Columbia University Medical Center, New York, NY 10032, USA.
Invest Ophthalmol Vis Sci. 2013 Jan 10;54(1):103-9. doi: 10.1167/iovs.12-10773.
While visualization of the retina and choroid has made great progress, functional imaging techniques have been lacking. Our aim was to utilize acoustic radiation force impulse (ARFI) response to probe functional properties of these tissues.
A single element 18-MHz ultrasound transducer was focused upon the retina of the rabbit eye. The procedure was performed with the eye proptosed and with the eye seated normally in the orbit. The transducer was excited to emit ARFI over a 10-ms period with a 25% duty cycle. Phase resolved pulse/echo data were acquired before, during, and following ARFI.
In the proptosed eye, ARFI exposure produced tissue displacements ranging from 0 to 10 μm, and an immediate increase in choroidal echo amplitude to over 6 dB, decaying to baseline after about 1 second. In the normally seated eye, ultrasound phase shifts consistent with flow were observed in the choroid, but enhanced backscatter following ARFI rarely occurred. ARFI-induced displacements of about 10 μm were observed at the choroidal margins. Larger displacements occurred within the choroid and in orbital tissues.
We hypothesize that elevated intraocular pressure occurring during proptosis induced choroidal ischemia and that acoustic radiation force produced a transient local decompression and reperfusion. With the eye normally seated, choroidal flow was observed and little alteration in backscatter resulted from exposure. Clinical application of this technique may provide new insights into diseases characterized by altered choroidal hemodynamics, including maculopathies, diabetic retinopathy, and glaucoma.
尽管视网膜和脉络膜的可视化已经取得了很大进展，但功能成像技术仍一直缺乏。我们的目的是利用声辐射力脉冲（ARFI）响应来探测这些组织的功能特性。
将单个 18MHz 超声换能器聚焦于兔眼的视网膜上。该过程在眼球突出和眼球正常位于眼眶中两种情况下进行。换能器以 25%的占空比发射持续 10ms 的 ARFI。在 ARFI 之前、期间和之后采集相分辨脉冲/回波数据。
在突出的眼睛中，ARFI 暴露产生的组织位移范围为 0 至 10μm，脉络膜回波幅度立即增加超过 6dB，并在大约 1 秒后衰减至基线。在正常坐立的眼睛中，在脉络膜中观察到与流动一致的超声相位移动，但很少发生 ARFI 后的增强反向散射。在脉络膜边缘观察到约 10μm 的 ARFI 诱导位移。更大的位移发生在脉络膜和眼眶组织中。
我们假设在眼球突出期间发生的眼内压升高导致脉络膜缺血，而声辐射力产生了短暂的局部减压和再灌注。在眼球正常坐立时，观察到脉络膜流动，并且暴露后反向散射几乎没有变化。该技术的临床应用可能为以改变的脉络膜血液动力学为特征的疾病提供新的见解，包括黄斑病变、糖尿病性视网膜病变和青光眼。
