The Experts below are selected from a list of 14988 Experts worldwide ranked by ideXlab platform
John B Fiveash - One of the best experts on this subject based on the ideXlab platform.
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plan quality and treatment Planning Technique for single isocenter cranial radiosurgery with volumetric modulated arc therapy
Practical radiation oncology, 2012Co-Authors: Grant M Clark, R Popple, Brendan M Prendergast, S A Spencer, Evan M Thomas, John G Stewart, Barton L Guthrie, James M Markert, John B FiveashAbstract:Abstract Purpose To demonstrate plan quality and provide a practical, systematic approach to the treatment Planning Technique for single isocenter cranial radiosurgery with volumetric modulated arc therapy (VMAT; RapidArc, Varian Medical systems, Palo Alto, CA). Methods and materials Fifteen patients with 1 or more brain metastases underwent single isocenter VMAT radiosurgery. All plans were normalized to deliver 100% of the prescription dose to 99%-100% of the target volume. All targets per plan were treated to the same dose. Plans were created with dose control tuning structures surrounding targets to maximize conformity and dose gradient. Plan quality was evaluated by calculation of conformity index (CI = 100% isodose volume/target volume) and homogeneity index (HI = maximum dose/prescription dose) scores for each target and a Paddick gradient index (GI = 50% isodose volume/100% isodose volume) score for each plan. Results The median number of targets per patient was 2 (range, 1-5). The median number of non-coplanar arcs utilized per plan was 2 (range, 1- 4). Single target plans were created with 1 or 2 non-coplanar arcs while multitarget plans utilized 2 to 4 non-coplanar arcs. Prescription doses ranged from 5-16 Gy in 1-5 fractions. The mean conformity index was 1.12 (± SD, 0.13) and the mean HI was 1.44 (± SD, 0.11) for all targets. The mean GI per plan was 3.34 (± SD, 0.42). Conclusions We have outlined a practical approach to cranial radiosurgery treatment Planning using the single isocenter VMAT platform. One or 2 arc single isocenter plans are often adequate for treatment of single targets, while 2-4 arcs may be more advantageous for multiple targets. Given the high plan quality and extreme clinical efficiency, this single isocenter VMAT approach will continue to become more prevalent for linac-based radiosurgical treatment of 1 or more intracranial targets and will likely replace multiple isocenter Techniques.
Mohammad Keshmiri - One of the best experts on this subject based on the ideXlab platform.
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Image-Based Visual Servoing Using an Optimized Trajectory Planning Technique
IEEE ASME Transactions on Mechatronics, 2017Co-Authors: Mohammad KeshmiriAbstract:Trajectory Planning is a useful Technique in robotics for guiding the robot through complicated tasks. In this paper, a new semi-offline trajectory Planning method is developed to perform image-based visual servoing (IBVS) tasks for a 6 DOFs robotic manipulator system. This method extends the operation range of the system compared with the traditional IBVS controllers. In this method, the camera's velocity screw is parametrized using time-based profiles. The parameters of the velocity profile are then determined by minimizing the cost function consisting of the error between the initial and desired features while respecting the system constraints. A depth-estimation algorithm is proposed to provide the trajectory Planning algorithm with a good estimation of the initial depth. The algorithm for Planning the orientation of the robot is decoupled from the position Planning of the robot. This method eliminates the limitation caused by camera's field of view. The algorithm is validated via the experiment on a 6 DOFs Denso robot in an eye-in-hand configuration. The experimental results demonstrate that the proposed method can overcome some major IBVS drawbacks such as surpassing the system limits and causing instability of the system in fulfilling the tasks which require a 180° rotation of the camera about its center.
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Visual servoing of a robotic manipulator using an optimized trajectory Planning Technique
2014 IEEE 27th Canadian Conference on Electrical and Computer Engineering (CCECE), 2014Co-Authors: Mohammad KeshmiriAbstract:In this paper, a novel image based visual servoing (IBVS) using an optimized trajectory Planning Technique is proposed. In this method the camera's velocity screw is parameterized using polynomial profiles. The parameters of the velocity profile are then determined to guide the robot to its desired position, by minimizing the error in an optimization algorithm. In addition, this Technique keeps the robot in its physical limits and keeps the features in the field of view (FOV). This algorithm is tested on a 4 DOFs Denso robot in an eye-in-hand configuration. Simulation results demonstrate t hat the proposed method solves some of the IBVS problems such as reaching the robot's or cameras' limits and instability of the system for pure 180o rotation about its center.
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CCECE - Visual servoing of a robotic manipulator using an optimized trajectory Planning Technique
2014 IEEE 27th Canadian Conference on Electrical and Computer Engineering (CCECE), 2014Co-Authors: Mohammad KeshmiriAbstract:In this paper, a novel image based visual servoing (IBVS) using an optimized trajectory Planning Technique is proposed. In this method the camera's velocity screw is parameterized using polynomial profiles. The parameters of the velocity profile are then determined to guide the robot to its desired position, by minimizing the error in an optimization algorithm. In addition, this Technique keeps the robot in its physical limits and keeps the features in the field of view (FOV). This algorithm is tested on a 4 DOFs Denso robot in an eye-in-hand configuration. Simulation results demonstrate t hat the proposed method solves some of the IBVS problems such as reaching the robot's or cameras' limits and instability of the system for pure 180o rotation about its center.
Jacob G Scott - One of the best experts on this subject based on the ideXlab platform.
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temporally feathered intensity modulated radiation therapy a Planning Technique to reduce normal tissue toxicity
Medical Physics, 2018Co-Authors: Juan Carlos Lopez Alfonso, Shireen Parsai, N P Joshi, Andrew Godley, Chirag Shah, Shlomo A Koyfman, Jimmy J Caudell, Clifton D Fuller, Heiko Enderling, Jacob G ScottAbstract:PURPOSE: Intensity-modulated radiation therapy (IMRT) has allowed optimization of three-dimensional spatial radiation dose distributions permitting target coverage while reducing normal tissue toxicity. However, radiation-induced normal tissue toxicity is a major contributor to patients' quality of life and often a dose-limiting factor in the definitive treatment of cancer with radiation therapy. We propose the next logical step in the evolution of IMRT using canonical radiobiological principles, optimizing the temporal dimension through which radiation therapy is delivered to further reduce radiation-induced toxicity by increased time for normal tissue recovery. We term this novel treatment Planning strategy "temporally feathered radiation therapy" (TFRT). METHODS: Temporally feathered radiotherapy plans were generated as a composite of five simulated treatment plans each with altered constraints on particular hypothetical organs at risk (OARs) to be delivered sequentially. For each of these TFRT plans, OARs chosen for feathering receive higher doses while the remaining OARs receive lower doses than the standard fractional dose delivered in a conventional fractionated IMRT plan. Each TFRT plan is delivered a specific weekday, which in effect leads to a higher dose once weekly followed by four lower fractional doses to each temporally feathered OAR. We compared normal tissue toxicity between TFRT and conventional fractionated IMRT plans by using a dynamical mathematical model to describe radiation-induced tissue damage and repair over time. RESULTS: Model-based simulations of TFRT demonstrated potential for reduced normal tissue toxicity compared to conventionally planned IMRT. The sequencing of high and low fractional doses delivered to OARs by TFRT plans suggested increased normal tissue recovery, and hence less overall radiation-induced toxicity, despite higher total doses delivered to OARs compared to conventional fractionated IMRT plans. The magnitude of toxicity reduction by TFRT Planning was found to depend on the corresponding standard fractional dose of IMRT and organ-specific recovery rate of sublethal radiation-induced damage. CONCLUSIONS: TFRT is a novel Technique for treatment Planning and optimization of therapeutic radiotherapy that considers the nonlinear aspects of normal tissue repair to optimize toxicity profiles. Model-based simulations of TFRT to carefully conceptualized clinical cases have demonstrated potential for radiation-induced toxicity reduction in a previously described dynamical model of normal tissue complication probability (NTCP).
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temporally feathered intensity modulated radiation therapy a Planning Technique to reduce normal tissue toxicity
bioRxiv, 2018Co-Authors: Juan Carlos Lopez Alfonso, Shireen Parsai, N P Joshi, Andrew Godley, Chirag Shah, Shlomo A Koyfman, Jimmy J Caudell, Clifton D Fuller, Heiko Enderling, Jacob G ScottAbstract:Purpose/Objective: We introduce a novel strategy of radiation therapy Planning using canonical radiobiology principles and leveraging time to further decrease normal tissue complication probability (NTCP). Temporally feathered radiation therapy (TFRT) is presented as a strategy to reduce radiation-induced toxicity, and is compared with conventionally fractionated radiotherapy an in silico model of normal tissue radiation response. Material/Methods: As a first choice to compare conventional and temporally feathered plans, we consider the biologically equivalent dose (BED), which is the most common model used to compare different fractionation schemes in radiotherapy. We formulated a mathematical model to simulate normal tissue radiation-induced damage and recovery induced by different fractionation regimens. This model considers tissue recovery as a dynamic process rather than a static probability. Radiation response is determined by the Linear-Quadratic (LQ) model, which is widely used in radiobiology. Results: TFRT is shown to be beneficial in reducing radiation-induced toxicity to normal tissues compared to conventional treatment schedules. BED is not suitable to evaluate the success potential of TFRT because of its static nature in time, the proposed dynamical NTCP model however, demonstrates that there exists a window of opportunity for temporally feathering organs at risk whereby toxicity can be reduced without affecting tumor dosing. The high and low fractional doses delivered by temporally feathered plans to organs at risk allow increased damage recovery despite higher total doses compared to standard plans. The clinical benefit of temporally feathered plans not only depends on the combination of fractional doses considered, but also on the organ-specific recovery rate of radiation damage. In particular, we found that when comparing temporally feathered and standard plans, for each recovery rate a certain range of standard fractional doses exists in which TFRT reduces toxicity. Although the potential benefit of TFRT over conventionally fractionated radiotherapy is always higher in those ranges, there exists an optimal standard fractional dose in which toxicity induced by the temporally feathered plan is minimum. Conclusions: Our novel TFRT methodology opens a yet unexplored avenue for Planning optimization in radiotherapy. Application of this Technique to carefully selected cases will not only potentially allow reduction in normal tissue toxicity, but also allow dose escalation to the tumor thereby enhancing the therapeutic ratio.
Grant M Clark - One of the best experts on this subject based on the ideXlab platform.
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plan quality and treatment Planning Technique for single isocenter cranial radiosurgery with volumetric modulated arc therapy
Practical radiation oncology, 2012Co-Authors: Grant M Clark, R Popple, Brendan M Prendergast, S A Spencer, Evan M Thomas, John G Stewart, Barton L Guthrie, James M Markert, John B FiveashAbstract:Abstract Purpose To demonstrate plan quality and provide a practical, systematic approach to the treatment Planning Technique for single isocenter cranial radiosurgery with volumetric modulated arc therapy (VMAT; RapidArc, Varian Medical systems, Palo Alto, CA). Methods and materials Fifteen patients with 1 or more brain metastases underwent single isocenter VMAT radiosurgery. All plans were normalized to deliver 100% of the prescription dose to 99%-100% of the target volume. All targets per plan were treated to the same dose. Plans were created with dose control tuning structures surrounding targets to maximize conformity and dose gradient. Plan quality was evaluated by calculation of conformity index (CI = 100% isodose volume/target volume) and homogeneity index (HI = maximum dose/prescription dose) scores for each target and a Paddick gradient index (GI = 50% isodose volume/100% isodose volume) score for each plan. Results The median number of targets per patient was 2 (range, 1-5). The median number of non-coplanar arcs utilized per plan was 2 (range, 1- 4). Single target plans were created with 1 or 2 non-coplanar arcs while multitarget plans utilized 2 to 4 non-coplanar arcs. Prescription doses ranged from 5-16 Gy in 1-5 fractions. The mean conformity index was 1.12 (± SD, 0.13) and the mean HI was 1.44 (± SD, 0.11) for all targets. The mean GI per plan was 3.34 (± SD, 0.42). Conclusions We have outlined a practical approach to cranial radiosurgery treatment Planning using the single isocenter VMAT platform. One or 2 arc single isocenter plans are often adequate for treatment of single targets, while 2-4 arcs may be more advantageous for multiple targets. Given the high plan quality and extreme clinical efficiency, this single isocenter VMAT approach will continue to become more prevalent for linac-based radiosurgical treatment of 1 or more intracranial targets and will likely replace multiple isocenter Techniques.
Wolfgang A Tome - One of the best experts on this subject based on the ideXlab platform.
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on a single isocenter volumetric modulated arc therapy srs Planning Technique for multiple brain metastases
Journal of radiosurgery and SBRT, 2012Co-Authors: Wolfgang A Tome, Nicholas HardcastleAbstract:Volumetric modulated arc therapy (VMAT) is a new Technique for efficient delivery of intensity modulated dose distributions. This study investigates a single isocenter VMAT Technique to treat multiple brain metastases to 15 - 24 Gy. The Pinnacle3 SmartArc VMAT optimization plugin was used for all VMAT plans. A non-coplanar arc Technique using five 100° arcs and one isocenter was compared with a conformal arc Technique which used anywhere from 5 to 9 arcs with at least one isocenter per target. Comparison was done using the Conformality Number (CN), Prescription Isodose to Target Volume (PITV), Homogeneity Index (HI), Conformity-Gradient Index (CGI) as well as the 12 Gy isodose volume in the normal brain from which the risk of symptomatic necrosis (S-NEC) was calculated. The VMAT Technique resulted in plans with a maximum delivery of 15 minutes, regardless of the number of targets. The VMAT Technique provided superior conformity for large targets but for small targets the conformal arc Technique resulted in superior conformity. For all targets, the conformal arc Technique resulted in superior dose fall off outside of the target. The VMAT Technique resulted in an increase in the 12 Gy volume over the conformal arc Technique, with an accompanying increase in risk of S-NEC. While the 12 Gy volume was still within an acceptable clinical range, 4 out 20 patients showed a significant increase (15-20%) in absolute risk of S-NEC. Thus the VMAT Technique resulted in clinically acceptable plans with vast reductions in treatment time.
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a Technique for stereotactic radiosurgery treatment Planning with helical tomotherapy
Medical Dosimetry, 2011Co-Authors: E Soisson, P W Hoban, Thomas Kammeyer, Jeffrey M Kapatoes, D Westerly, Amar Basavatia, Wolfgang A TomeAbstract:The purpose of this study was to develop an efficient and effective Planning Technique for stereotactic radiosurgery using helical tomotherapy. Planning CTs and contours of 20 patients, previously treated in our clinic for brain metastases with linac-based radiosurgery using circular collimators, were used to develop a robust TomoTherapy Planning Technique. Plan calculation times as well as delivery times were recorded for all patients to allow for an efficiency evaluation. In addition, conformation and homogeneity indices were calculated as metrics to compare plan quality with that which is achieved with conventional radiosurgery delivery systems. A robust and efficient Planning Technique was identified to produce plans of radiosurgical quality using the TomoTherapy treatment Planning system. Dose calculation did not exceed a few hours and resulting delivery times were less than 1 hour, which allows the process to fit into a single day radiosurgery workflow. Plan conformity compared favorably with published results for gamma knife radiosurgery. In addition, plan homogeneity was similar to linac-based approaches. The TomoTherapy Planning software can be used to create plans of acceptable quality for stereotactic radiosurgery in a time that is appropriate for a radiosurgery workflow that requires that Planning and delivery occur within 1 treatment day.