Biomedical subjects

Jim Graham

Publications and source records attributed to Jim Graham.

6 recordsLinked to original sources

PubMed2005

A freely accessible, evidence based, objective system of analysis of posterior capsular opacification; evidence for its validity and reliability.

BACKGROUND: The aim of this study was to develop a system of computerised analysis of digital images of posterior capsule opacification (PCO) that is evidence based, objective and freely available. The paper will present evidence for the reliability and validity of the developed system. METHODS: The system of PCO analysis was developed considering current published evidence on visual significance of PCO and additional investigative analysis of PCO images. Details of the image processing and analysis steps are discussed and a final system that measures an entropy score weighted toward proximity to central areas is described. In order to assess validity, the systems ability to measure PCO progression is assessed along with the visual significance of its final computerised scores. Reliability of the system is also assessed. RESULTS: The final system runs successfully and is simple to use. Analyses of PCO by the system show an ability to detect early progression of PCO as well as detection of visually significant PCO. Images with no clinical PCO produce very low scores in the analysis. Reliability of the system of analysis is shown to be satisfactory. CONCLUSION: This paper presents a system of PCO analysis that is evidence based, objective and clinically useful. Substantial evidence is provided for its validity and reliability.

Access to Information↗

PubMed2005

Developing functional outcome measures for unilateral neglect: a pilot study.

Stroke patients may develop personal neglect, peripersonal neglect or both. Four new measures were tested in a sample of 42 right-handed inpatients (25 male; 17 female, median age 72 years). Participants removed keys from a rack, identified grocery items, washed their face, and cleaned a tray. Prior to this, they were classified as: no neglect (15), personal neglect (8), peripersonal neglect (7), and both personal and peripersonal neglect (12). The sensitivity and specificity of each new measure was determined by agreement with the classification. Test-retest reliability was determined using weighted kappa statistics or limits of agreement. Four occupational therapists (OTs) rated videos of the face and tray measures, and software was developed to measure objectively time spent and area covered on Face and Tray. Keys and Grocery had high specificity, good reliability but poor sensitivity. For the OTs' video ratings, there was good and moderate inter-rater reliability on Tray and Face respectively for area covered, but not time spent. Intra-rater reliability was also better for area than time on Tray. However, the validity of Face and Tray themselves is currently inadequate. A longitudinal study is proposed to modify the measures, increase their sensitivity and evaluate their ability to monitor change over time.

Aged↗

PubMed2004

The effect of ovariectomy on mandibular cortical thickness in the rat.

OBJECTIVES: The purpose of this study was to investigate the effects of long-term oestrogen deficiency on mandibular cortical thickness in ovariectomized rats. METHODS: Twelve female rats either underwent ovariectomy or received a sham-operation. One year later images of the left side of the mandible were made using a standardized radiographic protocol. Manual measurements were made of the lower mandibular cortical thickness at three locations. The mean cortical thickness was also assessed using a specially developed image analysis program by placing points at three positions, identical to those used for the manual measurements, and additionally at 20 points evenly distributed along the mandibular cortex. RESULTS: The mean mandibular cortical thickness of the ovariectomized mandibles was significantly less than that of the sham-operated rats, measured using the computer image analysis (p=0.016, 95% CI=0.125, 0.016) and measured manually (p=0.011, 95% CI=0.0218, 0.1309). When 20 computational points were used, the mean mandibular cortical width of the ovariectomized rats was significantly less than that for the control rats (p=0.016, 95% CI=0.127, 0.018). CONCLUSIONS AND CLINICAL IMPLICATIONS: Long-term oestrogen deficiency in ovariectomized rats decreased the mandibular cortical thickness. If our result is applicable to human studies, a considerable duration of oestrogen deficiency may be necessary before a reduction of mandibular cortical bone loss can be observed. Because mandibular cortical bone is resistant to resorption, the value of clinically determined mandibular cortical thickness measurements as a method of detecting patients at risk of osteoporosis may have a reduced importance in younger postmenopausal patients.

Animals↗

PubMed2003

Using statistical image models for objective evaluation of spot detection in two-dimensional gels.

Protein spot detection is central to the analysis of two-dimensional electrophoresis gel images. There are many commercially available packages, each implementing a protein spot detection algorithm. Despite this, there have been relatively few studies comparing the performance characteristics of the different packages. This is in part due to the fact that different packages employ different sets of user-adjustable parameters. It is also partly due to the fact that the images are complex. To carry out an evaluation, "ground truth" data specifying spot position, shape and intensities needs to be defined subjectively on selected test images. We address this problem by proposing a method of evaluation using synthetic images with unambiguous interpretation. The characteristics of the spots in the synthetic images are determined from statistical models of the shape, intensity, size, spread and location of real spot data. The distribution of parameters is described using a Gaussian mixture model obtained from training images. The synthetic images allow us to investigate the effects of individual image properties, such as signal-to-noise ratios and degree of spot overlap, by measuring quantifiable outcomes, e.g. accuracy of spot position, false positive and false negative detection. We illustrate the approach by carrying out quantitative evaluations of spot detection on a number of widely used analysis packages.

Algorithms↗

PubMed2003

Statistical models of shape for the analysis of protein spots in two-dimensional electrophoresis gel images.

In image analysis of two-dimensional electrophoresis gels, individual spots need to be identified and quantified. Two classes of algorithms are commonly applied to this task. Parametric methods rely on a model, making strong assumptions about spot appearance, but are often insufficiently flexible to adequately represent all spots that may be present in a gel. Nonparametric methods make no assumptions about spot appearance and consequently impose few constraints on spot detection, allowing more flexibility but reducing robustness when image data is complex. We describe a parametric representation of spot shape that is both general enough to represent unusual spots, and specific enough to introduce constraints on the interpretation of complex images. Our method uses a model of shape based on the statistics of an annotated training set. The model allows new spot shapes, belonging to the same statistical distribution as the training set, to be generated. To represent spot appearance we use the statistically derived shape convolved with a Gaussian kernel, simulating the diffusion process in spot formation. We show that the statistical model of spot appearance and shape is able to fit to image data more closely than the commonly used spot parameterizations based solely on Gaussian and diffusion models. We show that improvements in model fitting are gained without degrading the specificity of the representation.

Computer Simulation↗

PubMedDate not supplied

Georgia's ADAP update.

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Anti-HIV Agents↗