- Email: [email protected]
Quantification of positron emission tomography brain imaging using 18F-fallypride: a simulation
Abstracts of the 55th Annual Congress of the SAAPMB / Physica Medica 41, Suppl. 1 (2017) S1–S15
O21. Investigating nanodosimetric parameters in and around charged particle tracks S.A. Ngcezu * a , H. Rabus b , M. Bug b , D. van der Merwe a a University
of the Witwatersrand, Johannesburg, South Africa Bundesanstalt (PTB), Braunschweig, Germany * E-mail address: [email protected] (S.A. Ngcezu) b Physikalisch-Technische
Hadron therapy offers unique physical characteristics (ballistic accuracy) of energy deposition and biological phenomena (especially heavy ions) resulting from the high density of energy deposition. Contrasting the physical and biological characteristics of conventional photon and electron radiotherapy modalities to those of hadron therapies highlights a fundamental link between physics and radiobiology. The study of the physical characteristics of hadron radiation (and ultimately ionising radiation in general) and their relation to the radiobiological phenomena induced in living tissue is paramount to the extension of current knowledge in combating cancer in radiotherapy. To this end, in addition to the assessment of physical dose, a thorough treatment of the related radiobiology is required. The spatial proximity of radiation tracks relative to sensitive sites of the DNA and their orientation in space determines the amount of ionisations acting on the biological molecule and its surrounding. This study investigates the distribution of nanodosimetric parameters along and around radiation tracks (particularly protons), which will in turn correlate to the distribution of biological damage. Simulations are performed using the GEANT4-DNA extension toolkit that can simulate physics processes using models that can track step-by-step interactions of particles in liquid water down to the eV scale. The DNA target is modeled by a cylindrical volume of water with dimensions comparable to a DNA segment of 10 base pairs. These targets are placed at various positions in and around the track to map out the variation of nanodosimetric parameters. The results of this investigation present the distribution of nanodosimetric parameters (i.e. the probability to create 2 or more ionisations (F2), within 10 base pairs of DNA) in and around radiation tracks of charged particles.
O22. Quantification of positron emission tomography brain imaging using 18 F-fallypride: a simulation M.S. Mohlapholi * a,c , P. Dupont b,e , J. Warwick c,d , M.D. Du Toit a,c , C.J. Trauernicht a,c a Medical Physics Department, Tygerberg Academic Hospital, South Africa b KU Leuven, Belgium c Stellenbosch University, Western Cape, South Africa d Department of Nuclear Medicine, Tygerberg Hospital, South Africa e Department of Neurosciences, Laboratory for Cognitive Neurology, Belgium * E-mail address: [email protected] (M.S. Mohlapholi)
Introduction: 18 F-fallypride is of interest in neurological and psychiatric diseases to visualise dopamine D2 /D3 receptors in striatal and extrastriatal regions. Most techniques used currently to quantify positron emission tomography (PET) brain imaging using 18 F-fallypride are highly invasive and involve arterial blood sampling to construct an input function for the determination of model parameters. In the present study, we used mathematical simulations and investigated the possibility of eliminating blood sampling using graphical and several simplified methods to quantify 18 F-fallypride in the human brain. The specific uptake areas of interest used in this study for human brain are putamen (high uptake area), thalamus (moderate uptake area) and temporal cortex (low uptake area).
S7
Methods: All simulations were performed using Matlab (version R2013a (8.1.0.604) win 64-bit software; MathWorks, Inc.). Simulations of realistic measurements were performed by modelling varying frame duration, decay of the tracer, and varying noise levels, starting from ideal tissue curves. A modelled input function was used for the generation of ideal tissue curves. The graphical and different simplified methods were tested with the simulated tissue data. For the assessment, the results were analysed using a correlation analysis and a Blandt-Altman analysis, the relative error (%) and the 5th and 95th percentiles. Results: Our study showed that in most cases, the graphical and the simplified methods produced results nearly identical to the ground truth method. Simplified models were also found to be useful when continuous scanning of 2.5–3 hours (with no breaks between scans) was used. Conclusion: Simplified models can be used to provide useful estimate of dopamine transporters that are comparable to methods using arterial blood sampling. This balances quantitative accuracy and allows less invasive procedures.
O23. Recent developments impacting traceability in dosimetry measurement in South Africa S. Jozela *, R. Pepenene, S.A. Ngcezu National Metrology Institute of South Africa, Pretoria, South Africa * E-mail address: [email protected] (S. Jozela) The need for international traceability for radiation dose measurements has been understood since the early nineteen-sixties when the acute need for high dosimetric accuracy was recognized, particularly in external beam radiation therapy, where the outcome of treatment is highly dependent on the radiation dose delivered to the patient. The Basic Safety Standards (BSS) requires that equipment used for measurement of radiation be properly maintained, tested and calibrated, at appropriate intervals, against standards that are traceable to national or international reference standards. In South Africa, according to the Hazardous Substances Act, 1973 (Act No. 15 of 1973), the regulatory body requires the authority holders to ensure that their radiation detectors are calibrated by an approved body. An approved body should maintain reference radiation fields that are traceable to a national standards body. This traceability chain provides quality assurance of the equipment used in industry where the lives of radiation workers and patients are at risk. Through the measurement units and measurement standards act No. 18, of 2006, the National Metrology Institute of South Africa (NMISA) was mandated to provide South African industry and environmental, health and safety sectors with fit-for-purpose measurements and measurement standards. In keeping up with this mandate, NMISA has over the past five years developed and improved its measurement capabilities through the government funded recapitalisation project. Old and outdated equipment were replaced with modern ones. This has also resulted in reduced measurement uncertainties in absorbed dose to water calibrations in Co-60 to better than 1.0% (k = 2) and air kerma measurements uncertainties ranging from 0.8% to 1.5% (k =2) for Co-60 and medium X-rays.
O24. The commissioning and implementation of total body irradiation at Livingstone Hospital A. Rule *, L. Moore Livingstone Hospital, Port Elizabeth, South Africa * E-mail address: [email protected] (A. Rule) Introduction: Total body irradiation (TBI) was commissioned and
O21. Investigating nanodosimetric parameters in and around charged particle tracks S.A. Ngcezu * a , H. Rabus b , M. Bug b , D. van der Merwe a a University
of the Witwatersrand, Johannesburg, South Africa Bundesanstalt (PTB), Braunschweig, Germany * E-mail address: [email protected] (S.A. Ngcezu) b Physikalisch-Technische
Hadron therapy offers unique physical characteristics (ballistic accuracy) of energy deposition and biological phenomena (especially heavy ions) resulting from the high density of energy deposition. Contrasting the physical and biological characteristics of conventional photon and electron radiotherapy modalities to those of hadron therapies highlights a fundamental link between physics and radiobiology. The study of the physical characteristics of hadron radiation (and ultimately ionising radiation in general) and their relation to the radiobiological phenomena induced in living tissue is paramount to the extension of current knowledge in combating cancer in radiotherapy. To this end, in addition to the assessment of physical dose, a thorough treatment of the related radiobiology is required. The spatial proximity of radiation tracks relative to sensitive sites of the DNA and their orientation in space determines the amount of ionisations acting on the biological molecule and its surrounding. This study investigates the distribution of nanodosimetric parameters along and around radiation tracks (particularly protons), which will in turn correlate to the distribution of biological damage. Simulations are performed using the GEANT4-DNA extension toolkit that can simulate physics processes using models that can track step-by-step interactions of particles in liquid water down to the eV scale. The DNA target is modeled by a cylindrical volume of water with dimensions comparable to a DNA segment of 10 base pairs. These targets are placed at various positions in and around the track to map out the variation of nanodosimetric parameters. The results of this investigation present the distribution of nanodosimetric parameters (i.e. the probability to create 2 or more ionisations (F2), within 10 base pairs of DNA) in and around radiation tracks of charged particles.
O22. Quantification of positron emission tomography brain imaging using 18 F-fallypride: a simulation M.S. Mohlapholi * a,c , P. Dupont b,e , J. Warwick c,d , M.D. Du Toit a,c , C.J. Trauernicht a,c a Medical Physics Department, Tygerberg Academic Hospital, South Africa b KU Leuven, Belgium c Stellenbosch University, Western Cape, South Africa d Department of Nuclear Medicine, Tygerberg Hospital, South Africa e Department of Neurosciences, Laboratory for Cognitive Neurology, Belgium * E-mail address: [email protected] (M.S. Mohlapholi)
Introduction: 18 F-fallypride is of interest in neurological and psychiatric diseases to visualise dopamine D2 /D3 receptors in striatal and extrastriatal regions. Most techniques used currently to quantify positron emission tomography (PET) brain imaging using 18 F-fallypride are highly invasive and involve arterial blood sampling to construct an input function for the determination of model parameters. In the present study, we used mathematical simulations and investigated the possibility of eliminating blood sampling using graphical and several simplified methods to quantify 18 F-fallypride in the human brain. The specific uptake areas of interest used in this study for human brain are putamen (high uptake area), thalamus (moderate uptake area) and temporal cortex (low uptake area).
S7
Methods: All simulations were performed using Matlab (version R2013a (8.1.0.604) win 64-bit software; MathWorks, Inc.). Simulations of realistic measurements were performed by modelling varying frame duration, decay of the tracer, and varying noise levels, starting from ideal tissue curves. A modelled input function was used for the generation of ideal tissue curves. The graphical and different simplified methods were tested with the simulated tissue data. For the assessment, the results were analysed using a correlation analysis and a Blandt-Altman analysis, the relative error (%) and the 5th and 95th percentiles. Results: Our study showed that in most cases, the graphical and the simplified methods produced results nearly identical to the ground truth method. Simplified models were also found to be useful when continuous scanning of 2.5–3 hours (with no breaks between scans) was used. Conclusion: Simplified models can be used to provide useful estimate of dopamine transporters that are comparable to methods using arterial blood sampling. This balances quantitative accuracy and allows less invasive procedures.
O23. Recent developments impacting traceability in dosimetry measurement in South Africa S. Jozela *, R. Pepenene, S.A. Ngcezu National Metrology Institute of South Africa, Pretoria, South Africa * E-mail address: [email protected] (S. Jozela) The need for international traceability for radiation dose measurements has been understood since the early nineteen-sixties when the acute need for high dosimetric accuracy was recognized, particularly in external beam radiation therapy, where the outcome of treatment is highly dependent on the radiation dose delivered to the patient. The Basic Safety Standards (BSS) requires that equipment used for measurement of radiation be properly maintained, tested and calibrated, at appropriate intervals, against standards that are traceable to national or international reference standards. In South Africa, according to the Hazardous Substances Act, 1973 (Act No. 15 of 1973), the regulatory body requires the authority holders to ensure that their radiation detectors are calibrated by an approved body. An approved body should maintain reference radiation fields that are traceable to a national standards body. This traceability chain provides quality assurance of the equipment used in industry where the lives of radiation workers and patients are at risk. Through the measurement units and measurement standards act No. 18, of 2006, the National Metrology Institute of South Africa (NMISA) was mandated to provide South African industry and environmental, health and safety sectors with fit-for-purpose measurements and measurement standards. In keeping up with this mandate, NMISA has over the past five years developed and improved its measurement capabilities through the government funded recapitalisation project. Old and outdated equipment were replaced with modern ones. This has also resulted in reduced measurement uncertainties in absorbed dose to water calibrations in Co-60 to better than 1.0% (k = 2) and air kerma measurements uncertainties ranging from 0.8% to 1.5% (k =2) for Co-60 and medium X-rays.
O24. The commissioning and implementation of total body irradiation at Livingstone Hospital A. Rule *, L. Moore Livingstone Hospital, Port Elizabeth, South Africa * E-mail address: [email protected] (A. Rule) Introduction: Total body irradiation (TBI) was commissioned and