Abstract 4054: Assessment of the progression of lymph node metastases using three-dimensional optical coherence tomography (OCT)
Authors: South Fredrick , Marjanovic Marina , John Renu , Adie Steven G. , Chaney Eric J. , Tangella Krishnarao V. , Ray Partha , Brockenbrough John , Monroy Guillermo L. , Hsu Jessica , Boppart Stephen A. 
Published: August 2012

Abstract
Several techniques have been developed to localize lymph nodes, primarily sentinel lymph nodes, prior to resection during cancer surgery, and for post-operative histological assessment. However, none of these existing methods offer the potential for in situ assessment of lymph nodes and their metastatic involvement, potentially during surgical procedures, and for intraoperatively staging cancer. In this study, three-dimensional optical coherence tomography (3-D OCT) was used for imaging and assessing resected popliteal lymph nodes from a pre-clinical rat metastatic tumor model over a 9-day time-course study after the injection of tumor cells into the lymphatic system via the hindlimb footpad. The spectral-domain OCT system utilized a center wavelength of 800 nm, provided axial and transverse resolutions of 3 µm and 12 µm, respectively, and performed imaging at 10,000 axial scans per second. OCT is capable of providing high-resolution label-free images of intact lymph node microstructure based on intrinsic optical scattering properties with penetration depths of ∼ 1-2 mm. To verify OCT findings, the lymph nodes were sectioned at the OCT imaging sites. Direct comparison of the 3-D OCT data and histology revealed that microstructural changes in the lymph node were detectable by the changes in optical scattering and the features visualized in the OCT images. The results demonstrate that OCT is capable of differentiating normal, reactive and metastatic lymph nodes based on these microstructural changes. The optical scattering and structural changes revealed by OCT from Day 3 to Day 9 correlate with inflammatory and immunological changes observed in the capsule, precortical regions, follicles, and germination centers found in the histopathology. We report for the first time a longitudinal study of 3-D trans-capsule OCT imaging of intact lymph nodes during metastatic infiltration. In a related intraoperative clinical study, resected lymph nodes from the cancer patients were imaged during the surgical procedure and the data was correlated with histological findings. The imaged sites were marked with surgical ink, and histology sections were taken for correlation with the 3-D OCT data. Clinical pathology reports were compared with OCT findings to determine the accuracy of our results. These preliminary clinical studies have identified scattering changes in the cortex, relative to the capsule, which can be used to differentiate normal from metastatic nodes. Our imaging studies of resected lymph nodes in both animal cancer models and human cancer patients demonstrate the potential of OCT as a technique for real time, in situ 3-D optical biopsy of lymph nodes for the intraoperative staging of cancer.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4054. doi:1538-7445.AM2012-4054