ESTRO 36 Abstract Book

S36 ESTRO 36 2017 _______________________________________________________________________________________________

Respiratory motion is a major concern in the treatment of lung tumors. Time resolved computed tomography (4D-CT) is the clinical standard to determine internal target volumes (ITVs). To overcome limitations of the 4D-CT (radiation dose, averaging of breathing cycles) the aim of this work is to develop a workflow for 4D-magnetic resonance imaging (4D-MRI) based target volume evaluation and determination. Material and Methods 4D-MRI (real-time, 157 volumes) with a temporal resolution of 0.5s and a spatial resolution of 3.91x3.91x10mm 3 , 4D-CT and breath-hold planning-CT (pCT) with clinical structures of lung tumor patients were utilized in this study. The diaphragm excursion in cranial- caudal direction was evaluated for the retrospective determination of the respiration phase on 4D-CT and 4D- MRI. The established workflow is outlined in fig. 1. The rigid registration from pCT to 4D-MRI and the corresponding propagation of gross tumor volume (GTV) and CT-based ITV CT were performed using the Image Processing Toolbox 9.2 (Matlab). The non-rigid registration and GTV propagation between the different 4D-MRI volumes was performed with the B-spline algorithm of plastimatch version 1.6.3. Fig 1: Schematic of the developed workflow: Computation of the target volume monitoring requires p-CT, DICOM-RT structures (GTV and ITV), 4D-CT and 4D-MRI. Reconstruction of the breathing-curve from 4D-CT and 4D- MRI enables a rigid registration of the p-CT to the 4D-MRI. By rigid transformation the GTV and the CT-based ITV CT are transferred to the MRI. The estimation of the tumor movement is done with a non-rigid registration of 4D-MRI volumes and the propagation of the GTV structures. Results The detection of the diaphragm is robust and facilitates a rigid registration of the p-CT to the most similar 4D-MRI volume. Based on non-rigid transformations of the GTV in- between the different volumes of the 4D-MRI, the movement of the tumor is determined and tracked (GTV deformed ). The estimated breathing curve and two representative MRI images are shown in fig. 2. The algorithm highlights those voxels of the GTV deformed in red which are not covered by the ITV CT . The ITV CT was too small for 34 out of 157 MRI volumes of the shown exemplary patient case. Maximally 7% of the GTV deformed were not covered by the ITV CT . An improved ITV MR can be determined by the union of all GTV deformed .

Fig 2: The estimated breathing curve is shown in the upper panel. The rigid registration form p-CT to 4D-MRI was performed using the 4D-MRI volumes of time point C. In the two shown MRI images the ITV CT and the deformed GTV are marked for the two extreme values of the breathing curve. For the time point B the GTV deformed is not covered by the ITV CT . Conclusion The feasibility of 4D-MRI based target volume evaluation and determination is demonstrated. The technic provides improved determination of a 4D-MRI based ITV MR , which covers the GTV motion over several breathing cycles. The proposed technique can be used in MRI-guided radiotherapy workflows. OC-0073 Shoulder girdle impairment evaluation in breast cancer patients undergoing surgery and radiotherapy D. Smaniotto 1 , D. Marchesano 1 , L. Boldrini 1 , V. Masiello 1 , M. Giraffa 1 , L. Maggi 2 , E. Amabile 2 , P.E. Ferrara 2 , F. Landi 2 , V. Valentini 1 , G. Mantini 1 1 Policlinico Universitario Agostino Gemelli- Catholic University, Radiation Oncology Department - Gemelli ART, Roma, Italy 2 Policlinico Universitario Agostino Gemelli- Catholic University, Physical Medicine and Rehabilitation Unit, Roma, Italy Purpose or Objective Aim of this study is to measure the incidence of pain and functional impairment of the ipsilateral shoulder girdle in patients who underwent surgery and radiotherapy (RT) for breast cancer, in order to elaborate preventive rehabilitation or treatments protocols contributing to an increase of patient quality of life. Material and Methods Patients who underwent surgery and radiotherapy for breast cancer since 2009 and currently in follow up protocols were selected. Exclusion criteria were the presence of moderate/severe arthrosis history and/or rheumatologic diseases. All the patients had complete physical and multi- dimensional exams during joint RT and physical medicine follow up visits. The physical exam included the range of motion (ROM) evaluation through goniometric measurement of flexion, abduction, internal rotation and external rotation movements of the shoulder girdle. Pain trigger points were identified and global performance status was assessed too. The used scales were VAS (Visual Analogue Scale) for pain and depression, DASH (Disability of the arm, shoulder and hand) and the KI (Karnofsky Index). Statistical analysis was realized with SPSS software v.14. Results 111 patients were selected: 94% of them underwent quadrantectomy while 6% had radical mastectomy. 60% of them had SLNB, while 40% underwent lymphadenectomy. 72% of them underwent standard adjuvant RT (5040 cGy/180 cGy on the breast and 1000 cGy/200 cGy boost and tumoral bed), while 28% had hypofractionated RT (4005 cGy/267 cGy). Mean ages of the groups were 57.9 and 70.1 years respectively. The ROM mean differences between the healthy and surgery side in the standard treatment group were 7°56’ for shoulder flexion, 13°48’ for abduction, 1°12’ for external rotation and 0°6’ for internal rotation. In the hypofractionated group the observed mean values were 8°52’, 11°8’, 0°35’ and 0°14’ respectively. The standard RT group showed the following mean values: VAS pain 2.0, VAS depression 3.7, DASH 12.4 and KI 91.5%. For the hypofractionated group the following mean values were recorded: VAS pain 2.4, VAS depression 4.8, DASH 16.8 and KI 91.2%.