地形坡度对星载LiDAR(lightdetection and ranging)估测最大树高具有较大的影响。为了提高坡度条件下树高的反演精度,通过建立坡地条件下5种不同的最大树高估测模型,前3个模型分别使用不同DEM(digital elevation model)数据的地形指数...地形坡度对星载LiDAR(lightdetection and ranging)估测最大树高具有较大的影响。为了提高坡度条件下树高的反演精度,通过建立坡地条件下5种不同的最大树高估测模型,前3个模型分别使用不同DEM(digital elevation model)数据的地形指数来量化地形坡度的Xing模型,第4个模型使用波形参数-未改进边缘长度来量化地形坡度,第5个模型与第4个模型类似,用改进边缘长度来替换未改进边缘长度。结果可知,波形参数模型的精度要高于使用DEM数据的地形指数的Xing模型的精度,第5个模型的精度要高于第4个模型的精度。表明波形参数量化地形坡度的能力要优于DEM数据的地形指数,而改进边缘长度模型更适合估测坡地的最大树高。展开更多
Background Real-time perfusion imaging （RTPI） using ultrasound contrast agents has shown good ＂accuracy＂ in detecting myocardial infarction, however its accuracy in the assessment of peri-infarct ischemia and stre...Background Real-time perfusion imaging （RTPI） using ultrasound contrast agents has shown good ＂accuracy＂ in detecting myocardial infarction, however its accuracy in the assessment of peri-infarct ischemia and stress echocardiography are not known. The aim of this study was to determine the accuracy of RTPI in assessment of peri-infarct ischemia during dobutamine and adenosine stress. Methods We employed the RTPI modality （Agilent and ATL Philips） in a canine model （18 dogs） of distal coronary occlusion and proximal coronary stenosis. Using coronary flow probe recordings, the physiologic significance of proximal coronary stenosis was established by confirming abolition of the coronary reserve. The contrast agent Optison was given as a slow bolus injection at baseline, during prolonged distal coronary occlusion, during adenosine bolus stress and during dobutamine stress. Triphenyltetrazolium chloride （TTC） staining was used to verity a distal infarction. RTPI recordings at baseline, the distal coronary occlusion and stress protocols were randomly mixed and reviewed blindly. Results In all but one dog, RTPI detected a distal infarct as small as 9% of the left ventricle. The sensitivity, specificity and overall diagnostic accuracy of RTPI in the detection of distal infarcts were： 94%, 89% and 92%, respectively. The sensitivity, specificity, and overall diagnostic accuracy of RTPI in the assessment of peri-infarction ischemia were 83%, 92% and 88% for adenosine stress and 95%, 86% and 91% for dobutamine stress, respectively. Conclusions Even small distal infarcts can be detected by RTPI; peri-infarct ischemia can be accurately recognized by RTPt during stress; adenosine and dobutamine stress appear equally reliable in the RTPI evaluation of peri-infarct ischemia.展开更多
文摘地形坡度对星载LiDAR(lightdetection and ranging)估测最大树高具有较大的影响。为了提高坡度条件下树高的反演精度,通过建立坡地条件下5种不同的最大树高估测模型,前3个模型分别使用不同DEM(digital elevation model)数据的地形指数来量化地形坡度的Xing模型,第4个模型使用波形参数-未改进边缘长度来量化地形坡度,第5个模型与第4个模型类似,用改进边缘长度来替换未改进边缘长度。结果可知,波形参数模型的精度要高于使用DEM数据的地形指数的Xing模型的精度,第5个模型的精度要高于第4个模型的精度。表明波形参数量化地形坡度的能力要优于DEM数据的地形指数,而改进边缘长度模型更适合估测坡地的最大树高。
基金This study was supported by a grant from the National Natural Science Foundation of China （No. 30670875）.
文摘Background Real-time perfusion imaging （RTPI） using ultrasound contrast agents has shown good ＂accuracy＂ in detecting myocardial infarction, however its accuracy in the assessment of peri-infarct ischemia and stress echocardiography are not known. The aim of this study was to determine the accuracy of RTPI in assessment of peri-infarct ischemia during dobutamine and adenosine stress. Methods We employed the RTPI modality （Agilent and ATL Philips） in a canine model （18 dogs） of distal coronary occlusion and proximal coronary stenosis. Using coronary flow probe recordings, the physiologic significance of proximal coronary stenosis was established by confirming abolition of the coronary reserve. The contrast agent Optison was given as a slow bolus injection at baseline, during prolonged distal coronary occlusion, during adenosine bolus stress and during dobutamine stress. Triphenyltetrazolium chloride （TTC） staining was used to verity a distal infarction. RTPI recordings at baseline, the distal coronary occlusion and stress protocols were randomly mixed and reviewed blindly. Results In all but one dog, RTPI detected a distal infarct as small as 9% of the left ventricle. The sensitivity, specificity and overall diagnostic accuracy of RTPI in the detection of distal infarcts were： 94%, 89% and 92%, respectively. The sensitivity, specificity, and overall diagnostic accuracy of RTPI in the assessment of peri-infarction ischemia were 83%, 92% and 88% for adenosine stress and 95%, 86% and 91% for dobutamine stress, respectively. Conclusions Even small distal infarcts can be detected by RTPI; peri-infarct ischemia can be accurately recognized by RTPt during stress; adenosine and dobutamine stress appear equally reliable in the RTPI evaluation of peri-infarct ischemia.
