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Biomedical subjects

David Atkinson

Publications and source records attributed to David Atkinson.

24 records · Page 2Linked to original sources
PubMed2002

A study of the motion and deformation of the heart due to respiration.

This paper describes a quantitative assessment of respiratory motion of the heart and the construction of a model of respiratory motion. Three-dimensional magnetic resonance scans were acquired on eight normal volunteers and ten patients. The volunteers were imaged at multiple positions in the breathing cycle between full exhalation and full inhalation while holding their breath. The exhalation volume was segmented and used as a template to which the other volumes were registered using an intensity-based rigid registration algorithm followed by nonrigid registration. The patients were imaged at inhale and exhale only. The registration results were validated by visual assessment and consistency measurements indicating subvoxel registration accuracy. For all subjects, we assessed the nonrigid motion of the heart at the right coronary artery, right atrium, and left ventricle. We show that the rigid-body motion of the heart is primarily in the craniocaudal direction with smaller displacements in the right-left and anterior-posterior directions; this is in agreement with previous studies. Deformation was greatest for the free wall of the right atrium and the left ventricle; typical deformations were 3-4 mm with deformations of up to 7 mm observed in some subjects. Using the registration results, landmarks on the template surface were mapped to their correct positions through the breathing cycle. Principal component analysis produced a statistical model of the motion and deformation of the heart. We discuss how this model could be used to assist motion correction.

Adult↗
PubMed2002

3-D freehand echocardiography for automatic left ventricle reconstruction and analysis based on multiple acoustic windows.

A new method is proposed to reconstruct and analyze the left ventricle (LV) from multiple acoustic window three-dimensional (3-D) ultrasound acquired using a transthoracic 3-D rotational probe. Prior research in this area has been based on one acoustic window acquisition. However, the data suffers from several limitations that degrade the reconstruction and reduce the clinical value of interpretation, such as the presence of shadow due to bone (ribs) and air (in the lungs) and motion of the probe during the acquisition. In this paper, we show how to overcome these limitations by automatically fusing information from multiple acoustic window sparse-view acquisitions and using a position sensor to track the probe in real time. Geometric constraints of the object shape, and spatiotemporal information relating to the image acquisition process, are used in new algorithms for 1) grouping endocardial edge cues from an initial image segmentation and 2) defining a novel reconstruction method that utilizes information from multiple acoustic windows. The new method has been validated on a phantom and three real heart data sets. In the phantom study, one finger of a latex glove was scanned from two acoustic windows and reconstructed using the new method. The volume error was measured to be less than 4%. In the clinical case study, 3-D ultrasound and magnetic resonance imaging (MRI) scanning were performed on the same healthy volunteers. Quantitative ejection fractions (EFs) and volume-time curves over a cardiac cycle were estimated using the new method and compared to cardiac MRI measurements. This showed that the new method agrees better with MRI measurements than the previous approach we have developed based on a single acoustic window. The EF errors of the new method with respect to MRI measurements were less than 6%. A more extensive clinical validation is required to establish whether these promising first results translate to a method suitable for routine clinical use.

Algorithms↗
PubMed2002

Impact of disability on quality of life of rural disabled people in Bangladesh.

This study examined the impact of disability on the quality of life of disabled people in rural Bangladesh. A primary healthcare specialist conducted a door-to-door survey in two villages in Bangladesh to collect socioeconomic and demographic information on the villagers and for identification of disabled people. Information on disability and how it affected their life was also obtained either from the disabled people or from their caregivers by interviewing them. The study revealed that disability had a devastating effect on the quality of life of the disabled people with a particularly negative effect on their marriage, educational attainment, employment, and emotional state. Disability also jeopardized their personal, family and social life. More than half of the disabled people were looked at negatively by society. Disabled women and girl children suffered more from negative attitudes than their male counterparts, resulting in critical adverse effects on their psychological and social health. A combination of educational, economic and intensive rehabilitative measures should be implemented urgently to make them self-reliant. Collaborative communication between professionals and parents, behavioural counselling, formation of a self-help group, and comprehensive support to families will reduce their suffering.

Affective Symptoms↗
PubMedDate not supplied

Establishing the Canadian Community Monitoring Network.

Community-based ecosystem monitoring activities in Canada are increasing in response to a number of factors including: (i) the needs of decision-makers for timely information on local environmental changes; (ii) limited use of government monitoring data and information by decision makers: (iii) government cuts to monitoring programs; (iv) the increasingly recognized need to include stakeholders in planning and management processes; and (v) the desire of citizens to contribute to environmental protection. To date there has been no network coordination of community based monitoring in Canada. This paper reports on the establishment of the Canadian Community Monitoring Network by Environment Canada's Ecological Monitoring and Assessment Network Coordinating Office and the Canadian Nature Federation. Information on research prepared in support of network establishment is presented along with a discussion of the potential of the network.

Animals↗
PubMedDate not supplied

From cells to colonies: at what levels of body organization does the 'temperature-size rule' apply?

An inverse relationship between temperature during ontogeny and final body size is widespread in ectotherms, but poorly understood. Evidence suggests that within organs, this "temperature-size rule" (TSR) may also apply to cell size with no change in numbers. So how closely do reductions in size and number of cells and other repeated structures correlate with size reduction at higher levels of organization? We examine this in the context of a proposal that size and/or number changes at various organizational levels are adaptive responses to temperature- and size-dependent oxygen supply. We subjected two clones of the modular colonial bryozoan, Celleporella hyalina, to orthogonal combinations of two temperatures and two oxygen concentrations during ontogeny, observing effects on sizes of colonies and larvae, and sizes and numbers of cells, tentacles, and modules (autozooids). We found that the size:number responses varied among cell types and among structures at different levels of organization, with the inverse temperature-size relationship applying only to larval parenchymal cells and colony modules. Using our findings and other evidence we propose a unifying adaptive hypothesis that predicts how temperature affects the sizes of mitochondria, cells, organs, modules and organisms, and their relationships with processes that determine the functional capacity of aerobic metabolism.

Animals↗