RETINAL BLOOD FLOW MEASUREMENT

可以使用激光触发的脂质体封装的荧光染料 作为眼睛的示踪剂。 荧光素广泛用于眼科 诊断，但必须局部应用或注射 静脉内，导致染料通过 视网膜循环沿着高水平的背景 脉络膜中的荧光。 羧基荧光素和钙黄绿素染料 类似于荧光素，可以以较高浓度包封在脂质体中， 浓度（100 mM）。 在如此高的浓度下， 荧光被淬灭，但当染料从荧光中释放出来时， 脂质体，它被稀释并发出强烈的荧光。 脂质体 含有这些荧光染料的药物可以静脉注射， 一旦进入流通领域， 通过激光器发出的局部光脉冲。 染料将 激光转化为热量，从而提高脂质体的温度， 包封，溶解脂质体，并释放染料。 的能力 为了控制染料释放的位置、定时和重复， 允许局部流动模式在没有背景的情况下可视化 脉络膜循环或邻近血管的 网络. 系统将评估局部灌注 可能存在缺陷。 创造一个更清晰的波前， 通过生成推注实现，为 流量的定量测量。 通过控制 染料从脂质体中的释放和 记录，我们已经能够在初步研究中测量 在体外的血液速度，以及在视网膜血管中， 兔子和猴子 此外，重复的可能性 程序允许细化的对齐和聚焦的 相机，从而优化照片的质量。 此外，测量可以在 引起生理条件的变化（即，氧或氮 呼吸、暴露于光或药物制剂）。 的 系统提供了时间，位置和重复的控制， 交付，这可能是有用的，在一些 治疗应用也是如此。

Laser-triggered, lipsome-encapsulated fluorescent dyes can be used as a tracer in the eye. Fluorescein is widely used in ophthalmic diagnosis, but it must be applied topically or injected intravenously, resulting in diffuse spread of dye through the retinal circulation along with high levels of background fluorescence in the choroid. Carboxyfluorescein and calcein, dyes similar to fluorescein, can be encapsulated in liposomes at high concentrations (100 mM). At such elevated concentrations, the fluorescence is quenched, but when the dye is released from the liposome, it is diluted and fluoresces intensely. Liposomes containing these fluorescent dyes can be injected intravenously and once in the circulation, can be trigged to release their contents by a localized pulse of light from a laser. The dye converts the laser into heat, which raises the temperature of the liposomal envelope, lyses the liposome, and releases the dye. The ability to control location, timing, and repetition of dye release would allow local flow patterns to be visualized without the background of the underlying choroidal circulation or adjacent vessel networks. The system will make assessment of localized perfusion defects possible. The creation of a better defined wavefront, achieved with the generation of a bolus, opens the way for quantitative measurement of flow. By controlling the time between the release of the dye from the liposomes and the time of recording, we have been able in preliminary studies to measure the velocity of blood in vitro, as well as in the retinal vessels of rabbits and monkeys. Moreover, the possibility of repeating the procedure allows refinement of alignment and focusing of the camera, thereby optimizing the quality of the photographs. Additionally, measurements can be performed before and after induced changes of physiologic conditions (i.e., oxygen or nitrogen breathing, exposure to light or pharmacological agents). The system offers the control of time, location, and repetition of delivery, which potentially will be useful in a number of therapeutic applications as well.