[Calculating the Hausdorff distance based on the scripting in RayStation treatment planning system].

Objective: To calculate out the Hausdorff distance based on the scripting in RayStation treatment planning system, which was then applied in measuring the deformation error of brain stem during image automatic registration between CT and MR. Methods: Scripting was edited in RayStation system (version 4.7) by using IronPython. The set of point coordinates on the contour of any two region of interest (ROI) had been found firstly, then the Hausdorff distance between the two point sets was calculated out. A graphical user interface (GUI) was designed by using XAML to acquire the visualized output of Hausdorff distance. GUI appeared when the script was run, where two ROIs was selected, then the corresponding Hausdorff distance and the running time were displayed by pressing the "Calculate" button. Results: The mean Hausdorff distance of brain stem in 20 patients with head and neck neoplasms was 1.20 cm while the mean elapsed time was 11.01s. Conclusions: Hausdorff distance of any two ROIs can be calculated out by using the developed method. GUI is designed to realize the visual interaction with RayStation system. Therefore, the RayStation system satisfies the demands of Hausdorff distance calculation in both clinical and research work.

Relation between geographical distribution of liver cancer and climate-aflatoxin B1 in China.

This paper analyses, for the first time in China, the relationship between the data on climate (temperature and humidity) in the country, aflatoxin, hepatitis B and primary liver cancer mortality, by using the methods of geographical epidemiology and generalized factor analysis, and also approaches the characteristics of the geographical distribution of liver cancer in China from a climate-mould viewpoint. The authors come to the conclusion that climate is an important environmental condition that determines the differences in the distributions of liver cancer in different areas, and that aflatoxin B1 is one of the main carcinogenic factors of liver cancer.