A diffuse reflectance spectral imaging system for tumor margin assessment using custom annular photodiode arrays

Abstract

Diffuse reflectance spectroscopy (DRS) is a well-established method to quantitatively distinguish between benign and cancerous tissue for tumor margin assessment. Current multipixel DRS margin assessment tools are bulky fiber-based probes that have limited scalability. Reported herein is a new approach to multipixel DRS probe design, which utilizes direct detection of the DRS signal by using optimized custom photodetectors in direct contact with the tissue. This first fiberless DRS imaging system for tumor margin assessment consists of a 4 × 4 array of annular silicon photodetectors and a constrained free-space light delivery tube optimized to deliver light across a 256 mm2 imaging area. This system has 4.5 mm spatial resolution. The signal-to-noise ratio measured for normal and malignant breast tissue-mimicking phantoms was 35 dB to 45 dB for λ = 470 nm to 600 nm.

Wavelength Optimization for Quantitative Spectral Imaging of Breast Tumor Margins

“…The phantom optical measurements were obtained with a previously reported system with slight modifications [1], [9] The system consists of a 450W Xenon Arc lamp and a scanning monochromator (Gemini 180, JY Horiba) coupled to a 600 µm optical fiber as the source. The spectral bandpass of the illumination was fixed at 7 nm.…”

“…A wavelength optimization strategy is developed to improve the design of a novel spectral imaging probe array [1] for quantitative assessment of breast tissue margins during partial mastectomy surgery, a common treatment for early stage breast cancer [2], [3]. This generalized method is based on a search heuristic known as a genetic algorithm that mimics the process of natural evolution and identifies reduced wavelength sets that maintain tissue optical contrast when compared to the broadband data.…”

Rapid Determination of Oxygen Saturation and Vascularity for Cancer Detection

“…With appropriate optimization for wavelength and illumination and collection geometries, the ratiometric analysis might be applied to a variety of spectral imaging systems [56] [57] [58] [59]. For example, this analysis can be incorporated into previously developed fiber-less technology [59], where a Xenon lamp and light filters are used to illuminate the tissue at different wavelengths of light. The illumination light was delivered through free space with a quartz light delivery tube.…”

Miniature spectral imaging device for wide-field quantitative functional imaging of the morphological landscape of breast tumor margins

“…The specific details of the PDA fabrication process flow, photodiode responsivity, SNR, and cross talk considerations are detailed in Ref. 12. Briefly, the imaging array consists of 16 annular photodiodes formed on an n-type silicon epitaxial substrate and is arranged in a 4 × 4 array with a 4.5 mm center-to-center pixel pitch, resulting in a 256 cm 2 The patterned silicon wafer is diced into a rectangle and is epoxied and wire-bonded to a gold plated printed circuit board for structural support and traces for photocurrent readout.…”

“…The optimal length of the absorbing tube was determined to be 70 mm as this provided low cross talk (4%) and nearly uniform illumination (center-pixel throughput ratio: 0.74). 12 Aperture throughput ranged from 17 to 22 μW per aperture while the total output from the hybrid LG ranged from 45 to 55 mW. An 8-slot filter wheel within the Asahi lamp houses eight thin-film bandpass filters (BP ¼ 10 nm) across the visible spectrum (λ ¼ ½470 480 490 500 510 560 580 600 nm).…”