Abstract book - ESTRO meets Asia

S48 ESTRO meets Asia 2018

these applicators in 1.5T with proper commissioning. We are in the process of starting MR image-based BT using 3T MRI. Hence, we carried out some QA tests using 3T MRI. The aim of this abstract is to report the results of the commissioning. Material and Methods Commercially available Vienna (Elekta) applicator was commissioned, which was made up of plastic body and Ti needles. A CT/MR compatible phantom of size 30cm x 20 cm x 12 cm was fabricated such that the applicator can be positioned in a reproducible geometry. The phantom was filled with the gel (3% Agarose + 1% Copper Sulphate) to closely resemble the tissue density in MRI. CT and MRI (GE- Discovery ) (1.5T and 3.0T) images of the phantom with the applicator were obtained followed by rigid registration and image analysis. CT slice thickness was 0.625mm, while MR was 3mm with 0.5 mm spacing. MR images were analyzed for image quality and geometry. The MR images obtained for 1.5T were as per the institutional protocol established already; however a new protocol for 3T was attempted: T1 weighted FRFSE, T2 weighted FRFSE, T2 weighted SSFSE and T2 weighted FSE, all with a band width of 125 and of equal matrix of 256 x 256 pixels. Various combination of TE (echo time), TR (repetition time), and Echo Train length were also used. Results Vienna applicator did not show much difference in the image quality between 1.5 and 3.0T. For Ti needles, T2 images had a better contrast as compared to T1 in 3T, the needle tip could be more easily located in T1. When compared between T2 weighted FRFSE and FSE sequence, the former one had a grainy appearance but the needle body and tip could be well identified in both. T2 weighted FSE sequence had a distinct artifact at the tip with a signal void region extending up to 0.8 cm, but when fused with CT, the needle tip was found to lie beyond the artifact at 0.5 cm in the signal void region, while in the T1 image the susceptibility artifact matched the CT tip. SSFSE series images were not of good quality. It was found that T1 weighted images with 100 kHz bandwidth, TR= 1160, TE min, Echo train length=6, slice thickness=3 mm and spacing of 0.5mm, are best for titanium needle reconstruction with 3T, especially for needle tip. Clinically, for reconstruction of Ti needles, we use CT images, with co registration with MRI, based on the The commissioning of the applicators was carried out, as a part of prerequisite for the clinical implantation of MR image based adaptive Brachytherapy. PV-123 3D printing in intracavitary head and neck, vaginal, and penis contact Interventional Radiotherapy V. Lancellotta 1 , L. Tagliaferri 2 , G. Kovacs 3 , S. Pagano 4 , A. Ricci 5 , S. Saldi 6 , S. Chierchini 7 , S. Cianetti 8 , V. Valentini 9 , C. Aristei 10 1 Ospedale Santa Maria della Misericordia, Radiation Oncology Unit- Department of Surgical and Bio medical Science, Perugia, Italy 2 Scienze Oncologiche ed Ematologiche- Università Cattoli ca del Sacro Cuore- Fondazione Policlinico Universitario Agostino Gemelli, Radiation Oncology, Rome, Italy 3 Interdisciplinary Brachytherapy Unit- University of Lübe ck - University Hospital S-H- Campus Lübeck, Radiation Oncology, Lubeck, Germany 4 Paediatric Dentistry Unit- Department of Surgical and Bi omedical Science University of Perugia, Department of Surgical and Biomedical Science, Perugia, Italy 5 3dific srl- Perugia, Engineering Section Manager, Perugia, Italy 6 University of Perugia, Radiation Oncologist- Radiation Oncology Unit, Perugia, Italy applicator. Conclusion

Conclusion The fabricated phantom is a representative female pelvis, realistic in size and anatomy and suitable for the evaluation of cervix cancer treatments. The materials chosen approximate tissue, organ and bone densities and allow for distinguishable structures in treatment planning. The fabricated phantom can accommodate TLDs and ion chamber for measurements; however provision can be made to use film, chemical dosimeters and OSLDs. Probability of occurrence of second malignancies may be evaluated. The dosimetric measurements show that the fabricated phantom can be used for the verification of dose delivery in various intra cavitary brachytherapy applications for tratment of carcinoma cervix. PV-122 Applicator commissioning using 3T MRI for Image Guided Adaptive Brachytherapy J. Swamidas 1 , S. Paul 2 , K. Joshi 3 , S. Chopra 1 , U. Mahantshetty 4 , S. Panda 1 , K. Chauhan 1 , D. Deshpande 5 1 Advanced Centre for Treatment Research and Educatio n in CancerACTREC- Tata Memorial Centre, Radiation Oncology, Mumbai, India 2 Advanced Centre for Treatment Research and Education in Cancer ACTREC- Tata Memorial Centre, Radiation Oncology, Mumbai, India 3 Advanced Centre for Treatment Research and Education in CancerACTREC- Tata Memorial Centre, Department of Radiation Oncology, Navi Mumbai, India 4 Tata Memorial Hospital, Radiation Oncology, Mumbai, India 5 Tata Memorial Hospital, Medical Physics, Mumbai, India Purpose or Objective In MRI image-based brachytherapy, it is highly recommended to commission applicators to minimize the uncertainties of applicator reconstruction. It has been reported that Ti needles cause susceptibility artifacts especially in 3T MRI. The manufacturer specification of the magnetic field strength to be used with certain applicators are 0.3-0.5T, however we have been using