Optical coherence elastography (OCE) is an imaging technique capable of mapping mechanical properties (such as elasticity) in 3-D and is emerging as a valuable tool in the study and potential intraoperative diagnosis of breast cancer due to mechanical contrast between healthy and malignant tissue. While the correlation between elevated elasticity in OCE and breast cancers has been well established, these studies have primarily focused on binary classifications of tissue as either malignant or benign, ignoring much of the heterogeneity present in breast tissue. In this work, we present a detailed assessment of the microstructures present in human breast tissue images acquired with OCE, identifying regions of interest that corresponded to invasive carcinomas, in situ carcinomas and benign tissue types. We also describe the unique morphological patterns present in each tissue type and provide a framework for the interpretation of breast cancer images acquired with OCE.
Optical coherence elastography (OCE) provides mechanical contrast on the micro-scale and has shown promise in a number of clinical applications. In the majority of OCE methods, local homogeneity is inherently assumed in the mechanical models, which results in low accuracy in complex tissues. Here, we present a novel compression OCE method that exploits tissue heterogeneity to generate mechanical contrast in human breast tissue by mapping the full strain tensor. We used the strain tensor to map mechanical parameters such as Euler angle of principal compression. We also demonstrate a new form of quantitative OCE by mapping local Poisson’s ratio.
In this work, we present the development of a compact, wireless imaging probe using a cost effective camera based optical elastography technique, stereoscopic optical palpation, towards intraoperative tumour assessment for breast cancer surgery. We demonstrate the working principle of this probe and test its capability of tumour margin assessment on freshly excised tissues. With further development, this probe holds the potential to be used as a real time cancer imaging tool that can help surgeons more effectively remove cancer during the operation, reducing the need for follow-up surgery. The probe has the potential to be used in rural and remote areas.
Quantitative micro-elastography (QME) is a compression-based optical coherence elastography technique that visualizes micro-scale tissue stiffness. Current benchtop QME shows great potential for identifying cancer in excised breast tissue (96% diagnostic accuracy), but cannot image cancer directly in the patients. We present the development of a handheld QME probe to directly image the surgical cavity in vivo during breast-conserving surgery (BCS) and a preliminary clinical demonstration. The results from 21 patients indicate that in vivo QME can identify residual cancer based on the elevated stiffness by directly imaging the surgical cavity, potentially contributing to a more complete cancer excision during BCS.
Assessing mechanical properties of tissue plays an important role in disease diagnosis and clinical examination. Here, we present a low resource and cost-effective method of using digital camera technologies to map mechanical properties of tissue, termed camera-based optical palpation. We applied this technique to breast cancer detection and burn scar assessment, validating its capability of generating high mechanical contrast between various tissue regions for clinical applications. We also implemented camera-based optical palpation in a smartphone, demonstrating its potential for telehealth applications in rural and remote areas, improving equity of access to optimal treatment for people all around the world.
Re-excision following breast-conserving surgery (BCS) due to suspected residual cancer left from the primary surgery causes substantial physical, psychological, and financial burdens for patients. This study provides a first-in-human clinical study of in vivo quantitative micro-elastography (QME) for in-cavity identification of residual cancer. A custom-built handheld QME probe is used to directly scan the surgical cavity for imaging the micro-scale tissue stiffness during BCS. In vivo QME of 21 patients, validated by co-registered histopathology of the excised specimens, demonstrates the capability to detect residual cancer based on its elevated micro-scale stiffness, potentially contributing to a more complete cancer removal.
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.
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