Sensitive Imaging System Research Articles

Puff, the polytene chromosome: Visualizing transcription elongation control

In this issue, Versluis etal.1 use a highly sensitive live-cell imaging system to examine transcription dynamics and functions of various key transcription elongation regulators at the Hsp70 loci.

Millimeter-Wave Band Electro-Optical Imaging System Using Polarization CMOS Image Sensor and Amplified Optical Local Oscillator Source.

In this study, we developed and demonstrated a millimeter-wave electric field imaging system using an electro-optic crystal and a highly sensitive polarization measurement technique using a polarization image sensor, which was fabricated using a 0.35-µm standard CMOS process. The polarization image sensor was equipped with differential amplifiers that amplified the difference between the 0° and 90° pixels. With the amplifier, the signal-to-noise ratio at low incident light levels was improved. Also, an optical modulator and a semiconductor optical amplifier were used to generate an optical local oscillator (LO) signal with a high modulation accuracy and sufficient optical intensity. By combining the amplified LO signal and a highly sensitive polarization imaging system, we successfully performed millimeter-wave electric field imaging with a spatial resolution of 30×60 µm at a rate of 1 FPS, corresponding to 2400 pixels/s.

Design and Performance Analysis of the Highly Sensitive Deep Vacuum Cooling sCMOS Imaging System for Highly Sensitive Detection of Space Targets

The sCMOS imaging system with deep vacuum cooling technology has become a necessary way to improve the detection capability of space targets. In order to improve the detection capability of the photoelectric detection equipment for space targets, this paper developed the Highly Sensitive Deep Vacuum Cooling Imaging System (HSDVCIS). Firstly, we designed the imaging readout processing circuit using the GSENSE4040 sCMOS image sensor designed and manufactured by Gpixel and the deep vacuum cooling structure using thermoelectric cooling. Then, we tested the designed HSDVCIS with readout noise, dark current, and dynamic range of 3.96 e−, 0.12 e−/pixel/sec, and 84.49 dB, respectively, and tested the image sensor with a minimum cooling temperature of −40 °C. Finally, according to the results of observation experiments, we validated that the photoelectric detection equipment equipped with HSDVCIS improved the limiting detection magnitude (at SNR = 5 level) from 13.22 to 13.51 magnitudes within a 3 s exposure time by turning on the cooling function. Therefore, HSDVCIS designed in this paper can achieve highly sensitive detection of space targets. At the same time, the development of HSDVCIS also provides technical reserves and strong support for future research on the imaging systems using multiple image sensor mosaics.

Toward the clinical application of ultrasound molecular imaging in the early detection of breast cancer

Ultrasound molecular imaging has large potential in the early detection of breast cancer, particularly in women with radiographically dense breasts. In ultrasound molecular imaging, a molecularly-targeted ligand attached to a microbubble binds to proteins expressed on the tumor neovasculature to produce contrast that can identify cancer at an early stage. Keys to successful ultrasound molecular imaging are: (1) a molecular target highly specific to breast cancer; and (2) a sensitive imaging system that can visualize bound microbubbles while suppressing bubble signal from the background. In addition, the system must integrate with existing ultrasound imaging workflow in breast imaging clinics. We present our current progress on the development of a real-time ultrasound molecular imaging platform that consists of a novel microbubble targeted to the B7-H3 biomarker (a vascular biomarker highly specific to breast cancer and not expressed in benign disease processes) alongside a nondestructive and real-time imaging technology, based on a neural network design for contrast imaging to enable real-time high-sensitivity imaging of the novel targeted contrast agent. Although we present the results and current status of this system in preclinical models of breast cancer, the targeted microbubble is designed to be pharmaceutical grade to allow it to be injected in humans, and the imaging technology is designed such that it is compatible with current clinical workflow and operation of breast ultrasound imaging.

Activated CMPs Act in Concert with the Spleen and Accelerate Hematopoietic Inflation after Transplantation

Hematopoietic stem cells (HSC) represent the apex of the hematopoietic hierarchy and their engraftment post-transplantation is essential for long-term donor hematopoiesis. After transplantation, injected HSCs rapidly expand to reconstitute the entire blood system. This early post-transplant "hematopoietic inflation" is a crucial phase in sustaining life. However, the time course of hematopoietic inflation and the spatial transition within the whole body have remained a mystery. The discovery of colonies forming in the spleen early after HSC transplantation in the 1960s has been a strong advocate of the existence of HSCs, but biological role of transient nature of spleen colonies has not been understood. In this study, we elucidated the spatiotemporal dynamics of hematopoietic inflation in the same individual in a murine HSC transplantation model. Current methods for tracking transplanted HSCs in vivo are limited due to their low sensitivity and their restriction to observe only previously known niches. To address these issues, we used the recently published, highly sensitive AkaLuc bioluminescence imaging system to visualize hematopoietic inflation in vivo. We combined Akaluc 3D images with CT scans to spatially capture early hematopoiesis after transplantation on a whole-body scale, and continuously monitored bioluminescence signals to clarify the dynamics of cellular distributions over time. Surprisingly, our data show that the spleen acts as a major site of hematopoiesis and shows unique hematopoietic patterns with dynamic changes. Splenic hematopoiesis was distinct from that occurring in the bone marrow and each progenitor cell has a different hematopoietic inflation pattern. We found that activated common myeloid progenitors (aCMPs) use the spleen as a site for hematopoietic inflation, producing much more cells early after transplantation than normal CMPs. Based on these findings, we developed expanded CMPs (exCMPs) that leverage the spleen environment to improve early hematopoietic recovery after transplantation. exCMPs, which can be produced in large quantities in polyvinyl-alcohol (PVA)-based cultures (Wilkinson et al., Nature 2019), had lower CXCR4 expression, different integrin expression patterns, better cytokine responsiveness and mitogenic potential, as well as higher expression of platelet-related genes compared to fresh CMP. Therefore, exCMPs are more likely to migrate to the spleen and proliferate more rapidly than fresh CMPs. Exploiting these properties, we could show that weekly administration of exCMP allowed for the long-term survival of lethally irradiated mice in a spleen-dependent manner. In the allogeneic transplantation setting, universal exCMPs could sustain life for a long time by a serial transplantation. Human exCMPs could be easily expanded as well, and the clinical use of human exCMPs is highly anticipated as a supportive therapy after HSCT. Our studies of post-transplant hematopoiesis using a next-generation luminescence imaging system showed that the spleen functioned as a major hematopoietic tissue and that aCMPs and the spleen cooperated to contribute to hematopoietic inflation post-SCT, which led to the concept of utilizing the spleen as an alternative hematopoietic site. These findings refine our understanding of the dynamics of hematopoietic reconstitution, reveal the unique collaboration of the spleen and transplanted cells and establish the therapeutic potential of exCMPs for early hematopoietic recovery. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Super-resolved three-dimensional near-field mapping by defocused imaging and tracking of fluorescent emitters.

Near-field optics is essential in many nanotechnology applications, such as implementing sensitive biosensing and imaging systems with extreme precision. Understanding optical near-fields at the nanoscale has so attracted the considerable research interest, which use a variety of analytical approaches, most notably near-field scanning microscopy. Here, we show defocused point localization mapped accumulation (DePLOMA), which can overcome many weaknesses of conventional analytical methods. DePLOMA is based on imaging fluorescence emitters at an out-of-focal plane. The acquisition, collection, and accumulation of the position and fluorescence intensity of emitters moving above nanostructures can generate three-dimensional near-field maps of light distribution. The idea enables super-resolution liquid-phase measurements, as demonstrated by reconstruction of near-field created by nanoslits with a resolution determined by emitter size. We employed fluorescent emitters with a radius of 50 and 100nm for confirmation. The axial resolution was found to be enhanced by more than 6 times above that of diffraction-limited confocal laser scanning microscopy when DePLOMA was used.

Analyzing the Electronics of Image Sensors and Their Functionality to Develop Low Light-Emitting Source Image

Bioluminescence imaging has been used to visualize the biological effects of human beings and is a promising technique in a recent modality. In this study, the digital image technique is used to improve quality and recover images. The optical fluence that emerges from the source is generated using a camera, and a low resgolution is observed. In this paper, the diurnal change of ultra-weak photon emission was successfully imaged with an improved, highly sensitive imaging system using a charge-coupled device (CCD) camera. The changes in energy metabolism might be linked with diurnal changes in photon emission, and when observed, the body emits extremely weak light spontaneously without external photoexcitation. Therefore, to obtain accurate information, a combined Barn Door Star Tracker approach has been proposed to improve the accuracy of the method and has been implemented to test on celestial bodies. The ability to temporally assess the location of star movement can be monitored accurately with bioluminescence imaging.

P1418: EXPANDED COMMON MYELOID PROGENITORS ACT IN CONCERT WITH THE SPLEEN AND SUPPORT EARLY HEMATOPOIETIC RECOVERY

Background: Hematopoietic stem cells (HSC) represent the apex of the hematopoietic hierarchy and their engraftment post-transplantation is essential for long-term donor hematopoiesis. After intravenous injection, HSCs are thought to home directly toward the bone marrow niche, and their homing mechanisms and interactions with the microenvironment have been intensively studied. However, the time course of the transplanted HSCs to reconstitute the entire blood system and the spatial transition within the whole body have remained a mystery. Aims: We aim to elucidate the spatiotemporal dynamics of hematopoiesis in the same individual in a murine HSC transplantation model. Methods: Current methods for tracking transplanted HSCs in vivo are limited due to their low sensitivity and their restriction to observe only previously known niches. To address these issues, we used the recently published, highly sensitive AkaLuc bioluminescence imaging system to visualize HSC migration in vivo. We combined Akaluc 3D images with CT scans to spatially capture early hematopoiesis after transplantation on a whole-body scale, and continuously monitored bioluminescence signals to clarify the dynamics of cellular distributions over time. Results: Surprisingly, our data show that the spleen acts as a major site of hematopoiesis and shows unique hematopoietic patterns with dynamic changes. Splenic hematopoiesis was distinct from that occurring in the bone marrow and we found that common myeloid progenitors (CMPs) use the spleen as a site for hematopoiesis, producing many cells early after transplantation. Based on these findings, we developed expanded CMPs (exCMPs) that leverage the spleen environment to improve early hematopoietic recovery after transplantation. exCMPs, which can be produced in large quantities in polyvinyl-alcohol (PVA)-based cultures (Wilkinson et al., Nature 2019), had lower CXCR4 expression, different integrin expression patterns, better cytokine responsiveness and mitogenic potential, as well as higher expression of platelet-related genes compared to fresh CMP. Therefore, exCMPs are more likely to migrate to the spleen and proliferate more rapidly than fresh CMPs. Exploiting these properties, we could show that weekly administration of exCMP allowed for the long-term survival of lethally irradiated mice in a spleen-dependent manner. Image:Summary/Conclusion: Our studies of post-transplant hematopoiesis using a next-generation luminescence imaging system showed that the spleen functioned as a major hematopoietic tissue and that CMPs and the spleen cooperated to contribute to early hematopoiesis post-SCT, which led to the concept of utilizing the spleen as an alternative hematopoietic site. These findings refine our understanding of the dynamics of hematopoietic reconstitution, reveal the unique collaboration of the spleen and transplanted cells and establish the therapeutic potential of exCMPs for early hematopoietic recovery.

Sensitive and real-time detection of IgG using interferometric reflecting imaging sensor system

Considering the limitations of well-known traditional detection techniques, innovative research studies have focused on the development of new sensors to offer label-free, highly sensitive, real-time, low-cost, and rapid detection for biomolecular interactions. In this study, we demonstrate immunoglobulin G (IgG) detection in aqueous solutions by using real-time and label-free kinetic measurements of the Interferometric Reflectance Imaging Sensor (IRIS) system. By performing kinetic characterization experiments, the sensor's performance is comprehensively evaluated and a high correlation coefficient value (>0.94) is obtained in the IgG concentration range of 1–50 μg/mL with a low detection limit (0.25 μg/mL or 1.67 nM). Moreover, the highly sensitive imaging system ensures accurate quantification and reliable validation of recorded binding events, offering new perspectives in terms of direct biomarker detection for clinical applications.

Dual-energy phase retrieval algorithm for inline phase sensitive x-ray imaging system.

Phase retrieval is vital for quantitative x-ray phase contrast imaging. This work presents an iterative method to simultaneously retrieve the x-ray absorption and phase images from a single x-ray exposure. The proposed approach uses the photon-counting detectors' energy-resolving capability in providing multiple spectrally resolved phase contrast images from a single x-ray exposure. The retrieval method is derived, presented, and experimentally tested with a multi-material phantom in an inline phase contrast imaging setup. By separating the contributions of photoelectric absorption and Compton scattering to the attenuation, the authors divide the phase contrast image into two portions, the attenuation map arises from photoelectric absorption and a pseudo phase contrast image generated by electron density. This way one can apply the Phase Attenuation Dualiby (PAD) algorithm and Fresnel propagation for the iteration. The retrieval results from the experimental images show that this iterative method is fast, accurate, robust against noise, and thus yields noticeable enhancement in contrast to noise ratios.

Profile-based intensity and frequency corrections for single-snapshot spatial frequency domain imaging.

We have proposed the profile-based intensity and frequency corrections for single-snapshot spatial frequency domain (SFD) imaging to mitigate surface profile effects on the measured intensity and spatial frequency in extracting the optical properties. In the scheme, the spatially modulated frequency of the projected sinusoidal pattern is adaptively adjusted according to the sample surface profile, reducing distortions of the modulation amplitude in the single-snapshot demodulation and errors in the optical property extraction. The profile effects on both the measured intensities of light incident onto and reflected from the sample are then compensated using Minnaert's correction to obtain the true diffuse reflectance of the sample. We have validated the method by phantom experiments using a highly sensitive SFD imaging system based on the single-pixel photon-counting detection and assessed error reductions in extracting the absorption and reduced scattering coefficients by an average of 40% and 10%, respectively. Further, an in vivo topography experiment of the opisthenar vessels has demonstrated its clinical feasibility.

Non-contact measurement of internal body temperature using subcutaneously implanted diamond microparticles.

We constructed a highly sensitive fluorescence wide-field imaging system with a microwave source, implanted fluorescent diamond microparticles ("microdiamonds") subcutaneously into the dorsal skin of a mouse after sacrifice, and demonstrated the feasibility of using optically detected magnetic resonance (ODMR) to measure internal body temperature in a mammal.

Thermally sensitive fluorescence imaging system for radiofrequency ablation guidance

Radiofrequency ablation (RFA) has been clinically used as a minimally invasive procedure for the treatment of many solid tumors. However, the current imaging techniques have some shortages in RFA guidance, especially for the assessment of the margin of ablation. Herein, we developed a novel optical imaging platform to guide RFA utilizing fluorescence resonance energy transfer from a thermally sensitive fluorescent protein conjugated to a near-infrared fluorescent dye. Additionally, attaching receptor-targeting ligands further equipped the system with high specificity to tumors overexpressing the targeted receptor.

Real-time Bioluminescence Imaging of Notch Signaling Dynamics during Murine Neurogenesis.

Notch signaling regulates the maintenance of neural stem/progenitor cells by cell-cell interactions. The components of Notch signaling exhibit dynamic expression. Notch signaling effector Hes1 and the Notch ligand Delta-like1 (Dll1) are expressed in an oscillatory manner in neural stem/progenitor cells. Because the period of the oscillatory expression of these genes is very short (2 h), it is difficult to monitor their cyclic expression. To examine such rapid changes in the gene expression or protein dynamics, fast response reporters are required. Because of its fast maturation kinetics and high sensitivity, the bioluminescence reporter luciferase is suitable to monitor rapid gene expression changes in living cells. We used a destabilized luciferase reporter for monitoring the promoter activity and a luciferase-fused reporter for visualization of protein dynamics at single cell resolution. These bioluminescence reporters show rapid turnover and generate very weak signals; therefore, we have developed a highly sensitive bioluminescence imaging system to detect such faint signals. These methods enable us to monitor various gene expression dynamics in living cells and tissues, which are important information to help understand the actual cellular states.

Multi-wavelength spatial frequency domain diffuse optical tomography using single-pixel imaging based on lock-in photon counting.

We present a spatial frequency domain (SFD) diffuse optical tomography for simultaneous acquisition of multi-wavelength tomographic images of turbid media. We propose a highly sensitive single-pixel SFD imaging system for simultaneously collecting multi-wavelength spatially modulated reflectance images, instead of using the expensive electron-multiplying charge-coupled device camera that requires switching between the multi-wavelength collections. The single-pixel SFD imaging system using three low-power light sources (455, 532 and 660 nm) that were intensity-modulated by square waves with three different frequencies for frequency encoding, and all the light sources were focused onto one digital micromirror device (DMD) for generating wide-field sinusoidal illumination patterns. Reflected light from the surface of the turbid media was modulated by the other DMD with many sampling patterns before being spatially integrated. Spatially integrated light signals were frequency decoded with a novel highly sensitive lock-in photon counting detection, then multi-wavelength spatially modulated reflectance images were recovered with the single-pixel imaging (SPI) method. We incorporated the two-dimensional discrete cosine transform (DCT) into the SPI method to reduce the number of sampling patterns, and, thereby, the proposed DCT-SPI scheme achieved a fast acquisition of SFD reflectance images that is desired for a dynamic SFD imaging application. Direct current (DC) and alternating current (AC) amplitudes at all the locations on the media surface were extracted from the recovered images. Multi-wavelength tomographic images were reconstructed with an inversion algorithm based on the first-order Rytov approximation of the diffusion equation, using both the extracted DC and AC amplitudes. We performed experiments using a series of tissue simulating phantoms to verify the performances of the proposed approach and compared the experimental results with those using a conventional camera-based SFD imaging system. The results demonstrate that our DCT-SPI based SFD-DOT approach is well suited for simultaneous reconstruction of multi-wavelength tomographic images to pave the way for many SFD imaging applications.

Imaging of ultraweak photon emission for evaluating the oxidative stress of human skin

Ultraweak photon emission (UPE) is generally observed in living organisms and often designated as biophoton emission. UPE is detectable from human skin, and its intensity increases by external stress such as ultraviolet (UV) irradiation. Presently, UPE measurement is used to evaluate oxidation status. The fact that the electronically excited species responsible for UPE are formed by reactive oxygen species (ROS)-induced lipid peroxidation and protein and nucleic acid oxidation is well known. The human skin undergoes oxidative stress by UV irradiation, resulting in various skin complications; therefore, it is essential to know the oxidation status of the skin. In this study, we assessed the characteristics of UV-induced UPE in the skin by the imaging and spectroscopy systems. Two-dimensional images obtained by a highly sensitive imaging system using a cooled charge-coupled device (CCD) camera revealed that UPE intensity increases with the amount of UV and is suppressed by antioxidants. Additionally, it is indicated that UPE is generated not only from the epidermis but also from the dermis. The spectra of UPE induced by UVA or UVB showed similar peaks in the visible light region. Furthermore, we confirmed the efficiency of sunscreen by the imaging technique. UPE measurement is a useful method to evaluate UV-induced oxidation in the human skin, and UPE imaging is an effective method to visually evaluate oxidative stress in the human skin.

Imaging Collagen Properties in the Uterosacral Ligaments of Women With Pelvic Organ Prolapse Using Spatial Light Interference Microscopy (SLIM)

We studied collagen fiber organization in tissue affected by pelvic organ prolapse (POP) and compared it to asymptomatic controls. Both the control and POP tissue biopsies were prepared and measured by a highly sensitive quantitative phase imaging (QPI) system, called spatial light inference microscopy (SLIM). Combined with automatic image processing, this modality provides quantitative, high-throughput assessment of fiber morphology. We found the fiber orientation in prolapsed specimens is less homogeneous, indicating an abnormal organization of collagen in the extracellular matrix (ECM).

Perspective: Terahertz wave parametric generator and its applications

The injection-seeded terahertz (THz) parametric generator (is-TPG) is one of the most high-power single-longitudinal mode THz-wave sources. Our system is less influenced by scattering, refraction, and multiple reflections by samples because it is a narrow-linewidth source, and the detection area of the THz parametric detector is large. Thus, it is suitable for nondestructive inspection of practical samples in the real world. In 2003, we reported on the development of a mail inspection system that employed a THz parametric oscillator. However, with a dynamic range of less than four orders of magnitude, this system could only identify reagents through thin envelopes. Recently, we succeeded in developing a high-power, highly sensitive THz-wave spectroscopic imaging system with a dynamic range of 100 dB using the is-TPG and a THz parametric detector. Nondestructive inspection of reagents inside thick envelopes and three-dimensional computed tomography of plastics, which attenuate THz-waves by more than 60 dB, were conducted using this system. More recently, we have focused our efforts on a real-time measurement system using a multiwavelength is-TPG, which gives rise to numerous potential applications, given the significantly shorter measurement times. Thus, this system will facilitate the implementation of THz-wave measurements in real-world applications. In this paper, we report on our recent results and provide a perspective on the is-TPG.

Detectability comparison of simulated tumors in digital breast tomosynthesis using high-energy X-ray inline phase sensitive and commercial imaging systems

This study compared the detectability of simulated tumors using a high-energy X-ray inline phase sensitive digital breast tomosynthesis (DBT) prototype and a commercial attenuation-based DBT system. Each system imaged a 5-cm thick modular breast phantom with 50–50 adipose-glandular percentage density containing contrast-detail (CD) test objects to simulate different tumor sizes. A commercial DBT system acquired 15 projection views over 15 degrees (15d-15p) was used to acquire the attenuation-based projection views and to reconstruct the conventional DBT slices. Attenuation-based projection views were acquired at 32 kV, 46 mAs with a mean glandular dose (Dg) of 1.6 mGy. For acquiring phase sensitive projection views, the prototype utilized two acquisition geometries: 11 projection views were acquired over 15 degrees (15d-11p), and 17 projection views were acquired over 16 degrees (16d-17p) at 120 kV, 5.27 mAs with 1.51 mGy under the magnification (M) of 2. A phase retrieval algorithm based on the phase-attenuation duality (PAD) was applied to each projection view, and a modified Feldkamp-Davis-Kress (FDK) algorithm was used to reconstruct the phase sensitive DBT slices. Simulated tumor margins were rated as more conspicuous and better visualized for both phase sensitive acquisition geometries versus conventional DBT imaging. The CD curves confirmed the improvement in both contrast and spatial resolutions with the phase sensitive DBT imaging. The superiority of the phase sensitive DBT imaging was further endorsed by higher contrast to noise ratio (CNR) and figure-of-merit (FOM) values. The CNR improvements provided by the phase sensitive DBT prototype were sufficient to offset the noise reduction provided by the attenuation-based DBT imaging.

An integrated and highly sensitive ultrafast acoustoelectric imaging system for biomedical applications

Direct imaging of the electrical activation of the heart is crucial to better understand and diagnose diseases linked to arrhythmias. This work presents an ultrafast acoustoelectric imaging (UAI) system for direct and non-invasive ultrafast mapping of propagating current densities using the acoustoelectric effect.Acoustoelectric imaging is based on the acoustoelectric effect, the modulation of the medium’s electrical impedance by a propagating ultrasonic wave. UAI triggers this effect with plane wave emissions to image current densities. An ultrasound research platform was fitted with electrodes connected to high common-mode rejection ratio amplifiers and sampled by up to 128 independent channels. The sequences developed allow for both real-time display of acoustoelectric maps and long ultrafast acquisition with fast off-line processing. The system was evaluated by injecting controlled currents into a saline pool via copper wire electrodes. Sensitivity to low current and low acoustic pressure were measured independently. Contrast and spatial resolution were measured for varying numbers of plane waves and compared to line per line acoustoelectric imaging with focused beams at equivalent peak pressure. Temporal resolution was assessed by measuring time-varying current densities associated with sinusoidal currents. Complex intensity distributions were also imaged in 3D.Electrical current densities were detected for injected currents as low as 0.56 mA. UAI outperformed conventional focused acoustoelectric imaging in terms of contrast and spatial resolution when using 3 and 13 plane waves or more, respectively. Neighboring sinusoidal currents with opposed phases were accurately imaged and separated. Time-varying currents were mapped and their frequency accurately measured for imaging frame rates up to 500 Hz. Finally, a 3D image of a complex intensity distribution was obtained. The results demonstrated the high sensitivity of the UAI system proposed. The plane wave based approach provides a highly flexible trade-off between frame rate, resolution and contrast. In conclusion, the UAI system shows promise for non-invasive, direct and accurate real-time imaging of electrical activation in vivo.