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Electron ballistic in magnetic radiotherapy
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145 DESIGN OF COMPENSATORS
FOR PATIENTS WITH HIP
PROSTHESES UNDERGOING PELVIC IRRADIATION R. ALECU, J. FELDMEIER, T. HE, M. ALECU, W. CODRT, C.G. ORTON. GRACE HOSPITAL AND WAYNE STATE UNIVERSITY.DETROIT, USA. DESIGN OF COMPENSATORS FOR PATIENTS WITH HIP PROSTHESES UNDERGOING PELVIC IRRADIATION. R. Alecu, J. Feldeeier, T. He, M. Alecu, W. Court and C.G. Orton. Grace Hospital and Wayne State University, Detroit, USA. The perturbations in the doss distribution caused by a hip prosthesis Yhen treating pel vic cancers have been evaluated and found to be significant by several investigators. Treatment techniques not inclUding the prosthesis are orten not the best choice. The goal of this study is to investigats the feasibility and usefulness of design of compsnsators in routine clinical practice for any kind of hip prostheais. The calculation procedures and the aIgorfthes developed by the authors for generatinll the compensators are described for tvo systells zone based on a locally developed 3-D computerlzed treatmsnt planning systell and an other one practicable in any institution Yhich does not have access to a 3D treatment planning systee or CT. The mstho
Monte Carlo cak:ulated stopping power ratio waterlair for dinical proton therapy Joakim MetJjn l ,2 and Pedro Andre~
Dept. of Med. Roo. Phys., Karolinska Instinuet and University of Stockholm. Stockholm, Sweden 2 Dept. of Oncology, University of Uppsala, Uppsala, Sweden I
In order to compute stopping-power ratios water/air for use in clinical proton dosimetry a Monte Carlo code has been developed [1]. The main difference between the present code and other codes for proton transport is the inclusion of the detailed production of secondary electrons along the proton track. For this purpose the code is a Class-II type. where single proton-electron collisions yielding energy losses larger than a specific cut-off are considered individually. Proton multiple scattering is sampled from the complete Moliere distribution [2]. To take into account in an approximate way the effect of inelastic nuclear collisions the fraction of the incident energy that is converted to kinetic energy of charged panicles in the interaction [3] is deposited on the spot. The energy that goes to neutral particles is assumed to leave the scoring geometry without any energy deposition. Stopping-power ratios are calculated in-line. i.e, during the transport, thereby reducing the uncertainty of the calculated value [4]. The production and transport of the secondary electrons is used to determine an additional contribution to the stopping-power ratios obtained using the proton spectra alone.
12] [3] [4J
H. Palmans and F. Verhaegen Standard Dosimetry Laboratory, Department ofBiomcdical Physics University of Gent. BELGIUM
Clinicalprotonbeam therapy bas known an explosive growthin the last decennium, a growth that has not ended yet. A huge uniforntity in clinical (routine) proton beam dosimetry bas been established by two dosimetry protocols(ECHED andAAPM).In spite of this, the influence of chamber dependent parameter on the iOllisat:iOll chamber dosimetry. has not been cleared out profoundly. A comparative study between water calorimetry using the calorimeter of Gem and ionometry applying the ECHED protocol showed a discrepancy of 2.6% in dose to water response for 85 MeV protons. To evaluate if. and to whaI extent this difference can be attributed to iOll chamberdependent parameters, Monte Carlo (MC) calculations are indispensable to support and to understand measurements. Indications for the existe:nce of chamber dependent corrections are found in the above-mentiOllfd study in which the dose response of different ion chamber types showedsystematic differences of up to 1.1%. Existingproton Me codes do not allow to simulate complex geometries with different media. Therefore an existing MC code (PTRAN) has been modified With theoriginal code it is possibleto calculate depth dose profiles, spectral energy and radial distributions for pencil beams in water. The code applies Molliere's multiple scattering theory and Vavilov's energy straggling theory. Changes to the code are made in order to be able to make simulations for other materials than water and for complex geometries with more than one medium. Tbe program'saccuracy has been tested by making a comparison withmeasurements and calculations reportedin the literature. Preliminary results of the influence of chamber design and chamber materials on dose to water detennination will be presented.
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MODIFICATIONS TO A PROTON MONTE CARLO CODEFOREVALUATION OF IONCHAMBER DEPENDENT CORRECflONFACTORS FOR IONISATION CHAMBER DOSIMETRY IN PROTON BEAMS
J. Medin andP. Andreo, "PETRA: a MOIlle Carlo codefor the trllIIspOn of proIOl1S in matUt', Intemal Report, work in progress. P. Andreo. J. Medin and A. F. Bielajew. 'Conslraintsof themultiple seatl!ring tbeory of Molim in Monte Carlo simulations of the trBllSpOItof charged particles'. Med. Phys. 20 (5), 1993. S. M.SeIIZtl, •An ~ 0( theRole of CIuqed Secondarira from Nonelastic Nuclear IntenlClioos by Therapy Proton Beams in Waw", NISTIR 5221, t993. P. Andrea, "Improved calculations of SlOPPing-power ratiosand Iheir comlatiOll willi the quality of therapeutic photon beams'. IAEA-SM3~2, 1993.
ELECTRON BALLISTIC IN MAGNETIC RADIOTHERAPY F. Scarlat Institute of Atomic Physics, Bucharest, Romania Considering the absorbed dose distribution in depth achievable with beams of negative It mesons (pions) as the reference absorbed dose distribution (RAOO), it is found that the distributions provided by electron beams can offer significant advantages compared to the photon beams for the treatment of patients with superficial tumors. Also, dose distribution obtained with beams of protons, helium ions or heavy ions are of the same configurations like the pions. The method to get a new electron absorbed dose distribution, closer to that of pions, is based on a magnetic field, transversal on the propagation direction of the electron beams and located in front of the tumor. The paper presents the electron ballistic in a planning target volume (PTV) with electron beams having energies between 50 Me V and 100 MeV for magnetic fields varying between I V.s/m 2 and 5 V.s/m 2 In function of the PTV location and size. there exist values for electron energies and magnetic fields to obtain an absorbed dose distribution closer to the RAOO.
145 DESIGN OF COMPENSATORS
FOR PATIENTS WITH HIP
PROSTHESES UNDERGOING PELVIC IRRADIATION R. ALECU, J. FELDMEIER, T. HE, M. ALECU, W. CODRT, C.G. ORTON. GRACE HOSPITAL AND WAYNE STATE UNIVERSITY.DETROIT, USA. DESIGN OF COMPENSATORS FOR PATIENTS WITH HIP PROSTHESES UNDERGOING PELVIC IRRADIATION. R. Alecu, J. Feldeeier, T. He, M. Alecu, W. Court and C.G. Orton. Grace Hospital and Wayne State University, Detroit, USA. The perturbations in the doss distribution caused by a hip prosthesis Yhen treating pel vic cancers have been evaluated and found to be significant by several investigators. Treatment techniques not inclUding the prosthesis are orten not the best choice. The goal of this study is to investigats the feasibility and usefulness of design of compsnsators in routine clinical practice for any kind of hip prostheais. The calculation procedures and the aIgorfthes developed by the authors for generatinll the compensators are described for tvo systells zone based on a locally developed 3-D computerlzed treatmsnt planning systell and an other one practicable in any institution Yhich does not have access to a 3D treatment planning systee or CT. The mstho
Monte Carlo cak:ulated stopping power ratio waterlair for dinical proton therapy Joakim MetJjn l ,2 and Pedro Andre~
Dept. of Med. Roo. Phys., Karolinska Instinuet and University of Stockholm. Stockholm, Sweden 2 Dept. of Oncology, University of Uppsala, Uppsala, Sweden I
In order to compute stopping-power ratios water/air for use in clinical proton dosimetry a Monte Carlo code has been developed [1]. The main difference between the present code and other codes for proton transport is the inclusion of the detailed production of secondary electrons along the proton track. For this purpose the code is a Class-II type. where single proton-electron collisions yielding energy losses larger than a specific cut-off are considered individually. Proton multiple scattering is sampled from the complete Moliere distribution [2]. To take into account in an approximate way the effect of inelastic nuclear collisions the fraction of the incident energy that is converted to kinetic energy of charged panicles in the interaction [3] is deposited on the spot. The energy that goes to neutral particles is assumed to leave the scoring geometry without any energy deposition. Stopping-power ratios are calculated in-line. i.e, during the transport, thereby reducing the uncertainty of the calculated value [4]. The production and transport of the secondary electrons is used to determine an additional contribution to the stopping-power ratios obtained using the proton spectra alone.
12] [3] [4J
H. Palmans and F. Verhaegen Standard Dosimetry Laboratory, Department ofBiomcdical Physics University of Gent. BELGIUM
Clinicalprotonbeam therapy bas known an explosive growthin the last decennium, a growth that has not ended yet. A huge uniforntity in clinical (routine) proton beam dosimetry bas been established by two dosimetry protocols(ECHED andAAPM).In spite of this, the influence of chamber dependent parameter on the iOllisat:iOll chamber dosimetry. has not been cleared out profoundly. A comparative study between water calorimetry using the calorimeter of Gem and ionometry applying the ECHED protocol showed a discrepancy of 2.6% in dose to water response for 85 MeV protons. To evaluate if. and to whaI extent this difference can be attributed to iOll chamberdependent parameters, Monte Carlo (MC) calculations are indispensable to support and to understand measurements. Indications for the existe:nce of chamber dependent corrections are found in the above-mentiOllfd study in which the dose response of different ion chamber types showedsystematic differences of up to 1.1%. Existingproton Me codes do not allow to simulate complex geometries with different media. Therefore an existing MC code (PTRAN) has been modified With theoriginal code it is possibleto calculate depth dose profiles, spectral energy and radial distributions for pencil beams in water. The code applies Molliere's multiple scattering theory and Vavilov's energy straggling theory. Changes to the code are made in order to be able to make simulations for other materials than water and for complex geometries with more than one medium. Tbe program'saccuracy has been tested by making a comparison withmeasurements and calculations reportedin the literature. Preliminary results of the influence of chamber design and chamber materials on dose to water detennination will be presented.
148
147
[I]
MODIFICATIONS TO A PROTON MONTE CARLO CODEFOREVALUATION OF IONCHAMBER DEPENDENT CORRECflONFACTORS FOR IONISATION CHAMBER DOSIMETRY IN PROTON BEAMS
J. Medin andP. Andreo, "PETRA: a MOIlle Carlo codefor the trllIIspOn of proIOl1S in matUt', Intemal Report, work in progress. P. Andreo. J. Medin and A. F. Bielajew. 'Conslraintsof themultiple seatl!ring tbeory of Molim in Monte Carlo simulations of the trBllSpOItof charged particles'. Med. Phys. 20 (5), 1993. S. M.SeIIZtl, •An ~ 0( theRole of CIuqed Secondarira from Nonelastic Nuclear IntenlClioos by Therapy Proton Beams in Waw", NISTIR 5221, t993. P. Andrea, "Improved calculations of SlOPPing-power ratiosand Iheir comlatiOll willi the quality of therapeutic photon beams'. IAEA-SM3~2, 1993.
ELECTRON BALLISTIC IN MAGNETIC RADIOTHERAPY F. Scarlat Institute of Atomic Physics, Bucharest, Romania Considering the absorbed dose distribution in depth achievable with beams of negative It mesons (pions) as the reference absorbed dose distribution (RAOO), it is found that the distributions provided by electron beams can offer significant advantages compared to the photon beams for the treatment of patients with superficial tumors. Also, dose distribution obtained with beams of protons, helium ions or heavy ions are of the same configurations like the pions. The method to get a new electron absorbed dose distribution, closer to that of pions, is based on a magnetic field, transversal on the propagation direction of the electron beams and located in front of the tumor. The paper presents the electron ballistic in a planning target volume (PTV) with electron beams having energies between 50 Me V and 100 MeV for magnetic fields varying between I V.s/m 2 and 5 V.s/m 2 In function of the PTV location and size. there exist values for electron energies and magnetic fields to obtain an absorbed dose distribution closer to the RAOO.