ESTRO 2021 Abstract Book

S1554

ESTRO 2021

intracavitary brachytherapy using Co-60 and Ir-192 sources. Materials and Methods

CT-based treatment plans of 20 patients with cervical carcinoma treated with brachytherapy were retrospectively studied. Patients with interstitial implants were planned for 24 Gy in 4 fractions with inverse planning simulated annealing using Co-60 and Ir-192 source keeping same dose objectives. Patients of intracavitary brachytherapy (ICBT) were planned for 21 Gy in 3 fractions with both sources keeping the same dwell positions. The dosimetric parameters Co-60 and Ir-192-based plans were compared in terms of HR-CTV coverage, OAR doses, homogeneity index (HI) and conformity index (CI). Results In interstitial brachytherapy, mean V100 values for Co-60 and Ir-192-based plans were 97.03±1.99 % and 96.42±2.25 % respectively. Mean D90 values for both the sources were 6.71±0.18 Gy and 6.49±0.15 Gy respectively. No significant difference was found in target coverage (p=0.332) while there were significant differences observed in mean D90 values. Average values of D2cc in the bladder for Co-60 and Ir-192-based plans were 4.30±0.57 Gy and 4.27±0.54 Gy respectively while in the rectum, they were 3.96±0.43 Gy and 4.08±0.49 Gy respectively. There were no significant differences between D2cc, D1cc, and D0.1cc values of bladder and rectum. Ir-192 based plans were more homogeneous (HI= 0.68±0.09) than the Co-60 plans (HI= 0.59±0.10), however, the conformity was similar with both the sources. In ICBT plans, mean D90 values for Co-60 and Ir-192 were 4.86±1.29 Gy and 4.94±1.43 Gy respectively. The mean values of the dose received by point A (both left and right) in Co-60-based plans were 6.92 ±0.08 Gy and 7.08±0.08 Gy respectively, while in Ir-192 based plans, they were 6.93±0.09 Gy and 7.07±0.09 Gy respectively. Mean D2cc values in the bladder for Co- 60 and Ir-192 based plans were 6.19±2.72 Gy and 5.93±2.44 Gy respectively while in the rectum, they were 4.17±1.73 Gy and 4.29±1.94 Gy respectively. We did not find any significant difference in dosimetric parameters of Co-60 and Ir-192- based ICBT plans. Conclusion Isodose distribution of Co-60 plans is extended a little along the anterior-posterior direction in interstitial brachytherapy plans and along the superior-inferior direction in intracavitary brachytherapy plans. There are no significant differences in dosimetric parameters and no clinical advantage of using Co-60 source over Ir-192-based HDR brachytherapy. However, when it comes to cost-management, using Co-60 source has the advantage of a longer half life, which reduces the cost of frequent source replacement and disposal. PO-1824 Segmentation of bone marrow using an intensity and histogram-based energy minimization approach J.L. Lopez Guerra 1 , P. Gómez-Millán 2 , M. Perucha 3 , J. Pérez-Carrasco 4 , B. Acha 5 , C. Serrano 5 , B.D. Delgado León 1 , O. Muñoz Muñoz 1 , C. Suárez-Mejías 6 1 Virgen del Rocío University Hospital, Radiation Oncology , Seville, Spain; 2 Virgen del Rocío University Hospital, Radiology, Seville, Spain; 3 Virgen del Rocío University Hospital, Medical Physics, Seville, Spain; 4 University of Seville, Signal and Communications Theory, Seville, Spain; 5 University of Seville, Signal and Communications Theory , Seville, Spain; 6 Virgen del Rocío University Hospital, Technological Information and Innovation, Seville, Spain Purpose or Objective Lung cancer is the leading cause of cancer-related mortality in men and the second leading cause in women. Approximately 85% of lung cancer patients have non-small cell lung cancer (NSCLC), and most present with advanced stage at diagnosis. The current treatment for such patients is chemoradiation (CRT) provided concurrently preferably or sequentially with chemotherapy. The efficacy of concurrent CRT comes at the cost of increased acute haematological toxicity versus sequential treatment. The segmentation of bone marrow in computed tomography (CT) scan is of interest to physicians and physicists for radiation planning and the analysis of haematological toxicity. However, there is sparse research on the segmentation of such structure. This work addresses the design and preliminary analysis of this segmentation tool. Materials and Methods Design and development of an intelligent system for radiotherapy (RT) in patients with lung cancer, taking into account the hematological toxicity associated with bone marrow radiation. For this purpose, an automatic bone marrow contouring algorithm will be designed that will allow the analysis of the bone marrow radiated area. This algorithm is integrated into a computer infrastructure, which will define predictive models based on neural networks and artificial intelligence and machine learning algorithms applying data mining. The proposed bone marrow segmentation algorithm is based on a three- label convex relaxation approach. The main novelty is that the proposed energy function to be minimized includes distance to histogram models of bone marrow combined with gray-level information. Results We first segmented manually 20 cases and were used as ground-truth for training and evaluation purposes. Different metrics were computed and compared with those used in some state-of-the art algorithms. The proposed algorithm outperformed the other methods, obtaining a Dice coefficient of 0.88 ±0.14, a Jaccard index of 0.80 ±0.19, a Sensitivity of 0.94 ±0.15 and a Specificity of 0.95 ±0.04 for bone segmentation. In a second phase, we are developing the algorithm for the bone marrow segmentation (Figure) and is planned to be tested in 600 NSCLC patients treated at 2 Institutions. Finally, we will analyze the association between the bone marrow dose-volume parameters and the grade of acute haematological toxicity experienced by the NSCLC patients.