Improve Image Contrast Research Articles

Initial results and designs of dual-filter and plenoptic imaging for high-temperature plasmas.

Mass injection has found new applications in magnetic fusion including edge-localized-mode control. Better understanding of injected-mass-plasma interactions requires spatially and temporally resolved diagnostics that can characterize the dynamics of the mass interactions with plasmas. Fast imaging can be used to characterize the ionization dynamics such as the propagation of the ionization front, which moves at the thermal sound or higher speed, and mixing of the neutral atoms with the ambient plasma. Multi-wavelength spectral imaging is promising since different parts of the plasma give different spectral signatures. Here we describe a dual-spectral imaging technique based on a monochromatic camera sensor and filters with two passing optical wavelengths. The method is shown to improve image contrast, and it compares favorably with alternatives such as color cameras and methods using a filter wheel. Further improvements through relative filter area ratios and plenoptic imaging are possible. The initial results from EAST and plenoptic imaging are also included.

PERBAIKAN CITRA INFRA MERAH DENGAN METODE CELLULAR AUTOMATA

Image enhancement is needed because not all images have good quality, such as noise, too low contrast or blurry image. These problems are commonly found in images generated from infrared cameras, therefore this study uses infrared imagery as an image to be corrected. The method that will be used to improve the image, namely Cellular Automata method. The edge detection using the Prewitt operator will be used as the initial state of Cellular Automata cells. The results obtained from this research is Cellular Automata method can improve the quality of infrared image well. Visually, the Cellular Automata method successfully improves image contrast and retains the infrared image detail so as not to reduce the value of information from the image. Calculated using the Linear Index of Fuzziness, the results of the Cellular Automata method are better only on some imagery only when compared to the Histogram Equalization mode.
 Keywords: Infrared Image, Image Enhancement, Cellular Automata

The configuration of DMD and the maximum intensity projection method for improving contrast in DMD-based confocal microscope.

In this article, an operation strategy of digital micromirror device (DMD) and the maximum intensity projection (MIP) image processing method are proposed to improve the contrast of images in confocal microscopy. First, the configuration of DMD is demonstrated and the effect of scanning unit size on image performance is analyzed. Then, the image processing method MIP is applied. According to the MIP method, only the maximum intensity projection point of the same pixel is chosen from every image, and the maximum intensity projection point exactly corresponds to the positon where mirror is at "on" position during the scanning process in DMD-based confocal microscope system,. Thus, high contrast of images can be achieved by using MIP. Finally, experiments are conducted to verify imaging performance by changing the parameter of scanning unit size and applying a MIP image processing technique. The results show that DMD scanning unit size and MIP image processing techniques play important roles in improving image contrast. Smaller scanning unit size of DMD improves axial contrast but greatly decreases the signal to noise ratio, which thus leads to reduced image contrast. Larger scanning unit size produces a better signal to noise ratio, thus better image contrast. However, a large S will sacrifice the processing time. Therefore, DMD scanning unit size should be smaller on the premise that image contrast can be satisfied. RESEARCH HIGHLIGHTS: Effect of DMD scanning unit size setting on image contrast is analyzed and verified. The maximum intensity projection (MIP) is investigated to improve the image contrast. Experiments are conducted to verify the enhancement of the image contrast.

Integrating fluorescence computed tomography with optical sheet illumination for imaging of live single cells.

We present a new approach for three-dimensional (3D) live single-cell imaging with isotropic sub-micron spatial resolution using fluorescence computed tomography (fCT). A thin, highly inclined and laminated optical (HILO) sheet of light is used for fluorescence excitation in live single cells that are rotated around an axis perpendicular to the optical axis. During a full rotation, 400-500 two-dimensional (2D) projection images of the cell are acquired from multiple viewing perspectives by rapidly scanning the HILO light sheet along the optical axis. We report technical characteristics of the HILO approach and the results of a quantitative comparison with conventional epi fCT, demonstrating that HILO fCT offers significantly (about 17 times) reduced photobleaching and a two-fold improvement in 3D imaging contrast. We discuss potential application areas of the method for cell structure studies in live single cells with isotropic 3D spatial resolution.

Whole-Brain Vasculature Reconstruction at the Single Capillary Level

The distinct organization of the brain’s vascular network ensures that it is adequately supplied with oxygen and nutrients. However, despite this fundamental role, a detailed reconstruction of the brain-wide vasculature at the capillary level remains elusive, due to insufficient image quality using the best available techniques. Here, we demonstrate a novel approach that improves vascular demarcation by combining CLARITY with a vascular staining approach that can fill the entire blood vessel lumen and imaging with light-sheet fluorescence microscopy. This method significantly improves image contrast, particularly in depth, thereby allowing reliable application of automatic segmentation algorithms, which play an increasingly important role in high-throughput imaging of the terabyte-sized datasets now routinely produced. Furthermore, our novel method is compatible with endogenous fluorescence, thus allowing simultaneous investigations of vasculature and genetically targeted neurons. We believe our new method will be valuable for future brain-wide investigations of the capillary network.

Miniature scanning light-sheet illumination implemented in a conventional microscope.

Living cells are highly dynamic systems responding to a large variety of biochemical and mechanical stimuli over minutes, which are well controlled by e.g. optical tweezers. However, live cell investigation through fluorescence microscopy is usually limited not only by the spatial and temporal imaging resolution but also by fluorophore bleaching. Therefore, we designed a miniature light-sheet illumination system that is implemented in a conventional inverted microscope equipped with optical tweezers and interferometric tracking to capture 3D images of living macrophages at reduced bleaching. The horizontal light-sheet is generated with a 0.12 mm small cantilevered mirror placed at 45° to the detection axis. The objective launched illumination beam is reflected by the micro-mirror and illuminates the sample perpendicular to the detection axis. Lateral and axial scanning of both Gaussian and Bessel beams, together with an electrically tunable lens for fast focusing, enables rapid 3D image capture without moving the sample or the objective lens. Using scanned Bessel beams and line-confocal detection, an average axial resolution of 0.8 µm together with a 10-15 fold improved image contrast is achieved.

Electron ptychography of 2D materials to deep sub-ångström resolution.

Aberration-corrected optics have made electron microscopy at atomic resolution a widespread and often essential tool for characterizing nanoscale structures. Image resolution has traditionally been improved by increasing the numerical aperture of the lens (α) and the beam energy, with the state-of-the-art at 300 kiloelectronvolts just entering the deep sub-ångström (that is, less than 0.5 ångström) regime. Two-dimensional (2D) materials are imaged at lower beam energies to avoid displacement damage from large momenta transfers, limiting spatial resolution to about 1 ångström. Here, by combining an electron microscope pixel-array detector with the dynamic range necessary to record the complete distribution of transmitted electrons and full-field ptychography to recover phase information from the full phase space, we increase the spatial resolution well beyond the traditional numerical-aperture-limited resolution. At a beam energy of 80 kiloelectronvolts, our ptychographic reconstruction improves the image contrast of single-atom defects in MoS2 substantially, reaching an information limit close to 5α, which corresponds to an Abbe diffraction-limited resolution of 0.39 ångström, at the electron dose and imaging conditions for which conventional imaging methods reach only 0.98 ångström.

Quantification of bone microstructure in the wrist using cone-beam computed tomography.

Due to the rising life expectancy, bone diseases (e.g. osteoporosis, osteoarthritis) and trauma (e.g. fracture) have become an important socio-economic burden. Accurate visualization and quantification of the bone microstructure in vivo is seen as an important step to enhance diagnosis and treatment. Micro-computed tomography (microCT) has become the gold standard in three-dimensional (3D) imaging of trabecular bone structure. Yet, usage is limited to ex vivo analyses, hence, it cannot be used to evaluate bone and bone adaptive responses in a patient. High-resolution peripheral computed tomography (HR-pQCT) is considered the best technique to measure the bone microarchitecture in vivo. By design HR-pQCT is limited to scanning extremities, such as the distal radius and distal tibia with a limited field of view and long scanning time (~2 à 3 min. for a stack of 0.9 cm). Cone-beam computed tomography (CBCT) is a promising alternative with a much larger field of view. Yet, CBCT is challenged by artefacts that reduce image contrast, such that it is currently being used for qualitative evaluation only. Therefore, the aims of this work were first to enhance image contrast and second to determine the accuracy of high-resolution CBCT for bone microarchitectural assessment. Trapezia of nineteen female arthritic patients were scanned twice ex vivo; once using CBCT (NewTom 5G, Cefla, Verona, Italy) at a nominal voxel size of 75 μm and once using microCT (SkyScan 1172, Bruker, Kontich, Belgium) at a voxel size of 19.84 μm. The CBCT-scans were reconstructed following 2 protocols: (1) using the commercial software delivered with the scanner and (2) using in-house developed software. After reconstruction and image processing, the images were segmented using adaptive thresholding. Bone morphometric parameters including bone volume (BV), total tissue volume (TV), bone volume fraction (BV/TV), bone surface density (BS/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp) and trabecular number (Tb.N) were calculated. Statistical evaluations were made at a significance level of 5%. Significant correlations were found between the CBCT-based bone parameters and the microCT-based parameters with R2 > 0.68 The in-house reconstructed software outperformed the commercial software. Smaller bias (overestimation of Tb.Th decreased from 114.24% to 59.96%) as well as higher correlations were observed for the in-house processed images. Still, a significant overestimation was observed for BV/TV and Tb. Th and an underestimation for Tb.N. We conclude that our CBCT image reconstruction improved image contrast which allowed for an accurate quantification of trabecular bone microarchitecture.

Lightness-aware contrast enhancement for images with different illumination conditions

It has become more convenient to take photographs in our daily life. However, without sufficient skills, we often produce poor photographs with low contrast and unclear details under various imperfect illumination conditions. Although plenty of image enhancing models have been developed, most of them impose a uniform enhancing strength to the whole image region, and thus tend to generate over-enhancement effects for regions with originally-satisfying illumination. To address this issue, we propose a novel contrast enhancing model, which is a simple linear fusion process based on an original image and its initial enhancement. As the key of our model, we construct a lightness map that estimates the scene lightness, which is aware of the image structure at pixel-wise level. In the fusion process, this map dynamically weighs between the initially enhanced image and the original image, and thus ensures a seamless fusion result. In our experiments, we validate our model on images with various illumination conditions, such as strong back light, imbalanced light, and low light. The results empirically show that our model performs well on simultaneously improving image contrast and keeping its naturalness.

Investigation of native cells in liquid using the high aspect ratio nanowhisker probes by means of atomic force microscopy

Specialized Pt/C single nanowhisker probes for atomic force microscopy have been used to study the native cellular bio-objects (fibroblasts) in PBS liquid. Optimal parameters of nanowhisker fabrication were found such as accelerating voltage 5 kV, exposure time 5-10 sec, aperture of electron microscope 20 μm. The preliminary results of our study showed an improvement of image contrast and adhesion forces when using nanowhisker probes compared to the standard Si probes.

Performance Evaluation of Adaptive Imaging Based on Multiphase Apodization with Cross-correlation: A Pilot Study in Abdominal Ultrasound.

Degradation of image contrast caused by phase aberration, off-axis clutter, and reverberation clutter remains one of the most important problems in abdominal ultrasound imaging. Multiphase apodization with cross-correlation (MPAX) is a novel beamforming technique that enhances ultrasound image contrast by adaptively suppressing unwanted acoustic clutter. MPAX employs multiple pairs of complementary sinusoidal phase apodizations to intentionally introduce grating lobes that can be used to derive a weighting matrix, which mostly preserves the on-axis signals from tissue but reduces acoustic clutter contributions when multiplied with the beamformed radio-frequency (RF) signals. In this paper, in vivo performance of the MPAX technique was evaluated in abdominal ultrasound using data sets obtained from 10 human subjects referred for abdominal ultrasound at the USC Keck School of Medicine. Improvement in image contrast was quantified, first, by the contrast-to-noise ratio (CNR) and, second, by the rating of two experienced radiologists. The MPAX technique was evaluated for longitudinal and transverse views of the abdominal aorta, the inferior vena cava, the gallbladder, and the portal vein. Our in vivo results and analyses demonstrate the feasibility of the MPAX technique in enhancing image contrast in abdominal ultrasound and show potential for creating high contrast ultrasound images with improved target detectability and diagnostic confidence.

Endoscopic near-infrared dental imaging with indocyanine green: a pilot study.

Current dental diagnosis, especially tooth abnormalities, relies largely on X-ray-based imaging, a technique that requires specialized skills and suffers from ionizing radiation. Here, we present a pilot study in rats of an efficient, ionizing-radiation-free and easy-to-use alternative for dental imaging. Postnatal rats at different ages were injected with indocyanine green and molars were imaged by a laboratory-designed endoscopic near-infrared (NIR) dental imaging system. The results indicate that the endoscopic NIR dental imaging can be used to observe the morphology of postnatal rat molars, especially at early postnatal stages when morphology of the molar is indistinguishable under visible conditions. A small abnormal cusp was observed and distinguished from the normal cusps by the NIR dental imaging system. Dental structures, such as unerupted molars, can be imaged as soon as 10 min after the injection of indocyanine green; imaging after 24 h shows improved imaging contrast. Overall, the endoscopic NIR fluorescence dental imaging system described here may be useful in dental research; this technique may serve as a safe, real-time imaging tool for dental diagnosis and treatment beyond experimental systems in the future.

Urokinase injection-triggered clearance enhancement of a 4-arm PEG-conjugated 64Cu-bombesin analog tetramer: A novel approach for the improvement of PET imaging contrast

Radiolabeled antibodies, polyethylene glycol-conjugated (PEGylated) peptides, liposomes, and other materials were investigated as positron-emission tomography (PET) probes. These substances accumulate in tumors but often remain too long in circulation. We investigated the combination of intravenous urokinase injection and its substrate linker as a triggered radioisotope clearance enhancement system to improve imaging contrast. To this end, we synthesized a four-arm PEGylated 64Cu-bombesin analog tetramer with a urokinase substrate linker. In mouse blood, it was almost perfectly cleaved and degraded into smaller radioactive fragments in vitro with urokinase (≥20,000 IU/mL). In mouse blood circulation, ∼50–65% of the probe was rapidly degraded after the urokinase injection and the radioactive fragments were eliminated mainly from the kidney. In contrast, tumor radioactivity levels did not change, and therefore, the tumors were clearly visualized. The tumor/blood ratio, an indicator of imaging contrast, increased 2.5 times, while elimination of the radioisotope from the blood was enhanced. This approach has the potential to improve imaging contrast using various PET probes. It could also shorten the time required to obtain sufficient contrast and decrease patient radiation exposure.

Molecular design of radiocopper-labelled Affibody molecules

The use of long-lived positron emitters 64Cu or 61Cu for labelling of Affibody molecules may improve breast cancer patients’ stratification for HER-targeted therapy. Previous animal studies have shown that the use of triaza chelators for 64Cu labelling of synthetic Affibody molecules is suboptimal. In this study, we tested a hypothesis that the use of cross-bridged chelator, CB-TE2A, in combination with Gly-Glu-Glu-Glu spacer for labelling of Affibody molecules with radiocopper would improve imaging contrast. CB-TE2A was coupled to the N-terminus of synthetic Affibody molecules extended either with a glycine (designation CB-TE2A-G-ZHER2:342) or Gly-Glu-Glu-Glu spacer (CB-TE2A-GEEE-ZHER2:342). Biodistribution and targeting properties of 64Cu-CB-TE2A-G-ZHER2:342 and 64Cu-CB-TE2A-GEEE-ZHER2:342 were compared in tumor-bearing mice with the properties of 64Cu-NODAGA-ZHER2:S1, which had the best targeting properties in the previous study. 64Cu-CB-TE2A-GEEE-ZHER2:342 provided appreciably lower uptake in normal tissues and higher tumor-to-organ ratios than 64Cu-CB-TE2A-G-ZHER2:342 and 64Cu-NODAGA-ZHER2:S1. The most pronounced was a several-fold difference in the hepatic uptake. At the optimal time point, 6 h after injection, the tumor uptake of 64Cu-CB-TE2A-GEEE-ZHER2:342 was 16 ± 6%ID/g and tumor-to-blood ratio was 181 ± 52. In conclusion, a combination of the cross-bridged CB-TE2A chelator and Gly-Glu-Glu-Glu spacer is preferable for radiocopper labelling of Affibody molecules and, possibly, other scaffold proteins having high renal re-absorption.

Design of a sustainable prepolarizing magnetic resonance imaging system for infant hydrocephalus.

The need for affordable and appropriate medical technologies for developing countries continues to rise as challenges such as inadequate energy supply, limited technical expertise, and poor infrastructure persist. Low-field magnetic resonance imaging (LF MRI) is a technology that can be tailored to meet specific imaging needs within such countries. Its low power requirements and the possibility of operating in minimally shielded or unshielded environments make it especially attractive. Although the technology has been widely demonstrated over several decades, it is yet to be shown that it can be diagnostic and improve patient outcomes in clinical applications. We here demonstrate the robustness of prepolarizing MRI (PMRI) technology for assembly and deployment in developing countries for the specific application to infant hydrocephalus. Hydrocephalus treatment planning and management requires only modest spatial resolution, such that the brain can be distinguished from fluid-tissue contrast detail within the brain parenchyma is not essential. We constructed an internally shielded PMRI system based on the Lee-Whiting coil system with a 22-cm diameter of spherical volume. In an unshielded room, projection phantom images were acquired at 113kHz with in-plane resolution of 3mm × 3mm, by introducing gradient fields of sufficient magnitude to dominate the 5000 ppm inhomogeneity of the readout field. The low cost, straightforward assembly, deployment potential, and maintenance requirements demonstrate the suitability of our PMRI system for developing countries. Further improvement in image spatial resolution and contrast of LF MRI will broaden its potential clinical utility beyond hydrocephalus.

An Adaptive Synthetic Aperture Method Applied to Ultrasound Tissue Harmonic Imaging.

In recent years, the minimum variance (MV) beamformer has been highly regarded since it provides high resolution and contrast in B-mode ultrasound imaging compared with nonadaptive delay-and-sum (DAS) beamformer. However, the performance of MV beamformer is degraded in the presence of the noise due to inaccurate estimation of the covariance matrix resulting in low-quality images. The conventional tissue harmonic imaging (THI) offers multiple advantages over conventional pulse-echo ultrasound imaging, including enhanced contrast resolution and improved axial and lateral resolutions, but low signal-to-noise ratio (SNR) is a major problem facing this imaging method, which uses a fixed transmit focus and dynamic receive focusing (DRF). In this paper, a synthetic aperture method based on the virtual source, namely, bidirectional pixel-based focusing (BiPBF), has been combined with the MV beamformer and then applied to second-harmonic ultrasound imaging. The main objective is suppressing the noise level to enhance the performance of the MV beamformer in the harmonic imaging, especially in lower and deeper depths where the SNR is low. In addition, combining the BiPBF and MV weighting results in simultaneous improvement in imaging resolution and contrast, in comparison with the conventional methods: DRF (DAS), BiPBF (DAS), and DRF (MV). The performance of the proposed method is evaluated on simulated and experimental RF data. The THI is achieved using the pulse-inversion technique. The results of the simulated wire phantom demonstrate that the proposed beamformer can achieve the best lateral resolution, along different depths, compared with DRF (DAS), BiPBF (DAS), and DRF (MV) methods. The results of the simulated and experimental cyst phantoms show that the new beamformer improves the contrast ratio (CR) and contrast-to-noise ratio (CNR) of the resulting images. In results of simulated cyst phantom, in average, the new beamformer improves the CR and CNR of the cyst about (7.4 dB, 49%), (3.2 dB, 16%), and (5 dB, 26%) compared with DRF (DAS), BiPBF (DAS), and DRF (MV), respectively. In results of experimental cyst phantom, these relative improvements are about (4.2 dB, 22%), (1.7 dB, 7%), and (2.6 dB, 15%). In addition, BiPBF (MV) method offers improved edge definition of cysts in comparison with the other methods.

Active pulse television measuring systems for ensuring navigation of transport means in heavy weather conditions

This paper presents research results of the Active Vision Area, formed by the Active Pulse Television Measuring System in conditions of decreased transparency of propagation medium.
 Aim: To increase backscatter interference suppression efficiency by the Active Pulse Television Measuring System for ensuring navigation of transport means in heavy weather conditions.
 Methods: Simulation of Active Vision Area considering light energy attenuation is proportionate to the square of distance and attenuation caused by propagation atmosphere. Performance of experimental researches with the Prototype of Active Pulse Television Measuring System using Big Aerosol Chamber, simulating dense fog and smoke conditions.
 Results: The designed model of Active Vision Area allowed estimating the changes of light energy distribution in the observed space layer depending on range of observation and transparency of radiation propagation medium. With equal duration values of the illumination and strobing pulses of the photodetector in conditions of dense fog, significantly big residual backscatter interference was revealed, maximum intensity area of the radiation reflected from objects was displaced from a distance of strobing delay. Illumination pulse duration reduction led to increase of backscatter interference suppression efficiency, improvement of image contrast and increase of accuracy of determination of distance to the observed objects.
 Conclusion: The increase of backscatter interference suppression efficiency by the Active Pulse Television Measuring System for ensuring navigation of transport means in heavy weather conditions is a relevant task

Synthesis and Evaluation of a Novel 64Cu- and 67Ga-Labeled Neurokinin 1 Receptor Antagonist for in Vivo Targeting of NK1R-Positive Tumor Xenografts.

Neurokinin 1 receptor (NK1R) is expressed in gliomas and neuroendocrine malignancies and represents a promising target for molecular imaging and targeted radionuclide therapy. The goal of this study was to synthesize and evaluate a novel NK1R ligand (NK1R-NOTA) for targeting NK1R-expressing tumors. Using a carboxymethyl moiety linked to L-733060 as a starting reagent, NK1R-NOTA was synthesized in a three-step reaction and then labeled with 64Cu (or 67Ga for in vitro studies) in the presence of CH3COONH4 buffer. The radioligand affinity and cellular uptake were evaluated with NK1R-transduced HEK293 cells (HEK293-NK1R) and NK1R nontransduced HEK293 cells (HEK293-WT) and their xenografts. Radiolabeled NK1R-NOTA was obtained with a radiochemical purity of >95% and specific activities of >7.0 GBq/μmol for 64Cu and >5.0 GBq/μmol for 67Ga. Both 64Cu- and 67Ga-labeled NK1R-NOTA demonstrated high levels of uptake in HEK293-NK1R cells, whereas co-incubation with an excess of NK1R ligand L-733060 reduced the level of uptake by 90%. Positron emission tomography (PET) imaging showed that [64Cu]NK1R-NOTA had a accumulated rapidly in HEK293-NK1R xenografts and a 10-fold lower level of uptake in HEK293-WT xenografts. Radioactivity was cleared by gastrointestinal tract and urinary systems. Biodistribution studies confirmed that the tumor-to-organ ratios were ≥5 for all studied organs at 1 h p.i., except kidneys, liver, and intestine, and that the tumor-to-intestine and tumor-to-kidney ratios were also improved 4 and 20 h post-injection. [64Cu]NK1R-NOTA is a promising ligand for PET imaging of NK1R-expressing tumor xenografts. Delayed imaging with [64Cu]NK1R-NOTA improves image contrast because of the continuous clearance of radioactivity from normal organs.

An integrated strategy for improving contrast, durability, and portability of a Pocket Colposcope for cervical cancer screening and diagnosis.

IntroductionWe have previously developed a portable Pocket Colposcope for cervical cancer screening in resource-limited settings. In this manuscript we report two different strategies (cross-polarization and an integrated reflector) to improve image contrast levels achieved with the Pocket Colposcope and evaluate the merits of each strategy compared to a standard-of-care digital colposcope. The desired outcomes included reduced specular reflection (glare), increased illumination beam pattern uniformity, and reduced electrical power budget. In addition, anti-fogging and waterproofing features were incorporated to prevent the Pocket Colposcope from fogging in the vaginal canal and to enable rapid disinfection by submersion in chemical agents.MethodsCross-polarization (Generation 3 Pocket Colposcope) and a new reflector design (Generation 4 Pocket Colposcope) were used to reduce glare and improve contrast. The reflector design (including the angle and height of the reflector sidewalls) was optimized through ray-tracing simulations. Both systems were characterized with a series of bench tests to assess specular reflection, beam pattern uniformity, and image contrast. A pilot clinical study was conducted to compare the Generation 3 and 4 Pocket Colposcopes to a standard-of-care colposcope (Leisegang Optik 2). Specifically, paired images of cervices were collected from the standard-of-care colposcope and either the Generation 3 (n = 24 patients) or the Generation 4 (n = 32 patients) Pocket Colposcopes. The paired images were blinded by device, randomized, and sent to an expert physician who provided a diagnosis for each image. Corresponding pathology was obtained for all image pairs. The primary outcome measures were the level of agreement (%) and κ (kappa) statistic between the standard-of-care colposcope and each Pocket Colposcope (Generation 3 and Generation 4).ResultsBoth generations of Pocket Colposcope had significantly higher image contrast when compared to the standard-of-care colposcope. The addition of anti-fog and waterproofing features to the Generation 3 and 4 Pocket Colposcope did not impact image quality based on qualitative and quantitative metrics. The level of agreement between the Generation 3 Pocket Colposcope and the standard-of-care colposcope was 75.0% (kappa = 0.4000, p = 0.0028, n = 24). This closely matched the level of agreement between the Generation 4 Pocket Colposcope and the standard-of-care colposcope which was also 75.0% (kappa = 0.4941, p = 0.0024, n = 32).ConclusionOur results indicate that the Generation 3 and 4 Pocket Colposcopes perform comparably to the standard-of-care colposcope, with the added benefit of being low-cost and waterproof, which is ideal for use in resource-limited settings. Additionally, the reflector significantly reduces the electrical requirements of the Generation 4 Pocket Colposcope enhancing portability without altering performance compared to the Generation 3 system.

Ageing and proton irradiation damage of a low voltage EMCCD in a CMOS process

Electron Multiplying Charge Coupled Devices (EMCCDs) have revolutionised low light level imaging, providing highly sensitive detection capabilities. Implementing Electron Multiplication (EM) in Charge Coupled Devices (CCDs) can increase the Signal to Noise Ratio (SNR) and lead to further developments in low light level applications such as improvements in image contrast and single photon imaging. Demand has grown for EMCCD devices with properties traditionally restricted to Complementary Metal-Oxide-Semiconductor (CMOS) image sensors, such as lower power consumption and higher radiation tolerance. However, EMCCDs are known to experience an ageing effect, such that the gain gradually decreases with time. This paper presents results detailing EM ageing in an Electron Multiplying Complementary Metal-Oxide-Semiconductor (EMCMOS) device and its effect on several device characteristics such as Charge Transfer Inefficiency (CTI) and thermal dark signal. When operated at room temperature an average decrease in gain of over 20% after an operational period of 175 hours was detected. With many image sensors deployed in harsh radiation environments, the radiation hardness of the device following proton irradiation was also tested. This paper presents the results of a proton irradiation completed at the Paul Scherrer Institut (PSI) at a 10 MeV equivalent fluence of 4.15× 1010 protons/cm2. The pre-irradiation characterisation, irradiation methodology and post-irradiation results are detailed, demonstrating an increase in dark current and a decrease in its activation energy. Finally, this paper presents a comparison of the damage caused by EM gain ageing and proton irradiation.