Objective To propose a novel method for image segmentation based on"catalyst" segmentation method.Methods Feeler image was imported into segmentation algorithm as the"catalyst",and whether the candidate nodes should stop segmentation or not was decided according to whether the catalyst appeared in the segmentation result.Results Image segmentation based on "catalyst" segmentation method could judge the right class number for segmented images.Conclusions Primary experiments shows that "catalyst" segmentation method is simple and useful.

Objective To find a method for calculating the scatter dose of irregular fields. Methods The original Day function was improved to vary with radiation depth, and the improved Day function was used for irregular fields to calculate scatter dose. Results The accuracy was greatly improved by making Day function depend on radiation depth, and the error was within 1.5%. Conclusion This method can be used to calculate the scatter dose of irregular fields as well as rectangular fields.