Investigation of optical coherence micro-elastography as a method to visualize micro-architecture in human axillary lymph nodes

Abstract

BackgroundEvaluation of lymph node involvement is an important factor in detecting metastasis and deciding whether to perform axillary lymph node dissection (ALND) in breast cancer surgery. As ALND is associated with potentially severe long term morbidity, the accuracy of lymph node assessment is imperative in avoiding unnecessary ALND. The mechanical properties of malignant lymph nodes are often distinct from those of normal nodes. A method to image the micro-scale mechanical properties of lymph nodes could, thus, provide diagnostic information to aid in the assessment of lymph node involvement in metastatic cancer. In this study, we scan axillary lymph nodes, freshly excised from breast cancer patients, with optical coherence micro-elastography (OCME), a method of imaging micro-scale mechanical strain, to assess its potential for the intraoperative assessment of lymph node involvement.MethodsTwenty-six fresh, unstained lymph nodes were imaged from 15 patients undergoing mastectomy or breast-conserving surgery with axillary clearance. Lymph node specimens were bisected to allow imaging of the internal face of each node. Co-located OCME and optical coherence tomography (OCT) scans were taken of each sample, and the results compared to standard post-operative hematoxylin-and-eosin-stained histology.ResultsThe optical backscattering signal provided by OCT alone may not provide reliable differentiation by inspection between benign and malignant lymphoid tissue. Alternatively, OCME highlights local changes in tissue strain that correspond to malignancy and are distinct from strain patterns in benign lymphoid tissue. The mechanical contrast provided by OCME complements the optical contrast provided by OCT and aids in the differentiation of malignant tumor from uninvolved lymphoid tissue.ConclusionThe combination of OCME and OCT images represents a promising method for the identification of malignant lymphoid tissue. This method shows potential to provide intraoperative assessment of lymph node involvement, thus, preventing unnecessary removal of uninvolved tissues and improving patient outcomes.

Volumetric quantitative optical coherence elastography with an iterative inversion method

“…Several studies have demonstrated that OCE can visualize tumor in excised human breast tissue [18,[23][24][25][26]. Eventually, OCE may provide intraoperative feedback to surgeons to assist in the detection of tumor, which may reduce the number of re-excision surgeries required to remove residual tumor missed during the initial surgery.…”

Quantification of linear and nonlinear elasticity by compression optical coherence elastography for determining lymph node status in breast cancer

“…However, contrast of such imaging often is insufficient for precise diagnostics of metastases in LNs. Presently, for enhancing the contrast of metastatic LN detection, structural OCT imaging was supplemented with such OCT modalities as attenuation imaging [30] and OCE [31]. Among new OCT modalities, intraoperatively feasible OCE has the high potential to assess LN architecture without physical resection of LNs for analysis, which provides the surgeon with valuable and accurate real-time information on the presence/absence of metastatic disease and potentially enables the preservation of reactive but non-metastatic LNs, thus reducing the risk of lymphedema.…”

Polarization-sensitive optical coherence elastography

“…The microscopic displacement visualizes the mechanical properties of the tissue [35], while more quantitative elastographic information, such as the Young's modulus [31] or shear modulus [36], can be obtained by combining the displacement information with the mechanical stimulation information. OCE has been used to investigate the mechanical properties of cornea [37], breast cancer tissue [38], and several other tissues [39][40][41][42]. The combined use of OCE and PS-OCT has also been demonstrated [43].…”