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181 Invited ESTRO-EQUAL radiotherapy dosimetry audit for high energy photon and electron beams
$59
Thursday, 19 September 2002
Symposium IMPLEMENTATION
OF N E W
DOSIMETRY
PROTO-
COLS AND QA NETWORKS
obtained in the source's reference air kerma rate depending on the method used for the chamber calibration.
178
180 Invited i m p l e m e n t a t i o n of c o d e o f p r a c t i c e b a s e d on s t a n d a r d s of
Invited
TLD audits for radiotherapy d o s i m e t r y in Central and Eastern Europe: a c t i v i t i e s o f the I A E A / W H O and National A u d i t Networks
J. Izewska IAEA Int'l Atomic Energy Agency, Dosimetry and Medical Radiation Physics Section, Wien, Austria Since 1969 the IAEA/WHO TLD postal service has verified the calibration of more than 4300 photon beams at approximately 1100 radiotherapy hospitals. In the past, only 66% of the global TLD results showed deviation between measured and stated dose within the acceptance limits of +5%. This figure has increased significantly reaching 83% in 1998-2001. However, only 75% of the hospitals who receive TLDs for the first time have results within the ±5% limits, while more than 88% of the users that have benefiied from a previous TLD audit are successful. The percentage of the results beyond the ±10% limits is twice as high for the new hospitals (8%) as for those having participated in the audits (4%). Since 1998 several countries of Central, Eastern and South-Eastern Europe have resumed regular participation in the IAEA/WHO audits. On average, their resutts do not differ significantly from the global results, however big differences exist between individual countries with the rate of successful participations r&nging from 65% to 100%. The countries with poor results suffer from an insufficient number of medical physicists, lack of proper dosimetry equipment and, typically, have obsolete radiotherapy machines. The IAEA supports its Member States in developing national programmes for TLD based QA audits in radiotherapy dosimetry and whenever possible, establishes links between the national programmes and the IAEA's Dosimetry Laboratory. Four national TLD networks operate in Central and Eastern Europe and two others are in the process of being established, The unsatisfactory status of the dosimetry for radiotherapy, as noted in the past, is gradually improving; however, the dosimetry practices in many hospitals need to be revised in order to reach the up-to-date standards. 179 Invited C a l i b r a t i o n o f p h o t o n and 13ray sources used in brachythera-
absorbed dose to water S. Vatnitskv IAEA Int'l Atomic Energy Agency, Dosimetry and Medical Radiation Physics Section, Wien, Austria The International Atomic Energy Agency (IAEA) has published recently an International Code of Practice (COP) for external beam radiotherapy dosimetry (TRS 398) based on measurement standards of absorbed close to water. Practical implementation of TRS 398 for hospital users in Member States requires testing of the procedures recommended in the CoP for different types of radiation beams and ionization chambers, and comparison of the results obtained with the existing protocols. This testing is performed within the framework of the IAEA Co-ordinated Research Project by a group of medical physicists from hospitals and various institutions around the world. The Network of the Secondary Standard Dosimetry Laboratories (SSDLs) maintained by the IAEA and World Health Organization (WHO) supports the study as the SSDLs are establishing standards of absorbed dose to water and disseminate them to users in hospitals. Different options for beam calibration in terms of absorbed dose-to-water were studied in conjunction with the comparison of absorbed dose-to-water and air kerma based CoPs for external photon, electron, proton and light ion beams. The available results and the estimated differences in dose for changing from an air kerma-based CoP to an absorbed dose-to-water CoP are discussed. Practical recommendations are given to radiotherapy hospitals switching to the absorbed dose-to-water-based CoPs for beam calibration. 181
Invited
ESTRO-EQUAL radiotherapy dosimetry audit for high energy p h o t o n and electron beams I. Ferreira 1, A. Dutreix 1, A. Bridier 2, H. Svensson 3 1ESTRO-EQUAL Measuring Laboratory, Service de Physique, Institut Gustave-Roussy, Villejuif, France 21nstitut Gustave-Roussy, Service de Physique, Villejuif, France 3University of Umea, cRadiation Physics Department, Umea, Sweden
PY H. Toelli IAEA Int'lAtomic Energy Agency, Dosimetry and Medical Radiation Physics Section, Wien, Austria The International Atomic Energy Agency (IAEA) has recently published a technical document (TECDOC-1274) on calibration of brachytherapy sources. It describes calibration techniques for all the most commonly used brachytherapy sources, including both photon and 13ray emitters. The callbration techniques on low energy photon sources and ~ ray sources have been developed in close collaboration with members of a committee of the International Commission on Radiation Units and Measurements (ICRU) who are drafting an ICRU report on this topic. In addition to the calibration techniques, TECDOC-1274 includes a comprehensive list of available detectors that can be used in the calibration procedure, It is recommended that ~ ray sources be calibrated in terms of absorbed dose to water at a specified reference distance from the source. This reference distance differs from one type of source to another and is chosen taking into consideration the low penetration of [3 rays and the requirement of the clinical application. In general, the reference distance for [3 ray sources is between 0.5 mm to 2 mm from the source, In accordance with the recommendations made by the ICRU, TECDOC1274 recommends that photon emitting brachytherapy sources should be calibrated in terms of reference air kerma rate. In such cases where Farmer type chambers are used for calibration of Ir-192 High Dose Rate (HDR) sources, it is noted that differences up to approximately 2 % may be
Since 1998 the ESTRO has set up a TLD Quality assurance programme (EQUAL), in which more than 55% of all European radiotherapy centres have participated. This TLD pbstal close assurance service addresses to photon and electron beam checks in reference and non-reference conditions and is successful with more than 1,500 beams checked. In the EQUAL programme, the accuracy in dose is checked on the beam axis in reference and non-reference conditions. Dosimetric problems in the beam calibration, errors in beam data used to the treatment planning system (TPS), have been detected by the EQUAL. The participating centres irradiate the TLD capsules sent by the EQUAL laboratory in a water phantom to an absorbed dose of 2 Gy estimated with the Treatment Planning System used in clinical routine. For the 1009 photon beams, the results show that 1.2% of checked beams are outside the tolerance level (larger than 5%) for the reference beam outputs and the percentage depth doses. For the beam output variation for open and wedged fields and for the wedge transmission factor, about 2.5% to 3% of the beams checked, show deviations >5%. The electron dose determination method applied to the EQUAL programme was developed and tested in 1999. For 574 reference beam outputs checked, only 2.6% are observed outside the tolerance level. For the other checked electron fields in non-reference conditions, up to 3-4% of checked beams show deviations larger than 5%. Considering the increasing number of conformal radiotherapy treatments, EQUAL programme was recently extended to include dose checks in photon fields shaped with Multileaf Collimators (MLC). In the MLC audit, EQUAL checks the dose in five fields with shapes and dimensions defined
$60 Thursday, 19 September 2002
by the MLC. tn three months, 43 centres have applied to take part to the MLC dose checks showing the great interest of radiotherapy centres for the new service offered by ESTRO. In the frame of ESQUIRE project, EQUAL and BRAPHYQS (BRAchytherapy PHYsics Quality assurance System) tasks have set up a system for dosimetric and geometric checks of brachytherapy procedures. The results of the EQUAL programme show the importance of a quality assurance network in Radiotherapy, especially for the non-reference conditions. Considering this point, ESTRO-EQUAL develops together with the IAEA the methodology for TLD-based Quality Audits for Radiotherapy Dosimetry in Non-reference Conditions for off-axis points with a modified TLD holder for photon beams.
Symposium
Thursday, 19 September 2002
Symposium IMPLEMENTATION
OF N E W
DOSIMETRY
PROTO-
COLS AND QA NETWORKS
obtained in the source's reference air kerma rate depending on the method used for the chamber calibration.
178
180 Invited i m p l e m e n t a t i o n of c o d e o f p r a c t i c e b a s e d on s t a n d a r d s of
Invited
TLD audits for radiotherapy d o s i m e t r y in Central and Eastern Europe: a c t i v i t i e s o f the I A E A / W H O and National A u d i t Networks
J. Izewska IAEA Int'l Atomic Energy Agency, Dosimetry and Medical Radiation Physics Section, Wien, Austria Since 1969 the IAEA/WHO TLD postal service has verified the calibration of more than 4300 photon beams at approximately 1100 radiotherapy hospitals. In the past, only 66% of the global TLD results showed deviation between measured and stated dose within the acceptance limits of +5%. This figure has increased significantly reaching 83% in 1998-2001. However, only 75% of the hospitals who receive TLDs for the first time have results within the ±5% limits, while more than 88% of the users that have benefiied from a previous TLD audit are successful. The percentage of the results beyond the ±10% limits is twice as high for the new hospitals (8%) as for those having participated in the audits (4%). Since 1998 several countries of Central, Eastern and South-Eastern Europe have resumed regular participation in the IAEA/WHO audits. On average, their resutts do not differ significantly from the global results, however big differences exist between individual countries with the rate of successful participations r&nging from 65% to 100%. The countries with poor results suffer from an insufficient number of medical physicists, lack of proper dosimetry equipment and, typically, have obsolete radiotherapy machines. The IAEA supports its Member States in developing national programmes for TLD based QA audits in radiotherapy dosimetry and whenever possible, establishes links between the national programmes and the IAEA's Dosimetry Laboratory. Four national TLD networks operate in Central and Eastern Europe and two others are in the process of being established, The unsatisfactory status of the dosimetry for radiotherapy, as noted in the past, is gradually improving; however, the dosimetry practices in many hospitals need to be revised in order to reach the up-to-date standards. 179 Invited C a l i b r a t i o n o f p h o t o n and 13ray sources used in brachythera-
absorbed dose to water S. Vatnitskv IAEA Int'l Atomic Energy Agency, Dosimetry and Medical Radiation Physics Section, Wien, Austria The International Atomic Energy Agency (IAEA) has published recently an International Code of Practice (COP) for external beam radiotherapy dosimetry (TRS 398) based on measurement standards of absorbed close to water. Practical implementation of TRS 398 for hospital users in Member States requires testing of the procedures recommended in the CoP for different types of radiation beams and ionization chambers, and comparison of the results obtained with the existing protocols. This testing is performed within the framework of the IAEA Co-ordinated Research Project by a group of medical physicists from hospitals and various institutions around the world. The Network of the Secondary Standard Dosimetry Laboratories (SSDLs) maintained by the IAEA and World Health Organization (WHO) supports the study as the SSDLs are establishing standards of absorbed dose to water and disseminate them to users in hospitals. Different options for beam calibration in terms of absorbed dose-to-water were studied in conjunction with the comparison of absorbed dose-to-water and air kerma based CoPs for external photon, electron, proton and light ion beams. The available results and the estimated differences in dose for changing from an air kerma-based CoP to an absorbed dose-to-water CoP are discussed. Practical recommendations are given to radiotherapy hospitals switching to the absorbed dose-to-water-based CoPs for beam calibration. 181
Invited
ESTRO-EQUAL radiotherapy dosimetry audit for high energy p h o t o n and electron beams I. Ferreira 1, A. Dutreix 1, A. Bridier 2, H. Svensson 3 1ESTRO-EQUAL Measuring Laboratory, Service de Physique, Institut Gustave-Roussy, Villejuif, France 21nstitut Gustave-Roussy, Service de Physique, Villejuif, France 3University of Umea, cRadiation Physics Department, Umea, Sweden
PY H. Toelli IAEA Int'lAtomic Energy Agency, Dosimetry and Medical Radiation Physics Section, Wien, Austria The International Atomic Energy Agency (IAEA) has recently published a technical document (TECDOC-1274) on calibration of brachytherapy sources. It describes calibration techniques for all the most commonly used brachytherapy sources, including both photon and 13ray emitters. The callbration techniques on low energy photon sources and ~ ray sources have been developed in close collaboration with members of a committee of the International Commission on Radiation Units and Measurements (ICRU) who are drafting an ICRU report on this topic. In addition to the calibration techniques, TECDOC-1274 includes a comprehensive list of available detectors that can be used in the calibration procedure, It is recommended that ~ ray sources be calibrated in terms of absorbed dose to water at a specified reference distance from the source. This reference distance differs from one type of source to another and is chosen taking into consideration the low penetration of [3 rays and the requirement of the clinical application. In general, the reference distance for [3 ray sources is between 0.5 mm to 2 mm from the source, In accordance with the recommendations made by the ICRU, TECDOC1274 recommends that photon emitting brachytherapy sources should be calibrated in terms of reference air kerma rate. In such cases where Farmer type chambers are used for calibration of Ir-192 High Dose Rate (HDR) sources, it is noted that differences up to approximately 2 % may be
Since 1998 the ESTRO has set up a TLD Quality assurance programme (EQUAL), in which more than 55% of all European radiotherapy centres have participated. This TLD pbstal close assurance service addresses to photon and electron beam checks in reference and non-reference conditions and is successful with more than 1,500 beams checked. In the EQUAL programme, the accuracy in dose is checked on the beam axis in reference and non-reference conditions. Dosimetric problems in the beam calibration, errors in beam data used to the treatment planning system (TPS), have been detected by the EQUAL. The participating centres irradiate the TLD capsules sent by the EQUAL laboratory in a water phantom to an absorbed dose of 2 Gy estimated with the Treatment Planning System used in clinical routine. For the 1009 photon beams, the results show that 1.2% of checked beams are outside the tolerance level (larger than 5%) for the reference beam outputs and the percentage depth doses. For the beam output variation for open and wedged fields and for the wedge transmission factor, about 2.5% to 3% of the beams checked, show deviations >5%. The electron dose determination method applied to the EQUAL programme was developed and tested in 1999. For 574 reference beam outputs checked, only 2.6% are observed outside the tolerance level. For the other checked electron fields in non-reference conditions, up to 3-4% of checked beams show deviations larger than 5%. Considering the increasing number of conformal radiotherapy treatments, EQUAL programme was recently extended to include dose checks in photon fields shaped with Multileaf Collimators (MLC). In the MLC audit, EQUAL checks the dose in five fields with shapes and dimensions defined
$60 Thursday, 19 September 2002
by the MLC. tn three months, 43 centres have applied to take part to the MLC dose checks showing the great interest of radiotherapy centres for the new service offered by ESTRO. In the frame of ESQUIRE project, EQUAL and BRAPHYQS (BRAchytherapy PHYsics Quality assurance System) tasks have set up a system for dosimetric and geometric checks of brachytherapy procedures. The results of the EQUAL programme show the importance of a quality assurance network in Radiotherapy, especially for the non-reference conditions. Considering this point, ESTRO-EQUAL develops together with the IAEA the methodology for TLD-based Quality Audits for Radiotherapy Dosimetry in Non-reference Conditions for off-axis points with a modified TLD holder for photon beams.
Symposium