OPTOACOUSTIC MONITORING OF CEREBRAL BLOOD OXYGENATION

监测脑氧合在急性、危及生命的神经系统疾病，包括严重的创伤性脑损伤的管理中提供了巨大的希望。迄今为止，用于监测脑氧合的两种主要方法都是侵入性的——一种需要经皮将导管插入颈静脉球以连续测量脑静脉氧合，另一种需要将探针通过颅骨插入脑实质以测量组织PO2。第一种技术需要经常重新校准。第二种不能表明在偏远地区组织氧合不足。近红外光谱是监测脑血氧的第三种无创方法，它很有前景，但还没有令人满意的校准来提供定量测量。因此，目前还没有准确、无创、连续监测脑血氧的系统。我们提出了一种新的技术，该技术将利用近红外光谱范围内氧和脱氧血红蛋白的光学吸收系数的既定差异来准确监测血液氧合。该项目的目的是测试一种新的光声技术，直接从上矢状窦（SSS）测量脑静脉氧合的绝对值，由于光声技术的高分辨率，该结构可以定位。光声技术是基于激光脉冲产生超声波，并通过灵敏的声换能器检测这些波。我们的初步研究表明：(1)超声波的振幅和时间分布与血氧呈线性关系；(2)使用特殊设计的换能器，尽管光学和声学受到厚骨的衰减，但仍然可以进行灵敏的检测；(3)该技术可以高精度地测量血氧。本项目的具体目的是：(1)评估体外反向模式下的光声血氧监测；(2)评价羊体内后向模式血氧的光声监测。性能将在正常绵羊和实验模型中进行评估，这些模型在绵羊中复制典型的严重静脉去饱和条件。

Monitoring cerebral oxygenation offers great promise in the management of acute, life-threatening neurologic illnesses, including severe traumatic brain injury. To date, the two primary methods used to monitor brain oxygenation are invasive- one requires percutaneous insertion of a catheter into the jugular bulb to continuously measure cerebral venous oxygenation and the other requires insertion of a probe through the skull into the brain parenchyma to measure tissue PO2. The first technique requires frequent recalibration. Second one cannot indicate inadequate tissue oxygenation in remote sites. Near- infrared spectroscopy, a third, noninvasive method of monitoring cerebral blood oxygenation, is promising, but has yet to be satisfactorily calibrated to provide quantitative measurement. Therefore, at present there is no system for accurate, non- invasive, and continuous monitoring of cerebral blood oxygenation. We propose a novel technique that will utilize well-established differences in optical absorption coefficients of oxy- and deoxyhemoglobin in the near-infrared spectral range to accurately monitor blood oxygenation. The objective of this project is to test a novel optoacoustic technique to measure the absolute value of cerebral venous oxygenation directly from the superior sagittal sinus (SSS), a structure that can be localized due to the high resolution of the optoacoustic technique. The optoacoustic technique is based on generation of ultrasonic waves by laser pulses and detection of these waves by a sensitive acoustic transducer. Our preliminary studies demonstrate that (1) the amplitude and temporal profile of the ultrasonic waves are linearly dependent on blood oxygenation; (2) the use of specially designed transducers allows sensitive detection despite optical and acoustic attenuation by thick bone; and (3) this technique will measure blood oxygenation with high accuracy. The specific aims of the project are: (1) to evaluate optoacoustic monitoring of blood oxygenation in backward mode in vitro in phantoms; and (2) to evaluate optoacoustic monitoring of blood oxygenation in backward mode in vivo in sheep. Performance will be evaluated in normal sheep and in experimental models in sheep that replicate conditions typical of severe venous desaturation.