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D McLean

Publications and source records attributed to D McLean.

At least 37 records · Page 2Linked to original sources
PubMed2001

Safety and reproducibility of sputum induction in asthmatic subjects in a multicenter study.

The safety of sputum induction and the reproducibility of measurements in induced sputum in multicenter studies is unknown. We examined the safety of sputum induction in a two-visit, six-center study in 79 subjects with moderate to severe asthma (mean +/- SD FEV(1) 71 +/- 12% predicted, 67% taking inhaled corticosteroids). In addition, we compared the reproducibility of markers of inflammation in induced sputum with the reproducibility of the FEV(1) and the methacholine PC(20). The FEV(1) decreased > or = 20% from the postbronchodilator baseline in 14% of all subjects and in 25% of subjects whose initial prebronchodilator baseline was 40 to 60% of predicted. All subjects responded promptly to additional albuterol treatment, and no subject developed refractory bronchoconstriction requiring treatment other than reversal of bronchospasm in the study laboratory. The reproducibility of measurements of the eosinophil percentage, eosinophil cationic protein, tryptase, and methacholine PC(20) were similar (concordance correlation coefficients of 0.74, 0.81, 0.79, and 0.74, respectively), without any significant among-center effect. We conclude that sputum induction can be performed safely in subjects with moderate to severe asthma in multicenter clinical trials when carried out under carefully monitored conditions. Importantly, we demonstrate that measurement of markers of inflammation in induced sputum is as reproducible as methacholine PC(20) and should prove useful in the assessment of airway inflammation in multicenter clinical trials.

Aged↗
PubMed2001

AmpFlSTR Profiler Plus and AmpFlSTR COfiler analysis of tissues stored in GenoFix, a new tissue preservation solution for mass disaster DNA identification.

A preliminary study was conducted to assess the capability of a new alcohol-based tissue fixative, GenoFix, to preserve DNA from biopsy tissues stored at room temperature and/or -20 degrees C in a freezer, for subsequent short tandem repeat (STR) DNA typing analysis. Fresh human smooth muscle samples were stored at room temperature in GenoFix for one month and up to one year and seven months before being processed using the megaplex STR systems, AmpFlSTR Profiler Plus and AmpFlSTR COfiler. Alternatively, muscle tissues in GenoFix were placed at -20 degrees C in a freezer for up to 3 1/2 years following two to three months in the fixative at room temperature. DNA analysis was also carried out on tissues stored in GenoFix for one month at room temperature and subsequently paraffin-embedded and stored at room temperature for four years. The AmpFlSTR Profiler Plus and AmpFlSTR COfiler STR profiles produced, using DNA extracted from all fixed tissue samples, were of very good quality. The fluorescent signals were well balanced across the nine STR loci or six loci comprised in the megaplexes surveyed and profiles showed no differences with those observed for the control blood of the respective donor patients. Continuous exposure to GenoFix at room temperature (up to one year and seven months) did not compromise the STR typing analysis of the fixed tissues. No adverse effects were noted on the STR typeability of tissues fixed with GenoFix and stored at -20 degrees C in a freezer for up to 3 1/2 years. STR profiles generated from the paraffin-embedded tissues fixed in GenoFix were of excellent quality. This preliminary study suggests that GenoFix can be used to store tissue samples at room temperature for up to one year and seven months or at -20 degrees C in a freezer for longer storage (up to 3 1/2 years). This new and odorless tissue fixative promotes tissue and DNA preservation in a very effective manner and as such may prove useful in criminal investigations or mass disaster identifications carried out in remote locations and in which a small or large number of tissue samples are collected for further analyses.

Biopsy↗
PubMed2000

Changes in work practice after a respiratory health survey among welders in New Zealand.

AIMS: To assess changes in work practice among eight New Zealand engineering sites, following a study of occupational respiratory symptoms in welders two years previously. METHODS: In 1996, we found that an acute decrease in lung function was more common in welders working without local exhaust ventilation. Findings were reported back to management, study participants and the media. Two years later we re-visited the eight welding sites. RESULTS: Of the eight engineering sites, two had local exhaust ventilation present in both Study 1 and Study 2, one site had installed local exhaust ventilation in part of the site since Study 1 and one site had moved to larger premises. The remaining four sites had no exhaust ventilation or change to the workplace between studies. Five welders (12.8%) used respiratory protection in both Study 1 and Study 2, seven welders (18%) used respiratory protection in Study 1 but not Study 2, four welders (10.3%) did not have respiratory protection in Study 1 but did in Study 2 and nine welders (23.1%) did not use respiratory protection at all in Study 1 or Study 2. CONCLUSION: Further effort is required to ensure that such studies lead to significant improvements in the work environment.

Air Pollutants, Occupational↗
PubMed2000

Worker exposures to airborne dust, endotoxin and beta(1,3)-glucan in two New Zealand sawmills.

BACKGROUND: Sawmill workers have an increased risk of developing occupational asthma and other respiratory symptoms. Wood dust and microorganisms have both been suggested to play a role, but few studies have measured microbial exposure levels in sawmills. METHODS: The preliminary study reported in this paper assessed airborne dust, bacterial endotoxin and beta(1,3)-glucan levels in 37 samples from two New Zealand sawmills. RESULTS: Nearly one-third of the measured dust levels exceeded 1 mg/m(3) and only one sample exceeded the legal limit of 5 mg/m(3). Endotoxin levels were clearly elevated with 50% of all measured exposures above 50 EU/m(3) (range: 7-588 EU/m(3)). beta(1,3)-glucan levels were comparable with levels measured in other industries where workers are exposed to organic dust. Workers in the planing department had the highest mean exposures to dust, endotoxin and beta(1,3)-glucan. Dust levels were only weakly correlated with endotoxin and beta(1,3)-glucan levels. CONCLUSIONS: Endotoxin exposures in sawmill workers are at levels sufficient to potentially contribute to the development of respiratory symptoms. Moreover, measurement of dust exposure is a poor proxy for beta(1,3)-glucan and endotoxin exposure in sawmill workers.

Dust↗
PubMed2000

Film based scatter measurement in mammography.

Film based measurements of scatter to primary ratio (s/p) have been made using the "beam stop" technique. Phantom material, radiographically equivalent to 100% glandular tissue, 100% adipose tissue and 50% glandular: 50% adipose tissue was used. These measurements have been made at 25 and 28 kVp for non grid and 28 and 30 kVp with grid for phantom thicknesses varying from 3 cm to 7 cm and 'D shaped' field sizes varying from 80 to 290 cm2. Results indicate that s/p is predominantly uniform across a mammographic image with a reduction towards the edge of the phantom. The values for s/p agree with previously published values determined from Monte Carlo calculation. Scatter primary ratio was found to be directly proportional to phantom thickness with little effect from field size. The effect of beam energy was significant in the non-grid case but reduced in significance with the use of a grid. The average measurement error was estimated at 4.5%. No variation in scatter primary ratio was detected between glandular and adipose phantom materials in this study.

Female↗
PubMed1999

Survey of mammographic cassette light output.

The purpose of the present paper was to assess the variation in light output from clinical mammographic screens, particularly in relationship to age and radiographic usage. The light output from 156 mammographic cassettes from 17 clinical centres was measured on site using a novel light detector. Survey information on cassette age and usage was collected. Where possible, screen manufacture date was supplied by the vendor. One cassette from each centre was measured at a standard laboratory to allow normalization of all measurements. Three centres were found to have cassettes in clinical use whose light outputs varied by an amount incompatible with current Royal Australasian College of Radiologists (RACR) standards. These centres used cassettes whose ages varied widely. No correlation between light output and radiographic usage was found. Older cassettes were found to have a slight increase in light output. A small reduction of light output was measured between screen regions of high and low radiation exposure histories. Replacement of mammographic screens should not be based on an expectation of light output reduction due to age or usage. Rather, all mammographic screens should be replaced simultaneously as indicated by factors such as failure of screen-film contact or the presence of screen-related image artefacts.

Humans↗
PubMed1999

Investigation of thyroid dose due to mammography.

The radiation dose to the skin overlying the thyroid was measured for 91 women undergoing routine mammographic screening. Measurement was made over 6 days using thermoluminescent dosimeter (TLD) detectors taped appropriately to the neck. An average skin dose of 0.39 +/- 0.22 mGy per mammographic examination was measured with measurements ranging from background levels to 1.15 mGy. The average dose was significantly correlated to the milliampere-seconds for a total procedure. The mediolateral-oblique view was found to give a 2.4-fold greater skin dose at the thyroid than the craniocaudal view. After considering depth dose data from the literature it was conservatively estimated that the dose to the thyroid gland might be 10% of the skin dose overlying the thyroid. This corresponds to an average thyroid dose during mammography of approximately 0.04 mGy which is considered insignificant compared with the average breast dose (4 mGy) and in light of the relevant available literature on the risk to the thyroid.

Female↗
PubMed1999

Resolution degradation due to K-characteristic photon absorption in dual phosphor image receptors.

Image receptors based on the absorption of x rays by phosphor screens have a system resolution described predominantly by the modulation transfer function (MTF) of the phosphor screens utilized. This ideal MTF is modified by the presence of secondary effects within the imaging receptor such as scatter from the receptor cover, visible light crossover (in the case of screen film cassettes) and scatter generated within the phosphor itself, presumed to be almost entirely due to photoelectric interactions. In this paper the MTF characteristics resulting from the absorption of K-characteristic x rays emitted by one screen of a pair in an image receptor and absorbed by the adjacent screen (referred to as cross-fluorescence hereafter) are examined. This effect has been previously modeled [Med. Phys. 23, 1253 (1996)] and recently a computer program has been written to calculate intensity of the radial component of a point spread function (PSF) describing the above process. From this, the MTF of cross-fluorescence under varying conditions can be calculated. The model was applied to a dual screen experiment described in the literature [Med. Phys. 23, 871 (1996)], from which it was possible to show good agreement between calculated results and those derived from the measurement. The effect of screen thickness, screen separation, and phosphor material on the MTF of cross-fluorescence was investigated using simulated x-ray beam spectra in association with phosphor screen parameters. Results showed that the calculated MTF falls to below 0.1 at 1 cy/mm in all cases examined. This MTF was reduced further as the separation between the screens increased from that commonly used in a screen film cassette. Beam energy, phosphor thickness, and phosphor material had a minimal or no effect on MTF. The effect of cross-fluorescence on total image receptor MTF is to reduce the high-frequency components of that function by an amount that is in proportion to the scatter fraction of the effect.

Calibration↗
PubMed1998

Blepharophimosis, hypoplastic radius, hypoplastic left heart, telecanthus, hydronephrosis, fused metacarpals, and "prehensile" halluces: a new syndrome?

We report on the prenatal ultrasound and postnatal findings in an infant born to a healthy, nonconsanguineous couple. The infant had microcephaly, telecanthus, blepharophimosis, cleft palate, micrognathia, abnormally modeled ears, hypoplastic left heart, hypoplastic radii and ulnae with radial subluxation, pseudoarthrotic distal humeri, fused metacarpals, tibial bowing, unusual feet with long halluces, hydronephrosis, patent urachus, abnormal electroencephalogram, and normal karyotype. To our knowledge, this combination of anomalies has not been recognized previously and may represent a new condition.

Adult↗
PubMed1998

Clinical evaluation of twin screen-film chest radiography: cost effective lung and mediastinal imaging.

OBJECTIVE: A new twin screen-film cassette system optimised for conventional chest radiography was evaluated by four thoracic radiologists. MATERIALS AND METHODS: The twin screen-film cassette system produces two film images, the front film optimised for the mediastinal region of the chest, the rear for the lung region. Image degradation on either screen-film system due to internal photon scatter has been virtually eliminated due to the use of a dividing filter. Fifty patients were included in a trial that resulted in a set of chest images for each patient, taken on the same inspiration, by both the twin screen-film cassette and the conventional system. The resultant fifty sets of images were evaluated by four chest radiologists who scored 12 radiographic features of the chest and patient pathologies present, using a paired difference technique. RESULTS: The image quality of the twin screen-film cassette system was judged to be significantly superior to the conventional screen-film system in nine of the 12 radiographic features scored (P < 0.003). In the three other regions and for the patient pathologies, no significant conclusions were drawn. CONCLUSION: The new twin screen-film system showed improved visualisation of radiographic features, particularly in the mediastinal and retrocardiac lung regions. This new system shows promise in both standard and portable clinical applications.

Cost-Benefit Analysis↗
PubMed1998

Technical aspects of twin screen-film chest radiography: cost effective lung and mediastinal imaging.

OBJECTIVE: To determine the sensitometry and 'cross-talk' of a twin screen-film cassette and to assess its clinical potential. MATERIALS AND METHODS: The twin cassette utilises two sets of screens, divided by filter material, to provide an optimised image of the mediastinum and the lungs. The exposure difference for the two images was measured sensitometrically. The contribution to film density of visible light and K-characteristic radiation, from adjacent screens in the absence of a dividing filter, was investigated. RESULT: Clinical experience indicated that an exposure difference of 3.4 between the front and back screens, was optimal. Visible light and K-characteristic radiation from the front screens, contributed up to 20 and 24% respectively, of the back film exposure and screen absorbed energy respectively. This was reduced to 0 and 6% with the use of the filter. CONCLUSIONS: The twin screen-film cassette provides extended latitude to enable optimal visualisation of the lung and mediastinal regions. Adjacent screen 'cross-talk' has been overcome to allow standard and portable chest applications.

Absorption↗
PubMed1998

Miyoshi myopathy in Saudi Arabia: clinical, electrophysiological, histopathological and radiological features.

Miyoshi myopathy (MM) is a rare autosomal recessive distal myopathy linked to chromosome 2p12-14 that has not been described in Saudi Arabia. A Saudi family with five siblings aged 3-25 years, an unrelated 18-year-old woman and a 40-year-old man with MM were identified. All patients underwent a neurological examination, serum chemistry, electromyography and MRI of the legs. Four patients underwent a muscle biopsy that was processed for routine enzyme histochemistry and immunocytochemical analyses for dystrophin and adhalin (alpha-sarcoglycan). The two sporadic and two familial cases showed classic findings of MM, including early adult onset, preferential involvement of gastrocnemius muscles, markedly elevated serum creatine kinase levels and dystrophic-appearing muscle without vacuoles. Magnetic resonance imaging revealed selective involvement of the posterior compartment muscles and myoedema by STIR sequences. The remaining three familial cases had elevated serum creatine kinase levels and two also had early myopathic findings by EMG suggestive of MM.

Adolescent↗
PubMed1998

Secondary photon scatter in imaging cassettes.

Secondary photon processes within a cassette image receptor have been identified in the literature for at least three decades. These secondary processes have varying effects on the contrast, resolution and noise of a resulting radiographic image. The magnitude of these effects can be quantified in terms of the percentage of scatter to total absorbed energy for each process recorded by the radiographic cassette, and also as a reduction in system MTF. Two of these processes, cassette face scatter and particularly film crossover, have been subject to considerable past study. The third, due to K-characteristic photon 'crossover', has only recently been quantified. The total magnitude of all secondary cassette effects for a radiographic image, could vary from a worst case where in excess of 40% of the total absorbed energy is due to secondary processes (for an aluminium cassette with Gd2O2S screen with high crossover film, exposed at high kVp) to a best case of less than 10% (for a carbon fibre cassette, tantilate screens with 'zero crossover' film) leading to corresponding contrast reductions of > 40% to < 10% respectively. The MTF components of all secondary effects have been determined and are shown to decrease rapidly with increasing spatial frequency. This results in the MTF of the total image receptor system being reduced for high spatial frequencies by the same percentage as the contrast reduction. Theory predicts that the affected image noise due to cassette secondary processes will be complex and vary with spatial frequency.

Biophysical Phenomena↗