Objective and accurate surface measurements of the human breast are important for surgical planning. Traditionally, surgeons plan their procedures using radiographic images, but these images do not illustrate the breast in the surgical position (i.e. supine position). As a result, surgeons need to account for differences in breast size and shape, and surgical outcome is largely dependent on the surgeon’s experience. Previous studies have shown that scanning large-breasted patients in the standing position resulted in breast ptosis and high variability. A system capable of accurately scanning patients in the supine position is therefore desirable. The aim of this work was to develop a non-contact imaging system that can provide 3D information of each breast surface from patients in the supine position. Two structured-light surface scanners were combined using separate colour optical filters to minimize cross-talk between scanners. Test scans were collected from a 3D printed breast phantom in both the supine and standing positions. Scanning with blue and green filters simultaneously at two different angles eliminated shadowing artifacts compared to a single scanner reconstruction. The mean error distance between the phantom CAD model and point cloud measurements was 0.1 ± 0.1 mm for both standing and supine positions. Our system performed better than currently available commercial systems, which have accuracy of 0.5 - 1 mm.
Photoacoustic tomography (PAT) has excellent sensitivity for hemoglobin and lipids, which make up much of human breast tissue. Our group has focused on intraoperative PAT applied to tissues obtained during breast-conserving surgery (BCS). In BCS, the tumor is excised with a margin of healthy tissue to ensure tumor removal. Margin detection can be difficult and re-excision surgeries are required in 10 to 25% of cases. Our first-generation intraoperative PAT system was capable of 3D imaging specimens up to 11 cm in diameter and several centimeters thick. The system used a semi-circular ring of low frequency transducers, resulting in a 2.5 mm spatial resolution. The current objective is to improve spatial resolution using higher frequency transducers. An array was constructed with 41 circular transducers positioned on two concentric circular rungs with a single point of focus. An optical window at the center allowed illumination. The array was tested with imaging phantoms consisting of written words on a clear plastic bag, 108 µm polyester monofilament arranged as parallel lines with spacing varying from 1 mm to 8 mm, and finally with porcine tissues. The array was positioned above and perpendicular to the imaging area and raster scanned. Signal averaging was implemented, and images were reconstructed with universal back projection. Image analysis demonstrated a 400 μm spatial resolution, but with low penetration depth and low sensitivity. Results suggest the transducers could improve spatial resolution of the first-generation intraoperative PAT system by 6-fold.