Biomedical subjects

N O'Hare

Publications and source records attributed to N O'Hare.

13 recordsLinked to original sources

PubMed2003

Development and application of a quality control procedure for short-wave diathermy units.

Short-wave diathermy (SWD) is a form of radiofrequency (RF) radiation, operating at 27.12 MHz, that is used therapeutically by physiotherapists. Although this form of therapy is widely available, the management of the equipment is not often addressed by either physiotherapists or by medical physics/clinical engineering. A quality control protocol for SWD units, examining power output and electrical and mechanical condition, was developed and applied to 20 units used in clinical practice. In addition, an environmental assessment of where the units were used was also included. Results showed that the power output was generally stable (coefficient of variation range 0-8.8%) and reproducible (coefficient of variation range 0-6.8%). When the outputs from 12 similar units were compared, it was found that the relationship between the units' intensity settings and power output measurements was non-linear. Two units with mechanical timers were found to have inaccuracies that could contribute, under a 'worst-case' scenario, to a dosage error of up to 45%. Environmental analysis found that all treatment plinths in use contained metal parts, which could constitute a fire hazard, and no department examined was equipped with an RF screened room, a facility that would ensure that other persons in the vicinity were not exposed to excessive stray radiation.

Equipment Safety↗

PubMed2002

Development of a quality assurance protocol for peripheral subtraction imaging applications.

Peripheral subtraction scanning is used to trace the blood vessels of upper and lower extremities. In some modern C-arm fluoroscopy systems this function is performed automatically. In this mode the system is programmed to advance and stop in a series of steps taking a mask image at each point. The system then repeats each step after the contrast agent has been injected, and produces a DSA image at each point. Current radiographic quality assurance protocols do not address this feature. This note reviews methods of measuring system vibration while images are being acquired in automated peripheral stepping. The effect on image quality pre- and post-image processing is assessed. Results show that peripheral stepping DSA does not provide the same degree of image quality as static DSA. In examining static test objects, the major cause of the reduction in image quality is misregistration due to vibration of the image intensifier during imaging.

Contrast Media↗

PubMed2002

Evaluation of renal function following treatment with 5-aminosalicylic acid derivatives in patients with ulcerative colitis.

BACKGROUND: A number of cases of nephrotoxicity have been reported in patients with inflammatory bowel disease taking oral 5-aminosalicylic acid (5-ASA). AIM: To evaluate the effects of 9 months of therapy with mesalazine or olsalazine on renal function in patients with ulcerative colitis in remission. METHODS: Forty patients with ulcerative colitis in complete remission for 6 months were randomized to either olsalazine (n=20) or mesalazine (n=20 for nine months). Thirty-six of the 40 patients were on prior salicylate therapy. Disease activity was the measure ofclinical efficacy and was assessed by the Harvey-Bradshaw Index (HBI). Laboratory efficacy measurements included glomerular filtration rate (GFR), microalbuminuria, urinary gluthathione S-transferase (GST) and serum C-reactive protein (CRP). Safety analysis consisted of documentation of adverse events and laboratory values. RESULTS: There was no significant reduction in the GFR overall on therapy. The levels of GFR adjusted for baseline were similar in the two treatment groups after 3, 6 and 9 months. A significantly higher percentage of mesalazine-treated patients experienced drug related adverse events, all of a minor nature. The incidence of adverse events causing early withdrawal was similar in the two treatment groups. CONCLUSION: Treatment with mesalazine or olsalazine for 9 months had no significant impact on GFR.

Adult↗

PubMed2001

Superior epithelial arcuate lesions with soft contact lens wear.

BACKGROUND: Superior epithelial arcuate lesions (SEALs) are an infrequent and often asymptomatic complication of conventional soft contact lens wear. The characteristic arcuate pattern of the full-thickness corneal epithelial lesion usually occurs in the area covered by the upper eyelid, within 2 to 3 mm of the superior limbus in the 10- and 2-o'clock region. METHODS: Literature on SEALs and recent clinical records from clinical trials using two types of prototype high Dk soft contact lenses were reviewed to gain greater insights into the etiology of SEALs. RESULTS AND CONCLUSIONS: The reported low incidence of SEALs is partly because SEALs are not usually symptomatic. The etiology of SEALs is multifactorial. Our current hypothesis is that SEALs are produced by mechanical chaffing at the peripheral cornea. This chaffing occurs as a result of inward pressure of the upper lid, in an area where the peripheral corneal topography and lens design, rigidity, and surface characteristics combine to create excessive "frictional" pressure and abrasive shear force on the epithelial surface. Patient characteristics such as gender, age, and specific corneal and lid topographies also appear to influence the occurrence of SEALs. Prototype silicone hydrogel lenses are made from higher modulus materials with surfaces that seem to differ subtly in wettability in some patients. The prevalence of SEALs may well increase with the first generations of these lenses.

Clinical Trials as Topic↗

PubMed2000

The development of a phantom to determine foetal organ doses from 131I in the foetal thyroid.

Iodine can accumulate in the foetal thyroid from the twelfth week of gestation onwards. If the iodine taken up by the foetal thyroid is in the form of 131I then the thyroid and its proximal tissues and organs will be irradiated. Several mathematical models exist in the literature on foetal/maternal iodine kinetics. However, very few studies have been performed where the foetal thyroid had been physically modelled thus allowing the determination of foetal organ dosimetry from 131I in the foetal thyroid. Here, the development of such a physical model or phantom is described and dosimetry results obtained from the phantom are discussed. The phantom is of Perspex construction, the dimensions of which are sufficient to incorporate models of the foetus at 16, 24 and 36 weeks' gestational age. The dosimetry of two organs is presented, that of the brain and the thymus. The results show that the measured absorbed dose is comparable with that calculated using modified MIRD dosimetry and traditional methods. The results also show that the dose to the thymus is greater than that of the brain by a factor of almost 30 for 16 weeks' gestational age.

Brain↗

PubMed2000

A quality control procedure for force platforms.

A force platform is a technical method of quantitatively assessing balance indirectly. The use of force platforms in physiotherapy departments has become more prominent over the last few years. However, the main drawback in the use of force platforms is the lack of comprehensive calibration procedures, which casts doubt on the results obtained with these systems. Existing calibration tests are limited to testing the spatial accuracy of the force platform. This paper describes a comprehensive quality control test procedure which was developed. It is proposed that the developed quality control test procedure could be used to test all types of force platform and it includes a description of how the tests should be carried out, the frequency with which they should be carried out and the expected performance for each of the tests as recommended for the most part by the Association Francaise de Posturologie.

Biomechanical Phenomena↗

PubMed2000

Development of a novel method for assessing balance: the quantitative posturography system.

Balance is the ability to maintain equilibrium while sitting or standing. There are a number of different methods which are used to assess balance: technical methods such as sway magnetometry, ataxia meter and force platforms, and clinical methods such as the functional reach test, Berg balance test and fall risk index. The most frequently used technical method is the force platform. There are two types of force platform, a static and a dynamic force platform, of which the dynamic force platform has been found to be more sensitive to detect impaired balance. The quantitative posturography system (QPS) described in this paper is a type of dynamic force platform; however, it has a simpler design than the currently available dynamic force platforms and can match the subject's sway exactly for tilting in the anterio-posterior and medio-lateral directions with its novel design. This paper describes the novel design of the QPS and its calibration.

Biomechanical Phenomena↗

PubMed1997

Classification of mild Alzheimer's disease by artificial neural network analysis of SPET data.

An evaluation of the performance of artificial neural networks (ANNs) for the classification of probable Alzheimer's disease (pAD) patients was undertaken using data extracted from four regions of interest constructed on single photon emission tomographic (SPET) cerebral perfusion images. Two studies using feed-forward neural networks (FFNNs) were undertaken. The first was to determine if it would be possible to classify pAD patients and normal subjects in a mixed group, comprising 29 patients diagnosed as having pAD varying in severity from mild, established dementia to moderate dementia and 10 healthy control subjects. The second was to determine if the networks generated in the first study could prospectively classify 15 additional patients with very mild or mild cognitive impairment. The results were compared to those obtained using the same data and discriminant analysis. The relative performances of the two analysis techniques were assessed on the basis of the area under receiver operating characteristics (ROC) curves. The FFNN successfully classified all datasets in the first study, achieving an area under the ROC curve of 1.00, whereas discriminant analysis achieved 0.94. When tested on data from the second group, the areas under the ROC curves varied between 0.86 and 1.00 for the FFNN, whereas that for discriminant analysis was 0.99. We conclude that FFNNs can accurately classify pAD patients with mild to moderate dementia using data obtained from SPET cerebral perfusion images.

Aged↗

PubMed1996

Event-related potential prolongation in Alzheimer's disease signifies frontal lobe impairment: evidence from SPECT imaging.

BACKGROUND: The N2 and P3 components of auditory event-related potentials (ERPs) and single-photon emission computed tomographic (SPECT) images are separate independent biological markers of cerebral function and are abnormal in Alzheimer's disease (AD). The relationship between ERP N2 and P3 latencies and regional cerebral perfusion abnormalities in AD is unknown. METHODS: ERP and SPECT data were obtained one week apart in 18 patients with "probable" AD of mild or moderate severity, and 12 healthy age-matched elderly controls. Average premotor frontal, anterior temporal, inferior parietal, and occipital cortical/cerebellar perfusion ratios were calculated from the SPECT data and correlations with ERP N2 and P3 latencies derived for AD and control groups separately. RESULTS: ERP N2 latency was correlated significantly with the average frontal perfusion ratio (r = -.59; p < .009), but correlations with average temporal, parietal, and occipital ratios were nonsignificant in the AD group. Similarly, ERP P3 latency was correlated significantly with the average frontal perfusion ratio (r = -.65; p < .004), but not with the other perfusion ratios in the AD group. In the control group, a partial correlation between the average frontal perfusion ratio and the ERP N2 latency was noted (r = -.52; p < .09), but no other ERP/SPECT correlations approached statistical significance. CONCLUSION: ERP N2 and P3 latency delay in AD is a function of differential frontal lobe hypoperfusion.

Aged↗

PubMed1996

Somatostatin and somatostatin analogues in medullary thyroid carcinoma.

Medullary thyroid carcinoma (MTC) is a neuroendocrine tumour characterized by the production and secretion of calcitonin. MTC tumours may express functional somatostatin receptors (hSSTR). A significant proportion of hSSTR receptor-positive MTC tumours, including metastatic disease, may be visualized in vivo through 111In-pentetreotide scintigraphy. Four patients with recurrent/metastatic disease, who had previously been assessed with 111In-anti-CEA monoclonal antibody fragment [F(ab')2] imaging, were evaluated. 111In-pentetreotide scintigraphy localized all known disease sites. Furthermore, mediastinal disease was detected in one patient with negative conventional, and 111In-anti-CEA F(ab')2 imaging studies. The detection of somatostatin within the tumour (2 patients), or negative octreotide challenges (2 patients), did not affect the outcome of 111In-pentetreotide scintigraphy. In conclusion, 111In-pentetreotide scintigraphy appears at least as effective as 111In-anti-CEA F(ab')2 imaging and should be considered in the diagnostic evaluation of MTC, particularly in the setting of recurrent/metastatic disease not detected by conventional means.

Adult↗

PubMed1994

The discriminant value of semiquantitative SPECT data in mild Alzheimer's disease.

UNLABELLED: In most semiquantitative SPECT studies, overlap between groups of patients with Alzheimer's disease (AD) and age-matched elderly controls is such that single posterior cortical perfusion measurements lack sensitivity. In the present study, the value of a combination of semiquantitative temporoparietal SPECT parameters was examined. METHODS: Supratentorial transaxial perfusion measurements were obtained in frontal, anterior temporal, posterior temporoparietal and occipital cortical areas in both hemispheres, in a baseline population of 10 healthy elderly controls and 30 mild to moderately impaired AD patients, as well as in a prospective group of 15 patients with mild cognitive impairment, 12 patients with a diagnosis of probable AD and individual cases of multi-infarct dementia, dementia-frontal type and paranoid psychosis. A linear discriminant function (LDF) was calculated from the baseline subjects' data to classify control and AD subjects individually. RESULTS: Highly significant hypoperfusion was noted in both the anterior temporal and posterior temporoparietal regions of interest in the AD group compared with controls, but with significant overlap. Using an LDF incorporating these perfusion measurements in both hemispheres, 10/10 (100%) controls and 26/30 (87%) AD baseline subjects were correctly classified. Using the baseline LDF in the prospective 15 mildly impaired cases, 11/12 new mild AD cases and none of the 3 non-AD cases were classified in the AD group. CONCLUSION: These results support the use of a combination of semiquantitative SPECT perfusion estimates from cortical areas with predictable pathological involvement in AD in a linear discriminant format in the clinical assessment of patients with suspected AD.

Aged↗

PubMed1993

Erythromycin improves emptying of the denervated stomach after oesophagectomy.

Oesophagectomy, necessitating vagotomy, is associated with delayed gastric emptying. Cisapride and erythromycin have prokinetic effects and improve emptying of the innervated stomach. Their effect on the denervated stomach following oesophagectomy is unknown. The effect of pyloroplasty, cisapride and erythromycin on the rate of gastric emptying after oesophagectomy was studied using a radiolabelled meal. Oesophagectomy was associated with a marked delay in gastric emptying (56 per cent of the test meal remaining after 4 h) compared with age- and sex-matched normal controls (16 per cent; P < 0.001). Erythromycin improved the rate of gastric emptying to preoperative control values (18 per cent). Cisapride had no significant effect on gastric emptying. After pyloroplasty, 32 per cent of the label remained at 4 h (P = 0.065). The mean(s.e.m.) half-emptying time in patients receiving erythromycin was 94(29) min, which was similar to control values, 55(3) min (P = 0.26). Erythromycin may have a role in the treatment of gastric stasis following oesophagectomy or truncal vagotomy.

Aged↗

PubMedDate not supplied

Analysis of ultraviolet phototherapy and photochemotherapy resources in Ireland.

BACKGROUND: Ultraviolet (UV) phototherapy is widely used and very successful in the treatment of skin conditions. As such a safe and efficient service is essential. At present, there are no standard Irish guidelines regarding the operation, calibration or inspection of UV equipment nor is there an Irish policy on staff/patient safety or training issues. AIM: To survey all known phototherapy centres in Ireland. METHODS: A postal questionnaire was sent to all known phototherapy centres in Ireland addressed to the consultant dermatologist or the physiotherapist-in-charge. It was divided into six sections: Instrumentation, Quality Assurance, UV meters, equipment maintenance, patient/staff safety and training. Comments on current practice were invited. Non-respondents were contacted by telephone, in some cases the survey was mailed a second time. RESULTS: This study demonstrated a substantial quantity of suboptimal equipment in use and a lack of consensus regarding quality assurance inspection and UV meter calibration frequency. CONCLUSIONS: Guidelines must be established for calibration of UV equipment and standardisation of phototherapy protocols in Ireland.

Calibration↗