PHILADELPHIA – Intraoperative optical coherence tomography (OCT) rapidly images larger breast tumor margin areas, dramatically improving the microscopic sampling rate or analysis of the margin.
“Intraoperative OCT has the potential to provide diagnostically useful information about margin status in real time, at the point of care, rather than relying on postoperative histopathology,” said Stephen Boppart, M.D., Ph.D., professor of electrical and computer engineering, bioengineering and medicine, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign.
Results of this study will appear in an article and on the cover of the Nov. 15 issue of Cancer Research, a journal of the American Association for Cancer Research.
OCT is a high-resolution imaging technique that offers optical biopsies of tissue, therefore yielding images that approach the resolution of histopathology.
Boppart and colleagues demonstrated the feasibility of using this technology for evaluating surgical margins during breast-conserving lumpectomy procedures. The aim was to first establish image-based features that could be used to determine negative or positive margins, and then demonstrate how well intraoperative OCT compares to histopathological findings of the tissue.
Thirty-seven patients were divided into two groups – 17 in a training set and 20 in a study set. Of the lumpectomy specimens in the study set, 11 had a positive or close surgical margin; nine had a negative margin under OCT.
In the study set, intraoperative OCT had 100 percent sensitivity and 82 percent specificity for determining margin status using postoperative histopathology as the gold standard, according to Boppart. OCT, with imaging resolution around 10 microns and depth-of-imaging up to 2 mm into the tissue, identified cell and tissue features to differentiate negative margins from positive margins.
“The imaging depth was equivalent to the tissue depth that pathologists typically examine postoperatively to determine if the margin is negative, close or positive,” he said. “Image features could also be used to identify structures such as surface blood or cauterized tissue and distinguish these image artifacts from normal and tumor tissue.”
Follow-up studies are ongoing in an effort to develop computer-aided detection algorithms that would automatically identify suspicious areas within images, according to Boppart. New computed imaging techniques are also being developed to improve the imaging resolution over larger volumes of tissue, which should further improve the ability to distinguish tumor cells.
“OCT is a very promising technology with many advantages for real-time optical biopsies of tissue. We hope that this technology and methodology will shift the microscopic assessment of tissue from postoperative assessment in the pathology lab, which offers limited sampling of the margin, to real-time, point-of-care assessment in the operating room, with improved comprehensive sampling of the surgical margin,” Boppart said.
He believes this will ultimately result in fewer repeat surgeries and long-term, potentially lower local recurrence rates.
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