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Beam delivery check and in-vivo dosimetry during breast radiotherapy treatment
e66
Abstracts/Physica Medica 32 (2016) e1–e70
Conclusions: The reported results demonstrate that DIAPIX is a suitable detector for dosimetric applications. Future plans foresee a new detector covering a larger area of 2.5 × 7.5 cm2 and a new prototype to be employed as a transmission detector, mounted on the LINAC gantry. This work has been supported by the experiments INFN CSN5 DIAPIX and IRPT/MIUR. http://dx.doi.org/10.1016/j.ejmp.2016.01.225
A.222 MULTICENTRE STUDY OF RELATIVE DOSIMETRY MEASUREMENTS USING RAZOR NEW SILICON DIODE C. Talamonti *,a, M.D. Falco b, L. Barone c, E. Di Castro d, C. Iervolino e, S. Luxardo f, G. Pastore g, M.C. Pressello h, A. Vaiano i, P. Mancosu j. a Università degli studi di Firenze, Azienda Ospedaliera Universitaria Careggi, Firenze, Italy; b Ospedale SS. Annunziata, Università di Chieti, Chieti, Italy; c A.R.N.A.S. Garibaldi, Catania, Italy; d Policlinico Umberto I, Roma, Italy; e A.O.S. G. Moscati, Avellino, Italy; f Ospedale Asl 1 Massa e Carrara, Carrara, Italy; g A.S.L., Lecce, Italy; h AO San Camillo Forlanini, Roma, Italy; i A.S.L 3, Pistoia, Italy; j Humanitas Milano, Milano, Italy Introduction: In this study an Italian multicentre evaluation of small field output factors (OFs) and field penumbras of different linear accelerator manufacturers using a silicon diode of new generation is presented. The main goal is to provide indications, for each linac model, on small field dosimetry measurements that could be used by those centers which intend to implement new and performing treatment techniques. Materials and methods: Among 34 radiotherapy centres which took part in the project, different LINACs were available: 2 Siemens, 13 Elekta Synergy Agility and BM, 12 Varian CLINAC and 7 Varian True Beam. The same protocol was used by each centre. A flat ionization chamber was fixed on the gantry as reference and the IBA unshielded silicon diode RAZOR was used. The diode was positioned at the isocentre (d = 10 cm SSD 90 cm) in water phantom. In-cross line beam profiles were used to calculate the effective field size (FS_E), defined as (A*B)^0.5.OFs as a function of FS_E, and nominal field size (FS), ranging from 0.6 to 5 cm, was calculated and normalized to the 3 cm FS. Results: Penumbra measurements were in agreement with each other for each FS and accelerator model. The mean values of OFs of all LINACs were found to be in good agreement within a few per mille up to 1 cm FS. In the smallest fields, the agreement was within few per cent and for FS = 0.6 cm was about 10%. For FS below 1 cm, a different trend is evident depending on different accelerator manufacturer and different models from the same vendor. Considering the FS_E, the agreement increased especially for Varian where a st.dev of 8% was found for FS = 0.6 cm. This was mainly due to FS which differed from FS_E up to 15%. Conclusions: The good agreement among data from different accelerators indicate that RAZOR can be used with good accuracy to perform measurements in small fields, and that our reported data can be used by other centres as indicative values, especially when suitable detectors are not available. http://dx.doi.org/10.1016/j.ejmp.2016.01.226
A.223 BEAM DELIVERY CHECK AND IN-VIVO DOSIMETRY DURING BREAST RADIOTHERAPY TREATMENT C. Talamonti *,a, L. Marrazzo b, C. Arilli b, C. Galeotti b, M. Casati b, S. Calusi a, C. Domizi a , A. Fidanzio c , I. Meattini b , S. Scoccianti b , P. Bonomo b , A. Piermattei c, S. Pallotta a. a Università degli Studi di Firenze, Azienda Ospedaliera Universitaria Careggi, Firenze, Italy; b Azienda Ospedaliera Universitaria Careggi, Firenze, Italy; c Università Cattolica del Sacro Cuore, Roma, Italy Introduction: The goal of this study is to verify the delivery of the prescribed dose during radiotherapy treatment using the integral quality monitoring (IQM) device (iRT Systems GmbH, Koblenz, Germany) and the portal imaging together with the software SoftDiso (Best Medical Italy Srl) for in-vivo measurements. Furthermore the ability in detecting positional and delivery errors intentionally introduced in breast treatments was studied.
Materials and methods: IQM consists of a large area ionization chamber, with a gradient in the electrode plate separation, to be mounted on the accelerator gantry. It is an independent on-line beam monitoring system able to verify the accuracy and consistency of beam delivery during each treatment session. The software SoftDiso permits to evaluate the dose at the isocenter on the basis of portal images acquired during the delivery and it allows to compare dose distributions at the isocenter plane of different acquisitions. 3DCRT and IMRT plans were calculated on a phantom and small delivery errors were induced to simulate deviation on the treatment plans due to delivery problems and/or to a wrong positioning of the phantom. The phantom used was the Anderson Rando modified to mimic a female torso by adding two silicone gel breast implants. Results: IQM can detect, with a precision of per mille, errors due to small changes in MU and field dimensions, while SoftDiso detects discrepancy on dose reconstructed with a precision of 5%. The combined use of the two systems allows to identify the source of error (phantom misalignment or changes in the beam). Conclusions: The concurrent use of the two tested systems allow for a check of the correct functioning of all components in the radiotherapy chain, including the treatment planning, the delivery system and the patient positioning and thus play an important role in meeting the needs of modern and upcoming radiotherapy QA. http://dx.doi.org/10.1016/j.ejmp.2016.01.227
A.224 QUALITY ASSURANCE TOOLS FOR RISK MANAGEMENT S. Tomatis *, V. Palumbo, G. Maggi, A. Gaudino, G. Reggiori, F. Lobefalo, A. Stravato, F. Zucconi, L. Paganini, G.R. D’Agostino, P. Navarria, P. Mancosu, M. Scorsetti. Humanitas Research Hospital, Rozzano, Italy Purpose: To develop proper quality indices to increase the control of the workflow in radiotherapy by a quantitative analysis of data extracted from the R&V system database of our radiotherapy department. Materials and methods: Several parameters related to delivery modality, use of flattened (FF) or unflattened (FFF) beams, pretreatment imaging and other planning details were extracted for each patient by proper SQL querying of the database. These features were analyzed to derive indicators for radiotherapy treatment quality and workflow monitoring. Impact of hypofractionation was quantified by considering the incidence of fraction doses up to 3 Gy against higher doses. The application of IGRT was measured to quantify the quality of patient positioning. For a specific hypofractionated protocol of breast treatment (48 Gy/15 fr), an indicator was developed to verify that the total number of effective fractions does not exceed the number of the planned ones. Results: Data show an increasing trend in the number of new patients per year (2500 in 2014). The fraction of VMAT treatments increased from 26.2% in 2010 to about 85% in 2014. Since 2010, median treatment beam on time (BOT) for fraction doses above 12 Gy decreased down to less than 2 minutes in 2014 as for every treatment. In the last 5 years, use of hypofractionation has grown from 19.2% to about 48.3% of treatments. In 2014 IGRT was applied to more than 80% of all treatments and always performed in the first fraction for all patients. Evaluation of excess time involved in the hypofractionated breast protocol was found to be always below 5 days. Conclusion: The introduction of new protocols coupled to a growing complexity of treatments led to higher doses per fraction delivered in acceptable times for a better patient overall comfort. The evaluation of IGRT frequency and excess therapy time using our indicators was found to be suitable to obtain high quality standards in essential parts of the radiotherapy workflow in our center. http://dx.doi.org/10.1016/j.ejmp.2016.01.228
Abstracts/Physica Medica 32 (2016) e1–e70
Conclusions: The reported results demonstrate that DIAPIX is a suitable detector for dosimetric applications. Future plans foresee a new detector covering a larger area of 2.5 × 7.5 cm2 and a new prototype to be employed as a transmission detector, mounted on the LINAC gantry. This work has been supported by the experiments INFN CSN5 DIAPIX and IRPT/MIUR. http://dx.doi.org/10.1016/j.ejmp.2016.01.225
A.222 MULTICENTRE STUDY OF RELATIVE DOSIMETRY MEASUREMENTS USING RAZOR NEW SILICON DIODE C. Talamonti *,a, M.D. Falco b, L. Barone c, E. Di Castro d, C. Iervolino e, S. Luxardo f, G. Pastore g, M.C. Pressello h, A. Vaiano i, P. Mancosu j. a Università degli studi di Firenze, Azienda Ospedaliera Universitaria Careggi, Firenze, Italy; b Ospedale SS. Annunziata, Università di Chieti, Chieti, Italy; c A.R.N.A.S. Garibaldi, Catania, Italy; d Policlinico Umberto I, Roma, Italy; e A.O.S. G. Moscati, Avellino, Italy; f Ospedale Asl 1 Massa e Carrara, Carrara, Italy; g A.S.L., Lecce, Italy; h AO San Camillo Forlanini, Roma, Italy; i A.S.L 3, Pistoia, Italy; j Humanitas Milano, Milano, Italy Introduction: In this study an Italian multicentre evaluation of small field output factors (OFs) and field penumbras of different linear accelerator manufacturers using a silicon diode of new generation is presented. The main goal is to provide indications, for each linac model, on small field dosimetry measurements that could be used by those centers which intend to implement new and performing treatment techniques. Materials and methods: Among 34 radiotherapy centres which took part in the project, different LINACs were available: 2 Siemens, 13 Elekta Synergy Agility and BM, 12 Varian CLINAC and 7 Varian True Beam. The same protocol was used by each centre. A flat ionization chamber was fixed on the gantry as reference and the IBA unshielded silicon diode RAZOR was used. The diode was positioned at the isocentre (d = 10 cm SSD 90 cm) in water phantom. In-cross line beam profiles were used to calculate the effective field size (FS_E), defined as (A*B)^0.5.OFs as a function of FS_E, and nominal field size (FS), ranging from 0.6 to 5 cm, was calculated and normalized to the 3 cm FS. Results: Penumbra measurements were in agreement with each other for each FS and accelerator model. The mean values of OFs of all LINACs were found to be in good agreement within a few per mille up to 1 cm FS. In the smallest fields, the agreement was within few per cent and for FS = 0.6 cm was about 10%. For FS below 1 cm, a different trend is evident depending on different accelerator manufacturer and different models from the same vendor. Considering the FS_E, the agreement increased especially for Varian where a st.dev of 8% was found for FS = 0.6 cm. This was mainly due to FS which differed from FS_E up to 15%. Conclusions: The good agreement among data from different accelerators indicate that RAZOR can be used with good accuracy to perform measurements in small fields, and that our reported data can be used by other centres as indicative values, especially when suitable detectors are not available. http://dx.doi.org/10.1016/j.ejmp.2016.01.226
A.223 BEAM DELIVERY CHECK AND IN-VIVO DOSIMETRY DURING BREAST RADIOTHERAPY TREATMENT C. Talamonti *,a, L. Marrazzo b, C. Arilli b, C. Galeotti b, M. Casati b, S. Calusi a, C. Domizi a , A. Fidanzio c , I. Meattini b , S. Scoccianti b , P. Bonomo b , A. Piermattei c, S. Pallotta a. a Università degli Studi di Firenze, Azienda Ospedaliera Universitaria Careggi, Firenze, Italy; b Azienda Ospedaliera Universitaria Careggi, Firenze, Italy; c Università Cattolica del Sacro Cuore, Roma, Italy Introduction: The goal of this study is to verify the delivery of the prescribed dose during radiotherapy treatment using the integral quality monitoring (IQM) device (iRT Systems GmbH, Koblenz, Germany) and the portal imaging together with the software SoftDiso (Best Medical Italy Srl) for in-vivo measurements. Furthermore the ability in detecting positional and delivery errors intentionally introduced in breast treatments was studied.
Materials and methods: IQM consists of a large area ionization chamber, with a gradient in the electrode plate separation, to be mounted on the accelerator gantry. It is an independent on-line beam monitoring system able to verify the accuracy and consistency of beam delivery during each treatment session. The software SoftDiso permits to evaluate the dose at the isocenter on the basis of portal images acquired during the delivery and it allows to compare dose distributions at the isocenter plane of different acquisitions. 3DCRT and IMRT plans were calculated on a phantom and small delivery errors were induced to simulate deviation on the treatment plans due to delivery problems and/or to a wrong positioning of the phantom. The phantom used was the Anderson Rando modified to mimic a female torso by adding two silicone gel breast implants. Results: IQM can detect, with a precision of per mille, errors due to small changes in MU and field dimensions, while SoftDiso detects discrepancy on dose reconstructed with a precision of 5%. The combined use of the two systems allows to identify the source of error (phantom misalignment or changes in the beam). Conclusions: The concurrent use of the two tested systems allow for a check of the correct functioning of all components in the radiotherapy chain, including the treatment planning, the delivery system and the patient positioning and thus play an important role in meeting the needs of modern and upcoming radiotherapy QA. http://dx.doi.org/10.1016/j.ejmp.2016.01.227
A.224 QUALITY ASSURANCE TOOLS FOR RISK MANAGEMENT S. Tomatis *, V. Palumbo, G. Maggi, A. Gaudino, G. Reggiori, F. Lobefalo, A. Stravato, F. Zucconi, L. Paganini, G.R. D’Agostino, P. Navarria, P. Mancosu, M. Scorsetti. Humanitas Research Hospital, Rozzano, Italy Purpose: To develop proper quality indices to increase the control of the workflow in radiotherapy by a quantitative analysis of data extracted from the R&V system database of our radiotherapy department. Materials and methods: Several parameters related to delivery modality, use of flattened (FF) or unflattened (FFF) beams, pretreatment imaging and other planning details were extracted for each patient by proper SQL querying of the database. These features were analyzed to derive indicators for radiotherapy treatment quality and workflow monitoring. Impact of hypofractionation was quantified by considering the incidence of fraction doses up to 3 Gy against higher doses. The application of IGRT was measured to quantify the quality of patient positioning. For a specific hypofractionated protocol of breast treatment (48 Gy/15 fr), an indicator was developed to verify that the total number of effective fractions does not exceed the number of the planned ones. Results: Data show an increasing trend in the number of new patients per year (2500 in 2014). The fraction of VMAT treatments increased from 26.2% in 2010 to about 85% in 2014. Since 2010, median treatment beam on time (BOT) for fraction doses above 12 Gy decreased down to less than 2 minutes in 2014 as for every treatment. In the last 5 years, use of hypofractionation has grown from 19.2% to about 48.3% of treatments. In 2014 IGRT was applied to more than 80% of all treatments and always performed in the first fraction for all patients. Evaluation of excess time involved in the hypofractionated breast protocol was found to be always below 5 days. Conclusion: The introduction of new protocols coupled to a growing complexity of treatments led to higher doses per fraction delivered in acceptable times for a better patient overall comfort. The evaluation of IGRT frequency and excess therapy time using our indicators was found to be suitable to obtain high quality standards in essential parts of the radiotherapy workflow in our center. http://dx.doi.org/10.1016/j.ejmp.2016.01.228