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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.


Pet images

PET images


Examples of radiotracer

Examples of radiotracer

  • Radioactive chemical that can be injected into vein, swallowed or inhaled

  • Produced in cyclotron


Positron emission

Positron Emission


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.


Detection

Detection


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


Asli yildirim

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


Asli yildirim

General characteristics of detectors (5th Chapter)


Asli yildirim

Transfer all the radiation energy into detector mass, then we can observe it.


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


Example

Example


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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