Hardy P A, Kucharczyk W, Henkelman R M
Ontario Cancer Institute, Toronto, Canada.
Radiology. 1990 Feb;174(2):549-55. doi: 10.1148/radiology.174.2.2296664.
Old hemorrhagic lesions in the brain are characteristically surrounded by a band of hemosiderin-containing tissue. This region is typically of low signal intensity on long-echo-time (TE) radio-frequency (RF) spin-echo magnetic resonance (MR) images and on gradient-echo MR images. To determine the cause of signal loss in this band, the authors measured the signal that arises from imaging such a region with use of an RF spin-echo technique with a 180 degrees pulse incrementally displaced from TE/2. The incremental loss of signal was small. Using an agar phantom containing iron particles, the authors also showed that signal loss results primarily from diffusion in magnetic gradients. They conclude that most signal loss in the dark band surrounding areas of late-stage hemorrhage arises from diffusion in areas of magnetic inhomogeneity.
脑内陈旧性出血性病变的特征是被一圈含铁血黄素的组织所环绕。在长回波时间（TE）射频（RF）自旋回波磁共振（MR）图像以及梯度回波MR图像上，该区域通常呈低信号强度。为了确定此带信号丢失的原因，作者使用射频自旋回波技术，在180°脉冲从TE/2开始逐渐位移的情况下，对这样一个区域进行成像，测量所产生的信号。信号的增量丢失很小。作者还使用含有铁颗粒的琼脂模型表明，信号丢失主要是由磁梯度中的扩散所致。他们得出结论，晚期出血区域周围暗带中的大部分信号丢失是由磁不均匀区域中的扩散引起的。
