Optical Scattering Properties of Intralipid Phantom in Presence of Encapsulated Microbubbles

Abstract

In imaging, contrast agents are utilized to enhance sensitivity and specificity of diagnostic modalities. In ultrasound imaging, microbubbles (MBs)—a gas-core shell-encapsulated agent—are used clinically as contrast agents. The working hypothesis of this study is that microbubbles can be employed as an intravascular contrast agent in optical imaging systems. In this work, the interaction of light and microbubbles in a turbid medium (intralipid) was investigated, particularly, the effect of MBs on the reduced scattering and absorption coefficients. Diffuse reflectance (DR) and total transmittance (TT) measurements of highly scattering intralipid suspension (0.5–5%) were measured using spectroscopic integrating sphere system in the absence and presence of Definity microbubbles. The optical properties were computed using the inverse adding doubling (IAD) software. The presence of microbubbles increased DR and decreased TT of intralipid phantoms. In the presence of MBs (0.5% volume concentration), the reflectance of the intralipid phantom increased from 35% to 100%. The reduced scattering coefficient increased significantly (30%) indicating potential use of MBs as optical contrast agents in light based modalities.

Internal-illumination photoacoustic computed tomography

“…The reduced scattering coefficient of the phantom was ∼7 cm −1 at 532 nm. 23,24 A CMOS camera was used to capture the illumination at both wavelengths. Then, we performed phantom experiments to characterize the PACT system with internal illumination.…”

Microvascular contrast enhancement in optical coherence tomography using microbubbles

“…17,18 In addition to the high resolution svOCT imaging of microvasculature, it has potential to provide new insight into the dynamics of vascular remodeling. [19][20][21] In our previous phantom study, 11 we demonstrated that MBs can be used as an optical contrast agent, yielding increased scattering (1.4× at 300 nm and 6× at 850 nm). Similarly, Barton et al 10 have shown that MBs enhanced the backscattered OCT signal in model scattering media.…”

“…8 In light of these drawbacks, microbubbles [MBs; currently Food and Drug Administration (FDA) approved intravascular contrast agents in diagnostic ultrasound 9 ] may have a role to play as OCT contrast agents. 10,11 MBs are micrometer sized shell-encapsulated gas-core spheres. They are considered intravascular agents, i.e., following intravenous injection, they remain within the blood compartment and do not extravasate.…”

A multipixel diffuse correlation spectroscopy system based on a single photon avalanche diode array

“…A measurement series in an Intralipid phantom was done for comparison with literature. Four percent Intralipid (200 mg/mL, Fresenius Kabi, Sweden) was mixed in distilled water for 0.8% lipid in total and = 8 cm −1 , comparable with that used by He et al and Zhou et al . Measurements were made for five source‐detector fiber separations between 6 and 25 mm at 20°C.…”