Modelling and Simulations of a clinical PET-system using the GATE Monte Carlo software
(2018) MSFT01 20181Medical Physics Programme
- Abstract
- Introduction: The increased importance of PET imaging in the health care system
has lead to a constant need for improvement and optimisation of scanner systems
and their protocols. By utilising the features of the GATE Monte Carlo program one
can gain a better understanding of the limitations and possibilities of the system.
GATE together with the reconstruction software CASToR provides a link from simulation
of modeled system to reconstructed images. The aim of this thesis was to learn
the basics of the Monte Carlo method and how to operate GATE, to create a model
of a generic PET camera as a first approximation, perform simulations using 18F as
radioactive source and from simulated data reconstruct images using the CASToR
... (More) - Introduction: The increased importance of PET imaging in the health care system
has lead to a constant need for improvement and optimisation of scanner systems
and their protocols. By utilising the features of the GATE Monte Carlo program one
can gain a better understanding of the limitations and possibilities of the system.
GATE together with the reconstruction software CASToR provides a link from simulation
of modeled system to reconstructed images. The aim of this thesis was to learn
the basics of the Monte Carlo method and how to operate GATE, to create a model
of a generic PET camera as a first approximation, perform simulations using 18F as
radioactive source and from simulated data reconstruct images using the CASToR
software.
Material and method: The modelling of the generic camera used the G.E. PET/CT
Discovery-690 as a template. The NEMA 2012/IEC 2008 PET phantom was used to
perform a measurement on a G.E. PET/CT Discovery-690. CT-images from the measurement
were segmented and used as a phantom for simulations. Parameters such
as true-fraction, scatter-fraction, random-fraction, sensitivity and FWHM of three
spheres were compared between the measurement and the simulation. Simulations
of a human-like phantom (XCAT) were also performed and compared to images of
clinical exams with 18F-fluoride taken with a Philips Gemini TF PET/CT. Comparisons
were also made with a SIMIND SPECT simulation of the same phantom in
order to study qualitative differences between PET and SPECT.
Results: The general structure of the simulated image corresponds well with structures
in the images taken by the Philips PET/CT Gemini TF camera. The visual
comparison between GATE and SIMIND simulated images show similar geometrical
structures. True-fraction, scatter-fraction, random-fraction, sensitivity and FWHM
between the measurement, NEMA simulation 1 (energy window threshold 300 keV,
crystal energy resolution 20%) and NEMA simulations 2 (energy window threshold
425 keV, crystal energy resolution 8%) (M/S1/S2) were TF: 0.64/0.29/0.47, SF:
0.23/0.45/0.32, RF: 0.14/0.27/0.22, S: 5.1/8.3/4.0 cps/kBq, FWHM for three of the
sphere 36.0/36.4/35.9 mm, 27.5/25.4/24.2 mm and 16.0/14.5/14.7 mm. NEMA simulation
1 showed high values of scatter- and random-fraction and a large deviation
in sensitivity with 63% higher compared to the measurement. After increasing the
energy window threshold to 425 keV and crystal energy resolution to 8% (NEMA
simulation 2) the results from the measurements and simulations became more in
accordance with each other, but are still deviating.
Conclusion: GATE is a powerful tool simulating emission tomography. With the
modelling tools provided by the Geant4 kernel, GATE offers the user good possibilities
to model specific scanner geometry and set-up. While GATE provides good
simulating accuracy it comes at a cost of computational power and time - the need for
decreasing simulation time is thus necessary. The link between CASToR and GATE
creates a good chain from simulated data to reconstructed images. PET images show
better spatial resolution over SPECT images of identical distribution. The results are
satisfying with regards to visual properties, however, the quantifiable parameters
have a significant deviation that needs to be further investigated as to why the deviations
occur. By further improving the model GATE simulations could possibly act
as an option in patient studies in the future. (Less) - Popular Abstract (Swedish)
- I verksamheten för diagnostisk medicin är de bildgivande systemens funktion ett
ständigt område för förbättring. En metod för utveckling och förbättring av systemen
är genom simuleringar. I detta arbete har programmet GATE använts för att modellera
och simulera ett PET-system. Simuleringarna har sedan gjorts om till bilder
med programmet CASToR för att jämföra resultaten med verkliga undersökningar
och mätningar.
PET (Positron emissions tomografi) är en teknik som faller inom området för nuklearmedicin.
PET syftar till att studera hur kroppens celler fungerar, och är ett kraftfullt
verktyg för diagnostik av bland annat cancer. Med PET innebär att ett radioaktivt ämne
injiceras i en patient varpå det ämnet kommer fördela sig i... (More) - I verksamheten för diagnostisk medicin är de bildgivande systemens funktion ett
ständigt område för förbättring. En metod för utveckling och förbättring av systemen
är genom simuleringar. I detta arbete har programmet GATE använts för att modellera
och simulera ett PET-system. Simuleringarna har sedan gjorts om till bilder
med programmet CASToR för att jämföra resultaten med verkliga undersökningar
och mätningar.
PET (Positron emissions tomografi) är en teknik som faller inom området för nuklearmedicin.
PET syftar till att studera hur kroppens celler fungerar, och är ett kraftfullt
verktyg för diagnostik av bland annat cancer. Med PET innebär att ett radioaktivt ämne
injiceras i en patient varpå det ämnet kommer fördela sig i kroppen utefter funktionalitet.
Områden som fungerar abnormalt kommer antingen ta upp mer eller mindre av det radioaktiva
ämnet. Det radioaktiva ämnet kommer under undersökningen att sönderfalla,
vilket resulterar i fotonstrålning som kommer detekteras av PET-kameran. Informationen
kan sedan användas för att återskapa bilder och på så vis kan den medicinskt
kunniga avgöra huruvida patienten är frisk eller sjuk.
Ett sätt att arbeta med förbättringar inom PET-verksamheten är genom att simulera undersökningar
och mätningar. Monte Carlo metoden är ett sådant verktyg som baserat
på slumpmässigt genererade tal och genom kända sannolikheter för att en händelse
skall ske försöker förutse hur en sekvens av händelser hade sett ut om de hade skett i
verklighet. Med en tillräckligt kraftfull dator kan man simulera partikelstrålningen associerad
med PET-diagnostik, och på så sätt arbeta med att ständigt förbättra tekniken
och undersökningsprotokoll.
För att en simulering skall vara tillräckligt träffsäker i sina resultat måste beskrivningen
av simuleringen efterlikna verkligheten. Att således beskriva den simulerade världen
korrekt är av yttersta vikt. I fallet för en simulering av en PET-undersökning handlar det
då bland annat om kamerans uppbyggnad, korrekt beskriven fysik och detektorns svar
på en träff.
GATE är ett simuleringsprogram anpassad inom området för nuklearmedicin, detta program
ger användare friheten att skapa sin egen simuleringsgeometri och sedan studera
hur partiklar transporteras från start- till slutpunkt. Den insamlade information från
simuleringen kan användas för att studera underliggande faktorer, men även bildkvalitet
kan studeras genom en bildrekonstruktion. Ett program för detta är CASToR, utvecklat
för att återskapa bilder inom området för medicinsk bildvetenskap. Med dessa verktyg
för simulering och bildrekonstruering kan arbetet för utveckling och förbättring inom
området för PET-verksamheten fortskrida. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/8958979
- author
- Kalaitzidis, Philip
- supervisor
- organization
- course
- MSFT01 20181
- year
- 2018
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 8958979
- date added to LUP
- 2018-09-18 08:23:48
- date last changed
- 2018-09-18 08:23:48
@misc{8958979,
abstract = {{Introduction: The increased importance of PET imaging in the health care system
has lead to a constant need for improvement and optimisation of scanner systems
and their protocols. By utilising the features of the GATE Monte Carlo program one
can gain a better understanding of the limitations and possibilities of the system.
GATE together with the reconstruction software CASToR provides a link from simulation
of modeled system to reconstructed images. The aim of this thesis was to learn
the basics of the Monte Carlo method and how to operate GATE, to create a model
of a generic PET camera as a first approximation, perform simulations using 18F as
radioactive source and from simulated data reconstruct images using the CASToR
software.
Material and method: The modelling of the generic camera used the G.E. PET/CT
Discovery-690 as a template. The NEMA 2012/IEC 2008 PET phantom was used to
perform a measurement on a G.E. PET/CT Discovery-690. CT-images from the measurement
were segmented and used as a phantom for simulations. Parameters such
as true-fraction, scatter-fraction, random-fraction, sensitivity and FWHM of three
spheres were compared between the measurement and the simulation. Simulations
of a human-like phantom (XCAT) were also performed and compared to images of
clinical exams with 18F-fluoride taken with a Philips Gemini TF PET/CT. Comparisons
were also made with a SIMIND SPECT simulation of the same phantom in
order to study qualitative differences between PET and SPECT.
Results: The general structure of the simulated image corresponds well with structures
in the images taken by the Philips PET/CT Gemini TF camera. The visual
comparison between GATE and SIMIND simulated images show similar geometrical
structures. True-fraction, scatter-fraction, random-fraction, sensitivity and FWHM
between the measurement, NEMA simulation 1 (energy window threshold 300 keV,
crystal energy resolution 20%) and NEMA simulations 2 (energy window threshold
425 keV, crystal energy resolution 8%) (M/S1/S2) were TF: 0.64/0.29/0.47, SF:
0.23/0.45/0.32, RF: 0.14/0.27/0.22, S: 5.1/8.3/4.0 cps/kBq, FWHM for three of the
sphere 36.0/36.4/35.9 mm, 27.5/25.4/24.2 mm and 16.0/14.5/14.7 mm. NEMA simulation
1 showed high values of scatter- and random-fraction and a large deviation
in sensitivity with 63% higher compared to the measurement. After increasing the
energy window threshold to 425 keV and crystal energy resolution to 8% (NEMA
simulation 2) the results from the measurements and simulations became more in
accordance with each other, but are still deviating.
Conclusion: GATE is a powerful tool simulating emission tomography. With the
modelling tools provided by the Geant4 kernel, GATE offers the user good possibilities
to model specific scanner geometry and set-up. While GATE provides good
simulating accuracy it comes at a cost of computational power and time - the need for
decreasing simulation time is thus necessary. The link between CASToR and GATE
creates a good chain from simulated data to reconstructed images. PET images show
better spatial resolution over SPECT images of identical distribution. The results are
satisfying with regards to visual properties, however, the quantifiable parameters
have a significant deviation that needs to be further investigated as to why the deviations
occur. By further improving the model GATE simulations could possibly act
as an option in patient studies in the future.}},
author = {{Kalaitzidis, Philip}},
language = {{eng}},
note = {{Student Paper}},
title = {{Modelling and Simulations of a clinical PET-system using the GATE Monte Carlo software}},
year = {{2018}},
}