Objective Clinical application of electrons often involves some beam in which the field size varies with the applicators. The work was done to understand the electron beam characteristics in different field sizes. Methods Percent depth dose and the dose output factor were measured for square and rectangular fields at 100?cm source to surface distance ( SSD ) . Central axis percent depth dose (PDD) measurements were made using the RFA 300 three dimensional radiation field analyzer with a shielded p type diode detector . The dose output factors were measured with the RFA 300 three dimensional radiation field analyzer with a PTW 0.1?cm 3 chamber and a Farmer 2570/1 dosimeter with a 2571 ion chamber in a water phantom. Results The measurements showed that the depth dose curves and the output factors were sometimes dependent on how the field sizes were formed. The change in depth dose with field size was more pronounced in the high energy beams than the low energy ones. However, the output factor did not show any systematic energy dependence because each applicator had it's own X ray jaw setting at each energy. Conclusions When using small inserted apertures to treat small lesions, we should verify the conformation of depth dose and output factors. In this case, we should use applicator dependent output factors at each energy to calculate the monitor units for irradiation.

Objective To improve the ventilation mode for respiratory failure based on the self-made respirator. Methods For the conscious COPD patients with type II respiratory failure, nasal mask and NEEP ventilation mode were used. Patients breathe in air through the mouth and breathe out through the noses. There is no need of manual control tube to control the negative pressure in the nasal mask. For the non-typical type I respiratory failure, exhaled gas comes out from the one-way channel in the front of the mask, while oxygen for the next breathes is brought into the ball through the tube under it. Results The COPD patients breathe more freely and smoothly without disturb of the manual control tube. On the non-typical type I respiratory failure, FiO2 is much higher and without breath in CO2. Conclusion The new ventilation mode can provide a great range of FiO2 and get ride of redundant CO2. It's beneficial to the recovery of patients.

Simple oxygenation respirator is mainly used for respiratory failure patients who are failed in being treated with open positive pressure.It can markedly improve the oxygenation concentration and ventilation.Most respiratory failure patients can avoid using mechanical respirator if it is used adequately.Respiratory model Ⅰ,Ⅱ,Ⅲ can be applied according to different type of respiratory failure respectively.It is also very effective to cerebral vascular diseases.The structure of respirator is fit for human physiology without interfering cardiac and pulmonary functions.It has no contraindications and side effect.It is simple,cheap and practical.