<qa>  What is the amount of alendronate per week in the first 16 weeks?This study will include ESRD patients who had received maintenance PD for more than 3 months, have high CPP level 55, and have chest X-ray proven aortic calcification or coronary artery calcification. All participants are randomly allocated to either group 1 or group 2. Group 1 patients receive alendronate 70 mg once weekly in the first 16 weeks, while group 2 patients receive the same dose of drug every week in the second 16 weeks. The extent of coronary artery and aortic calcification is evaluated by using multi-detector spiral computed tomography, whereas bone mineral density is measured by dual-energy X-ray absorptiometry. Both examinations are performed at week 0, 16 and 32 for each participant. Laboratory studies and possible adverse reactions were regularly monitored. 