FRACTAL NATURE OF REGIONAL MYOCARDIAL BLOOD-FLOW HETEROGENEITY
FRACTAL NATURE OF REGIONAL MYOCARDIAL BLOOD-FLOW HETEROGENEITY
复制标题
DOI：
10.1161/01.res.65.3.578
复制
发表时间：
1989-09-01
影响因子：
20.1
通讯作者：
ROGER, SA
中科院分区：
文献类型：
--
作者：
BASSINGTHWAIGHTE, JB;KING, RB;ROGER, SA
即使使用低分辨率技术，也可以测量心脏、骨骼肌和其他器官内区域血流的空间变化以及局部小动脉速度和血流的时间变化。在评估这种变化的重要性时存在的一个问题是，观测到的变化随着测量中空间或时间分辨率的增加而增加。这种与分辨率相关的方差现在可以用分形维数d来描述。例如，给定空间分辨率下流量空间分布的相对弥散度（RD = SD/mean）为：RD(m)=RD(mref) .cntdot。[m/mref]1- ds，其中m为组织块的质量，单位为克，参考色散水平RD（mref）被任意取为使用质量块mref得到的RD，选择为1 g。因此，器官内区域流量的变化可以用两个参数来描述，RD（mref）和由空间分形维数Ds定义的对数关系的斜率。在心脏中，这种关系被发现在很宽的片尺寸范围内成立，分形Ds约为1.2，相关系数为0.99。若Ds为1.2，则表明局部流量相关性较强；Ds = 1.0表示均匀流动，Ds = 1.5表示完全随机。
Spatial variation in regional flows within the heart, skeletal muscle, and in other organs, and temporal variations in local arteriolar velocities and flows is measurable even with low resolution techniques. A problem in the assessment of the importance of such variations has been that the observed variance increases with increasing spatial or temporal resolution in the measurements. This resolution-dependent variance is now shown to be described by the fractal dimension, D. For example, the relative dispersion (RD = SD/mean) of the spatial distribution of flows for given spatial resolution, is given by: RD(m)=RD(mref) .cntdot. [m/mref]1-Ds where m is the mass of the pieces of tissue in grams, and the reference level of dispersion, RD(mref), is taken arbitrarily to be the RD found using pieces of mass mref, which is chosen to be 1 g. Thus, the variation in regional flow within an organ can be described with two parameters, RD(mref) and the slope of the logarithmic relationship defined by the spatial fractal dimension Ds. In the heart, this relation has been found to hold over a wide range of piece sizes, the fractal Ds being about 1.2 and the correlation coefficient 0.99. A Ds of 1.2 suggests moderately strong correlation between local flows; a Ds = 1.0 indicates uniform flow and a Ds = 1.5 indicates complete randomness.