Van Houten J P, Benaron D A, Spilman S, Stevenson D K
Stanford Medical Spectroscopy and Imaging Laboratory, Division of Neonatal and Developmental Medicine, Stanford University, Palo Alto, California 94304, USA.
Pediatr Res. 1996 Mar;39(3):470-6. doi: 10.1203/00006450-199603000-00015.
Conventional brain imaging modalities are limited in that they image only secondary physical manifestations of brain injury, which may occur well after the actual insult to the brain and represent irreversible structural changes. A real-time continuous bedside monitor that images functional changes in cerebral blood flow or oxygenation might allow for recognition of brain tissue ischemia or hypoxia before the development of irreversible injury. Visible and near infrared light pass through human bone and tissue in small amounts, and the emerging light can be used to form images of the interior structure of the tissue and measure tissue blood flow and oxygen utilization based on light absorbance and scattering. We developed a portable time-of-flight and absorbance system which emits pulses of near infrared light into tissue and measures the transit time of photons through the tissue. Images can then be reconstructed mathematically using either absorbance or scattering information. Pathologic brain specimens from adult sheep and human newborns were studied with this device using rotational optical tomography. Images generated from these optical scans show that neonatal brain injuries such as subependymal and intraventricular hemorrhages can be successfully identified and localized. Resolution of this system appears to be better than 1 cm at a tissue depth of 5 cm, which should be sufficient for imaging some brain lesions as well as for detection of regional changes in cerebral blood flow and oxygenation. We conclude that light-based imaging of cerebral structure and function is feasible and may permit identification of patients with impending brain injury as well as monitoring of the efficacy of intervention. Construction of real-time images of brain structure and function is now underway using a fiber optic headband and nonmechanical rotational scanner allowing comfortable, unintrusive monitoring over extended periods of time.
传统的脑成像方式存在局限性，因为它们仅对脑损伤的继发性物理表现进行成像，而这些表现可能在对大脑的实际损伤发生很久之后才出现，并且代表着不可逆的结构变化。一种能够对脑血流或氧合的功能变化进行成像的实时连续床边监测仪，或许可以在不可逆损伤发生之前识别脑组织缺血或缺氧情况。可见光和近红外光能够少量穿透人体骨骼和组织，出射光可用于形成组织内部结构的图像，并基于光吸收和散射来测量组织血流和氧利用情况。我们开发了一种便携式飞行时间和吸收系统，该系统向组织发射近红外光脉冲，并测量光子在组织中的传播时间。然后可以使用吸收或散射信息通过数学方法重建图像。使用旋转光学断层扫描技术，用该设备对成年绵羊和人类新生儿的病理性脑标本进行了研究。这些光学扫描生成的图像表明，诸如室管膜下和脑室内出血等新生儿脑损伤能够被成功识别和定位。在5厘米的组织深度下，该系统的分辨率似乎优于1厘米，这对于成像一些脑损伤以及检测脑血流和氧合的区域变化应该是足够的。我们得出结论，基于光的脑结构和功能成像具有可行性，可能有助于识别即将发生脑损伤的患者以及监测干预效果。目前正在使用光纤头带和非机械旋转扫描仪构建脑结构和功能的实时图像，以便能够长时间进行舒适、非侵入性的监测。
