The Experts below are selected from a list of 1113 Experts worldwide ranked by ideXlab platform
R L Maughan - One of the best experts on this subject based on the ideXlab platform.
-
solid state microdosimetry in hadron Therapy
Radiation Protection Dosimetry, 2002Co-Authors: A B Rosenfled, P. D. Bradley, R L Maughan, Marco Zaider, Iwan Cornelius, Barry Allen, J C Yanch, J Flanz, T KobayashiAbstract:A report of recent developments in silicon microdosimetry is presented. SOI based microdosemeters have shown promise as a viable alternative to traditional tissue-equivalent proportional counters. The application of these silicon microdosemeters to such radiation Therapy modalities as boron Neutron capture Therapy (BNCT), boron Neutron capture synovectomy (BNCS), proton Therapy (PT), and Fast Neutron Therapy (FNT) has been performed. Several shortcomings of the current silicon microdose-meter were identified and will be taken into account in the design of a second-generation device.
-
characterization of miniature tissue equivalent proportional counters for Neutron radioTherapy applications
Physics in Medicine and Biology, 2002Co-Authors: J Burmeister, Chandrasekhar Kota, R L Maughan, A J WakerAbstract:A miniature tissue-equivalent proportional counter (TEPC) system has been developed to facilitate microdosimetric measurements in high-flux mixed fields. Counters with collecting volumes of 12.3 and 2.65 mm3 have been constructed using various tissue-equivalent wall materials, including those loaded with 10B for evaluation of the effects of the boron Neutron capture reaction. These counters provide a measure of both the absorbed dose and associated radiation quality, allowing an assessment of the utility and relative effectiveness of various Neutron radioTherapy techniques such as boron Neutron capture Therapy (BNCT), boron Neutron capture enhanced Fast Neutron Therapy (BNCEFNT) and intensity modulated Neutron radioTherapy (IMNRT). An evaluation of the physical parameters affecting the measured microdosimetric spectrum, the gas multiplication characteristics and the measurement of absorbed dose is presented. In addition, important aspects of the calibration and low energy extrapolation techniques for the microdosimetric spectrum are provided.
-
miniature tissue equivalent proportional counters for bnct and bncefnt dosimetry
Medical Physics, 2001Co-Authors: J Burmeister, Chandrasekhar Kota, R L Maughan, A J WakerAbstract:A dual miniature tissue-equivalent proportional counter (TEPC) system has been developed to facilitate microdosimetry for BoronNeutron Capture Therapy (BNCT). This system has been designed specifically to allow the analysis of the single event charged particle spectrum in phantom in high intensity BNCT beams and to provide this microdosimetric information with excellent spatial resolution. Paired A-150 and 10 B -loaded A-150 TEPCs with 12.3 mm3 collecting volumes have been constructed. These TEPCs allow more accurate Neutrondosimetry than current techniques, offer a direct measure of the boronNeutron capture dose, and provide a framework for predicting the biological effectiveness of the absorbed dose. Design aspects and characterization of these detectors are reviewed, along with an exposition of the advantages of microdosimetry using these detectors over conventional dosimetry methods. In addition, the utility of this technique for boronNeutron capture enhancement of Fast Neutron Therapy (BNCEFNT) is discussed.
-
use of low pressure tissue equivalent proportional counters for the dosimetry of Neutron beams used in bnct and bncefnt
Medical Physics, 2000Co-Authors: Chandrasekhar Kota, R L Maughan, David Tattam, Derek T BeynonAbstract:The absorbed dose in a phantom or patient in boronNeutron capture Therapy (BNCT) and boronNeutron capture enhanced Fast Neutron Therapy (BNCEFNT) is deposited by gamma rays,Neutrons of a range of energies and the 10 B reaction products. These dose components are commonly measured with paired (TE/Mg) ion chambers and foil activation technique. In the present work, we have investigated the use of paired tissue equivalent (TE) and TE+ 10 B proportional counters as an alternate and complementary dosimetry technique for use in these Neutron beams. We first describe various aspects of counter operation, uncertainties in dose measurement, and interpretation of the data. We then present measurements made in the following radiation fields: An epithermal beam at the University of Birmingham in the United Kingdom, a d(48.5)+ Be Fast Neutron Therapy beam at Harper Hospital in Detroit, and a 252 Cf radiation field. In the epithermal beam, our measured gamma and Neutrondose rates compare very well with the values calculated using Monte Carlo methods. The measured 10 B dose rates show a systematic difference of ∼35% when compared to the calculations. The measured Neutron+gamma dose rates in the Fast Neutron beam are in good agreement with those measured using a calibrated A-150 TEP (tissue equivalent plastic) ion chamber. The measured 10 B dose rates compare very well with those measured using other methods. In the 252 Cf radiation field, the measured dose rates for all three components agree well with other Monte Carlo calculations and measurements. Based on these results, we conclude that the paired low-pressure proportional counters can be used to establish an independent technique of dose measurement in these radiation fields.
-
microdosimetric specification of the radiation quality of a d 48 5 be Fast Neutron Therapy beam produced by a superconducting cyclotron
Medical Physics, 1996Co-Authors: Chandrasekhar Kota, R L MaughanAbstract:The proportional countermicrodosimetric technique has been employed to quantify variations in the quality of a d(48.5)+Be Fast Neutron beam passing through a homogeneous water phantom. Single event spectra have been measured as a function of spatial location in the water phantom and field size. The measured spectra have been separated into component spectra corresponding to the gamma, recoil proton and alpha plus heavy recoil ion contribution to the total absorbed dose. The total absorbed dose normalized to the ‘‘monitor units’’ used in daily clinical use has been calculated from the measured spectra and compared to the data measured with calibrated ion chambers. The present measurements agree with the ion chamber data to within 5%. The RBE of the Neutron beam is assumed to be proportional to the microdosimetric parameter y* for the dose ranges pertinent to fractionated Neutron Therapy. The relative variations in y* , assumed to be representative of variations in the RBE are mapped as a function of field size and spatial location in the phantom. A variation in the RBE of about 4% for points within and 8% for points outside a 10 cm×10 cm field is observed. The variations in the RBE within the beam are caused by an increase in the gamma component with depth. An increase in the RBE of about 4% is observed with increasing field size which is attributed to a change in the Neutron spectrum. Compared to the uncertainties in the prescribed dose, associated with uncertainties in the clinically used RBE, variation in the RBE between various tissues, and other dosimetric uncertainities caused by factors such as patient inhomogeneities, patient setup errors, patient motion, etc., the measured spatial RBE variations are not considered significant enough to be incorporated into the treatment planning scheme.
Chandrasekhar Kota - One of the best experts on this subject based on the ideXlab platform.
-
characterization of miniature tissue equivalent proportional counters for Neutron radioTherapy applications
Physics in Medicine and Biology, 2002Co-Authors: J Burmeister, Chandrasekhar Kota, R L Maughan, A J WakerAbstract:A miniature tissue-equivalent proportional counter (TEPC) system has been developed to facilitate microdosimetric measurements in high-flux mixed fields. Counters with collecting volumes of 12.3 and 2.65 mm3 have been constructed using various tissue-equivalent wall materials, including those loaded with 10B for evaluation of the effects of the boron Neutron capture reaction. These counters provide a measure of both the absorbed dose and associated radiation quality, allowing an assessment of the utility and relative effectiveness of various Neutron radioTherapy techniques such as boron Neutron capture Therapy (BNCT), boron Neutron capture enhanced Fast Neutron Therapy (BNCEFNT) and intensity modulated Neutron radioTherapy (IMNRT). An evaluation of the physical parameters affecting the measured microdosimetric spectrum, the gas multiplication characteristics and the measurement of absorbed dose is presented. In addition, important aspects of the calibration and low energy extrapolation techniques for the microdosimetric spectrum are provided.
-
miniature tissue equivalent proportional counters for bnct and bncefnt dosimetry
Medical Physics, 2001Co-Authors: J Burmeister, Chandrasekhar Kota, R L Maughan, A J WakerAbstract:A dual miniature tissue-equivalent proportional counter (TEPC) system has been developed to facilitate microdosimetry for BoronNeutron Capture Therapy (BNCT). This system has been designed specifically to allow the analysis of the single event charged particle spectrum in phantom in high intensity BNCT beams and to provide this microdosimetric information with excellent spatial resolution. Paired A-150 and 10 B -loaded A-150 TEPCs with 12.3 mm3 collecting volumes have been constructed. These TEPCs allow more accurate Neutrondosimetry than current techniques, offer a direct measure of the boronNeutron capture dose, and provide a framework for predicting the biological effectiveness of the absorbed dose. Design aspects and characterization of these detectors are reviewed, along with an exposition of the advantages of microdosimetry using these detectors over conventional dosimetry methods. In addition, the utility of this technique for boronNeutron capture enhancement of Fast Neutron Therapy (BNCEFNT) is discussed.
-
use of low pressure tissue equivalent proportional counters for the dosimetry of Neutron beams used in bnct and bncefnt
Medical Physics, 2000Co-Authors: Chandrasekhar Kota, R L Maughan, David Tattam, Derek T BeynonAbstract:The absorbed dose in a phantom or patient in boronNeutron capture Therapy (BNCT) and boronNeutron capture enhanced Fast Neutron Therapy (BNCEFNT) is deposited by gamma rays,Neutrons of a range of energies and the 10 B reaction products. These dose components are commonly measured with paired (TE/Mg) ion chambers and foil activation technique. In the present work, we have investigated the use of paired tissue equivalent (TE) and TE+ 10 B proportional counters as an alternate and complementary dosimetry technique for use in these Neutron beams. We first describe various aspects of counter operation, uncertainties in dose measurement, and interpretation of the data. We then present measurements made in the following radiation fields: An epithermal beam at the University of Birmingham in the United Kingdom, a d(48.5)+ Be Fast Neutron Therapy beam at Harper Hospital in Detroit, and a 252 Cf radiation field. In the epithermal beam, our measured gamma and Neutrondose rates compare very well with the values calculated using Monte Carlo methods. The measured 10 B dose rates show a systematic difference of ∼35% when compared to the calculations. The measured Neutron+gamma dose rates in the Fast Neutron beam are in good agreement with those measured using a calibrated A-150 TEP (tissue equivalent plastic) ion chamber. The measured 10 B dose rates compare very well with those measured using other methods. In the 252 Cf radiation field, the measured dose rates for all three components agree well with other Monte Carlo calculations and measurements. Based on these results, we conclude that the paired low-pressure proportional counters can be used to establish an independent technique of dose measurement in these radiation fields.
-
microdosimetric specification of the radiation quality of a d 48 5 be Fast Neutron Therapy beam produced by a superconducting cyclotron
Medical Physics, 1996Co-Authors: Chandrasekhar Kota, R L MaughanAbstract:The proportional countermicrodosimetric technique has been employed to quantify variations in the quality of a d(48.5)+Be Fast Neutron beam passing through a homogeneous water phantom. Single event spectra have been measured as a function of spatial location in the water phantom and field size. The measured spectra have been separated into component spectra corresponding to the gamma, recoil proton and alpha plus heavy recoil ion contribution to the total absorbed dose. The total absorbed dose normalized to the ‘‘monitor units’’ used in daily clinical use has been calculated from the measured spectra and compared to the data measured with calibrated ion chambers. The present measurements agree with the ion chamber data to within 5%. The RBE of the Neutron beam is assumed to be proportional to the microdosimetric parameter y* for the dose ranges pertinent to fractionated Neutron Therapy. The relative variations in y* , assumed to be representative of variations in the RBE are mapped as a function of field size and spatial location in the phantom. A variation in the RBE of about 4% for points within and 8% for points outside a 10 cm×10 cm field is observed. The variations in the RBE within the beam are caused by an increase in the gamma component with depth. An increase in the RBE of about 4% is observed with increasing field size which is attributed to a change in the Neutron spectrum. Compared to the uncertainties in the prescribed dose, associated with uncertainties in the clinically used RBE, variation in the RBE between various tissues, and other dosimetric uncertainities caused by factors such as patient inhomogeneities, patient setup errors, patient motion, etc., the measured spatial RBE variations are not considered significant enough to be incorporated into the treatment planning scheme.
A J Waker - One of the best experts on this subject based on the ideXlab platform.
-
characterization of miniature tissue equivalent proportional counters for Neutron radioTherapy applications
Physics in Medicine and Biology, 2002Co-Authors: J Burmeister, Chandrasekhar Kota, R L Maughan, A J WakerAbstract:A miniature tissue-equivalent proportional counter (TEPC) system has been developed to facilitate microdosimetric measurements in high-flux mixed fields. Counters with collecting volumes of 12.3 and 2.65 mm3 have been constructed using various tissue-equivalent wall materials, including those loaded with 10B for evaluation of the effects of the boron Neutron capture reaction. These counters provide a measure of both the absorbed dose and associated radiation quality, allowing an assessment of the utility and relative effectiveness of various Neutron radioTherapy techniques such as boron Neutron capture Therapy (BNCT), boron Neutron capture enhanced Fast Neutron Therapy (BNCEFNT) and intensity modulated Neutron radioTherapy (IMNRT). An evaluation of the physical parameters affecting the measured microdosimetric spectrum, the gas multiplication characteristics and the measurement of absorbed dose is presented. In addition, important aspects of the calibration and low energy extrapolation techniques for the microdosimetric spectrum are provided.
-
miniature tissue equivalent proportional counters for bnct and bncefnt dosimetry
Medical Physics, 2001Co-Authors: J Burmeister, Chandrasekhar Kota, R L Maughan, A J WakerAbstract:A dual miniature tissue-equivalent proportional counter (TEPC) system has been developed to facilitate microdosimetry for BoronNeutron Capture Therapy (BNCT). This system has been designed specifically to allow the analysis of the single event charged particle spectrum in phantom in high intensity BNCT beams and to provide this microdosimetric information with excellent spatial resolution. Paired A-150 and 10 B -loaded A-150 TEPCs with 12.3 mm3 collecting volumes have been constructed. These TEPCs allow more accurate Neutrondosimetry than current techniques, offer a direct measure of the boronNeutron capture dose, and provide a framework for predicting the biological effectiveness of the absorbed dose. Design aspects and characterization of these detectors are reviewed, along with an exposition of the advantages of microdosimetry using these detectors over conventional dosimetry methods. In addition, the utility of this technique for boronNeutron capture enhancement of Fast Neutron Therapy (BNCEFNT) is discussed.
J Burmeister - One of the best experts on this subject based on the ideXlab platform.
-
three discipline collaborative radiation Therapy 3dcrt special debate the united states needs at least one carbon ion facility
Journal of Applied Clinical Medical Physics, 2019Co-Authors: Eleanor A Blakely, B Faddegon, Christopher L Tinkle, C Bloch, M M Dominello, Robert J Griffin, M C Joiner, J BurmeisterAbstract:High linear energy transfer (LET) radioTherapy has long held the promise of improved efficacy against tumors that are refractory to conventional radioTherapy. While such an increase in efficacy is achievable with Fast Neutron Therapy, poor physical dose distribution characteristics have limited its potential. Carbon ions are an elegant solution in that they combine the biological effectiveness of Fast Neutron Therapy with physical dose shaping characteristics even better than proton Therapy. However, the cost of technology to deliver this treatment is tremendous and its clinical potential remains largely unproven. Clinical trials are underway in several countries, helping us gather the necessary data to demonstrate its efficacy. However, the United States, a traditional world leader in the development and implementation of advanced healthcare technology, is not among them. Considering the substantial potential benefit of this treatment and also our current efforts to contain the costs of healthcare, is now the time for the United States to step from the sidelines to participate in this research? This is the subject of this month’s 3DCRT debate. Arguing for the proposition will be Drs. Eleanor Blakely, Bruce Faddegon, and Christopher Tinkle. Dr. Blakely is a senior staff in biophysicist (rehired retiree since 2015) at the Lawrence Berkeley National Laboratory (LBNL) with more than 44 yr of professional experience in molecular, cellular, and animal radiobiological research directed at studying the basic mechanisms of radiation responses, with an emphasis on charged particle radiation effects. Dr. Faddegon is a professor of medical physics in the radioTherapy department of UCSF. His research focus is to bring technical innovation into the clinic to improve radioTherapy by advancing linear accelerator, imaging, and particle Therapy equipment and methods including Monte Carlo simulation tools and techniques. Dr. Tinkle is a radiation oncologist and Assistant Member in the department of radiation oncology at St. Jude Children’s Research Hospital. His focus is on preclinical and translational studies in pediatric cancers exploring the interactions of proton and photon radioTherapy and emerging targeted systemic Therapy. Arguing against the proposition will be Drs. Charles Bloch, Michael Dominello, and Robert Griffin. Dr. Bloch is a medical physicist who started his career in proton Therapy over 25 yr ago. Currently, he is an associate professor in the department of radiation oncology at the University of Washington and serves as an associate director of education, research, and development at the Seattle Proton Therapy Center. Dr. Dominello is an assistant professor in oncology department and practicing radiation oncologist at Wayne State University, Karmanos Cancer Center. His interests include stereotactic radiosurgery for brain and spine and therapeutic ratio. He currently serves as the Karmanos/McLaren‐wide PI for NRG, Karmanos Cancer Network Medical Director for Quality and participates as a member of numerous committees through NRG and ASTRO. Dr. Dominello serves as the Assistant Program Director for the Radiation Oncology Residency Program and as an instructor in courses for both graduate and undergraduate students at the university. Dr. Griffin is a professor of radiation biology at the University of Arkansas for Medical Sciences. His group studies living tissue response to high‐dose radioTherapy (SBRT) and spatially fractionated radiation approaches with targeted drug delivery to tumors. He served as a president of the Society for Thermal Medicine, is a Vice Chair of the Science Education and Professional Development Committee and Annual Meeting biology track chair for ASTRO and is an associate senior editor for Technology in Cancer Research and Treatment and the International Journal of Radiation Oncology, Biology and Physics.
-
characterization of miniature tissue equivalent proportional counters for Neutron radioTherapy applications
Physics in Medicine and Biology, 2002Co-Authors: J Burmeister, Chandrasekhar Kota, R L Maughan, A J WakerAbstract:A miniature tissue-equivalent proportional counter (TEPC) system has been developed to facilitate microdosimetric measurements in high-flux mixed fields. Counters with collecting volumes of 12.3 and 2.65 mm3 have been constructed using various tissue-equivalent wall materials, including those loaded with 10B for evaluation of the effects of the boron Neutron capture reaction. These counters provide a measure of both the absorbed dose and associated radiation quality, allowing an assessment of the utility and relative effectiveness of various Neutron radioTherapy techniques such as boron Neutron capture Therapy (BNCT), boron Neutron capture enhanced Fast Neutron Therapy (BNCEFNT) and intensity modulated Neutron radioTherapy (IMNRT). An evaluation of the physical parameters affecting the measured microdosimetric spectrum, the gas multiplication characteristics and the measurement of absorbed dose is presented. In addition, important aspects of the calibration and low energy extrapolation techniques for the microdosimetric spectrum are provided.
-
miniature tissue equivalent proportional counters for bnct and bncefnt dosimetry
Medical Physics, 2001Co-Authors: J Burmeister, Chandrasekhar Kota, R L Maughan, A J WakerAbstract:A dual miniature tissue-equivalent proportional counter (TEPC) system has been developed to facilitate microdosimetry for BoronNeutron Capture Therapy (BNCT). This system has been designed specifically to allow the analysis of the single event charged particle spectrum in phantom in high intensity BNCT beams and to provide this microdosimetric information with excellent spatial resolution. Paired A-150 and 10 B -loaded A-150 TEPCs with 12.3 mm3 collecting volumes have been constructed. These TEPCs allow more accurate Neutrondosimetry than current techniques, offer a direct measure of the boronNeutron capture dose, and provide a framework for predicting the biological effectiveness of the absorbed dose. Design aspects and characterization of these detectors are reviewed, along with an exposition of the advantages of microdosimetry using these detectors over conventional dosimetry methods. In addition, the utility of this technique for boronNeutron capture enhancement of Fast Neutron Therapy (BNCEFNT) is discussed.
P Pihet - One of the best experts on this subject based on the ideXlab platform.
-
specification of radiation quality in Fast Neutron Therapy microdosimetric and radiobiological approach
Recent results in cancer research, 1998Co-Authors: John Gueulette, H G Menzel, P Pihet, Andre WambersieAbstract:Specification of radiation quality is an important issue in Fast Neutron Therapy since the biological effectiveness of the beams varies to a large extent with Neutron energy. It must meet specific criteria, mainly derived from the accuracy requirement for absorbed dose delivery. A first approach to this problem consists in identifying physical parameters that can be related to Relative Biological Effectiveness (RBE) and which describe the beam production technique (e.g. Neutron-producing reaction, p + Be or d + Be, energy of the incident particle). A second is based on microdosimetry, which provides a description of the secondary radiation components to which the biological consequences of irradiations are more directly correlated. A third approach consists in experimental RBE determinations in reference conditions: intestinal crypt regeneration in mice after irradiation to the whole body with single doses is proposed as a standard biological system for radiobiological calibrations of clinical Fast Neutron beams. Dosimetric, microdosimetric and radiobiological intercomparisons are encouraged since they provide a homogeneous set of data which facilitate the exchange of clinical information. They also constitute a basis for the clinical RBE approach and an overall check of the irradiation procedure. Therefore they should be recommended in every non-conventional radiation Therapy facility.
-
radiobiological effectiveness of radiation beams with broad let spectra microdosimetric analysis using biological weighting functions
Radiation Protection Dosimetry, 1994Co-Authors: T Loncol, John Gueulette, P Pihet, V Cosgrove, J M Denis, A Mazal, H G Menzel, R SabattierAbstract:The evaluation of averaged parameters from microdosimetric spectra, measured with proportional counters and biological weighting functions of the quantity lineal energy, provides a practical solution to the specification of radiation quality, especially for radiations with broad LET spectra, such as those used for radiation Therapy. This approach has already proved satisfactory for Fast Neutron Therapy beams of different energy using a biological weighting function numerically determined on empirical and statistical bases using the results of a RBE-microdosimetry intercomparison study. The paper discusses the applicability of this procedure by extending the range of radiations to Fast protons. For this purpose, the earlier Neutron data were combined with preliminary results from RBE experiments and microdosimetric measurements performed within the framework of two proton Therapy programmes. Different weighting functions were derived by unfolding calculations applied to data sets combining high energy gamma rays, Fast Neutrons and Fast protons.
-
the clinical rbe and microdosimetric characterization of radiation quality in Fast Neutron Therapy
Acta Oncologica, 1994Co-Authors: H G Menzel, Andre Wambersie, P PihetAbstract:High-LET radiation Therapy using Fast Neutrons is being applied regularly at several centres worldwide and in the future, other types of radiation qualities, such as protons and heavier ions and boron Neutron capture Therapy (BNCT) are likely to be used. The Neutron beams used are of considerably varying energy and thus considerable variations in the relative biological effectiveness (RBE) have been found. At present, no generally accepted method exists for the quantitative specification of these differences in radiation quality for clinical purposes. This is in clear discrepancy with the accuracy requirements in clinical dosimetry. An approach is presented which is based on a single parameter radiation quality characterization determined in combined microdosimetric and radiobiological experiments. It is shown that the method can meet the accuracy requirements of clinical dosimetry and that it is applicable within a concept of formalized procedure of clinical practice and experience ('clinical RBE').