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Yip M.,University of Surrey | Zanca F.,University Hospitals Gasthuisberg | MacKenzie A.,National Coordinating Center for the Physics of Mammography | Workman A.,Northern Ireland Regional Medical Physics Agency | And 5 more authors.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

The purpose of this study is to evaluate the effect of simulated dose reduction using CDMAM and mastectomy images acquired on two digital mammography systems. High dose images have been artificially degraded to reduced dose levels by systematically adding filtered noise. Automated scoring has been carried out on the degraded CDMAM images and on experimental CDMAM images, taken at the same corresponding reduced doses. Contrast-detail curves were derived for both, at all doses, and compared. Relative difference in the contrast-detail curves was approximately 5% overall for all four doses. For the mastectomy images noise power spectra were obtained and the ratio of experimental to synthetic low dose NPS profiles averaged for all doses at 1.04. The largest differences in the NPS profiles were found at the high spatial frequencies, corresponding with the differences in the small discs in the contrast-detail curves. © 2010 Springer-Verlag. Source


Mackenzie A.,National Coordinating Center for the Physics of Mammography | Workman A.,Northern Ireland Regional Medical Physics Agency | Dance D.R.,National Coordinating Center for the Physics of Mammography | Dance D.R.,University of Surrey | And 4 more authors.
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2010

Comparing the clinical performance of digital mammography technologies is challenging. The aim of this work is to develop and test a methodology for adjusting mammographic images taken on a given imaging system to simulate their appearance as if taken on a different system. Such methodology would be very useful for a wide range of system performance and design studies using both phantom and clinical images. The process involves changing the image blurring in accordance with the measured modulation transfer functions and adding noise (electronic, quantum and structure). The method has been tested by adapting flat field images acquired using an amorphous selenium detector and a computed radiography (CR) detector to different dose levels and comparing the resultant simulated NPSs with directly measured NPSs. For the detectors used in this work the NPSs at different dose levels are well predicted. This could be a powerful tool for studies of clinical image quality. © 2010 Springer-Verlag. Source


Donaghy C.,Royal Victoria Hospital | Pinnock R.,Northern Ireland Regional Medical Physics Agency | Abrahams S.,University of Edinburgh | Cardwell C.,Queens University of Belfast | And 4 more authors.
Journal of Neurology | Year: 2010

Historical studies of eye movements in motor neurone disease (MND) have been conflicting although current findings suggest that eye movement abnormalities relate to frontal lobe impairment. Numerous case reports, however, describe slow saccades and supranuclear gaze palsies in patients with MND often associated with bulbar-onset disease. We performed a study of saccades and smooth pursuit in a large group of patients with MND to examine for any differences between bulbar-onset and spinal-onset patients. Forty-four patients (14 bulbar-onset and 30 spinal-onset patients) and 45 controls were recruited. Reflexive saccades, antisaccades and smooth pursuit were examined using infra-red oculography and all subjects then underwent neuropsychological evaluation. Reflexive saccades were found to be slower in bulbar-onset compared to spinal-onset patients and controls (p = 0.03, p = 0.05). Antisaccade latency (p = 0.01) and antisaccade type 1 errors (p = 0.03, p = 0.04) were increased in patients compared to controls. 'Proportion of time spent in smooth pursuit' and smooth pursuit 'velocity gain' were reduced in patients compared to controls (p = 0.000, p = 0.001). Antisaccade errors and velocity gain correlated with neuropsychological measures sensitive to lesions of the frontal lobes. This is the first study to highlight the presence of slow saccades in bulbar-onset MND. These findings suggest that slow saccades may be due to increased brainstem pathology in bulbar-onset disease that involves burst cell neurons. Furthermore these observations highlight the potential for overlap between bulbar-onset MND and progressive supranuclear palsy (PSP) as both can have a bulbar palsy and slowed saccades. © 2010 Springer-Verlag. Source


Quinn C.E.,Queens University of Belfast | Hamilton P.K.,Queens University of Belfast | Mccann A.J.,Northern Ireland Regional Medical Physics Agency | Agnew C.E.,Northern Ireland Regional Medical Physics Agency | And 4 more authors.
Microcirculation | Year: 2011

Waveform analysis has been used to assess vascular resistance and predict cardiovascular events. We aimed to identify microvascular abnormalities in patients with IGT using ocular waveform analysis. The effects of pioglitazone were also assessed. Methods: Forty patients with IGT and 24 controls were studied. Doppler velocity recordings were obtained from the central retinal, ophthalmic, and common carotid arteries, and sampled at 200Hz. A discrete wavelet-based analysis method was employed to quantify waveforms. The RI was also determined. Patients with IGT were randomized to pioglitazone or placebo, and measurements were repeated after 12-week treatment. Results: In the ocular waveforms, significant differences in power spectra were observed in frequency band 4 (corresponding to frequencies between 6.25 and 12.50Hz) between groups (p<0.05). No differences in RI occurred. No association was observed between waveform parameters and fasting glucose or insulin resistance. Pioglitazone had no effect on waveform structure, despite significantly reducing insulin resistance, fasting glucose, and triglycerides (p<0.05). Conclusions: Analysis of ocular Doppler flow waveforms using the discrete wavelet transform identified microvascular abnormalities that were not apparent using RI. Pioglitazone improved glucose, insulin sensitivity, and triglycerides without influencing the contour of the waveforms. © 2011 John Wiley & Sons Ltd. Source


Pinnock R.A.,Northern Ireland Regional Medical Physics Agency | McGivern R.C.,Northern Ireland Regional Medical Physics Agency | Forbes R.,Craigavon Area Hospital | Gibson J.M.,Royal Victoria Hospital
Journal of Neurology | Year: 2010

Since the basal ganglia are thought to have a role in controlling ocular fixation it is expected that patients with parkinsonian conditions would show impaired performance in fixation tasks. Our study examines ocular fixation in patients with a range of parkinsonian conditions (Idiopathic Parkinson's Disease, Multiple System Atrophy and Progressive Supranuclear Palsy). Eye movements were recorded from 44 patients and 50 age matched control subjects during ocular fixation both with and without a visible target. The data for each patient were then characterised in terms of fixation periods and saccadic intrusions (SI). Patient groups exhibited larger and more frequent SI as well as greater displacement from the fixation target. Patients with Progressive Supranuclear Palsy exhibit larger SI than control subjects when fixation targets are visible, this difference is reversed in the absence of a fixation target. Patients with Multiple System Atrophy show increased frequency of SI both with and without a visible target. Our findings show that ocular fixation is impaired in patients with parkinsonian conditions and may prove useful as part of an oculomotor profile to aid with the differentiation of parkinsonian conditions. © 2009 Springer-Verlag. Source

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