Abstract
AbstractIntraoperative assessment of surgical margins remains one of the main challenges in cancer surgery. Raman spectroscopy can detect cancer cells with high accuracy, but it is time‐consuming. In this paper, we investigated a selective‐sampling Raman spectroscopy approach, based on high wavenumber (HW) Raman imaging (spectral range 2,500–3,500 cm−1) and fingerprint Raman spectroscopy (spectral range 600–1,800 cm−1), to reduce the overall tissue analysis time while maintaining high diagnostic accuracy. HW Raman mapping was used as a first step to identify the adipose tissue regions based on the C–H stretching bands at 2,700–2,950 cm−1. As residual tumors are typically found in nonadipose tissue, an algorithm was developed to allocate sampling points for fingerprint Raman spectroscopy at locations corresponding to low intensity in the HW‐Raman maps. Preliminary results show that HW‐Raman imaging based on a 671 nm laser is effective and fast for mapping of adipose tissue in breast resections, with typical imaging times of 2 min for tissue areas as large as 2 × 2 cm2 areas. Albeit the remaining high fluorescence background in the fingerprint region prevents the use of single 671‐nm laser, the HW Raman imaging can be still exploited in combination with 785‐nm excitation Raman spectroscopy for identifying residual tumor. Although this study demonstrates the feasibility of this approach, further improvements, such as using single element detectors for HW Raman imaging, are required to increase the analysis speed further towards intraoperative use in the routine clinical setting.
Highlights
Breast conserving surgery (BCS) is widely used for treating patients with breast cancers.[1]
The fluorescence background is even stronger for nonadipose tissue, and only the broad water band is detectable at 3,400 cm−1.19 In the fingerprint region, only the bands at 1,157 and 1,525 cm−1 can be detected for the adipose tissue, which can be assigned to carotenoids.[21]
These results indicate that the selection of laser excitation around 660 nm is a good trade-off between maximizing the efficiency for detecting the Raman bands in both fingerprint and the high wavenumber regions and enables discrimination between the adipose and nonadipose tissue
Summary
Breast conserving surgery (BCS) is widely used for treating patients with breast cancers.[1]. We developed a selective-sampling technique that combined high-resolution wide-field auto-fluorescence (AF) microscopy and fingerprint Raman spectroscopy (700–1,800 cm−1 Raman shift region) to detect ductal carcinomas in frozen breast microsections (5 × 5 mm2).[14] More recently, confocal AFRaman spectroscopy combined with more efficient data processing algorithms enabled the analysis of larger tissues areas (4 × 6.5 cm area) with acquisition times of 12–24 min, achieving 95% sensitivity and 82% specificity in an independent test on 121 samples from 107 patients (including 51 fresh, whole excision specimens).[17] the confocal AF was effective in segmenting the tissue images based on AF intensity, it was not able to reliably identify the regions of adipose tissue. This approach has the advantage of targeting the fingerprint Raman measurements more effectively to the nonadipose tissue areas, which are associated with stroma, benign, or malignant tumor
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