Digital Phase Contrast Imaging Research Articles

Intelligent Phase Contrast Meta-Microscope System.

Phase contrast imaging techniques enable the visualization of disparities in the refractive index among various materials. However, these techniques usually come with a cost: the need for bulky, inflexible, and complicated configurations. Here, we propose and experimentally demonstrate an ultracompact meta-microscope, a novel imaging platform designed to accomplish both optical and digital phase contrast imaging. The optical phase contrast imaging system is composed of a pair of metalenses and an intermediate spiral phase metasurface located at the Fourier plane. The performance of the system in generating edge-enhanced images is validated by imaging a variety of human cells, including lung cell lines BEAS-2B, CLY1, and H1299 and other types. Additionally, we integrate the ResNet deep learning model into the meta-microscope to transform bright-field images into edge-enhanced images with high contrast accuracy. This technology promises to aid in the development of innovative miniature optical systems for biomedical and clinical applications.

Visualization of microvasculature by x-ray in-line phase contrast imaging in rat spinal cord

Computed tomography combined with angiography has recently been developed to visualize three-dimensional (3D) vascular structure in experi-mental and clinical studies. However, there remain difficulties in using conventional x-ray angiography to detect small vessels with a diameter less than 200 µm. This study attempted to develop a novel method for visualizing the micro-angioarchitecture of rat spinal cord. Herein, synchrotron radiation-based x-ray in-line phase contrast computed tomography (IL-XPCT) was used to obtain 3D micro-vessel structure without angiography. The digital phase contrast images were compared with conventional histological sections. Our results clearly demonstrated that the resolution limit of the spatial blood supply network in the normal rat thoracic cord appeared to be as small as ∼10 µm. The rendered images were consistent with that obtained from histo-morphology sections. In summary, IL-XPCT is a potential tool to investigate the 3D neurovascular morphology of the rat spinal cord without the use of contrast agents, and it could help to evaluate the validity of the pro- or anti-angiogenesis therapeutic strategies on microvasculature repair or regeneration.

Investigation of magnification factor and sampling pitch in digital phase contrast imaging

Investigation of magnification factor and sampling pitch in digital phase contrast imaging

Image-quality assessment method for digital phase-contrast imaging based on two-dimensional power spectral analysis

With use of the phase shift of X-rays that occurs when they pass through an object, phase-contrast imaging (herein referred to as "phase imaging") can produce images different from those of conventional contact imaging (herein referred to as "conventional imaging"). For this reason, assessment of the image quality based on noise-equivalent quanta (NEQ) and detective quantum efficiency (DQE) which does not include object-based information may not be appropriate for comparison of image quality between phase and conventional images. As an alternative method, we conceived a new image-quality assessment method with images that contain information about an object. First, we constructed images with an object and without an object under the same imaging parameters; then, we obtained two-dimensional power spectra by Fourier transform of those images. Second, we calculated the radial direction distribution function with the power spectra, and the distribution of signal intensity, which we defined as a signal intensity distribution function (SIDF). In this way, differences in image quality were evaluated relatively based on the SIDF of the imaged object. In our study, we first confirmed that phase-imaging evaluation was not appropriate by comparing NEQ and DQE of conventional, magnification, and phase imaging. Further, comparing the image quality of projected plant seeds by employing conventional, magnification, and phase imaging, we found that the phase-imaging method provided a higher image quality regarding edge sharpness than did conventional and magnification imaging. Therefore, based on these results, our image assessment method is considered useful for evaluation of images which include object-based information.

Dynamics of Chromosome Compaction during Mitosis

We have quantitatively studied the space–time dynamics of mitotic chromosome compaction in cultured amphibian cells. After collecting digital phase-contrast images we have done digital image analysis to study spatial correlations in density. We find a characteristic distance at which the strongest correlations occur, which provides a quantitative measure of the size of patches of dense chromatin during interphase and early prophase. Later in mitosis, this length corresponds to the thickness of prophase and metaphase chromosomes. We find that during interphase strong correlations exist at a few-micrometer length; during prophase this correlation length progressively drops as the chromosomes are compacted. Our data are explained by a model based on assembly of chromatin loops onto already fiberlike interphase chromosomes. To test this model we have microinjected cobalt hexamine trichloride into interphase nuclei and have observed the rapid condensation of the interphase chromatin into thick fibers with a spacing similar to the native-state interphase correlation length determined from our image analysis.

An innovative digital imaging set-up allowing a low-dose approach to phase contrast applications in the medical field.

Recently, new imaging modalities based on the detection of weak phase perturbations effects, among which are phase contrast and diffraction imaging, have been developed by several researchers. Due to their high sensitivity to weakly absorbing details, these techniques seem to be very promising for applications in the medical field. On the other hand, digital radiology is undergoing a wide diffusion, and its benefits are presently very well understood. Up to now, however, the strong pixel size constraints associated with phase contrast pattern detection limited the possibility of exploiting the advantages of phase contrast in digital radiology applications. In this paper, an innovative setup capable of removing the pixel size constraints, and thus opening the way to low dose digital phase contrast imaging, is described. Furthermore, we introduce an imaging technique based on the detection of radiation scattered at small angles: the information extracted from the sample is increased at no dose expense. We believe that several radiological fields, mammography being the first important example, may benefit from the herein described innovative imaging techniques.