Displaying publications 1 - 20 of 102 in total

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  1. Potapov AL, Loginova MM, Moiseev AA, Radenska-Lopovok SG, Kuznetsov SS, Kuznetsova IA, et al.
    Sovrem Tekhnologii Med, 2023;15(1):53-60.
    PMID: 37388751 DOI: 10.17691/stm2023.15.1.06
    The aim of the study was to identify different degrees of dermal lesions in vulvar lichen sclerosus (VLS) using cross-polarization optical coherence tomography (CP OCT) based on attenuation coefficient to detect disease early manifestations and to monitor the effectiveness of treatment.

    MATERIALS AND METHODS: The study included 10 patients without pathology and 39 patients with VLS diagnosed histologically. CP OCT was performed in vivo on the inner surface of the labia minora, in the main lesion area. From each scanning point, a 3.4×3.4×1.25-mm3 3D data array was obtained in 26 s. CP OCT examination results were compared with histological examination of specimens stained with Van Gieson's picrofuchsin.Quantitative analysis of OCT images was performed by measuring the attenuation coefficient in co-polarization and cross-polarization. For visual analysis, color-coded charts were developed based on OCT attenuation coefficients.

    RESULTS: According to histological examination, all patients with VLS were divided into 4 groups as per dermal lesion degree: initial (8 patients); mild (7 patients); moderate (9 patients); severe (15 patients). Typical features of different degrees were interfibrillary edema up to 250 μm deep for initial degree, thickened collagen bundles without edema up to 350 μm deep for mild degree, dermis homogenization up to 700 μm deep for moderate degree, dermis homogenization and total edema up to 1200 μm deep for severe degree.Pathological processes in dermis during VLS like interfibrillary edema and collagen bundles homogenization were visualized using CP OCT method based on values of attenuation coefficient in co- and cross-polarization channels. However, CP OCT method appeared to be less sensitive to changes of collagen bundles thickness not allowing to distinguish thickened collagen bundles from normal ones with enough statistical significance. The CP OCT method was able to differentiate all degrees of dermal lesions among themselves. OCT attenuation coefficients differed from normal condition with statistical significance for all degrees of lesions, except for mild.

    CONCLUSION: For the first time, quantitative parameters for each degrees of dermis lesion in VLS, including initial degree, were determined by CP OCT method allowing to detect the disease at an early stage and to monitor the applied clinical treatment effectiveness.

    Matched MeSH terms: Tomography, Optical Coherence*
  2. Mohamad Saberi FN, Sukumaran P, Ung NM, Liew YM
    Biomed Eng Online, 2022 Dec 03;21(1):83.
    PMID: 36463182 DOI: 10.1186/s12938-022-01055-x
    Tooth demineralization is one of the most common intraoral diseases, encompassing (1) caries caused by acid-producing bacteria and (2) erosion induced by acid of non-bacterial origin from intrinsic sources (e.g. stomach acid reflux) and extrinsic sources (e.g. carbonated drinks). Current clinical assessment based on visual-tactile examination and standardized scoring systems is insufficient for early detection. A combination of clinical examination and technology is therefore increasingly adapted. This paper reviews various procedures and technologies that have been invented to diagnose and assess the severity of tooth demineralization, with focus on optical coherence tomography (OCT). As a micron-resolution non-invasive 3D imaging modality, variants of OCT are now available, offering many advantages under different working principles for detailed analytical assessment of tooth demineralization. The roles, capabilities and impact of OCT against other state-of-the-art technologies in both clinical and research settings are described. (139 words).
    Matched MeSH terms: Tomography, Optical Coherence*
  3. Saberi FNM, Liew YM, Sukumaran P, Ung NM
    Photodiagnosis Photodyn Ther, 2023 Sep;43:103715.
    PMID: 37481146 DOI: 10.1016/j.pdpdt.2023.103715
    Head and neck cancer patients are prone to dental caries after radiotherapy. An ex-vivo study was conducted to assess the feasibility of optical coherence tomography (OCT) to detect tooth demineralization due to caries in irradiated teeth. Thirty-nine human molar teeth were subjected to caries lesion induction through irradiation (Group 1), pH cycling (Group 2-1), and both (Group 2-2). The OCT signal attenuation coefficient, µR was assessed and validated against microhardness test and scanning electron microscope (SEM). The µR for Group 1 increased from 10 Gy to 40 Gy, and subsequently decreased after irradiated to 50 Gy and 60 Gy due to damaged enamel microstructure. In Group 2-1, the µR decreased with duration of pH cycling from day 1 to day 14 due to the increase of porosity in enamel layer. However, the µR showed decreasing trend from day 14 to day 28 of pH cycling, resulted from mineral deposition in the enamel layer. Although no significant difference was found in the µR between Group 2-1 and 2-2, SEM of Group 2-2 demonstrated visually higher porosity and larger gaps between microstructures. Irradiation may accelerate caries damage to tooth microstructure by increasing its porosity and brittleness, but larger sample size may be needed to further prove the effect. OCT could potentially be used for early detection of tooth demineralization in vivo based on the measurable µR changes for all groups which are shown negatively correlated with microhardness value (p 
    Matched MeSH terms: Tomography, Optical Coherence/methods
  4. Kee AR, Yip VCH, Tay ELT, Lim CW, Cheng J, Teo HY, et al.
    BMC Ophthalmol, 2020 Nov 10;20(1):440.
    PMID: 33167902 DOI: 10.1186/s12886-020-01701-9
    BACKGROUND: To understand the differences between two different optical coherence tomography angiography (OCTA) devices in detecting glaucomatous from healthy eyes by comparing their vascular parameters, diagnostic accuracy and test-retest reliability.

    METHODS: A cross-sectional observational study was performed on healthy and glaucoma subjects, on whom two sets of OCTA images of optic disc and macula were acquired using both AngioVue (Optovue, USA) and Swept Source (Topcon, Japan) OCTA devices during one visit. A novel in-house software was used to calculate the vessel densities. Diagnostic accuracy of the machines in differentiating healthy versus glaucomatous eyes was determined using area under the receiver operating characteristic curve (AUROC) and test-retest repeatability of the machines was also evaluated.

    RESULTS: A total of 80 healthy and 38 glaucomatous eyes were evaluated. Glaucomatous eyes had reduced mean vessel density compared to healthy controls in all segmented layers of the optic disc and macula using AngioVue (p ≤ 0.001). However, glaucomatous eyes had higher mean vessel density on optic disc scans using Swept Source, with lack of statistically significant difference between healthy and glaucomatous eyes. The AUROC showed better diagnostic accuracy of AngioVue (0.761-1.000) compared to Swept Source (0.113-0.644). The test-retest reliability indices were generally better using AngioVue than Swept Source.

    CONCLUSIONS: AngioVue showed better diagnostic capability and test-retest reliability compared to Swept Source. Further studies need to be undertaken to evaluate if there is any significant difference between the various machines in diagnosing and monitoring glaucoma.

    Matched MeSH terms: Tomography, Optical Coherence*
  5. Teo ZL, Sun CZ, Chong CCY, Tham YC, Takahashi K, Majithia S, et al.
    Ophthalmol Retina, 2022 Nov;6(11):1080-1088.
    PMID: 35580772 DOI: 10.1016/j.oret.2022.05.010
    OBJECTIVE: To describe the normative quantitative parameters of the macular retinal vasculature, as well as their systemic and ocular associations using OCT angiography (OCTA).

    DESIGN: Population-based, cross-sectional study.

    SUBJECTS: Adults aged > 50 years were recruited from the third examination of the population-based Singapore Malay Eye Study.

    METHODS: All participants underwent a standardized comprehensive examination and spectral-domain OCTA (Optovue) of the macula. OCT angiography scans that revealed pre-existing retinal disease, revealed macular pathology, and had poor quality were excluded.

    MAIN OUTCOME MEASURES: The normative quantitative vessel densities of the superficial layer, deep layer, and foveal avascular zone (FAZ) were evaluated. Ocular and systemic associations with macular retinal vasculature parameters were also evaluated in a multivariable analysis using linear regression models with generalized estimating equation models.

    RESULTS: We included 1184 scans (1184 eyes) of 749 participants. The mean macular superficial vessel density (SVD) and deep vessel density (DVD) were 45.1 ± 4.2% (95% confidence interval [CI], 37.8%-51.4%) and 44.4 ± 5.2% (95% CI, 36.9%-53.2%), respectively. The mean SVD and DVD were highest in the superior quadrant (48.7 ± 5.9%) and nasal quadrant (52.7 ± 4.6%), respectively. The mean FAZ area and perimeter were 0.32 ± 0.11 mm2 (95% CI, 0.17-0.51 mm) and 2.14 ± 0.38 mm (95% CI, 1.54-2.75 mm), respectively. In the multivariable regression analysis, female sex was associated with higher SVD (β = 1.25, P ≤ 0.001) and DVD (β = 0.75, P = 0.021). Older age (β = -0.67, P < 0.001) was associated with lower SVD, whereas longer axial length (β = -0.42, P = 0.003) was associated with lower DVD. Female sex, shorter axial length, and worse best-corrected distance visual acuity were associated with a larger FAZ area. No association of a range of systemic parameters with vessel density was found.

    CONCLUSIONS: This study provided normative macular vasculature parameters in an adult Asian population, which may serve as reference values for quantitative interpretation of OCTA data in normal and disease states.

    Matched MeSH terms: Tomography, Optical Coherence*
  6. Alsaih K, Yusoff MZ, Tang TB, Faye I, Mériaudeau F
    Comput Methods Programs Biomed, 2020 Oct;195:105566.
    PMID: 32504911 DOI: 10.1016/j.cmpb.2020.105566
    BACKGROUND AND OBJECTIVES: Aged people usually are more to be diagnosed with retinal diseases in developed countries. Retinal capillaries leakage into the retina swells and causes an acute vision loss, which is called age-related macular degeneration (AMD). The disease can not be adequately diagnosed solely using fundus images as depth information is not available. The variations in retina volume assist in monitoring ophthalmological abnormalities. Therefore, high-fidelity AMD segmentation in optical coherence tomography (OCT) imaging modality has raised the attention of researchers as well as those of the medical doctors. Many methods across the years encompassing machine learning approaches and convolutional neural networks (CNN) strategies have been proposed for object detection and image segmentation.

    METHODS: In this paper, we analyze four wide-spread deep learning models designed for the segmentation of three retinal fluids outputting dense predictions in the RETOUCH challenge data. We aim to demonstrate how a patch-based approach could push the performance for each method. Besides, we also evaluate the methods using the OPTIMA challenge dataset for generalizing network performance. The analysis is driven into two sections: the comparison between the four approaches and the significance of patching the images.

    RESULTS: The performance of networks trained on the RETOUCH dataset is higher than human performance. The analysis further generalized the performance of the best network obtained by fine-tuning it and achieved a mean Dice similarity coefficient (DSC) of 0.85. Out of the three types of fluids, intraretinal fluid (IRF) is more recognized, and the highest DSC value of 0.922 is achieved using Spectralis dataset. Additionally, the highest average DSC score is 0.84, which is achieved by PaDeeplabv3+ model using Cirrus dataset.

    CONCLUSIONS: The proposed method segments the three fluids in the retina with high DSC value. Fine-tuning the networks trained on the RETOUCH dataset makes the network perform better and faster than training from scratch. Enriching the networks with inputting a variety of shapes by extracting patches helped to segment the fluids better than using a full image.

    Matched MeSH terms: Tomography, Optical Coherence
  7. Ch'ng TW, Gillmann K, Hoskens K, Rao HL, Mermoud A, Mansouri K
    Eye (Lond), 2020 03;34(3):562-571.
    PMID: 31409906 DOI: 10.1038/s41433-019-0560-6
    OBJECTIVES: To determine the effect of surgical intraocular pressure (IOP) lowering on peripapillary retinal nerve fibre layer thickness (RNFL), fovea avascular zone (FAZ), peripapillary and macular vessel density (VD) in glaucoma using with optical coherence tomography angiography (OCT-A).

    METHODS: This was a prospective observational study performed at the Glaucoma Research Centre, Montchoisi Clinic, Lausanne. In total 40 eyes with open-angle glaucoma were included. OCT-A scans were performed before glaucoma surgery, and at 1-month, 3-month, 6-month, and 12-month post-operatively. AngioVue AngioAnalytic (Optovue Inc, Fremont, CA) software was used to analyse the RNFL, FAZ, peripapillary and macular VD. Changes were analysed using analysis of variance (ANOVA) models.

    RESULTS: Mean IOP dropped from 19.4 (±7.0) mmHg pre-surgery and stabilized at 13.0 (±3.1) mmHg at 12 months (p 

    Matched MeSH terms: Tomography, Optical Coherence
  8. Mat Nor MN, Guo CX, Green CR, Squirrell D, Acosta ML
    J Anat, 2023 Oct;243(4):697-705.
    PMID: 37222261 DOI: 10.1111/joa.13889
    The aim of this study is to correlate small dot hyper-reflective foci (HRF) observed in spectral domain optical coherence tomography (SD-OCT) scans of an animal model of hyperglycaemia with focal electroretinography (fERG) response and immunolabelling of retinal markers. The eyes of an animal model of hyperglycaemia showing signs of diabetic retinopathy (DR) were imaged using SD-OCT. Areas showing dot HRF were further evaluated using fERG. Retinal areas enclosing the HRF were dissected and serially sectioned, stained and labelled for glial fibrillary acidic protein (GFAP) and a microglial marker (Iba-1). Small dot HRF were frequently seen in OCT scans in all retinal quadrants in the inner nuclear layer or outer nuclear layer in the DR rat model. Retinal function in the HRF and adjacent areas was reduced compared with normal control rats. Microglial activation was detected by Iba-1 labelling and retinal stress identified by GFAP expression in Müller cells observed in discrete areas around small dot HRF. Small dot HRF seen in OCT images of the retina are associated with a local microglial response. This study provides the first evidence of dot HRF correlating with microglial activation, which may allow clinicians to better evaluate the microglia-mediated inflammatory component of progressive diseases showing HRF.
    Matched MeSH terms: Tomography, Optical Coherence
  9. Ibrahim S, Yunus MA, Green RG, Dutton K
    ISA Trans, 2012 Nov;51(6):821-6.
    PMID: 22624831 DOI: 10.1016/j.isatra.2012.04.010
    Optical tomography provides a means for the determination of the spatial distribution of materials with different optical density in a volume by non-intrusive means. This paper presents results of concentration measurements of gas bubbles in a water column using an optical tomography system. A hydraulic flow rig is used to generate vertical air-water two-phase flows with controllable bubble flow rate. Two approaches are investigated. The first aims to obtain an average gas concentration at the measurement section, the second aims to obtain a gas distribution profile by using tomographic imaging. A hybrid back-projection algorithm is used to calculate concentration profiles from measured sensor values to provide a tomographic image of the measurement cross-section. The algorithm combines the characteristic of an optical sensor as a hard field sensor and the linear back projection algorithm.
    Matched MeSH terms: Tomography, Optical/methods*
  10. Wang L, Tan H, Yu J, ZhangBao J, Huang W, Chang X, et al.
    Eur J Neurol, 2023 Feb;30(2):443-452.
    PMID: 36286605 DOI: 10.1111/ene.15612
    BACKGROUND AND PURPOSE: The aim was to evaluate the potential of retinal nerve fiber layer thickness (RNFLT) measured with optical coherence tomography in predicting disease progression in relapsing-remitting multiple sclerosis (RRMS).

    METHODS: Analyses were conducted post hoc of this 24-month, phase III, double-blind study, in which RRMS patients were randomized (1:1:1) to once daily oral fingolimod 0.5 mg, 1.25 mg or placebo. The key outcomes were the association between baseline RNFLT and baseline clinical characteristics and clinical/imaging outcomes up to 24 months. Change of RNFLT with fingolimod versus placebo within 24 months and time to retinal nerve fiber layer (RNFL) thinning were evaluated.

    RESULTS: Altogether 885 patients were included. At baseline, lower RNFLT was correlated with higher Expanded Disability Status Scale score (r = -1.085, p = 0.018), lower brain volume (r = 0.025, p = 0.006) and deep gray matter volume (r = 0.731, p 

    Matched MeSH terms: Tomography, Optical Coherence/methods
  11. Sun CZ, Sim SSKP, Vyas CH, Lott PW, Gunatheesan R, Teo KYC, et al.
    Eye (Lond), 2022 Jun;36(6):1143.
    PMID: 35046551 DOI: 10.1038/s41433-021-01859-6
    Matched MeSH terms: Tomography, Optical Coherence/methods
  12. Pee XK, Low A, Ab Kahar MEPI, Mohamed SO, Chong YJ
    BMC Ophthalmol, 2023 Nov 07;23(1):444.
    PMID: 37932684 DOI: 10.1186/s12886-023-03186-8
    BACKGROUND: To report a rare case of pulmonary and ocular complications with visual loss due to bilateral Purtscher-like retinopathy and paracentral acute middle maculopathy (PAMM) following a hyaluronic acid (HA) filler injection to the breast. Systemic and visual recovery was attained following corticosteroid therapy.

    CASE PRESENTATION: A 27-year-old lady presented with painless blurring of vision in both eyes for 2 weeks following hyaluronic acid breast filler injections by a non-medical practitioner. She was initially admitted to the medical ward for diffuse alveolar haemorrhage and altered sensorium. The presenting visual acuity was counting fingers in both eyes. Bilateral dilated fundus examination showed hyperaemic discs, concentric rim of retinal whitening around macula with patches of polygonal-shaped retinal whitening, generalised cotton-wool spots, tortuous veins, and flame-shaped haemorrhages. Spectral-domain optical coherence tomography (SD-OCT) macula revealed hyper-reflective bands at the inner nuclear layer (INL). Fluorescein angiography demonstrated hot discs, delayed arm-to-retina time, arterial filling, and arterio-venous transit time with staining of the vessels at the posterior pole. She was managed with a tapering dose of systemic corticosteroids. The visual acuity improved to 6/12 over 8 weeks with significant anatomical and functional improvement. Dilated fundus examination showed resolution of initial funduscopy findings. The hyper-reflective bands on the OCT had resolved with subsequent thinning of the INL and disorganisation of retinal inner layers.

    CONCLUSION: Filler injections are in increasing demand and are frequently being performed by non-medical practitioners. Visual loss from non-facial HA fillers is rare. Inadvertent entry of HA into a blood vessel may potentially cause systemic and sight-threatening ocular complications. Good anatomical knowledge and proper injection technique are vital in preventing this unfortunate sequela. There are limited reports on successful visual recovery following various treatment approaches and we hope this case provides valuable insights.

    Matched MeSH terms: Tomography, Optical Coherence/methods
  13. Chou HD, Teh WM, Wu WC, Hwang YS, Chen KJ, Lai CC
    Retina, 2023 Dec 01;43(12):2134-2138.
    PMID: 35512285 DOI: 10.1097/IAE.0000000000003516
    PURPOSE: To report the outcomes of the Peeling and Internal Limiting Membrane Reposition (PAIR) technique in myopic foveoschisis.

    METHODS: A retrospective case series of eyes with myopic foveoschisis that underwent vitrectomy and PAIR. Visual acuity, fundus photographs, and optical coherence tomography measurements were obtained and analyzed. Data are presented as medians (ranges).

    RESULTS: A total of seven eyes underwent PAIR and were followed up for 339 days (188-436 days). No intraoperative complications were noted. One eye exhibited postoperative macular hole formation, but the hole was healed through fluid-gas exchange. At the last follow-up, the visual acuity had improved from 20/66 (20/332-20/40) to 20/40 (20/100-20/25), and the central foveal thickness had decreased from 576 µ m to 269 µ m. A repositioned internal limiting membrane (ILM) was observed in six of the eyes, and inner retinal dimples were noted in only two eyes. However, retinal wrinkles under the repositioned or perifoveal ILM were noted in five eyes.

    CONCLUSION: The PAIR technique relieved traction, restored the ILM, and achieved functional and morphological improvement in eyes with myopic foveoschisis. Limited occurrence of inner retinal dimples and retinal thinning was noted, but retinal wrinkles occurred, likely due to ILM contracture.

    Matched MeSH terms: Tomography, Optical Coherence/methods
  14. Alsaih K, Lemaitre G, Rastgoo M, Massich J, Sidibé D, Meriaudeau F
    Biomed Eng Online, 2017 Jun 07;16(1):68.
    PMID: 28592309 DOI: 10.1186/s12938-017-0352-9
    BACKGROUND: Spectral domain optical coherence tomography (OCT) (SD-OCT) is most widely imaging equipment used in ophthalmology to detect diabetic macular edema (DME). Indeed, it offers an accurate visualization of the morphology of the retina as well as the retina layers.

    METHODS: The dataset used in this study has been acquired by the Singapore Eye Research Institute (SERI), using CIRRUS TM (Carl Zeiss Meditec, Inc., Dublin, CA, USA) SD-OCT device. The dataset consists of 32 OCT volumes (16 DME and 16 normal cases). Each volume contains 128 B-scans with resolution of 1024 px × 512 px, resulting in more than 3800 images being processed. All SD-OCT volumes are read and assessed by trained graders and identified as normal or DME cases based on evaluation of retinal thickening, hard exudates, intraretinal cystoid space formation, and subretinal fluid. Within the DME sub-set, a large number of lesions has been selected to create a rather complete and diverse DME dataset. This paper presents an automatic classification framework for SD-OCT volumes in order to identify DME versus normal volumes. In this regard, a generic pipeline including pre-processing, feature detection, feature representation, and classification was investigated. More precisely, extraction of histogram of oriented gradients and local binary pattern (LBP) features within a multiresolution approach is used as well as principal component analysis (PCA) and bag of words (BoW) representations.

    RESULTS AND CONCLUSION: Besides comparing individual and combined features, different representation approaches and different classifiers are evaluated. The best results are obtained for LBP[Formula: see text] vectors while represented and classified using PCA and a linear-support vector machine (SVM), leading to a sensitivity(SE) and specificity (SP) of 87.5 and 87.5%, respectively.

    Matched MeSH terms: Tomography, Optical Coherence*
  15. Yip VCH, Wong HT, Yong VKY, Lim BA, Hee OK, Cheng J, et al.
    J Glaucoma, 2019 07;28(7):e132-e133.
    PMID: 31135585 DOI: 10.1097/IJG.0000000000001289
    Matched MeSH terms: Tomography, Optical Coherence
  16. Obade AY, Pandarathodiyil AK, Oo AL, Warnakulasuriya S, Ramanathan A
    Clin Oral Investig, 2021 Sep;25(9):5411-5419.
    PMID: 33629155 DOI: 10.1007/s00784-021-03849-0
    OBJECTIVE: This study aims to examine the ability of optical coherence tomography (OCT) to differentiate ex vivo epithelial structure of benign disorders, dysplastic, and oral squamous cell carcinoma (OSCC) in comparison with the structure of normal marginal mucosa of oral biopsies. As a secondary objective, we examined the inter- and intra-observer variations of OCT measurements of two calibrated assessors.

    MATERIALS AND METHODS: Oral biopsies (n = 44) were scanned using the swept source OCT (SSOCT) and grouped by pathology diagnosis to benign, dysplasia or carcinoma. Two trained and calibrated assessors scored on the five OCT variables: thickness of keratin layer (KL), epithelial layer (EL), homogeneity of lamina propria (LP), basement membrane integrity (BMI), and the degree of reflection of the epithelial layer (Ep Re). Chi-square tests and Fischer's exact method were used to compare the data.

    RESULTS: The OCT images showed breached BM status in all the OSCC samples (100%). Epithelial reflection was noted to be hyper-reflective in all the OSCC and oral dysplasia samples (100%). An increase in KL in 66.67% of the OSCC and 100% of the oral dysplasia samples was found. EL was increased in all the OSCC samples (100%) and 85.72% of the oral dysplasias. Kappa values showed that there was very good agreement (over 0.7) when scoring individual parameters between the two assessors.

    CONCLUSION: The study showed that the BM status was a key parameter in the detection of SCC and for differentiating SCC from oral dysplasia or benign disorders.

    CLINICAL RELEVANCE: OCT is a non-invasive and non-radioactive adjunct diagnostic tool that can provide immediate results on the structure of oral mucosa. The BM status measured ex vivo was a key parameter in the detection of SCC and for differentiating SCC from oral dysplasia or benign disorders.

    Matched MeSH terms: Tomography, Optical Coherence
  17. Abdul Rahim, R., Pang, J.F., Chan, K.S., Leong, L.C., Fazalul Rahiman, M.H.
    ASM Science Journal, 2007;1(1):27-36.
    MyJurnal
    In this study, real-time imaging was monitored for flowing solid particles when various baffles were created to block certain areas of the pipe. The generated flow regimes were full-flow, three-quarter-flow, half-flow and quarter-flow. A vertical pneumatic conveyor was designed to hold a 85 mm inner diameter pipeline. The four projection optical tomography systems used, applied the parallel beam projection approach and use infrared light sources so that the sensor was free of noise from the surrounding visible light source. The two orthogonal and two rectilinear projections were axial, but ideally they should have been in the same layer. The sensor readings could be related to the varying light intensity effects of the dropping particles and were used to provide cross-sectional distribution information for the conveyor. By using computer programming, the information was reconstructed to produce coloured images and concentration was obtained by reference to a colour code. The results obtained from this study showed how imaged flow followed the artificial flow regime. This study could benefit industrial production lines in maintaining the desired flow rates.
    Matched MeSH terms: Tomography, Optical
  18. Tayyari F, Yusof F, Vymyslicky M, Tan O, Huang D, Flanagan JG, et al.
    Invest Ophthalmol Vis Sci, 2014 Dec;55(12):7716-25.
    PMID: 25335983 DOI: 10.1167/iovs.14-14430
    The purpose of this study was to determine the within-session variability and between-session repeatability of spectral Fourier-domain optical coherence tomography (Doppler FD-OCT) Doppler retinal blood flow measurements in young and elderly subjects.
    Matched MeSH terms: Tomography, Optical Coherence/methods*; Tomography, Optical Coherence/standards
  19. Gong P, Chin L, Es'haghian S, Liew YM, Wood FM, Sampson DD, et al.
    J Biomed Opt, 2014 Dec;19(12):126014.
    PMID: 25539060 DOI: 10.1117/1.JBO.19.12.126014
    We demonstrate the in vivo assessment of human scars by parametric imaging of birefringence using polarization-sensitive optical coherence tomography (PS-OCT). Such in vivo assessment is subject to artifacts in the detected birefringence caused by scattering from blood vessels. To reduce these artifacts, we preprocessed the PS-OCT data using a vascular masking technique. The birefringence of the remaining tissue regions was then automatically quantified. Results from the scars and contralateral or adjacent normal skin of 13 patients show a correspondence of birefringence with scar type: the ratio of birefringence of hypertrophic scars to corresponding normal skin is 2.2 ± 0.2 (mean ± standard deviation ), while the ratio of birefringence of normotrophic scars to normal skin is 1.1 ± 0.4 . This method represents a new clinically applicable means for objective, quantitative human scar assessment.
    Matched MeSH terms: Tomography, Optical Coherence/instrumentation; Tomography, Optical Coherence/methods*
  20. Idroas M, Rahim RA, Green RG, Ibrahim MN, Rahiman MH
    Sensors (Basel), 2010;10(10):9512-28.
    PMID: 22163423 DOI: 10.3390/s101009512
    This research investigates the use of charge coupled device (abbreviated as CCD) linear image sensors in an optical tomographic instrumentation system used for sizing particles. The measurement system, consisting of four CCD linear image sensors are configured around an octagonal shaped flow pipe for a four projections system is explained. The four linear image sensors provide 2,048 pixel imaging with a pixel size of 14 micron × 14 micron, hence constituting a high-resolution system. Image reconstruction for a four-projection optical tomography system is also discussed, where a simple optical model is used to relate attenuation due to variations in optical density, [R], within the measurement section. Expressed in matrix form this represents the forward problem in tomography [S] [R] = [M]. In practice, measurements [M] are used to estimate the optical density distribution by solving the inverse problem [R] = [S](-1)[M]. Direct inversion of the sensitivity matrix, [S], is not possible and two approximations are considered and compared-the transpose and the pseudo inverse sensitivity matrices.
    Matched MeSH terms: Tomography, Optical/instrumentation*; Tomography, Optical/methods*
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