激光散斑血流成像系统中的光源相干性

Source coherence in laser speckle blood imaging system

针对激光散斑血流成像系统中光源相干性对散斑衬比的影响进行了研究,提出了一种基于混合遗传算法的散斑图像恢复方案。首先,分析非完全相干光用于激光散斑血流成像系统时的劣势,说明混合遗传算法恢复被低相干性光源破坏的散斑图像的原理;使用对比度与噪声比来衡量由两种光源成像得到的静态白盘散斑图像质量;最后,将算法分别用于静态白盘散斑图像和真实的手背血流检测场景。实验结果表明,相干性较好的单纵模激光器成像得到的散斑图像,较之于相干性较差的半导体激光器成像得到的散斑图像,对比度与噪声比高出67.2%;将算法用于质量较差的散斑图像后,其对比度与噪声比提高了57.7%;将算法用于手背血流检测场景,进行恢复运算后,验证了手指指尖的血流灌注量平均高于手指关节30%的临床事实。将本算法用于激光散斑血流成像系统,可以有效消除非完全相干光给散斑衬比分析造成的影响,获得质量更好的血流图像。本算法的推广使用可以提高激光散斑血流仪器在光源选择方面的灵活性。

This study investigated the influence of the light source coherence in a laser speckle blood imaging system on speckle contrast analysis.Therefore,a speckle image restoration scheme based on a hybrid genetic algorithm was proposed.First,the disadvantages of using finite coherent lasers in a laser speckle blood imaging system were analyzed and the principle of a hybrid genetic algorithm used to restore speckle images destroyed by a finite coherent laser was explained.Then,the Contrast to Noise Ratio(CNR)was used to measure the quality of static white disk images from two laser sources.Finally,to verify the effectiveness of the algorithm,it was applied to the speckle image of a disk and the real blood flow detection scene on the back of a hand.Compared with the CNR of the speckle images obtained by a diode laser with low coherence,the CNR of those obtained by a single longitudinal mode laser with good coherence was 67.2%higher.When the algorithm was applied to a speckle image of poor quality,the CNR is improved by 57.7%.When it was applied to the blood flow detection scene on the back of a hand that had undergone a restoration operation,the clinical fact that the blood perfusion index of the fingertip was 30%higher than that of the finger joint was accurately measured.When the algorithm was applied to a laser speckle blood imaging system,the effect of the finite coherent laser on speckle contrast analysis could be effectively eliminated,facilitating the procurement of better blood flow images.Further popularization of this method could improve the flexibility of laser speckle blood flow instruments in laser source selection,which has certain application value.