Diffuse Reflectance Imaging Research Articles

A Review of the Application of the Laser-Light Backscattering Imaging Technique to Agricultural Products

Growing concerns about food safety and waste have increased consumer demand for high-quality agricultural products, particularly at the postharvest stage. This demand has prompted the development of non-destructive methods to assess or inspect the internal quality of fruits and vegetables. The backscattering imaging technique, also known as diffuse reflectance imaging, is considered a highly promising approach. Numerous studies have focused on practical applications, using laser light at selected wavelengths to develop quick multispectral methods. Due to the rapid interaction of photons with biological tissue, together with the highly computational performance of machine vision, backscattering imaging can offer a valuable alternative to traditional methods. Its primary benefits include quick measurements without chemical sample preparation, easy integration with high-throughput automatic quality control, and reduced waste, since this non-destructive technique does not damage samples. This review presents a comprehensive overview of backscattering imaging, including the measurement geometry, data analysis, and design considerations for vision systems. Additionally, it explores this technique’s advantages, challenges, and accuracy, as demonstrated using various case studies.

In vivo visualization of burn depth in skin tissue of rats using hemoglobin parameters estimated by diffuse reflectance spectral imaging.

Burn injuries represent a global public health problem that kills an estimated 180,000 people annually. Non-fatal burns result in prolonged hospitalization, disfigurement, and disability. The most common, convenient, and widely used method for assessing burn depth is physical or visual examination, but the accuracy of this method is reportedly poor (60% to 75%). Rapid, correct assessment of burn depth is very important for the optimal management and treatment of burn patients. New methods of burn depth assessment that are inexpensive, simple, rapid, non-contact, and non-invasive are therefore needed. The aim of this study was to propose an approach to visualize the spatial distribution of burn depth using hemoglobin parameters estimated from spectral diffuse reflectance imaging and to demonstrate the feasibility of the proposed approach for differentiating burn depth in a rat model of scald burn injury. The new approach to creating a spatial map of burn depth was based on canonical discriminant analysis (CDA) of total hemoglobin concentration, tissue oxygen saturation, and methemoglobin saturation as estimated from spectral diffuse reflectance images. Burns of three different degrees of severity were created in rat dorsal skin by 10-s exposure to water maintained at 70°C, 78°C, and 98°C, respectively. Spectral images for dorsal regions were acquired under anesthesia immediately after burn injury and at 24h, 48h, and 72h after injury. Most areas of images in the group with skin exposed to 70°C water and 98°C water were classified as 70°C burn and 98°C burn, respectively. In contrast, no significant difference between areas classified as 78°C burn and 98°C burn from 24h to 72h was evident in the group with skin exposed to 78°C water, suggesting that burn depth was heterogeneous. The proposed approach combining diffuse reflectance spectral imaging and CDA appears promising for differentiating 70°C burns from 78°C burns and 98°C burns, and 98°C burns from 70°C burns and 78°C burns at 24 to 72h after burn injury in a rat model of scald burn injury.

Diffuse reflectance spectroscopy and imaging for non-invasive objective assessment of genitourinary syndrome of menopause: a pilot study

The genitourinary symptom of menopause (GSM) affects up to 65% of women, resulting in symptoms such as vulvovaginal dryness, discomfort, and dysuria, which significantly impacts quality of life. The current assessment methods rely on subjective questionnaires that can be influenced by individual differences, as well as invasive measurements that are time-consuming and not easily accessible. In this study, we explore the potential of a non-invasive and objective assessment tool called diffuse reflectance spectroscopy and imaging (DRSI) to evaluate tissue chromophores, including water, lipid, oxyhemoglobin, and deoxyhemoglobin. These measurements provide information about moisture content, lipid levels, oxygen saturation, and blood fraction, which can serve as surrogate markers for genital estrogen levels. Our findings reveal distinct differences in these chromophores among pre, peri, and postmenopausal subjects. By using lipid and blood fraction tissue chromophores in a K-Nearest Neighbour classifier model, we achieved a prediction accuracy of 65% compared to vaginal maturation index (VMI) that is clinically used to assess estrogen-related hormonal changes. When age was included as the third feature, the accuracy increased to 78%. We believe that by refining the study protocol and configuring the fiber probe to examine tissue chromophores both in the superficial vulva skin for epidermal water content and the deeper layers, DRSI has the potential to provide objective diagnosis and aid in monitoring the treatment outcome of GSM.

Diffuse Reflection Imaging for Detection of Surface Defect Based on Machine Learning

Diffuse reflection imaging relies on the fundamental principles of light interaction with rough or matte surfaces, enabling light to scatter in various directions. Unlike specular reflection, which directs light in a single path, diffuse reflection occurs sporadically. Its distinctive quality lies in its effectiveness for imaging objects with irregular or nonreflective surfaces, offering comprehensive information challenging to attain through alternative imaging methods. As a burgeoning subfield within optical and computer vision technologies, diffuse reflection imaging holds immense potential across scientific, industrial, and medical domains. This abstract succinctly outlines the key aspects of diffuse reflection imaging and underscores its diverse applications, marking it as a promising and newly developed field with substantial implications.

Multi-wavelength interference phase imaging for automatic breast cancer detection and delineation using diffuse reflection imaging

Millions of women globally are impacted by the major health problem of breast cancer (BC). Early detection of BC is critical for successful treatment and improved survival rates. In this study, we provide a progressive approach for BC detection using multi-wavelength interference (MWI) phase imaging based on diffuse reflection hyperspectral (HS) imaging. The proposed findings are based on the measurement of the interference pattern between the blue (446.6 nm) and red (632 nm) wavelengths. We consider implementing a comprehensive image processing and categorization method based on the use of Fast Fourier (FF) transform analysis pertaining to a change in the refractive index between tumor and normal tissue. We observed that cancer growth affects tissue organization dramatically, as seen by persistently increased refractive index variance in tumors compared normal areas. Both malignant and normal tissue had different depth data collected from it that was analyzed. To enhance the categorization of ex-vivo BC tissue, we developed and validated a training classifier algorithm specifically designed for categorizing HS cube data. Following the application of signal normalization with the FF transform algorithm, our methodology achieved a high level of performance with a specificity (Spec) of 94% and a sensitivity (Sen) of 90.9% for the 632 nm acquired image categorization, based on preliminary findings from breast specimens under investigation. Notably, we successfully leveraged unstained tissue samples to create 3D phase-resolved images that effectively highlight the distinctions in diffuse reflectance features between cancerous and healthy tissue. Preliminary data revealed that our imaging method might be able to assist specialists in safely excising malignant areas and assessing the tumor bed following resection automatically at different depths. This preliminary investigation might result in an effective "in-vivo" disease description utilizing optical technology using a typical RGB camera with wavelength-specific operation with our quantitative phase MWI imaging methodology.

Multispectral Imaging Analysis of Skin Lesions in Patients with Neurofibromatosis Type 1.

Neurofibromatosis type 1 (NF1) is a rare disease, affecting around 1 in 3500 individuals in the general population. The rarity of the disease contributes to the scarcity of the available diagnostic and therapeutic approaches. Multispectral imaging is a non-invasive imaging method that shows promise in the diagnosis of various skin diseases. The device utilized for the present study consisted of four sets of narrow-band LEDs, including 526 nm, 663 nm, and 964 nm for diffuse reflectance imaging and 405 nm LEDs, filtered through a 515 nm long-pass filter, for autofluorescence imaging. RGB images were captured using a CMOS camera inside of the device. This paper presents the results of this multispectral skin imaging approach to distinguish the lesions in patients with NF1 from other more common benign skin lesions. The results show that the method provides a potential novel approach to distinguish NF1 lesions from other benign skin lesions.

The UV–vis‐NIR Broadband Ultrafast Flexible Sn‐Pb Perovskite Photodetector for Multispectral Imaging to Distinguish Substance and Foreign‐Body in Biological Tissues

AbstractMultispectral imaging plays an important role in many applications such as color recognition, substance distinction, and medical therapy. Although multicolor detection has been demonstrated in lead‐based perovskites, the limited near‐infrared responsivity and slow response impede their applications for identifying the substance. Herein, narrow bandgap highly stable Cs0.05MA0.45FA0.5Sn0.5Pb0.5I3 (Sn‐Pb) perovskite films with excellent crystallinity and selective growth orientation are realized by the synergy of a Sn‐Pb mixing method and electronegativity balance. The Sn‐Pb perovskite photodetector shows a broadband response from 350 to 1000 nm and high‐performance near‐infrared (NIR) detection with a fast response of 2.0 µs and excellent responsivity of 0.29 A W−1. Furthermore, flexible Sn‐Pb perovskite devices without any encapsulation in the air continuously exhibit fast response after 3000 bending cycles. In addition, the Sn‐Pb perovskite diffuse reflection imaging system is demonstrated for multispectral imaging and substance distinction. Meanwhile, foreign‐body identification in biological tissues by NIR imaging of Sn‐Pb perovskite photodetectors is further demonstrated, proving narrow bandgap mixed perovskite photodetectors an attractive candidate for biomedical imaging.

Evaluation of shelf life of egg treated with edible coating by means of NIR spectroscopy and laser induced diffuse reflectance imaging

A coating solution was developed by blending cassava starch at different levels (2%, 3% and 4% w/v) with gelatin and plasticizers to maintain the quality of eggs during 4 weeks of storage (25 ± 1 °C, 60–65% RH). This study suggests the rapid techniques of near-infrared (NIR) spectroscopy and laser-induced diffuse reflectance imaging for determining the internal quality of eggs. The scanning electron microscopy (SEM) micrographs showed that the coatings were effective in protecting eggshells. During storage, coated eggs had lower weight loss and albumen pH, higher Haugh unit and yolk index than control eggs (p < 0.05). These factors are the most common parameters in assessing egg quality. Among the coating formulas, the 4% starch coating had significantly higher effectiveness from the 3rd week of storage. The results indicated that the coating solution containing 4% starch could maintain the egg quality up to 28 days. Furthermore, the NIR spectra were used to develop prediction models for the investigated quality attributes using partial least squares regression (PLSR). Models were created using 3 preprocessing methods of standard normal variate (SNV), first derivative (lD) and second derivative (2D). The PLSR-SNV model achieved the best prediction for weight loss (R2 = 0.883, RPD = 2.920), Haugh unit (R2 = 0.756, RPD = 2.025), and yolk index (R2 = 0.807, RPD = 2.276). Laser scattering was successfully used to detect the egg quality change during storage by linear discriminant analysis (LDA) at wavelengths of 532 nm and 780 nm. The descriptive attributes extracted from intensity profiles showed significant effects of storage time, treatment and their interaction. This research highlighted the promising application of NIR and laser-induced diffuse reflectance imaging for inline control of egg quality at room temperature.

In vivo monitoring of hemoglobin derivatives in a rat thermal injury model using spectral diffuse reflectance imaging

IntroductionTo demonstrate the feasibility of our previously proposed Diffuse reflectance spectral imaging (DRSI) method for in vivo monitoring of oxygenated hemoglobin, deoxygenated hemoglobin, methemoglobin, tissue oxygen saturation, and methemoglobin saturation in a rat scald burn wound model and assess whether the method could be used for differentiating the burn depth groups in rats based on the hemoglobin parameters. MethodologySuperficial dermal burns (SDBs), deep dermal burns (DDBs), and deep burns (DBs) were induced in rat dorsal skin using a Walker–Mason method. An approach based on multiple regression analysis for spectral diffuse reflectance images aided by Monte Carlo simulations for light transport was used to quantify the hemoglobin parameters. Canonical discriminant analysis (CDA) was performed to discriminate SDB, DDB, and DB. ResultsCDA using the total hemoglobin concentration, tissue oxygen saturation, and methemoglobin saturation as the independent variables showed good performance for discriminating the SDB, DDB, and DB groups immediately after burn injury and the SDB group from the DDB and DB groups 24–72 h after burn injury. ConclusionsThe DRSI method with multiple regression analysis for quantification of oxygenated hemoglobin, deoxygenated hemoglobin, and methemoglobin proved to be reliable for monitoring these hemoglobin derivatives in the rat experimental burn injury model. The parameters of tissue oxygen saturation, methemoglobin saturation, and total hemoglobin concentration are promising for the differentiating the degree of burn injury using CDA.

A Cross-Sectional Study of the Dermatological Manifestations of Patients with Fabry Disease and the Assessment of Angiokeratomas with Multimodal Imaging.

Fabry disease (FD) is a multisystemic X-linked lysosomal storage disease that presents with angiokeratomas (AKs). Our objective was to investigate the clinical and morphologic features of AKs and to present two experimental techniques, multispectral imaging (MSI) and non-linear microscopy (NLM). A thorough dermatological examination was carried out in our 26 FD patients and dermoscopic images (n = 136) were evaluated for specific structures. MSI was used for the evaluation of AKs in seven patients. NLM was carried out to obtain histology samples of two AKs and two hemangiomas. Although AKs were the most common manifestation, the majority of patients presented an atypical distribution and appearance, which could cause a diagnostic challenge. Dermoscopy revealed lacunae (65%) and dotted vessels (56%) as the most common structures, with a whitish veil present in only 25%. Autofluorescence (405 nm) and diffuse reflectance (526 nm) images showed the underlying vasculature more prominently compared to dermoscopy. Using NLM, AKs and hemangiomas could be distinguished based on morphologic features. The clinical heterogeneity of FD can result in a diagnostic delay. Although AKs are often the first sign of FD, their presentation is diverse. A thorough dermatological examination and the evaluation of other cutaneous signs are essential for the early diagnosis of FD.

Sparsely sampled Fourier ptychography in diffuse reflection

Fourier ptychography microscopy combines the idea of aperture synthesis, which enables the synthesis of multiple low-resolution images in the frequency domain to achieve large field-of-view and high-resolution imaging results. The Fourier ptychography imaging technique applied to the field of far-field diffuse reflectance imaging needs to consider the impact of diffuse reflectance speckle formed by the object’s rough surface on the imaging results. Therefore, far-field diffuse reflectance Fourier ptychography often requires more than microscopic imaging of low-resolution images to achieve super-resolution. In response, we design a sparse sampling method that can reduce the number of required low-resolution images to one-fourth of the original sampling, and does not affect the imaging resolution. Experimental results show that our method can significantly improve imaging efficiency and achieve super-resolution far-field imaging with fast sampling.

Measurement of rat and human tissue optical properties for improving the optical detection and visualization of peripheral nerves.

Peripheral nerve damage frequently occurs in challenging surgical cases resulting in high costs and morbidity. Various optical techniques have proven effective in detecting and visually enhancing nerves, demonstrating their translational potential for assisting in nerve-sparing medical procedures. However, there is limited data characterizing the optical properties of nerves in comparison to surrounding tissues, thus limiting the optimization of optical nerve detection systems. To address this gap, the absorption and scattering properties of rat and human nerve, muscle, fat, and tendon were determined from 352-2500 nm. The optical properties highlighted an ideal region in the shortwave infrared for detecting embedded nerves, which remains a significant challenge for optical approaches. A 1000-1700 nm hyperspectral diffuse reflectance imaging system was used to confirm these results and identify optimal wavelengths for nerve imaging contrast in an in vivo rat model. Optimal nerve visualization contrast was achieved using 1190/1100 nm ratiometric imaging and was sustained for nerves embedded under ≥600 µm of fat and muscle. Overall, the results provide valuable insights for optimizing the optical contrast of nerves, including those embedded in tissue, which could lead to improved surgical guidance and nerve-sparing outcomes.

Conspectus on nanodiagnostics as an incipient platform for detection of oral potentially malignant disorders and oral squamous cell carcinoma.

Conspectus on nanodiagnostics as an incipient platform for detection of oral potentially malignant disorders and oral squamous cell carcinoma.

Research on Digital Testing Technology for Full Surface Defects of Cross scale Heteromorphic Metal Devices

There are many types of cross scale special-shaped metal components in various fields, and the surface quality (defects) of some key components will affect the device performance and even cause the long-term stability and reliability of the system to decline. The existing manual inspection methods are difficult to accurately quantify and establish a digital traceability database, so it is urgent to study the automatic digital inspection technology of full surface defects. However, most of the devices are curved surfaces with different shapes, large size spans, various types of surface defects and diffuse reflection imaging, and the background of machine vision images is complex, which greatly increases the difficulty of defect detection. Based on the principle of machine vision imaging, this paper designs a long depth of field and low distortion imaging system for curved surfaces. Combined with a flexible scanning motion mechanism with multiple degrees of freedom, this paper studies the technology of complex background defect extraction to realize the full surface defect detection of cross scale special-shaped metal devices.

479 Introduction of a Novel Multispectral Imaging Screening Algorithm to Distinguish Malignant Melanoma from Seborrheic Keratosis

Malignant melanoma (MM) is in the background of the majority of skin cancer-related mortality. On the other hand, seborrheic keratosis (SK) is a common benign lesion that in certain cases can mimic MM. In this work, we utilized a multispectral imaging device prototype with LED illumination to differentiate MM from SK, with the use of 405 nm autofluorescence and 525 and 660 nm diffuse reflectance imaging. Intensity descriptors of the captured images were analyzed, including the ratios, standard deviation and minimum and maximum of intensity values of the lesions in the investigated channels.

Ultrasensitive, flexible perovskite nanowire photodetectors with long‐term stability exceeding 5000 h

AbstractPhotodetectors (PDs) based on perovskite nanowires are among the most promising next‐generation photodetection technologies; however, their poor long‐term stability is the biggest challenge limiting their commercial application. Herein, an ionic liquid, 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIMBF4), is incorporated as an additive into methylammonium lead triiodide (MAPbI3) nanowires; this not only effectively passivates defects to inhibit perovskite degradation but also leads to the formation of nanochannels, enabling fast charge transfer. As a result, the long‐term stability and performance of MAPbI3 nanowires are considerably improved. The detectivity, linear detection range, and noise equivalent power of the MAPbI3 nanowire PD reach 2.06 × 1013 Jones, 160 dB, and 1.38 × 10−15 W Hz−1/2, respectively, comparable to the highest performance of perovskite nanowire PDs reported to date. Moreover, the unencapsulated PD can maintain 100% of its initial performance after being exposed to an open‐air environment for more than 5000 h, establishing it as the most stable perovskite nanowire PD reported to date. Notably, the PD exhibits improved diffuse reflection imaging ability when compared with commercial silicon photodiode S2386. This study provides a new strategy for constructing sensitive, stable, and flexible perovskite PDs and will accelerate their commercial application in the future.image

Rapid Quantification of Tissue Perfusion Properties with a Two-Stage Look-Up Table

Tissue perfusion properties reveal crucial information pertinent to clinical diagnosis and treatment. Multispectral spatial frequency domain imaging (SFDI) is an emerging imaging technique that has been widely used to quantify tissue perfusion properties. However, slow processing speed limits its usefulness in real-time imaging applications. In this study, we present a two-stage look-up table (LUT) approach that accurately and rapidly quantifies optical (absorption and reduced scattering maps) and perfusion (total hemoglobin and oxygen saturation maps) properties using stage-1 and stage-2 LUTs, respectively, based on reflectance images at 660 and 850 nm. The two-stage LUT can be implemented on both CPU and GPU computing platforms. Quantifying tissue perfusion properties using the simulated diffuse reflectance images, we achieved a quantification speed of 266, 174, and 74 frames per second for three image sizes 512 × 512, 1024 × 1024, and 2048 × 2048 pixels, respectively. Quantification of tissue perfusion properties was highly accurate with only 3.5% and 2.5% error for total hemoglobin and oxygen saturation quantification, respectively. The two-stage LUT has the potential to be integrated with dual-sensor cameras to enable real-time quantification of tissue hemodynamics.

Design of laser parameter measurement system based on diffuse reflection imaging

Design of laser parameter measurement system based on diffuse reflection imaging

Single-Fiber Diffuse Reflectance Spectroscopy and Spatial Frequency Domain Imaging in Surgery Guidance: A Study on Optical Phantoms.

Diffuse reflectance spectroscopy (DRS) and imaging are increasingly being used in surgical guidance for tumor margin detection during endoscopic operations. However, the accuracy of the boundary detection with optical techniques may depend on the acquisition parameters, and its evaluation is in high demand. In this work, using optical phantoms with homogeneous and heterogeneous distribution of chromophores mimicking normal and pathological bladder tissues, the accuracy of tumor margin detection using single-fiber diffuse reflectance spectroscopy and spatial frequency domain imaging was evaluated. We also showed how the diffuse reflectance response obtained at different spatial frequencies with the spatial frequency domain imaging technique could be used not only to quantitatively map absorption and scattering coefficients of normal tissues and tumor-like heterogeneities but also to estimate the tumor depth localization. The demonstrated results could be helpful for proper analysis of the DRS data measured in vivo and for translation of optical techniques for tumor margin detection to clinics.

In vivo sensing of cutaneous edema: A comparative study of diffuse reflectance, Raman spectroscopy and multispectral imaging.

Quantitative noninvasive assessment of water content in tissues is important for biomedicine. Optical spectroscopy is potentially capable of solving this problem; however, its applicability for clinical diagnostics remains questionable. The presented study compares diffuse reflectance spectroscopy, Raman spectroscopy and multispectral imaging in the characterization of cutaneous edema. The source-detector geometries for each method are selected based on Monte Carlo simulations results to detect the signal from the dermis. Then, the kinetics of the edema development is studied for two models. All methods demonstrate synchronous trends for histamine-induced edema: The water content reaches a maximum of 1 hour after histamine application and then gradually decreases. For the venous occlusion, a 51% increase in water content is observed with Raman spectroscopy. The differences in water content estimation by three methods are explained based on the light propagation model. The obtained results are essential for introducing quantitative optical water measurement technology to the clinics.