Effect of curvature correction on parameters extracted from hyperspectral images

Abstract

. Significance: Hyperspectral imaging (HSI) has emerged as a promising optical technique. Besides optical properties of a sample, other sample physical properties also affect the recorded images. They are significantly affected by the sample curvature and sample surface to camera distance. A correction method to reduce the artifacts is necessary to reliably extract sample properties. Aim: Our aim is to correct hyperspectral images using the three-dimensional (3D) surface data and assess how the correction affects the extracted sample properties. Approach: We propose the combination of HSI and 3D profilometry to correct the images using the Lambert cosine law. The feasibility of the correction method is presented first on hemispherical tissue phantoms and next on human hands before, during, and after the vascular occlusion test (VOT). Results: Seven different phantoms with known optical properties were created and imaged with a hyperspectral system. The correction method worked up to 60 deg inclination angle, whereas for uncorrected images the maximum angles were 20 deg. Imaging hands before, during, and after VOT shows good agreement between the expected and extracted skin physiological parameters. Conclusions: The correction method was successfully applied on the images of tissue phantoms of known optical properties and geometry and VOT. The proposed method could be applied to any reflectance optical imaging technique and should be used whenever the sample parameters need to be extracted from a curved surface sample.

Estimating quantitative physiological and morphological tissue parameters of murine tumor models using hyperspectral imaging and optical profilometry

“…This study used a custom‐built multimodal optical imaging system combining a hyperspectral imaging (HSI) module and a three‐dimensional optical profilometry (OP) module presented in Figure 1. HSI was integrated with an optical profilometry module to obtain the surface shape of the imaged tissue and apply the curvature and height corrections [45] of hyperspectral images to compensate for the signal loss in areas with high inclination angles and distance variation. HSI is a push‐broom (line‐scanning) hyperspectral imaging device consisting of a monochrome CMOS camera (Blackfly S, BFS‐U3‐51S5M‐C, FLIR, Canada), an imaging spectrograph (ImSpector V10E, Specim, Finland), two motorized translation stages (8MT195, Standa, Lithuania), custom LED illumination panel spanning the spectral range of 400–1000 nm and crossed polarizers to minimize specular reflection.…”

“…Normalized hyperspectral images were then corrected for the signal loss due to the changing inclination of the object surface and distortions resulting from the varying distance between the object and the camera. Specifically, 3D OP data were analyzed to obtain the surface shape profile, and height and surface curvature corrections were applied as described by Rogelj et al [45] to flatten the hyperspectral intensity profiles at different surface inclinations.…”

“…HSI can be complemented with other non-invasive optical techniques to provide additional information about the biological tissue. A three-dimensional optical profilometry (OP) provides the tissue surface shape [45] that can be used to accurately calculate tumor volumes and eliminate the need to measure tumor sizes with a vernier caliper, a standard procedure [46,47] in assessing tumor volumes. Although optical profilometry is a widespread technique in industry and many scientific fields, it is still not common in biomedical optics to extract information about tumors or other biological tissue.…”

Daily monitoring of CT26 murine tumor model using hyperspectral imaging and optical profilometry

“…where Iraw is raw hyperspectral image intensity, Idark is the dark current, and Iwhite is white standard reference intensity 2 . Secondly, 3D OP data were analyzed, and normalized hyperspectral images were curvature-and height-corrected to minimize the tissue curvature effect 4 . Furthermore, corrected hyperspectral images were spectrally reduced to the range of 450-750 nm with 5 nm spectral resolution and spatially binned twofold in X and Y directions to facilitate image analysis.…”

“…Furthermore, 3D OP captures tissue surface shape and could detect tumor morphology changes or be used to calculate tumor volumes. Additionally, it could compensate for signal loss in HSI due to highly inclined tumor tissue surfaces 4 . Tissue properties of tumors can be determined from hyperspectral images using different methods.…”