School Work

Optimization of the parameters in the electronics of a PET detector.

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The aim of this project is to fi nd the best integration time which minimizes degrading e fects such us pile-up and thus gives the best energy resolution and quality image. Once the optimum integration time is known the next step is to find the best phoswich separation, that is, to distinguish between the counts in the first layer (LYSO) and the counts in the second layer (GSO).
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  Optimization of the parameters in theelectronics of a PET detector. (Optimizaci´on de los par´ametros de la electr´onica de un detectorpara PET) Ana Mar´ıa Barrag´an MonteroJuly 4, 2013 Academic project (TAD, Trabajo Acad´emicamente Dirigido).Departamento de Fsica Atmica, Nuclear y Molecular.Supervised by:Dr. Jose Manuel Ud´ıas Moinelo. (Director)Esteban Picado Sand´ı (Co-Director)Jacobo Cal Gonz´alez (Co-Director)  Contents 1. Introduction 52. Physical background for PET 6 2.1. Beta-decay and  e  −  e + annihilation . . . . . . . . . . . . . . . . . . . . . 62.2. Positron range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82.3. Interaction of gamma radiation with matter . . . . . . . . . . . . . . . . 82.3.1. Photoelectric absorption . . . . . . . . . . . . . . . . . . . . . . . 82.3.2. Rayleigh and Compton scattering . . . . . . . . . . . . . . . . . . 82.3.3. Pair production . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3. Detectors 9 3.1. Scintillators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103.2. Photomultipliers tubes PMT . . . . . . . . . . . . . . . . . . . . . . . . . 11 4. Influence of acquisition and processing factors on image quality 12 4.1. Positron range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.2. Non-collinearity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.3. Scattering and interaction with several crystals. Crystal identification(Anger logic) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134.4. Pile-up and dead time . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154.5. Energy resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164.6. Depth of interaction (DOI) . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5. Set-up 18 5.1. Description of the data set . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6. Aims of this work 197. Results. 20 7.1. Pulse integration. Optimum integration time. . . . . . . . . . . . . . . . 207.2. Phoswich separation. Delay integration method. . . . . . . . . . . . . . . 247.3. Crystal identification. Individual spectrum. Histogram and calibration. . 28 8. Comparison of results for different integration times. 329. Conclusions. 32A. Appendix 35 A.1.  pulse  −  procesor.f  , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35A.2.  phoswich total.f   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38A.3.  xyanger.f   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39A.4.  phoswich  1 crystal.f   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42A.5.  histo.f   . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 432  A.6.  sum spectra.sh  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 453  Motivation and acknowledges Some months ago I started the final year of my degree in Physics and I wanted to dosomething different, something more practical and exciting than a common subject inthe course. Indeed, I wanted to be closer to research world and work by my own, so Idecided to try a supervised project (TAD, trabajo acadmicamente dirigido). I chose theAtomic and Nuclear Physics Department because I became very interested in nuclearphysics. I have to thank Jose Manuel Ud´ıas for being always ready to supervise anddirect my project in any of the topics which considered. At the beginning I had in minda very different topic, a more theoretical one (’ electron scattering by nuclei’), however,I realised that I needed to do something more applied. I began then with my projectabout PET tecnique. Now, I am very happy I decided to do this work and that I chosethis topic because I feel I learnt a lot. I have learnt a lot about PET but also, andeven more important, about programming, data analysis and processing, Linux, For-tran, gnuplot,... At the end, I have developed a lot of new and good skills making me abetter scientist. I can say it has been totally worth it :)I want to thank Esteban Picado for his help at the beginning, when I was a bit lostabout what to do, for showing me the way to start and how to reach the importantpoints in the project. I also want to thank Jacobo Cal for always being ready to answerany question or helping me with the program codes, and all the people in the laboratoryfor maintaining always such a good atmosphere.To finish, I want to dedicate this work to all my close friends during these five yearsof my degree, for being always there, making me happy, they know who they are.4

Da Pped Beams

Jul 26, 2017

Winning in 2014

Jul 26, 2017
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