Papers by Subhash Narayanan
Journal of Biomedical Optics, 2021
Significance: Screening and early detection of oral potentially malignant lesions (OPMLs) are of ... more Significance: Screening and early detection of oral potentially malignant lesions (OPMLs) are of great significance in reducing the mortality rates associated with head and neck malignancies. Intra-oral multispectral optical imaging of tissues in conjunction with cloud-based machine learning (CBML) can be used to detect oral precancers at the point-of-care (POC) and guide the clinician to the most malignant site for biopsy. Aim: Develop a bimodal multispectral imaging system (BMIS) combining tissue autofluorescence and diffuse reflectance (DR) for mapping changes in oxygenated hemoglobin (HbO 2) absorption in the oral mucosa, quantifying tissue abnormalities, and guiding biopsies. Approach: The hand-held widefield BMIS consisting of LEDs emitting at 405, 545, 575, and 610 nm, 5MPx monochrome camera, and proprietary Windows-based software was developed for image capture, processing, and analytics. The DR image ratio (R610/R545) was compared with pathologic classification to develop a CBML algorithm for real-time assessment of tissue status at the POC. Results: Sensitivity of 97.5% and specificity of 92.5% were achieved for discrimination of OPML from patient normal in 40 sites, whereas 82% sensitivity and 96.6% specificity were obtained for discrimination of abnormal (OPML + SCC) in 89 sites. Site-specific algorithms derived for buccal mucosa (27 sites) showed improved sensitivity and specificity of 96.3% for discrimination of OPML from normal. Conclusions: Assessment of oral cancer risk is possible by mapping of HbO 2 absorption in tissues, and the BMIS system developed appears to be suitable for biopsy guidance and early detection of oral cancers.
BMJ open, 2011
Strong proof-of-principle for utilisation of diffuse reflectance spectroscopy, a non-invasive too... more Strong proof-of-principle for utilisation of diffuse reflectance spectroscopy, a non-invasive tool for early detection of malignant changes, has emerged recently. The potential of this technique in distinguishing normal tissue from hyperplastic and dysplastic tissues was explored. Diffuse reflectance (DR) spectra in the 400-700 nm region were obtained from the buccal mucosa of 96 patients and 34 healthy volunteers. The DR spectral data were compared against the gold standard biopsy and histopathology results. A principal-component analysis was performed for dimensional reduction in the normalised spectral data with linear discriminant analysis as the classifying technique. The receiver operator characteristic curve technique was employed for evaluating the performance of the diagnostic test. DR spectral features for different lesions, such as normal/healthy, hyperplastic, dysplastic and squamous cell carcinoma (SCC), varied significantly according to the intensity of oxygenated haem...
Optical Biopsy X, 2012
Accurate diagnosis of premalignant or malignant oral lesions depends on the quality of the biopsy... more Accurate diagnosis of premalignant or malignant oral lesions depends on the quality of the biopsy, adequate clinical information and correct interpretation of the biopsy results. The major clinical challenge is to precisely locate the biopsy site in a clinically suspicious lesion. Dips due to oxygenated hemoglobin absorption have been noticed at 545 and 575 nm in the diffusely reflected white light spectra of oral mucosa and the intensity ratio R545/R575 has been found suited for early detection of oral pre-cancers. A multi-spectral diffuse reflectance (DR) imaging system has been developed consisting of an electron multiplying charge coupled device (EMCCD) camera and a liquid crystal tunable filter for guiding the clinician to an optimal biopsy site. Towards this DR images were recorded from 27 patients with potentially malignant lesions on their tongue (dorsal, lateral and ventral sides) and from 44 healthy controls at 545 and 575 nm with the DR imaging system. False colored ratio image R545/R575 of the lesion provides a visual discerning capability that helps in locating the most malignant site for biopsy. Histopathological report of guided biopsy showed that out of the 27 patients 16 were cancers, 9 pre-cancers and 2 lichen planus. In this clinical trial DR imaging has correctly guided 25 biopsy sites, yielding a sensitivity of 93% and a specificity of 98%, thereby establishing the potential of DR imaging as a tool for guided biopsy.
Biomedical Applications of Light Scattering VI, 2012
In clinical diagnostic procedures, gingival inflammation is considered as the initial stage of pe... more In clinical diagnostic procedures, gingival inflammation is considered as the initial stage of periodontal breakdown. This is often detected clinically by bleeding on probing as it is an objective measure of inflammation. Since conventional diagnostic procedures have several inherent drawbacks, development of novel non-invasive diagnostic techniques assumes significance. This clinical study was carried out in 15 healthy volunteers and 25 patients to demonstrate the applicability of diffuse reflectance (DR) spectroscopy for quantification and discrimination of various stages of inflammatory conditions in periodontal disease. The DR spectra of diseased lesions recorded using a point monitoring system consisting of a tungsten halogen lamp and a fiber-optic spectrometer showed oxygenated hemoglobin absorption dips at 545 and 575 nm. Mean DR spectra on normalization shows marked differences between healthy and different stages of gingival inflammation. Among the various DR intensity ratios investigated, involving oxy Hb absorption peaks, the R620/R575 ratio was found to be a good parameter of gingival inflammation. In order to screen the entire diseased area and its surroundings instantaneously, DR images were recorded with an EMCCD camera at 620 and 575 nm. We have observed that using the DR image intensity ratio R620/R575 mild inflammatory tissues could be discriminated from healthy with a sensitivity of 92% and specificity of 93%, and from moderate with a sensitivity of 83% and specificity of 96%. The sensitivity and specificity obtained between moderate and severe inflammation are 82% and 76% respectively.
Journal of Biomedical Optics, 2006
A low-cost, fast, and noninvasive method for early diagnosis of malignant lesions of oral mucosa ... more A low-cost, fast, and noninvasive method for early diagnosis of malignant lesions of oral mucosa based on diffuse reflectance spectral signatures is presented. In this technique, output of a tungsten halogen lamp is guided to the tissue through the central fiber of a reflection probe whose surrounding six fibers collects tissue reflectance. Ex vivo diffuse reflectance spectra in the 400 to 600-nm region is measured from surgically removed oral cavity lesions using a miniature fiber optic spectrometer connected to a computer. Reflectance spectral intensity is higher in malignant tissues and shows dips at 542 and 577 nm owing to absorption from oxygenated hemoglobin ͑HbO 2 ͒. Measurements carried out, within an hour of surgical excision, on malignant lesion and adjoining uninvolved mucosa show that these absorption features are more prominent in neoplastic tissues owing to increased microvasculature and blood content. It is observed that reflectance intensity ratio of hemoglobin bands, R540/R575, from malignant sites are always lower than that from normal sites and vary according to the histological grade of malignancy. The diffuse reflectance intensity ratio R540/R575 of the hemoglobin bands appears to be a useful tool to discriminate between malignant lesions and normal mucosa of the oral cavity in a clinical setting.
Journal of Biomedical Optics, 2012
This clinical study was to demonstrate the applicability of diffuse reflectance (DR) intensity ra... more This clinical study was to demonstrate the applicability of diffuse reflectance (DR) intensity ratio R620/ R575 in the quantification and discrimination of periodontitis and gingivitis from healthy gingiva. DR spectral measurements were carried out with white-light illumination from 70 healthy sites in 30 healthy volunteers, and 63 gingivitis-and 58 periodontitis-infected sites in 60 patients. Clinical parameters such as probing pocket depth, clinical attachment level, and gingival index were recorded in patient population. Diagnostic accuracies for discrimination of gingivitis and periodontitis from healthy gingiva were determined by comparison of spectral signatures with clinical parameters. Divergence of average DR spectral intensity ratio between control and test groups was studied using analysis of variance. The mean DR spectrum on normalization at 620 nm showed marked differences between healthy tissue, gingivitis, and periodontitis. Hemoglobin concentration and apparent SO 2 (oxygen saturation) were also calculated for healthy, gingivitis, and periodontitis sites. DR spectral intensities at 545 and 575 nm showed a decreasing trend with progression of disease. Among the various DR intensity ratios studied, the R620/R575 ratio provided a sensitivity of 90% and specificity of 94% for discrimination of healthy tissues from gingivitis and a sensitivity of 91% and specificity of 100% for discrimination of gingivitis from periodontitis. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).
Journal of Biomedical Optics, 2008
Functional Plant Biology, 2004
The effects of drought and petrol engine exhaust pollutants, such as SO2 and NO2 and suspended pa... more The effects of drought and petrol engine exhaust pollutants, such as SO2 and NO2 and suspended particulate matter (SPM), on the photosynthetic activity of colocasia [Colocasia esculenta (L.) Schott], kacholam (Kaempferia galanga L.) and tapioca (Manihot esculenta Crantz) plants were studied from in vivo laser-induced chlorophyll fluorescence (LICF) spectra. An open-top chamber (OTC) of 2.5 m diameter and 3 m height incorporating an air-filtering unit was developed for this study. Plants grown inside the OTC were exposed to exhaust emissions from a two-stroke Birla Yamaha genset for 10 d, while a control group was maintained outside. Gaseous pollutants and SPM present inside the OTC during the exposure period were measured with a high-volume air sampler. The steady-state LICF spectra of the control and treated plants were recorded in the 650–750-nm region. Fluorescence induction kinetics (Kautsky effect) was also recorded during the stress period from dark-adapted intact plant leaves...
Cancer, 2008
BACKGROUNDLaser‐induced autofluorescence (LIAF) is an emerging noninvasive technique in the biome... more BACKGROUNDLaser‐induced autofluorescence (LIAF) is an emerging noninvasive technique in the biomedical field, especially for cancer detection. The goal of the study was to develop a spectral ratio reference standard (SRRS) to discriminate different grades of oral cancer.METHODSLIAF emission spectra from oral mucosa were recorded in the 420–720 nm spectral range on a miniature fiberoptic spectrometer from 14 anatomical sites of 35 healthy volunteers and 91 sites of 44 patients, with excitation at 404 nm from a diode laser.RESULTSHistopathologic analysis of biopsy samples showed that oral mucosa of adjoining malignant sites in patients are not usually normal, but showed various degrees of epithelial dysplasia and hyperplasia. Therefore, instead of using LIAF data from apparently normal lesions of patients as control, spectral data values of the oral mucosa of healthy volunteers were used as control. The autofluorescence emission at 500 nm is characteristic of oral mucosa, whereas in m...
Journal of Biomedical Optics, 2010
We present the clinical applicability of fluorescence ratio reference standard ͑FRRS͒ to discrimi... more We present the clinical applicability of fluorescence ratio reference standard ͑FRRS͒ to discriminate different stages of dental caries. Toward this, laser-induced autofluorescence emission spectra are recorded in vivo in the 400-to 800-nm spectral range on a miniature fiber optic spectrometer from 65 patients, with a 404-nm diode laser as the excitation source. Autofluorescence spectra of sound teeth consist of a broad emission at 500 nm that is typical of natural enamel, whereas in caries teeth additional peaks are seen at 635 and 680 nm due to emission from porphyrin compounds in oral bacteria. Scatter plots are developed to differentiate sound teeth from enamel caries, sound teeth from dentinal caries, and enamel caries from dentinal caries using the mean fluorescence intensity ͑FI͒ and ratios F500/ F635 and F500/ F680 measured from 25 sites of sound teeth and 65 sites of carious teeth. The sensitivity and specificity of both the FI and FRRS are determined. It is observed that a diagnostic algorithm based on FRRS scatter plots is able to discriminate enamel caries from sound teeth, dentinal caries from sound teeth, and enamel from dentinal caries with overall sensitivities of 85, 100, and 88% and specificities of 90, 100, and 77%, respectively.
Antimicrobial photodynamic therapy (aPDT) is an evolving treatment modality where light of a part... more Antimicrobial photodynamic therapy (aPDT) is an evolving treatment modality where light of a particular wavelength is used to excite a specific photosensitizer (PS) that mediates bacterial destruction. Randomized controlled trial of aPDT in the management of chronic periodontitis shows the potential of this treatment in improving clinical, patient-based and microbial parameters in the test group as compared to control group and therefore can be proposed as an adjunct to conventional scaling and root planning in order to improve treatment results of chronic periodontitis. Furthermore, for the first time, laser induced autofluorescence spectra recorded in situ from dental plaque accumulated on tooth surface shows the applicability of this technique in discrimination between various grades of plaque clinically.
Biomolecules, Nov 24, 2017
The aim of this systematic review was to investigate whether antimicrobial photodynamic therapy (... more The aim of this systematic review was to investigate whether antimicrobial photodynamic therapy (aPDT) as either a primary mode of treatment or an adjunct to non-surgical treatment was more effective than scaling and root planing (SRP) alone in treating chronic periodontitis in terms of clinical attachment level (CAL) gain and probing depth (PD) reduction. The focused question was developed using the Patient, Intervention, Comparison, and Outcome (PICO) format, and two authors independently searched the Medline, EMBASE, Cochrane Library, Web of Science, Google Scholar, and Scopus databases for relevant studies from January 2008 to December 2016. Twenty studies included in this systematic review were randomized clinical trials (RCTs) or quasi-RCTs of aPDT compared to placebo, no intervention, or non-surgical treatment in an adult population. Basic study characteristics, photosensitizing agents and wavelengths used in aPDT, frequency of aPDT application, effect of aPDT on clinical par...
Journal of Biomedical Optics, 2015
The aim of this study was to evaluate the applicability of laser-induced autofluorescence (LIAF) ... more The aim of this study was to evaluate the applicability of laser-induced autofluorescence (LIAF) spectroscopy to detect and quantify dental plaque. LIAF spectra were recorded in situ from dental plaque (0-3 grades of plaque index) in 300 patients with 404 nm diode laser excitation. The fluorescence intensity ratio of the emission peaks was calculated from the LIAF spectral data following which their scatter plots were drawn and the area under the receiver operating characteristics were calculated. The LIAF spectrum of clinically invisible grade-1 plaque showed a prominent emission peak at 510 nm with a satellite peak around 630 nm in contrast to grade 0 that has a single peak around 500 nm. The fluorescence intensity ratio (F 510∕F 630) has a decreasing trend with increase in plaque grade and the ratio values show statistically significant differences (p < 0.01) between different grades. An overall sensitivity and specificity of 100% each was achieved for discrimination between grade-0 and grade-1 plaque. The clinical significance of this study is that the diagnostic algorithm developed based on fluorescence spectral intensity ratio (F 510∕F 630) would be useful to precisely identify minute amounts of plaque without the need for disclosing solutions and to convince patients of the need for proper oral hygiene and homecare practices.
Oral Oncology Supplement, 2007
was of 40 to 93 year-old with a median age of 67 years. Only 11 patients were smokers. Totally ou... more was of 40 to 93 year-old with a median age of 67 years. Only 11 patients were smokers. Totally our 48 patients developed 83 carcinomas; 35 patients (73%) were affected by chronic hepatitis related to HCV infection. Fifteen patients (31.25%) developed only one malignancy and 33 (68.75%) patients two or more primary tumours; the sites affected by the first malignancy were: the tongue in 11 cases (23%); the gingival in 12 (25%); the floor of the mouth in 7 (14.5%); the buccal mucosa in 13 (27%); the palate in 5 (10.5%). Thirty-three patients developed a second primary tumour after a median period after the detection of the first malignancy of 18 months; among these 9 patients (18.75%) developed more than two malignancies. Among all patients, only 4 died for reasons (8.3%) related to the disease; the remaining are still currently monitored every four months Despite several different therapeutic approaches PVL remains a refractory disease with an unknown aetiology that imposes prolonged and strict follow-up which should not exceed four months.
169 Abstract Early detection of cervical cancer is a growing concern worldwide. Current screening... more 169 Abstract Early detection of cervical cancer is a growing concern worldwide. Current screening techniques based on Pap smear and colposcopy burden the health care system with excessive costs, unnecessary anxiety, discomfort and the patient has to wait for a few days for biopsy results. This paper reports a non-invasive and real-time diagnostic tool based on diffuse reflectance (DR) imaging for screening of cervical cancers. The DR spectra of white light consist of dips at 545 and 575 nm due to oxygenated hemoglobin absorption and the previous studies on oral cancer patients using a multi-spectral DR imaging system has shown that reflectance image ratio R545/R575 could effectively discriminate healthy tissue from premalignant and malignant lesions. In the present study DR images were recorded from 41 patients and the image ratio R545/R575 was determined from the monochrome images recorded at 545 and 575 nm and the same was pseudo-color-mapped to examine variations in the ratio value across the lesion. The DR image ratio value from the biopsied site was compared with histopathology results and the specificity and sensitivity of the imaging technique was determined. It was observed that low-grade cervical intraepithelial neoplasia (low grade CIN) could be discriminated from normal tissues with a sensitivity of 87.5% and specificity of 78.3% whereas high-grade cervical intraepithelial neoplasia (high grade CIN) could be discriminated from normal with 100% sensitivity and specificity. In comparison, low-grade CIN was discriminated from high-grade CIN with a sensitivity of 88.9 % and specificity of 87.5%. The results of the study show the potential of DR image ratio in non-invasive and real-time screening cervical precancers and in the identification of the most malignant site in the cervix for biopsy.
ABSTRACT A simple circuit utilising a pressurised three-electrode spark gap as the switching elem... more ABSTRACT A simple circuit utilising a pressurised three-electrode spark gap as the switching element for driving the electro-optic Q-switch of a solid-state laser is described. Output pulses of 15 ns duration (FWHM) were generated when this circuit was employed in a KDP Q-switched Nd:glass laser.
Review of Scientific Instruments, 1980
ABSTRACT A simple circuit using NE555 Timers for controlling a low repetition rate (upto 10 pulse... more ABSTRACT A simple circuit using NE555 Timers for controlling a low repetition rate (upto 10 pulses/min.) Q-switched solid-state laser is described. This circuit produces two pulses, one for firing the flashlamp and the other for driving the electro-optic Q-switch, whose delay can be continuously varied up to 700 mus.
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Papers by Subhash Narayanan