ICRP Publication 127
Radiological Protection in Ion Beam Radiotherapy
Recommended citation
ICRP, 2014. Radiological Protection in Ion Beam Radiotherapy. ICRP Publication 127. Ann. ICRP 43(4).
Authors on behalf of ICRP
Y. Yonekura, H. Tsujii, J.W. Hopewell, P. Ortiz Lopez, J-M. Cosset, H. Paganetti, A. Montelius, D. Schardt, B. Jones, T. Nakamura
Abstract - The goal of external-beam radiotherapy is to provide precise dose localisation in the treatment volume of the target with minimal damage to the surrounding normal tissue. Ion beams, such as protons and carbon ions, provide excellent dose distributions due primarily to their finite range, allowing a significant reduction of undesired exposure of normal tissue. Careful treatment planning is required for the given type and localisation of the tumour to be treated in order to maximise treatment efficiency and minimise the dose to normal tissue. Radiation exposure in outof-field volumes arises from secondary neutrons and photons, particle fragments, and photons from activated materials. These unavoidable doses should be considered from the standpoint of radiological protection of the patient.
Radiological protection of medical staff at ion beam radiotherapy facilities requires special attention. Appropriate management and control are required for the therapeutic equipment and the air in the treatment room that can be activated by the particle beam and its secondaries. Radiological protection and safety management should always conform with regulatory requirements. The current regulations for occupational exposures in photon radiotherapy are applicable to ion beam radiotherapy with protons or carbon ions. However, ion beam radiotherapy requires a more complex treatment system than conventional radiotherapy, and appropriate training of staff and suitable quality assurance programmes are recommended to avoid possible accidental exposure of patients, to minimise unnecessary doses to normal tissue, and to minimise radiation exposure of staff.
© 2014 ICRP. Published by SAGE.
Keywords: Radiotherapy; Ion beam; Proton; Carbon ion.
AUTHORS ON BEHALF OF ICRP Y. YONEKURA, H. TSUJII, J.W. HOPEWELL, P. ORTIZ LÓPEZ, J-M. COSSET, H. PAGANETTI, A. MONTELIUS, D. SCHARDT, B. JONES, T. NAKAMURA
Key Points
External-beam radiotherapy relies on precise dose localisation in the target treatment volume with minimal damage to the surrounding normal tissue. The success of treatment largely depends on the performance and capacity of accelerators, the beam delivery system, and the quality of the treatment planning systems used.
The clinical use of ion beams, such as protons and carbon ions, provides precise dose distributions due primarily to their finite range in tissue. Such precise deposition of energy in tumour volumes enables a significant reduction in radiation exposure of uninvolved normal tissue.
The clinical advantage of ion beam radiotherapy results from the manner in which protons and carbon ions lose their energy in tissue. Much of their energy is lost near the end of their range in tissue. This peak of energy loss or stopping power is called the ‘Bragg peak’. This physical phenomenon is exploited in ion beam therapy of cancer to achieve a higher absorbed dose within the tumour than in surrounding healthy tissues.
Relative biological effectiveness (RBE) values for different ions vary for different endpoints but tend to increase with increments of stopping power or linear energy transfer (LET) up to a maximum value before declining. Proton beams in clinical use are low-LET radiations, hence the RBE values are very close to those of high-energy x rays. For a given biological endpoint, carbon ions have higher RBE values than protons. RBE values increase with depth, and have their maximum near the depth where the Bragg peak occurs.
An ion beam delivery system generally consists of an accelerator, a transport beam line, and an irradiation system, where dose is delivered to the patient as either a narrow beam (pencil beam scanning method) or a broadened beam (broad beam method). When ion beams pass through or hit these beam line structures, secondary radiations including neutrons are produced. Some of the particles in the structures can become radioactive, and form an auto radioactive component of the beam.
The first step for ion beam radiotherapy, similar to any medical procedure, is justification. The proper selection of the patient should be based on knowledge of radiation oncology, the specific tumour to be treated, and available clinical results to provide the optimal benefit to the patient.
Careful treatment planning is required for optimisation to maximise the efficiency of treatment and minimise the dose to normal tissue, and depends on the treatment method and the targeted tumour. Theoretically, ion beam radiotherapy delivers radiation dose to the target volume more efficiently than conventional radiotherapy, while minimising undesired exposure of normal tissue. Nonetheless, the treatment planning must be sufficiently precise to avoid damaging the critical organs or tissues within or near the target.
Doses in the out-of-field volumes arise from the secondary neutrons and photons, particle fragments, and photons from activated materials. These undesired but unavoidable doses should be considered from the standpoint of radiological protection. Secondary neutrons are the major contributor to absorbed dose in areas distance from the treatment volume. The pencil beam scanning method can minimise this type of radiation exposure.
Imaging procedures are essential in treatment planning, similar to other modern radiotherapies, and deliver an additional small dose of radiation to the patient.
Appropriate management is required for the therapeutic equipment and the air in the treatment room which is activated. Management should always conform with regulatory requirements. The current regulations for occupational exposures in photon radiotherapy are applicable to ion beam radiotherapy with protons or carbon ions.
After treatment with ion beams, the patient will be slightly radioactive for a short time. However, radiation exposure of their family members and caretakers, as well as the public, due to this activation is negligible, and no specific protection procedures are required. Thus, the methods of radiological protection for public exposures in photon radiotherapy facilities are applicable to, and adequate for, ion beam radiotherapy facilities.
As ion beam radiotherapy requires a more complex treatment system than conventional radiotherapy, appropriate training of staff and suitable quality assurance programmes are essential to avoid possible accidental exposure of patients.
Executive Summary: Not included in this publication
ICRP, 2014. Radiological Protection in Ion Beam Radiotherapy. ICRP Publication 127. Ann. ICRP 43(4).
Authors on behalf of ICRP
Y. Yonekura, H. Tsujii, J.W. Hopewell, P. Ortiz Lopez, J-M. Cosset, H. Paganetti, A. Montelius, D. Schardt, B. Jones, T. Nakamura
Abstract - The goal of external-beam radiotherapy is to provide precise dose localisation in the treatment volume of the target with minimal damage to the surrounding normal tissue. Ion beams, such as protons and carbon ions, provide excellent dose distributions due primarily to their finite range, allowing a significant reduction of undesired exposure of normal tissue. Careful treatment planning is required for the given type and localisation of the tumour to be treated in order to maximise treatment efficiency and minimise the dose to normal tissue. Radiation exposure in outof-field volumes arises from secondary neutrons and photons, particle fragments, and photons from activated materials. These unavoidable doses should be considered from the standpoint of radiological protection of the patient.
Radiological protection of medical staff at ion beam radiotherapy facilities requires special attention. Appropriate management and control are required for the therapeutic equipment and the air in the treatment room that can be activated by the particle beam and its secondaries. Radiological protection and safety management should always conform with regulatory requirements. The current regulations for occupational exposures in photon radiotherapy are applicable to ion beam radiotherapy with protons or carbon ions. However, ion beam radiotherapy requires a more complex treatment system than conventional radiotherapy, and appropriate training of staff and suitable quality assurance programmes are recommended to avoid possible accidental exposure of patients, to minimise unnecessary doses to normal tissue, and to minimise radiation exposure of staff.
© 2014 ICRP. Published by SAGE.
Keywords: Radiotherapy; Ion beam; Proton; Carbon ion.
AUTHORS ON BEHALF OF ICRP Y. YONEKURA, H. TSUJII, J.W. HOPEWELL, P. ORTIZ LÓPEZ, J-M. COSSET, H. PAGANETTI, A. MONTELIUS, D. SCHARDT, B. JONES, T. NAKAMURA
Key Points
External-beam radiotherapy relies on precise dose localisation in the target treatment volume with minimal damage to the surrounding normal tissue. The success of treatment largely depends on the performance and capacity of accelerators, the beam delivery system, and the quality of the treatment planning systems used.
The clinical use of ion beams, such as protons and carbon ions, provides precise dose distributions due primarily to their finite range in tissue. Such precise deposition of energy in tumour volumes enables a significant reduction in radiation exposure of uninvolved normal tissue.
The clinical advantage of ion beam radiotherapy results from the manner in which protons and carbon ions lose their energy in tissue. Much of their energy is lost near the end of their range in tissue. This peak of energy loss or stopping power is called the ‘Bragg peak’. This physical phenomenon is exploited in ion beam therapy of cancer to achieve a higher absorbed dose within the tumour than in surrounding healthy tissues.
Relative biological effectiveness (RBE) values for different ions vary for different endpoints but tend to increase with increments of stopping power or linear energy transfer (LET) up to a maximum value before declining. Proton beams in clinical use are low-LET radiations, hence the RBE values are very close to those of high-energy x rays. For a given biological endpoint, carbon ions have higher RBE values than protons. RBE values increase with depth, and have their maximum near the depth where the Bragg peak occurs.
An ion beam delivery system generally consists of an accelerator, a transport beam line, and an irradiation system, where dose is delivered to the patient as either a narrow beam (pencil beam scanning method) or a broadened beam (broad beam method). When ion beams pass through or hit these beam line structures, secondary radiations including neutrons are produced. Some of the particles in the structures can become radioactive, and form an auto radioactive component of the beam.
The first step for ion beam radiotherapy, similar to any medical procedure, is justification. The proper selection of the patient should be based on knowledge of radiation oncology, the specific tumour to be treated, and available clinical results to provide the optimal benefit to the patient.
Careful treatment planning is required for optimisation to maximise the efficiency of treatment and minimise the dose to normal tissue, and depends on the treatment method and the targeted tumour. Theoretically, ion beam radiotherapy delivers radiation dose to the target volume more efficiently than conventional radiotherapy, while minimising undesired exposure of normal tissue. Nonetheless, the treatment planning must be sufficiently precise to avoid damaging the critical organs or tissues within or near the target.
Doses in the out-of-field volumes arise from the secondary neutrons and photons, particle fragments, and photons from activated materials. These undesired but unavoidable doses should be considered from the standpoint of radiological protection. Secondary neutrons are the major contributor to absorbed dose in areas distance from the treatment volume. The pencil beam scanning method can minimise this type of radiation exposure.
Imaging procedures are essential in treatment planning, similar to other modern radiotherapies, and deliver an additional small dose of radiation to the patient.
Appropriate management is required for the therapeutic equipment and the air in the treatment room which is activated. Management should always conform with regulatory requirements. The current regulations for occupational exposures in photon radiotherapy are applicable to ion beam radiotherapy with protons or carbon ions.
After treatment with ion beams, the patient will be slightly radioactive for a short time. However, radiation exposure of their family members and caretakers, as well as the public, due to this activation is negligible, and no specific protection procedures are required. Thus, the methods of radiological protection for public exposures in photon radiotherapy facilities are applicable to, and adequate for, ion beam radiotherapy facilities.
As ion beam radiotherapy requires a more complex treatment system than conventional radiotherapy, appropriate training of staff and suitable quality assurance programmes are essential to avoid possible accidental exposure of patients.
Executive Summary: Not included in this publication
