A Positive Electron Tomography/Computed Tomography devise was installed in theX-ray section at US Linköping in May 2007. Positive Electron Tomography examinations with 18F-fluoro-deoxy-glucose are mainly used for tumor examinations. During 2007 occurred approximately 200 examinations and in 2008 600 are planned. Today there are two reconstruction methods commercially available, Filtered Back projection and Maximum Likelihood Expectation Maximiza tion, used in the faster version called Ordered Subsets Expectation Maximization. The image quality in Positive Electron Tomography depends on the choice of reconstruction method and the settings of its parameters. We have performed a physical phantom study with Positive Electron Tomography to determine optimal parameters for the iterative reconstruction algorithm Ordered Subsets Expectation Maximization. To find out whether or not the quality of the image can be improved, so that the patient received radiation dose and/or examination time can be lowered. The phantom used was a NEMA IEC Body PhantomTM, designed to mimic smallhot lesions typical in 18F, Fluorine-18 PET, and all calculations were done according to the NEMA NU2-2001 protocol. The main conclusion from this project is that a higher level of contrast can be reached, compared to the one clinically obtained today. Using more iterations then recommended from the manufacturer. / I maj 2007 installerades en Positiv Elektron Tomografi /DatoriseradTomografi-kamera, PET/CT, i Röntgenavdelningen Linköping US. PET med 18F-fluoro-deoxy-glucose används huvudsakligen för tumörundersökningar.2007 genomfördes ca 200 undersökningar, och för 2008 är ytterligare 600 planerade. Idag finns två olika bildrekonstruktionsmetoder kliniskt tillgängliga; Filtered Back projection och Maximum Likelihood Expectation Maximization, där den  vidareutvecklade versionen kallad Ordered Subsets Expectation Maximizationanvänds. Bildkvalitén från en Positive Electron Tomographykamera påverkas av valet av rekonstruktionsmetod och dess ingående parametrar. I detta projekt har en fantomstudie genomförts med syfte att bestämma de optimala parametrarna för den iterativa metoden Ordered Subsets Expectation Maximization. För att utreda huruvida stråldosen och/eller undersöknings tiden kan minskas. Det testfantom som användes var en NEMA IEC Body PhantomTM. Projektet följde metoden angiven i NEMA NU2-2001 protokollet. Det resultaten visar är att de rekommenderade inställningarna från tillverkaren inte är de optimala.

A Positive Electron Tomography/Computed Tomography devise was installed in the X-ray section at US Linköping in May 2007. Positive Electron Tomography examinations with 18F-fluoro-deoxyglucose are mainly used for tumor examinations. During 2007 occurred approximately 200 examinations and in 2008 600 are planned.Today there are two reconstruction methods commercially available, Filtered Back projection and Maximum Likelihood Expectation Maximiza tion, used in the faster version called Ordered Subsets Expectation Maximization. The image quality in Positive Electron Tomography depends on the choice of reconstruction method and the settings of its parameters. We have performed a physical phantom study with Positive Electron Tomography to determine optimal parameters for the iterativereconstruction algorithm Ordered Subsets Expectation Maximization. To find out whether or not the quality of the image can be improved, so that the patient received radiation dose and/or examination time can be lowered. The phantom used was a NEMA IEC Body PhantomTM, designed to mimic small hot lesions typicalin 18F, Fluorine-18 PET, and all calculations were done according to the NEMA NU2-2001 protocol. The main conclusion from this project is that a higher level of contrastcan be reached, compared to the one clinically obtained today. Using more iterations then recommended from the manufacturer.

<p>A Positive Electron Tomography/Computed Tomography devise was installed in theX-ray section at US Linköping in May 2007. Positive Electron Tomography examinations with 18F-fluoro-deoxy-glucose are mainly used for tumor examinations. During 2007 occurred approximately 200 examinations and in 2008 600 are planned. Today there are two reconstruction methods commercially available, Filtered Back projection and Maximum Likelihood Expectation Maximiza tion, used in the faster version called Ordered Subsets Expectation Maximization. The image quality in Positive Electron Tomography depends on the choice of reconstruction method and the settings of its parameters. We have performed a physical phantom study with Positive Electron Tomography to determine optimal parameters for the iterative reconstruction algorithm Ordered Subsets Expectation Maximization. To find out whether or not the quality of the image can be improved, so that the patient received radiation dose and/or examination time can be lowered. The phantom used was a NEMA IEC Body PhantomTM, designed to mimic smallhot lesions typical in 18F, Fluorine-18 PET, and all calculations were done according to the NEMA NU2-2001 protocol.</p><p>The main conclusion from this project is that a higher level of contrast can be reached, compared to the one clinically obtained today. Using more iterations then recommended from the manufacturer.</p> / <p>I maj 2007 installerades en Positiv Elektron Tomografi /DatoriseradTomografi-kamera, PET/CT, i Röntgenavdelningen Linköping US. PET med 18F-fluoro-deoxy-glucose används huvudsakligen för tumörundersökningar.2007 genomfördes ca 200 undersökningar, och för 2008 är ytterligare 600 planerade. Idag finns två olika bildrekonstruktionsmetoder kliniskt tillgängliga; Filtered Back projection och Maximum Likelihood Expectation Maximization, där den  vidareutvecklade versionen kallad Ordered Subsets Expectation Maximizationanvänds. Bildkvalitén från en Positive Electron Tomographykamera påverkas av valet av rekonstruktionsmetod och dess ingående parametrar.</p><p>I detta projekt har en fantomstudie genomförts med syfte att bestämma de optimala parametrarna för den iterativa metoden Ordered Subsets Expectation Maximization. För att utreda huruvida stråldosen och/eller undersöknings tiden kan minskas. Det testfantom som användes var en NEMA IEC Body PhantomTM. Projektet följde metoden angiven i NEMA NU2-2001 protokollet. Det resultaten visar är att de rekommenderade inställningarna från tillverkaren inte är de optimala.</p>

<p>A Positive Electron Tomography/Computed Tomography devise was installed in the X-ray section at US Linköping in May 2007. Positive Electron Tomography examinations with 18F-fluoro-deoxyglucose are mainly used for tumor examinations. During 2007 occurred approximately 200 examinations and in 2008 600 are planned.Today there are two reconstruction methods commercially available, Filtered Back projection and Maximum Likelihood Expectation Maximiza tion, used in the faster version called Ordered Subsets Expectation Maximization. The image quality in Positive Electron Tomography depends on the choice of reconstruction method and the settings of its parameters. We have performed a physical phantom study with Positive Electron Tomography to determine optimal parameters for the iterativereconstruction algorithm Ordered Subsets Expectation Maximization. To find out whether or not the quality of the image can be improved, so that the patient received radiation dose and/or examination time can be lowered. The phantom used was a NEMA IEC Body PhantomTM, designed to mimic small hot lesions typicalin 18F, Fluorine-18 PET, and all calculations were done according to the NEMA NU2-2001 protocol.</p><p>The main conclusion from this project is that a higher level of contrastcan be reached, compared to the one clinically obtained today. Using more iterations then recommended from the manufacturer.</p>