29 research outputs found

    Reducing radiation dose for a linear slot scanning digital X-ray machine using a filtration technique

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    This study describes the development of a filtration technique applied to the Lodox Statscan linear slotscanning digital X-ray system to reduce radiation dose to paediatric patients whilst preserving diagnostic image quality. The Statscan is an FDA approved, commercially available digital X-ray system commonly used for trauma and emergency patients. The Statscan provides significantly lower radiation dose to patients than conventional Xray systems for comparable studies without loss of image quality. This is particularly beneficial in paediatric radiology, where the risks associated with ionizing radiation are much higher. A static dose prediction model for the Statscan which was previously developed at the University of Cape Town has been adapted to create a dynamic dose prediction model which allows the user to adjust the system scanning parameters. The model calculates the patient entrance dose from an energy spectrum generated using the input parameters. The effective dose for a paediatric sized patient is then calculated using a Monte Carlo simulation. The dynamic model allows for variation of the scan parameters and direct observation of the expected dose levels for specific examinations. Filtration is a well-known technique for reducing radiation dose, where a filter material is placed in the path of the X-ray beam to reduce patient exposure to radiation. The dynamic model was used to design a new filtration technique for the paediatric settings on the Statscan

    Reducing effective dose to a paediatric phantom by using different combinations of kVp, mAs and additional filtration whilst maintaining image quality

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    Purpose: To determine whether using different combinations of kVp and mAs with additional filtration can reduce the effective dose to a paediatric phantom whilst maintaining diagnostic image quality. Methods: 27 images of a paediatric AP pelvis phantom were acquired with different kVp, mAs and additional copper filtration. Images were displayed on quality controlled monitors with dimmed lighting. Ten diagnostic radiographers (5 students and 5 experienced radiographers) had eye tests to assess visual acuity before rating the images. Each image was rated for visual image quality against a reference image using 2 alternative forced choice software using a 5-point Likert scale. Physical measures (SNR and CNR) were also taken to assess image quality. Results: Of the 27 images rated, 13 of them were of acceptable image quality and had a dose lower than the image with standard acquisition parameters. Two were produced without filtration, 6 with 0.1mm and 5 with 0.2mm copper filtration. Statistical analysis found that the inter-rater and intra-rater reliability was high. Discussion: It is possible to obtain an image of acceptable image quality with a dose that is lower than published guidelines. There are some areas of the study that could be improved. These include using a wider range of kVp and mAs to give an exact set of parameters to use. Conclusion: Additional filtration has been identified as amajor tool for reducing effective dose whilst maintaining acceptable image quality in a 5 year old phantom

    Hand X-ray absorptiometry for measurement of bone mineral density on a slot-scanning X-ray imaging system

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    Includes bibliographical references.Bone mineral density (BMD) is an indicator of bone strength. While femoral and spinal BMDs are traditionally used in the management of osteoporosis, BMD at peripheral sites such as the hand has been shown to be useful in evaluating fracture risk for axial sites. These peripheral locations have been suggested as alternatives to the traditional sites for BMD measurement. Dual-energy X-ray absorptiometry (DXA) is the gold standard for measuring BMD due to low radiation dose, high accuracy and proven ability to evaluate fracture risk. Computed digital absorptiometry (CDA) has also been shown to be very effective at measuring the bone mass in hand bones using an aluminium step wedge as a calibration reference. In this project, the aim was to develop algorithm s for accurate measurement of BMD in hand bones on a slot - scanning digital radiography system. The project assess e d the feasibility of measuring bone mineral mass in hand bones using CDA on the current system. Images for CDA - based measurement were acquired using the default settings on the system for a medium sized patient. A method for automatic processing of the hand images to detect the aluminium step wedge, included in the scan for calibration, was developed and the calibration accuracy of the step wedge was evaluated. The CDA method was used for computation of bone mass with units of equivalent aluminium thickness (mmA1). The precision of the method was determined by taking three measurements in each of 1 6 volunteering subjects and computing the root - mean - square coefficient of variation (CV) of the measurements. The utility of the method was assessed by taking measurements of excised bones and assessing the correlation between the measured bone mass and ash weight obtained by incinerating the bones. The project also assessed the feasibility of implementing a DXA technique using two detectors in a slot-scanning digital radiography system to acquire dual-energy X-ray images for measuring areal and volumetric BMD of the middle phalanx of the middle finger. The dual-energy images were captured in two consecutive scans. The first scan captured the low- energy image using the detector in its normal set-up. The second scan captured the high- energy image with the detector modified to include an additional scintillator to simulate the presence of a second detector that would capture the low-energy image in a two-detector system. Scan parameters for acquisition of the dual-energy images were chosen to optimise spectral separation, entrance dose and image quality. Simulations were carried out to evaluate the spectral separation of the low- and high-energy spectra

    OPTIMAX 2014 - Radiation dose and image quality optimisation in medical imaging

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    Medical imaging is a powerful diagnostic tool. Consequently, the number of medical images taken has increased vastly over the past few decades. The most common medical imaging techniques use X-radiation as the primary investigative tool. The main limitation of using X-radiation is associated with the risk of developing cancers. Alongside this, technology has advanced and more centres now use CT scanners; these can incur significant radiation burdens compared with traditional X-ray imaging systems. The net effect is that the population radiation burden is rising steadily. Risk arising from X-radiation for diagnostic medical purposes needs minimising and one way to achieve this is through reducing radiation dose whilst optimising image quality. All ages are affected by risk from X-radiation however the increasing population age highlights the elderly as a new group that may require consideration. Of greatest concern are paediatric patients: firstly they are more sensitive to radiation; secondly their younger age means that the potential detriment to this group is greater. Containment of radiation exposure falls to a number of professionals within medical fields, from those who request imaging to those who produce the image. These staff are supported in their radiation protection role by engineers, physicists and technicians. It is important to realise that radiation protection is currently a major European focus of interest and minimum competence levels in radiation protection for radiographers have been defined through the integrated activities of the EU consortium called MEDRAPET. The outcomes of this project have been used by the European Federation of Radiographer Societies to describe the European Qualifications Framework levels for radiographers in radiation protection. Though variations exist between European countries radiographers and nuclear medicine technologists are normally the professional groups who are responsible for exposing screening populations and patients to X-radiation. As part of their training they learn fundamental principles of radiation protection and theoretical and practical approaches to dose minimisation. However dose minimisation is complex – it is not simply about reducing X-radiation without taking into account major contextual factors. These factors relate to the real world of clinical imaging and include the need to measure clinical image quality and lesion visibility when applying X-radiation dose reduction strategies. This requires the use of validated psychological and physics techniques to measure clinical image quality and lesion perceptibility

    Optimising image quality for medical imaging

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    OPTIMAX 2016 was held at the University of Salford in Greater Manchester. It is the fourth summer school of OPTIMAX with other renditions having been organized at the University of Salford (2013), ESTeSL, Lisbon (2014) and Hanze UAS, Groningen (2015). For OPTIMAX 2016, 72 people participated from eleven countries, comprising PhD, MSc and BSc students as well as tutors from the seven European partner universities. Professional mix was drawn from engineering, medical physics/ physics and radiography. OPTIMAX 2016 was partly funded by the partner universities and partly by the participants. Two students from South Africa and two from Brazil were invited by Hanze UAS (Groningen) and ESTeSL (Lisbon). One student from the United Kingdom was funded by the Nuffield Foundation. The summer school included lectures and group projects in which experimental research was conducted in five teams. Each team project focus varied and included: optimization of full spine curvature radiography in paediatrics; ultrasound assessment of muscle thickness and muscle cross-sectional area: a reliability study; the Influence of Source-to-Image Distance on Effective Dose and Image Quality for Mobile Chest X-rays; Impact of the anode heel effect on image quality and effective dose for AP Pelvis: A pilot study; and the impact of pitch values on Image Quality and radiation dose in an abdominal adult phantom using CT. OPTIMAX 2016 culminated in a poster session and a conference, in which the research teams presented their posters and oral presentations. This book comprises of two sections, the first four chapters concern generic background information which has value to summer school organization and also theory on which the research projects were built. The second section contains the research papers in written format. The research papers have been accepted for the ECR conference, Vienna, 2017 as either oral presentations or posters

    Optimax 2016 : peer observation of facilitation

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    In August 2016, a 3-week research Summer School was delivered at University of Salford. The Summer School, known as ‘OPTIMAX’ was in its fourth year of delivery. Previous iterations were held in the Netherlands (2015), Portugal (2014) and Salford (2013). The purpose of OPTIMAX is to facilitate collaborative international and interdisciplinary research between university academics and students. This offers an exceptional opportunity not only for students, but also for tutors who want to develop their facilitation skills. The project reported here used tutor observers (i.e. tutors who attend the summer school, in an observational capacity only, to develop their own skills as teachers) to observe, identify and reflect on a range of facilitation practices for managing the diverse OPTIMAX research groups. The project presents a description of the peer-observation method we used and highlights a number of findings related to facilitator strategies that appeared to influence group dynamics and learning. These observations are then used to make recommendations about how OPTIMAX tutors can be prepared for their facilitation experience

    Radiation dose and image quality optimisation in medical imaging

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    Following the successful OPTIMAX summer school held in Salford, 2013, we organised another OPTIMAX summer school in Lisbon during August, 2014. Sixty six people participated,comprising PhD, MSc and BSc students as well as tutors from the 5 European partners. Professional mix was drawn from engineering, medical physics / physics, radiography and occupational therapy. The summer school was hosted by the Lisbon School of Health Technology, Polytechnic Institute of Lisbon, Portugal. It was funded by Erasmus,aside one additional student who was funded by Nuffield.The summer school comprised of lectures and group work in which experimental research projects were conducted in six teams. Team project focus varied, with two concentrating on iterative reconstruction (CT), one into interface pressure mapping (between human body and imaging couch) whilst the remaining three focused to determining ways to reduce dose whilst preserving image quality for different projection radiography procedures. The summer school culminated in a conference, in which each team presented two oral papers.One paper reviewed the literature on their area of interest,whilst the other considered their experimental findings. The oral papers were also presented in written format, in journal article style, and after editing they have been included within this book. At the time of editing this book, several of the experimental papers had been submitted to conferences and some lecturers have commenced development work in order to make them fit for submission to journals

    Relación del filtro de cobre con la calidad de imagen y el producto dosis área en imágenes radiográficas de fantoma de pelvis pediátrico en el Hospital Docente Madre Niño San Bartolomé

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    Determina la relación del filtro de cobre con la calidad de imagen y el producto dosis área en imágenes radiográficas de fantoma de pelvis pediátrico en el Hospital Docente Madre Niño San Bartolomé. El estudio es de tipo experimental, enfoque cuantitativo, de nivel relacional, prospectivo y de corte transversal. Se utilizó 40 radiográficas obtenidas del fantoma de pelvis pediátrico con filtro (0.1mm, 0.2mm y 0.3mm) y sin filtro de cobre. Se observó de la CNR obtenida de las imágenes radiográficas del fantoma pediátrico que no hubo diferencias significativas entre no utilizar filtro de cobre que utilizando un filtro de 0.1mm de Cu (p=0.08), por lo que es posible obtener una calidad de imagen aceptable con este grosor de filtro. A diferencia de utilizar un filtro de 0.2mm y de 0.3mm donde se evidenció diferencias significativas (p=0.000) en comparación que sin utilizar filtro de cobre en el CNR. El DPA utilizando filtro de 0.1mm Cu resultó menor que sin utilizar filtro de Cu con diferencias significativas (p=0.000) al igual que utilizar filtro de 0.2 y 0.3 mm de Cu. El DPA disminuyó un 49.2% utilizando filtro de 0.1mm de Cu, mientras que utilizando un filtro de 0.2mm disminuyó un 63.5% y con un filtro de 0.3mm de Cu disminuyó un 72.8%. Se determinó que el filtro de cobre presenta una fuerte correlación con la calidad de imagen (rho=-0.831) y con el producto dosis-área (rho=-0.970), además presenta una fuerte correlación entre la calidad de imagen y el producto dosis-área (rho=0.856). Se concluye que el filtro de cobre con la calidad de imagen y el producto dosis área de la imágenes radiográficas obtenidas del fantoma de pelvis pediátrico tienen una relación significativa. El filtro de 0.1mm de Cu no disminuye significativamente la calidad de imagen en las imágenes obtenidas del fantoma de pelvis pediátrico reduciendo la dosis significativamente

    Image quality and radiation dose comparison of a computed radiography system and an amorphous silicon flat panel system in paediatric radiography: a phantom study

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    This purpose of this work was to investigate the patient radiation doses and image quality of a Philips/Agfa computed radiographic (CR) system and a Philips indirect-capture digital radiographic (DR) system in a paediatric setting. A CDRAD digital radiographic contrast-detail phantom was used to assess radiographic image quality. Perspex slabs of three different thicknesses (6, 11 and 16 cm) were used to simulate paediatric patients of three arbitrary ages. These phantoms, in conjunction with the CDRAD digital radiographic contrast-detail phantom, were imaged under three different conditions. The CDRAD Analyser software package was used to assess the quality of each image. The first experiment conducted was a comparison of the two systems under standard conditions, with beam filtration of aluminium and copper, as recommended in European Guidelines on Quality Criteria for Diagnostic Radiographic Images in Paediatrics (European Commission 1996b). Image quality was compared for each phantom size at three doses with the same entrance exposure used for both systems. A visual comparison of the resulting contrast detail curves showed the DR system generally outperformed the CR system, especially at the lowest two doses. A chi-square analysis of the targets detected generally confirmed this visual impression. The second experiment performed was to compare the two systems under the conditions used in routine clinical practice at PMH. As a result of additional beam filtration not generally being employed, the image quality of the CR system was similar to the DR system for the two smaller phantom sizes but with a major dose cost - effective doses higher by between 38% and 100%. A chi-square analysis of the targets detected showed the CR system to be significantly better than the DR system at two of three doses for the thinnest phantom and no significant difference at any doses for the intermediate phantom size. For the largest phantom size, additional filtration - although different - was used for the CR and DR systems and so the X-ray beam spectra were more similar. Consequently, the results for this phantom size reflected those from the experiment conducted under standard conditions, ie the effective doses for both systems were similar and the image quality of the DR system superior. The chi-square analysis s howed the DR system to be significantly better than the CR at all three dose levels. A third experiment was undertaken to compare doses between the two systems at 'equal' image quality. The CDRAD Analyser software specific image quality parameter, IQFinv, was held constant for both systems. The entrance exposures required to achieve this image quality were measured and then converted to effective doses using the dose calculation software package PCXMC 1.5. The DR system offered effective dose savings of between 28 and 42% for the three phantom sizes. Overall, this work suggests that a Philips flat-panel system is superior to an Agfa CR system in paediatric radiography. This result generally reflects the findings of other authors who have conducted similar studies in adult patient settings
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