Exhaust gas temperature is an important factor in NOx, THC and PM emissions of engines. Especially 2D temperature and concentration distribution plays an important role for the engine efficiency. A thermocouple is int...Exhaust gas temperature is an important factor in NOx, THC and PM emissions of engines. Especially 2D temperature and concentration distribution plays an important role for the engine efficiency. A thermocouple is intrinsically a point temperature measurement method and noncontact 2D temperature distribution cannot be attained by thermocouples. Recently, as a measurement technique with high sensitivity and high response, laser diagnostics has been developed and applied to the actual engine combustions. With these engineering developments, transient phenomena such as start-ups and load changes in engines have been gradually elucidated in various conditions. In this study, the theoretical and experimental research has been conducted in order to develop the noncontact and fast response 2D temperature and concentration distribution measurement method. The method is based on a Computed Tomography （CT） method using absorption spectra of water vapor at 1388 nm. It has been demonstrated that the method has been successfully applied to engine exhausts to measure 2D temperature distributions.展开更多
背景与目的计算机断层扫描(computed tomography,CT)随访评估结节体积及密度变化是临床针对不定性肺结节采用的常用策略。在保证测量精度前提下降低CT剂量是需要考虑的问题。本研究旨在评估不同管电流及重建算法对肺体模结节容积定量及C...背景与目的计算机断层扫描(computed tomography,CT)随访评估结节体积及密度变化是临床针对不定性肺结节采用的常用策略。在保证测量精度前提下降低CT剂量是需要考虑的问题。本研究旨在评估不同管电流及重建算法对肺体模结节容积定量及CT值测量的影响。方法应用64排螺旋CT,管电压120k V,7种管电流(10 m A、20 m A、50 m A、80 m A、100 m A、150 m A、350 m A)对肺结节体模进行扫描,采用滤波反投影(filtered back projection, FBP)、自适应迭代重建(ASIR:30%,50%,80%)算法进行重建,获取28套CT图像。应用肺结节分析软件对3种直径(2.5 mm,5 mm,10 mm)、三种CT值(-100 HU,60 HU,100 HU)共9个球型结节测量容积及平均CT值数据。应用重复测量方差分析评估不同管电流及原始数据重建算法对容积及CT值测量的影响。结果直径为2.5 mm结节的容积测量相对误差(100.8%±28%)及三维CT值绝对误差(-756±80)HU最大;直径为5 mm及10 mm结节的容积相对误差小[(-0.9%±1.1%)vs(0.9%±1.4%)],但CT值绝对误差大[(-243±26)HU vs(-129±7)HU]。针对直径为5 mm及10 mm结节使用重复测量方差分析结果显示,应用不同管电流及原始数据重建算法时容积测量相对误差没有显著性差异(F=5.60,P=0.10 vs F=11.13,P=0.08),三维CT值的绝对误差有显著影响(F=34.79,P<0.001 vs F=156.14,P<0.001)。结论不同管电流及重建算法对直径5mm及10 mm的结节容积定量影响很小,因此较低管电流及迭代重建算法可以应用在5 mm以上肺结节的CT随访中。结节分析软件提供的平均CT值与标准CT值在不同大小、密度结节中均具有较大误差,不能应用于临床。展开更多
文摘Exhaust gas temperature is an important factor in NOx, THC and PM emissions of engines. Especially 2D temperature and concentration distribution plays an important role for the engine efficiency. A thermocouple is intrinsically a point temperature measurement method and noncontact 2D temperature distribution cannot be attained by thermocouples. Recently, as a measurement technique with high sensitivity and high response, laser diagnostics has been developed and applied to the actual engine combustions. With these engineering developments, transient phenomena such as start-ups and load changes in engines have been gradually elucidated in various conditions. In this study, the theoretical and experimental research has been conducted in order to develop the noncontact and fast response 2D temperature and concentration distribution measurement method. The method is based on a Computed Tomography （CT） method using absorption spectra of water vapor at 1388 nm. It has been demonstrated that the method has been successfully applied to engine exhausts to measure 2D temperature distributions.
文摘背景与目的计算机断层扫描(computed tomography,CT)随访评估结节体积及密度变化是临床针对不定性肺结节采用的常用策略。在保证测量精度前提下降低CT剂量是需要考虑的问题。本研究旨在评估不同管电流及重建算法对肺体模结节容积定量及CT值测量的影响。方法应用64排螺旋CT,管电压120k V,7种管电流(10 m A、20 m A、50 m A、80 m A、100 m A、150 m A、350 m A)对肺结节体模进行扫描,采用滤波反投影(filtered back projection, FBP)、自适应迭代重建(ASIR:30%,50%,80%)算法进行重建,获取28套CT图像。应用肺结节分析软件对3种直径(2.5 mm,5 mm,10 mm)、三种CT值(-100 HU,60 HU,100 HU)共9个球型结节测量容积及平均CT值数据。应用重复测量方差分析评估不同管电流及原始数据重建算法对容积及CT值测量的影响。结果直径为2.5 mm结节的容积测量相对误差(100.8%±28%)及三维CT值绝对误差(-756±80)HU最大;直径为5 mm及10 mm结节的容积相对误差小[(-0.9%±1.1%)vs(0.9%±1.4%)],但CT值绝对误差大[(-243±26)HU vs(-129±7)HU]。针对直径为5 mm及10 mm结节使用重复测量方差分析结果显示,应用不同管电流及原始数据重建算法时容积测量相对误差没有显著性差异(F=5.60,P=0.10 vs F=11.13,P=0.08),三维CT值的绝对误差有显著影响(F=34.79,P<0.001 vs F=156.14,P<0.001)。结论不同管电流及重建算法对直径5mm及10 mm的结节容积定量影响很小,因此较低管电流及迭代重建算法可以应用在5 mm以上肺结节的CT随访中。结节分析软件提供的平均CT值与标准CT值在不同大小、密度结节中均具有较大误差,不能应用于临床。
