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Evaluation and optimization of cardiac and left anterior descending artery DVHs in radiotherapy of left breast cancer patients
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Abstracts / Physica Medica 32 (2016) 222–250
associated with less complications and preservation of fertility is the prophylactic hypogastric artery balloon occlusion (HABO) under fluoroscopic guidance. However, concerns regarding fetal radiation exposure and the associated radiogenic risks cannot be ignored. Purpose. To provide methods and data for fetal radiation dose estimation from HABO procedures. Material and methods. Mathematical phantoms that simulate a pregnant patient at the 9th month of gestation and Monte-Carlo-Nparticle (MCNP) transport code were employed. Projection-specific normalized fetal dose (NFD) data for various beam qualities were produced through simulations of the left and right internal iliac arteries. The effects of X-ray field location relative to the fetus, field size and maternal body size on NFD were investigated. To verify MCNP results, fetal dose measurements were carried out by using a physical anthropomorphic phantom simulating pregnancy at the 3rd trimester and thermoluminescence dosimeters (TLDs). Results. NFD was found to markedly depend on tube voltage, filtration, X-ray field location and size. Presented results have taken into account the effect of maternal body size on NFD. NFD derived from TLDs showed a difference of less than 13.5% compared to those estimated by MCNP simulations. Conclusion. Methods provided allow for reliable estimation of fetal radiation burden from HABO performed at any institution. Disclosure. This study was supported by the Greek Ministry of Education and Religious Affairs, General Secretariat for Research and Technology, Operational Program ’Education and Lifelong Learning’, ARISTIA (Research project: CONCERT). http://dx.doi.org/10.1016/j.ejmp.2016.07.490
EVALUATION AND OPTIMIZATION OF CARDIAC AND LEFT ANTERIOR DESCENDING ARTERY DVHS IN RADIOTHERAPY OF LEFT BREAST CANCER PATIENTS T. Stroubinis a,*, M. Tolia b, C. Kappas a, G. Kyrgias b, K. Theodorou a a Medical Physics Department, Medical School, University of Thessaly, Biopolis, 41110 Larissa, Greece b Department of Radiotherapy, School of Health Sciences, Faculty of Medicine, University of Thessaly, Biopolis, 41110 Larissa, Greece ⇑ Corresponding author.
Introduction. The potential heart damage in left-sided breast cancer radiotherapy is well known; nevertheless the biological mechanisms are only partially understood. Radiotherapy guidelines impose dose-volume constrains for the whole heart but newer data propose that excessive dose to the Left Anterior Descending artery (LAD) endothelium may cause cardiac toxicity. Purpose. To evaluate the dose-volume data for the whole heart and LAD and performed dose distribution optimization based on a LAD dose constrain. Materials and methods. 11 left-sided breast cancer patients were retrospectively selected for this study. All patients underwent 3DCRT with 2-field tangential irradiation technique. The dose prescription was 50–60 Gy in 2 Gy/fraction. LAD was delineated for all patients and DVHs were calculated and compared. Every plan was acceptable regarding the V25 < 10% heart dose constraint of QUANTEC (IJROBR, 2010). Next, all plans were optimized based on the dose to LAD. Results. The measured Dmean was 2.9 Gy to the heart and 24.8 Gy to the LAD. Volumes below 1.5% of the heart received dose P50 Gy in 6 patients (55%). LAD Dmean in 6 cases (55%) was > 20 Gy. Plan optimization based on LAD dose reduction was possible for 5 cases where Dmax reduced 13.6-38.3% and Dmean reduced 35.1–52%. Conclusion. In left-sided breast cancer 3D-CRT, even when the DVH constrain is met for the whole heart; the LAD receives signifi-
cant higher doses. In the case that LAD dose is responsible for cardiac toxicity, new dose constrain should be added for plan optimization. http://dx.doi.org/10.1016/j.ejmp.2016.07.491
DOSIMETRIC COMPARISON OF 3D CHEMICAL DOSIMETERS FOR USE IN MODERN RT/SRS QUALITY ASSURANCE L. Petrokokkinos a,*, A. Moutsatsos a, E.P. Pappas a, I. Seimenis b, E. Pantelis a,c, P. Karaiskos a,d, P. Papagiannis a a
Physics Laboratory, Medical School, National & Kapodistrian University of Athens, Greece b Medical Physics Laboratory, Medical School, Democritus University of Thrace, Alexandroupolis, Greece c CyberKnife & TomoTherapy Department, Iatropolis Clinic, Chalandri, Athens, Greece d Gamma Knife Department, Hygeia Hospital, Marousi, Athens, Greece ⇑ Corresponding author. Introduction. QA of modern radiotherapy/radiosurgery techniques is quite challenging, requiring dosimetric systems with fine spatial resolution, water equivalence, lack of energy/dose rate dependence and, hopefully, 3D dose registering. Purpose. A comparative dosimetric assessment of two 3D dosimeters, one custom and one commercially available, towards a dosimetric system with favorable characteristics for radiotherapy/ radiosurgery QA. Materials and methods. MRI scanned VIP Polymer Gel and Optical-CT scanned PRESAGE radiochromic dosimeters were calibrated side by side. Both were subjected to the same irradiation scheme, in an extensive dose range. The dosimetric characteristics compared included dose sensitivity, dose resolution, dose rate dependence, useful dose range, minimum detectable dose and, ultimately, the uncertainty budget of the measured dose distribution. Results & conclusion. Both 3D dosimetric systems exhibited measured dose uncertainty appropriate for clinical dosimetry. The dose sensitivity of PRESAGE/OCT was higher resulting to improved dose resolution. This adds up to the increased ease of use of PRESAGE/ OCT and availability of a dedicated optical scanner. However the increased noise in comparison to Polymer Gel/MRI and the occurrence of concentric ring and significant edge artifacts render this favorable characteristics debatable. Moreover indications of dose rate and energy dependence due to higher density have to be further investigated in order to end up with a dosimetric system to be used in the verification of complex radiotherapy/radiosurgery treatment plans. Disclosure. Research conducted with financing by ‘‘IKY Postdoc Fellowships of Excellence in Greece – Siemens Programme” in the framework of the Hellenic Republic – Siemens Settlement Agreement. http://dx.doi.org/10.1016/j.ejmp.2016.07.492
COMPARISON OF TWO FILM DOSIMETRY METHODS FOR DOSE VERIFICATION IN STEREOTACTIC RADIOSURGERY APPLICATIONS G. Antorkas a,*, E. Zoros a, E. Pantelis a, G. Kollias b, E. Georgiou a, P. Karaiskos a,b a
Medical Physics Laboratory, Medical School, National Kapodistrian University of Athens, 75 Mikras Asias, 11527 Athens, Greece b Gamma Knife Center, Hygeia Hospital, Er. Stavrou 4 and Kifisias, 151 23 Athens, Greece ⇑ Corresponding author. Introduction. The increased demand for quality assurance in stereotactic radiosurgery (SRS) applications using small fields with
Abstracts / Physica Medica 32 (2016) 222–250
associated with less complications and preservation of fertility is the prophylactic hypogastric artery balloon occlusion (HABO) under fluoroscopic guidance. However, concerns regarding fetal radiation exposure and the associated radiogenic risks cannot be ignored. Purpose. To provide methods and data for fetal radiation dose estimation from HABO procedures. Material and methods. Mathematical phantoms that simulate a pregnant patient at the 9th month of gestation and Monte-Carlo-Nparticle (MCNP) transport code were employed. Projection-specific normalized fetal dose (NFD) data for various beam qualities were produced through simulations of the left and right internal iliac arteries. The effects of X-ray field location relative to the fetus, field size and maternal body size on NFD were investigated. To verify MCNP results, fetal dose measurements were carried out by using a physical anthropomorphic phantom simulating pregnancy at the 3rd trimester and thermoluminescence dosimeters (TLDs). Results. NFD was found to markedly depend on tube voltage, filtration, X-ray field location and size. Presented results have taken into account the effect of maternal body size on NFD. NFD derived from TLDs showed a difference of less than 13.5% compared to those estimated by MCNP simulations. Conclusion. Methods provided allow for reliable estimation of fetal radiation burden from HABO performed at any institution. Disclosure. This study was supported by the Greek Ministry of Education and Religious Affairs, General Secretariat for Research and Technology, Operational Program ’Education and Lifelong Learning’, ARISTIA (Research project: CONCERT). http://dx.doi.org/10.1016/j.ejmp.2016.07.490
EVALUATION AND OPTIMIZATION OF CARDIAC AND LEFT ANTERIOR DESCENDING ARTERY DVHS IN RADIOTHERAPY OF LEFT BREAST CANCER PATIENTS T. Stroubinis a,*, M. Tolia b, C. Kappas a, G. Kyrgias b, K. Theodorou a a Medical Physics Department, Medical School, University of Thessaly, Biopolis, 41110 Larissa, Greece b Department of Radiotherapy, School of Health Sciences, Faculty of Medicine, University of Thessaly, Biopolis, 41110 Larissa, Greece ⇑ Corresponding author.
Introduction. The potential heart damage in left-sided breast cancer radiotherapy is well known; nevertheless the biological mechanisms are only partially understood. Radiotherapy guidelines impose dose-volume constrains for the whole heart but newer data propose that excessive dose to the Left Anterior Descending artery (LAD) endothelium may cause cardiac toxicity. Purpose. To evaluate the dose-volume data for the whole heart and LAD and performed dose distribution optimization based on a LAD dose constrain. Materials and methods. 11 left-sided breast cancer patients were retrospectively selected for this study. All patients underwent 3DCRT with 2-field tangential irradiation technique. The dose prescription was 50–60 Gy in 2 Gy/fraction. LAD was delineated for all patients and DVHs were calculated and compared. Every plan was acceptable regarding the V25 < 10% heart dose constraint of QUANTEC (IJROBR, 2010). Next, all plans were optimized based on the dose to LAD. Results. The measured Dmean was 2.9 Gy to the heart and 24.8 Gy to the LAD. Volumes below 1.5% of the heart received dose P50 Gy in 6 patients (55%). LAD Dmean in 6 cases (55%) was > 20 Gy. Plan optimization based on LAD dose reduction was possible for 5 cases where Dmax reduced 13.6-38.3% and Dmean reduced 35.1–52%. Conclusion. In left-sided breast cancer 3D-CRT, even when the DVH constrain is met for the whole heart; the LAD receives signifi-
cant higher doses. In the case that LAD dose is responsible for cardiac toxicity, new dose constrain should be added for plan optimization. http://dx.doi.org/10.1016/j.ejmp.2016.07.491
DOSIMETRIC COMPARISON OF 3D CHEMICAL DOSIMETERS FOR USE IN MODERN RT/SRS QUALITY ASSURANCE L. Petrokokkinos a,*, A. Moutsatsos a, E.P. Pappas a, I. Seimenis b, E. Pantelis a,c, P. Karaiskos a,d, P. Papagiannis a a
Physics Laboratory, Medical School, National & Kapodistrian University of Athens, Greece b Medical Physics Laboratory, Medical School, Democritus University of Thrace, Alexandroupolis, Greece c CyberKnife & TomoTherapy Department, Iatropolis Clinic, Chalandri, Athens, Greece d Gamma Knife Department, Hygeia Hospital, Marousi, Athens, Greece ⇑ Corresponding author. Introduction. QA of modern radiotherapy/radiosurgery techniques is quite challenging, requiring dosimetric systems with fine spatial resolution, water equivalence, lack of energy/dose rate dependence and, hopefully, 3D dose registering. Purpose. A comparative dosimetric assessment of two 3D dosimeters, one custom and one commercially available, towards a dosimetric system with favorable characteristics for radiotherapy/ radiosurgery QA. Materials and methods. MRI scanned VIP Polymer Gel and Optical-CT scanned PRESAGE radiochromic dosimeters were calibrated side by side. Both were subjected to the same irradiation scheme, in an extensive dose range. The dosimetric characteristics compared included dose sensitivity, dose resolution, dose rate dependence, useful dose range, minimum detectable dose and, ultimately, the uncertainty budget of the measured dose distribution. Results & conclusion. Both 3D dosimetric systems exhibited measured dose uncertainty appropriate for clinical dosimetry. The dose sensitivity of PRESAGE/OCT was higher resulting to improved dose resolution. This adds up to the increased ease of use of PRESAGE/ OCT and availability of a dedicated optical scanner. However the increased noise in comparison to Polymer Gel/MRI and the occurrence of concentric ring and significant edge artifacts render this favorable characteristics debatable. Moreover indications of dose rate and energy dependence due to higher density have to be further investigated in order to end up with a dosimetric system to be used in the verification of complex radiotherapy/radiosurgery treatment plans. Disclosure. Research conducted with financing by ‘‘IKY Postdoc Fellowships of Excellence in Greece – Siemens Programme” in the framework of the Hellenic Republic – Siemens Settlement Agreement. http://dx.doi.org/10.1016/j.ejmp.2016.07.492
COMPARISON OF TWO FILM DOSIMETRY METHODS FOR DOSE VERIFICATION IN STEREOTACTIC RADIOSURGERY APPLICATIONS G. Antorkas a,*, E. Zoros a, E. Pantelis a, G. Kollias b, E. Georgiou a, P. Karaiskos a,b a
Medical Physics Laboratory, Medical School, National Kapodistrian University of Athens, 75 Mikras Asias, 11527 Athens, Greece b Gamma Knife Center, Hygeia Hospital, Er. Stavrou 4 and Kifisias, 151 23 Athens, Greece ⇑ Corresponding author. Introduction. The increased demand for quality assurance in stereotactic radiosurgery (SRS) applications using small fields with