In vivo quantification of optical contrast agent dynamics in rat tumors by use of diffuse optical spectroscopy with magnetic resonance imaging coregistration

Abstract

We present a study of the dynamics of optical contrast agents indocyanine green ͑ICG͒ and methylene blue ͑MB͒ in an adenocarcinoma rat tumor model. Measurements are conducted with a combined frequency-domain and steady-state optical technique that facilitates rapid measurement of tissue absorption in the 650 -1000-nm spectral region. Tumors were also imaged by use of contrast-enhanced magnetic resonance imaging ͑MRI͒ and coregistered with the location of the optical probe. The absolute concentrations of contrast agent, oxyhemoglobin, deoxyhemoglobin, and water are measured simultaneously each second for approximately 10 min. The differing tissue uptake kinetics of ICG and MB in these late-stage tumors arise from differences in their effective molecular weights. ICG, because of its binding to plasma proteins, behaves as a macromolecular contrast agent with a low vascular permeability. A compartmental model describing ICG dynamics is used to quantify physiologic parameters related to capillary permeability. In contrast, MB behaves as a small-molecular-weight contrast agent that leaks rapidly from the vasculature into the extravascular, extracellular space, and is sensitive to blood flow and the arterial input function.

A simulation study of the variability of indocyanine green kinetics and using structurala prioriinformation in dynamic contrast enhanced diffuse optical tomography (DCE-DOT)

“…Note that υ p was not improved much when the structural priors were used. Therefore it might be useful to calculate this value using the baseline as suggested by Cuccia et al (2003).…”

“…However, they did not detect a difference in the ICG uptake rates between the normal and the neoplastic tissue. Later, Cuccia et al (2003) used a six-parameter pharmokinetic model and presented a study of the dynamics of the ICG in an adenocarcinoma rat tumor model by the use of diffuse optical spectroscopy coregistered with MRI. They found differences in the ICG uptake between necrotic and edematous tumors.…”

Improving signal levels in intravital multiphoton microscopy using an objective correction collar

“…The effects of scattering on light propagation in tissue are typically ten to one hundred times more significant than absorption. [26,27] Calculations indicate that the magnitude of scattering is such that nearly all of the fluorescence arising from a point 100 microns into tissue is scattered prior to exiting the tissue. [4,13] Since deep-tissue microscopy typically involves imaging into a tissue whose average refractive index does not match that of the objective immersion medium, the single point of fluorescence stimulated in a confocal or MPM system will form an image broadened by spherical aberration.…”

How to Improve Quality Assurance in Fluorometry: Fluorescence-Inherent Sources of Error and Suited Fluorescence Standards

“…In vivo fluorescence imaging allows for instance to study the dynamics of contrast agents or specific intrinsic fluorophores, which serve as reporters for diseased tissue [146]. In addition, fluorescence measurements based on specific molecular probes for target detection, i.e.…”