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ASLI YILDIRIM. Medical applications of particle physics General characteristics of detectors (5 th Chapter). APPLICATIONS OF PARTICLE PHYSICS. Medical applications such as producing X rays, protons, neutrons for diagnostic or treatment purposes. Security such as nuclear waste monitoring - PowerPoint PPT Presentation
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ASLI YILDIRIM
Medical applications of particle physics
General characteristics of detectors (5th Chapter)ASLI YILDIRIMAPPLICATIONS OF PARTICLE PHYSICSMedical applications such as producing X rays, protons, neutrons for diagnostic or treatment purposes.Security such as nuclear waste monitoringIndustry Biomedicine
MEDICAL IMAGINGX RaysComputational TomographyMagnetic Resonance ImagingUltrasoundPositron Emission Tomography
MEDICAL IMAGINGX RaysComputational TomographyMagnetic Resonance ImagingUltrasoundPositron Emission Tomography
Positron Emission Tomography
* After injecting radiotracer to human body, gamma rays produced and detected.* This information is transformed into images by using tomography tecniniques.PET images
Examples of radiotracer Radioactive chemical that can be injected into vein, swallowed or inhaledProduced in cyclotron
Positron Emission
Compton scattering and photoelectric absorptionPhoton can loose energy through Compton scattering and scattering changes direction of photon
Under certain energy levels, photon can be absorbed by an atom.
Detection
Scattered coincidence
After first detection, one of detected photons has undergone Compton scatteringRandom coincidence Two photon from different annihilation
PET DetectorPhoto sensor
Pre-AmplifierElectronics Scintillation crystalGamma raysIts converts gamma rays to optical photonsIt converts light into electrical signalIt prepares the signal for computational processing Scintillatior
Spatial resolution
Thinner detectors give better resolution and better images but they have lower sensivityThicker detectors improve sensitivity, but spatial resolution becomes worseDetectorsPMT
Solid state detectors
Photodiodes
Silicon PMT
PhotodiodesAvalanche photodiodes
PMT
SPMT
PD
SSDProperties of system Spatial resolution is 1- 5 mmDetection efficiency is higher than 30 % Time resolution is 1-10 nsEnergy resolution is about 20 % Can detect 107-108 eventsExpensive
Computed TomographyComputed x-ray tomography is a technique in which the x-ray source and detector screen are moved in opposite directionsAlso system moves around object to produce images slices that can be converted into 3d picture
General characteristics of detectors (5th Chapter)
Transfer all the radiation energy into detector mass, then we can observe it.SensivityCapability of producing signal for a given radiationCross section for ionizing reactionsDetector massDetector noiseProtective material
Detector response Response is relation between radiation energy and output signal. Energy ResolutionAbility of distinguish very close energy levels
Response functionSpectrum of pulses observed in detector when monoenergetic beam is sent to detectorRelated to different interactions , design and geometryExample
Dead time Required time for detector to process an eventAll other electronics have their own dead times
Extendable-Nonextendable dead times
Extendable occurs when detector does not loose its sensitivity during dead timeNon-extendable occurs when detector looses its sensitivity during dead timeDetector efficiency Intrinsic EfficiencyRelated to radiation interacting with detector
Geometric EfficiencyRelated to part of the radiation which is intercepted by detector.
ReferencesW.R Leo, Techiniques for nuclear and particle physics experiments, pages 107-118http://depts.washington.edu/nucmed/IRL/pet_intro/toc.html, accessed on 11/14/2010www.bnl.gov/ncss/files/.../NucChemSummerSchool-072106-v2.ppt, accessed on 11/14/2010www.physics.usyd.edu.au/astromed09/Talks/Day2/Cherry_invited.ppt, accessed on 11/14/2010www.fnal.gov/gridfest/pdfs/benefits_factsheet.pdf, accessed on 11/14/2010www.physics.ucla.edu/~arisaka/.../Physics89_PET.pdf, accessed on 11/14/2010http://serc.carleton.edu/research_education/geochemsheets/techniques/CT.html, accessed on 11/14/2010http://www.fda.gov/Radiation-EmittingProducts/RadiationEmittingProductsandProcedures/MedicalImaging/MedicalX-Rays/ucm115317.htm#5, accessed on 11/14/2010 www.jsgreen.tamu.edu/427%205%20Medical%20imaging.ppt, accessed on 11/14/2010