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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

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asli yildirim

ASLI YILDIRIM

Medical applications of particle physics

General characteristics of detectors (5th Chapter)

applications of particle physics
APPLICATIONS OF PARTICLE PHYSICS
  • Medical applications such as producing X rays, protons, neutrons for diagnostic or treatment purposes.
  • Security such as nuclear waste monitoring
  • Industry
  • Biomedicine
medical imaging
MEDICAL IMAGING
  • X Rays
  • Computational Tomography
  • Magnetic Resonance Imaging
  • Ultrasound
  • Positron Emission Tomography
medical imaging1
MEDICAL IMAGING
  • X Rays
  • Computational Tomography
  • Magnetic Resonance Imaging
  • Ultrasound
  • Positron Emission Tomography
positron 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.

examples of radiotracer
Examples of radiotracer
  • Radioactive chemical that can be injected into vein, swallowed or inhaled
  • Produced in cyclotron
compton scattering and photoelectric absorption
Compton scattering and photoelectric absorption
  • Photon can loose energy through Compton scattering and scattering changes direction of photon
  • Under certain energy levels, photon can be absorbed by an atom.
scattered coincidence
Scattered coincidence

After first detection, one of detected photons has undergone Compton scattering

random coincidence
Random coincidence

Two photon from different annihilation

pet detector
PET Detector

Gamma rays

Photo sensor

Scintillation

crystal

Pre-Amplifier

Electronics

Its converts gamma rays to optical photons

It converts light into electrical signal

It prepares the signal for computational processing

scintillatior
Scintillatior
  • Spatial resolution
slide15

Thicker detectors improve sensitivity, but spatial resolution becomes worse

Thinner detectors give better resolution and better images but they have lower sensivity

detectors
Detectors
  • PMT
  • Solid state detectors
  • Photodiodes
  • Silicon PMT

Photodiodes

Avalanche photodiodes

PMT

PD

SPMT

SSD

properties of system
Properties of system
  • Spatial resolution is 1- 5 mm
  • Detection efficiency is higher than 30 %
  • Time resolution is 1-10 ns
  • Energy resolution is about 20 %
  • Can detect 107-108events
  • Expensive
computed tomography
Computed Tomography
  • Computed x-ray tomography is a technique in which the x-ray source and detector screen are moved in opposite directions
  • Also system moves around object to produce images slices that can be converted into 3d picture
sensivity
Sensivity
  • Capability of producing signal for a given radiation
    • Cross section for ionizing reactions
    • Detector mass
    • Detector noise
    • Protective material
detector response
Detector response

Response is relation between radiation energy and output signal.

Energy Resolution

Ability of distinguish very close energy levels

response function
Response function
  • Spectrum of pulses observed in detector when monoenergetic beam is sent to detector
  • Related to different interactions , design and geometry
dead time
Dead time
  • Required time for detector to process an event
  • All other electronics have their own dead times
extendable nonextendable dead times
Extendable-Nonextendable dead times

Non-extendable occurs when detector looses its sensitivity during dead time

Extendable occurs when detector does not loose its sensitivity during dead time

detector efficiency
Detectorefficiency
  • Intrinsic Efficiency
    • Related to radiation interacting with detector
  • Geometric Efficiency
    • Related to part of the radiation which is intercepted by detector.
references
References
  • W.R Leo, Techiniques for nuclear and particle physics experiments, pages 107-118
  • http://depts.washington.edu/nucmed/IRL/pet_intro/toc.html, accessed on 11/14/2010
  • www.bnl.gov/ncss/files/.../NucChemSummerSchool-072106-v2.ppt, accessed on 11/14/2010
  • www.physics.usyd.edu.au/astromed09/Talks/Day2/Cherry_invited.ppt, accessed on 11/14/2010
  • www.fnal.gov/gridfest/pdfs/benefits_factsheet.pdf, accessed on 11/14/2010
  • www.physics.ucla.edu/~arisaka/.../Physics89_PET.pdf, accessed on 11/14/2010
  • http://serc.carleton.edu/research_education/geochemsheets/techniques/CT.html, accessed on 11/14/2010
  • http://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
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