Objective To investigate indications,pacing modes,pacing parameters and postoperative complications of pacemaker implantation for patients aged 80 years or over.Methods Patients were recruited on a continuous basis and were assigned into two groups,with 112 patients in the very elderly (80-90 years old) group and 484 patients in the elderly (60-79 years old) group,which served as the control.Follow-up observations with the two groups were conducted concerning indications,mode selection,pacing parameters and postoperative complications.Results Compared with the control group,the very elderly group showed:1) a higher rate of coronary heart disease (58cases vs.163 cases or 51.8％ vs.33.7％ ; x2 =12.78,P＜0.01) ; 2) more single-chamber pacemaker implantations (63 cases vs.217 cases or 56.3％ vs.44.8％; x2=4.76,P＜0.05) and fewer dual-or multi-chamber pacemaker implantations (49 cases vs.267 cases or 43.8％ vs.55.2％ ; x2 =4.76,P＜0.05) ; 3) a higher rate of double bundles branch block (19 cases vs.31 cases or 17.0％ vs.6.4％ ; x2=13.20,P＜0.01); 4) a higher rate of postoperative acute cerebral infarction (x2 =8.34,P＜0.01) ; and 5) increased ventricular [(0.78±0.24)V vs.(0.55±0.16)V,P＜0.05]and atrial [(1.07±0.22)V vs.(0.84±0.28)V,P＜0.05]pacing thresholds.Conclusions Special considerations should be made when pacemaker implantation is planned for patients aged 80 or over.Pacemaker selection decisions ought to be based on a comprehensive evaluation of relevant clinical situations so that clinical benefits can be maximized.

This article describes the physical, technical, and dosimetric aspects of total body irradiation (TBI) that was carried out by using 6MV X-Ray from Varian 2300 C/D Linear Accelerator at a distance of 450 cm from target to the treatment table and at a gantry angle of 270°.The dose to lung tissue was limit by setting the individual lead compensators customized before, and using DPD-510 to monitor the absorbed dose of the reference point the absorbed dose in depth of half of body will be (Din+Dout)/2 after taking treatment in both AP position and PA position.

Objective To study the impact of implanted thermoseeds of magnetic induction hyperthermia on radiation dose distribution. Methods To simulate irradiation, an anthropomorphic phantom and three-dimensional treatment planning system were used. The impact of thermoseeds on radiation dose distribution was evaluated. Results The change of absorbed dose caused by the implantated thermoseeds was less than 1.5%. Conclusions The impact of implanted thermoseeds on radiation dose distribution is small and comes up to the requirements that the total target dose uncertainty must be less than 5%. Therefore, the impact of thermoseeds on the absorbed dose in tissue can be ignored in clinical practice.