Multispectral optoacoustic localization of ICG-labeled sentinel lymph nodes: phantom study

Sentinel lymph node mapping is clinically important, but optical localization at depth is limited by tissue scattering.This preliminary phantom study evaluates whether multispectral optoacoustic imaging can detect lymph-node-mimicking inclusions embedded in a tissue-like scattering medium.Model nodes containing indocyanine green (ICG) or ICG J-aggregates were used as near-infrared absorbing targets.Compact lymph node models were placed at controlled depths in a Lipofundin-based tissue-mimicking liquid.Two contrast formulations were compared: conventional ICG and self-assembled ICG J-aggregates with a shifted near-infrared absorption band.The measurements were designed to assess detectability, depth dependence and spectral separability under simplified phantom conditions.Optoacoustic measurements were performed with a custom 3D tomographic system based on ultrasound detection of laser-induced acoustic signals [1].Excitation wavelengths covered the main spectral features of ICG and ICG J-aggregates [2].Representative spectra and reconstructed projections of embedded lymph node models are shown in Fig. 1.The same phantom platform is compatible with complementary fluorescence readout.