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Biomedical subjects

D Keating

Publications and source records attributed to D Keating.

At least 19 recordsLinked to original sources
PubMed1999

Ability of mammography to reveal nonpalpable breast cancer in women with palpable breast masses.

OBJECTIVE: Our goal was to determine the frequency with which mammography reveals nonpalpable malignancies in women with benign palpable masses and to compare these nonpalpable malignancies with the palpable malignancies and nonpalpable malignancies detected in asymptomatic women. SUBJECTS AND METHODS: This study of nominally asymptomatic women involved 85,399 consecutive mammographic examinations, of which 3459 (4.1%) examinations were performed on women who had palpable masses identified before or at the time of mammography. A medical outcomes audit identified mammographic examinations after which breast cancer was diagnosed and determined selected surrogate measures for mortality reduction for the mammographically detected malignancies. RESULTS: Of the 3459 examinations in women with palpable masses, 64 cases of cancer were revealed by mammography. Of these, 54 cases involved palpable malignancies (15.6/1000 examinations) and 10 involved nonpalpable malignancies (2.6/1000 examinations). Of the 81,940 examinations in asymptomatic women, 346 cases of nonpalpable cancer were detected (4.2/1000 examinations). Of the 10 cases of nonpalpable cancer detected in women with benign palpable masses, median tumor size was 13.8 mm, 10% had axillary node metastasis, and 10% were stage 2 or higher. The corresponding surrogate measures for cases of nonpalpable cancer detected in asymptomatic women were median tumor size, 13.6 mm; node metastasis, 7%; stage 2 or higher, 14%. The surrogate measures for the 54 palpable malignancies were median tumor size, 23.7 mm; node metastasis, 31%; stage 2 or higher, 63%. CONCLUSION: The surrogate measures for the nonpalpable malignancies in women with benign palpable lesions resemble those in asymptomatic women and are much more favorable than those of palpable malignancies. Therefore, in women with a palpable breast mass, it is important to use mammography to screen the remainder of both breasts for nonpalpable cancer.

Adult↗
PubMed1998

Paediatricians: referral rates and speech pathology waiting lists.

OBJECTIVE: This study aimed to examine paediatricians' training in and understanding of communication development and disabilities and their attitudes to speech pathology waiting lists and management practices. The relationship between these factors and referral rates was also investigated. METHODOLOGY: A total of 229 paediatricians registered with the Australian College of Paediatrics participated in the study in November 1996. They answered 15 multiple-choice questions designed to collect demographic information and data pertaining to their training and understanding of communication development and disabilities. The survey also obtained data on referral rates to public and private speech pathology services and on paediatricians' perceptions of speech pathology waiting lists and possible management strategies. RESULTS: Referral rate to public and private speech pathology services was found to be associated with the quality of paediatricians' training in and knowledge of communication development and disabilities. Paediatricians who had regular contact with speech pathologists were also more likely to make more referrals. Waiting lists had a negative influence on referral rate. Treatment rather than assessment waiting lists were preferred. Paediatricians believed the best solution to speech pathology waiting lists was an increase in staffing levels particularly in community health centres. Respondents reported that 1-4 months was an acceptable time to wait for speech pathology care and indicated the order of importance of factors for prioritising children. CONCLUSIONS: The results have important implications for developing best practice models for improving referral processes and access to speech pathology services for children with communication disabilities.

Australia↗
PubMed1997

Electroretinography of central retinal vein occlusion under scotopic and photopic conditions: what to measure?

INTRODUCTION: In the management of cases of central retinal vein occlusion it is important to identify those patients who will develop the complication of iris neovascularisation. Electroretinography is of proven use in this role but there is some confusion about which parameters to measure and at what stimulus intensities. METHODS: A variety of ERG parameters in scotopic and photopic conditions were tested by ROC analysis for the prediction of the development of this complication in 39 patients with CRVO. RESULTS: The results indicated that a single flash and measurement of the b/a ratio under photopic conditions is as effective in this aim as measuring multiple parameters. CONCLUSION: A simplified and shortened protocol could be used in the examination of this condition thereby making the application of ERG more practical in the clinical setting.

Adaptation, Ocular↗
PubMed1997

Lamotrigine for pain with hyperalgesia.

Pain associated with hyperalgesia of the affected area occurs in a number of conditions. We describe our experience of using the drug Lamotrigine in the management of this pain in 3 individuals with Phantom limb pain and stump hypersensitivity Post herpetic neuralgia and causalgia respectively. We discuss the mechanism of action of the drug and why possibly it renders it effective in this form of pain.

Aged↗
PubMed1996

Implications of the emerging home systems technologies for rehabilitation.

This paper gives a review of the current and anticipated developments in Integrated Home Systems and raises the implications these have in the field of rehabilitation. Firstly, the systems under consideration are defined and their development world-wide outlined. An overview of the European Home Systems Specification is given. The implications of this technology for rehabilitation are then raised considering: environmental control in the home; how people with degenerative conditions may be more readily able to remain in their homes as condition progresses; and remote health monitoring. The expectation that the initial impact will be in the area of environment control is stated, and a closer look at this field is made comparing current with anticipated systems. An outline is given of the TIDE Project HS-ADEPT (Home Systems--Access for Disabled and Elderly People to this Technology). The key findings of the survey of users made at the outset of the project, relevant to this paper, are given. The ongoing work of the project is described in brief. The continuing developments in Integrated Home Systems and in particular the issue of standards are noted. Concluding comments are offered in the hope of stimulating the necessary interdisciplinary discussion if this technology is to realize its full potential in the field of rehabilitation.

Electronics, Medical↗
PubMed1996

Automatic detection of diabetic retinopathy using an artificial neural network: a screening tool.

AIMS: To determine if neural networks can detect diabetic features in fundus images and compare the network against an ophthalmologist screening a set of fundus images. METHODS: 147 diabetic and 32 normal images were captured from a fundus camera, stored on computer, and analysed using a back propagation neural network. The network was trained to recognise features in the retinal image. The effects of digital filtering techniques and different network variables were assessed. 200 diabetic and 101 normal images were then randomised and used to evaluate the network's performance for the detection of diabetic retinopathy against an ophthalmologist. RESULTS: Detection rates for the recognition of vessels, exudates, and haemorrhages were 91.7%, 93.1%, and 73.8% respectively. When compared with the results of the ophthalmologist, the network achieved a sensitivity of 88.4% and a specificity of 83.5% for the detection of diabetic retinopathy. CONCLUSIONS: Detection of vessels, exudates, and haemorrhages was possible, with success rates dependent upon preprocessing and the number of images used in training. When compared with the ophthalmologist, the network achieved good accuracy for the detection of diabetic retinopathy. The system could be used as an aid to the screening of diabetic patients for retinopathy.

Diabetic Retinopathy↗
PubMed1996

Objective detection of hemifield and quadrantic field defects by visual evoked cortical potentials.

AIMS/BACKGROUND: An objective method for detecting hemifield and quadrantic visual field defects has been developed using steady state visual evoked cortical potentials (VECPs), an adaptive noise canceller (ANC), and Hotelling's t2 statistic. The purpose of this study was to determine the sensitivity and specificity of the technique. METHODS: Nine subjects (mean age 44 years) were investigated with field loss due to a variety of causes including both anterior and posterior visual pathway lesions. Dynamic perimetry was performed by means of a Goldmann or Tübingen perimeter. VECP recordings were made from each visual field quadrant (23 degrees X 23 degrees) by means of a steady state reversing checkerboard (7.7 rev/s). The central 5 degrees of the visual field and the vertical and horizontal meridians were masked during these measurements. Recordings were made from three electrode sites, positioned over the visual cortex, relative to a mid frontal electrode. Each recording lasted 2 minutes, during which time fixation was monitored. The data from each recording were divided into 4 second segments, and the amplitude and phase of the VECP signal measured using the ANC. Hotelling's t2 statistic was applied to determine the probability of signal detection. Receiver operating characteristic curves were used to find the optimum signal detection threshold for identification of the visual field defects. RESULTS: The results of the study confirmed patterns of subjective visual field loss. The technique had a sensitivity and a specificity of 81% and 85%, respectively, for detecting 'non-seeing' areas in the inferior visual field, and 82% and 89%, respectively, for detecting 'non-seeing' areas in the superior visual field. CONCLUSION: These results demonstrate that the technique is of potential clinical value to ophthalmologists and neurologists when subjective perimetry is not possible.

Adolescent↗
PubMed1996

Functional imaging of the retina using the multifocal electroretinograph: a control study.

BACKGROUND: A new technique exists that enables functional mapping of the retina. A control population was examined to obtain normative values and to assess the reproducibility of this new test. METHODS: Twenty healthy volunteers were tested using a 61 hexagonal array stimulus with a 14 minute recording period. Median 5th and 95th percentiles were determined for implicit times and amplitude measures for the 61 test areas. Repeat measurements were performed on 10 individuals. Wilcoxon and Bland and Altman techniques were used to quantify reproducibility of the test. RESULTS: The implicit time of the wave-form components was not found to vary over the retina (peak or b-wave component, 35.52 (1.4) ms; trough or a-wave component, 17.76 (0.8) ms). Reproducibility was found to decrease with eccentricity (coefficient of repeatability 17.4% for the central area increasing to 30.3% for the peripheral ring). CONCLUSIONS: The findings suggest that reproducibility, although variable with eccentricity, is comparable with conventional electrophysiology. These limits of variation were used to assign confidence intervals to individual retinal areas and will be used (future work) in the examination of diseased states.

Adolescent↗
PubMed1995

Crossed polarising filters to measure relative afferent pupillary defects: reproducibility, correlation with neutral density filters and use in central retinal vein occlusion.

Measurement of a relative afferent pupillary defect (RAPD) can be carried out by attenuation of light received by the normal eye during the swinging flashlight test. Such measurements may be useful in the management of central retinal vein occlusion (CRVO). In this study a method employing cross polarised filters (CPFs) was tested for reproducibility. In addition the pattern of attenuation of light was compared with that by neutral density filters (NDFs). Finally, the method was used to investigate 74 patients with CRVO. The method was reproducible (8.7% variation) and showed exponential attenuation of light (in contrast to linear attenuation by the NDFs). In unilateral CRVO a sensitivity of 71% and specificity of 69% for the risk of iris neovascularisation was determined by the presence of RAPD requiring 20 degrees of rotation of the CPFs. It is concluded that CPFs provide a useful alternative to NDFs for the measurement of RAPD and have some advantages. They can be employed in the clinical management of patients with CRVO.

Adult↗
PubMed1994

A personal computer-based visual evoked potential stimulus and recording system.

A system for recording electroretinograms and visual evoked cortical potentials has been constructed with the use of a personal computer and a digital signal processing card. The system is based on widely available commercial hardware. It has been designed to be capable of performing routine visual electrophysiology as well as allowing the development of novel visual stimuli and signal detection techniques. The system enables both transient and steady-state stimulation rates. Pattern stimuli can be presented in pattern-reversal, pattern-onset, pattern-offset or motion-onset modes. In addition to conventional signal averaging, the digital signal processing card can also provide on-line Fourier analysis and is facilitating the development of adaptive filtering techniques for the detection of steady-state visual evoked cortical potentials. This versatile system is in regular clinical use for the measurement of electroretinograms and visual evoked cortical potentials.

Electrophysiology↗
PubMed1994

Visual field interpretation with a personal computer based neural network.

The Computer Assisted Touch Screen (CATS) and Computer Assisted Moving Eye Campimeter (CAMEC) are personal computer (PC)-based video-campimeters which employ multiple and single static stimuli on a cathode ray tube respectively. Clinical studies show that CATS and CAMEC provide comparable results to more expensive conventional visual field test devices. A neural network has been designed to classify visual field data from PC-based video-campimeters to facilitate diagnostic interpretation of visual field test results by non-experts. A three-layer back propagation network was designed, with 110 units in the input layer (each unit corresponding to a test point on the visual field test grid), a hidden layer of 40 processing units, and an output layer of 27 units (each one corresponding to a particular type of visual field pattern). The network was trained by a training set of 540 simulated visual field test result patterns, including normal, glaucomatous and neuro-ophthalmic defects, for up to 20,000 cycles. The classification accuracy of the network was initially measured with a previously unseen test set of 135 simulated fields and further tested with a genuine test result set of 100 neurological and 200 glaucomatous fields. A classification accuracy of 91-97% with simulated field results and 65-100% with genuine field results were achieved. This suggests that neural networks incorporated into PC-based video-campimeters may enable correct interpretation of results in non-specialist clinics or in the community.

Diagnosis, Computer-Assisted↗
PubMed1994

Argon laser photocoagulation of fluorescein stained retina--an unrecognised hazard?

Sodium fluorescein staining of the retina following fluorescein angiography may affect the absorption characteristics of argon ion laser photocoagulation. This hypothesis was investigated by performing laser photocoagulation on control and fluorescein stained porcine retinas. The resultant damage was viewed by scanning electron microscopy. In both specimens, argon irradiation produced damage to the pigment epithelium and overlying photoreceptor layer. The control sample showed a deep cylindrical burn, indicative of internal heating, in both retina and choroid. The fluorescein stained sample showed damage consistent with thermal interaction from the surface downwards leaving the choroid relatively spared. This preliminary study demonstrates that fluorescein staining of the retina changes the absorption site of argon laser light and this subject clearly merits further investigation.

Animals↗
PubMed1994

MR-guided biopsy of suspect breast lesions with a simple stereotaxic add-on-device for surface coils.

A guiding attachment is described that transforms a conventional magnetic resonance (MR) imaging surface coil into a stereotaxic biopsy unit. Eight patients, aged 38-66 years (mean, 54 years), with suspect breast lesions detected exclusively at contrast material-enhanced MR imaging underwent MR-guided needle biopsy with this unit. Diagnostic material was successfully aspirated in all patients (four carcinomas, three fibroadenomas, and one intraductal hyperplasia), and the diagnosis was subsequently confirmed at surgical biopsy. This technique promises to increase the diagnostic specificity for lesions seen solely at MR imaging.

Adult↗
PubMed1994

MR arthrography of the shoulder with gadopentetate dimeglumine: influence of concentration, iodinated contrast material, and time on signal intensity.

OBJECTIVE: MR arthrography of the shoulder with gadopentetate dimeglumine has been proved to be valuable in the diagnosis of injuries of the rotator cuff and glenoid labrum. To date, no standard protocol for the concentration of gadopentetate dimeglumine and the volume of iodinated contrast material used for intraarticular injection exists. This study compared the intraarticular signal intensities achieved with three different MR arthrography protocols with respect to the volume of iodinated contrast material, the concentration of gadopentetate dimeglumine, and the interval between injection of contrast material and the MR study. SUBJECTS AND METHODS: MR arthrography was performed with three different protocols in 38 patients (26 men, 12 women). Patients examined with protocol 1 received an intraarticular injection of 5 ml of iotrolan and 5 ml of a 5 mmol/l solution of gadopentetate dimeglumine, resulting in a gadopentetate dimeglumine concentration of 2.5 mmol/l. Patients in protocol 2 received only 0.5 ml of iotrolan plus 12 ml of a 10 mmol/l solution of gadopentetate dimeglumine, leading to a 10 mmol/l concentration. The interval between injection and MR imaging for patients in protocols 1 and 2 was 30-45 min. Patients in protocol 3 received an intraarticular injection of 10 ml iotrolan and 1 ml of a 500 mmol/l solution of gadopentetate dimeglumine, resulting in an intraarticular concentration of gadopentetate dimeglumine of 45 mmol/l. MR examinations were performed between 20 and 360 min after administration of contrast material. Patients in protocol 3 had additional conventional and CT arthrography within 30 min after injection. The contrast-to-noise ratio of the intraarticular signal intensity was calculated for all protocols. RESULTS: The contrast-to-noise ratio (mean +/- SD) was 22.7 +/- 7.4 for the 2.5 mmol/l solution (protocol 1), 47.5 +/- 11.9 for the 10 mmol/l solution (protocol 2), and 9.9 +/- 3.1 for the 45 mmol/l solution (protocol 3) within 1 hr after injection. For protocol 3, an increase in contrast-to-noise ratio was observed after 90-180 min (53.5 +/- 12.7), followed by a decrease in contrast-to-noise ratio after 180 min (17.1 +/- 8.2). The image quality of conventional, CT, and MR arthrography (90-180 min after injection) was good in all cases of protocol 3. CONCLUSION: For MR arthrography performed within 1 hr after injection, protocol 2 is sufficient. The optimal time frame for protocol 3 is between 1.5 and 3 hr after joint puncture. Protocol 3 allows the prior performance of conventional and CT arthrography. Therefore, the addition of 1 ml of a 500 mmol/l solution of gadopentetate dimeglumine to 10 ml of iodinated contrast material is advisable if a subsequent MR study is anticipated.

Adult↗
PubMed1994

Dissection of the thoracic aorta: pre- and postoperative findings on turbo-FLASH MR images obtained in the plane of the aortic arch.

This pictorial essay illustrates the pre- and postoperative findings seen in patients with aortic dissections on contrast-enhanced turbo-fast low-angle shot (FLASH) MR images obtained in the plane of the aortic arch. Contrast-enhanced images provide morphologic and functional information not normally available with conventional spin-echo (SE) MR imaging or dynamic CT. Preoperative examination of the acute dissection is often troubled by cardiovascular insufficiency and motion artifacts. Therefore most of our patients were examined postoperatively. The main reason for postsurgical imaging is the evaluation of the flow in the different lumina and the detection of complications (i.e., aneurysms or progress of dissection).

Aortic Dissection↗
PubMed1992

Steady-state visual evoked cortical potentials from stimulation of visual field quadrants. Optimizing pattern variables for the size of the field to be investigated.

The effects of check size and stimulus size were investigated to optimize the steady-state visual evoked cortical potentials from pattern-reversal stimulation of the visual field quadrants. Check sizes of 15', 30', 60', 90', 120' and 180' were investigated at a pattern reversal rate of 11.6 per second for field sizes varying from 2 degrees x 2 degrees to 24 degrees x 24 degrees. The visual evoked cortical potentials were recorded from mid occipital, right occipital and left occipital positions. In the inferonasal quadrant, the largest amplitudes were obtained with 30' and 60' check sizes; however, for these check sizes, the visual evoked cortical potential yielded limited additional information for field sizes greater than 4 degrees x 4 degrees and 6 degrees x 6 degrees, respectively. When a field size of 12 degrees x 12 degrees was investigated, a 90' check size was optimal. The results indicated that, with the above recording positions and check sizes of 15' to 120', there is an optimal number of pattern elements, 40 to 100, for stimulation of the inferonasal quadrant. This should be taken into account when a check size is selected to investigate a field quadrant of a particular size. Digital signal processing techniques were applied to analyze the visual evoked cortical potential, and the system shows promise for objective examination of the visual field.

Adult↗
PubMed1992

Visual evoked cortical potentials from transient dark and bright stimuli. Selective 'on' and 'off-pathway' testing?

The superior hemifields of five normal left eyes were stimulated by novel equal and opposite contrast pattern onset stimuli which were generated on a cathode ray tube. Patterns consisted of 144 discs, each subtending 60 min arc at the viewing distance of 40 cm and were separated by a distance equal to their diameter. Equal and opposite light changes were created by presenting the disc patterns with different luminance values on a uniform constant background (20 cd/m2). Transient visual evoked cortical potentials to the appearance and disappearance of the patterns were recorded separately and analysed. Significant amplitude differences between the responses to bright and dark stimuli were observed with light increment responses being 36-53% larger than the light decrement responses for pattern on-set and 54-80% larger for pattern off-set respectively. This finding is attributed to the difference in the input to the ON and OFF Parallel Pathways which are known to carry light increment and decrement information respectively, as well as differences in the metabolic and discharge rates of these pathways.

Adult↗