Optical thickness measurement of occluded samples by lens-less Fourier transform digital holography, thermal loading, and machine learning.

Thickness measurements of objects, especially transparent and semi-transparent objects, are essential for their characterization and identification. However, in the case of occluded objects, the optical thickness determination becomes difficult, and an indirect way must be devised. Thermal loading of the objects changes their opto-thermal properties, which will be reflected as a change in their optical thickness. The key to quantifying such occluded objects lies in collecting these opto-thermal signatures. This could be achieved by imaging the changes occurring to a probe wavefront passing through the object while it is being thermally loaded. Digital holographic interferometry is an ideal tool for observing phase changes, as it can be used to compare wavefronts recorded at different instances of time. Lens-less Fourier transform digital holographic imaging provides the phase information from a single Fourier transform of the recorded hologram and can be used to quantify occluded phase objects. Here we describe a technique for the measurement of change in optical thickness of thermally loaded occluded phase samples using lens-less Fourier transform digital holography and machine learning. The advantage of the proposed technique is that it is a single shot, lens-less imaging modality for quasi-real-time quantification of phase samples behind thin occlusions.

Correlation of various dental parameters of mandibular first molar with age, body weight and breed in healthy dogs.

The aim of this study was to investigate the relationship of different radiographic parameters of mandibular first molar with respect to age, body weight and breed in healthy dogs. Overall, 50 dogs with the age from 5 to 156 months and body weight from 6.00 to 45.00 kg of various breeds were made the subject of study. Animals were categorized into different groups based on age, body weight and breed. A new dental parameters measurement technique was standardised which was in line with modified Lind's measurement technique of human dentistry. A significant decrease in least square count means of dental parameters was observed in age group 1 (0 - 12 months) in comparison with group 2 (13 - 60 months) and group 3 (> 60 months). A significant decrease in least square count means of dental parameters was observed in group A (0.00 - 10.00 kg) in comparison with group B (11.00 - 25.00 kg) and group C (> 25.00 kg). The root canal width showed a significant decrease with an increase in age; therefore, it was difficult to approach pulp cavity in older dogs. Small breeds showed decline in root length/crown height (R/C) ratio and mandible height/first mandibular molar height (MH/M1H) ratio in comparison with medium and large breeds because of which there were more chances of tooth loosening in smaller breeds. Regression equations formulated with respect to body weight and age can act as a ready reference to calculate values of different dental parameters at places where dental radiography is not available.

Thoracic and abdominal aortic alterations in dogs affected with systemic hypertension.

Aortic remodeling is the consequence of untreated systemic hypertension along with aortic dilatation as a marker for target organ damage in human literature. Therefore, the present study was planned to detect the changes in aorta at the level of aortic root via echocardiography, thoracic descending aorta via radiography and abdominal aorta via ultrasonography in healthy (n = 46), diseased normotensive (n = 20) and systemically hypertensive dogs (n = 60). The aortic root dimensions were measured at the level of aortic annulus, sinus of valsalva, sino-tubular junction and proximal ascending aorta via left ventricular outflow tract view of echocardiography. The thoracic descending aorta was subjectively assessed for any disparity in size and shape of aorta via lateral and dorso-ventral view of chest radiography. The abdominal aorta was assessed via left and right paralumbar window for calculating the aortic elasticity along with aortic and caudal venacaval dimensions to calculate the aortic-caval ratio. The aortic root measurements were dilated (p < 0.001) in systemically hypertensive dogs with a positive correlation (p < 0.001) with systolic blood pressure (BP). Thoracic descending aorta was also (p < 0.05) altered in the size and shape (undulation) of systemically hypertensive dogs. Abdominal aorta was markedly stiffened with reduced elasticity (p < 0.05) along with dilatation (p < 0.01) in hypertensive dogs. Also, there was a positive correlation (p < 0.001) of aortic diameters and aortic-caval ratio and negative correlation (p < 0.001) of aortic elasticity with systolic BP. Therefore, it was concluded that aorta could be considered as an important target organ damage of systemic hypertension in dogs.

LED based large field of view off-axis quantitative phase contrast microscopy by hologram multiplexing.

In this manuscript, we describe the development of a single shot, self-referencing wavefront division, multiplexing digital holographic microscope employing LED sources for large field of view quantitative phase imaging of biological samples. To address the difficulties arising while performing interferometry with low temporally coherent sources, an optical arrangement utilizing multiple Fresnel Biprisms is used for hologram multiplexing, enhancing the field of view and increasing the signal to noise ratio. Biprisms offers the ease of obtaining interference patterns by automatically matching the path length between the two off-axis beams. The use of low temporally coherent sources reduces the speckle noise and the cost, and the form factor of the setup. The developed technique was implemented using both visible and UV LEDs and tested on polystyrene microspheres and human erythrocytes.

Pharmacokinetic-Pharmacodynamic Study of Ampicillin-Cloxacillin Combination in Indian Thoroughbred Horses (Equus caballus) and Safety Evaluation of the Computed Dosage Regimen.

The pharmacokinetics of ampicillin-cloxacillin, given as single intravenously dose of 10 mg.kg-1 (5 mg.kg-1 of ampicillin plus 5 mg.kg-1 of cloxacillin) was examined in clinically presented Indian thoroughbred horses (n = 6) in order to design appropriate dosing strategies. Drug concentrations in plasma were determined by high performance liquid chromatography (HPLC) and pharmacokinetic parameters were derived by non-compartmental analysis using WinNonlin software. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of ampicillin-cloxacillin against quality control strains of Escherichia coli and Staphylococcus aureus, grown in Muller Hinton Broth, were determined by broth microdilution method. For ampicillin, area under plasma drug concentration time curve (AUC) was 15.2 ± 0.54 µg.h.ml-1, mean residence time (MRT) was 1.33 ± 0.06 h and clearance (Cl) was 0.33 ± 0.01 L.h-1.kg-1. For cloxacillin, AUC was 18.0 ± 0.9 µg.h.ml-1, MRT was 1.28 ± 0.02 h and Cl was 0.28 ± 0.01 L.h-1.kg-1. MIC of ampicillin-cloxacillin combination against E. coli and S. aureus was determined to be 0.4 µg.ml-1. PK-PD integration indicated that to maintain %T > MIC value 50% for bacteria with MIC ≤ 0.4 µg.ml-1, an appropriate intravenous dosage regimen of ampicillin-cloxacillin combination in horses would be 15 mg.kg-1 (i.e. 7.5 mg.kg-1 of ampicillin plus 7.5 mg.kg-1 of cloxacillin), to be repeated at 12 h intervals. Safety profile of the recommended regimen did not significantly alter any of the 16 biochemical or haematological parameters studied.

Roadmap on digital holography [Invited].

This Roadmap article on digital holography provides an overview of a vast array of research activities in the field of digital holography. The paper consists of a series of 25 sections from the prominent experts in digital holography presenting various aspects of the field on sensing, 3D imaging and displays, virtual and augmented reality, microscopy, cell identification, tomography, label-free live cell imaging, and other applications. Each section represents the vision of its author to describe the significant progress, potential impact, important developments, and challenging issues in the field of digital holography.

Successful surgical management of massive ovarian teratoma in a rhesus macaque (Macaca mulatta).

A 5 years-old Rhesus macaque was presented with abdominal enlargement. The clinical, radiographic and ultrasonographic findings suggested that a massive mass occupying the whole of the abdomen. The mass was surgically removed, and histopathology confirmed ovarian teratoma. The macaque recovered uneventfully; however, the management to avoid self-mutilation of skin sutures was challenging.

Angular spectrum matching for digital holographic microscopy under extremely low light conditions.

Digital holographic microscopy (DHM) is a future three-dimensional (3D) microscopy due to its high-resolution and high-precision 3D images. Thus, it is getting attention in bioinformatics, semiconductor defect detection, etc. However, some limitations still exist. Especially, high-speed holographic imaging requires high-power lasers, which are difficult to image on highly absorbent or light-sensitive samples. To overcome these issues, we propose a new, to the best of our knowledge, digital hologram recovery algorithm called angular spectrum matching (ASM), which achieves hologram imitation to recover holograms in digital holography at low light intensities. The hologram used for the background phase comparison is recorded without objects; thus, no power limitation is required. The ASM utilizes this background hologram to recover dark holograms. We present experimental results showing improved DHM numerical reconstructions and recovered holograms under extremely low light conditions.

Whole-body Vibration Exposure Experienced by Dumper Operators in Opencast Mining According to ISO 2631-1:1997 and ISO 2631-5:2004: A Case Study.

The study characterizes whole-body vibration exposure (WBV) experienced by dumper operators in opencast mining in India. OBJECTIVE: Comparison of WBV risk of dumper operators as per ISO 2631-1 and ISO 2631-5 standard which are based on dominant axis RMS acceleration and estimated static compression dose (Sed), respectively. METHOD: Field study was conducted for 26 dumper operators. Whole Body Vibration signals were recorded using the tri-axial seat pad accelerometer and WBV data logger. RESULTS: The results showed RMS in range 0.47-1.62 m/s2, total vibration dose value (VDVT) 6.91-21.03 m/s1.75, and Sed values 0.13-1.09 MPa for all 26 dumper operators. It was observed that 23% of dumper operators exposed to high health risk, 73% dumper operators exposed to moderate health risk, and minimal health risk was observed for only dumper operators as per ISO 2631-1:1997. While evaluation based on ISO 2631-5:2004 revealed, only one dumper with high health risk, 27% showed moderate health risk, however, 69% of dumper operators were exposed to minimal health risk. CONCLUSION: The predicted health risk according to the ISO 2631-1 is higher as compared to ISO 2631-5. ISO 2631-1 methodology has the upper hand during the prediction of WBV health risk as compared to ISO 2631-5. The result showed that ISO 2631-1 methodology was more appropriate than ISO 2631-5 for WBV health risk analysis of dumper operators in Indian mines.

Deep learning-based cell identification and disease diagnosis using spatio-temporal cellular dynamics in compact digital holographic microscopy.

We demonstrate a successful deep learning strategy for cell identification and disease diagnosis using spatio-temporal cell information recorded by a digital holographic microscopy system. Shearing digital holographic microscopy is employed using a low-cost, compact, field-portable and 3D-printed microscopy system to record video-rate data of live biological cells with nanometer sensitivity in terms of axial membrane fluctuations, then features are extracted from the reconstructed phase profiles of segmented cells at each time instance for classification. The time-varying data of each extracted feature is input into a recurrent bi-directional long short-term memory (Bi-LSTM) network which learns to classify cells based on their time-varying behavior. Our approach is presented for cell identification between the morphologically similar cases of cow and horse red blood cells. Furthermore, the proposed deep learning strategy is demonstrated as having improved performance over conventional machine learning approaches on a clinically relevant dataset of human red blood cells from healthy individuals and those with sickle cell disease. The results are presented at both the cell and patient levels. To the best of our knowledge, this is the first report of deep learning for spatio-temporal-based cell identification and disease detection using a digital holographic microscopy system.

Differential diagnosis and surgical management of cecal dilatation vis-a-vis cecal impaction in bovine.

AIM: The present study was undertaken to study the clinical and hemato-biochemical alterations, ultrasonography, and surgical treatment of bovine suffering from cecal dilatation and cecal impaction. MATERIALS AND METHODS: The present study was conducted on 11 bovines (9 buffaloes and 2 cattle) suffering from cecal dilatation (n=6) and cecal impaction (n=5). The diagnosis of surgical affections of cecum was made on the basis of clinical examination, hematobiochemistry, ultrasonography, and exploratory laparotomy. RESULTS: A marked decrease in serum total protein, albumin, chloride, potassium, and calcium levels while an increase in lactate concentrations was recorded. Peritoneal fluid examination revealed an increase in total protein concentration. Per rectal examination along with ultrasonography was used as a confirmatory diagnostic tool for cecal dilatation and cecal impaction. Ultrasonographic features of cecal dilatation and cecal impaction were recorded. Left flank laparorumenotomy was performed in six animals with dilated cecum along with colonic fecalith. Post-rumenotomy, these animals were treated with massage of cecum along with kneading of colonic fecalith. Right flank typhlotomy was done in the remaining five animals having impacted cecum for decompression of the dilated cecum. 9 of 11 animals survived which underwent surgery and remained healthy up to 3-month follow-up. CONCLUSION: Ultrasonography was reliable in the diagnosis of cecal dilatation and cecal impaction in bovine. Left flank exploration after laparorumenotomy is an ideal surgical technique for the management of cecal dilatation, while right flank typhlotomy is ideal for the management of cecal impaction in bovine.

Wavefront division digital holographic microscopy.

Digital holographic microscopy is the state of the art quantitative phase imaging of micro-objects including living cells. It is an ideal tool to image and quantify cell thickness profiles with nanometer thickness resolution. Digital holographic techniques usually are implemented using a two-beam setup that may be bulky and may not be field portable. Self-referencing techniques provide compact geometry but suffer from a reduction of the field of view. Here, we discuss the development of a wavefront division digital holographic microscope providing the full field of view with a compact system. The proposed approach uses a wavefront division module consisting of two lenses. The developed microscope is tested experimentally by measuring the physical and mechanical properties of red blood cells.

Sickle cell disease diagnosis based on spatio-temporal cell dynamics analysis using 3D printed shearing digital holographic microscopy.

We present a spatio-temporal analysis of cell membrane fluctuations to distinguish healthy patients from patients with sickle cell disease. A video hologram containing either healthy red blood cells (h-RBCs) or sickle cell disease red blood cells (SCD-RBCs) was recorded using a low-cost, compact, 3D printed shearing interferometer. Reconstructions were created for each hologram frame (time steps), forming a spatio-temporal data cube. Features were extracted by computing the standard deviations and the mean of the height fluctuations over time and for every location on the cell membrane, resulting in two-dimensional standard deviation and mean maps, followed by taking the standard deviations of these maps. The optical flow algorithm was used to estimate the apparent motion fields between subsequent frames (reconstructions). The standard deviation of the magnitude of the optical flow vectors across all frames was then computed. In addition, seven morphological cell (spatial) features based on optical path length were extracted from the cells to further improve the classification accuracy. A random forest classifier was trained to perform cell identification to distinguish between SCD-RBCs and h-RBCs. To the best of our knowledge, this is the first report of machine learning assisted cell identification and diagnosis of sickle cell disease based on cell membrane fluctuations and morphology using both spatio-temporal and spatial analysis.

Wide field of view common-path lateral-shearing digital holographic interference microscope.

Quantitative three-dimensional (3-D) imaging of living cells provides important information about the cell morphology and its time variation. Off-axis, digital holographic interference microscopy is an ideal tool for 3-D imaging, parameter extraction, and classification of living cells. Two-beam digital holographic microscopes, which are usually employed, provide high-quality 3-D images of micro-objects, albeit with lower temporal stability. Common-path digital holographic geometries, in which the reference beam is derived from the object beam, provide higher temporal stability along with high-quality 3-D images. Self-referencing geometry is the simplest of the common-path techniques, in which a portion of the object beam itself acts as the reference, leading to compact setups using fewer optical elements. However, it has reduced field of view, and the reference may contain object information. Here, we describe the development of a common-path digital holographic microscope, employing a shearing plate and converting one of the beams into a separate reference by employing a pin-hole. The setup is as compact as self-referencing geometry, while providing field of view as wide as that of a two-beam microscope. The microscope is tested by imaging and quantifying the morphology and dynamics of human erythrocytes.

Compact and field-portable 3D printed shearing digital holographic microscope for automated cell identification.

We propose a low-cost, compact, and field-portable 3D printed holographic microscope for automated cell identification based on a common path shearing interferometer setup. Once a hologram is captured from the portable setup, a 3D reconstructed height profile of the cell is created. We extract several morphological cell features from the reconstructed 3D height profiles, including mean physical cell thickness, coefficient of variation, optical volume (OV) of the cell, projected area of the cell (PA), ratio of PA to OV, cell thickness kurtosis, cell thickness skewness, and the dry mass of the cell for identification using the random forest (RF) classifier. The 3D printed prototype can serve as a low-cost alternative for the developing world, where access to laboratory facilities for disease diagnosis are limited. Additionally, a cell phone sensor is used to capture the digital holograms. This enables the user to send the acquired holograms over the internet to a computational device located remotely for cellular identification and classification (analysis). The 3D printed system presented in this paper can be used as a low-cost, stable, and field-portable digital holographic microscope as well as an automated cell identification system. To the best of our knowledge, this is the first research paper presenting automatic cell identification using a low-cost 3D printed digital holographic microscopy setup based on common path shearing interferometry.

Microsphere-assisted super-resolved Mirau digital holographic microscopy for cell identification.

In this paper, we use a glass microsphere incorporated into a digital holographic microscope to increase the effective resolution of the system, aiming at precise cell identification. A Mirau interferometric objective is employed in the experiments, which can be used for a common-path digital holographic microscopy (DHMicroscopy) arrangement. High-magnification Mirau objectives are expensive and suffer from low working distances, yet the commonly used low-magnification Mirau objectives do not have high lateral resolutions. We show that by placing a glass microsphere within the working distance of a low-magnification Mirau objective, its effective numerical aperture can be increased, leading to super-resolved three-dimensional images. The improvement in the lateral resolution depends on the size and vertical position of microsphere, and by varying these parameters, the lateral resolution and magnification may be adjusted. We used the information from the super-resolution DHMicroscopy to identify thalassemia minor red blood cells (tRBCs). Identification is done by comparing the volumetric measurements with those of healthy RBCs. Our results show that microsphere-assisted super-resolved Mirau DHMicroscopy, being common path and off-axis in nature, has the potential to serve as a benchtop device for cell identification and biomedical measurements.

Noncontact speckle-based optical sensor for detection of glucose concentration using magneto-optic effect.

We experimentally verify a speckle-based technique for noncontact measurement of glucose concentration in the bloodstream. The final device is intended to be a single wristwatch-style device containing a laser, a camera, and an alternating current (ac) electromagnet generated by a solenoid. The experiments presented are performed in vitro as proof of the concept. When a glucose substance is inserted into a solenoid generating an ac magnetic field, it exhibits Faraday rotation, which affects the temporal changes of the secondary speckle pattern distributions. The temporal frequency resulting from the ac magnetic field was found to have a lock-in amplification role, which increased the observability of the relatively small magneto-optic effect. Experimental results to support the proposed concept are presented.

Highly stable digital holographic microscope using Sagnac interferometer.

Interferometric microscopy has grown into a very potent tool for quantitative phase imaging of biological samples. Among the interfermetric methods, microscopy by digital holography is one of the most effective techniques, especially for studying dynamics of cells. Imaging of cell fluctuations requires digital holographic setups with high temporal stability. Common path setups in which the object and the reference beams encounter the same set of optical elements provide better temporal stability compared to two-beam setups. Here, we present a compact, easy-to-implement, common path digital holographic microscope based on Sagnac interferometer geometry. The microscope is implemented using a diode laser module employing a CCD array or a webcam sensor to record holograms. The system was tested for three-dimensional imaging capability, numerical focusing ability, and temporal stability. Sub-nanometer temporal stability without external vibration isolation components was obtained in both cases. The higher temporal stability makes the microscope compatible to image cell fluctuations, which is demonstrated by imaging the oscillation of the cell membrane of human red blood cells.

Digital holographic microscopy with coupled optical fiber trap for cell measurement and manipulation.

We present an integrated optical system for three-dimensional (3D) imaging of micrometer-sized samples, while immobilizing and manipulating the samples by means of an optical fiber trap. Optical traps allow us to apply and measure pico-Newton-sized forces, and perform detailed measurements of micrometer-sized dielectric systems in the field of biology. The integrated 3D system can be used as a major tool in the field of biophysics. The trap is built using a tapered optical fiber to enhance the effective numerical aperture of the fiber. The trapping system is mounted on a conventional microscope, in which the two eyepieces' output ports are used as the paths of an off-axis self-referencing digital holographic microscopy (DHM) setup. The trap is calibrated using a high-speed camera, and trap stiffness is determined through the power spectrum method. The compact setup provides an elegant apparatus for temporally stable DHM for 3D imaging of optically controlled samples. Three-dimensional information and quantitative phase contrast images of the trapped samples are obtained by postprocessing the recorded digital holograms. Experiments were performed on lipids and red blood cells. Quantitative phase contrast images and temporal evolution of optical thickness of trapped samples are presented.