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A comparative study of the cytogenetic responses for homo- and heterogeneous exposures of human T-lymphocytes
S2
Abstracts/Physica Medica 31 (2015) S1–S14
O.4 A COMPARATIVE STUDY OF THE CYTOGENETIC RESPONSES FOR HOMO- AND HETEROGENEOUS EXPOSURES OF HUMAN T-LYMPHOCYTES
O.6 SCRIPTING A VARIAN IGRT COUCH ON PINNACLE FOR TREATMENT PLANNING PURPOSES
P.R. Beukes *,a, J. Depuydt b, H. Thierens b, A. Vral b, J.P. Slabbert a. a Radiation Biophysics Division, NRF iThemba LABS, South Africa; b Department of Basic Medical Sciences, Ghent University, Belgium
J.J. Botha *, H. Burger, C. Trauernicht. Department of Medical Physics, Groote Schuur Hospital, Cape Town, South Africa
Introduction: Biological dosimetry is central in the assessment and mitigation of large scale radiation accidents and occupational over-exposures. Several biological endpoints have been successfully employed to estimate doses for both in vitro and in vivo exposures. Comprehensive statistical analysis of the dose–response parameters can yield more information than mere quantitative dose estimates. Qualitative aspects of the radiation type and dose distribution can be predicted, which is important for real world biodosimetry applications. Materials and Methods: Equivalent total body dose estimates were prepared for blood samples exposed to 60Co gamma-rays at doses ranging from 1 to 6 Gy. The samples were subsequently diluted with sham irradiated blood to yield a range of total body dose equivalents between 0 and 4 Gy. Dicentric formation frequency in lymphocyte metaphase spreads was quantified using a semi-automated image analysis system. Results: Cytogenetic aberration frequencies for each irradiation and dilution condition were translated to whole body dose values using dose– response curves established in the laboratory. The measured values were in agreement with the calculated estimates (P-value > 0.05). The overdistribution of chromosomal aberrations correlated with the non-uniformity of the radiation applied; which is reflected by the indices of dispersion (σ2/ μ > 1.2) for heterogeneously exposed samples. Conclusion: The degree of non-uniformity of exposures can be predicted on the basis of over-dispersion parameters calculated using advanced statistical analysis of dicentric frequency distributions. Keywords: Biodosimetry, Dicentric, Dispersion index, Metafer
O.5 VERIFICATION OF A MONTE CARLO SIMULATED SIEMENS SYMBIA SPECT/CT M. Booyens *, M. Morphis, J. Van Staden, H. du Raan. Department of Medical Physics, University of the Free State, Bloemfontein, South Africa Introduction: Monte Carlo (MC) simulations can be employed in nuclear medicine to improve the qualitative and quantitative accuracy of planar and Single Photon Emission Computed Tomography (SPECT) images. In this study a Siemens Symbia T2 SPECT/CT system was modelled using the SIMIND MC code. Planar images were simulated and acquired to determine the system performance characteristics in terms of energy resolution, system spatial resolution and sensitivity. SPECT image quality was assessed in terms of image contrast, uniformity and resolution. The aim of the study was to determine if the SIMIND MC code could be used to accurately simulate acquisitions of images obtained with a Siemens Symbia T2 SPECT/CT system. Materials and Methods: Experimental data were acquired according to National Electrical Manufacturers Association standards. CT images of each setup were acquired and segmented. Segmentation eliminates slight pixel to pixel variations, producing areas of uniform density. Simulations were performed using segmented images. The experimental and simulated results were compared. Results: The energy spectra for Tc-99m in air compared favourably. Experimental and simulated values were energy resolution: 9.4% and 9.9% respectively, extrinsic spatial resolution: 7.6 mm and 7.1 mm respectively, sensitivity: 97.4 cps/MBq and 97.0 cps/MBq respectively. Extrinsically measured and simulated image contrast, uniformity and resolution were analysed and found to compare well. Conclusion: The results of this study show that the SIMIND MC code can be used with confidence to accurately simulate planar and SPECT projections of the Siemens Symbia T2 SPECT/CT. Future studies will determine the accuracy of the SIMIND MC code for simulations with high energy radioactive Au-198. Keywords: SIMIND Monte Carlo Simulations, SPECT/CT, Segmentation
Introduction: During treatment planning the Linac couch must be added as a structure on the plan, so that its density is taken into account for dose calculations. Scripting is a programming language that supports the writing of programs for a software environment that automate the execution of tasks. Scripting the couch top on the Pinnacle Treatment Planning System (TPS) replaces manual contouring of the couch as a structure, thus streamlining the planning process. The couch is irregular in shape and the aim was to model the full couch accurately in terms of shape, dimensions, and attenuation characteristics. Materials and Methods: The actual transmission of the 6 MV Linac beam through the Varian IGRT couch top was measured at different gantry angles. Because the shape of the couch is irregular superior to inferior, as well as anterior to posterior, it was decided to use a slice-by-slice approach to model it. The user specifies on the TPS where the top of the couch must be. The script then determines on which part of the couch each slice is and then draws the relevant couch contour, taking into account any offsets that the user specified. For the scripting, Pinnacle scripting and Python were used. Results: The couch transmission was measured at gantry angles from 120° to 180°. The couch transmission as determined by the TPS at the same gantry angles after the script was implemented differed by no more than ±0.5% for the 6 MV beam at 180° and 150°, and by no more than 2.6% for the gantry angle of 120°. Conclusion: Scripting the Varian IGRT couch top on Pinnacle was achievable and the script runs fast and reliably. The script is deployed for testing by the planning RTTs. Keywords: Couch, IGRT, Script, Pinnacle
O.7 IN-HOUSE SOLUTION FOR THE MANAGEMENT OF PROTOCOLS AND STANDARD OPERATING PROCEDURES J.J. Botha *. Department of Medical Physics, Groote Schuur Hospital, Cape Town, South Africa Introduction: Protocols and standard operating procedures (SOPs) are an important part of maintaining good standards in the department. They make it possible for all staff to perform tasks in a uniform and standard way, especially with tasks which are not routinely or frequently performed. However, protocols and SOPs need to be regularly checked to ensure they are still current and valid and there needs to be a uniform format and a central repository of the department’s protocols and SOPs so that all staff can easily access them. The aim was to develop a software solution to help manage the protocols and SOPs in terms of ease of use, ease of access, and improved control over the regular revision of these documents. Materials and Methods: The current system was evaluated and found to be very disjointed and unmanaged. Every section had some protocols and SOPs in some folder on a computer and it was impossible to determine which protocols and SOPs were still in use and which were the latest versions. This also made it difficult for staff members to access relevant protocols and SOPs. It was decided to write a computer program using SQL Server and C# to manage the protocols and SOPs. Results: The Protocol Manager is being developed and phase one is being tested in the department. Phase two will include email notifications to the staff members as reminders when protocols and SOPs are due for revision. The program consists of a database and various checks to improve the integrity of the protocols and SOPs, and help ensure regular reviews of them. Conclusion: The Protocol Manager has the potential to greatly improve the management of and the control over the huge number of protocols and SOPs required in a department. Keywords: Software solution, Protocols, standard operating procedures
Abstracts/Physica Medica 31 (2015) S1–S14
O.4 A COMPARATIVE STUDY OF THE CYTOGENETIC RESPONSES FOR HOMO- AND HETEROGENEOUS EXPOSURES OF HUMAN T-LYMPHOCYTES
O.6 SCRIPTING A VARIAN IGRT COUCH ON PINNACLE FOR TREATMENT PLANNING PURPOSES
P.R. Beukes *,a, J. Depuydt b, H. Thierens b, A. Vral b, J.P. Slabbert a. a Radiation Biophysics Division, NRF iThemba LABS, South Africa; b Department of Basic Medical Sciences, Ghent University, Belgium
J.J. Botha *, H. Burger, C. Trauernicht. Department of Medical Physics, Groote Schuur Hospital, Cape Town, South Africa
Introduction: Biological dosimetry is central in the assessment and mitigation of large scale radiation accidents and occupational over-exposures. Several biological endpoints have been successfully employed to estimate doses for both in vitro and in vivo exposures. Comprehensive statistical analysis of the dose–response parameters can yield more information than mere quantitative dose estimates. Qualitative aspects of the radiation type and dose distribution can be predicted, which is important for real world biodosimetry applications. Materials and Methods: Equivalent total body dose estimates were prepared for blood samples exposed to 60Co gamma-rays at doses ranging from 1 to 6 Gy. The samples were subsequently diluted with sham irradiated blood to yield a range of total body dose equivalents between 0 and 4 Gy. Dicentric formation frequency in lymphocyte metaphase spreads was quantified using a semi-automated image analysis system. Results: Cytogenetic aberration frequencies for each irradiation and dilution condition were translated to whole body dose values using dose– response curves established in the laboratory. The measured values were in agreement with the calculated estimates (P-value > 0.05). The overdistribution of chromosomal aberrations correlated with the non-uniformity of the radiation applied; which is reflected by the indices of dispersion (σ2/ μ > 1.2) for heterogeneously exposed samples. Conclusion: The degree of non-uniformity of exposures can be predicted on the basis of over-dispersion parameters calculated using advanced statistical analysis of dicentric frequency distributions. Keywords: Biodosimetry, Dicentric, Dispersion index, Metafer
O.5 VERIFICATION OF A MONTE CARLO SIMULATED SIEMENS SYMBIA SPECT/CT M. Booyens *, M. Morphis, J. Van Staden, H. du Raan. Department of Medical Physics, University of the Free State, Bloemfontein, South Africa Introduction: Monte Carlo (MC) simulations can be employed in nuclear medicine to improve the qualitative and quantitative accuracy of planar and Single Photon Emission Computed Tomography (SPECT) images. In this study a Siemens Symbia T2 SPECT/CT system was modelled using the SIMIND MC code. Planar images were simulated and acquired to determine the system performance characteristics in terms of energy resolution, system spatial resolution and sensitivity. SPECT image quality was assessed in terms of image contrast, uniformity and resolution. The aim of the study was to determine if the SIMIND MC code could be used to accurately simulate acquisitions of images obtained with a Siemens Symbia T2 SPECT/CT system. Materials and Methods: Experimental data were acquired according to National Electrical Manufacturers Association standards. CT images of each setup were acquired and segmented. Segmentation eliminates slight pixel to pixel variations, producing areas of uniform density. Simulations were performed using segmented images. The experimental and simulated results were compared. Results: The energy spectra for Tc-99m in air compared favourably. Experimental and simulated values were energy resolution: 9.4% and 9.9% respectively, extrinsic spatial resolution: 7.6 mm and 7.1 mm respectively, sensitivity: 97.4 cps/MBq and 97.0 cps/MBq respectively. Extrinsically measured and simulated image contrast, uniformity and resolution were analysed and found to compare well. Conclusion: The results of this study show that the SIMIND MC code can be used with confidence to accurately simulate planar and SPECT projections of the Siemens Symbia T2 SPECT/CT. Future studies will determine the accuracy of the SIMIND MC code for simulations with high energy radioactive Au-198. Keywords: SIMIND Monte Carlo Simulations, SPECT/CT, Segmentation
Introduction: During treatment planning the Linac couch must be added as a structure on the plan, so that its density is taken into account for dose calculations. Scripting is a programming language that supports the writing of programs for a software environment that automate the execution of tasks. Scripting the couch top on the Pinnacle Treatment Planning System (TPS) replaces manual contouring of the couch as a structure, thus streamlining the planning process. The couch is irregular in shape and the aim was to model the full couch accurately in terms of shape, dimensions, and attenuation characteristics. Materials and Methods: The actual transmission of the 6 MV Linac beam through the Varian IGRT couch top was measured at different gantry angles. Because the shape of the couch is irregular superior to inferior, as well as anterior to posterior, it was decided to use a slice-by-slice approach to model it. The user specifies on the TPS where the top of the couch must be. The script then determines on which part of the couch each slice is and then draws the relevant couch contour, taking into account any offsets that the user specified. For the scripting, Pinnacle scripting and Python were used. Results: The couch transmission was measured at gantry angles from 120° to 180°. The couch transmission as determined by the TPS at the same gantry angles after the script was implemented differed by no more than ±0.5% for the 6 MV beam at 180° and 150°, and by no more than 2.6% for the gantry angle of 120°. Conclusion: Scripting the Varian IGRT couch top on Pinnacle was achievable and the script runs fast and reliably. The script is deployed for testing by the planning RTTs. Keywords: Couch, IGRT, Script, Pinnacle
O.7 IN-HOUSE SOLUTION FOR THE MANAGEMENT OF PROTOCOLS AND STANDARD OPERATING PROCEDURES J.J. Botha *. Department of Medical Physics, Groote Schuur Hospital, Cape Town, South Africa Introduction: Protocols and standard operating procedures (SOPs) are an important part of maintaining good standards in the department. They make it possible for all staff to perform tasks in a uniform and standard way, especially with tasks which are not routinely or frequently performed. However, protocols and SOPs need to be regularly checked to ensure they are still current and valid and there needs to be a uniform format and a central repository of the department’s protocols and SOPs so that all staff can easily access them. The aim was to develop a software solution to help manage the protocols and SOPs in terms of ease of use, ease of access, and improved control over the regular revision of these documents. Materials and Methods: The current system was evaluated and found to be very disjointed and unmanaged. Every section had some protocols and SOPs in some folder on a computer and it was impossible to determine which protocols and SOPs were still in use and which were the latest versions. This also made it difficult for staff members to access relevant protocols and SOPs. It was decided to write a computer program using SQL Server and C# to manage the protocols and SOPs. Results: The Protocol Manager is being developed and phase one is being tested in the department. Phase two will include email notifications to the staff members as reminders when protocols and SOPs are due for revision. The program consists of a database and various checks to improve the integrity of the protocols and SOPs, and help ensure regular reviews of them. Conclusion: The Protocol Manager has the potential to greatly improve the management of and the control over the huge number of protocols and SOPs required in a department. Keywords: Software solution, Protocols, standard operating procedures