A low-cost, portable, and quantitative spectral imaging system for application to biological tissues

Abstract

Abstract:The ability of diffuse reflectance spectroscopy to extract quantitative biological composition of tissues has been used to discern tissue types in both pre-clinical and clinical cancer studies. Typically, diffuse reflectance spectroscopy systems are designed for single-point measurements. Clinically, an imaging system would provide valuable spatial information on tissue composition. While it is feasible to build a multiplexed fiber-optic probe based spectral imaging system, these systems suffer from drawbacks with respect to cost and size. To address these we developed a compact and low cost system using a broadband light source with an 8-slot filter wheel for illumination and silicon photodiodes for detection. The spectral imaging system was tested on a set of tissue mimicking liquid phantoms which yielded an optical property extraction accuracy of 6.40 ± 7.78% for the absorption coefficient (µ a ) and 11.37 ± 19.62% for the wavelength-averaged reduced scattering coefficient (µ s '). ©2010 Optical Society of America

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

“…10 Using tissuesimulating liquid phantoms, we demonstrated equivalent optical quantitation accuracy to the fiber-based systems. The primary limitation of this initial prototype stemmed from repurposing the commercial photodiodes; producing the illumination apertures involved a drilling process that proved to be unreliable from a manufacturing standpoint due to the brittleness of the encapsulated Si-based photodiodes.…”

Instrumentation in Diffuse Optical Imaging

“…The advantages of fiber-coupling include high flexibility in hardware configuration and improved instrument ruggedness. Optical fibers are also often used in small animal imaging, human neuroimaging, and multimodality imaging, because they provide reliable optical contact, reduce the interference from hair, and allow flexibility in system configuration and experimental setup, e.g., [14, 25, 26, 27, 28, 29]. Disadvantages of fiber-coupling include limited mobility of the imaging subject, reduced usable experiment duration due to discomfort, and inconsistent skin-fiber coupling efficiency as a result of variations in fiber contact and subject motion.…”

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

“…While our previously reported diffuse reflectance imaging systems have utilized individual fibers or fiber bundles to illuminate each tissue site, these systems have been limited to less than 10 illumination sites per image, and pixel spacings greater than 7 mm [12,13]. As pixel to pixel spacing decreases, and in addition, imaging area increases, illuminating each tissue site with a fiber becomes increasingly unwieldy.…”

“…A classification model was developed using a combination of these endpoints to detect positive tumor margins with a sensitivity of 79.4% (i.e., percentage of correctly detected positive margins), and specificity of 66.7% (i.e., percentage of correctly detected negative margins) from a 48 patient cohort, demonstrating its potential to significantly reduce re-excision surgeries [2]. However, this system costs $50,000, has a footprint of 2 m × 1 m, and is only capable of coarse 8-pixel imaging [12,13]. In addition, the ability to rapidly assess large margin areas is key in the context of breast cancer imaging, since excised breast tissue areas can be as large as 20 cm 2 .…”

“…It was demonstrated that optical properties could be extracted with low errors using the inverse Monte Carlo model, with eight wavelengths of light as opposed to 81 wavelengths used in the bench-top system [14]. In addition, an array of mechanically drilled commercial silicon photodiodes was developed to achieve Si photodiode-based collection, and fibers were epoxied to the drilled photodiode apertures to achieve fiber-based illumination in the DRS probe [13]. This system obviated the need to use an imaging spectrograph and a 2D CCD for obtaining spectral information; components that significantly added to the complexity and foot-print of the bench-top system.…”