Doshisha University, Kyotanabe, Japan.
Nara Medical University, Kashihara, Japan.
Sci Rep. 2021 Sep 2;11(1):17592. doi: 10.1038/s41598-021-96502-5.
The transcranial Doppler method (TCD) enables the measurement of cerebral blood flow velocity and detection of emboli by applying an ultrasound probe to the temporal bone window, or the orbital or greater occipital foramina. TCD is widely used for evaluation of cerebral vasospasm after subarachnoid hemorrhage, early detection of patients with arterial stenosis, and the assessment of brain death. However, measurements often become difficult in older women. Among various factors contributing to this problem, we focused on the effect of the diploe in the skull bone on the penetration of ultrasound into the brain. In particular, the effect of the cancellous bone structure in the diploe was investigated. Using a 2D digital bone model, wave propagation through the skull bone was investigated using the finite-difference time-domain (FDTD) method. We fabricated digital bone models with similar structure but different BV/TV (bone volume/total volume) values in the diploe. At a BV/TV of approximately 50-60% (similar to that of older women), the minimum ultrasound amplitude was observed as a result of scattering and multiple reflections in the cancellous diploe. These results suggest that structural changes such as osteoporosis may be one factor hampering TCD measurements.
经颅多普勒（TCD）方法通过将超声探头应用于颞骨窗、眶或枕大孔来测量脑血流速度和检测栓子。TCD 广泛用于评估蛛网膜下腔出血后的脑血管痉挛、早期发现动脉狭窄患者以及评估脑死亡。然而，在老年女性中，测量往往变得困难。在导致这一问题的各种因素中，我们关注颅骨板障对超声穿透大脑的影响。特别是，研究了板障中松质骨结构的影响。使用二维数字骨骼模型，我们采用时域有限差分（FDTD）方法研究了颅骨中的波传播。我们制作了具有相似结构但板障中骨体积/总体积（BV/TV）值不同的数字骨骼模型。在 BV/TV 约为 50-60%（类似于老年女性）时，由于松质板障中的散射和多次反射，观察到最小的超声幅度。这些结果表明，结构变化（如骨质疏松症）可能是阻碍 TCD 测量的一个因素。
