No abstract

Radiation therapy (RT) in general requires a treatment period of 5 to 7 weeks. Tumor shrinkage in response to RT and weight loss due to radiationinduced mucositis may impact on the dose distribution in both target and organ at risk in patients Abstract : The treatment period over which radiation therapy is administered extends over several weeks. Since tumor shrinkage in response to radiation therapy and weight loss due to radiation-induced mucositis may impact on the dose distribution in both target and organ at risk in patients with head and neck cancer, the anatomical changes of tumor and neck volumes during this period should be taken into consideration. We investigated the anatomical changes that occurred in the target and normal structure of the neck during radiation therapy for pharyngeal cancer, and evaluated the necessity of an adaptive strategy. Ten patients with pharyngeal cancer who underwent radical chemoradiation therapy using 3-dimensional conformal radiation therapy RT ( ORIGINAL Changes

Conditions for occurrence of pendulum airflow under spontaneous ventilation were studied in adult dogs with flail chest experimentally constructed by removing three ribs and the chest wall. Pendulum air flow was recorded pneumotachometrically from outside the body by intubation to the bronchi. Despite objections to the occurrence of pendulum air by many investigators, we found that pendulum airflow occurs under various conditions. The main factors facilitating the occurrence included 1) Significant differences in airway pressure and ventilatory volume between the lungs on the injured and the opposite side. 2) A high frequency of respiration. 3) Increased resistance in the upper airway. The pendulum airflow occurred not only at the area of tracheal bifurcation but also in the peripheral bronchial airway in the ipsi-lateral thorax of the flail chest. However, pendulum airflow was observed only transiently coinciding with the time of change from one phase of respiration to the other, and volume of pendulum airflow was considered to be so minimal that it had no significant deleterious influence on the alveolar ventilation. In cases of marked dysfunction of the chest wall or with increasing upper airway resistance, pendulum airflow may disturb alveolar ventilation to a considerable extent.

If rectal gas is present during either IMRT or VMAT, a dose decrease will occur in relation to CTV and PTV, suggesting that a plan does not eliminate adverse effects on organs at risk.

In cervical cancer treatment, radiation therapy is selected based on the degree of tumor progression, and radiation oncologists are required to delineate tumor contours. To reduce the burden on radiation oncologists, an automatic segmentation of the tumor contours would prove useful. To the best of our knowledge, automatic tumor contour segmentation has rarely been applied to cervical cancer treatment. In this study, diffusion-weighted images (DWI) of 98 patients with cervical cancer were acquired. We trained an automatic tumor contour segmentation model using 2D U-Net and 3D U-Net to investigate the possibility of applying such a model to clinical practice. A total of 98 cases were employed for the training, and they were then predicted by swapping the training and test images. To predict tumor contours, six prediction images were obtained after six training sessions for one case. The six images were then summed and binarized to output a final image through automatic contour segmentation. For the evaluation, the Dice similarity coefficient (DSC) and Hausdorff distance (HD) was applied to analyze the difference between tumor contour delineation by radiation oncologists and the output image. The DSC ranged from 0.13 to 0.93 (median 0.83, mean 0.77). The cases with DSC <0.65 included tumors with a maximum diameter < 40 mm and heterogeneous intracavitary concentration due to necrosis. The HD ranged from 2.7 to 9.6 mm (median 4.7 mm). Thus, the study confirmed that the tumor contours of cervical cancer can be automatically segmented with high accuracy.