Department of Radiological Sciences, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.
Magn Reson Med. 2010 Apr;63(4):910-21. doi: 10.1002/mrm.22274.
The blood oxygenation level dependent signal of cerebral tissue can be theoretically derived using a network model formed by randomly oriented infinitely long cylinders. The validation of this model by phantom and in vivo experiments is still an object of research. A network phantom was constructed of solid polypropylene strings immersed in silicone oil, which essentially eliminated the effect of spin diffusion. The volume fraction and magnetic property of the string network was predetermined by independent methods. Ten healthy volunteers were measured for in vivo demonstration. The gradient echo sampled spin echo signal was evaluated with the cylinder network model. We found a strong interdependency between the two network characterizing parameters deoxygenated blood volume and oxygen extraction fraction. Here, different sets of deoxygenated blood volume/oxygen extraction fraction values were able to describe the measured signal equally well. However, by setting one parameter constant to a predetermined value, reasonable estimates of the other parameter were obtained. The same behavior was found for the in vivo demonstration. The signal theory of the cylinder network was validated by a well-characterized phantom. However, the found interdependency that was found between deoxygenated blood volume and oxygen extraction fraction requires an independent estimation of one variable to determine reliable values of the other parameter.
脑组织血氧水平依赖信号可以通过由随机取向的无限长圆柱体组成的网络模型理论上推导出来。该模型通过体模和体内实验进行验证仍然是一个研究对象。使用浸入硅油中的固体聚丙烯线构建了网络体模，这实质上消除了自旋扩散的影响。通过独立的方法预先确定了字符串网络的体积分数和磁性质。对 10 名健康志愿者进行了体内演示测量。使用圆柱网络模型评估梯度回波采样自旋回波信号。我们发现两个网络特征参数去氧血红蛋白体积和氧提取分数之间存在很强的相关性。在这里，可以使用不同的去氧血红蛋白体积/氧提取分数值集来同样很好地描述测量信号。但是，通过将一个参数设置为预定值，就可以获得另一个参数的合理估计值。体内演示也表现出相同的行为。圆柱网络的信号理论通过一个特征良好的体模得到了验证。然而，发现去氧血红蛋白体积和氧提取分数之间存在相关性，这需要对一个变量进行独立估计，以确定另一个参数的可靠值。
