Near-infrared Reflectance Imaging Research Articles

Near-infrared imaging: an in vivo, non-invasive diagnostic tool in neurofibromatosis type 1.

Only a few reports in the literature have investigated the presence of ocular abnormalities in neurofibromatosis type 1 (NF-1) patients. The aim of this study was to evaluate the prevalence of ocular abnormalities in a large population of NF1 patients, focusing on the choroidal changes. This study was conducted on 160 consecutive patients with NF1 and 106 sex- and age-matched healthy subjects (control). Each patient underwent a complete ophthalmological examination inclusive of best-corrected visual acuity, intraocular pressure measurement, slit-lamp biomicroscopy, indirect fundus biomicroscopy, and near-infrared reflectance (NIR) retinography by using the spectral domain OCT. Moreover, all patients underwent complete dermatological exam and 1.5-Tesla MRI scan of the brain to assess the presence of optic nerve gliomas. Choroidal abnormalities were detected in 97% of patients, with a positive predictive value of 100% and a negative predictive value of 96.4%. Interestingly, a small number of patients (4/160; 2.5%) showed Lisch nodules without choroidal abnormalities, whereas a larger number of patents (22/160; 13.75%) presented choroidal lesions in absence of Lisch nodules. None of the patients showed the absence of both choroidal lesions and Lisch nodules. The number of choroidal lesions increased with age (r = 0.364, p = 0.0001) and with the severity of pathology (r = 0.23, p = 0.003). Any statistically significant correlation between choroidal lesions, visual acuity, and intraocular pressure was observed. NIR imaging represents an in vivo, non-invasive, sensitive and reproducible exam to detect choroidal nodules in NF-1 patients, suggesting that choroidal changes may represent an additional diagnostic criteria for NF1.

Consensus Definition for Atrophy Associated with Age-Related Macular Degeneration on OCT: Classification of Atrophy Report 3

To develop consensus terminology and criteria for defining atrophy based on OCT findings in the setting of age-related macular degeneration (AMD). Consensus meeting. Panel of retina specialists, image reading center experts, retinal histologists, and optics engineers. As part of the Classification of Atrophy Meetings (CAM) program, an international group of experts surveyed the existing literature, performed a masked analysis of longitudinal multimodal imaging for a series of eyes with AMD, and reviewed the results of this analysis to define areas of agreement and disagreement. Through consensus discussions at 3 meetings over 12 months, a classification system based on OCT was proposed for atrophy secondary to AMD. Specific criteria were defined to establish the presence of atrophy. A consensus classification system for atrophy and OCT-based criteria to identify atrophy. OCT was proposed as the reference standard or base imaging method to diagnose and stage atrophy. Other methods, including fundus autofluorescence, near-infrared reflectance, and color imaging, provided complementary and confirmatory information. Recognizing that photoreceptor atrophy can occur without retinal pigment epithelium (RPE) atrophy and that atrophy can undergo an evolution of different stages, 4 terms and histologic candidates were proposed: complete RPE and outer retinal atrophy (cRORA), incomplete RPE and outer retinal atrophy, complete outer retinal atrophy, and incomplete outer retinal atrophy. Specific OCT criteria to diagnose cRORA were proposed: (1) a region of hypertransmission of at least 250 μm in diameter, (2) a zone of attenuation or disruption of the RPE of at least 250 μm in diameter, (3) evidence of overlying photoreceptor degeneration, and (4) absence of scrolled RPE or other signs of an RPE tear. A classification system and criteria for OCT-defined atrophy in the setting of AMD has been proposed based on an international consensus. This classification is a more complete representation of changes that occur in AMD than can be detected using color fundus photography alone. Longitudinal information is required to validate the implied risk of vision loss associated with these terms. This system will enable such future studies to be undertaken using consistent definitions.

Cuticular Drusen: Clinical Phenotypes and Natural History Defined Using Multimodal Imaging

To define the range and life cycles of cuticular drusen phenotypes using multimodal imaging and to review the histologic characteristics of cuticular drusen. Retrospective, observational cohort study and experimental laboratory study. Two hundred forty eyes of 120 clinic patients with a cuticular drusen phenotype and 4 human donor eyes with cuticular drusen (n= 2), soft drusen (n= 1), and hard drusen (n= 1). We performed a retrospective review of clinical and multimodal imaging data of patients with a cuticular drusen phenotype. Patients had undergone imaging with various combinations of color photography, fluorescein angiography, indocyanine green angiography, near-infrared reflectance, fundus autofluorescence, high-resolution OCT, and ultrawide-field imaging. Human donor eyes underwent processing for high-resolution light and electron microscopy. Appearance of cuticular drusen in multimodal imaging and the topography of a cuticular drusen distribution; age-dependent variations in cuticular drusen phenotypes, including the occurrence of retinal pigment epithelium (RPE) abnormalities, choroidal neovascularization, acquired vitelliform lesions (AVLs), and geographic atrophy (GA); and ultrastructural and staining characteristics of druse subtypes. The mean age of patients at the first visit was 57.9±13.4 years. Drusen and RPE changes were seen in the peripheral retina, anterior to the vortex veins, in 21.8% of eyes. Of eyes with more than 5 years of follow-up, cuticular drusen disappeared from view in 58.3% of eyes, drusen coalescence was seen in 70.8% of eyes, and new RPE pigmentary changes developed in 56.2% of eyes. Retinal pigment epithelium abnormalities, AVLs, neovascularization, and GA occurred at a frequency of 47.5%, 24.2%, 12.5%, and 25%, respectively, and were significantly more common in patients older than 60 years of age (all P < 0.015). Occurrence of GA and neovascularization were important determinants of final visual acuity in eyes with the cuticular drusen phenotype (both P< 0.015). Small cuticular drusen typically demonstrated a homogenous ultrastructural appearance similar to hard drusen, whereas fragmentation of the central and basal contents was seen frequently in larger cuticular drusen. Although the ultrastructural characteristics of cuticular drusen appear more similar to those of hard drusen, their lifecycle and macular complications are more comparable with those of soft drusen. Cuticulardrusen phenotype may confer a unique risk for the development of GA and neovascularization.

Detection of blueberry internal bruising over time using NIR hyperspectral reflectance imaging with optimum wavelengths

Early detection of internal bruising is one of the major challenges in blueberry postharvest quality sorting processes. The potential of using near infrared (NIR) hyperspectral reflectance imaging (950–1650nm) with reduced spectral features was investigated for blueberry internal bruising detection 30min to 12h after mechanical impact. A least squares support vector machine (LS-SVM) was used to develop classification models to compute the spatial distribution of bruising based on the spectra extracted from regions of interest (ROIs) at four measurement times (30min, 2h, 6h, and 12h after mechanical impact). Three feature selection methods were used to select optimum wavelengths or band ratio images for bruising detection. The classification model, developed using optimum wavelengths selected by competitive adaptive reweighted sampling (CARS) (CARS-LS-SVM model) and full spectra (full spectra-LS-SVM), had similar performance in the identification of bruised blueberries. Band ratio images (1235nm/1035nm) achieved a comparable accuracy with the CARS-LS-SVM model at 6h, and higher accuracy than CARS-LS-SVM and full spectra-LS-SVM models at 12h. The overall classification accuracies of 77.5%, 83.8%, 92.5%, and 95.0% were obtained by band ratio images for blueberries 30min, 2h, 6h, and 12h after impact, respectively. In order to evaluate the performance of the proposed methods, additional validation samples were processed by the detection algorithm. The overall discrimination accuracies for healthy and bruised blueberries in the validation set were 93.3% and 98.0%, respectively, for CARS-LS-SVM model, and 93.3% and 95.9%, respectively, for band ratio images. The overall results indicated that NIR reflectance imaging can detect blueberry internal bruising as early as 30min after mechanical impact, and band ratio images computed from two wavelengths showed great potential to detect blueberry internal bruising on the packing line.

Ripeness monitoring of two cultivars of nectarine using VIS-NIR hyperspectral reflectance imaging

Visible–near-infrared (450–1040 nm) hyperspectral reflectance imaging was studied in order to assess the internal physicochemical properties and sensory perception of ‘Big Top’ and ‘Magique’ nectarines (Prunus persica L. Batsch var. nucipersica) (yellow and white-flesh cultivar, respectively) during ripening using the Ripening Index (RPI) and the Internal Quality Index (IQI). Hyperspectral images of the intact fruits were acquired during the ripeness under controlled conditions, and their physicochemical properties (flesh firmness, total soluble solids, titratable acidity and flesh colour) were analysed. IQI and RPI were used to relate the spectral information obtained from nectarines with the physicochemical properties and the sensory perception of their maturity using Partial Least Square (PLS) regression with proper variable selection. Optimal results were obtained with R2 values higher than 0.87 for the two indices and the two cultivars. The ripeness of each fruit could be visualised by projecting the PLS models of the IQI on the pixels of the fruits in the images, showing great potential for further monitoring of the evolution of intact nectarine ripeness in industrial setups.

Changes in reticular pseudodrusen area in eyes that progressed from early to late age-related macular degeneration.

This retrospective cohort study utilized 3 imaging modalities to analyze quantitatively reticular pseudodrusen (RPD) area changes in eyes that progressed from early to late age-related macular degeneration (AMD). Subjects with AMD, unilateral choroidal neovascularization (CNV), and early AMD with RPD in the fellow eye (the study eye) were included. The study eyes underwent indocyanine green angiography (ICGA), near-infrared reflectance (NIR-R), and short-wavelength autofluorescence (AF) imaging of the macula at baseline and at follow-up. Study eyes were analyzed for RPD and for the development of late AMD-CNV and/or geographic atrophy (GA). RPD area was measured at baseline and at follow-up as a percentage of the 30-degree field. During the study period (mean follow-up time 23.5±5.0months), 12/31 study eyes developed CNV and 4/31 developed GA. In the eyes that developed CNV, there was a statistically significant decrease in mean RPD area over the follow-up period as seen on AF (P<0.01) and NIR-R (P=0.01), and the decrease in mean RPD area approached statistical significance on ICGA (P=0.08). Using 3 en face imaging techniques, we demonstrate that RPD undergo dynamic spatiotemporal changes in eyes that progress from early AMD to CNV, namely a decrease in the area of lesions detected.

Differential Disease Progression in Atrophic Age-Related Macular Degeneration and Late-Onset Stargardt Disease.

To compare the disease course of retinal pigment epithelium (RPE) atrophy secondary to age-related macula degeneratio (AMD) and late-onset Stargardt disease (STGD1). Patients were examined longitudinally by fundus autofluorescence, near-infrared reflectance imaging, and best-corrected visual acuity (BCVA). Areas of RPE atrophy were quantified using semi-automated software, and the status of the fovea was evaluated based on autofluorescence and near-infrared reflectance images. Mixed-effects models were used to compare atrophy progression rates. BCVA loss and loss of foveal integrity were analyzed using Turnbull's estimator. A total of 151 patients (226 eyes) with RPE atrophy secondary to AMD and 38 patients (66 eyes) with RPE atrophy secondary to late-onset STGD1 were examined for a median time of 2.3 years (interquartile range, 2.7). Mean baseline age was 74.2 years (SD, 7.6) in AMD and 63.4 (SD, 9.9) in late-onset STGD1 (P = 1.1 × 10-7). Square root atrophy progression was significantly faster in AMD when compared with late-onset STGD1 (0.28 mm/year [SE, 0.01] vs. 0.23 [SE, 0.03]; P = 0.030). In late-onset STGD1, the median survival of the fovea was significantly longer when compared with eyes with AMD (8.60 vs. 3.35 years; P = 0.005) with a trend to a later BCVA loss of ≥3 lines (5.97 vs. 4.37 years; P = 0.382). These natural history data indicate differential disease progression in AMD versus late-onset STGD1. The results underline the relevance of refined phenotyping in elderly patients presenting with RPE atrophy in regard to prognosis and design of interventional trials.

Standoff chemical imaging finds evidence for Jackson Pollock's selective use of alkyd and oil binding media in a famous ‘drip’ painting

Near-infrared diffuse reflectance imaging spectroscopy (NIR-RIS, 1000 to 2500 nm) was used to map the use of alkyd and oil paints in Jackson Pollock'sNumber 1, 1950(Lavender Mist), one of his most important ‘drip’ or ‘poured’ paintings.

Natural History of the Central Structural Abnormalities in Choroideremia: A Prospective Cross-Sectional Study

To describe in detail the central retinal structure of a large group of patients with choroideremia (CHM). A prospective, cross-sectional, descriptive study. Patients (n= 97, age 6-71 years) with CHM and subjects with normal vision (n= 44; ages 10-50 years) were included. Subjects were examined with spectral-domain optical coherence tomography (SD OCT) and near-infrared reflectance imaging. Visual acuity (VA) was measured during their encounter or obtained from recent ophthalmic examinations. Visual thresholds were measured in a subset of patients (n= 24) with automated static perimetry within the central regions (±15°) examined with SD OCT. Visual acuity and visual thresholds; total nuclear layer, inner nuclear layer (INL), and outer nuclear layer (ONL) thicknesses; and horizontal extent of the ONL and the photoreceptor outer segment (POS) interdigitation zone (IZ). Earliest abnormalities in regions with normally appearing retinal pigment epithelium (RPE) were the loss of the POS and ellipsoid zone associated with rod dysfunction. Transition zones (TZs) from relatively preserved retina to severe ONL thinning and inner retinal thickening moved centripetally with age. Most patients (88%) retained VAs better than 20/40 until their fifth decade of life. The VA decline coincided with migration of the TZ near the foveal center. There were outer retinal tubulations in degenerated, nonatrophic retina in the majority (69%) of patients. In general, RPE abnormalities paralleled photoreceptor degeneration, although there were regions with detectable but abnormally thin ONL co-localizing with severe RPE depigmentation and choroidal thinning. Abnormalities of the POS and rod dysfunction are the earliest central abnormalities observed in CHM. Foveal function is relatively preserved until the fifth decade of life. Migration of the TZs to the foveal center with foveal thinning and structural disorganization heralded central VA loss. The relationships established may help outline the eligibility criteria and outcome measures for clinical trials for CHM.

Use of MultiColor imaging in the assessment of suspected papilledema in 20 consecutive children

To investigate the use of MultiColor Scanning Laser Imaging as an adjunct to traditional imaging modalities in the assessment of children with suspected disk swelling. In this study of 20 consecutive children with suspected papilledema, MultiColor imaging was performed on all patients in addition to fundus examination, fundus autofluorescence, disk spectral domain optical coherence tomography (SD-OCT), and disk retinal nerve fiber layer thickness (RNFL) measurement. Diagnoses were determined in all 20 patients, and all images were evaluated by a medical retina specialist. Of the 20 cases (average age 11years [range, 5-16years]; 10 males), papilledema was confirmed in 11 (55%) and pseudopapilledema diagnosed in 9 (45%). Of pseudopapilledema cases, there were 4 cases of optic disk drusen, 2 hypermetropic disks, 2 "crowded disks," and 1 anomalous disk. In patients with true papilledema, on the combined MultiColor image, a green shift in the form of an elevated green ring was seen consistently. This ring was also hyperreflective on the blue and green images and surrounded a central "shadow," which was seen best on near infrared reflectance (NIR). The disk margins and vasculature were obscured on the combined, green, blue, and NIR images. These changes were not present in the pseudopapilledema cases. MultiColor imaging of disks with papilledema shows characteristic changes that may prove useful in differentiating true papilledema from pseudopapilledema. It is therefore a useful adjunct to traditional disk imaging modalities in assessing children with suspected disk swelling.

Nondestructive Detection and Quantification of Blueberry Bruising using Near-infrared (NIR) Hyperspectral Reflectance Imaging.

Currently, blueberry bruising is evaluated by either human visual/tactile inspection or firmness measurement instruments. These methods are destructive, time-consuming, and subjective. The goal of this paper was to develop a non-destructive approach for blueberry bruising detection and quantification. Experiments were conducted on 300 samples of southern highbush blueberry (Camellia, Rebel, and Star) and on 1500 samples of northern highbush blueberry (Bluecrop, Jersey, and Liberty) for hyperspectral imaging analysis, firmness measurement, and human evaluation. An algorithm was developed to automatically calculate a bruise ratio index (ratio of bruised to whole fruit area) for bruise quantification. The spectra of bruised and healthy tissues were statistically separated and the separation was independent of cultivars. Support vector machine (SVM) classification of the spectra from the regions of interest (ROIs) achieved over 94%, 92%, and 96% accuracy on the training set, independent testing set, and combined set, respectively. The statistical results showed that the bruise ratio index was equivalent to the measured firmness but better than the predicted firmness in regard to effectiveness of bruise quantification, and the bruise ratio index had a strong correlation with human assessment (R2 = 0.78 − 0.83). Therefore, the proposed approach and the bruise ratio index are effective to non-destructively detect and quantify blueberry bruising.

Near-Infrared Confocal Laser Reflectance Cytoarchitectural Imaging of the Substantia Nigra and Cerebellum in the Fresh Human Cadaver

Cytoarchitectural neuroimaging remains critical for diagnosis of many brain diseases. Fluorescent dye-enhanced, near-infrared confocal in situ cellular imaging of the brain has been reported. However, impermeability of the blood-brain barrier to most fluorescent dyes limits clinical utility of this modality. The differential degree of reflectance from brain tissue with unenhanced near-infrared imaging may represent an alternative technique for in situ cytoarchitectural neuroimaging. We assessed the utility of unenhanced near-infrared confocal laser reflectance imaging of the cytoarchitecture of the cerebellum and substantia nigra in 2 fresh human cadaver brains using a confocal near-infrared laser probe. Cellular images based on near-infrared differential reflectance were captured at depths of 20-180 μm from the brain surface. Parts of the cerebellum and substantia nigra imaged using the probe were subsequently excised and stained with hematoxylin and eosin for histologic correlation. Near-infrared reflectance imaging revealed the 3-layered cytoarchitecture of the cerebellum, with Purkinje cells appearing hyperreflectant. In the substantia nigra, neurons appeared hyporeflectant with hyperreflectant neuromelanin cytoplasmic inclusions. Cytoarchitecture of the cerebellum and substantia nigra revealed on near-infrared imaging closely correlated with the histology on hematoxylin-eosin staining. We showed that unenhanced near-infrared reflectance imaging of fresh human cadaver brain can reliably identify and distinguish neurons and detailed cytoarchitecture of the cerebellum and substantia nigra.

Multimodal Imaging of Vitreoretinal Lymphoma

Purpose: To assess the characteristics and prevalence of fundus abnormalities in vitreoretinal lymphoma (VRL) using multimodal imaging. Methods: We retrospectively reviewed chart and imaging studies of patients diagnosed with VRL. Results: All 10 VRL patients (14 eyes) included in the study showed vitreitis, hyperreflective lesions on near-infrared reflectance imaging, and hypoautofluorescent lesions on fundus autofluorescence. Other findings included hypofluorescent lesions on fluorescein angiography (79%), hypocyanescent lesions on indocyanine green angiography (77%), small retinal pigment epithelium detachments (PEDs) (71%) and large PEDs (36%) on optical coherence tomography (OCT). Outer retinal layer nodularity was identified on OCT in 93% of cases. Small PEDs corresponded to hyperreflective, hyperautofluorescent, hypofluorescent, hypocyanescent lesions. Conclusion: Multiple signs were present on multimodal imaging in VRL eyes. Lymphomatous infiltration created focal PEDs showing abnormal imaging signals. Outer retinal layer nodularity could represent an additional sign of infiltration. Multimodal imaging may guide physicians in the early diagnosis of VRL.

Near-infrared reflectance and autofluorescence imaging characteristics of choroidal nevi.

PurposeTo report near-infrared reflectance (NIR-R), near-infrared autofluorescence (NIR-AF) and blue wave autofluorescence (BW-AF) appearance of choroidal nevi using a confocal scanning laser ophthalmoscope (cSLO).Patients and methodsNIR-R, NIR-AF and BW-AF images of choroidal nevi were compared with color fundus photos (CF). Images were graded as hyperreflective if reflectance was much greater than background, hyporeflective if less than background, and isoreflective if the same as the background.ResultsForty-two nevi of 39 patients were imaged. When compared with CF, nevi could be identified on 95% (40/42) NIR-R images (95% CI: 83.5-99.3). On NIR-R 71% (30/42) demonstrated hyperreflectance and 24% (10/42) were hyporeflective. Hyperreflectivity was demonstrated in 96% (23/24) of NIR-AF images (95% CI: 79.1-99.9) and 34% (14/41) of BW-AF images (95% CI: 20.0-50.5). On NIR-R, 29/40 (73%) were apparently smaller in comparison with CF and 11/40 (28%) had the same area. A correlation was found between NIR-R and NIR-AF (P=0.02) but not with BW-AF (P=0.15).ConclusionsNevi can be visualized well using NIR-R and NIR-AF imaging modalities, but are less frequently visible using BW-AF. These changes may be related to melanin within the choroid or chronic changes of the overlying retinal pigment epithelium.

Choroidal Freckling in Pediatric Patients Affected by Neurofibromatosis Type 1

Greater understanding of choroidal freckling in patients affected by neurofibromatosis type 1 (NF1) has changed the previous belief that choroidal lesions are unusual in eyes with this disease. In fact, the high frequency of freckling suggests that the choroid is a structure commonly affected in patients with NF1. A review of patients aged 16 years or younger was performed. Recent studies using near-infrared reflectance imaging have shown that choroidal freckling frequently occurred in pediatric patients. As a result of these findings, some authors have suggested that choroidal freckling should be considered as a new diagnostic criterion for NF1. [J Pediatr Ophthalmol Strabismus. 2016;53(5):271-274.].

In vivo fluorescence imaging of hepatocellular carcinoma xenograft using near-infrared labeled epidermal growth factor receptor (EGFR) peptide.

Minimally-invasive surgery of hepatocellular carcinoma (HCC) can be limited by poor tumor visualization with white light. We demonstrate systemic administration of a Cy5.5-labeled peptide specific for epidermal growth factor receptor (EGFR) to target HCC in vivo in a mouse xenograft model. We attached a compact imaging module to the proximal end of a medical laparoscope to collect near-infrared fluorescence and reflectance images concurrently at 15 frames/sec. We measured a mean target-to-background ratio of 2.99 ± 0.22 from 13 surgically exposed subcutaneous human HCC tumors in vivo in 5 mice. This integrated imaging methodology is promising to guide laparoscopic resection of HCC.

Spectral-Domain Optical Coherence Tomography Angiography Findings in Multifocal Choroiditis With Active Lesions

To describe optical coherence tomography angiography (OCTA) findings in multifocal choroiditis (MFC) with active lesions and to characterize the concordance between the OCTA and other traditional imaging modalities. Reliability and validity analysis. Patients with suspected choroidal neovascularization (CNV) or acute inflammatory lesions associated with MFC were assessed in this study. All participants underwent preliminary traditional multimodal imaging including color fundus photography, fundus autofluorescence, near-infrared reflectance imaging, spectral-domain optical coherence tomography, and fluorescence angiography (FA). The participants were prospectively recruited to perform OCTA. OCTA findings of active lesions were compared with other traditional imaging results. Vascular flow signal representing CNV was identified, and a quantitative analysis of CNV size was performed on OCTA. Fifty-two eyes of 26 MFC patients (14 were bilaterally affected and 12 were unilaterally affected) wereincluded. Among the 23 active CNV cases, 20 were confirmed on OCTA while the other 3 were invalid owing to severe motion artifacts. OCTA of CNV showed a well-circumscribed vascular network (mean flow area, 0.271mm(2) [± 0.144mm(2)]). Among the 34 inflammatory lesions in 13 eyes, 32 showed no blood flow in the outer retina on OCTA while the other 2 showed blood flow signal. OCTA has a predominant advantage in differentiating CNV from inflammatory lesions. It also allows the visualization of detailed vascular structure of CNV and the function of flow area measurement realizes the quantitative analysis of CNV. Hence, it could be an alternative option for CNV identification and may better guide treatment.

Quantification of retinal layer thickness changes in acute macular neuroretinopathy

PurposeTo quantitatively evaluate retinal layer thickness changes in acute macular neuroretinopathy (AMN).MethodsAMN areas were identified using near-infrared reflectance (NIR) images. Intraretinal layer segmentation using Heidelberg software was performed. The inbuilt...

Activity assessment of root caries lesions with thermal and near-IR imaging methods.

The purpose of this study was to evaluate thermal and near-infrared (NIR) reflectance imaging methods for the assessment of the activity of root caries lesions. In addition, changes in the lesion structure were monitored with polarization sensitive optical coherence tomography (PS-OCT). Artificial bovine and natural root caries lesions were imaged with PS-OCT, and their dehydration rate was measured with thermal and NIR cameras. The lesion activity of the natural root caries samples was also assessed by two clinicians by conventional means according to ICDAS II guidelines. The thickness of the highly mineralized transparent surface layer measured using PS-OCT increased and the area enclosed by the time-temperature curve, ΔQ, measured with thermal imaging decreased significantly with longer periods of remineralization in simulated dentin lesions, but the NIR reflectance intensity differences, ΔI, failed to show any significant relationship with the degree of remineralization. The PS-OCT algorithm for the automated assessment of remineralization successfully detected the highly mineralized surface layer on both natural and simulated lesions. Thermal imaging provided the most accurate diagnosis of root caries lesion activity. These results demonstrate that thermal imaging and PS-OCT may be ideally suited for the nondestructive root caries lesion activity during a clinical examination.

Penetration Depth Measurement of Near-Infrared Hyperspectral Imaging Light for Milk Powder.

The increasingly common application of the near-infrared (NIR) hyperspectral imaging technique to the analysis of food powders has led to the need for optical characterization of samples. This study was aimed at exploring the feasibility of quantifying penetration depth of NIR hyperspectral imaging light for milk powder. Hyperspectral NIR reflectance images were collected for eight different milk powder products that included five brands of non-fat milk powder and three brands of whole milk powder. For each milk powder, five different powder depths ranging from 1 mm–5 mm were prepared on the top of a base layer of melamine, to test spectral-based detection of the melamine through the milk. A relationship was established between the NIR reflectance spectra (937.5–1653.7 nm) and the penetration depth was investigated by means of the partial least squares-discriminant analysis (PLS-DA) technique to classify pixels as being milk-only or a mixture of milk and melamine. With increasing milk depth, classification model accuracy was gradually decreased. The results from the 1-mm, 2-mm and 3-mm models showed that the average classification accuracy of the validation set for milk-melamine samples was reduced from 99.86% down to 94.93% as the milk depth increased from 1 mm–3 mm. As the milk depth increased to 4 mm and 5 mm, model performance deteriorated further to accuracies as low as 81.83% and 58.26%, respectively. The results suggest that a 2-mm sample depth is recommended for the screening/evaluation of milk powders using an online NIR hyperspectral imaging system similar to that used in this study.