It can be used in real time situation . for the second type , the blood flow ' s speed is very high ( fig . 3 . 5 ) . average speed of a frame can be measured using fft 第二类血管内的血液流速很高(见图3 . 5 ) ,看不清细胞,本文用傅立叶变换,可以求出每帧血液的流速。
The edge of a group of blood is visible and easy to track . there is little distortion of the shape of a group of blood between two frames . there are many methods to measure blood velocity such as optical flow techniques [ 40 , 44 , 45 ] , using fluorescent images [ 42 ] , template matching method [ 17 ] and so on [ 43 ] 大血管的情况复杂一些,第一类血管的血液和周围的组织都很复杂(见图3 . 1 ) ,这类血管有些血液和组织还很相似,特征是流速比较低,细胞团块边缘清晰,在一定时间内的形变较小,本文用模板匹配法,较好的测量出这类血液的流速。