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Biomedical subjects

G Low

Publications and source records attributed to G Low.

At least 19 recordsLinked to original sources
PubMed2006

Technical inadequacies of peripheral contrast-enhanced magnetic resonance angiography: incidence, causes and management strategies.

AIM: To assess the incidence, causes and effects of technical inadequacies in peripheral contrast-enhanced magnetic resonance angiography (CE-MRA) and to discuss relevant management strategies. MATERIALS AND METHODS: A retrospective analysis of 249 peripheral CE-MRA examinations was performed using the radiology department's RIS/PACS (radiology information system/picture archiving and communication system) database. All failed or technically inadequate MRAs were reviewed. In cases that underwent further imaging by conventional angiography (CA), we assessed if relevant arterial disease had been masked on the MRA. RESULTS: Of the 249 examinations, 215 (86.3%) were technically satisfactory while 34 (13.7%) were a combination of technical inadequacies [29 cases (11.6%)] and examination failures [five cases (2%)]. The causes of technical inadequacies were: (1) venous contamination (13 cases; 5.2%), (2) motion-induced subtraction artefact (eight cases; 3.2%), (3) stent-induced artefact (four cases; 1.6%), (4) inadequate scan coverage (two cases; 0.8%), and (5) contrast timing error (two cases; 0.8%). The causes of failed examinations were: (1) inability to tolerate lying in the scanner (three cases; 1.2%) and (2) inability to fit into the scanner (two cases; 0.8%). Fifteen (44.1%) of the 34 cases underwent further imaging by CA, and in eight of these there was significant arterial disease that was missed on the MRA. CONCLUSION: Technical inadequacies occur in a small but significant proportion of peripheral CE-MRAs and can mask significant arterial disease. Knowledge of the potential causes of technical problems and the relevant management options is important for quality assurance and for limiting the need for an alternative investigation.

Adult↗
PubMed2006

Currarino triad: characteristic appearances on magnetic resonance imaging and plain radiography.

The Currarino triad is a complex anomaly consisting of an anorectal malformation, a sacral bone defect and a presacral mass. It was first described in 1981 and since then, approximately 250 cases have been reported. Radiology has an important part to play in the diagnosis of this entity, as the imaging features are characteristic. We report a case of Currarino triad in an infant who presented with intractable constipation and discuss relevant MRI and plain radiography findings.

Abnormalities, Multiple↗
PubMed2005

Elevated mercury concentrations in fish in lakes in the Mackenzie River Basin: the role of physical, chemical, and biological factors.

During the mid-1990s and through the early 2000s, researchers determined that elevated mercury concentrations were a common occurrence in predatory fish in many lakes in the Mackenzie River Basin (MRB), located in northern Canada. Here we present the results of studies investigating factors contributing to higher mercury concentrations in fish in many of these lakes. Twenty-two percent of lake trout, 33% of northern pike, and 50% of walleye populations had mean mercury concentrations >0.5 microg/g, the guideline for the commercial sale of fish. Higher mercury concentrations were strongly associated with the relatively old age of MRB predatory fish; mean age ranged from 7.6 to 24.9 years for the three species. In contrast, none of the lake trout sampled in eight lakes further south in northern Saskatchewan and Alberta had mean mercury concentrations >0.5 microg/g; fish also were younger (mean age 6 years for the 8 lakes). Mercury concentrations in MRB fish generally increased with fish length, age, and trophic feeding although the nature of these relationships varied with the lake. Mean length was a good predictor of mean mercury concentrations in walleye populations across the study lakes but not for whitefish, lake trout, and pike; age was a good predictor for lake trout and walleye. Mercury concentrations in water and invertebrates were similar to those observed in more southerly regions where fish do not have elevated mercury concentrations. Mercury concentrations tended to be higher in fish in smaller vs. larger lakes and as a probable consequence of higher summer epilimnion temperatures, which favour a higher net methylation rate, and higher mercury and methyl mercury concentrations in water which enter these lakes from the watershed. Increasing fishing pressures on MRB lakes may be a means of reducing mean fish age, improving growth rates, and decreasing mercury body burdens. Increased global warming may result in higher mercury concentrations in fish through increased water temperatures, a longer ice free season, and increased release of stored mercury from the watershed into these lakes.

Age Factors↗
PubMed2005

A history of total mercury in edible muscle of fish from lakes in northern Canada.

Subsistence fishing has been an important source of food for Native People in northern Canada since prehistoric time. Measurements of the levels of mercury in edible muscle of northern fish have been undertaken for over three decades in efforts to evaluate the risks of consuming northern fish. This report summarizes the data obtained from 7974 fish of 25 species from sites distributed from the Yukon to Labrador. The most abundant species were lake trout, lake whitefish, arctic char, walleye, northern pike and burbot. The question being asked was essentially "Are the fish safe to eat?" The results were used to support decisions on fishing and consumption of fish. They were sorted in several ways, into concentration ranges corresponding to human consumption guidelines, into political jurisdictions and into types of bedrock geology. Overall walleye, northern pike and lake trout, usually exceeded the subsistence consumption guideline of 0.2 microg g-1 total mercury and often exceeded the higher guideline of 0.5 microg g-1 total mercury for commercial sales of fish. Mercury in burbot, another facultative predator, was often lower but several still exceeding a guideline. Arctic char collections were mostly from anadromous populations and these had very low levels of mercury, presumably reflecting marine food sources. Lake whitefish were among the cleanest fish examined with 69 of 81 collections falling in the lowest range. Most collections were from sites in sedimentary rock. However a few sites were in metamorphic, intrusive or volcanic rocks and these, taken together, tended to have a higher proportion of sites in the higher ranges of mercury. These results indicate a widespread problem with mercury in subsistence fisheries for predator species of fish with the problem being most problematic for Nunavut.

Animals↗
PubMed2005

Can follow-up radiography for acute scaphoid fracture still be considered a valid investigation?

AIM: To determine whether follow-up radiography is a valid diagnostic investigation in patients with suspected acute scaphoid fractures and normal initial radiographs. MATERIALS AND METHODS: Fifty sets of radiographs (initial and follow-up) were independently assessed by four expert observers for the presence or absence of a scaphoid fracture. Magnetic resonance imaging (MRI), performed in all cases, was used as the gold standard to determine the sensitivity, specificity, positive and negative predictive values of the observers' assessment of the follow-up radiograph. In addition, the reliability among observers of the follow-up radiograph was determined by reliability variance analysis. RESULTS: Of the 50 sets of radiographs, 35 patients had a scaphoid fracture and 15 were normal, as established from MRI report. For individual observer's assessment of the follow-up radiograph, sensitivities of 11, 9, 43 and 49%; specificities of 93, 93, 87 and 80%; positive predictive values of 80, 75, 88 and 85%; and negative predictive values of 31, 30, 39 and 40%. A reliability coefficient of more than 60% is needed for a diagnostic test to be considered reliable. Overall, the inter-observer reliability coefficient was 33%, with pair-wise inter-observer coefficients ranging from 18-53%. CONCLUSION: With poor sensitivity, poor negative predictive value and poor reliability, follow-up radiography cannot be considered a valid diagnostic examination for the detection of scaphoid fracture in patients with normal initial radiographs.

Adolescent↗
PubMed2002

Performance on tests of frontal lobe function reflect general intellectual ability.

Recent studies have indicated that performance on tests of frontal lobe function are highly associated with general intellectual ability (g). Some authors have even claimed that the available evidence does not support a more specific account of frontal lobe function than to provide a general intellectual function for the performance of goal directed tasks. We examined the relationship between performance on the WAIS-R (as a measure of g) and performance on standard tests of frontal lobe function in 123 healthy individuals. Our results demonstrate that in healthy individuals (i) performance on the most popular tests of frontal lobe function shares significant variance, and (ii) a large proportion of that shared variance is highly associated with performance on the Wechsler Adult Intelligence Scales-Revised (WAIS-R), so that the tests are similar to the extent that they measure g. Performance on the Modified Card Sorting Test (MCST), however, is not related to g. The results support the claim that many tests of frontal lobe function measure primarily a non-specific intellectual function but also indicate that some tests, like the MCST, may be assessing more specific cognitive operations.

Adolescent↗
PubMed2000

Childhood trauma, dissociation and self-harming behaviour: a pilot study.

OBJECTIVE: Childhood trauma is known to be an important antecedent in those who engage in deliberate self-harm (DSH). We aimed to explore the mediating mechanisms between childhood trauma and subsequent DSH in a sample of women detained in a high secure setting. METHOD: From a previous incidence study into DSH, we subdivided a group of 50 women as follows: non-harmers (N = 13), infrequent harmers (N = 22) and frequent harmers (N = 15). These three groups were then compared on several measures believed to be associated with DSH. RESULTS: The frequency of DSH was related to low self-esteem, increased dissociation, anger (both inwardly and outwardly directed), impulsivity, and a history of sexual and physical abuse. When these variables were entered into a path analytic model exploring the relationship between childhood trauma and subsequent DSH, two paths emerged: one major path which linked childhood sexual abuse to DSH via increased dissociation and another, more minor association, linking childhood sexual abuse via reduced self-esteem. CONCLUSION: This study shows a strong association between high levels of dissociation and an increased frequency of self-harming behaviour. This association is theoretically plausible and has therapeutic implications.

Adult↗
PubMed1999

Steroid metabolism along the gastrointestinal tract of the cannulated pig.

Steroid metabolism along the gastrointestinal tract of the cannulated pig was studied. Thi was achieved by fitting simple gut cannulas in the terminal ileum, caecum and mid-colon of three Landrace x large white boars, which enabled convenient collection of digesta and faecal samples at defined time points. Biochemical analyses showed that the neutral steroid profile of the pig is similar to that of man, dominated by cholesterol and its bacterial metabolite coprostanol. In contrast, pigs consuming a normal diet excrete appreciably lower quantities of neutral sterols in faeces. The major primary bile acids detected were the glycine and taurine amidates of hyocholic and chenodeoxycholic acids, which were rapidly converted to the free bile acids and subsequently dehydroxylated to hyodeoxycholic and lithocholic acids respectively, in the terminal ileum and caecum. Bacterial deconjugation and 7 alpha-dehyrdoxylation are virtually complete in the caecum with negligible further metabolism in the colon and faeces. On a wet weight basis the concentration of both neutral and acid steroids was shown to increase aborally. Inclusion of dietary fibre in the form of cellulose (Solka floc) and guar gum reduced steroid concentration considerably at all sites of the large intestine, which is consistent with their stool bulking effects. In conclusion, this study shows that intestinal steroid metabolism in the pig is similar to that in man despite slightly different bile acid profiles and, therefore, the multicannulated pig may serve as a useful model of man in chemoprevention studies of colorectal cancer.

Animals↗
PubMed1999

Performance on the Modified Card Sorting Test by normal, healthy individuals: relationship to general intellectual ability and demographic variables.

OBJECTIVES: The aim of this study was to obtain normative data for the Modified Card Sorting Test (MCST), and to examine the relationship between performance on this task, general intellectual ability and demographic variables. DESIGN: A sample of 146 healthy individuals was tested with a demographic distribution (age, sex, socioeconomic class) similar to that of the British population. METHODS: The MCST and the Wechsler Adult Intelligence Scales--Revised were administered to 146 people aged between 16 and 75 years. RESULTS: Most people (56.6%) completed six categories, and many people made perseverative errors. Approximately 8% of the participants made over 50% perseverative errors. Performance on the MCST varied with age, years of education and general intellectual ability. Individuals with a Full Scale Intelligence Quotient (FSIQ) below 100 showed much more variability in performance than individuals with an FSIQ over 100. Detailed percentile norms for the performance on different indices of the test are presented. CONCLUSIONS: The performance of individuals on the MCST is more closely associated with general intellectual ability than with demographic variables.

Adolescent↗
PubMed1991

Estimating the sensitivity of breast cancer screening--experience with the Honolulu BCDDP data.

The 'capture-recapture' models for estimating breast cancer screening sensitivity can be generalized to include factors that affect sensitivity such as cancer size. Including such factors can help reduce the covariance between mammographic and physical exam sensitivity, which will improve the estimates. One model relating sensitivity to cancer length is presented and tested using data from the Honolulu Breast Cancer Detection Demonstration Project (BCDDP). The model predicts sensitivity fairly well for large breast cancers, but underestimates sensitivity for small cancers. Using both mammography and physical examination, the total screening sensitivity is estimated as 0.91 +/- 0.03 for cancers longer than 12 mm (for the second through fifth screenings for Honolulu and Tucson screening data combined). Limited data suggest similar screening sensitivities for Orientals and Caucasians in Hawaii. Shortcomings of the BCDDP data include inaccurate measurements of cancer length. Suggestions to improve data for future work are given.

Breast Neoplasms↗
PubMed1987

Differences between sexes in maximum jaw opening when corrected to body size.

According to linear interincisal measurements, women have a smaller maximum jaw opening than men. In this study the difference was 2.7%. In contrast, epidemiological surveys indicate that women have a greater mobility of joints and generally more joint laxity. Covariate analysis was used to test for the difference between sexes in mean maximum passive opening adjusted according to group mean differences in other parameters of body size. The net result was that the values became more equal between sexes. A second method, employing a geometric estimation for the angle of maximum jaw opening, showed that women had a 5.4% wider range of jaw opening than men (P less than 0.057). This method avoided the problem of considering relative body size and body factors which generally correlated poorly with maximum opening. It should be noted that an increased range of opening is a measure of hyperextensibility and does not necessarily imply laxity or instability.

Adult↗
PubMed1987

Physicians' non-compliance with patients' refusal of life-sustaining treatment.

Should patients be treated when they have specifically refused treatment? Three competent patients are described with end-stage renal disease who, against the advice of their family, friends and care-givers, refused dialysis. Each was treated and subsequently they acknowledged their satisfaction with the outcome. Guidelines for treating patients when consent is refused are discussed and it is suggested that this is permissible in life-saving situations where the patients' refusal is idiosyncratic and irrational.

Adult↗
PubMed1987

The multicompetent practitioner: a needs analysis in an urban area.

This study examined the concept of the multicompetent practitioner - the health care worker trained in more than one specialty - as one way of meeting the changing needs of the health care system. Seventy-four hospital administrators, 74 directors of nursing, 14 directors of community health organizations, and 12 private physicians from the Philadelphia metropolitan area were surveyed to explore the feasibility of developing and using multicompetent practitioners at their participating institutions. The results indicated that multicompetent practitioners are already working in some institutions and that there is a willingness to hire this new type of health care worker. How the multicompetent practitioner fits into the institution, the level of education required beyond the original area of skill, and the question of salary were included in the survey. Findings also indicate positive support for the development of multicompetent practitioner training within allied health educational programs.

Allied Health Personnel↗