- Email: [email protected]
PO-0947: Image-guided brachytherapy with 106Ru eye plaques for uveal melanomas using post implantation MRI
S524 ESTRO 36 _______________________________________________________________________________________________
cylinder applicator (Figure 1b) with 5 catheters. Interdwell distances of 2 and 5 mm were employed and the experiments performed for source activities between 5 and 10 Ci. The EPID response is proportional to the source activity so it is possible to obtain the activity by sending the source to pre-defined dwell position.
Results 3D Cartesian coordinates can be obtained with 0.2 mm accuracy using a single EPID panel. The panel can clearly identify dwell positions 2 mm apart even with the catheter at 24 cm distance (Figure 1c) from the panel. Absolute coordinates can be obtained by adding reference points (representing the corners of the water phantom) in the treatment plan that can be related with the position of the water phantom over the panel during the experiments. An in-house developed software compares all dwell positions/times against the treatment plan. The software can also monitor the sequence of the treatment identifying the afterloader channel connected to each catheter. Therefore, it is possible to detect catheter misplacements, swapped transfer tube connections, wrong dwell times and/or positions and also verify the source activity. Conclusion This work describes an experimental system that can be implemented in the clinic providing experimental pretreatment verification that is not currently available. This method provides several advantages when compared against other dosimeters such as films or MOSFETs as it combines a 2D dosimeter, which has an online response. Our system can detect several problems that would be unnoticed during the treatment if only traditional QA is performed.
Material and Methods The kinetic M1 model, is based on the spherical harmonic expansion of the distribution function, solution of the linear Boltzmann equation. The first two angular moments equations, combined with the Continuous Slowing Down Approximation, are closed using the Boltzmann's principle of entropy maximization. The algorithm computes at the same time all primary and secondary particles created by the interactions of the beam with the medium. Thanks to the implementation of the interaction cross sections for electrons and photons in the energy range from 1keV up to 100 MeV, the algorithm can simulate different treatment techniques such as the external radiotherapy, brachytherapy or intra-operative radiation therapy. As a first validation step, a large number of heterogeneity shapes has been defined for various complex numerical phantoms both for electron and photon monoenergetic sources. Dose profiles at different positions have been measured in water phantoms including inhomogeneity of bone ( ρ = 1.85 g/cm3), lung ( ρ = 0.3 g/cm3) and air ( ρ = 10-3 g/cm3). Secondly, taking as reference the Carleton Laboratory for Radiotherapy Physics Database, different radioactive seeds have been implemented in the code. Moreover, several simulations based on CT scan of prostate cancer have been performed. The M1 model is validated with a comparison with a standard, accurate but time consuming, statistical simulation tools as PENELOPE. Results The M1 code is capable of calculating 3D dose distribution with 1mm3 voxels without statistical uncertainties in few seconds instead of several minutes as PENELOPE. Thanks to its capability to take into account the presence of inhomogeneities and strong density gradients, the dose distributions significantly differ from those calculated with the TG-43 approximations. More in detail: inter-seed attenuation is treated, the real chemical composition of the different tissues can be taken into account and the effects of patient dimensions are considered. Conclusion In the comparison with the MC results the excellent accuracy of the M1 model is demonstrated. In general, M1, as the MC codes, overcomes the approximations that are formalised in TG-43 in order to decrease the complexity of the calculations. Thanks to its reduced computational time and its accuracy M1 is a promising candidate to become a real-time decision support tool for brachytherapists.
PO-0946 Entropic model for real-time dose calculation: I-125 prostate brachytherapy application. G. Birindelli1, J.L. Feugeas1, B. Dubroca1, J. Caron1,2, J. Page1, T. Pichard1, V. Tikhonchuk1, P. Nicolaï1 1 Centre Lasers Intenses et Applications, InteractionFusion par Confinement Inertiel- Astrophysique, Talence, France 2 Institut Bergonié Comprehensive Cancer Center, Department of radiotherapy, Bordeaux, France
PO-0947 Image-guided brachytherapy with 106Ru eye plaques for uveal melanomas using post implantation MRI G. Heilemann1, N. Nesvacil2, M. Blaickner3, L. Fetty1, R. Dunavoelgyi4, D. Georg2 1 Medical University of Vienna/ AKH Vienna, Department for Radiotherapy, Vienna, Austria 2 Medical University of Vienna/ AKH Vienna, Department for Radiotherapy/ Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Vienna, Austria 3 Austrian Institute of Technology GmbH, Health and Environment Department Biomedical Systems, Vienna, Austria 4 Medical University of Vienna/ AKH Vienna, Department for Ophthalmology and Optometry, Vienna, Austria
Purpose or Objective This work proposes a completely new Grid Based Boltzmann Solver (GBBS) conceived for the description of the transport and energy deposition by energetic particles for brachytherapy purposes. Its entropic closure and mathematical formulation allow our code (M1) to calculate the delivered dose with an accuracy comparable to the Monte Carlo (MC) codes with a computational time that is reduced to the order of few seconds without any special processing power requirement.
Purpose or Objective In radiation oncology magnetic-resonance imaging (MRI) is an important modality for tissue characterization, target delineation and allows image-guidance due to its high soft tissue contrast as a tool for better cancer treatment. In 106 Ru-brachytherapy of uveal melanomas MRI is mainly used for pre-treatment planning scans to assess tumor size and location. However, post-implantation MR scans yield additional information on the plaque position in relation to the target volume and critical structures. Together with
S525 ESTRO 36 _______________________________________________________________________________________________
funduscopic images MRI can be used to better assess the delivered doses to the target and the organs-at-risk (OAR). The main goal of this feasibility study is to demonstrate that fundus mapping and post implantation MR imaging can be incorporated into the treatment planning workflow of 106Ru plaque brachytherapy. Material and Methods Patients were scanned in a 0.35 T MR scanner (Magnetom C! Siemens, Germany) after 106Ru eye plaque implantation. To achieve a good normal tissue contrast for tumor delineation and organ-at-risk (OAR) segmentation a fast low angle shot (FLASH) T1 weighted sequence was utilized (TR = 15 ms, flip-angles = 25°). A second FLASH MRI scan with lower repetition times (TR = 11.2 ms) and flip-angles (20°) was applied in order to display the plaque as a welldefined void with minimal distortion artifacts at the cost of lower signal to noise ratio and less soft tissue contrast. Based on the MRI the resizable 3D eye model of a newly developed treatment planning software (described in detail in [1]) was adapted to the individual patient anatomy in terms of size and plaque position. Furthermore, the funduscopy image was projected onto the retina of the digital 3D eye model. Results The presented method using two MR sequences yielded 3D image sets that allowed segmenting both the anatomical structures and the 106-Ru plaque. The funduscopy image on the other hand is the optimal modality for tumor segmentation. By combination the 3D eye model can be adapted to match the individual patient and thus allow for individual treatment planning and dose calculation (based on MR anatomy) where the post-implantation imaging accounts for the actual position of the plaque with respect to the target and critical structures. This way irradiation times can be calculated which guarantee full tumor coverage. Moreover, the workflow can be applied for treatment plan optimization strategies where plaques are shifted in order to reduce doses to OARs. Conclusion In this feasibility study it was shown that MRI in combination with funduscopy can be used to optimize brachytherapy with 106Ru plaques. The additional spatial information on plaque position relative to critical structures, tumor geometry as well as position can be used for more precise dose calculations and therefore improved treatment planning. References: [1] G. Heilemann et al. Treatment plan optimization and robustness of 106Ru eye plaque brachytherapy using a novel software tool. Radiotherapy and Oncology. (in revision) Poster: Brachytherapy: Miscellaneous PO-0948 Role of HDR Intraluminal Brachytherapy in carcinoma Esophagus: An institutional experience. P.B. Kainthaje1, P. Gaur1, A. Malavat1, R. Paliwal1, V. Sehra1 1 Dr. Sampurnanand Medical College, Department of Radiotherapy, Jodhpur, India Purpose or Objective To study the profile of patients of Carcinoma Esophagus treated with Intraluminal Brachytherapy (ILBT), the outcome of the treatment in terms of response assessment, toxicity and survival. Material and Methods The study period was between January 2014 and June 2015, with 25 patients of carcinoma esophagus middle third, treated with ILBT either as part of definitive Radiotherapy or as part of palliative Radiotherapy. The patients with unifocal disease ≤10cm in length and with no recorded intra-abdominal or distant metastases received definitive Radiotherapy with 44Gy/22Fr through EBRT with
concurrent Cisplatin and 5-Flurouracil followed by, 10Gy/2Fr of ILBT boost once weekly. The patients with local advanced disease for palliation received 36Gy/12Fr through EBRT followed by, 10Gy/2Fr of ILBT once weekly. The outcome of treatment was assessed in terms of dysphagia score, dysphagia free survival, toxicities and overall survival. Results Median age of patients was 55 years. Histopathologically 96 % has Squamous cell carcinoma. 16 (64%) of patients were treated with definitive radiotherapy while the rest, 9 (36%) with palliative intent. At a median follow up of 9 months, 13 patients were dysphagia free and there were 5 deaths. One month after completion of treatment, 18 patients were dysphagia free while, 2 patients had partial relief and 5 patients did not notice any relief in dysphagia. 2 patients died within 6 months of completion while, 2 patients developed trachea-esophageal fistula during follow-up.
Conclusion ILBT is a safe modality for boost in treatment of carcinoma esophagus provided, the patients are sele cted with caution. PO-0949 Evaluation of role of Interstitial Brachytherapy in Soft Tissue Sarcoma: Single institute experience V. Pareek1 1 Jupiter Hospital- Thane, Radiation Oncology, Mumbai, India Purpose or Objective Soft tissue Sarcomas are rare group of solid tumors comprising of 1% of all solid tumors. The management of soft tissue sarcomas have evolved due to advancements in imaging, histopathology, cytogenetics, and the use of multimodality treatment. The treatment strategies emphasizes on the control of disease locally, sparing of limb function and improvement in the quality of life. High dose brachytherapy has formed a part of the management and has the advantage of providing concentrated dose to tumors and sparing of surrounding normal tissues. In this study we examined the clinical outcome of High dose Brachytherapy for STS at our Hospital through retrospective analysis of the prospective database maintained. Objectives: To review the clinical outcome and quality of life in patients with Soft Tissue Sarcoma treated at our center through High dose rate interstitial brachytherapy.
cylinder applicator (Figure 1b) with 5 catheters. Interdwell distances of 2 and 5 mm were employed and the experiments performed for source activities between 5 and 10 Ci. The EPID response is proportional to the source activity so it is possible to obtain the activity by sending the source to pre-defined dwell position.
Results 3D Cartesian coordinates can be obtained with 0.2 mm accuracy using a single EPID panel. The panel can clearly identify dwell positions 2 mm apart even with the catheter at 24 cm distance (Figure 1c) from the panel. Absolute coordinates can be obtained by adding reference points (representing the corners of the water phantom) in the treatment plan that can be related with the position of the water phantom over the panel during the experiments. An in-house developed software compares all dwell positions/times against the treatment plan. The software can also monitor the sequence of the treatment identifying the afterloader channel connected to each catheter. Therefore, it is possible to detect catheter misplacements, swapped transfer tube connections, wrong dwell times and/or positions and also verify the source activity. Conclusion This work describes an experimental system that can be implemented in the clinic providing experimental pretreatment verification that is not currently available. This method provides several advantages when compared against other dosimeters such as films or MOSFETs as it combines a 2D dosimeter, which has an online response. Our system can detect several problems that would be unnoticed during the treatment if only traditional QA is performed.
Material and Methods The kinetic M1 model, is based on the spherical harmonic expansion of the distribution function, solution of the linear Boltzmann equation. The first two angular moments equations, combined with the Continuous Slowing Down Approximation, are closed using the Boltzmann's principle of entropy maximization. The algorithm computes at the same time all primary and secondary particles created by the interactions of the beam with the medium. Thanks to the implementation of the interaction cross sections for electrons and photons in the energy range from 1keV up to 100 MeV, the algorithm can simulate different treatment techniques such as the external radiotherapy, brachytherapy or intra-operative radiation therapy. As a first validation step, a large number of heterogeneity shapes has been defined for various complex numerical phantoms both for electron and photon monoenergetic sources. Dose profiles at different positions have been measured in water phantoms including inhomogeneity of bone ( ρ = 1.85 g/cm3), lung ( ρ = 0.3 g/cm3) and air ( ρ = 10-3 g/cm3). Secondly, taking as reference the Carleton Laboratory for Radiotherapy Physics Database, different radioactive seeds have been implemented in the code. Moreover, several simulations based on CT scan of prostate cancer have been performed. The M1 model is validated with a comparison with a standard, accurate but time consuming, statistical simulation tools as PENELOPE. Results The M1 code is capable of calculating 3D dose distribution with 1mm3 voxels without statistical uncertainties in few seconds instead of several minutes as PENELOPE. Thanks to its capability to take into account the presence of inhomogeneities and strong density gradients, the dose distributions significantly differ from those calculated with the TG-43 approximations. More in detail: inter-seed attenuation is treated, the real chemical composition of the different tissues can be taken into account and the effects of patient dimensions are considered. Conclusion In the comparison with the MC results the excellent accuracy of the M1 model is demonstrated. In general, M1, as the MC codes, overcomes the approximations that are formalised in TG-43 in order to decrease the complexity of the calculations. Thanks to its reduced computational time and its accuracy M1 is a promising candidate to become a real-time decision support tool for brachytherapists.
PO-0946 Entropic model for real-time dose calculation: I-125 prostate brachytherapy application. G. Birindelli1, J.L. Feugeas1, B. Dubroca1, J. Caron1,2, J. Page1, T. Pichard1, V. Tikhonchuk1, P. Nicolaï1 1 Centre Lasers Intenses et Applications, InteractionFusion par Confinement Inertiel- Astrophysique, Talence, France 2 Institut Bergonié Comprehensive Cancer Center, Department of radiotherapy, Bordeaux, France
PO-0947 Image-guided brachytherapy with 106Ru eye plaques for uveal melanomas using post implantation MRI G. Heilemann1, N. Nesvacil2, M. Blaickner3, L. Fetty1, R. Dunavoelgyi4, D. Georg2 1 Medical University of Vienna/ AKH Vienna, Department for Radiotherapy, Vienna, Austria 2 Medical University of Vienna/ AKH Vienna, Department for Radiotherapy/ Christian Doppler Laboratory for Medical Radiation Research for Radiation Oncology, Vienna, Austria 3 Austrian Institute of Technology GmbH, Health and Environment Department Biomedical Systems, Vienna, Austria 4 Medical University of Vienna/ AKH Vienna, Department for Ophthalmology and Optometry, Vienna, Austria
Purpose or Objective This work proposes a completely new Grid Based Boltzmann Solver (GBBS) conceived for the description of the transport and energy deposition by energetic particles for brachytherapy purposes. Its entropic closure and mathematical formulation allow our code (M1) to calculate the delivered dose with an accuracy comparable to the Monte Carlo (MC) codes with a computational time that is reduced to the order of few seconds without any special processing power requirement.
Purpose or Objective In radiation oncology magnetic-resonance imaging (MRI) is an important modality for tissue characterization, target delineation and allows image-guidance due to its high soft tissue contrast as a tool for better cancer treatment. In 106 Ru-brachytherapy of uveal melanomas MRI is mainly used for pre-treatment planning scans to assess tumor size and location. However, post-implantation MR scans yield additional information on the plaque position in relation to the target volume and critical structures. Together with
S525 ESTRO 36 _______________________________________________________________________________________________
funduscopic images MRI can be used to better assess the delivered doses to the target and the organs-at-risk (OAR). The main goal of this feasibility study is to demonstrate that fundus mapping and post implantation MR imaging can be incorporated into the treatment planning workflow of 106Ru plaque brachytherapy. Material and Methods Patients were scanned in a 0.35 T MR scanner (Magnetom C! Siemens, Germany) after 106Ru eye plaque implantation. To achieve a good normal tissue contrast for tumor delineation and organ-at-risk (OAR) segmentation a fast low angle shot (FLASH) T1 weighted sequence was utilized (TR = 15 ms, flip-angles = 25°). A second FLASH MRI scan with lower repetition times (TR = 11.2 ms) and flip-angles (20°) was applied in order to display the plaque as a welldefined void with minimal distortion artifacts at the cost of lower signal to noise ratio and less soft tissue contrast. Based on the MRI the resizable 3D eye model of a newly developed treatment planning software (described in detail in [1]) was adapted to the individual patient anatomy in terms of size and plaque position. Furthermore, the funduscopy image was projected onto the retina of the digital 3D eye model. Results The presented method using two MR sequences yielded 3D image sets that allowed segmenting both the anatomical structures and the 106-Ru plaque. The funduscopy image on the other hand is the optimal modality for tumor segmentation. By combination the 3D eye model can be adapted to match the individual patient and thus allow for individual treatment planning and dose calculation (based on MR anatomy) where the post-implantation imaging accounts for the actual position of the plaque with respect to the target and critical structures. This way irradiation times can be calculated which guarantee full tumor coverage. Moreover, the workflow can be applied for treatment plan optimization strategies where plaques are shifted in order to reduce doses to OARs. Conclusion In this feasibility study it was shown that MRI in combination with funduscopy can be used to optimize brachytherapy with 106Ru plaques. The additional spatial information on plaque position relative to critical structures, tumor geometry as well as position can be used for more precise dose calculations and therefore improved treatment planning. References: [1] G. Heilemann et al. Treatment plan optimization and robustness of 106Ru eye plaque brachytherapy using a novel software tool. Radiotherapy and Oncology. (in revision) Poster: Brachytherapy: Miscellaneous PO-0948 Role of HDR Intraluminal Brachytherapy in carcinoma Esophagus: An institutional experience. P.B. Kainthaje1, P. Gaur1, A. Malavat1, R. Paliwal1, V. Sehra1 1 Dr. Sampurnanand Medical College, Department of Radiotherapy, Jodhpur, India Purpose or Objective To study the profile of patients of Carcinoma Esophagus treated with Intraluminal Brachytherapy (ILBT), the outcome of the treatment in terms of response assessment, toxicity and survival. Material and Methods The study period was between January 2014 and June 2015, with 25 patients of carcinoma esophagus middle third, treated with ILBT either as part of definitive Radiotherapy or as part of palliative Radiotherapy. The patients with unifocal disease ≤10cm in length and with no recorded intra-abdominal or distant metastases received definitive Radiotherapy with 44Gy/22Fr through EBRT with
concurrent Cisplatin and 5-Flurouracil followed by, 10Gy/2Fr of ILBT boost once weekly. The patients with local advanced disease for palliation received 36Gy/12Fr through EBRT followed by, 10Gy/2Fr of ILBT once weekly. The outcome of treatment was assessed in terms of dysphagia score, dysphagia free survival, toxicities and overall survival. Results Median age of patients was 55 years. Histopathologically 96 % has Squamous cell carcinoma. 16 (64%) of patients were treated with definitive radiotherapy while the rest, 9 (36%) with palliative intent. At a median follow up of 9 months, 13 patients were dysphagia free and there were 5 deaths. One month after completion of treatment, 18 patients were dysphagia free while, 2 patients had partial relief and 5 patients did not notice any relief in dysphagia. 2 patients died within 6 months of completion while, 2 patients developed trachea-esophageal fistula during follow-up.
Conclusion ILBT is a safe modality for boost in treatment of carcinoma esophagus provided, the patients are sele cted with caution. PO-0949 Evaluation of role of Interstitial Brachytherapy in Soft Tissue Sarcoma: Single institute experience V. Pareek1 1 Jupiter Hospital- Thane, Radiation Oncology, Mumbai, India Purpose or Objective Soft tissue Sarcomas are rare group of solid tumors comprising of 1% of all solid tumors. The management of soft tissue sarcomas have evolved due to advancements in imaging, histopathology, cytogenetics, and the use of multimodality treatment. The treatment strategies emphasizes on the control of disease locally, sparing of limb function and improvement in the quality of life. High dose brachytherapy has formed a part of the management and has the advantage of providing concentrated dose to tumors and sparing of surrounding normal tissues. In this study we examined the clinical outcome of High dose Brachytherapy for STS at our Hospital through retrospective analysis of the prospective database maintained. Objectives: To review the clinical outcome and quality of life in patients with Soft Tissue Sarcoma treated at our center through High dose rate interstitial brachytherapy.