DOCSLIB.ORG

Proposed Method for Measuring the LET of Radiotherapeutic Particle Beams Stephen D

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Proposed Method for Measuring the LET of Radiotherapeutic Particle Beams Stephen D University of New Mexico UNM Digital Repository Physics & Astronomy ETDs Electronic Theses and Dissertations Fall 11-10-2017 Proposed Method for Measuring the LET of Radiotherapeutic Particle Beams Stephen D. Bello University of New Mexico - Main Campus Follow this and additional works at: https://digitalrepository.unm.edu/phyc_etds Part of the Astrophysics and Astronomy Commons, Health and Medical Physics Commons, Other Medical Sciences Commons, and the Other Physics Commons Recommended Citation Bello, Stephen D.. "Proposed Method for Measuring the LET of Radiotherapeutic Particle Beams." (2017). https://digitalrepository.unm.edu/phyc_etds/167 This Dissertation is brought to you for free and open access by the Electronic Theses and Dissertations at UNM Digital Repository. It has been accepted for inclusion in Physics & Astronomy ETDs by an authorized administrator of UNM Digital Repository. For more information, please contact [email protected]. Dedication To my father, who started my interest in physics, and my mother, who encouraged me to expand my mind. iii Acknowledgments I’d like to thank my advisor, Dr. Michael Holzscheiter, for his endless support, as well as putting up with my relentless grammatical errors concerning the focus of our research. And Dr. Shuang Luan for his feedback and criticism. iv Proposed Method for Measuring the LET of Radiotherapeutic Particle Beams by Stephen Donald Bello B.S., Physics & Astronomy, Ohio State University, 2012 M.S., Physics, University of New Mexico, 2017 Ph.D, Physics, University of New Mexico, 2017 Abstract The Bragg peak geometry of the depth dose distributions for hadrons allows for precise and e↵ective dose delivery to tumors while sparing neighboring healthy tis- sue. Further, compared against other forms of radiotherapeutic treatments, such as electron beam therapy (EBT) or photons (x and γ-rays), hadrons create denser ion- ization events along the particle track, which induces irreparable damage to DNA, and thus are more e↵ective at inactivating cancerous cells. The measurement of radi- ation’s ability to inactivate cellular reproduction is the relative biological e↵ectiveness (RBE). A quality related to the RBE that is a measurable physical property is the linear energy transfer (LET), a measurement of the deposited energy over the par- ticle track. The purpose of this work was to develop a method of measuring LET of radiotherapeutic beams using an air-filled ionization chamber (IC) and liquid-filled ionization chamber (LIC). Through analysis of the IC and LIC signals, we deter- mined a correlation between the recombination index (IC/LIC) and dose-averaged LET. v Contents Abstract iv 1 Introduction 1 2 Radiotherapy 5 2.1 Fluence .................................. 7 2.2 AbsorbedDose .............................. 7 2.3 Radiation and Matter Interactions . 8 2.3.1 Charged-Particle Interactions . 9 2.4 Stopping Power . 10 2.4.1 The Bethe-Bloch Equation . 12 2.4.2 Continuous Slowing Down Approximation . 14 2.4.3 Multiple Coulomb Scattering . 15 2.5 Relative Biological E↵ectiveness (RBE) . 17 2.5.1 RBE Dependencies . 20 2.6 Linear Energy Transfer (LET) . 23 3Dosimetry 27 3.1 Ionization Chambers . 28 3.2 Initial Recombination . 30 3.2.1 Geminate Recombination - Onsager’s Theory . 31 vi Contents 3.2.2 Columnar Recombination - Ja↵e’sTheory ........... 33 3.3 General Recombination . 35 4DeterminationofLET 40 4.1 The Experimental Setup . 41 4.1.1 The Heidelberg Ion-Beam Therapy Center . 44 4.1.2 Characteristics of the Beam . 46 4.1.3 Gaussian Distribution of the Beam . 47 4.2 Instrumentation.............................. 49 4.2.1 The IC: PTW Roos . 49 4.2.2 The LIC: MicroLion . 51 4.3 FLUKAandLET............................. 52 4.3.1 LETAverages........................... 53 4.4 Experimental Results . 58 4.4.1 Beam Spread Corrections on the IC . 64 4.4.2 Beam Spot Size Corrections . 67 4.4.3 Proton Calibration Curves . 76 4.4.4 Carbon Calibration Curves . 77 4.4.5 Oxygen Calibration Curves . 78 4.4.6 Combined Calibration Curves . 80 Summary and Conclusions 84 Discussion and Outlook 87 References 89 vii Chapter 1 Introduction The geometric profile of energy deposited by radiotherapeutic hadron beams is ad- vantageous for treating deep-seated tumors compared to other forms of radiation, such as electron beam therapy (EBT) and photons (x-rays and γ-rays). The steep increase and subsequent exponential decay in the depth dose distribution near the end of the particle track (i.e. the Bragg peak), allows for accurate three-dimensional painting of tumors while sparing healthy tissue located along the entrance plateau and distal tail of the depth dose distribution from the majority of damaging radia- tion. The nuclear charge of hadrons also allows radial steering of the beam, enabling true 3-D mapping of tumorous masses. For hadrons, heavier charged particles have several advantages over lighter charged particles. Radial scattering, where the beam spreads due to multiple Coulomb scattering, has dependency on the atomic mass, which makes heavier charged particles superior (i.e. He instead of H). Also, due to their greater atomic mass and nuclear charge, carbon and oxygen ions have higher ionization event densities along the particle track compared to protons. This higher ionization event density induces numerous forms of damage to DNA molecules, rang- ing from base loss and base change, H2-bond breakage, pyrimidine dimers, DNA cross-linkage, single-strand breaks (SSB) and double-strand breaks (DSB). These ef- 1 Chapter 1. Introduction fects are prominent around the Bragg peak, where the energy deposited along the particle track is several times that of the distal tail and entrance plateau, leading to the increased biological e↵ectiveness of hadrons compared to other forms of radiation in the target region. For hadrons and other types of ionizing radiation, the percentage of cells within the tumor that survive and reproduce is related to a biological quality known as the relative biological e↵ectiveness (RBE). The RBE is the ratio between the absorbed dose required by ionizing radiation and x-rays (220 keV photons) to induce identical damage to DNA molecules and biological tissues. However, calculating RBE is dif- ficult due to its dependency on multiple biological and physical variables - type of ionizing particle, dose, dose rate, type of tissue, oxygenation level of the tissue and the selected biological endpoint (i.e. the expected survival fraction). Therefore, it’s advantageous to work with a physical property of the beam related to the RBE - the linear energy transfer (LET), which is a measurement of the energy deposited along the particle track. LET can be calculated using Monte Carlo codes (Fluka, Shield-HIT12A) [Ferrari 2005, Bassler 2017], which simulate conditions for both tis- sues and experimental setups. But so far, no method for directly measuring LET, which would make such calculations unnecessary, has been reported. A correlation between RBE and LET has been reported [Sorensen 2011], which sug- gests LET is an acceptable physical surrogate for the purposes of treatment planning. The ability to directly measure LET in-situ would be advantageous for keeping the high RBE region on the target volume and away from healthy tissues. To perform LET measurements of radiation, two ionization chambers were utilized. The first was an air-filled ionization chamber (IC) and the second was a liquid-filled ioniza- tion chamber (LIC), which was filled with isooctane. Although ICs have higher resolution than LICs in beam direction, LICs are preferable for dose distributions with narrow beam profiles and sharp penumbras. Due to the higher density of liquids 2 Chapter 1. Introduction compared to gases, LICs can be constructed several times smaller than ICs. How- ever, while LICs are advantageous due to their small diameter, the high density of liquids leads to recombination e↵ects within the sensitive volume, which suppresses the detected signal (i.e. quenching). On the other hand, ICs, due to the low density of air, experiences little recombination. All, or nearly all, of the electron-ion pairs created in ICs are captured by the collecting electrode while an appreciable fraction of electron-ion pairs in LICs recombine. There are two forms of recombination. The first is Initial Recombination (IR), which involves electron-ion pairs produced by a single particle track recombining before detection by the ionization chamber. Initial Recombination consists of two com- ponents. Geminate recombination (described by Onsager’s Theory) [Onsager 1938] involves an electron recombining with the original ion while columnar recombination (Ja↵e’s Theory) [Acciarri 2013] involves an electron recombining with a di↵erent ion produced along the track of the same charged particle. The second is General Re- combination (GR), which involves electrons and ions produced along the tracks from di↵erent charged particles recombining into a neutral atom. General Recombination is inversely proportional to the voltage applied across the sensitive volume. Thus, at the voltages used in the experiment, GR was e↵ectively negligible in the LIC. Initial Recombination on the other hand, is dependent upon the LET, with higher LET particles producing more ionization events per unit length along their track, creating more electron-ion pairs. Our work involved developing a method capable of relating LET to the ratio be- tween the IC and LIC signals. In the water phantom at the Heidelberg Ion-Beam Therapy Center (HIT), the ionization chambers were held flush to each other, the IC (PTW Roos) in front and LIC (MicroLion) in the rear. The ionization chambers were attached to a mobile apparatus capable of precise movements, ranging from centime- ter to sub-millimeter steps. This allowed for accurate measurement of di↵erent ion 3 Chapter 1. Introduction species, one after the other, at identical depths within the water phantom for the IC and LIC, the latter of which experienced quenching due to IR (GR was minimized by the applied voltage).
Load more

Recommended publications
  • Radiation Therapy
    Radiation Therapy Use of radiation to kill diseased cells. Cancer is the disease that is almost always treated when using radiation. • One person in three will develop some form of cancer in their lifetime. • One person in five will die from that cancer. • Cancer is the second leading cause of death but exceeds all other diseases in terms of years of working-life lost. Diagrammatic representation of a Image removed. slice through a large solid tumor. From Webster’s Medical Dictionary: Cancer – A malignant tumor of potentially unlimited growth that expands locally by invasion and sytemically by metastasis. Tumor – an abnormal mass of tissues that arises from cells of pre-existent tissue, and serves no useful purpose. Malignant – dangerous and likely to be fatal (as opposed to “benign,” which refers to a non-dangerous growth). 1 Unlimited Growth: • Cancer cells multiply in an unregulated manner independent of normal control mechanisms. • Formation of a solid mass in organs. • Multiplication of bone marrow stem cells gives rise to leukemia, a cancer of the blood. Image removed. Solid tumors: • Primary tumor may be present in the body for months or years before clinical symptoms develop. • Some tumors can be managed and the patient often cured provided there has been no significant invasion of vital organs. • Patients do not often die of primary tumors---brain tumors are the exception. Metastases: • The spread of tumor cells from one part of the body to another, usually by the blood or lymph systems. • Metastases are more usually the cause of death. • Metastases are especially common in the bone marrow, liver, lungs and brain.
    [Show full text]
  • 30. Radioactivity and Radiation Protection 1 30
    30. Radioactivity and radiation protection 1 30. RADIOACTIVITY AND RADIATION PROTECTION Revised August 2011 by S. Roesler and M. Silari (CERN). 30.1. Definitions [1,2] 30.1.1. Physical quantities : • Fluence, Φ (unit: 1/m2): The fluence is the quotient of dN by da, where dN is the number of particles incident upon a small sphere of cross-sectional area da Φ = dN/da . (30.1) In dosimetric calculations, fluence is frequently expressed in terms of the lengths of the particle trajectories. It can be shown that the fluence, Φ, is given by Φ = dl/dV, where dl is the sum of the particle trajectory lengths in the volume dV . • Absorbed dose, D (unit: gray, 1 Gy=1 J/kg=100 rad): The absorbed dose is the energy imparted by ionizing radiation in a volume element of a specified material divided by the mass of this volume element. • Kerma, K (unit: gray): Kerma is the sum of the initial kinetic energies of all charged particles liberated by indirectly ionizing radiation in a volume element of the specified material divided by the mass of this volume element. • Linear energy transfer, L or LET (unit: J/m, often given in keV/µm): The linear energy transfer is the mean energy, dE, lost by a charged particle owing to collisions with electrons in traversing a distance dl in matter. Low-LET radiation: x rays and gamma rays (accompanied by charged particles due to interactions with the surrounding medium) or light charged particles such as electrons that produce sparse ionizing events far apart at a molecular scale (L < 10 keV/µm).
    [Show full text]
  • Ionoacoustic Bragg Peak Localization for Charged Particle Cancer Therapy
    Ionoacoustic Bragg Peak Localization for Charged Particle Cancer Therapy Siavash Yousefi, December-9-2015 Jonathan Alava, 7 Roberts Proton Therapy Center in Philadelphia Cancer Treatment: Protons vs. X-ray Superior Dose Distribution Photon vs. Proton Dose Distribution http://www.wikiwand.com/en/Particle_therapy Knopf, Antje-Christin, and Antony Lomax. "In vivo proton range verification: a review." Physics in medicine and biology 58.15 (2013): R131. Proton and Carbon Therapy Facilities Carbon Therapy Facilities PROTON THERAPY FACILITIES External Beam LINAC External Beam LINAC Proton Therapy Facility : C Heidelberg Ion Therapy Center 60m x 70m Compact Design Uncertainties in Proton Therapy • Due to sharp dose fall-off at Bragg peak • Protons are more sensitive to uncertainties than photon • Damaging surrounding healthy tissue/not treating tumor Sources of uncertainties • Stochastic error (CT noise) • CT artifacts • CT resolution (partial volume effect) • Hounsfield unit (HU) conversion method Proton Range Verification Techniques Measurement technique › Direct › Indirect: range is implied from another signal Timing › Online: during treatment delivery › Offline: performed after completion of the treatment Direct Indirect Prompt gamma imaging (3D) Range probes PET imaging (3D) Online Proton radiography Ionoacoustic PET imaging (3D) Offline MRI (3D) PET Imaging for Range Verification • Protons and heavy ions cause nuclear fragmentation reactions • Generation of positron emitting isotopes (15O, 11C) • PET scan measures the distribution of activities • Clinically appealing; no additional dose to the patient PET Verification of Proton Therapy: Operational Modalities In-beam PET Offline PET In-room PET PET Verification Studies in Patient Clival chordoma receiving a posterior–anterior followed by a lateral field ~26 min (T1) and 16 min (T2) after completion.
    [Show full text]
  • Alpha Emitting Radionuclides and Radiopharmaceuticals for Therapy"
    Report Technical Meeting on "Alpha emitting radionuclides and radiopharmaceuticals for therapy" June, 24−28, 2013 IAEA Headquarters, Vienna, Austria 1 BACKGROUND An alpha (α)-particle is a ionised 4He nucleus with a +2 electric charge and, therefore, it is relatively heavier than other subatomic particles emitted from decaying radionuclides such as electrons, neutrons, and protons. Because of this physical properties, α-particles are more effective ionization agents with linear energy transfer (LET) of the order of magnitude of 100 keV/µm, and are highly efficient in depositing energy over a short range in tissue (50–100 µm). Actually, a α-particle deposits 1500 times more energy per unit path length than a β- particle. The high mean energy deposition in tissues gives α-radiation exquisite cytotoxicity, which commonly manifests itself within the range of cell’s dimensions. This high LET may allow for an accurately controlled therapeutic modality that can be targeted to selected malignant cells with negligible burden to normal tissues. The short path length renders α-emitters suitable for treatment of minimal disease such as micro metastases or residual tumour after surgical resection of a primary lesion, hematologic cancers, infections, and compartmental cancers. A highly desirable goal in cancer therapy is the ability to target malignant cells while sparing normal cells. If significant differential targeting is achieved by a radiolabelled vector specifically designed to hold onto cancer cells, then a toxic payload on the vector will deliver a lethal dose preferentially to those cells expressing higher concentrations of the target molecule. This could be achieved by using highly cytotoxic α-particle radiation carried to specific sites of cancer cells by appropriate vectors.
    [Show full text]
  • Stereotactic Radiosurgery with Charged-Particle Beams: Technique and Clinical Experience
    Review Article Stereotactic radiosurgery with charged-particle beams: technique and clinical experience Richard P. Levy1, Reinhard W. M. Schulte2 1Advanced Beam Cancer Treatment Foundation, 887 Wildrose Circle, Lake Arrowhead, CA 92352-2356 USA; 2Department of Radiation Medicine, Loma Linda University Medical Center, Loma Linda, CA, 92354, USA Corresponding to: Richard Levy, MD, PhD. PO Box 2356, Lake Arrowhead, CA 92352-2356 USA. Email: [email protected]. Abstract: Stereotactic radiosurgery using charged-particle beams has been the subject of biomedical research and clinical development for almost 60 years. Energetic beams of charged particles of proton mass or greater (e.g., nuclei of hydrogen, helium or carbon atoms) manifest unique physical and radiobiological properties that offer advantages for neurosurgical application and for neuroscience research. These beams can be readily collimated to any desired cross-sectional size and shape. At higher kinetic energies, the beams can penetrate entirely through the patient in a similar fashion to high-energy photon beams but without exponential fall-off of dose. At lower kinetic energies, the beams exhibit increased dose-deposition (Bragg ionization peak) at a finite depth in tissue that is determined by the beam’s energy as it enters the patient. These properties enable highly precise, 3-dimensional placement of radiation doses to conform to uniquely shaped target volumes anywhere within the brain. Given the radiosurgical requirements for diagnostic image acquisition and fusion, precise target delineation and treatment planning, and millimeter- or even submillimeter-accurate dose delivery, reliable stereotactic fixation and immobilization techniques have been mandatory for intracranial charged particle radiosurgery. Non-invasive approaches initially used thermoplastic masks with coordinate registration made by reference to bony landmarks, a technique later supplemented by using vacuum-assisted dental fixation and implanted titanium fiducial markers for image guidance.
    [Show full text]
  • August 31, 1963 NATURE 923
    No. 4896 August 31, 1963 NATURE 923 RADIOBIOLOGY missed, as Berry, Oliver and Porter seem to suggest, though their imputation that cost is our sole consideration A Fast-neutron Source for Radiotherapy is, of course, incorrect. IN a recent note, Lomer and Greene1 have recommended It is perhaps worth enlarging a little on the importance the development of a 14-MeV fast-neutron source for of compactness. In radiotherapy accurate direction of the radiotherapy. We feel that there are disadvantages to beam at the tumour is a primary consideration, and this is this approach. The relative biological effectiveness of best achieved by using a flexibly mounted radiation source fast neutrons is related to their linear energy transfer, so that the beam may be moved with respect to a com­ which in turn varies inversely with the energy of the fortably placed patient, rather than the patient 'lined up' neutron•,•. It has been shown that cell-killing by 1-2- to the machine: compactness is thus important because it facilitates MeV neutrons (linear energy transfer, 50-60 keV/µ) is accurate treatment. relatively independent of oxygen•. As the energy of the We are, of course, well aware that designing a neutron neutrons is increased, the effect becomes more oxygen­ collimator is a problem, and the solution of this problem dependent•-30-MeV neutrons would have a linear energy is naturally an important part of our development pro­ gra,mme. transfer similar to 250-kV X-rays, and hence a similar oxygen-dependence. Tf one is to expect an improvement Furthermore, even if 14-MeV neutrons prove to have no in the results of radiotherapy due to the relative oxygen­ biological advantage over megavoltage X-rays, the D-T source independence of the effect of fast neutrons, then one must may still be competitive with high-energy X-ray units, attempt to use those neutrons the effects of which are in so far as there are reasonable grounds for believing relatively oxygen-independent; this cannot be claimed that they will produce similar dose distributions inside a patient.
    [Show full text]
  • Dose Reporting in Ion Beam Therapy
    IAEA-TECDOC-1560 Dose Reporting in Ion Beam Therapy Proceedings of a meeting organized jointly by the International Atomic Energy Agency and the International Commission on Radiation Units and Measurements, Inc. and held in Ohio, United States of America, 18–20 March 2006 June 2007 IAEA-TECDOC-1560 Dose Reporting in Ion Beam Therapy Proceedings of a meeting organized jointly by the International Atomic Energy Agency and the International Commission on Radiation Units and Measurements, Inc. and held in Ohio, United States of America, 18–20 March 2006 June 2007 The originating Section of this publication in the IAEA was: Applied Radiation Biology and Radiotherapy Section International Atomic Energy Agency Wagramer Strasse 5 P.O. Box 100 A-1400 Vienna, Austria DOSE REPORTING IN ION BEAM THERAPY IAEA, VIENNA, 2007 IAEA-TECDOC-1560 ISBN 978–92–0–105807–2 ISSN 1011–4289 © IAEA, 2007 Printed by the IAEA in Austria June 2007 FOREWORD Following the pioneering work in Berkeley, USA, ion beam therapy for cancer treatment is at present offered in Chiba and Hyogo in Japan, and Darmstadt in Germany. Other facilities are coming close to completion or are at various stages of planning in Europe and Japan. In all these facilities, carbon ions have been selected as the ions of choice, at least in the first phase. Taking into account this fast development, the complicated technical and radiobiological research issues involved, and the hope it raises for some types of cancer patients, the IAEA and the International Commission on Radiation Units and measurements (ICRU) jointly sponsored a technical meeting held in Vienna, 23–24 June 2004.
    [Show full text]
  • Α-Particle Emitters in Radioimmunotherapy: New And
    INVITED COMMENTARY ␣-Particle Emitters in Radioimmunotherapy: New and Welcome Challenges to Medical Internal Dosimetry sulting in the release of the daughter as the cellular S value methodology to Over the past decade, there has a free element. include time-dependent partial contri- been progressively stronger interest in Two very different approaches can butions of the various daughter emis- the use of ␣-particle emitters for radio- be applied to the dosimetry of ␣-parti- sions in the serial decay chains of immunotherapy (1–6). With proper lo- cle emitters. One is microdosimetry, in 225Ac, 221At, 213Bi, and 223Ra. In their calization of the labeled antibody, the which the probabilistic nature of approach, a cutoff time (␶0) is selected high linear energy transfer of ␣-parti- ␣-particle emission and its trajectory before which free elemental daughter cles provides a correspondingly high through the cell and cell nucleus are radionuclides are considered to remain probability of mitotic cell kill when explicitly considered (1,8–10). In a in the same source configuration as compared with an equivalent number microdosimetric analysis, probability that assumed for the parent. At short of cellular traversals by lower linear density functions of specific energy are cutoff times, the daughter radionu- energy transfer ␤-particles. Conse- obtained (stochastic expressions of en- clides, which are released as free ele- quently, much developmental work ergy imparted per unit mass to small ments after the ␣-decay of the parent, has been initiated in the production, targets), as well as frequencies of zero- diffuse or migrate far from the site of chemistry, and preclinical trials of can- dose contribution.
    [Show full text]
  • Alpha Emitters for Radiotherapy: Basic Radiochemistry to Clinical Studies Part 1
    Journal of Nuclear Medicine, published on March 15, 2018 as doi:10.2967/jnumed.116.186338 Alpha Emitters for Radiotherapy: Basic Radiochemistry to Clinical Studies _ Part 1 Running title: Alpha Emitters for Radiotherapy Sophie Poty1, Lynn C. Francesconi2,3, Michael R. McDevitt1,4, Michael J. Morris,5 Jason S. Lewis1,6 1Department of Radiology and the Program in Molecular Pharmacology, Memorial Sloan Kettering Cancer Center, New York, NY, USA 2Department of Chemistry, Hunter College, New York, NY, USA 3The Graduate Center of the City University of New York, New York, NY, USA 4Departments of Radiology, Weill Cornell Medical College, New York, NY, USA 5Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY, USA 6Departments of Radiology and Pharmacology, Weill Cornell Medical College, New York, NY, USA Correspondence: Jason S. Lewis, PhD, 1275 York Avenue, New York, NY 10065, USA. Phone: 646-888-3038, FAX: 646-422-0408, Email: [email protected] First author: Sophie Poty, PhD, 1275 York Avenue, New York, NY 10065, USA. Phone: 646- 888-3080, FAX: 646-422-0408, Email: [email protected] Word count: 5317 Disclaimer: The authors have nothing to disclose. Financial support: The authors gratefully acknowledge the Radiochemistry and Molecular Imaging Probe core, which was supported in part by the NIH/NCI Cancer Center Support Grant P30 CA008748. We gratefully acknowledge Mr. William H. and Mrs. Alice Goodwin and the Commonwealth Foundation for Cancer Research and The Center for Experimental Therapeutics of Memorial Sloan Kettering Cancer Center (JSL) and the fellowship from the François Wallace Monahan Fellowship from the JLM Benevolent Fund (SP).
    [Show full text]
  • RELATIVE BIOLOGICAL EFFECTIVENESS in ION BEAM THERAPY TECHNICAL REPORTS SERIES No
    10.24 mm technical reportS series no. 46i This report covers all the aspects of the relative biological effectiveness (RBE) of ion beams, including laboratory measurements of RBE and the important variables that influence it, dose related quantities and units, and approaches to the clinical use of the concept of RBE based on experimental findings, theoretical models, and previous clinical experience with fast neutrons and ions. RBE is a simple concept but its clinical Technical Reports SeriEs No. 46i application is complex. Future developments in ion therapy will require a coherent approach to the reporting of therapies and their outcomes, not only for comparison with other ion facilities but also with conventional and newly developing photon irradiation techniques. The report is the result of a joint initiative between the IAEA and the International Commission on Radiation Relative Biological Units and Measurements, and is the only current extensive review of ion RBE. Relative Biological Effectiveness in Therapy Ion Beam Effectiveness in Ion Beam Therapy Jointly sponsored by the IAEA and ICRU INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA ISBN 978–92–0–107807–0 ISSN 0074–1914 07-32641_D461_CovI-IV.indd 1 2008-04-01 10:47:19 RELATIVE BIOLOGICAL EFFECTIVENESS IN ION BEAM THERAPY TECHNICAL REPORTS SERIES No. 461 RELATIVE BIOLOGICAL EFFECTIVENESS IN ION BEAM THERAPY JOINTLY SPONSORED BY THE INTERNATIONAL ATOMIC ENERGY AGENCY AND THE INTERNATIONAL COMMISSION ON RADIATION UNITS AND MEASUREMENTS INTERNATIONAL ATOMIC ENERGY AGENCY VIENNA, 2008 COPYRIGHT NOTICE All IAEA scientific and technical publications are protected by the terms of the Universal Copyright Convention as adopted in 1952 (Berne) and as revised in 1972 (Paris).
    [Show full text]
  • Basic Physics of Proton Therapy
    University of Florida Proton Therapy Institute Basic Physics of Proton Therapy Roelf Slopema overview I. basic interactions . energy loss . scattering . nuclear interactions II. clinical beams . pdd . lateral penumbra interactions / energy loss Primarily protons lose energy in coulomb interactions with the outer-shell electrons of the target atoms. • excitation and ionization of atoms • loss per interaction small ‘continuously slowing down’ • range secondary e+ <1mm dose absorbed locally • no significant deflection protons by electrons interactions / energy loss Energ y loss is given b y Bethe-Bloch equ ation: + corrections Tmax max energy transfer to free electron Tmax max energy transfer to free electron • to first order: –dE/dx 1/speed2 2 2 • max electron energy: Tmax 4Tm4 T mec /m/ mpc T=200 MeV Tmax 0.4 MeV range 1.4mm ….but most electrons far lower energy in practice we use range-energy tables and measured depth dose curves. Equations from Review of particle physics, C. Amsler et al., Physics Letters B667, 1 (2008) stopping power water stopping power water p+ 200MeV Bragg peak Bragg peak Bragg peak William Bragg W.H. Bragg and R. Kleeman, On the ionization curves of radium, Philosophical Magazine S6 (1904), 726-738 stopping power Graph based on NIST data interactions / scattering PiPrimaril y protons scatter d ue to el asti c coulomb interactions with the target nuclei. • many, small angle deflections • full description Moliere, gaussian approx. Highland p proton momentum L target thickness v proton speed LR target radiation length . 0 1/pv 1/(2*T) T<<938MeV -050.5 . material dependence: 0 1/LR 2 2 1 g/cm of water (LR =36.1 g/cm ) 0=5mrad for T=200MeV 2 2 1 g/cm of lead (LR = 6.37 g/cm ) 0=14mrad for T=200MeV Highland neglects large-angle tails, but works well in many situations… Equation from Gottschalk (Passive beam spreading) radial spread in water Approximation: 0.02 x range Calculation using Highland’s equation.
    [Show full text]
  • The Biological Effects of Space Radiation During Long Stays in Space
    Biological Sciences in Space, Vol.18 No.4 (2004):Ohnishi, 201-205 K. and Ohnishi, T. © 2004 Jpn. Soc. Biol. Sci. Space The Biological Effects of Space Radiation during Long Stays in Space Ken Ohnishi and Takeo Ohnishi Department of Biology, Nara Medical University School of Medicine,Shijo-cho 840, Kashihara, Nara 634-8521, Japan. Abstract Many space experiments are scheduled for the International Space Station (ISS). Completion of the ISS will soon become a reality. Astronauts will be exposed to low-level background components from space radiation including heavy ions and other high-linear energy transfer (LET) radiation. For long-term stay in space, we have to protect human health from space radiation. At the same time, we should recognize the maximum permissible doses of space radiation. In recent years, physical monitoring of space radiation has detected about 1 mSv per day. This value is almost 150 times higher than that on the surface of the Earth. However, the direct effects of space radiation on human health are currently unknown. Therefore, it is important to measure biological dosimetry to calculate relative biological effectiveness (RBE) for human health during long-term flight. The RBE is possibly modified by microgravity. In order to understand the exact RBE and any interaction with microgravity, the ISS centrifugation system will be a critical tool, and it is hoped that this system will be in operation as soon as possible. Key words; space, space radiation, biological effect, high-LET, ISS Characteristics of space and the composition of space radiation the radiation being composed of α-particles and heavy For several years, human beings have been particles.
    [Show full text]