Program Information
High-Resolution Optical-CT/ECT Imaging of Unstained Mice Femur, Brain, Spleen, and Tumor
S Yoon1*, M Boss2 , S Birer3 , M Dewhirst1 , M Oldham1 , (1) Duke University Medical Center, Durham, NC, (2) North Carolina State University, Durham, North Carolina, (3) Duke University School of Medicine, Durham, North Carolina
Presentations
TH-EF-207A-6 (Thursday, August 4, 2016) 1:00 PM - 2:50 PM Room: 207A
Purpose: Optical transmission and emission computed tomography (optical-CT/ECT) provides high-resolution 3D attenuation and emission maps in unsectioned large (~1cm³) ex vivo tissue samples at a resolution of 12.9μm³ per voxel. Here we apply optical-CT/ECT to investigate high-resolution structure and auto-fluorescence in a range of optically cleared mice organs, including, for the first time, mouse bone (femur), opening the potential for study of bone metastasis and bone-mediated immune response.
Methods: Three BALBc mice containing 4T1 flank tumors were sacrificed to obtain spleen, brain, tumor, and femur. Tissues were washed in 4% PFA, fixed in EtOH solution (for 5, 10, 10, and 2 days respectively), and then optically cleared for 3 days in BABBs. The femur was also placed in 0.25M aqueous EDTA for 15-30 days to remove calcium. Optical-CT/ECT attenuation and emission maps at 633nm (the latter using 530nm excitation light) were obtained for all samples. Bi-telecentric optical-CT was compared side-by-side with conventional optical projection tomography (OPT) imaging to evaluate imaging capability of these two rival techniques.
Results: Auto-fluorescence mapping of femurs reveals vasculatures and fluorescence heterogeneity. High signals (A.U.=10) are reported in the medullary cavity but not in the cortical bone (A.U.=1). The brain strongly and uniform auto-fluoresces (A.U.=5). Thick, optically dense organs such as the spleen and the tumor (0.12, 0.46OD/mm) are reconstructed at depth without significant loss of resolution, which we attribute to the bi-telecentric optics of optical-CT. The attenuation map of tumor reveals vasculature, attenuation heterogeneity, and possibly necrotic tissue.
Conclusion: We demonstrate the feasibility of optical-CT/ECT imaging of un-sectioned mice bones (femurs) and spleen with high resolution. This result, and the characterization of unstained organs, are important steps enabling future studies involving optical-CT/ECT applied to study metastasis and immunologic responses via fluorescence staining.
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