This presentation reports a comparison between two handheld quantitative micro elastography (QME) methods: PZT actuated compression QME and manual compression QME. PZT actuated compression QME utilizes a PZT actuator to provide a periodic compression against the scanned sample, whilst manual compression QME utilizes the continuous motion of the user’s hand holding the probe to create compression against the sample. From our results, each method has its own advantages, and both methods are capable of measuring elasticity of the sample and distinguishing stiff tumor from regions of soft benign tissue on excised human breast specimens.
Breast-conserving surgery (BCS) for treatment of breast cancer requires complete removal of the tumor. 20-30% of patients undergoing BCS require multiple surgeries due to cancer at or near the boundary (margin) of the excised tissue as assessed by postoperative histopathology. Intraoperative detection of involved margins could significantly reduce the number of patients requiring repeat surgeries. We built and deployed a portable optical coherence elastography system capable of rapid, 3D imaging of whole margins (46x46 mm) of excised breast specimens (wide local excisions, WLEs) removed during BCS. The system produces images of the microstructure and stiffness of the tissue using a phase-sensitive, compression-based elastography approach. The goal of this study was to determine the diagnostic accuracy (sensitivity and specificity), using this system, of OCT versus OCT plus micro-elastography for detecting cancer within 0.75 mm of the margin of the excised tissue. >70 women undergoing BCS were enrolled in the study. We scanned two margins from each fresh, intact surgical specimen within 2 hours of excision. We selected 10x10x0.75mm regions of interest (ROIs) from each margin scanned that are representative of the makeup of breast tissue. Post-operative histology, co-registered with the scans, was used as a gold standard, and a pathologist determined the tissue types present within each ROI based on corresponding histology. Recruitment for the study is complete, and a blinded reader analysis of one ROI from each margin is being performed by two surgeons, a pathologist, a radiologist, and an engineer. Results for sensitivity and specificity will be presented.
Approximately a quarter of patients undergoing breast conserving surgery will need further surgery as close or involved surgical margins suggest they may have residual tumour in the breast. Handheld imaging probes capable of scanning the surgical cavity during the surgery have the potential to improve intraoperative assessment of surgical margins in breast conserving surgery thus allow real time assessment of completeness of tumour excision. In this paper, we present a handheld optical coherence elastography (OCE) probe, allowing us to acquire a 3D quantitative elastogram of a 6×6×1.5 mm volume in 3.4 seconds. Our technique is based on a compression OCE technique, referred to as quantitative micro-elastography (QME), where a compliant silicone layer is incorporated to measure stress at the tissue surface. To perform handheld scanning, we implemented a rapid scan pattern to enable B-scan rates of 215 Hz using a microelectromechanical system (MEMS) scanner: minimizing the time difference between B-scan pairs used to generate displacement maps thus minimizing the motion artefact caused by hand motion. We present handheld scans acquired from silicone phantoms where the motion artefact is barely noticeable. In addition, freshly dissected human breast tissue from a mastectomy was scanned with the handheld probe. The breast tissue elastograms are validated using standard histology and demonstrate our ability to distinguish stiff regions of tumour from benign tissue using this probe.