目的 探讨血流变化对肺部MRI信号的影响，并研究1种新的MR肺血流灌注成像方法。方法 对健康志愿者15例，采用相位对比电影MRI技术测量大肺动脉血流速度和流量在心动周期内的变化；并选用单次激发半傅立叶变换超快速自旋回波序列观察肺实质MR信号的相应改变，评价其相关性；根据不同心动期相肺实质MR 信号的差异进行图像减影。结果　肺实质MRI 信号表现为心脏收缩期降低，舒张期升高。大肺动脉的瞬时速度、瞬时流量与其呈负相关（r=-0.878、-0.770，P=0.002、0.015) 。经肺部MRI信号差异最大的舒张末期和收缩中期的MRI减影可获得肺灌注像。结论 肺实质MRI信号的改变与肺血流模式和速度有关。该技术是1种简便易行的非对比剂性的MR肺灌注评价新方法。

目的　利用影像学手段采用分支几何学方法探索在活体状态下肺小血管的分支特征。方法　通过对63 例正常胸部螺旋CT扫描图像，采用分支几何学方法对2 008套肺血管两分支状血管分支点两侧的血管横径进行测量，计算扩张因子和不对称因子，分析其特征及与母支直径的相关关系。结果　活体状态下两因子与标本数据存在差异；扩张因子均值为1.0022，不对称因子中位数为1.4938，分别与母支横径呈线性负、正相关，这一趋势在母支横径小于4.0mm时最为明显。母支横径大于6.0 mm时，不对称因子分布趋势不明显。母支横径为2.5mm时，扩张因子迅速降至1.622，而不对称因子降至1.500左右。结论　用分支几何学方法研究肺小血管的分支特征，对认识肺血管的分支形态特点，建立血流和压力的数学及物理模型有潜在理论和实用价值。

AIM: To cxplore the diagnostic effect of pulmonary ventilation-perfnsionfMRI for pulmonary embolism(PE).METMODS: Gelatin sponge was intraduced into the left fewer lobar pal-monary arteries of 4 dogs through catheter under distal subtraction an#ag-raphy(DSA) so as to establish PE model. Before PE, the dogs inhaled roomair(21%O2) and 99.5%02 respectively and inhaled 99.5% 02 again afterPE. Then MRI scanning was performed for pulmonatT ventilation. The signalintersitites (SI) of left lower lobe wore meesured and its variation was oh-sexved. The dogs were undergone MRI scanning before and efiex PE to ob-serve the perfusion of ]eft lower lobe.RESULTS: Both before and ofter PE the SI of left lower lobe after inhalationof 99.5% O2 increased significantly much more than after inhalation of indoorair. However, there was no significant difference in the increase of SI valuehctween the emhollc left lower lobe and non-mhdiio region of the right lowerlobe (t=3.685, P>0.05), indicating that pulmonary ventilation was notinfluenced in the emholic region of left lower loho. During perfusion MRscanning and after injection of contrast media, the SI of non-embelic re#on inthe fight lower lobe rapidly inched and reached the peak 6.8 aconds atinrinjection of contrast media. Bm the time-signal intensity curve of die embeficregion of left fower lube rpmained at lower level and had no apparont peakvalue all the time. CONCLUSION: Oxygen-enhanced ventilation fMRI combining pexlnsionfMRI provide a new diagnostic means for PE. The method is feasible andbeneficial for PE diagnosis.

AIM: To mea sure the flowvolume of pulmonary arteries by using pha se-contra st magnetic re sonance imaging(MRI) and to inve stigate the values of pha se-contrast MRI ina sse ssing pulmonary perfusion. METHODS: Pha se-contra stMRI was performed in 20 healthy volunteers by Philips Gy-roscan NT 1. 5TMR scanner. The flow rates of main pulmonaryartery (MPA), right pulmonary artery (RPA) and left pul-monary artery (LPA) of different cardiac phases in one cardiaccycle were mea sured and the flow volumes were calculated.RESULTS: The flow volumes of MPA, RPA and LPA were (73.5