Instrumentation Center (GEI-CI), Physics Department, Faculty of Sciences and Technology of Coimbra University, Coimbra, Portugal.
Med Biol Eng Comput. 2013 Feb;51(1-2):103-12. doi: 10.1007/s11517-012-0973-x. Epub 2012 Oct 12.
Measuring functional activity in brain in connection with neural stimulation faces technological challenges. Our goal is to evaluate, in relative terms, the real-time variations of local cerebral blood flow in rat brain, with a convenient spatial resolution. The use of laser Doppler flowmetry (LDF) probes is a promising approach but commercially available LDF probes are still too large (450 μm) to allow insertion in brain tissue without causing damage in an extension that may negatively impact local measurements. The self-mixing technique coupled to LDF is herein proposed to overcome limitations of the minimal diameter of the probe imposed by non-self-mixing probes (commercial available probes). Our Monte Carlo simulations show that laser photons have a mean penetration depth of 0.15 mm, on the rat brain with the 785 nm laser light microprobe. Moreover, three self-mixing signal processing methods are tested: counting method, autocorrelation method, power spectrum method. The perfusion signal computed shows a good linearity with the scatterers velocity, for the three methods (a determination coefficient close to one is obtained), for the in vitro measurements. Furthermore, we believe that these indicators can be used to monitor local blood flow changes in the rat brain.
测量与神经刺激相关的大脑功能活动面临着技术挑战。我们的目标是评估大鼠大脑局部脑血流的实时变化，具有方便的空间分辨率。激光多普勒流量测量（LDF）探头的使用是一种很有前途的方法，但商用的 LDF 探头仍然太大（450μm），以至于不能在不造成损伤的情况下插入脑组织，这种插入可能会对局部测量产生负面影响。本文提出了将自混合技术与 LDF 相结合，以克服非自混合探头（商用探头）对探头最小直径的限制。我们的蒙特卡罗模拟表明，在大鼠大脑中，785nm 激光微探头的激光光子平均穿透深度为 0.15mm。此外，我们测试了三种自混合信号处理方法：计数法、自相关法、功率谱法。对于这三种方法（都得到了接近 1 的决定系数），体外测量得到的灌注信号与散射体速度具有很好的线性关系。此外，我们认为这些指标可用于监测大鼠大脑局部血流的变化。
