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Belfast, United Kingdom

Carson K.J.,Regional Medical Physics Service | Hanna G.G.,Cancer Center | Hounsell A.R.,Cancer Center
Nowotwory | Year: 2011

There is considerable interest in using 18F-Fluorodeoxyglucose (FDG) positron emission tomography (PET) images for radiotherapy treatment planning (RTP) purposes, and in particular for defining target volumes. This is a rapidly evolving subject and this review describes the background to this application of PET imaging and discusses the issues involved. Source

McEwan C.,University of Ulster | Nesbitt H.,University of Ulster | Nicholas D.,University of Ulster | Kavanagh O.N.,University of Ulster | And 5 more authors.
Bioorganic and Medicinal Chemistry | Year: 2016

Sonodynamic therapy (SDT) involves the activation of a non-toxic sensitiser drug using low-intensity ultrasound to produce cytotoxic reactive oxygen species (ROS). Given the low tissue attenuation of ultrasound, SDT provides a significant benefit over the more established photodynamic therapy (PDT) as it enables activation of sensitisers at a greater depth within human tissue. In this manuscript, we compare the efficacy of aminolevulinic acid (ALA) mediated PDT and SDT in a squamous cell carcinoma (A431) cell line as well as the ability of these treatments to reduce the size of A431 ectopic tumours in mice. Similarly, the relative cytotoxic ability of Rose Bengal mediated PDT and SDT was investigated in a B16-melanoma cell line and also in a B16 ectopic tumour model. The results reveal no statistically significant difference in efficacy between ALA mediated PDT or SDT in the non-melanoma model while Rose Bengal mediated SDT was significantly more efficacious than PDT in the melanoma model. This difference in efficacy was, at least in part, attributed to the dark pigmentation of the melanoma cells that effectively filtered the excitation light preventing it from activating the sensitiser while the use of ultrasound circumvented this problem. These results suggest SDT may provide a better outcome than PDT when treating highly pigmented cancerous skin lesions. © 2016 Published by Elsevier Ltd. Source

McFadden S.L.,University of Ulster | Hughes C.M.,University of Ulster | Mooney R.B.,Regional Medical Physics Service | Winder R.J.,University of Ulster
Journal of Radiological Protection | Year: 2013

The purpose of this work is to investigate removal of the anti-scatter grid and alteration of the frame rate in paediatric interventional cardiology (IC) and assess the impact on radiation dose and image quality. Phantom based experimental studies were performed in a dedicated cardiac catheterisation suite to investigate variations in radiation dose and image quality, with various changes in imaging parameters. Phantom based experimental studies employing these variations in technique identified that radiation dose reductions of 28%-49% can be made to the patient with minimal loss of image quality in smaller sized patients. At present, there is no standard technique for carrying out paediatric IC in the UK or Ireland, resulting in the potential for a wide variation in radiation dose. Dose reductions to patients can be achieved with slight alterations to the imaging equipment with minimal compromise to the image quality. These simple modifications can be easily implemented in clinical practice in IC centres. © 2013 IOP Publishing Ltd. Source

Lockhart C.J.,Queens University of Belfast | McCann A.J.,Regional Medical Physics Service | Pinnock R.A.,Regional Medical Physics Service | Hamilton P.K.,Queens University of Belfast | And 2 more authors.
American Journal of Physiology - Heart and Circulatory Physiology | Year: 2014

Structural and functional changes in the microcirculation in type 1 diabetes mellitus predict future end-organ damage and macrovascular events. We explored the utility of novel signal processing techniques to detect and track changes in ocular hemodynamics in patients with this disease. Twenty-four patients with uncomplicated type 1 diabetes mellitus and eighteen age- and sex-matched control subjects were studied. Doppler ultrasound was used to interrogate the carotid and ophthalmic arteries, and digital photography was used to image the retinal vasculature. Frequency analysis algorithms were applied to quantify velocity waveform structure and retinal photographic data at baseline and after inhalation of 100% O2. Frequency data were compared between groups. No significant differences were found in the resistive index between groups at baseline or after inhaled O2. Frequency analysis of Doppler flow velocity waveforms identified significant differences in bands 3–7 between patients and control subjects in data captured from the ophthalmic artery (P < 0.01 for each band). In response to inhaled O2, changes in frequency band amplitudes were significantly greater in control subjects compared with patients (P < 0.05). Only control subjects demonstrated a positive correlation (R = 0.61) between changes in retinal vessel diameter and frequency band amplitudes derived from ophthalmic artery waveform data. The use of multimodal signal processing techniques applied to Doppler flow velocity waveforms and retinal photographic data identified preclinical changes in the ocular microcirculation in patients with uncomplicated diabetes mellitus. An impaired autoregulatory response of the retinal microvasculature may contribute to the future development of retinopathy in such patients. © 2014 the American Physiological Society. Source

Irvine D.,Regional Medical Physics Service | McJury M.,Regional Medical Physics Service
Journal of Radiotherapy in Practice | Year: 2010

Background and purpose: Following a recent major upgrade in cone-beam computed tomography (CBCT) software and functionality, we have reassessed aspects of our Varian Acuity simulator performance for use in treatment planning. The feasibility of using CBCT for treatment planning has been assessed and here we report specifically on Hounsfield number (HN) accuracy and related dose errors, and digitally reconstructed radiograph (DRR) image quality. Methods: Using a Catphan® 600 CT phantom, HN accuracy and uniformity were investigated for a range of CBCT imaging modes. This included the variation in HNs with scan length and phantom position. Results were compared with those acquired from conventional CT. Treatment plans for three sites were generated using the Rando phantom, and results from CBCT-based data were compared to that from CT-based data using a gamma analysis. Image quality of DRRs based on CBCT data were compared with those from CT data both quantitatively, by calculating the modulation transfer function (MTF) and qualitatively, by counting the number of line pairs visible on a phantom. Results and conclusions: Catphan data showed that for certain cases, the HN calibration of the Acuity CBCT was out of tolerance and could lead to errors in dose calculation of >2%. HNs were only acceptable for scan lengths >10 cm. In multi-scan mode, geometric shifts and differences in HNs were seen on CT slices on either side of the interface between the two acquisitions. However, comparisons between treatment plans calculated using CBCT data and conventional CT data from Rando phantoms showed that head, pelvis and thorax plans were acceptable. CBCT DRR image quality compared favourably with a conventional CT scanner in some respects; however, image uniformity and low contrast resolution were poorer due to the cupping artefact obtained with CBCT scans. Copyright © Cambridge University Press 2010. Source

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