Microvascular contrast enhancement in optical coherence tomography using microbubbles

Abstract

Gas microbubbles (MBs) are investigated as intravascular optical coherence tomography (OCT) contrast agents. Agar + intralipid scattering tissue phantoms with two embedded microtubes were fabricated to model vascular blood flow. One was filled with human blood, and the other with a mixture of human blood + MB. Swept-source structural and speckle variance (sv) OCT images, as well as speckle decorrelation times, were evaluated under both no-flow and varying flow conditions. Faster decorrelation times and higher structural and svOCT image contrasts were detected in the presence of MB in all experiments. The effects were largest in the svOCT imaging mode, and uniformly diminished with increasing flow velocity. These findings suggest the feasibility of utilizing MB for tissue hemodynamic investigations and for microvasculature contrast enhancement in OCT angiography.

Preclinical quantitative in-vivo assessment of skin tissue vascularity in radiation-induced fibrosis with optical coherence tomography

“…40 The interframe B-scan acquisition rate was chosen to be 25 ms (suitable for stationary tissue speckle to remain correlated between frames, while ensuring complete interframe decorrelation of vascular blood pixels). 41 Animals were kept in microisolator cages with access to food and water ad libitum for 6 months after irradiation prior to OCT imaging. Mice were anesthetized by inhalation of 2% isoflurane and placed under the OCT imaging probe on a heating pad to maintain physiological temperature during imaging procedures.…”

Analysis of low-scattering regions in optical coherence tomography: applications to neurography and lymphangiography

“…It is important to note here, that although the number of 1080 pixels per ROI was considered to be sufficient to detect structures of interest, these 1080 statistical samples of the speckle distribution per small analysis volume may not be fully independent at OCT's frame rate of 40 Hz and the resultant inter-frame temporal spacing of 25 ms. In our earlier in-vivo experiments [42,43] we explored the range of OCT signal decorrelation times for blood, tumor and normal tissues. For blood, decorrelation times were found to range from ∼20 ms (0.5 mm/s flow rate in small vessels like capillaries) to ∼1 ms (>12 mm/s flow rate in larger vessels); tumor and normal tissues had much longer decorrelation times reaching ∼500 ms and 1.1s (skin), respectively.…”

Can OCT Angiography Be Made a Quantitative Blood Measurement Tool?

“…If a more isotropically scattering contrast agent such as Intralipid ® [ 89 , 90 ] is used, angiograms derived from the contrast agent signal alone do not suffer from multiple scattering tails [ 89 , 90 ]. Microbubbles [ 91 , 92 ] are promising for enhancing intravascular scattering signals, and may present more well-defined decorrelation characteristics than blood. Moreover, if the contrast agent behaves like plasma and the signal can be calibrated and related to concentration [ 89 , 90 ], plasma flow, transit time, and volume can all be measured.…”