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[P171] Quality control measurements for head and neck cancer patients with SHANE Phantom
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Abstracts / Physica Medica 52 (2018) 99–187
measured using thermoluminescence dosimeters. The phantoms were subject to three fractions (1,8 Gy each), with and without 1 mm lead shielding of the torso. The measured doses were used to calculate lifetime attributable risks for cancer incidence, for the total treatment dose of 54 Gy, in accordance with the BEIR VII report.1 Results. Applying lead shielding yielded dose reductions of 8–18% for the thyroid and 12–18% for the breast. The results were statistically significant (Student’s t-test, significance level p < 0,05) in all cases except for the thyroid of the 5-year phantom for the large PTV. The dose reductions caused by the shielding translated into reduced secondary cancer risks. Without shielding, the largest risks were calculated for the 1-year phantom and large PTV, since the risk increases with decreasing age and increasing dose. By applying shielding, this risk was reduced from 1,09% to 0,90% for the thyroid, and from 1,05% to 0,92% for the breast. Conclusions. Lead shielding of the phantoms resulted in a systematic decrease in the measured doses to the thyroid and breast, reducing the lifetime attributable risks for cancer incidence. The results hereby suggest that a 1 mm thick lead rubber blanket might be a clinically feasible solution for reducing the risk of secondary cancer in paediatric radiotherapy patients. https://doi.org/10.1016/j.ejmp.2018.06.469
[P170] Influence of detector selection for VMAT patient QA on a gamma analysis result Attila Sarvari *, Primoz Peterlin, Tatjana Pernek Institute of Oncology Ljubljana, Radiotherapy, Ljubljana, Slovenia Corresponding author.
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Purpose. The aim of this study was to investigate how the selection of detector for VMAT patient QA influences on a gamma analysis result. Methods. Twenty RapidArc (10 prostate, 10 head&neck) plans were made in an Eclipse (ver. 10.0, AAA algorithm) treatment planning system (Varian Medical Systems) were measured with Delta 4PT, Delta 4+ (ScandiDos) and MatriXX MultiCube (IBA Dosimetry) detectors. Most prostate plans consisted of 2 full arc fields while some of the head&neck plans had only 2 half arc fields. The measurements were performed on a Varian Novalis Tx linear accelerator with use of a 6 MV energy. With one device we have measured the entire number of plans on a single day in order to avoid the error of the daily dose output variation and the daily phantom setup error. Before the start of the RA plan measurements we performed a warm up and measured the daily correction factor for the linear accelerator output as well as the temperature correction. Based on the measurements we have applied a phantom position correction to eliminate the error caused by alignment of the phantom to laser system. Gamma evaluations using the same global settings (DTA 3 mm, dose difference 3%, gamma 95% < 1, dose threshold 20%) were performed. Results. In total 41 fields were measured with one device. The biggest difference between the results of gamma analysis for different detectors was detected in a dose difference parameter. The Delta 4 + and Delta 4PT had an average difference between the dose difference parameter 2%, while the average differences regarding to MatriXX MultiCube were 7.5% and 9.5%. Conclusions. Based on the results we can conclude that both Delta4 systems are more suitable for VMAT patient QA than the MatriXX 1 National Research Council. Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2. National Academies Press 2006.
MultiCube. The MatriXX is designed for verification where the device is perpendicular to radiation field. Nevertheless the decision of the appropriate equipment to be used for the patient QA is upon the medical physicist. https://doi.org/10.1016/j.ejmp.2018.06.470
[P171] Quality control measurements for head and neck cancer patients with SHANE Phantom Barbara Melles-Bencsik a,*, Dalma Mihály a, Eniko} Tolvaj a, Zoltán Takácsi Nagy a, Tibor Major a, Csaba Polgár b, Csilla Pesznyák c a
National Institute of Oncology, Radiotherapy Centre, Budapest, Hungary b National Institute of Oncology, Semmelweis University, Radiotherapy Centre, Budapest, Hungary c National Institute of Oncology, Budapest University of Technology and Economics, Centre of Radiotherapy, Budapest, Hungary ⇑ Corresponding author. Purpose. To investigate irradiation techniques for simultaneous integrated boost (SIB) treatment of nasopharyngeal cancer (NPC) case in terms of organs at risk (OAR) toxicity and patient specific quality control (QC). This study is a part of an end-to-end audit programme for dose delivery using intensity modulated radiation therapy (IMRT). Methods. CIRS SHANE Phantom was used to create four different treatment plans for a NPC patient. SIB schedule prescribes 54 Gy, 60 Gy and 70 Gy in 30 fractions for elective nodes (both sides), involved nodes (right side) and primary nasopharynx respectively, using 1, 2 or 3 arcs RapidArc (RA) or 7 field Sliding Window (SW) techniques. Patient specific quality control measurements were performed using EPID. Varian Portal Dosimetry was used with local gamma analysis using 2%/2 mm and 3%/3 mm criteria with 10% threshold. Results. All plans met the criteria of dose to OARs: D2% of the spinal cord and the brainstem on average were 35 Gy and 35.5 Gy; mean dose of the left parotid on average was 22.9 Gy. Patient specific QC was performed without any interruption. MUs for 1, 2, 3 arcs and 7 field SW were 602, 706, 696 and 2447, respectively. Gamma analysis on EPID images gave 96.2%, 96.2%, 96.7%, 82.6% and 98,8%, 98.9%, 99.3%, 92,1% passing rate on average for 2%/ 2 mm and 3%/ 3 mm criteria, respectively. Conclusions. All treatment techniques are suitable for NPC irradiation with SIB in terms of OAR toxicity although RA with 2 or 3 arcs are more preferable in terms of number of MUs. https://doi.org/10.1016/j.ejmp.2018.06.471
[P172] Establishment and transfer of a primary dosimetry standard for breast cancer IORT using the INTRABEAM(R) system Abdullah Abudra’a a, Jean Gouriou a, Christel Stien a, Johann Plagnard a, Marc Denoziere a, Ramona Itti b, Bruno Chauvenet a, Isabelle Aubineau-Laniece a,* a Cea, List, Laboratoire National Henri Becquerel (Lne-Lnhb), Cea-Saclay, Drt/List/Dm2i, Gif-Sur-Yvette Cedex, France b Service de Cancérologie-Radiothérapie, Hôpital Saint-Louis, Service de Cancérologie-Radiothérapie, Paris, France ⇑ Corresponding author.
Purpose. Intraoperative radiation therapy (IORT) using low-energy X-rays (650 keV) delivers a concentrated dose by placing, during surgery, a miniaturized X-ray tube in contact with the treated tumor
Abstracts / Physica Medica 52 (2018) 99–187
measured using thermoluminescence dosimeters. The phantoms were subject to three fractions (1,8 Gy each), with and without 1 mm lead shielding of the torso. The measured doses were used to calculate lifetime attributable risks for cancer incidence, for the total treatment dose of 54 Gy, in accordance with the BEIR VII report.1 Results. Applying lead shielding yielded dose reductions of 8–18% for the thyroid and 12–18% for the breast. The results were statistically significant (Student’s t-test, significance level p < 0,05) in all cases except for the thyroid of the 5-year phantom for the large PTV. The dose reductions caused by the shielding translated into reduced secondary cancer risks. Without shielding, the largest risks were calculated for the 1-year phantom and large PTV, since the risk increases with decreasing age and increasing dose. By applying shielding, this risk was reduced from 1,09% to 0,90% for the thyroid, and from 1,05% to 0,92% for the breast. Conclusions. Lead shielding of the phantoms resulted in a systematic decrease in the measured doses to the thyroid and breast, reducing the lifetime attributable risks for cancer incidence. The results hereby suggest that a 1 mm thick lead rubber blanket might be a clinically feasible solution for reducing the risk of secondary cancer in paediatric radiotherapy patients. https://doi.org/10.1016/j.ejmp.2018.06.469
[P170] Influence of detector selection for VMAT patient QA on a gamma analysis result Attila Sarvari *, Primoz Peterlin, Tatjana Pernek Institute of Oncology Ljubljana, Radiotherapy, Ljubljana, Slovenia Corresponding author.
⇑
Purpose. The aim of this study was to investigate how the selection of detector for VMAT patient QA influences on a gamma analysis result. Methods. Twenty RapidArc (10 prostate, 10 head&neck) plans were made in an Eclipse (ver. 10.0, AAA algorithm) treatment planning system (Varian Medical Systems) were measured with Delta 4PT, Delta 4+ (ScandiDos) and MatriXX MultiCube (IBA Dosimetry) detectors. Most prostate plans consisted of 2 full arc fields while some of the head&neck plans had only 2 half arc fields. The measurements were performed on a Varian Novalis Tx linear accelerator with use of a 6 MV energy. With one device we have measured the entire number of plans on a single day in order to avoid the error of the daily dose output variation and the daily phantom setup error. Before the start of the RA plan measurements we performed a warm up and measured the daily correction factor for the linear accelerator output as well as the temperature correction. Based on the measurements we have applied a phantom position correction to eliminate the error caused by alignment of the phantom to laser system. Gamma evaluations using the same global settings (DTA 3 mm, dose difference 3%, gamma 95% < 1, dose threshold 20%) were performed. Results. In total 41 fields were measured with one device. The biggest difference between the results of gamma analysis for different detectors was detected in a dose difference parameter. The Delta 4 + and Delta 4PT had an average difference between the dose difference parameter 2%, while the average differences regarding to MatriXX MultiCube were 7.5% and 9.5%. Conclusions. Based on the results we can conclude that both Delta4 systems are more suitable for VMAT patient QA than the MatriXX 1 National Research Council. Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2. National Academies Press 2006.
MultiCube. The MatriXX is designed for verification where the device is perpendicular to radiation field. Nevertheless the decision of the appropriate equipment to be used for the patient QA is upon the medical physicist. https://doi.org/10.1016/j.ejmp.2018.06.470
[P171] Quality control measurements for head and neck cancer patients with SHANE Phantom Barbara Melles-Bencsik a,*, Dalma Mihály a, Eniko} Tolvaj a, Zoltán Takácsi Nagy a, Tibor Major a, Csaba Polgár b, Csilla Pesznyák c a
National Institute of Oncology, Radiotherapy Centre, Budapest, Hungary b National Institute of Oncology, Semmelweis University, Radiotherapy Centre, Budapest, Hungary c National Institute of Oncology, Budapest University of Technology and Economics, Centre of Radiotherapy, Budapest, Hungary ⇑ Corresponding author. Purpose. To investigate irradiation techniques for simultaneous integrated boost (SIB) treatment of nasopharyngeal cancer (NPC) case in terms of organs at risk (OAR) toxicity and patient specific quality control (QC). This study is a part of an end-to-end audit programme for dose delivery using intensity modulated radiation therapy (IMRT). Methods. CIRS SHANE Phantom was used to create four different treatment plans for a NPC patient. SIB schedule prescribes 54 Gy, 60 Gy and 70 Gy in 30 fractions for elective nodes (both sides), involved nodes (right side) and primary nasopharynx respectively, using 1, 2 or 3 arcs RapidArc (RA) or 7 field Sliding Window (SW) techniques. Patient specific quality control measurements were performed using EPID. Varian Portal Dosimetry was used with local gamma analysis using 2%/2 mm and 3%/3 mm criteria with 10% threshold. Results. All plans met the criteria of dose to OARs: D2% of the spinal cord and the brainstem on average were 35 Gy and 35.5 Gy; mean dose of the left parotid on average was 22.9 Gy. Patient specific QC was performed without any interruption. MUs for 1, 2, 3 arcs and 7 field SW were 602, 706, 696 and 2447, respectively. Gamma analysis on EPID images gave 96.2%, 96.2%, 96.7%, 82.6% and 98,8%, 98.9%, 99.3%, 92,1% passing rate on average for 2%/ 2 mm and 3%/ 3 mm criteria, respectively. Conclusions. All treatment techniques are suitable for NPC irradiation with SIB in terms of OAR toxicity although RA with 2 or 3 arcs are more preferable in terms of number of MUs. https://doi.org/10.1016/j.ejmp.2018.06.471
[P172] Establishment and transfer of a primary dosimetry standard for breast cancer IORT using the INTRABEAM(R) system Abdullah Abudra’a a, Jean Gouriou a, Christel Stien a, Johann Plagnard a, Marc Denoziere a, Ramona Itti b, Bruno Chauvenet a, Isabelle Aubineau-Laniece a,* a Cea, List, Laboratoire National Henri Becquerel (Lne-Lnhb), Cea-Saclay, Drt/List/Dm2i, Gif-Sur-Yvette Cedex, France b Service de Cancérologie-Radiothérapie, Hôpital Saint-Louis, Service de Cancérologie-Radiothérapie, Paris, France ⇑ Corresponding author.
Purpose. Intraoperative radiation therapy (IORT) using low-energy X-rays (650 keV) delivers a concentrated dose by placing, during surgery, a miniaturized X-ray tube in contact with the treated tumor