7 results on '"Speller, Robert"'
Search Results
2. Multivariate data analysis for drug identification using energy-dispersive x-ray diffraction
- Author
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Cook, Emily J., Pani, Silvia, George, Leah, Hardwick, Sheila, Horrocks, Julie A., and Speller, Robert D.
- Subjects
Multivariate analysis -- Methods ,Drugs -- Atomic properties ,X-rays -- Diffraction ,X-rays -- Methods ,Business ,Electronics ,Electronics and electrical industries - Abstract
Preliminary studies have shown the effectiveness of multivariate analysis (MVA) for drug identification from energy-dispersive X-ray diffraction patterns. A statistical model to predict drug content from the diffraction profile of a sample of mixed composition was developed by applying MVA to both experimental and simulated data. Separate data-sets were used for building and testing the models. Both experimental and simulated data were used and the MVA predictions compared. Experimental data included diffraction patterns from small (5 mm diameter) drug samples with various cutting agents, acquired with a HPGe detector; simulated data included diffraction patterns of samples including materials simulating drugs (i.e., materials featuring sharp diffraction peaks in the relevant momentum transfer range) and typical packaging materials. Both a HPGe detector (energy resolution 0.7 keV at 59.5 keV) and a CZT detector (energy resolution 4 keV at all energies) were simulated. MVA was used to predict the drug content. In all cases different statistics were applied to assess the detection limits of the models. Multivariate analysis has proved effective in both identifying the presence of a drug and its concentration. Due to the large contribution to peak broadening given by angular resolution, no significant decrease in accuracy has been found when using CZT with respect to HPGe data. Index Terms--Diffraction, drugs, multivariate analysis, x-ray detectors.
- Published
- 2009
3. Modelling an energy-dispersive X-Ray diffraction system for drug detection
- Author
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Pani, Silvia, Cook, Emily, Horrocks, Julie, George, Leah, Hardwick, Sheila, and Speller, Robert
- Subjects
Detectors -- Usage ,Drug dealing -- Research ,Drug traffic -- Research ,X-rays -- Diffraction ,X-rays -- Models ,Business ,Electronics ,Electronics and electrical industries - Abstract
A system for drug detection using X-ray diffraction is currently being developed by the DILAX collaboration. A simulation program for modelling the response of an energy-dispersive X-ray diffraction system has been developed, with the two-fold aim of selecting possible configurations prior to experimental tests and of generating data for statistical models for prediction of drug content. Simulated data showed a good agreement with experimental results. The data showed that the main factor affecting the shape of the diffraction pattern is the thickness of the sample. Scatter angle and detector energy resolution have a smaller effect on the diffraction pattern. This suggests that cheaper, room-temperature detectors can be used for a drug detection system without any loss in sensitivity and specificity. Index Terms--Nondestructive testing, X-ray imaging, diffraction, geometric modelling.
- Published
- 2009
4. Performance evaluation of 98 CZT sensors for their use in gamma-ray imaging
- Author
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Dedek, Nicolas, Speller, Robert D., Spendley, Paul, and Horrocks, Julie A.
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Imaging systems -- Methods ,Gamma rays -- Properties ,Radiation warning systems -- Usage ,Sensors -- Usage ,Business ,Electronics ,Electronics and electrical industries - Abstract
98 SPEAR sensors from eV Products have been evaluated for their use in a portable Compton camera. The sensors have a 5 mm x 5 mm x 5 mm CdZnTe crystal and are provided together with a preamplifier. The energy resolution was studied in detail for all sensors and was found to be 6% on average at 59.5 keV and 3% on average at 662 keV. The standard deviations of the corresponding energy resolution distributions are remarkably small (0.6% at 59.5 keV, 0.7% at 662 keV) and reflect the uniformity of the sensor characteristics. For a possible outside use the temperature dependence of the sensor performances was investigated for temperatures between 15 and 45 deg Celsius. A linear shift in calibration with temperature was observed. The energy resolution at low energies (81 keV) was found to deteriorate exponentially with temperature, while it stayed constant at higher energies (356 keV). A Compton camera built of these sensors was simulated. To obtain realistic energy spectra a suitable detector response function was implemented. To investigate the angular resolution of the camera a [sup.137]Cs point source was simulated. Reconstructed images of the point source were compared for perfect and realistic energy and position resolutions. The angular resolution of the camera was found to be better than 10 deg. Index Terms--CdZnTe, Compton camera, CZT, energy resolution, gamma-ray, imaging, simulation.
- Published
- 2008
5. Design and characterization of the I-ImaS multi-element x-ray detector system
- Author
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Griffiths, Jennifer A., Metaxas, Marinos G., Royle, Gary J., Venanzi, Cristian, Esbrand, Colin, Cavouras, Dionisis, Fant, Andrea, Gasiorek, Przemyslaw, Georgiou, Harris, Hall, Geoff, Jones, John, Leaver, James D.G., Longo, Renata, Manthos, Nicos, Noy, Matthew, Ostby, Joar Martin, Rokvic, Tatjana, Schulerud, Helene, Theodoridis, Sergios, Triantis, Frixos A., Turchetta, Renato, and Speller, Robert D.
- Subjects
Complementary metal oxide semiconductors -- Design and construction ,Imaging systems -- Technology application ,Imaging systems -- Methods ,Technology application ,Business ,Electronics ,Electronics and electrical industries - Abstract
I-ImaS (Intelligent Imaging Sensors) is a European project aiming to produce new, intelligent x-ray imaging systems using novel APS sensors to create optimal diagnostic images. Initial systems have been constructed for medical imaging; specifically mammography and dental encephalography. However, the I-ImaS system concept could be applied to all areas of x-ray imaging, including homeland security and industrial QA. The I-ImaS system intelligence is implemented by the use of APS technology and FPGAs, allowing real-time analysis of data during image acquisition. This gives the system the capability to perform as an on-the-fly adaptive imaging system, with the potential to create images with maximum diagnostic information within given dose constraints. The I-ImaS system uses a scanning linear array of scintillator-coupled 1.5-D CMOS Active Pixel Sensors to create a full 2-D x-ray image of an object. This paper describes the parameters considered when choosing the scintillator elements of the detectors. A study of the positioning of the sensors to form a linear detector is also considered, along with a discussion of the potential losses in image quality associated with creating a linear sensor by tiling many smaller sensors. Preliminary results show that the detectors have sufficient performance to be used successfully in the initial mammographic and encephalographic I-ImaS systems that are currently under construction. Index Terms--CMOS, scintillators, x-ray imaging.
- Published
- 2008
6. X-ray performance evaluation of the dexela cmos aps x-ray detector using monochromatic synchrotron radiation in the mammographic energy range
- Author
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P. Liaparinos, Steve Naday, Spencer Gunn, Alessandro Olivo, Nicola Sodini, Anastasios C. Konstantinidis, Diego Dreossi, Magdalena B. Szafraniec, Luigi Rigon, Alan McArthur, Robert D. Speller, Giuliana Tromba, Konstantinidis, Anastasios C., Szafraniec, Magdalena B., Rigon, Luigi, Tromba, Giuliana, Dreossi, Diego, Sodini, Nicola, Liaparinos, Panagiotis F., Naday, Steve, Gunn, Spencer, Mcarthur, Alan, Speller, Robert D., and Olivo, Alessandro
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Physics ,CMOS sensor ,Nuclear and High Energy Physics ,Physics::Instrumentation and Detectors ,business.industry ,synchrotron radiation ,Monte Carlo method ,Detector ,Complementary metal-oxide-semiconductor (CMOS) ,X-ray detector ,Synchrotron radiation ,Scintillator ,Detective quantum efficiency ,Nuclear Energy and Engineering ,Optical transfer function ,digital mammography ,Optoelectronics ,image quality ,Electrical and Electronic Engineering ,business - Abstract
Digital detectors based on complementary metal-oxide-semiconductors (CMOS) active pixel sensor (APS) technology have been introduced recently in many scientific applications. This work is focused on the X-ray performance evaluation of a novel CMOS APS detector in low energy medical imaging applications using monochromatic synchrotron radiation (i.e., 17-35 keV), which also allows studying how the performance varies with energy. The CMOS sensor was coupled to a Thallium-activated structured cesium iodide (CsI:Tl) scintillator and the detector's X-ray performance evaluation was carried out in terms of sensitivity, presampling modulation transfer function (pMTF), normalized noise power spectrum (NNPS) and the resulting detective quantum efficiency (DQE). A Monte Carlo simulation was used to validate the experimentally measured low frequency DQE. Finally, the effect of iodine's secondary generated K-fluorescence X-rays on pMTF and DQE results was evaluated. Good agreement (within 5%) was observed between the Monte Carlo and experimentally measured low frequency DQE results. A CMOS APS detector was characterized for the first time over a wide range of low energies covering the mammographic spectra. The detector's performance is limited mainly by the detectability of the scintillator. Finally, we show that the current data could be used to calculate the detector's pMTF, NNPS and DQE for any mammographic spectral shape within the investigated energies.
- Published
- 2013
7. A multi-element detector system for intelligent imaging: I-ImaS
- Author
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J. Leaver, Dimosthenis E. Bolanakis, Dionisis Cavouras, Nikolaos Manthos, D. Machin, A. Asimidis, P. Gasiorek, C. Venanzi, Gary Royle, M. Khaleeq, C Esbrand, M. Noy, Harris V. Georgiou, Renato Turchetta, Geoffrey Hall, S. Greenwood, Anna Bergamaschi, Robert D. Speller, Helene Schulerud, H. Verheij, P.F. van der Stelt, A. Fant, Frixos A Triantis, M Metaxas, Sergios Theodoridis, Renata Longo, Jennifer Griffiths, J.M. Ostby, Gang Li, J. Jones, Orale Radiologie (OUD, ACTA), IEEE, Griffiths, Jennifer A., Metaxas, Marinos G., Royle, Gary J., Venanzi, Cristian, Esbrand, Colin, van der Stelt, Paul F., Verheij, Han, Li, Gang, Turchetta, Renato, Fant, Andrea, Gasiorek, Przemyslaw, Theodoridis, Sergio, Georgiou, Harri, Cavouras, Dionissi, Hall, Geoff, Noy, Matthew, Jones, John, Leaver, Jame, Machin, Davy, Greenwood, S, Khaleeq, M, Schulerud, Helene, Ostby, Joar M., Triantis, Frixo, Asimidis, Asimaki, Bolanakis, Dimo, Manthos, Niko, Longo, Renata, Bergamaschi, Anna, and Speller, Robert D.
- Subjects
EXPOSURE CONTROL ,RADIOGRAPHY ,medicine.diagnostic_test ,Computer science ,business.industry ,Detector ,Characterization (materials science) ,Data acquisition ,Upgrade ,Medical imaging ,medicine ,Data analysis ,Mammography ,Computer vision ,Artificial intelligence ,Field-programmable gate array ,business ,Computer hardware - Abstract
I-ImaS is a European project aiming to produce new, intelligent x-ray imaging systems using novel APS sensors to create optimal diagnostic images. Initial systems concentrate on mammography and encephalography. Later development will yield systems for other types of radiography such as industrial QA and homeland security. The I-ImaS system intelligence, due to APS technology and FPGAs, allows real-time analysis of data during image acquisition, giving the capability to build a truly adaptive imaging system with the potential to create images with maximum diagnostic information within given dose constraints. A companion paper deals with the DAQ system and preliminary characterization. This paper considers the laboratory x-ray characterization of the detector elements of the I-ImaS system. The characterization of the sensors when tiled to form a strip detector will be discussed, along with the appropriate correction techniques formulated to take into account the misalignments between individual sensors within the array. Preliminary results show that the detectors have sufficient performance to be used successfully in the initial mammographic and encephalographic I-ImaS systems under construction and this paper will further discuss the testing of these systems and the iterative processes used for intelligence upgrade in order to obtain the optimal algorithms and settings
- Published
- 2006
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