针对EVaR(Expectile-based Value at Risk)风险度量提出了基于GARCH类和SV波动率模型的EVaR风险度量计算方法,即EVaR计算的参数模型方法.并基于模拟学生t分布时间序列数据,给出EVaR样本外预测的失败率检验方法:Kupiec失败率检验和动态...针对EVaR(Expectile-based Value at Risk)风险度量提出了基于GARCH类和SV波动率模型的EVaR风险度量计算方法,即EVaR计算的参数模型方法.并基于模拟学生t分布时间序列数据,给出EVaR样本外预测的失败率检验方法:Kupiec失败率检验和动态分位数(DQ)检验法.与采用CARE(Conditional Autoregressive Expectile)模型的EVaR计算方法进行了对比研究,结果表明基于GARCH类模型和SV模型相对于基于CARE模型有更优的EVaR预测效果.选取2004年1月5日到2009年12月30日的国内外五个股票市场指数数据,针对日对数收益率进行了EVaR风险度量的实证研究,得出在金融危机期间,基于参数模型的EVaR预测要比基于CARE模型的EVaR预测更接近市场实际风险.展开更多
Background Endovascular aneurysm repair (EVAR) is a new technology to treat pa tients with abdominal aortic aneurysm (AAA) when the anatomy is suitable. Uncert ainty exists about how endovascular repair compares with ...Background Endovascular aneurysm repair (EVAR) is a new technology to treat pa tients with abdominal aortic aneurysm (AAA) when the anatomy is suitable. Uncert ainty exists about how endovascular repair compares with conventional open surge ry. EVAR trial 1 was instigated to compare these treatments in patients judged f it for open AAA repair. Methods Between 1999 and 2003, 1082 elective (non emerg ency) patients were randomised to receive either EVAR (n=543) or open AAA repair (n=539). Patients aged at least 60 years with aneurysms of diameter 5.5 cm or m ore, who were fit enough for open surgical repair (anaesthetically and medically well enough for the procedure), were recruited for the study at 41 British hosp itals proficient in the EVAR technique. The primary outcome measure is all cause mortality and these results will be rele ased in 2005. The primary analysis presented here is operative mortality by inte ntion to treat and a secondary analysis was done in per protocol patients. Find ings Patients (983 men, 99 women) had a mean age of 74 years (SD 6) and mean AAA diameter of 6.5 cm (SD 1). 1047 (97%) patients underwent AAA repair and 1008 ( 93%) received their allocated treatment. 30-day mortality in the EVAR group wa s 1.7%(9/531)versus 4.7%(24/516) in the open repair group (odds ratio 0.35<<95 %CI 0.16-0.77>>, p=0.009). By per protocol analysis, 30-day mortality for EVA R was 1.6%(8/512) versus 4.6%(23/496) for open repair (0.33 <<0.15-0.74>>, p=0. 007). Secondary interventions were more common in patients allocated EVAR (9.8% vs 5.8%, p=0.02). Interpretation In patients with large AAAs, treatment by EVAR reduced the 30-day operative mortality by two thirds compared with open repai r. Any change in clinical practice should await durability and longer term resul ts.展开更多
Background Endovascular aneurysm repair (EVAR) is a new technology to treat pa tients with abdominal aortic aneurysm (AAA) when the anatomy is suitable. Uncert ainty exists about how endovascular repair compares with ...Background Endovascular aneurysm repair (EVAR) is a new technology to treat pa tients with abdominal aortic aneurysm (AAA) when the anatomy is suitable. Uncert ainty exists about how endovascular repair compares with conventional open surge ry. EVAR trial 1 was instigated to compare these treatments in patients judged f it for open AAA repair. Methods Between 1999 and 2003,1082 elective (non emerge ncy) patients were randomised to receive either EVAR (n=543) or open AAA repair (n=539). Patients aged at least 60 years with aneurysms of diameter 5.5 cm or mo re, who were fit enough for open surgical repair (anaesthetically and medically well enough for the procedure), were recruited for the study at 41 British hospi tals proficient in the EVAR technique. The primary outcome measure is all cause mortality and these results will be released in 2005. The primary analysis pres ented here is operative mortality by intention to treat and a secondary analysis was done in per protocol patients. Findings Patients (983 men, 99 women) had a mean age of 74 years (SD 6) and mean AAA diameter of 6.5 cm (SD 1). 1047 (97%) patients underwent AAA repair and 1008 (93%) received their allocated treatmen t. 30-day mortality in the EVAR group was 1.7%(9/531) versus 4.7%(24/516) in the open repair group (odds ratio 0.35 [95%CI 0.16-0.77], p=0.009). By per p rotocol analysis, 30-day mortality for EVAR was 1.6%(8/512) versus 4.6%(23/49 6) for open repair (0.33 [0.15-0.74], p=0.007). Secondary interventions were mo re common in patients allocated EVAR (9.8%vs 5.8%, p=0.02). Interpretation In patients with large AAAs, treatment by EVAR reduced the 30-day operative mortal ity by two thirds compared with open repair. Any change in clinical practice sh ould await durability and longer term results.展开更多
Objectives: This study aimed to determine whether errors in vascular measurements would affect device selection in endovascular aortic repair (EVAR) by comparing measurements obtained using non-contrast computed tomog...Objectives: This study aimed to determine whether errors in vascular measurements would affect device selection in endovascular aortic repair (EVAR) by comparing measurements obtained using non-contrast computed tomography (NCT) with those obtained using contrast-enhanced CT (CECT). Materials and Methods: This single-center, retrospective study included 25 patients who underwent EVAR for abdominal aortic aneurysm at our institution. A 1-mm horizontal cross-sectional slice of NCT and CECT from each patient was retrospectively reviewed. The area from the abdominal aorta to the common iliac artery was divided into four zones. A centerline was created using the NCT by manually plotting the center points. Subsequently, the centerlines were automatically extracted and manually corrected during the arterial phase of CECT. The diameter and length of each zone were measured for each modality. The mean diameters and lengths of the target vessels were compared between NCT and CECT. Results: The measurements obtained using both methods were reproducible and demonstrated good agreement. The mean differences in vessel length and diameter measurements for each segment between NCT and CECT were not statistically significant, indicating good consistency. Conclusion: NCT may be useful for preoperative EVAR evaluation in patients with renal dysfunction or allergies to contrast agents.展开更多
文摘针对EVaR(Expectile-based Value at Risk)风险度量提出了基于GARCH类和SV波动率模型的EVaR风险度量计算方法,即EVaR计算的参数模型方法.并基于模拟学生t分布时间序列数据,给出EVaR样本外预测的失败率检验方法:Kupiec失败率检验和动态分位数(DQ)检验法.与采用CARE(Conditional Autoregressive Expectile)模型的EVaR计算方法进行了对比研究,结果表明基于GARCH类模型和SV模型相对于基于CARE模型有更优的EVaR预测效果.选取2004年1月5日到2009年12月30日的国内外五个股票市场指数数据,针对日对数收益率进行了EVaR风险度量的实证研究,得出在金融危机期间,基于参数模型的EVaR预测要比基于CARE模型的EVaR预测更接近市场实际风险.
文摘Background Endovascular aneurysm repair (EVAR) is a new technology to treat pa tients with abdominal aortic aneurysm (AAA) when the anatomy is suitable. Uncert ainty exists about how endovascular repair compares with conventional open surge ry. EVAR trial 1 was instigated to compare these treatments in patients judged f it for open AAA repair. Methods Between 1999 and 2003, 1082 elective (non emerg ency) patients were randomised to receive either EVAR (n=543) or open AAA repair (n=539). Patients aged at least 60 years with aneurysms of diameter 5.5 cm or m ore, who were fit enough for open surgical repair (anaesthetically and medically well enough for the procedure), were recruited for the study at 41 British hosp itals proficient in the EVAR technique. The primary outcome measure is all cause mortality and these results will be rele ased in 2005. The primary analysis presented here is operative mortality by inte ntion to treat and a secondary analysis was done in per protocol patients. Find ings Patients (983 men, 99 women) had a mean age of 74 years (SD 6) and mean AAA diameter of 6.5 cm (SD 1). 1047 (97%) patients underwent AAA repair and 1008 ( 93%) received their allocated treatment. 30-day mortality in the EVAR group wa s 1.7%(9/531)versus 4.7%(24/516) in the open repair group (odds ratio 0.35<<95 %CI 0.16-0.77>>, p=0.009). By per protocol analysis, 30-day mortality for EVA R was 1.6%(8/512) versus 4.6%(23/496) for open repair (0.33 <<0.15-0.74>>, p=0. 007). Secondary interventions were more common in patients allocated EVAR (9.8% vs 5.8%, p=0.02). Interpretation In patients with large AAAs, treatment by EVAR reduced the 30-day operative mortality by two thirds compared with open repai r. Any change in clinical practice should await durability and longer term resul ts.
文摘Background Endovascular aneurysm repair (EVAR) is a new technology to treat pa tients with abdominal aortic aneurysm (AAA) when the anatomy is suitable. Uncert ainty exists about how endovascular repair compares with conventional open surge ry. EVAR trial 1 was instigated to compare these treatments in patients judged f it for open AAA repair. Methods Between 1999 and 2003,1082 elective (non emerge ncy) patients were randomised to receive either EVAR (n=543) or open AAA repair (n=539). Patients aged at least 60 years with aneurysms of diameter 5.5 cm or mo re, who were fit enough for open surgical repair (anaesthetically and medically well enough for the procedure), were recruited for the study at 41 British hospi tals proficient in the EVAR technique. The primary outcome measure is all cause mortality and these results will be released in 2005. The primary analysis pres ented here is operative mortality by intention to treat and a secondary analysis was done in per protocol patients. Findings Patients (983 men, 99 women) had a mean age of 74 years (SD 6) and mean AAA diameter of 6.5 cm (SD 1). 1047 (97%) patients underwent AAA repair and 1008 (93%) received their allocated treatmen t. 30-day mortality in the EVAR group was 1.7%(9/531) versus 4.7%(24/516) in the open repair group (odds ratio 0.35 [95%CI 0.16-0.77], p=0.009). By per p rotocol analysis, 30-day mortality for EVAR was 1.6%(8/512) versus 4.6%(23/49 6) for open repair (0.33 [0.15-0.74], p=0.007). Secondary interventions were mo re common in patients allocated EVAR (9.8%vs 5.8%, p=0.02). Interpretation In patients with large AAAs, treatment by EVAR reduced the 30-day operative mortal ity by two thirds compared with open repair. Any change in clinical practice sh ould await durability and longer term results.
文摘Objectives: This study aimed to determine whether errors in vascular measurements would affect device selection in endovascular aortic repair (EVAR) by comparing measurements obtained using non-contrast computed tomography (NCT) with those obtained using contrast-enhanced CT (CECT). Materials and Methods: This single-center, retrospective study included 25 patients who underwent EVAR for abdominal aortic aneurysm at our institution. A 1-mm horizontal cross-sectional slice of NCT and CECT from each patient was retrospectively reviewed. The area from the abdominal aorta to the common iliac artery was divided into four zones. A centerline was created using the NCT by manually plotting the center points. Subsequently, the centerlines were automatically extracted and manually corrected during the arterial phase of CECT. The diameter and length of each zone were measured for each modality. The mean diameters and lengths of the target vessels were compared between NCT and CECT. Results: The measurements obtained using both methods were reproducible and demonstrated good agreement. The mean differences in vessel length and diameter measurements for each segment between NCT and CECT were not statistically significant, indicating good consistency. Conclusion: NCT may be useful for preoperative EVAR evaluation in patients with renal dysfunction or allergies to contrast agents.
