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Glenn Sjoden - One of the best experts on this subject based on the ideXlab platform.
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SU‐FF‐T‐81: Adaptive Differencing Schemes with Parallel Computing for Detailed SN Solutions of a Co‐60 Radiotherapy Unit
Medical Physics, 2006Co-Authors: Ahmad Khaled Al-basheer, Glenn SjodenAbstract:Purpose: To apply deterministic techniques to provide a numerical solution for the 3‐D integro‐differential form of the Boltzmann transport equation using the discrete ordinates (SN) method for a Radiotherapy Unit. Method and Materials: Comparisons were made between deterministic and Monte Carlo simulations considering angular quadrature, spatial discretization (also spatial differencing), and cross section library selection. In order to assess these issues, we simulated the 60 Co beam from a standard EldoradoRadiotherapy Unit. In addition, we simulated the gantry, air gaps, and a water phantom. A 3‐D spatial distribution was generated to yield a 24 ‘z‐level’ model of 150,000 fine mesh cells. To accurately compare our deterministic results with Monte Carlo, we considered an equivalent MCNP5 model with ENDF/B‐VI cross‐section data libraries and volumetric flux (F4) tallies along the central axis of the model. Results: Overall, deterministic SN results yielded good agreement with Monte Carlo results within the Monte Carlo stochastic error for the reference case. At the same time, the parallel SN model provided a full 3D‐scalar flux distribution over the entire geometry within an acceptable running time. To accurately represent the radiation transport, a quadrature level of at least S24 was required with an added ordinate splitting refinement of 6 directions of interest. These results where obtained when the Directional Theta‐Weighted (DTW) differencing scheme was locked for the regions with low density material (air regions), and the adaptive differencing scheme with upgrades up to the Exponential‐Directional Weighted (EDW) differencing scheme was prescribed for higher density regions. Conclusions: The discrete ordinates (SN) method provides a viable alternative to the Monte Carlo method for solving the Boltzmann transport equation. With the proper discretization, an adaptive differencing scheme, and suitable quadratures with ordinate splitting, the SN method is a useful tool in determining the resulting radiation transport throughout a Radiotherapy Unit.
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su ff t 81 adaptive differencing schemes with parallel computing for detailed sn solutions of a co 60 Radiotherapy Unit
Medical Physics, 2006Co-Authors: Ahmad Khaled Albasheer, Glenn SjodenAbstract:Purpose: To apply deterministic techniques to provide a numerical solution for the 3‐D integro‐differential form of the Boltzmann transport equation using the discrete ordinates (SN) method for a Radiotherapy Unit. Method and Materials: Comparisons were made between deterministic and Monte Carlo simulations considering angular quadrature, spatial discretization (also spatial differencing), and cross section library selection. In order to assess these issues, we simulated the 60 Co beam from a standard EldoradoRadiotherapy Unit. In addition, we simulated the gantry, air gaps, and a water phantom. A 3‐D spatial distribution was generated to yield a 24 ‘z‐level’ model of 150,000 fine mesh cells. To accurately compare our deterministic results with Monte Carlo, we considered an equivalent MCNP5 model with ENDF/B‐VI cross‐section data libraries and volumetric flux (F4) tallies along the central axis of the model. Results: Overall, deterministic SN results yielded good agreement with Monte Carlo results within the Monte Carlo stochastic error for the reference case. At the same time, the parallel SN model provided a full 3D‐scalar flux distribution over the entire geometry within an acceptable running time. To accurately represent the radiation transport, a quadrature level of at least S24 was required with an added ordinate splitting refinement of 6 directions of interest. These results where obtained when the Directional Theta‐Weighted (DTW) differencing scheme was locked for the regions with low density material (air regions), and the adaptive differencing scheme with upgrades up to the Exponential‐Directional Weighted (EDW) differencing scheme was prescribed for higher density regions. Conclusions: The discrete ordinates (SN) method provides a viable alternative to the Monte Carlo method for solving the Boltzmann transport equation. With the proper discretization, an adaptive differencing scheme, and suitable quadratures with ordinate splitting, the SN method is a useful tool in determining the resulting radiation transport throughout a Radiotherapy Unit.
Kiki Theodorou - One of the best experts on this subject based on the ideXlab platform.
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A comparison of Monte Carlo simulation with experimental dosimetric techniques for a 6 MV stereotactic Radiotherapy Unit.
Journal of B.U.ON. : official journal of the Balkan Union of Oncology, 2004Co-Authors: I. Tsougos, Kiki Theodorou, M. A. Bazioglou, Sotirios Stathakis, Constantin KappasAbstract:PURPOSE To compare Monte Carlo simulation with conventional dosimetry techniques for stereotactic Radiotherapy (SRT), since accurate dosimetry of narrow photon beams is very complicated and has often been questioned, mainly due to the lack of lateral electronic equilibrium and uncertainty in beam energy in terms of steep dose gradients. MATERIALS AND METHODS In this work a Monte Carlo (MC, EGS4) simulation for dosimerty study was performed for the 6MV home made SRT Unit of the University Hospital of Patras (Hellas). The results were compared with conventional small field dosimetry techniques such as ionization chamber, TLD's, and films (conventional and radiochromic). Hence, a comparison of many of the dosimetric techniques currently being used in small field dosimetry was attempted. RESULTS It was shown that all techniques are in reasonable agreement (within -/+ 2%) and that Monte Carlo can be used as a reliable reference for the dosimetry of the SRT beams, especially where lateral electronic equilibrium does not exist, as long as accurate simulation can be achieved. CONCLUSION This study is only limited by the insurance of accurate simulation of the linear accelerator, which can be a difficult task since it is limited by the availability of the manufacturer's designs and the availability of computers and computer time for adequate runs, but it could become a useful tool for Monte Carlo simulations, as it contains detailed analysis of the run parameters and component modules selection.
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Graphical treatment simulation and automated collision detection for conformal and stereotactic Radiotherapy treatment planning
Medical Physics, 2001Co-Authors: Miltiadis F. Tsiakalos, Eduard Schrebmann, Kiki Theodorou, Constantin KappasAbstract:The purpose of this work is to develop a “room’s eye view” graphical simulation program with an automated collision detection option, to assist a treatment planning user to visualize the treatment setup checking at the same time the feasibility of his plan. The program simulates the treatment process using accurate three-dimensional graphical models of the gantry, table, and that of an average patient. This allows the use of any mechanical movement concerning the Radiotherapy Unit. The simulation of the mechanical movements and their limitations are according to IEC standards and thus compatible with any Radiotherapy machine. Graphical methods for collision detection between the models guarantee speed and accuracy. The module simulates the treatment setup with accuracy better than 2° for any tested case. When a collision takes place a warning message is displayed. In this paper a software tool is developed that can be used as a stand-alone program or embedded in any treatment planning system. The visualization of the treatment fields prior to treatment permits the geometric feasibility of the plan, thus adding one more step toward the automation of the treatment process.
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development of a prototype stereotactic Radiotherapy radiosurgery Unit in english
Medical Physics, 2001Co-Authors: Kiki TheodorouAbstract:In this thesis the design, construction, and installation of a new linac-based stereotactic Radiotherapy Unit is described. The design requirements were a noninvasive head fixation providing accurate patient repositioning with high reproducibility during multiple fractions. The noninvasive immobilization frame we constructed is used for both localization and for treatments. The immobilization is achieved using three stable locations: the upper dentition, the bridge of the nose, and the back of the neck. This fixation ensures adequate immobilization. The maximum relocation error measured on 22 patients in more than 200 mountings was 1.2 mm. The beam collimation is achieved by eight nondivergent–parallel–circular collimators (diameters between 1–4 cm) and the photon energy used is 6 MV. Concerning dosimetry, a methodology has been developed for dose measurements at the beam central axis. The methodology consists of the irradiation of an ionization chamber with its logitudinal axis parallel to the beam central axis. A correction factor is applied that includes the beam dose profile averaged over the chamber volume. The applied methodology proved to be compatible with film and TLDdosimetry and it has been tested successfully to 4 stereotactic Units at different European centers. Furthermore, a new design of head phantom accommodates various dosimeters—ion chambers, TLDs, and films. A three-dimensional treatment planning system, the X-STING, was developed. It is dedicated for stereotactic Radiotherapy. In addition to standard features, it includes innovative algorithms for image correlation (between CT and angiographic images with volumetric accuracy of 3%) and a complete model of the treatment machine.
Raja K Muralidhar - One of the best experts on this subject based on the ideXlab platform.
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su gg t 312 intrabeam intraoperative Radiotherapy Unit quality assurarance measurements with edr2 films and radiological imaging technology
Medical Physics, 2010Co-Authors: Raja K MuralidharAbstract:Purpose: EDR2‐QA films were developed for patient dosimetry in Intraoperative Radiotherapy. In this study a method to evaluate the isotropy, PDD, Isodose and beam deflection using EDR2‐QA films and a vidar scanner with RIT Software was developed and tested. Methods and Materials: Intrabeam System is (50KeV, 40μA) intraoperative Radiotherapy Unit. X‐ray source (XRS) equipped with a 10 cm long (o/ 3.2 mm) probe. Five Films were irradiated for one minute each at a distance of 5cm from the source in all 5 directions (0°, 90°, 180°, 270° and perpendicular to the source) with flat surface facing towards the source. Percentage depth doses were derived by exposing the film vertically down from the source.Results: Horizontal and vertical profiles from films in all directions were taken and compared with the help of RIT software. A difference of 0.7% was found between the profiles at 12cm from the central axis. PDD'S were obtained with the film (which was kept vertically down from the source) by normalizing the values at 2 cm depth (known dose) from the surface. These PDD'S proved l/r3 and can be implemented on CT.Dose distributions were also derived by RIT software. Films were exposed at different distances from the source and found that these doses are comparable with the doses obtained from Ionization chamber (<1%). Conclusion: Some of these QA procedures can be incorporated as periodic and some can be incorporated as regular QA procedures before taking any patient. These film measurements proved and shown the simple way of checking the Isotropy, PDD, Isodose and beam deflection. These tests also useful to take beam data for planning systems to view the dose on CTimages in 2D and 3D, which is not available on the present system.
Oliver Jakel - One of the best experts on this subject based on the ideXlab platform.
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first experiences with the implementation of the european standard en 62304 on medical device software for the quality assurance of a Radiotherapy Unit
Radiation Oncology, 2014Co-Authors: Angelika Hoss, Christian Lampe, Ralf Panse, Benjamin Ackermann, Jakob Naumann, Oliver JakelAbstract:According to the latest amendment of the Medical Device Directive standalone software qualifies as a medical device when intended by the manufacturer to be used for medical purposes. In this context, the EN 62304 standard is applicable which defines the life-cycle requirements for the development and maintenance of medical device software. A pilot project was launched to acquire skills in implementing this standard in a hospital-based environment (in-house manufacture). The EN 62304 standard outlines minimum requirements for each stage of the software life-cycle, defines the activities and tasks to be performed and scales documentation and testing according to its criticality. The required processes were established for the pre-existent decision-support software FlashDumpComparator (FDC) used during the quality assurance of treatment-relevant beam parameters. As the EN 62304 standard implicates compliance with the EN ISO 14971 standard on the application of risk management to medical devices, a risk analysis was carried out to identify potential hazards and reduce the associated risks to acceptable levels. The EN 62304 standard is difficult to implement without proper tools, thus open-source software was selected and integrated into a dedicated development platform. The control measures yielded by the risk analysis were independently implemented and verified, and a script-based test automation was retrofitted to reduce the associated test effort. After all documents facilitating the traceability of the specified requirements to the corresponding tests and of the control measures to the proof of execution were generated, the FDC was released as an accessory to the HIT facility. The implementation of the EN 62304 standard was time-consuming, and a learning curve had to be overcome during the first iterations of the associated processes, but many process descriptions and all software tools can be re-utilized in follow-up projects. It has been demonstrated that a standards-compliant development of small and medium-sized medical software can be carried out by a small team with limited resources in a clinical setting. This is of particular relevance as the upcoming revision of the Medical Device Directive is expected to harmonize and tighten the current legal requirements for all European in-house manufacturers.
Khumaidi Khumaidi - One of the best experts on this subject based on the ideXlab platform.
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PROCEDURE OF 3D CONFORMAL Radiotherapy ON SQUAMOUS CELL CARCINOMA CASE IN ORBITAL REGION IN Radiotherapy Unit OF DR. SARDJITO YOGYAKARTA HOSPITAL
Jurnal Imejing Diagnostik (JImeD), 2018Co-Authors: Nova Aditya Surya Irawan, Gatot Murti Wibowo, Khumaidi KhumaidiAbstract:Background: This study aims to determine the procedures, techniques, reasons and evaluation of 3D conformal Radiotherapy of squamous cell carcinoma case in the orbital region with additional bolus that has been done in the Radiotherapy Unit of Dr. Sardjito Yogyakarta Hospital. In addition, from this research also to find out how the visually tumor response to the radiation that has been given and there are limits of research for tumor responses made observations from the beginning of radiation to the completion of radiation. Methods: This type of research is qualitative with a case study approach. The data was collected in November-December 2017 at Radiotherapy Unit of Dr. Sardjito Yogyakarta Hospital by observation methodology, interview with Radiation Oncologist Specialist, Medical Physicist and Radiographer. the data obtained from the study were analyzed by an interactive model, creating the interview transcripts subsequently reduced and processed within the type of open coding, given within the type of quotations then are often drawn conclusions. Results: The results showed that the 3D Conformal Radiotherapy of squamous cell carcinoma case on orbital region with the addition of a bolus in Dr. Sardjito Yogyakarta Hospital consists of a CT Simulator examination, TPS (Treatment Planning System), Verification and Treatment (radiation therapy). The bolus in the treatment process is intended for this case to provide a 95% dose to the target tumor raised up to the surface. For the response shown in this case the patient was not good despite the reduction in tumor, the tumor response was not good (response
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procedure of 3d conformal Radiotherapy on squamous cell carcinoma case in orbital region in Radiotherapy Unit of dr sardjito yogyakarta hospital
Jurnal Imejing Diagnostik (JImeD), 2018Co-Authors: Nova Aditya Surya Irawan, Gatot Murti Wibowo, Khumaidi KhumaidiAbstract:Background: This study aims to determine the procedures, techniques, reasons and evaluation of 3D conformal Radiotherapy of squamous cell carcinoma case in the orbital region with additional bolus that has been done in the Radiotherapy Unit of Dr. Sardjito Yogyakarta Hospital. In addition, from this research also to find out how the visually tumor response to the radiation that has been given and there are limits of research for tumor responses made observations from the beginning of radiation to the completion of radiation. Methods: This type of research is qualitative with a case study approach. The data was collected in November-December 2017 at Radiotherapy Unit of Dr. Sardjito Yogyakarta Hospital by observation methodology, interview with Radiation Oncologist Specialist, Medical Physicist and Radiographer. the data obtained from the study were analyzed by an interactive model, creating the interview transcripts subsequently reduced and processed within the type of open coding, given within the type of quotations then are often drawn conclusions. Results: The results showed that the 3D Conformal Radiotherapy of squamous cell carcinoma case on orbital region with the addition of a bolus in Dr. Sardjito Yogyakarta Hospital consists of a CT Simulator examination, TPS (Treatment Planning System), Verification and Treatment (radiation therapy). The bolus in the treatment process is intended for this case to provide a 95% dose to the target tumor raised up to the surface. For the response shown in this case the patient was not good despite the reduction in tumor, the tumor response was not good (response <50%) according to WHO criteria showed stable disease criteria (SD). Conclusion: 3D conformal Radiotherapy of squamous cell carcinoma case in the orbital region of this patient with the addition of a bolus aims to obtain a homogeneous distribution of all tumor targets and for visual tumor response in this case according to WHO criteria showing stable disease (SD) criteria.
