Abstract
Diffuse reflectance spectroscopy (DRS) is being used in exploratory clinical applications such as cancer margin assessment on excised tissue. However, when interrogating nonplanar tissue anomalies can arise from non-uniform pressure. Herein is reported the design, fabrication, and test of flexible, thin film silicon photodetectors (PDs) bonded to a flexible substrate designed for use in conformal DRS. The PDs have dark currents and responsivities comparable to conventional Si PDs, and were characterized while flat and while flexed at multiple radii of curvature using liquid phantoms mimicking adipose and malignant breast tissue. The DRS and nearest neighbor crosstalk results were compared with Monte Carlo simulations, showing good agreement between simulation and experiment.
Highlights
Cancer margin assessment performed in the surgical suite on excised breast tissue has the potential to significantly reduce costly, emotionally challenging re-excision surgery [1]
The process of extracting the optical properties can be performed by comparing the reflectance data to a previously calculated table [2,3,4], to a model based on the diffusion approximation [5, 6], or to Monte-Carlo simulations [7,8,9,10], yielding quantitative information that can determine chromophore concentrations in skin [11], diagnosis of skin cancers [12], detect oral [13, 14], colon [15, 16], and breast cancer [8, 17], and perform intra-operative breast cancer margin assessment [18, 19]
The PD Diffuse Reflectance Spectroscopy (DRS) performance was measured on two liquid phantoms, representing benign and malignant breast tissue
Summary
Cancer margin assessment performed in the surgical suite on excised breast tissue has the potential to significantly reduce costly, emotionally challenging re-excision surgery [1]. The NA and packing density of photodetectors (PDs) can be significantly larger than optical fibers, if the PDs are placed directly on or close to the tissue sample One example of this is a custom 4 x 4 array of annular Si PDs implemented in a DRS probe for breast cancer margin assessment [20]. The design, fabrication, and test of a probe comprised of flexible, thin film Si custom annular PDs bonded to a flexible substrate optimized for DRS imaging is reported. The flexibility of these 10 μm thick PDs enables conformal tissue sensing. The DRS photodetector design was optimized for high optical throughput and high signal to noise ratio [20] by varying the PD shape, size, and spacing to maximize the collected DRS signal while minimizing the back illumination and crosstalk signals
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