Search PubMed⌕ Search

Biomedical subjects

K D Rogers

Publications and source records attributed to K D Rogers.

At least 19 recordsLinked to original sources
PubMed2006

Model fitting in two dimensions to small angle diffraction patterns from soft tissue.

In our research programme small angle x-ray scattering (SAXS) is used to provide information on the axial arrangement of collagen molecules as well as data about the state of other components of the extra cellular matrix (ECM) in human tissues. Derivation of parameters to describe and simplify the data is required for much of the SAXS patterns analysis. A method is presented here to achieve function fitting to collagen diffraction peaks along with a representation of the underlying diffuse scatter. A simple model was used which proved reliable in fitting a variety of 2D diffraction patterns. The logarithm of the scatter intensity over the area of the scatter image was taken to reduce the range and improve fitting accuracy. Our model was then used to fit the log data. The model consisted of a radial exponential diffuse scatter component added to a specified number of Gaussian peaks. In 2D the peak model is toroidal, each component being rotated about a common specified centre. Initial search parameters from a 1D averaged sector were supplied to the iterative 2D fitting routine. With the aid of data weighting and basic wavelet filtering, successful and reliable fitting of a specified 2D model to real data is achievable. The process is easily automated. Multiple SAXS patterns can be fitted without operator intervention. As described the model is simple enough to converge rapidly and yet allows image data to be parameterized to a form suitable for extracting the requisite information. The fitting method is flexible enough to be extended to achieve a more comprehensive and complex pattern fitting in two dimensions if this turns out to be necessary. It is our intention to implement orientation distribution functions in the near future by including an angular scaling factor.

Animals↗
PubMed2005

A preliminary study of breast cancer diagnosis using laboratory based small angle x-ray scattering.

Breast tissue collected from tumour samples and normal tissue from bi-lateral mastectomy procedures were examined using small angle x-ray scattering. Previous work has indicated that breast tissue disease diagnosis could be performed using small angle x-ray scattering (SAXS) from a synchrotron radiation source. The technique would be more useful to health services if it could be made to work using a conventional x-ray source. Consistent and reliable differences in x-ray scatter distributions were observed between samples from normal and tumour tissue samples using the laboratory based 'SAXSess' system. Albeit from a small number of samples, a sensitivity of 100% was obtained. This result encourages us to pursue the implementation of SAXS as a laboratory based diagnosis technique.

Algorithms↗
PubMed2004

Determination of depth-dependent diffraction data: a new approach.

A direct method for determining powder diffraction data at specific depths from angle-dependent diffraction data is described. The method is non-destructive and only traditional data collections, where the angle of incidence is varied, are required. These angle-dependent spectra are transformed to give diffraction data arising from different depths, which may then be exploited using any conventional method. This is a novel approach as traditional methods are forced to tolerate the inherent depth averaging of grazing-angle diffraction, or only examine specific structural characteristics. In order to obtain depth-dependent X-ray diffraction data, a Fredholm integral equation of the first kind is solved using regularization techniques. The method has been validated by the generation of pseudo-experimental data having known depth profiles and solving the Fredholm integral equation to recover the solution. The method has also been applied to experimental data from a number of thin film systems.

Journal Article↗
PubMed2003

X-ray refraction effects: application to the imaging of biological tissues.

The purpose of this study was to explore the potential of refraction contrast X-ray imaging of biological tissues. Images of dissected mouse lungs, heart, liver and legs were produced using the medical beamline at the Elettra Synchrotron at Trieste, Italy. The technique used was diffraction enhanced imaging. This utilizes a silicon crystal positioned between the tissue sample and the detector to separate refracted X-rays from transmitted and scattered radiation by Bragg diffraction. The contrast in the images produced is related to changes in the X-ray refractive index of the tissues, resulting in remarkable clarity compared with conventional X-ray images based on absorption effects. These changes were greatest at the boundaries between different tissues, giving a marked edge enhancement effect and three-dimensional appearance to the images. The technique provides a way of imaging a property of biological tissues not yet exploited, and further studies are planned to identify specific applications in medical imaging.

Animals↗
PubMed2003

Effect of foot balance on the intra-articular pressure in the distal interphalangeal joint in vitro.

REASONS FOR PERFORMING STUDY: Increased joint pressure has been implicated in the progression of osteoarthritis. HYPOTHESIS: That intra-articular pressure in the distal interphalangeal joint (DIP) is significantly higher in legs loaded with heel up (HU), low heel (TU), lateral side up (LU) and medial side up (MU) imbalance compared to the balanced position. METHODS: Twelve elbow down limbs were compressed in a hydraulic loading jig and DIP pressure measured. RESULTS: Elevating the heels by 5 degrees significantly increased DIP pressure. After 5 ml of contrast was injected into the joint, heel elevation caused a greater increase in DIP pressure and heel lowering decreased DIP pressure. Silicone rubber castings were taken of 20 DIP whilst under load. The articular contact area was localised on the dorsal aspect in the HU position, palmar aspect in the TU position and towards the elevated side with lateromedial imbalance. CONCLUSIONS: Altered foot orientation, which could result from trimming and shoeing, therefore influences intra-articular pressure in the DIP and the articular contact area. POTENTIAL CLINICAL RELEVANCE: The results support the view that a balanced foot is the ideal and that the elevated heels may be detrimental to long term viability of the DIP joint.

Abattoirs↗
PubMed2002

An X-ray diffraction study of the effects of heat treatment on bone mineral microstructure.

A series of human cortical bone specimens has been heated to temperatures up to 1200 degrees C and the mineral content examined in detail by X-ray diffraction. Line profile analysis of the diffraction data has been undertaken to characterise the microstructural (crystallite size and microstrain) features of the mineral at each temperature. Individual profile fitting of several maxima from each diffractogram has also provided precise lattice parameters of the apatite at each temperature. The apatite did not show any significant decomposition over the temperature range although CaO was increasingly formed at temperatures above 600 degrees C. Both finite crystallite size and microstrain contributed significantly to the diffraction peak broadening below 600 degrees C. When heated to > 800 degrees C, the small, rod-like mineral crystallites changed from a highly anisotropically strained state to one with significantly larger equidimensional crystals possessing little microstrain. The findings are discussed in the context of graft bone substitutes and surgical heating of bone.

Adult↗
PubMed2000

Breast cancer diagnosis using scattered X-rays.

Small-angle X-ray diffraction data has been collected from 99 ;core-cut' breast tissue specimens representing a number of different pathologies. Data in the range 75-1390 A have been compared with controls from patients with no breast disease. Bessel functions and Bragg maxima resulting from the fibrillar structure of collagen have been identified. The Bragg maxima indexed onto a 649 A lattice. Systematic differences in the intensities and D-spacings between the collagen of malignant, benign and normal tissue groups have been clearly demonstrated and quantified. These differences appear to be due to a significantly lower structural order within the malignant tissues. Possible explanations for this are discussed and the potential for utilizing this observation in cancer diagnosis is considered.

Journal Article↗
PubMed1993

Intra- and interobserver variability in interpretation of DMSA scans using a set of standardized criteria.

A set of criteria was developed to standardize assessment of DMSA renal scintigraphy which were performed to evaluate children for acute pyelonephritis and renal scarring. This study was undertaken to assess intra- and interobserver variability in the interpretation of DMSA renal scintigraphy using these criteria. Renal contours and parenchyma were assessed in three zones. Contours were assessed as normal or abnormal and parenchymal defects were evaluated in terms of character, shape and degree in three regions (upper and lower pole and midzone). Two nuclear medicine physicians blindly reviewed 57 DMSA scintigraphy on two occasions each. Disagreement of each observer's evaluation of the same scintigraphy on two different occasions was described as intraobserver variability, and the comparison between readings by each of the two observers was described as interobserver variability. High levels of intra- (95.9% and 90.6% respectively, p < 0.05) and interobserver agreement (84.4%, p < 0.05) were demonstrated. There were minor differences in inconsistencies between the two kidneys or different kidney zones. We conclude that standardization of criteria resulted in higher intra- and interobserver consistency in interpretation of DMSA scintigraphy.

Acute Disease↗
PubMed1990

Efficacy of adenoidectomy for recurrent otitis media in children previously treated with tympanostomy-tube placement. Results of parallel randomized and nonrandomized trials.

We studied the efficacy of adenoidectomy in 213 children who had received tympanostomy-tube placement because of persistent and/or recurrent otitis media and had again developed otitis media after tubal extrusion. Ninety-nine of the children were assigned randomly to either an adenoidectomy group or a control group; in a separate trial, 114 children whose parents withheld consent for randomization were assigned according to parental preference. In both trials, control group outcomes appeared to have been biased favorably by the withdrawal of certain severely affected subjects from control status to receive adenoidectomy. Nonetheless, in both trials, adenoidectomy group outcomes were more favorable than control group outcomes during the first 2 follow-up years. Statistically significant differences were found mainly in the randomized trial, where during the first and second years, respectively, adenoidectomy subjects had 47% and 37% less time with otitis media than control subjects and 28% and 35% fewer suppurative (acute) episodes than control subjects. We conclude that adenoidectomy is warranted on an individualized basis for children who develop recurrent otitis media after extrusion of tympanostomy tubes.

Adenoidectomy↗
PubMed1990

Disability from bicycle-related injuries in children.

Bicycle crashes are a major cause of injuries in childhood. The goal of this study was to determine the long-term disabilities caused by bicycle-related injuries, and to clarify the long-term treatment priorities of injured children. Hospital records of 372 children (ages 2-15 yr, median 9 yr; 232 boys and 140 girls) admitted with bicycle-related injuries from 1979 through 1986 provided clinical information, social service visits, in-hospital and outpatient rehabilitative interventions, and physical status at discharge. More complete evaluations were made by contacting parents by telephone (82 children), and by personal interview and physical examinations (27). Head injuries predominated (69.1%). Twelve (3.2%) died, all from major head injuries. Four suffered permanent severe impairment from cervical spinal injuries and head injuries and remain institutionalized (1.4%). One third had a persistent disability noted at the time of discharge in the medical record (33.6%), reported by telephone interview (31.7%), or confirmed by physical examination (37.0%). Still, only 11.0% received physical therapy consultations during hospitalization, and 22.8% received social service assistance. Only 39.0% were seen by a surgeon or pediatrician after discharge, and few (7.3%) received outpatient physical therapy. Cognitive or behavior changes were noted in 31.7%, many noting changes in school performance (worse in 20.7%), behavior (13.4%), and sleep, particularly nightmares (34.1%). Recurrent injuries occurred in 52 children (14.4%), of whom ten (2.8%) required further hospital admission. Bicycle-related injuries cause significant short- and long-term disabilities among children.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1989

Status of scrap (recyclable) dental amalgams as environmental health hazards or toxic substances.

This article presents information garnered after an investigation by the Environmental Protection Agency in 1987 of dentists and others who had sold scrap dental amalgam to refiners who had "arranged for the disposal or treatment ... of hazardous substances," and were responsible for adverse consequences associated with their subsequent management and refining. Information about the health hazard status of scrap dental amalgams was obtained by: interviews with toxicologists, review of published lists of toxic and hazardous materials, and survey of biomedical publications (1977 through 1987) concerning toxicity or health hazards associated with dental amalgams. The conclusions were that scrap dental amalgam is not: a waste substance to be disposed of, but is a product of commercial value; identified or regulated by the Environmental Protection Agency, the Occupational Safety and Health Administration, the Department of Transportation, the Food and Drug Administration, the National Institute of Occupational Safety and Health, the US Public Health Service, or the Centers for Disease Control as an environmental health hazard or toxic substance; identified by toxicologists and persons responsible for solid waste regulation as a toxic substance or environmental health hazard; nor proved by scientific study to be toxic or hazardous in the manner and form in which it is collected and stored by dentists and subsequently sold to metal refiners.

American Dental Association↗
PubMed1987

Variation in repeat rates between 18 radiology departments.

A comprehensive analysis of repeat rates has been obtained from an observational study of radiological practice in diagnostic X-ray departments throughout Wales. Interdepartmental and intradepartmental repeat rates are investigated for chest, abdomen, pelvis, sinus, lumbar spine, cervical spine and intravenous pyelographic examinations. The confounding effects upon observed repeat rates of trainee practitioners and automatic exposure control devices are also considered. The overall proportions of total film cost and patient exposure attributable to repeat radiographs are estimated to be 10% and 14% respectively.

Hospital Departments↗
PubMed1986

School performance characteristics preceding onset of smoking in high school students.

The cigarette smoking status of 1,442 high school students was determined by questionnaire. Of the respondents (smoking and nonsmoking), 60% had been enrolled in the same school system during elementary school. Thus, records were available of school absence, grades, achievement tests, and IQ tests during elementary school, prior to the time when the smokers had commenced the practice. Smoking in high school was significantly related to high absence rates, low achievement test scores, and low grade point averages during elementary school years, prior to the onset of smoking. The IQ was not significantly different in the third grade among pupils who became smokers in high school and those who did not, but sixth-grade IQ scores were significantly lower in students who later identified themselves as smokers. Although smokers demonstrated these characteristics prior to beginning smoking, the differences were not large enough to predict which elementary school students would become high school smokers. The findings support the view that smoking and these school-related characteristics may both be part of a "smoker life-style."

Absenteeism↗
PubMed1986

Physical maturity and outcome of pregnancy in primiparas younger than 16 years of age.

The association of complications and adverse outcomes of early teenage pregnancy with physical growth maturation of mothers was studied in subjects identified from review of medical records in a Pittsburgh obstetrical hospital from 1970 through 1977. Five groups were used to categorize the subjects: (1) 449 primiparas younger than 16 years of age, (2) 347 primiparas 20 to 24 years of age, pair-matched with subjects in group 1 by race, hospital service status, sex of infant, trimester of first prenatal visit, and year of delivery within 5 years, (3) 139 group 1 mothers at the time of their second delivery, (4) 104 group 1 primiparas whose postmenarcheal age was less than or equal to 2.6 years at delivery, and (5) 108 group 1 primiparas whose postmenarcheal age was greater than or equal to 4.1 years at delivery. Subjects in groups 1 and 2, first and second pregnancies of subjects in group 3, and subjects in groups 4 and 5 were compared for prepregnancy weight and height, weight gain during pregnancy, complications of pregnancy, birth weight and gestational age of infant, and perinatal morbidity and mortality. Although primiparas younger than 16 years of age had not achieved mature height and weight, no relationship between mother's physical growth maturation and adverse pregnancy course or outcome was demonstrated.

Adolescent↗