Purpose: To develop a system to detect positive margins during the time of breast conserving surgery. The instrumentation is a combined x-ray micro computed tomography (uCT) and optical structured light imaging (SLI), which is tested in a clinical study imaging whole lumpectomy specimens within the surgery suite.
Methods: A system was developed that performed a 50 kVp, 1 mAs uCT scan and SLI at five optical wavelengths ranging from 490 nm to 700 nm at high spatial frequency, requiring eight minutes per scan. SLI involves illuminating a sample with sinusoid patterns and imaging the reflectance. As the spatial frequency of the pattern increases, the depth penetration of the light is decreased. This makes high frequency SLI sensitive to superficial structures which are relevant to BCS as positive margins are malignant cells at the surface for invasive carcinomas and for DCIS within 2 mm of the surface. Custom optically clear acrylic plates with 3D printed spacers to create optimal surfaces for SLI were made to optimize workflow.
Results: Results from previous studies on breadloafed specimens have shown statistically significant differences between the signals from many subtypes of malignancy and surrounding benign tissue with SLI on tissue slices post-surgery. Other studies have also shown an increase in sensitivity with uCT over specimen x-ray. The current study on whole lump scanning represents the next major step towards clinical use with optimization to clinically applicable time-frames without loss of sensitivity.
Conclusion: This study represents the first major cohort of whole lumpectomies imaged using uCT and SLI. Tumor confirmation, clip localization, and volumetric information is obtained through uCT while surface information that is highly sensitive to malignancy is gained through SLI. The high speed, large field of view, and sensitivity to morphology changes associated with malignancy make it an attractive modality to match with uCT.