Lee HY, et al. Radiat Oncol J. 2013 Dec;31(4):239-246. http://dx.doi.org/10.3857/roj.2013.31.4.239

Given the tremendous potential of stereotactic body radiotherapy (SBRT), investigations of the underlying radiobiology associated with SBRT-induced normal tissue injury are of paramount importance. This study was designed to develop an animal model that simulates centrally and peripherally located clinical SBRT-induced lung injuries. A 90-Gy irradiation dose was focally delivered to the central and peripheral areas of the left mouse lung with an image-guided small-animal irradiation system. At 1, 2 and 4 weeks after irradiation, micro-computed tomography (micro-CT) images of the lung were taken. Lung function measurements were performed with the Flexivent^® system (SCIREQ^©, Montreal, Canada). For the histopathological analysis, the lungs were fixed by perfusing with formalin, and paraffin sections were stained with hematoxylin and eosin and Masson's Trichrome. Gross inspection clearly indicated local lung injury confined to the central and peripheral areas of the left lung. Typical histopathological alterations corresponding to clinical manifestations were observed. The micro-CT analysis results appeared to correlate with the histopathological findings. Mouse lung tissue damping increased dramatically at central settings, compared with that at the control or peripheral settings. An animal model to simulate clinical SBRT-induced central and peripheral lung injuries was developed and validated with histopathological, radiological and functional analyses. This model increases our understanding of SBRT-induced central and peripheral lung injuries and will help to improve radiation therapy in the future.

Background: While atlas segmentation (AS) has proven to be a time-saving and promising method for radiation therapy contouring, optimal methods for its use have not been well-established. Therefore, we investigated the relationship between the size of the atlas patient population and the atlas segmentation auto contouring (AC) performance. Methods: A total of 110 patients' head planning CT images were selected. The mandible and thyroid were selected for this study. The mandibles and thyroids of the patient population were carefully segmented by two skilled clinicians. Of the 110 patients, 100 random patients were registered to 5 different atlas libraries as atlas patients, in groups of 20 to 100, with increments of 20. AS was conducted for each of the remaining 10 patients, either by simultaneous atlas segmentation (SAS) or independent atlas segmentation (IAS). The AS duration of each target patient was recorded. To validate the accuracy of the generated contours, auto contours were compared to manually generated contours (MC) using a volume-overlap-dependent metric, Dice Similarity Coefficient (DSC), and a distance-dependent metric, Hausdorff Distance (HD). Results: In both organs, as the population increased from n = 20 to n = 60, the results showed better convergence. Generally, independent cases produced better performance than simultaneous cases. For the mandible, the best performance was achieved by n = 60 [DSC = 0.92 (0.01) and HD = 6.73 (1.31) mm] and the worst by n = 100 [DSC = 0.90 (0.03) and HD = 10.10 (6.52) mm] atlas libraries. Similar results were achieved with the thyroid; the best performance was achieved by n = 60 [DSC = 0.79 (0.06) and HD = 10.17 (2.89) mm] and the worst by n = 100 [DSC = 0.72 (0.13) and HD = 12.88 (3.94) mm] atlas libraries. Both IAS and SAS showed similar results. Manual contouring of the mandible and thyroid required an average of 1,044 (±170.15) seconds, while AS required an average of 46.4 (±2.8) seconds. Conclusions: The performance of AS AC generally increased as the population of the atlas library increased. However, the performance does not drastically vary in the larger atlas libraries in contrast to the logic that bigger atlas library should lead to better results. In fact, the results do not vary significantly toward the larger atlas library. It is necessary for the institutions to independently research the optimal number of subjects.

// <![CDATA[ $('.header-date').hide();$('#titleAuthors').hide();$('#abstractHeader').hide(); // ]]> Kwangwoo Park1, Sungjin Park2, Mi-Jin Jeon1, Jinhyun Choi1, Jun Won Kim1, Yoon Jin Cho1, Won-Seok Jang1, Yo Sup Keum3 and Ik Jae Lee1 1 Department of Radiation Oncology, Gangnam Severance Hospital, College of Medicine, Yonsei University, Gangnam-gu, Seoul, Korea 2 Department of Textiles, Fashion and Merchandising, College of Human Ecology, Seoul National University, Gwanak-gu, Seoul, Korea 3 Texas A&M Health Science Center College of Medicine, Bryan, Texas, USA Correspondence to: Ik Jae Lee, email: // <![CDATA[ mail("ikjae412","yuhs.ac") // ]]> Keywords: 3D-printed bolus, 3D printer, MRM, electron conformal therapy, dosimetery Received: June 20, 2016 Accepted: October 19, 2016 Published: October 23, 2016

In a previous study, we established an image-guided small-animal micro-irradiation system mimicking clinical stereotactic body radiotherapy (SBRT). The goal of this study was to develop a rodent model of acute phase lung injury after ablative irradiation. A radiation dose of 90 Gy was focally delivered to the left lung of C57BL/6 mice using a small animal stereotactic irradiator. At days 1, 3, 5, 7, 9, 11 and 14 after irradiation, the lungs were perfused with formalin for fixation and paraffin sections were stained with hematoxylin and eosin (H&E) and Masson's trichrome. At days 7 and 14 after irradiation, micro-computed tomography (CT) images of the lung were taken and lung functional measurements were performed with a flexiVent™ system. Gross morphological injury was evident 9 days after irradiation of normal lung tissues and dynamic sequential events occurring during the acute phase were validated by histopathological analysis. CT images of the mouse lungs indicated partial obstruction located in the p...