Intraoperative Assessment of Breast Cancer Tissues after Breast-Conserving Surgery Based on Mapping the Attenuation Coefficients in 3D Cross-Polarization Optical Coherence Tomography

Abstract

Intraoperative differentiation of tumorous from non-tumorous tissue can help in the assessment of resection margins in breast cancer and its response to therapy and, potentially, reduce the incidence of tumor recurrence. In this study, the calculation of the attenuation coefficient and its color-coded 2D distribution was performed for different breast cancer subtypes using spectral-domain CP OCT. A total of 68 freshly excised human breast specimens containing tumorous and surrounding non-tumorous tissues after BCS was studied. Immediately after obtaining structural 3D CP OCT images, en face color-coded attenuation coefficient maps were built in co-(Att(co)) and cross-(Att(cross)) polarization channels using a depth-resolved approach to calculating the values in each A-scan. We determined spatially localized signal attenuation in both channels and reported ranges of attenuation coefficients to five selected breast tissue regions (adipose tissue, non-tumorous fibrous connective tissue, hyalinized tumor stroma, low-density tumor cells in the fibrotic tumor stroma and high-density clusters of tumor cells). The Att(cross) coefficient exhibited a stronger gain contrast of studied tissues compared to the Att(co) coefficient (i.e., conventional attenuation coefficient) and, therefore, allowed improved differentiation of all breast tissue types. It has been shown that color-coded attenuation coefficient maps may be used to detect inter- and intra-tumor heterogeneity of various breast cancer subtypes as well as to assess the effectiveness of therapy. For the first time, the optimal threshold values of the attenuation coefficients to differentiate tumorous from non-tumorous breast tissues were determined. Diagnostic testing values for Att(cross) coefficient were higher for differentiation of tumor cell areas and tumor stroma from non-tumorous fibrous connective tissue: diagnostic accuracy was 91–99%, sensitivity—96–98%, and specificity—87–99%. Att(co) coefficient is more suitable for the differentiation of tumor cell areas from adipose tissue: diagnostic accuracy was 83%, sensitivity—84%, and specificity—84%. Therefore, the present study provides a new diagnostic approach to the differentiation of breast cancer tissue types based on the assessment of the attenuation coefficient from real-time CP OCT data and has the potential to be used for further rapid and accurate intraoperative assessment of the resection margins during BCS.

Depth-Resolved Attenuation Mapping of the Vaginal Wall under Prolapse and after Laser Treatment Using Cross-Polarization Optical Coherence Tomography: A Pilot Study

“…In this paper, for the first time, we calculated the attenuation coefficient from CP OCT images of human vaginal wall tissue in different states: age norm, stage I-II prolapse and stage I-II prolapse after Nd:YAG laser treatment. Attenuation coefficient calculation from OCT data allowed us to achieve improved biological structure visualization and objectively differentiate between tissues of different morphology [41][42][43][44]. In the present study, the depth-resolved method for attenuation coefficient was used for the first time to evaluate connective tissue changes in the vaginal wall.…”

“…In our study, this allowed us to clearly distinguish the epithelium from the underlying lamina propria and assess changes in collagen bundles in the latter layer. Previously, attenuation mapping has predominantly been used in the en face plane, which is preferable for non-layered structures, such as, for example, tumors or inflammations [41,43].…”

“…The attenuation coefficient of the OCT signal is commonly used to quantify the CP OCT data. It helps to improve the assessment of the collagen state, for example, in non-tumorous and tumorous tissues [41], in the identification of an early stage of vulvar lichen sclerosus [42], and in the detection of areas of inflammation vs. norm and necrosis [43]. More recently, it became possible to build depth-resolved attenuation maps in the B-scan projection for the earlier detection of ovarian and fallopian tube malignancy [44].…”

Structured illumination microscopy for cancer identification in diagnostic breast biopsies

“…These microscopy techniques have been demonstrated in the laboratory, but optical clearing steps are lengthy, which present a hinderance to clinical implementation, especially in the context of on-site feedback applications. As such, the most promising approaches for rapid clinical feedback leverage rapid 2D optical sectioning of fresh tissue surfaces, or 3D imaging that does not require optical clearing [ 35 , 36 ]. Research in the field of ex-vivo microscopy continues to address these barriers, including the recent work by Conservano et.…”