Khan Bilal, Wildey Chester, Francis Robert, Tian Fenghua, Delgado Mauricio R, Liu Hanli, Macfarlane Duncan, Alexandrakis George
Biomed Opt Express. 2012 May 1;3(5):878-98. doi: 10.1364/BOE.3.000878. Epub 2012 Apr 6.
A novel brush optode was designed and demonstrated to overcome poor optical contact with the scalp that can occur during functional near infrared spectroscopy (fNIRS) and imaging due to light obstruction by hair. The brush optodes were implemented as an attachment to existing commercial flat-faced (conventional) fiber bundle optodes. The goal was that the brush optodes would thread through hair and improve optical contact on subjects with dense hair. Simulations and experiments were performed to assess the magnitude of these improvements. FNIRS measurements on 17 subjects with varying hair colors (blonde, brown, and black) and hair densities (0-2.96 hairs/mm(2)) were performed during a finger tapping protocol for both flat and brush optodes. In addition to reaching a study success rate of almost 100% when using the brush optode extensions, the measurement setup times were reduced by a factor of three. Furthermore, the brush optodes enabled improvements in the activation signal-to-noise ratio (SNR) by up to a factor of ten as well as significant (p < 0.05) increases in the detected area of activation (dAoA). The measured improvements in SNR were matched by Monte Carlo (MC) simulations of photon propagation through scalp and hair. In addition, an analytical model was derived to mathematically estimate the observed light power losses due to different hair colors and hair densities. Interestingly, the derived analytical formula produced excellent estimates of the experimental data and MC simulation results despite several simplifying assumptions. The analytical model enables researchers to readily estimate the light power losses due to obstruction by hair for both flat-faced fiber bundles and individual fibers for a given subject.
设计并展示了一种新型刷状光极，以克服在功能近红外光谱（fNIRS）和成像过程中因头发遮挡光线而导致的与头皮光学接触不良的问题。刷状光极被设计为现有商用平面（传统）光纤束光极的附件。目标是刷状光极能够穿过头发，改善对头发浓密的受试者的光学接触。进行了模拟和实验来评估这些改善的程度。在手指轻敲实验中，对17名具有不同发色（金色、棕色和黑色）和头发密度（0 - 2.96根/平方毫米）的受试者使用平面光极和刷状光极进行了fNIRS测量。使用刷状光极扩展时，除了研究成功率几乎达到100%外，测量设置时间减少了三分之一。此外，刷状光极使激活信号噪声比（SNR）提高了高达10倍，并且激活检测面积（dAoA）显著（p < 0.05）增加。通过光子在头皮和头发中传播的蒙特卡罗（MC）模拟，验证了测量得到的SNR改善情况。此外，还推导了一个分析模型，以数学方式估计由于不同发色和头发密度导致的光功率损失。有趣的是，尽管有几个简化假设，但推导的分析公式对实验数据和MC模拟结果的估计非常出色。该分析模型使研究人员能够轻松估计给定受试者的平面光纤束和单根光纤因头发遮挡而导致的光功率损失。
