Dynamic contrast-enhanced diffuse optical tomography (DCE-DOT): experimental validation with a dynamic phantom

Temporal Unmixing of Dynamic Fluorescent Images by Blind Source Separation Method with a Convex Framework

By recording a time series of tomographic images, dynamic fluorescence molecular tomography (FMT) allows exploring perfusion, biodistribution, and pharmacokinetics of labeled substances in vivo. Usually, dynamic tomographic images are first reconstructed frame by frame, and then unmixing based on principle component analysis (PCA) or independent component analysis (ICA) is performed to detect and visualize functional structures with different kinetic patterns. PCA and ICA assume sources are statistically uncorrelated or independent and don't perform well when correlated sources are present. In this paper, we deduce the relationship between the measured imaging data and the kinetic patterns and present a temporal unmixing approach, which is based on nonnegative blind source separation (BSS) method with a convex analysis framework to separate the measured data. The presented method requires no assumption on source independence or zero correlations. Several numerical simulations and phantom experiments are conducted to investigate the performance of the proposed temporal unmixing method. The results indicate that it is feasible to unmix the measured data before the tomographic reconstruction and the BSS based method provides better unmixing quality compared with PCA and ICA.

Tumor characterization in small animals using magnetic resonance-guided dynamic contrast enhanced diffuse optical tomography

We present a magnetic resonance (MR)-guided near-infrared dynamic contrast enhanced diffuse optical tomography (DCE-DOT) system for characterization of tumors using an optical contrast agent (ICG) and a MR contrast agent [Gd-diethylenetriaminepentaacetic acid (DTPA)] in a rat model. Both ICG and Gd-DTPA are injected and monitored simultaneously using a combined MRI-DOT system, resulting in accurate co-registration between two imaging modalities. Fisher rats bearing R3230 breast tumor are imaged using this hybrid system. For the first time, enhancement kinetics of the exogenous contrast ICG is recovered from the DCE-DOT data using MR anatomical a priori information. As tumors grow, they undergo necrosis and the tissue transforms from viable to necrotic. The results show that the physiological changes between viable and necrotic tissue can be differentiated more accurately based on the ICG enhancement kinetics when MR anatomical information is utilized.

Dual-contrast dynamic MRI-DOT for small animal imaging

In this paper we present first-of-its-kind spatially resolved enhancement kinetics of optical and magnetic resonance (MR) agents obtained by a combined MR and Diffuse Optical Tomography (MR-DOT) animal imaging system. A unique MR compatible fiber optic interface allows co-registration of MR and DOT data in space and time. High temporal resolution of the hybrid system permits acquisition of data in dynamic mode. Rats bearing a R3230 AC breast cancer tumor model are used for in vivo studies. Thirty-two optical and thirty MR images are acquired during a single imaging session that lasts nearly ten minutes. Both optical, indocyanine green (ICG), and MR contrast agents, gadolinium-DTPA (Gd-DTPA), are injected simultaneously after the acquisition of several baseline frames. Contrast enhancement time curves obtained by MR and DOT systems both indicate higher average enhancement in tumor regions, up to ten-fold for MRI and 3-fold for DOT, compared to close by non-tumor regions. This feasibility study is the first step towards clinical translation of this hybrid imaging platform. The ultimate aim is to use the enhancement kinetics of the optical agent ICG, which binds to plasma proteins, as complementary information to the kinetics of the MR agent Gd-DTPA, a small molecular agent that does not bind to plasma proteins, to better differentiate benign and malignant lesions.