Several in vitro and in vivo studies have established accelerated thrombolysis using ultrasound (US) induced microbubble (MB) cavitation. However, the mechanisms underlying MB mediated sonothrombolysis are still not completely elucidated. We performed three-dimensional (3-D) volumetric optical coherence tomography (OCT) imaging before and after the application of contrast US to thrombus. The most dramatic reduction in clot volume was observed with US + MB + recombinant tissue plasminogen activator (rt-PA). Thrombus surface erosion in this group on the side of the thrombus exposed to MB and ultrasound was evident on the OCT images. This technique may assist in clarifying the mechanisms underlying sonothrombolysis, especially regarding the importance of US transducer orientation on lytic efficacy and the effects of MB cavitation on thrombus structure.
We have developed a new image-based guidance system for microsurgery using optical coherence tomography
(OCT), which presents a virtual image in its correct location inside the scanned tissue. Applications include surgery of
the cornea, skin, and other surfaces below which shallow targets may advantageously be displayed for the naked eye or
low-power magnification by a surgical microscope or loupes (magnifying eyewear). OCT provides real-time highresolution
(3 micron) images at video rates within a two or more millimeter axial range in soft tissue, and is therefore
suitable for guidance to various shallow targets such as Schlemm's canal in the eye (for treating Glaucoma) or skin
tumors. A series of prototypes of the "OCT penlight" have produced virtual images with sufficient resolution and
intensity to be useful under magnification, while the geometrical arrangement between the OCT scanner and display
optics (including a half-silvered mirror) permits sufficient surgical access. The two prototypes constructed thus far have
used, respectively, a miniature organic light emitting diode (OLED) display and a reflective liquid crystal on silicon
(LCoS) display. The OLED has the advantage of relative simplicity, satisfactory resolution (15 micron), and color
capability, whereas the LCoS can produce an image with much higher intensity and superior resolution (12 micron),
although it is monochromatic and more complicated optically. Intensity is a crucial limiting factor, since light flux is
greatly diminished with increasing magnification, thus favoring the LCoS as the more practical system.
We use Fourier domain optical coherence tomography (OCT) data to assess retinal blood oxygen saturation. Three-dimensional disk-centered retinal tissue volumes were assessed in 17 normal healthy subjects. After removing DC and low-frequency a-scan components, an OCT fundus image was created by integrating total reflectance into a single reflectance value. Thirty fringe patterns were sampled; 10 each from the edge of an artery, adjacent tissue, and the edge of a vein, respectively. A-scans were recalculated, zeroing the DC term in the power spectrum, and used for analysis. Optical density ratios (ODRs) were calculated as ODRArt=ln(Tissue855/Art855)/ln(Tissue805/Art805) and ODRVein=ln(Tissue855/Vein855)/ln(Tissue805/Vein805) with Tissue, Art, and Vein representing total a-scan reflectance at the 805- or 855-nm centered bandwidth. Arterial and venous ODRs were compared by the Wilcoxon signed rank test. Arterial ODRs were significantly greater than venous ODRs (1.007±2.611 and −1.434±4.310, respectively; p=0.0217) (mean±standard deviation). A difference between arterial and venous blood saturation was detected. This suggests that retinal oximetry may possibly be added as a metabolic measurement in structural imaging devices.