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A parallel solution for the numerical study of transcranial magnetic stimulation using the scalar potential finite differences method
Abstracts / Physica Medica 32 (2016) 284–339
field in field (FIF) and the forward planning IMRT with electronic compensator (EComp) using the Varian multileaf collimator. Materials and methods. Thirty patients were included in our study. Treatment plans were created and compared according to dose volume histogram in terms of dose homogeneity within the target volume and dose to OARs as well as conformity indices. Coverage improvement of FIF and EComp over 3DW was also quantified using dose improvement index. Results. Target volumes receiving 95% of the dose for the PTV were equal to 89.0 ± 4.1, 94.2 ± 2.19 and 96.8 ± 0.98 for 3DW, FIF and Ecomp respectively. Average value of the dose improvement index was equal to 8.92% and 5.97% for EComp and FIF respectively. No statistically significant difference in lung and heart sparing was observed. An advantage of FIF and EComp over 3DW was observed in the sparing of the contralateral breast. Conclusion. EComp and FIF proved to be superior to the 3DW technique with regard to improving dose homogeneity within the PTV and dose to normal tissues. Results showed that EComp is superior for a PTV volume P1500cc, or a separation P25 cm, or a combination of PTV volumes P1200cc and separation P22 cm. Disclosure. Authors have nothing to disclose. http://dx.doi.org/10.1016/j.ejmp.2016.07.213
CLINICAL COMMISSIONING OF THE INCISETM MULTILEAF COLLIMATOR FOR CYBERKNIFE M6TM SYSTEM Tarek El Kaissi, Tarraf Torfeh, Adam Shulman, Rabih Hammoud *, Noora Al-Hammadi Department of Radiation Oncology, National Center for Cancer Care & Research (NCCCR), Hamad Medical Corporation, Doha, Qatar ⇑ Corresponding author. Introduction. The National Center for Cancer Care and Research (NCCCR) at Hamad Medical Corporation in Qatar is amongst the first institutions in Asia and Europe to have the CyberKnifeÒ M6 FIM system (Accuray, Inc., Sunnyvale, CA, USA) including Fixed Collimators, Iris Variable Aperture Collimator and InCiseTM Multileaf Collimator. Purpose. To report our commissioning experiences of the CyberKnife M6 InCiseTM Multileaf Collimator system. Materials and methods. Accuray guidelines were used to conduct measurements. A detailed description of the equipment used, the mechanical alignment, the verification procedures, and the alignment of the detector motion with the radiation beam is described. Incise MLC testing was conducted as per Accuray procedure. Further MLC tests were developed to verify its feasibility under certain clinical settings. Results. Our results were within the manufacturer specifications. Results for both the Sun Nuclear Edge detector and PTW SRS diode 60018 were found to be comparable. Measurement conditions specified by Accuray were sufficient; however the use of a reference chamber introduced additional noise for the continuous profile acquisitions. As compared to fixed and IRIS collimators, the incise MLC produced acceptable results with an average of 20% decrease in treatment delivery time. Conclusions. Our results are amongst the first set of data reported on the InCiseTM MLC and were within the manufacturer specifications. These results will be used to develop a benchmark reference for periodic Quality Control (QC). Disclosure. Authors have nothing to disclose. http://dx.doi.org/10.1016/j.ejmp.2016.07.214
323
A PARALLEL SOLUTION FOR THE NUMERICAL STUDY OF TRANSCRANIAL MAGNETIC STIMULATION USING THE SCALAR POTENTIAL FINITE DIFFERENCES METHOD Stefanos Mavros, Theodoros Samaras * Department of Physics, Aristotle University of Thessaloniki, Greece Corresponding author.
⇑
Introduction. In transcranial magnetic stimulation (TMS) coils are used for the stimulation of human brain cortex. Numerous coil designs have been proposed and tested for different applications, both diagnostic and therapeutic. Purpose. The objective of the current study is the fast and accurate calculation of the induced electric field and current density distribution inside the human head, in order to allow for the design of coils fulfilling specific treatment requirements. Materials and methods. In order to avoid the intense computation of finite and boundary element meshes we developed a parallel in-house code, which implements a finite difference method. It calculates the magnetic scalar potential inside a human head model, given the electric conductivity distribution and the magnetic vector potential from 3D thin-wire coils. Tissue conductivity values can be derived either from volumetric data of realistic, voxelized human models, or from DICOM data segmentation. The numerical code was validated using analytical solutions of induced electric field in homogeneous conductive spherical models. Results. The simulation gives information on focality, depth of stimulus, peak value and orientation of the induced electric field for different coil topologies. These characteristics of the TMS are different for various areas of the brain cortex. Furthermore, they show not only intra- but also inter-subject changes that can easily be quantified. Conclusion. Our code can calculate the induced electric fields from TMS coils in the tissues of a human head model. The results can be derived within reasonable computational times and, therefore, the code can be used in the future to design coils with given specifications. Disclosure. Authors declare that they have no competing interests. http://dx.doi.org/10.1016/j.ejmp.2016.07.215
THERMOGRAPHIC IMAGE ANALYSIS IN SCOLIOSIS A. Papapouliou a,*, I. Kalatzis a, N. Kalyvas a, A. Skouroliakou b a Department of Biomedical Engineering, Technological Educational Institute of Athens, Greece b Department of Energy Technology Engineering, Technological Educational Institute of Athens, Greece ⇑ Corresponding author.
Introduction. Infrared thermal imaging is a useful tool for assessing skin temperature distribution. Scoliosis could result in alterations of the symmetry of skin temperature pattern in the back area of the trunk. Purpose. The purpose of the study is to develop thermographic image analysis techniques to obtain indices that characterize perispinal skin temperature distribution in children suffering from scoliosis. Materials and methods. Thermograms of the back area from 40 children (30 suffering from different types of scoliosis and 10 serving as the control group) were obtained. Image analysis methods were performed to obtain quantitative indices to characterize homogeneity as well as temperature differences on the thermograms. Obtained indices were evaluated using statistical methods as to their ability to
field in field (FIF) and the forward planning IMRT with electronic compensator (EComp) using the Varian multileaf collimator. Materials and methods. Thirty patients were included in our study. Treatment plans were created and compared according to dose volume histogram in terms of dose homogeneity within the target volume and dose to OARs as well as conformity indices. Coverage improvement of FIF and EComp over 3DW was also quantified using dose improvement index. Results. Target volumes receiving 95% of the dose for the PTV were equal to 89.0 ± 4.1, 94.2 ± 2.19 and 96.8 ± 0.98 for 3DW, FIF and Ecomp respectively. Average value of the dose improvement index was equal to 8.92% and 5.97% for EComp and FIF respectively. No statistically significant difference in lung and heart sparing was observed. An advantage of FIF and EComp over 3DW was observed in the sparing of the contralateral breast. Conclusion. EComp and FIF proved to be superior to the 3DW technique with regard to improving dose homogeneity within the PTV and dose to normal tissues. Results showed that EComp is superior for a PTV volume P1500cc, or a separation P25 cm, or a combination of PTV volumes P1200cc and separation P22 cm. Disclosure. Authors have nothing to disclose. http://dx.doi.org/10.1016/j.ejmp.2016.07.213
CLINICAL COMMISSIONING OF THE INCISETM MULTILEAF COLLIMATOR FOR CYBERKNIFE M6TM SYSTEM Tarek El Kaissi, Tarraf Torfeh, Adam Shulman, Rabih Hammoud *, Noora Al-Hammadi Department of Radiation Oncology, National Center for Cancer Care & Research (NCCCR), Hamad Medical Corporation, Doha, Qatar ⇑ Corresponding author. Introduction. The National Center for Cancer Care and Research (NCCCR) at Hamad Medical Corporation in Qatar is amongst the first institutions in Asia and Europe to have the CyberKnifeÒ M6 FIM system (Accuray, Inc., Sunnyvale, CA, USA) including Fixed Collimators, Iris Variable Aperture Collimator and InCiseTM Multileaf Collimator. Purpose. To report our commissioning experiences of the CyberKnife M6 InCiseTM Multileaf Collimator system. Materials and methods. Accuray guidelines were used to conduct measurements. A detailed description of the equipment used, the mechanical alignment, the verification procedures, and the alignment of the detector motion with the radiation beam is described. Incise MLC testing was conducted as per Accuray procedure. Further MLC tests were developed to verify its feasibility under certain clinical settings. Results. Our results were within the manufacturer specifications. Results for both the Sun Nuclear Edge detector and PTW SRS diode 60018 were found to be comparable. Measurement conditions specified by Accuray were sufficient; however the use of a reference chamber introduced additional noise for the continuous profile acquisitions. As compared to fixed and IRIS collimators, the incise MLC produced acceptable results with an average of 20% decrease in treatment delivery time. Conclusions. Our results are amongst the first set of data reported on the InCiseTM MLC and were within the manufacturer specifications. These results will be used to develop a benchmark reference for periodic Quality Control (QC). Disclosure. Authors have nothing to disclose. http://dx.doi.org/10.1016/j.ejmp.2016.07.214
323
A PARALLEL SOLUTION FOR THE NUMERICAL STUDY OF TRANSCRANIAL MAGNETIC STIMULATION USING THE SCALAR POTENTIAL FINITE DIFFERENCES METHOD Stefanos Mavros, Theodoros Samaras * Department of Physics, Aristotle University of Thessaloniki, Greece Corresponding author.
⇑
Introduction. In transcranial magnetic stimulation (TMS) coils are used for the stimulation of human brain cortex. Numerous coil designs have been proposed and tested for different applications, both diagnostic and therapeutic. Purpose. The objective of the current study is the fast and accurate calculation of the induced electric field and current density distribution inside the human head, in order to allow for the design of coils fulfilling specific treatment requirements. Materials and methods. In order to avoid the intense computation of finite and boundary element meshes we developed a parallel in-house code, which implements a finite difference method. It calculates the magnetic scalar potential inside a human head model, given the electric conductivity distribution and the magnetic vector potential from 3D thin-wire coils. Tissue conductivity values can be derived either from volumetric data of realistic, voxelized human models, or from DICOM data segmentation. The numerical code was validated using analytical solutions of induced electric field in homogeneous conductive spherical models. Results. The simulation gives information on focality, depth of stimulus, peak value and orientation of the induced electric field for different coil topologies. These characteristics of the TMS are different for various areas of the brain cortex. Furthermore, they show not only intra- but also inter-subject changes that can easily be quantified. Conclusion. Our code can calculate the induced electric fields from TMS coils in the tissues of a human head model. The results can be derived within reasonable computational times and, therefore, the code can be used in the future to design coils with given specifications. Disclosure. Authors declare that they have no competing interests. http://dx.doi.org/10.1016/j.ejmp.2016.07.215
THERMOGRAPHIC IMAGE ANALYSIS IN SCOLIOSIS A. Papapouliou a,*, I. Kalatzis a, N. Kalyvas a, A. Skouroliakou b a Department of Biomedical Engineering, Technological Educational Institute of Athens, Greece b Department of Energy Technology Engineering, Technological Educational Institute of Athens, Greece ⇑ Corresponding author.
Introduction. Infrared thermal imaging is a useful tool for assessing skin temperature distribution. Scoliosis could result in alterations of the symmetry of skin temperature pattern in the back area of the trunk. Purpose. The purpose of the study is to develop thermographic image analysis techniques to obtain indices that characterize perispinal skin temperature distribution in children suffering from scoliosis. Materials and methods. Thermograms of the back area from 40 children (30 suffering from different types of scoliosis and 10 serving as the control group) were obtained. Image analysis methods were performed to obtain quantitative indices to characterize homogeneity as well as temperature differences on the thermograms. Obtained indices were evaluated using statistical methods as to their ability to