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Biomedical subjects

D G Sutton

Publications and source records attributed to D G Sutton.

14 recordsLinked to original sources
PubMed2001

The(13)C-octanoic acid breath test for detection of effects of meal composition on the rate of solid-phase gastric emptying in ponies.

The aim of this study was to apply the(13)C-octanoic acid breath test for detection of alterations in the rate of solid-phase gastric emptying, induced by changes in test meal composition, in ponies. After a 14 hour fast the ponies (n = 4) ingested a test meal with 0, 35 or 70 ml soya oil, and labelled with 250 mg(13)C-octanoic acid. Each pony was given each of the three test meals on three separate occasions, in a randomised order. Exhaled breath samples were collected for 12 hours after ingestion of the test meal. Breath samples were analysed by continuous flow isotope ratio mass spectrometry. Three indices of breath(13)C-enrichment were computed, half-dose recovery time (t 1/2), gastric emptying coefficient (GEC) and time to peak breath(13)C-excretion t(max). The(13)C-octanoic acid breath test was a reliable means of assessing the significantly decreased rate of gastric emptying in the pony, associated with addition of soya oil to the test meal.

Animal Feed↗
PubMed2001

A computer model of an image intensifier system working under automatic brightness control.

A computer model of a fluoroscopy unit operating under automatic brightness control has been developed. The model has been validated by simulating one particular unit but is very general in nature and can easily be applied to other fluoroscopy systems. The model was developed by breaking the operation of a fluoroscopy unit down into its constituent parts then implementing each part in a module of code. It is controlled using the input air kerma to the intensifier face. Discrepancies from the situation when the model is controlled by the energy deposited in the input phosphor have been investigated and shown to be negligible over the operating range. To calculate entrance surface dose rates (ESDRs) to water and polymethylmethacrylate (PMMA) phantoms, Monte Carlo techniques were used to generate backscatter factors for these materials using the beam geometry and range of possible tube potentials and field sizes of a typical mobile image intensifier unit. The model was validated by calculating ESDRs to different thicknesses of water and PMMA phantoms. The predictions generated by the model were in good agreement with experimental measurements. Potential uses of the model include evaluation of dose reduction techniques, investigation of the balance between patient dose and image quality, and assessment of scatter dose.

Algorithms↗
PubMed2000

Caecocaecal and caecocolic intussusceptions associated with larval cyathostomosis in four young horses.

This report describes the clinical and pathological features of 4 horses affected by caecocaecal or caecocolic intussusceptions associated with larval cyathostomiasis. In each case, there was clinical and/or pathological evidence of concurrent larval cyathostomosis. They all demonstrated variable signs including diarrhoea, pyrexia, weight loss and subcutaneous oedema and cyathostome larvae were identified in the faeces of 3 of the horses. These cases highlight the need to consider caecal intussusceptions as a possible complication in horses affected by larval cyathostomosis, especially where signs of abdominal pain are severe or persistent.

Animals↗
PubMed1999

Balancing patient dose and image quality.

The formation of images in diagnostic radiology involves a complex interdependence of many factors. The ideal balance is to obtain an image which is adequate for the clinical purpose with the minimum radiation dose. Factors which affect radiation dose and image quality can be grouped under three headings; radiation quality, photon fluence and removal of scattered radiation. If optimal performance is to be achieved, it is necessary to understand how these factors influence image formation and affect radiation dose, and apply methodology for image quality and dose analysis at each stage in the development and use of X-ray equipment.

Fluoroscopy↗
PubMed1999

Measurement of image quality in diagnostic radiology.

The aim in radiology is to obtain images which are adequate for the clinical purpose with the minimum radiation dose to the patient. If optimum performance is to be achieved, assessments of image quality must be made to balance against patient dose. The subjective nature of image interpretation makes an objective approach to such assessment difficult. Methods widely applied involve the use of test objects, which although providing a measure of imaging performance may be difficult to link to clinical image formation. The ideal method for evaluation of imaging techniques is through clinical trials and this should be used to address major questions. Scoring of quality criteria, relating to features observed in a normal clinical radiograph, provides a simple method through which image quality can be assessed in every hospital department.

Clinical Trials as Topic↗
PubMed1998

Protocol for measurement of patient entrance surface dose rates for fluoroscopic X-ray equipment.

While patient entrance surface dose rate is an important indicator of dose performance for fluoroscopic units, there has been no standardized approach to measuring this. Since results are strongly dependent on the type of phantom used and the relative positions of the X-ray tube, intensifier and phantom, comparisons of the performance for different units are difficult to make. This document sets out a protocol for making these measurements using a standard phantom and standard configurations for different types of X-ray unit Values of dose rates which might be expected are given.

Clinical Protocols↗
PubMed1995

Estimating the diagnostic yields resulting from renography and deconvolution parameters: a logistic regression analysis.

METHODS: Seventy patients with established diagnoses of normal, parenchymally insufficient or acutely obstructed kidneys were subjected to gamma camera renography. Deconvolution was then performed using three main techniques subdivided into six variants. Parameters from time-activity curves as well as retention curves were calculated. Logistic regression analysis was performed to assess the ability of renography and deconvolution methods to differentiate between kidney groups. RESULTS: Discrimination between the groups was achieved by standard renography using six of 17 tested renogram parameters. Based on a set of six curve parameters, the correct classification rates ranged 86%-100%. Five of the six variants of the deconvolution technique used produced similar results. None, however, produced results which were as robust as those from renography. The sixth deconvolution method was consistently worse than the others. CONCLUSION: Standard renography was consistently better than any of the deconvolution techniques used in the separation of the kidney groups. Conceptually, the results of a logistic regression analysis of renogram parameters may raise possibilities in the field of computer-aided diagnosis.

Adolescent↗
PubMed1993

Constrained least-squares restoration and renogram deconvolution: a comparison with other techniques.

It has previously been shown that an iterative constrained least-squares (CLSR) technique using a noise-based constraint may be superior to other methods of renogram deconvolution analysis. To test this hypothesis on real data, renography was performed on 70 patients with established diagnoses of normal, insufficient or acutely obstructed kidneys. Standard renography parameters were obtained from the time activity curves which were then deconvolved using three techniques. One kidney per patient was chosen at random for analysis resulting in a total of 43 normal and 27 diseased kidneys. The ability of each of the analytical techniques to discriminate between normal and diseased kidneys was assessed using logistic regression. CLSR proved to be robust and provide the best discrimination of the deconvolution techniques. However, the best overall discrimination was provided by a model based on the renography parameters excretion ratio, rate of uptake and time to peak activity which correctly classified 86% of the kidneys. It is possible that the renogram parameters could be used to produce notional probabilities of renal dysfunction which the physician could use as an aid in the interpretation of gamma-camera renography.

Acute Kidney Injury↗
PubMed1992

Constrained least-squares restoration and renogram deconvolution: a comparison by simulation.

Before deconvolution can be used in renography, it is necessary to decide whether the renal function is sufficiently good to allow it. To see if this decision can be circumvented, an iterative constrained least-squares restoration (CLSR) method was implemented in which the point of termination of the iteration occurs when a residual vector has a value less than an estimate of the noise in the original renogram curve. The technique was compared with the matrix algorithm and with direct FFT division. The comparison was achieved by deconvolving simulated renogram data with differing transit time spectra and statistics. As expected, the FFT technique produced results of little value whereas the CLSR and matrix methods produced values of mean transit time (MTT) that differed slightly from the expected results. Analysis indicated that the matrix approach was superior when the percentage noise component was less than 6% and vice versa. No technique produced useful transit time spectra. As the CLSR technique produced better results than the matrix method in simulations with relatively long MTTs and high noise, it seems reasonable to suggest that it might be used for renogram deconvolution without the need for previous inspection of the curves.

Humans↗
PubMed1990

Modeling the prehistoric Maori population.

Skeletal and comparative evidence of mortality is combined with fertility estimates for the precontact Maori population of New Zealand to determine the implied rate of precontact population growth. This rate is found to be too low to populate New Zealand within the time constraints of its prehistoric sequence, the probable founding population size, and the probable population size at contact. Rates of growth necessary to populate New Zealand within the accepted time span are calculated. The differences between this minimum necessary rate and the skeletally derived rate are too large to result solely from inadequacies in the primary data. Four alternative explanations of this conundrum are proposed: 1) skeletal evidence of precontact mortality is highly inaccurate; 2) skeletal evidence of fertility is severely underestimating actual levels; 3) there was very rapid population growth in the earliest part of the sequence up to 1150 A.D., from which no skeletal evidence currently is available; or 4) the prehistoric sequence of New Zealand may have been longer than the generally accepted 1,000-1,200 years. These alternatives are examined, and a combination of the last two is found to be the most probable. The implications of this model for New Zealand prehistory and Oceanic paleodemography are discussed.

Fertility↗
PubMed1989

Gallbladder function and fasting enterogastric bile reflux.

The relationship between gallbladder function and duodenogastric reflux of bile has been investigated in the fasting phase by 99Tcm-EHIDA biliary scintigraphy in 370 patients with abdominal pain. This isotope is cleared from the blood-pool by hepatocellular function and is excreted into the biliary tract. Obstruction of the common bile duct was found in 79 patients, leaving 291 who were evaluable for duodenogastric bile reflux. Gallblader function was present in 169 and absent in 122 patients. Duodenogastric reflux of bile was observed in 82 patients, 10 of whom had had previous gastric surgery. Only 298 of 169 (17%) patients with a functioning gallbladder showed evidence of enterogastric bile reflux compared to 43 of 122 (35%) with absent gallbladder function (p less than 0.005 by Chi Square). These results suggest that continuous bile flow into the duodenum in the absence of a functioning gallbladder facilitates duodenogastric reflux.

Adult↗
PubMed1989

Brachylaima apoplania n. sp. (Digenea: Brachylaimidae) from the Polynesian rat, Rattus exulans (Rodentia: Muridae), in New Zealand: origins and zoogeography.

Brachylaima apoplania n. sp. is described from the small intestine of the Polynesian rat (Rattus exulans) on Tiritiri Matangi Island, New Zealand. The new species is most similar to Brachylaima ratti Baugh, 1962, from Rattus rattus. The two species differ only in morphometric characters, B. apoplania possessing significantly smaller suckers, pharynx, testes, ovary, and cirrus sac. The close resemblance between B. apoplania and B. ratti, the close relationship between their hosts, and archaeological evidence on the origin and early dispersal of R. exulans are used to hypothesize a common Southeast Asian origin for the 2 Brachylaima species. Brachylaima apoplania is believed to have dispersed subsequently throughout the South Pacific islands, along with its rodent host, in the canoes of the ancestors of the modern Polynesians and Maoris.

Animals↗
PubMed1981

A multiaperture collimator for use at 511 keV.

Positron-emitting radionuclides are being used more and more in nuclear medicine. This paper describes a high energy collimator suitable for imaging at 511 keV, the energy emitted by these radionuclides, for use with the Baird Corporation's System 77.

Gamma Rays↗