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

Abstract

Dynamic contrast-enhanced diffuse optical tomography (DCE-DOT) can provide spatially resolved enhancement kinetics of an optical contrast agent. We undertook a systematic phantom study to evaluate the effects of the geometrical parameters such as the depth and size of the inclusion as well as the optical parameters of the background on the recovered enhancement kinetics of the most commonly used optical contrast agent, indocyanine green (ICG). For this purpose a computer-controlled dynamic phantom was constructed. An ICG–intralipid–water mixture was circulated through the inclusions while the DCE-DOT measurements were acquired with a temporal resolution of 16 s. The same dynamic study was repeated using inclusions of different sizes located at different depths. In addition to this, the effect of non-scattering regions was investigated by placing a second inclusion filled with water in the background. The phantom studies confirmed that although the peak enhancement varied substantially for each case, the recovered injection and dilution rates obtained from the percentage enhancement maps agreed within 15% independent of not only the depth and the size of the inclusion but also the presence of a non-scattering region in the background. Although no internal structural information was used in these phantom studies, it may be necessary to use it for small objects buried deep in tissue. However, the different contrast mechanisms of optical and other imaging modalities as well as imperfect co-registration between both modalities may lead to potential errors in the structural a priori. Therefore, the effect of erroneous selection of structural priors was investigated as the final step. Again, the injection and dilution rates obtained from the percentage enhancement maps were also immune to the systematic errors introduced by erroneous selection of the structural priors, e.g. choosing the diameter of the inclusion 20% smaller increased the peak enhancement 60% but changed the injection and dilution rates only less than 10%.

Dual-Contrast Dynamic MRI-DOT for Small Animal Imaging

“…We used a combined MR-DOT system that has previously been described in detail (21–23). This system used a series of eight source fibers to deliver light from laser diodes modulated at 100MHz to the animal being imaged.…”

“…However, in vivo studies in the literature showed that following the administration, the ICG concentration reached to its peak in nearly one minute (10, 17). To be able to monitor the enhancement kinetics of ICG, we recently increased the time resolution of our DOT system to 16 seconds using a heterodyne detection technique (23). The new version of the system recorded the output signals of the PMTs simultaneously using NI 4472 8-channel DAQ system after the down conversion of the signal frequency to 1 kHz.…”

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

“…14,15 The system operates at 100 MHz and 8 sources and 8 detectors are used, which yield 64 amplitude and 64 phase measurements. The temporal resolution of the system is 16 s, which is a pivotal feature for measuring ICG kinetics due to the fact that ICG reaches its peak concentration in about 1 min.…”

Advances in fluorescence diagnosis to track footprints of cancer progression in vivo

“…MRI anatomical prior information was incorporated into the FT reconstruction algorithms, in order to improve in vivo tumor localization. This method was also exploited by Gulsen and coworkers when they built a MRI‐guided dynamic contrast‐enhanced diffuse optical tomography (DCE‐DOT) system and used it together with ICG and a MR contrast agent [Gd‐diethylenetriaminepentaacetic acid (DTPA)] for tumor characterization in a rat model. As tumors grow, they undergo necrosis and the tissue transforms from viable to necrotic.…”