High spatial frequency structured light imaging for intraoperative breast tumor margin assessment

Abstract

A new superficial wide-field imaging technique is presented, which utilizes high spatial frequency structured illumination to constrain the light sampling volume to a sub-diffuse regime. In this transport regime, the effects of absorption are drastically reduced and the sensitivity to local scattering from ultrastructrual alterations is increased. Absorption independence is validated with multiple experiments including a bovine blood-Intralipid solution matrix and avian tissue with superficial bovine blood. The resulting structured light demodulated images show a complete insensitivity to the blood over Hb concentrations of 0 – 240 μM. Increased sensitivity to ultrastructual changes is demonstrated by imaging avian tissue with controlled morphological alterations including formalin-induced crosslinking. This imaging technique is currently being translated towards intraoperative assessment of breast tumor margins because of its ability to capture an entire lumpectomy margin in a single field of view, insensitivity to confounding surface blood present on lumpectomies, and its inherent scatter signal without the need of any model inversion. Further, a new lumpectomy marking system is introduced that allows for both the surgeon to mark the lumpectomy during excision and optical assessment of the specimen after the margins have been marked. Structured light images acquired intraoperatively of all margins of lumpectomy specimens are presented to show feasibility of clinical translation. Immediate future work will focus on developing a multi-spectral system.