Tissue Phantom for Optical Imaging

The tissue phantom was made from gelatin gel containing 2% of Intralipid (20%, emulsion, Sigma) mimicking the scattering from the tissue and 100 µM of hemoglobin (porcelain, Sigma) mimicking tissue absorption.^{37 (link)–38 (link)} Briefly, 5 g of gelatin, 1 ml of Intralipid (20% emulsion), 320 mg of hemoglobin and 0.5 g glutaraldehyde were dissolved in 50ml Tris buffer (pH=7.4, 50 mM Tris, 150 mM NaCl and 0.1% w/v sodium azide) at about 50 °C. The homogenous solution was then poured to a model with the thickness of 1, 2, 3, and 4 mm. The gel was formed after refrigeration overnight. For the tissue penetration experiment, 80 µCi (2.96 MBq) of ⁸⁹Zr and an increasing concentration of QDs were added to wells in a 96-well plate, reaching a total volume of 250 µl. The tissue phantoms with different thickness were placed on top of the well plate and imaged in a PerkinElmer IVIS Spectrum optical imaging system. QD fluorescence was imaged with excitation at 605 nm, emission at 720 nm, and 2 s exposure time. CL was imaged without blocked excitation, either open emission filter or 720 nm filter, and 2 min exposure time.