry become crucial. At present no in vivo non-invasive technique is available that can provide accurate measurement of three-dimensional blood velocities and shear stresses in curved and branching sites of vessels where atherosclerotic plaques are found frequently. This paper presents a computer modelling technique which combines state-of-the-art computational fluid dynamics (CFD) with new noninvasive magnetic resonance imaging techniques to provide the complete haemodynamic data in 'real' arterial geometries. Using magnetic resonance angiographic and velocity images acquired from the aortic bifurcation of a healthy human subject, CFD simulations have been carried out and the predicted flow patterns demonstrate the non-planar-type flow characteristics found in experimental studies.

Aorta, Abdominal↗
PubMed1998

Magnetic resonance image processing and structured grid generation of a human abdominal bifurcation.

Magnetic resonance angiography (MRA) offers a non-invasive approach to the acquisition of anatomically accurate human arterial structure. Combining the latest computational fluid dynamics (CFD) techniques with clinical data from MRA, the detailed haemodynamics information in the human circulation system can be obtained. In this paper, a novel computer method is presented, which generates automatically a computational grid for a human abdominal bifurcation from a set of conventional MRA images. The method covers the complete sequence from MR image segmentation, 3-D model construction, grid generation, to grid quality evaluation. Results demonstrate that the computer program developed is capable of generating a good quality grid for human arterial bifurcations from MRA images with minimum user input. The resultant grid can be used directly for further computer simulation of the flow.

Abdomen↗
PubMed1998

Hospital outcomes management: the Care Continuum and Health Outcomes Project.

The Care Continuum and Health Outcomes Project is part of a national initiative to build an outcomes management approach in health care. This paper examines the baseline performance of the study. In 1995-96, 7154 Australian Capital Territory hospital inpatients were selected to take part in a five-wave survey over six months. In addition to the survey, the project involved the unit record linkage of routine data collections. A total of 5668 people (79%) agreed to participate in the survey, with 85% of these people agreeing to release their Medicare data. There were significant variations in participation rates between hospitals and wards. Factors contributing to these variations included patient socioeconomic status, disease type and illness severity. In conclusion, the success in establishing the project indicates that it is possible to conduct a broad scientific study within the health system, and that there are strong implications that ongoing scientific evaluations can be embedded within routine clinical practice.

Adult↗
PubMed1998

The combination of magnetic resonance angiography and computational fluid dynamics: a critical review.

Computational Fluid Dynamics (CFD) has proven to be a valuable technique in the study of blood flow in arteries because of its capability of obtaining quantitatively velocities and wall shear stress. However, the "bottleneck" problem limiting the application of CFD is the difficulty of constructing anatomically realistic arterial geometries. In this survey, an overview is presented of the progress over the last decade in the development of magnetic resonance angiography (MRA) techniques, medical image processing and CFD, as well as the combination of these techniques in hemodynamics research. It is demonstrated that with modern angiographic techniques such as MRA, noninvasive measurement of human angiograms becomes possible and practical. Together with digital medical image processing and analysis techniques, computational models can be constructed for the "real" human arteries without making any geometric assumptions. When allied with state-of-the-art CFD codes, velocity and wall shear stress distributions, as well as particle trajectories, can be determined in the arteries.

Animals↗
PubMed1997

Analysis of cardiac function by MRI and stereology.

Design-based stereology and phase contrast magnetic resonance imaging (MRI) were combined to monitor changes in the volume of the four chambers of the human heart during the cardiac cycle. The data set consisted of 18 adjacent slices (or 'scanning levels') of 0.5 cm thickness, perpendicular to the long axis of the body, and encompassing the whole heart of a healthy volunteer. At each scanning level, a cardiac gated MR image was obtained at each of 16 equally spaced time frames within the cardiac cycle. Given stationarity with respect to time, absence of image artefacts and appropriate definition of chamber boundaries, for each time frame unbiased estimates of total blood volume in the relevant heart chambers were efficiently obtained using the Cavalieri method and point counting. Combined with a proper MRI acquisition, modern stereological methods constitute an efficient and reliable tool to quantify cardiac function noninvasively.

Blood Volume↗
PubMed1996

Assessment of hemodynamic effects of angiotensin-converting enzyme inhibitor therapy in chronic aortic regurgitation by using velocity-encoded cine magnetic resonance imaging.

Long-term treatment with angiotensin-converting enzyme (ACE) inhibitors has beneficial effects in patients with chronic aortic regurgitation by reducing left ventricular volumes and regurgitant fraction. Velocity-encoded cine magnetic resonance imaging can directly measure antegrade (forward stroke volume) and retrograde blood flow (regurgitant volume) in the ascending aorta. Velocity-encoded cine magnetic resonance imaging was used in 9 patients with moderate to severe aortic regurgitation (regurgitant fraction 49% +/- 17%) to measure regurgitant fraction, regurgitant volume, and forward stroke volume at baseline and 3 months after therapy with enalapril (mean dose 29 +/- 13 mg). Ten additional patients with aortic regurgitation without any drug therapy served as a control group. In the treatment group, systolic blood pressure slightly decreased from 132 +/- 20 mm Hg to 121 +/- 14 mm Hg (p = not significant), whereas diastolic blood pressure and heart rate (beats per minute) remained unchanged. Regurgitant fraction decreased in 6 patients (responders) from 49% +/- 19% to 39% +/- 20% (percentage change 24% +/- 14%, p = 0.002) and was unchanged in 3 patients (nonresponder, 49% +/- 19% vs 51% +/- 16%; p = not significant). In the responder group, forward stroke volume increased from 128 +/- 32 ml to 148 +/- 57 ml, whereas regurgitant volume remained unchanged (67 +/- 40 ml vs 65 +/- 51 ml). At baseline, the responder group had a significant higher total vascular resistance than the nonresponder group (998 +/- 538 dyne.sec.cm-5 vs 625 +/- 214 dyne.sec.cm-5; p < 0.05). With enalapril treatment, total vascular resistance in the responder group tended to decrease (891 +/- 576 dyne.sec.cm-5), but slightly increased in the nonresponder group (679 +/- 276 dyne.sec.cm-5). The control group showed no changes in regurgitant fraction, regurgitant volume, forward stroke volume, and total vascular resistance at follow-up.

Adult↗
PubMed1993

A comparison of the effects of single doses of amoxapine and amitriptyline on autonomic functions in healthy volunteers.

We have studied the effects of single oral doses of amoxapine (100 mg and 200 mg), amitriptyline (50 mg and 100 mg), and placebo on some autonomic functions in ten healthy volunteers, using a balanced double-blind crossover design. Amitriptyline significantly reduced salivation and it significantly attenuated both miosis evoked by locally applied pilocarpine and sweat secretion evoked by locally applied carbachol. Amoxapine did not significantly alter any of these measures. Neither treatment significantly altered the pupillary light reflex (latency, amplitude, or 75% recovery time). Resting pupil diameter was significantly reduced by the higher dose of amoxapine but was not affected by the other treatments. The higher dose of amoxapine significantly increased supine systolic blood pressure, but did not affect heart rate or diastolic blood pressure; amitriptyline had no effect on any of these cardiovascular measures. These results confirm the antimuscarinic effects of amitriptyline in man, but provide no evidence for antimuscarinic effects of amoxapine.

Adolescent↗
PubMed1993

Unbiased estimation of human body composition by the Cavalieri method using magnetic resonance imaging.

The classical methods for estimating the volume of human body compartments in vivo (e.g. skin-fold thickness for fat, radioisotope counting for different compartments, etc.) are generally indirect and rely on essentially empirical relationships--hence they are biased to unknown degrees. The advent of modern non-invasive scanning techniques, such as X-ray computed tomography (CT) and magnetic resonance imaging (MRI) is now widening the scope of volume quantification, especially in combination with stereological methods. Apart from its superior soft tissue contrast, MRI enjoys the distinct advantage of not using ionizing radiations. By a proper landmarking and control of the scanner couch, an adult male volunteer was scanned exhaustively into parallel systematic MR 'sections'. Four compartments were defined, namely bone, muscle, organs and fat (which included the skin), and their corresponding volumes were easily and efficiently estimated by the Cavalieri method: the total section area of a compartment times the section interval estimates the volume of the compartment without bias. Formulae and nomograms are given to predict the errors and to optimize the design. To estimate an individual's muscle volume with a 5% coefficient of error, 10 sections and less than 10 min point counting (to estimate the relevant section areas) are required. Bone and fat require about twice as much work. To estimate the mean muscle volume of a population with the same error contribution, from a random sample of six subjects, the workload per subject can be divided by square root of 6, namely 4 min per subject. For a given number of sections planimetry would be as accurate but far more time consuming than point counting.

Body Composition↗
PubMed1985

Multiple-hospital survey of ejection-fraction variability using a cardiac phantom.

A dynamic cardiac phantom was used to provide identical input data at 11 different nuclear medicine laboratories throughout the Philadelphia area, and the variability in the resulting calculations of ejection fraction (EF) was assessed. The variability observed between different operators using the same computer system averaged 3 EF units, which was similar to that between different observers using different types of computers. In the range of low ejection fractions, however, there was a suggestion that EFs calculated with an MDS computer were slightly lower than those from a DEC computer.

Cardiac Output↗