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Purpose: Phase contrast MRI (PC‐MRI) is used clinically to measure velocities in the body, but systematic background phase errors caused by magnetic field imperfections corrupt the velocity measurements with offsets that limit clinical utility. This work aims to minimize systematic background phase errors in PC‐MRI, thereby maximizing the accuracy of velocity measurements. Methods: The MRI scanner's background phase errors from eddy currents and mechanical oscillations were modeled using the gradient impulse response function (GIRF). Gradient waveforms were then numerically optimized using the GIRF to create pulse sequences that minimize the background phase errors. The pulse sequences were tested in a static phantom where the predicted response could be compared directly to the measured background velocity. The optimized acquisitions were then tested in human subjects, where flow rates and background errors were compared to conventional PC‐MRI. Results: When using the GIRF‐optimized gradient waveforms, the predicted background phase was within 0.6 [95% CI = −3.4, 5.4] mm/s of the measured background phase in a static phantom. Excellent agreement was seen for in vivo blood flow values (flow rate agreement r2$$ {r}^2 $$ = 0.96), and the background phase was reduced by 78.8 ±$$ \pm $$ 18.7%. Conclusion: This work shows that using a GIRF to model the effects of magnetic field imperfections combined with numerically optimized gradient waveforms enables PC‐MRI waveforms to be designed to produce a minimal background phase in the most time‐efficient manner. The methodology could be adapted for other MRI sequences where similar magnetic field errors affect measurements. [ABSTRACT FROM AUTHOR]

Phase contrast imaging is well-suited for studying weakly scattering samples. Its strength lies in its ability to measure how the phase of the electron beam is affected by the sample, even when other imaging techniques yield low contrast. In this study, we explore via simulations two phase contrast techniques: integrated center of mass (iCOM) and ptychography, specifically using the extended ptychographical iterative engine (ePIE). We simulate the four-dimensional scanning transmission electron microscopy (4D-STEM) datasets for specific parameters corresponding to a scanning electron microscope (SEM) with an immersive objective and a given pixelated detector. The performance of these phase contrast techniques is analyzed using a contrast transfer function. Simulated datasets from a sample consisting of graphene sheets and carbon nanotubes are used for iCOM and ePIE reconstructions for two aperture sizes and two electron doses. We highlight the influence of aperture size, showing that for a smaller aperture, the radiation dose is spent mostly on larger sample features, which may aid in imaging sensitive samples while minimizing radiation damage. [ABSTRACT FROM AUTHOR]

Background: Standard Cartesian time‐of‐flight (TOF) head magnetic resonance angiography (MRA) is routinely used to evaluate the intracranial arteries, but does not provide quantitative hemodynamic information that is useful for patient risk stratification as well as for monitoring treatment and tracking changes in blood flow over time. Quantitative TOF (qTOF) MRA represents a new and efficient method for simultaneous evaluating the intracranial arteries and quantifying blood flow velocity, but it has not yet been evaluated in patients with cerebrovascular disease. Purpose: To evaluate qTOF for simultaneously evaluating the intracranial arteries and quantifying intracranial blood flow velocity in patients with cerebrovascular disease, without the need for a phase contrast (PC) scan. Study Type: Prospective. Subjects: Twenty‐four patients (18 female, 6 male) with cerebrovascular disease. Field Strength/Sequences: Head MRA at 3 T using gradient‐echo 3D qTOF, standard Cartesian TOF, and PC protocols. Assessment: Three independent readers assessed arterial image quality using a 4‐point scale (1: non‐diagnostic, 4: excellent) and artifact presence. Total and component flow velocities obtained with qTOF and PC were measured. Statistical Tests: Wilcoxon signed‐rank tests, Gwet's AC2, intraclass correlation coefficients (ICC) for absolute agreement, Bland–Altman analyses, tests of equal proportions. P values <0.05 were considered statistically significant. Results: Averaged across readers and compared to standard Cartesian TOF, qTOF significantly improved overall arterial image quality (3.8 ± 0.2 vs. 3.6 ± 0.5), image quality at locations of pathology (3.7 ± 0.5 vs. 3.4 ± 0.7), and increased the proportion of evaluations rated without artifacts (63.9% [46/72] vs. 37.5% [27/72]). qTOF significantly agreed with PC for total flow velocity (ICC = 0.71) and component flow velocity (ICC = 0.89). Data Conclusion: qTOF angiography of the head matched or improved upon the image quality of standard Cartesian TOF, reduced image artifacts, and provided quantitative hemodynamic data, without the need for a PC scan. Evidence Level: 2 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

Abstract In the last decade, grating-based phase-contrast computed tomography (gbPC-CT) has received growing interest. It provides additional information about the refractive index decrement in the sample. This signal shows an increased soft-tissue contrast. However, the resolution dependence of the signal poses a challenge: its contrast enhancement is overcompensated by the low resolution in low-dose applications such as clinical computed tomography. As a result, the implementation of gbPC-CT is currently tied to a higher dose. To reduce the dose, we introduce the self-supervised deep learning network Noise2Inverse into the field of gbPC-CT. We evaluate the behavior of the Noise2Inverse parameters on the phase-contrast results. Afterward, we compare its results with other denoising methods, namely the Statistical Iterative Reconstruction, Block Matching 3D, and Patchwise Phase Retrieval. In the example of Noise2Inverse, we show that deep learning networks can deliver superior denoising results with respect to the investigated image quality metrics. Their application allows to increase the resolution while maintaining the dose. At higher resolutions, gbPC-CT can naturally deliver higher contrast than conventional absorption-based CT. Therefore, the application of machine learning-based denoisers shifts the dose-normalized image quality in favor of gbPC-CT, bringing it one step closer to medical application.

Abstract Phase contrast x-ray imaging (PCXI) provides high-contrast images of weakly-attenuating structures like the lungs. PCXI, when paired with 4D X-ray Velocimetry (XV), can measure regional lung function and non-invasively assess the efficacy of emerging therapeutics. Bacteriophage therapy is an emerging antimicrobial treatment option for lung diseases such as cystic fibrosis (CF), particularly with increasing rates of multi-drug-resistant infections. Current efficacy assessment in animal models is highly invasive, typically requiring histological assessment. We aim to use XV techniques as non-invasive alternatives to demonstrate efficacy of bacteriophage therapy for treating Pseudomonas aeruginosa CF lung infections, measuring functional changes post-treatment. Time-resolved in vivo PCXI-CT scans of control, Pseudomonas-infected, and phage-treated mouse lungs were taken at the Australian Synchrotron Imaging and Medical Beamline. Using XV we measured local lung expansion and ventilation throughout the breath cycle, analysing the skew of the lung expansion distribution. CT images allowed visualisation of the projected air volume in the lungs, assessing structural lung damage. XV analysis demonstrated changes in lung expansion between infection and control groups, however there were no statistically significant differences between treated and placebo groups. In some cases where structural changes were not evident in the CT scans, XV successfully detected changes in lung function.

Abstract Neutron imaging has gained significant importance as a material characterisation technique and is particularly useful to visualise hydrogenous materials in objects opaque to other radiations. Fields of application include investigations of hydrogen in metals as well as metal corrosion, thanks to the fact that neutrons can penetrate metals better than e.g. X-rays and are highly sensitive to hydrogen. However, at interfaces refraction effects sometimes obscure the attenuation image, which is used for hydrogen quantification. Refraction, a differential phase effect, diverts the neutron beam away from the interface in the image leading to intensity gain and intensity loss regions, which are superimposed to the attenuation image, thus obscuring the interface region and hindering quantitative analyses of e.g. hydrogen content in the vicinity of the interface. For corresponding effects in X-ray imaging, a phase filter approach was developed and is generally based on transport-of-intensity considerations. Here, we compare such an approach, that has been adapted to neutrons, with another simulation-based assessment using the ray-tracing software McStas. The latter appears superior and promising for future extensions which enable fitting forward models via simulations in order to separate phase and attenuation effects and thus pave the way for overcoming quantitative limitations at refracting interfaces.

In the last decade, grating-based phase-contrast computed tomography (gbPC-CT) has received growing interest. It provides additional information about the refractive index decrement in the sample. This signal shows an increased soft-tissue contrast. However, the resolution dependence of the signal poses a challenge: its contrast enhancement is overcompensated by the low resolution in low-dose applications such as clinical computed tomography. As a result, the implementation of gbPC-CT is currently tied to a higher dose. To reduce the dose, we introduce the self-supervised deep learning network Noise2Inverse into the field of gbPC-CT. We evaluate the behavior of the Noise2Inverse parameters on the phase-contrast results. Afterward, we compare its results with other denoising methods, namely the Statistical Iterative Reconstruction, Block Matching 3D, and Patchwise Phase Retrieval. In the example of Noise2Inverse, we show that deep learning networks can deliver superior denoising results with respect to the investigated image quality metrics. Their application allows to increase the resolution while maintaining the dose. At higher resolutions, gbPC-CT can naturally deliver higher contrast than conventional absorption-based CT. Therefore, the application of machine learning-based denoisers shifts the dose-normalized image quality in favor of gbPC-CT, bringing it one step closer to medical application. [ABSTRACT FROM AUTHOR]

Phase contrast x-ray imaging (PCXI) provides high-contrast images of weakly-attenuating structures like the lungs. PCXI, when paired with 4D X-ray Velocimetry (XV), can measure regional lung function and non-invasively assess the efficacy of emerging therapeutics. Bacteriophage therapy is an emerging antimicrobial treatment option for lung diseases such as cystic fibrosis (CF), particularly with increasing rates of multi-drug-resistant infections. Current efficacy assessment in animal models is highly invasive, typically requiring histological assessment. We aim to use XV techniques as non-invasive alternatives to demonstrate efficacy of bacteriophage therapy for treating Pseudomonas aeruginosa CF lung infections, measuring functional changes post-treatment. Time-resolved in vivo PCXI-CT scans of control, Pseudomonas-infected, and phage-treated mouse lungs were taken at the Australian Synchrotron Imaging and Medical Beamline. Using XV we measured local lung expansion and ventilation throughout the breath cycle, analysing the skew of the lung expansion distribution. CT images allowed visualisation of the projected air volume in the lungs, assessing structural lung damage. XV analysis demonstrated changes in lung expansion between infection and control groups, however there were no statistically significant differences between treated and placebo groups. In some cases where structural changes were not evident in the CT scans, XV successfully detected changes in lung function. [ABSTRACT FROM AUTHOR]

Purpose: Tricuspid valve flow velocities are challenging to measure with cardiovascular MR, as the rapidly moving valvular plane prohibits direct flow evaluation, but they are vitally important to diastolic function evaluation. We developed an automated valve‐tracking 2D method for measuring flow through the dynamic tricuspid valve. Methods: Nine healthy subjects and 2 patients were imaged. The approach uses a previously trained deep learning network, TVnet, to automatically track the tricuspid valve plane from long‐axis cine images. Subsequently, the tracking information is used to acquire 2D phase contrast (PC) with a dynamic (moving) acquisition plane that tracks the valve. Direct diastolic net flows evaluated from the dynamic PC sequence were compared with flows from 2D‐PC scans acquired in a static slice localized at the end‐systolic valve position, and also ventricular stroke volumes (SVs) using both planimetry and 2D PC of the great vessels. Results: The mean tricuspid valve systolic excursion was 17.8 ± 2.5 mm. The 2D valve‐tracking PC net diastolic flow showed excellent correlation with SV by right‐ventricle planimetry (bias ± 1.96 SD = −0.2 ± 10.4 mL, intraclass correlation coefficient [ICC] = 0.92) and aortic PC (−1.0 ± 13.8 mL, ICC = 0.87). In comparison, static tricuspid valve 2D PC also showed a strong correlation but had greater bias (p = 0.01) versus the right‐ventricle SV (10.6 ± 16.1 mL, ICC = 0.61). In most (8 of 9) healthy subjects, trace regurgitation was measured at begin‐systole. In one patient, valve‐tracking PC displayed a high‐velocity jet (380 cm/s) with maximal velocity agreeing with echocardiography. Conclusion: Automated valve‐tracking 2D PC is a feasible route toward evaluation of tricuspid regurgitant velocities, potentially solving a major clinical challenge. [ABSTRACT FROM AUTHOR]

Neutron imaging has gained significant importance as a material characterisation technique and is particularly useful to visualise hydrogenous materials in objects opaque to other radiations. Fields of application include investigations of hydrogen in metals as well as metal corrosion, thanks to the fact that neutrons can penetrate metals better than e.g. X-rays and are highly sensitive to hydrogen. However, at interfaces refraction effects sometimes obscure the attenuation image, which is used for hydrogen quantification. Refraction, a differential phase effect, diverts the neutron beam away from the interface in the image leading to intensity gain and intensity loss regions, which are superimposed to the attenuation image, thus obscuring the interface region and hindering quantitative analyses of e.g. hydrogen content in the vicinity of the interface. For corresponding effects in X-ray imaging, a phase filter approach was developed and is generally based on transport-of-intensity considerations. Here, we compare such an approach, that has been adapted to neutrons, with another simulation-based assessment using the ray-tracing software McStas. The latter appears superior and promising for future extensions which enable fitting forward models via simulations in order to separate phase and attenuation effects and thus pave the way for overcoming quantitative limitations at refracting interfaces. [ABSTRACT FROM AUTHOR]

The work is devoted to the study of the influence of dimensional effects on the interaction of materials with X-ray radiation. In practice, there is often a need for defining minimum dimensions of an object that can be visualized using an X-ray device with certain characteristics. To address this, a proprietary method was devised for creating three-dimensional computer models of complex objects of free geometric shape, and computer simulations of X-ray diffraction on these objects were carried out within the framework of the Fresnel-Kirchhoff theory. The study of visibility conditions was carried out on a complex 3-component object at different "object-screen" distances (1.5 m, 0.25 m) and different object sizes (200 µm and less). The effective linear size of an irregularly shaped object is proposed to be estimated as the ratio of the diameter of a circle, whose area is equal to that of the object's image on the screen, to the magnification factor. Through these simulations, the effective diameters of individual components within the complex object were identified, along with the count of overlapping Fresnel zones for each component. It is shown that the quality of the image on the screen depends on the number of Fresnel zones intersecting the area of the geometric shadow of the sample during wavefront expansion. The more Fresnel zones fall into the area of the geometric shadow of the object under study, the higher the quality of the image on the screen. If less than one Fresnel zone exists within the geometric shadow of the sample, the object becomes undetectable. Based on information about the distance between the source and object, object and screen, and the radiation wavelength, we propose an analytical criterion to determine the minimum sizes of structural inhomogeneities that can be detected in the given materials using this research method. The results of this work hold potential utility for experimenters and developers of laboratory equipment. [ABSTRACT FROM AUTHOR]

Signal-to-noise ratio and spatial resolution are quantitatively analysed in the context of in-line (propagation based) X-ray phase-contrast imaging. It is known that free-space propagation of a coherent X-ray beam from the imaged object to the detector plane, followed by phase retrieval in accordance with Paganin's method, can increase the signal-to-noise in the resultant images without deteriorating the spatial resolution. This results in violation of the noise-resolution uncertainty principle and demonstrates `unreasonable' effectiveness of the method. On the other hand, when the process of free-space propagation is performed in software, using the detected intensity distribution in the object plane, it cannot reproduce the same effectiveness, due to the amplification of photon shot noise. Here, it is shown that the performance of Paganin's method is determined by just two dimensionless parameters: the Fresnel number and the ratio of the real decrement to the imaginary part of the refractive index of the imaged object. The relevant theoretical analysis is performed first, followed by computer simulations and then by a brief test using experimental images collected at a synchrotron beamline. More extensive experimental tests will be presented in the second part of this paper.

In normal-pressure hydrocephalus, disturbances in cerebrospinal fluid (CSF) circulation occur; therefore, understanding CSF dynamics is crucial. The two-dimensional phase-contrast (2D-PC) method, a common approach for visualizing CSF flow on MRI, often presents challenges owing to prominent vein signals and excessively high contrast, hindering the interpretation of morphological information. Therefore, we devised a new imaging method that utilizes T2-weighted high-signal intensification of the CSF and saturation pulses, without requiring specialized imaging sequences. This sequence utilized a T2-weighted single-shot fast spin-echo combined with multi-phase imaging synchronized with a pulse wave. Optimal imaging conditions (repetition time, presence/absence of fast recovery, and echo time) were determined using self-made contrast and single-plate phantoms to evaluate signal-to-noise ratio, contrast ratio, and spatial resolution. In certain clinical cases of hydrocephalus, confirming CSF flow using 2D-PC was challenging. However, our method enabled the visualization of CSF flow, proving to be useful in understanding the pathophysiology of hydrocephalus. [ABSTRACT FROM AUTHOR]

In problems of X-ray phase contrast in dynamic diffraction of a spherical wave, it is recommended to use a highly absorbing superlattice plate with a small period in the Laue geometry as an analyzer crystal. By choosing the value of the temperature gradient, it is proposed to focus all the satellites on the exit surface of the sample, guided by the lens formula for a crystalline medium. A method for recording reflexes without additional movement of the phase object is described. [ABSTRACT FROM AUTHOR]

Neutron differential phase-contrast imaging (DPCI) plays a pivotal role in analyzing magnetic domain structures and field gradients in materials, necessitating high-quality neutron absorption gratings for enhanced fringe contrast. Traditional fabrication techniques, typically filling gadolinium (Gd) or Gd-containing materials into the corresponding grating structures, face challenges in achieving optimal Gd filling ratios and thickness, limiting the neutron DPCI system's performance. This paper introduces an approach utilizing ultrasound-assisted filling method to introduce Gd particles into grating trenches with dense deposition, achieving an absorption grating period of 42 μ m. This method achieves an equivalent Gd thickness of 80.3 μ m, corresponding to the filling ratio of 53.53%, as confirmed by scanning electron microscopy and x-ray micro-imaging. The utilization of an ultrasound not only improves the Gd filling ratio, but also suggests potential scalability for large-area grating production, marking a significant advancement in neutron DPCI technology by providing high-quality components. [ABSTRACT FROM AUTHOR]

The glymphatic system is a system of specialized perivascular spaces in the brain that facilitates removal of toxic waste solutes from the brain. Evaluation of glymphatic system function by means of magnetic resonance imaging (MRI) has thus far been largely focused on rodents because of the limitations of intrathecal delivery of gadolinium‐based contrast agents to humans. This review discusses MRI methods that can be employed clinically for glymphatic‐related measurements intended for early diagnosis, prevention, and the treatment of various neurological conditions. Although glymphatic system‐based MRI research is in its early stages, recent studies have identified promising noninvasive MRI markers associated with glymphatic system alterations in neurological diseases. However, further optimization in data acquisition, validation, and modeling are needed to investigate the glymphatic system within the clinical setting. [ABSTRACT FROM AUTHOR]

Neurological disorders can manifest with altered neurofluid dynamics in different compartments of the central nervous system. These include alterations in cerebral blood flow, cerebrospinal fluid (CSF) flow, and tissue biomechanics. Noninvasive quantitative assessment of neurofluid flow and tissue motion is feasible with phase contrast magnetic resonance imaging (PC MRI). While two‐dimensional (2D) PC MRI is routinely utilized in research and clinical settings to assess flow dynamics through a single imaging slice, comprehensive neurofluid dynamic assessment can be limited or impractical. Recently, four‐dimensional (4D) flow MRI (or time‐resolved three‐dimensional PC with three‐directional velocity encoding) has emerged as a powerful extension of 2D PC, allowing for large volumetric coverage of fluid velocities at high spatiotemporal resolution within clinically reasonable scan times. Yet, most 4D flow studies have focused on blood flow imaging. Characterizing CSF flow dynamics with 4D flow (i.e., 4D CSF flow) is of high interest to understand normal brain and spine physiology, but also to study neurological disorders such as dysfunctional brain metabolite waste clearance, where CSF dynamics appear to play an important role. However, 4D CSF flow imaging is challenged by the long T1 time of CSF and slower velocities compared with blood flow, which can result in longer scan times from low flip angles and extended motion‐sensitive gradients, hindering clinical adoption. In this work, we review the state of 4D CSF flow MRI including challenges, novel solutions from current research and ongoing needs, examples of clinical and research applications, and discuss an outlook on the future of 4D CSF flow. [ABSTRACT FROM AUTHOR]

Signal‐to‐noise ratio and spatial resolution are quantitatively analysed in the context of in‐line (propagation based) X‐ray phase‐contrast imaging. It is known that free‐space propagation of a coherent X‐ray beam from the imaged object to the detector plane, followed by phase retrieval in accordance with Paganin's method, can increase the signal‐to‐noise in the resultant images without deteriorating the spatial resolution. This results in violation of the noise‐resolution uncertainty principle and demonstrates 'unreasonable' effectiveness of the method. On the other hand, when the process of free‐space propagation is performed in software, using the detected intensity distribution in the object plane, it cannot reproduce the same effectiveness, due to the amplification of photon shot noise. Here, it is shown that the performance of Paganin's method is determined by just two dimensionless parameters: the Fresnel number and the ratio of the real decrement to the imaginary part of the refractive index of the imaged object. The relevant theoretical analysis is performed first, followed by computer simulations and then by a brief test using experimental images collected at a synchrotron beamline. More extensive experimental tests will be presented in the second part of this paper. [ABSTRACT FROM AUTHOR]

The in situ study of fractal microstructure in nanocarbon polymers is an actual task for their application and for the improvement in their functional properties. This article presents a visualization of the bulk structural features of the composites using pulsed acoustic microscopy and synchrotron X-ray microtomography. This article presents details of fractal structure formation using carbon particles of different sizes and shapes—exfoliated graphite, carbon platelets and nanotubes. Individual structural elements of the composite, i.e., conglomerations of the particles in the air capsule as well as their distribution in the composite volume, were observed at the micro- and nanoscale. We have considered the influence of particle architecture on the fractal formation and elastic properties of the composite. Acoustic and X-ray imaging results were compared to validate the carbon agglomeration. [ABSTRACT FROM AUTHOR]

Purpose: To develop a highly‐accelerated, real‐time phase contrast (rtPC) MRI pulse sequence with 40 fps frame rate (25 ms effective temporal resolution). Methods: Highly‐accelerated golden‐angle radial sparse parallel (GRASP) with over regularization may result in temporal blurring, which in turn causes underestimation of peak velocity. Thus, we amplified GRASP performance by synergistically combining view‐sharing (VS) and k‐space weighted image contrast (KWIC) filtering. In 17 pediatric patients with congenital heart disease (CHD), the conventional GRASP and the proposed GRASP amplified by VS and KWIC (or GRASP + VS + KWIC) reconstruction for rtPC MRI were compared with respect to clinical standard PC MRI in measuring hemodynamic parameters (peak velocity, forward volume, backward volume, regurgitant fraction) at four locations (aortic valve, pulmonary valve, left and right pulmonary arteries). Results: The proposed reconstruction method (GRASP + VS + KWIC) achieved better effective spatial resolution (i.e., image sharpness) compared with conventional GRASP, ultimately reducing the underestimation of peak velocity from 17.4% to 6.4%. The hemodynamic metrics (peak velocity, volumes) were not significantly (p > 0.99) different between GRASP + VS + KWIC and clinical PC, whereas peak velocity was significantly (p < 0.007) lower for conventional GRASP. RtPC with GRASP + VS + KWIC also showed the ability to assess beat‐to‐beat variation and detect the highest peak among peaks. Conclusion: The synergistic combination of GRASP, VS, and KWIC achieves 25 ms effective temporal resolution (40 fps frame rate), while minimizing the underestimation of peak velocity compared with conventional GRASP. [ABSTRACT FROM AUTHOR]

The enamel of mammalian teeth is a highly mineralized tissue that must endure a lifetime of cyclic contact and is inspiring the development of next-generation engineering materials. Attempts to implement enamel-inspired structures in synthetic materials have had limited success, largely due to the absence of a detailed understanding of its microstructure. The present work used synchrotron phase-contrast microCT imaging to evaluate the three-dimensional microstructure of enamel from four mammals including Lion, Gray Wolf, Snow Leopard, and Black Bear. Quantitative results of image analysis revealed that the decussation pattern of enamel consists of discrete diazone (D) and parazone (P) bands of rods organized with stacking arrangement of D+/P/D-/P in all mammals evaluated; the D+ and D- refer to distinct diazone bands with juxtaposed rod orientations from the reference plane. Furthermore, the rod orientations in the bands can be described in terms of two principal angles, defined here as the pitch and yaw. While the pitch angle increases from the outer enamel to a maximum (up to ≈ 40°) near the dentin enamel junction, minimal spatial variations are observed in yaw across the enamel thickness. There are clear differences in the decussation parameters of enamel across species that are interpreted here with respect to the structural demands placed on their teeth. The rod pitch and band width of enamel are identified as important design parameters and appear to be correlated with the bite force quotient of the four mammals evaluated. The multi-functionality of tooth enamel requires both hardness and resistance to fracture, properties that are generally mutually exclusive. Ubiquitous to all mammalian teeth, the enamel is expected to have undergone adaptations in microstructure to accommodate the differences in diet, body size and bite force across animals. For the first time, we compare the complex three-dimensional microstructure of enamel from teeth of multiple mammalian species using synchrotron micro-computed tomography. The findings provide new understanding of the "design" of mammalian enamel microstructures, as well as how specific parameters associated with the decussation of rods appear to be engineered to modulate its fracture resistance. [Display omitted] [ABSTRACT FROM AUTHOR]

Purpose: Diastolic function evaluation requires estimates of early and late diastolic mitral filling velocities (E and A) and of mitral annulus tissue velocity (e′). We aimed to develop an MRI method for simultaneous all‐in‐one diastolic function evaluation in a single scan by generating a 2D phase‐contrast (PC) sequence with balanced steady‐state free precession (bSSFP) contrast (PC‐SSFP). E and A could then be measured with PC, and e′ estimated by valve tracking on the magnitude images, using an established deep learning framework. Methods: Our PC‐SSFP used in‐plane flow‐encoding, with zeroth and first moment nulling over each TR. For further acceleration, different k‐t principal component analysis (PCA) methods were investigated with both retrospective and prospective undersampling. PC‐SSFP was compared to separate balanced SSFP cine and PC‐gradient echo acquisitions in phantoms and in 10 healthy subjects. Results: Phantom experiments showed that PC‐SSFP measured accurate velocities compared to PC‐gradient echo (r = 0.98 for a range of pixel‐wise velocities −80 cm/s to 80 cm/s). In subjects, PC‐SSFP generated high SNR and myocardium‐blood contrast, and excellent agreement for E (limits of agreement [LOA] 0.8 ± 2.4 cm/s, r = 0.98), A (LOA 2.5 ± 4.1 cm/s, r = 0.97), and e′ (LOA 0.3 ± 2.6 cm/s, r = 1.00), versus the standard methods. The best k‐t PCA approach processed the complex difference data and substituted in raw k‐space data. With prospective k‐t PCA acceleration, higher frame rates were achieved (50 vs. 25 frames per second without k‐t PCA), yielding a 13% higher e′. Conclusion: The proposed PC‐SSFP method achieved all‐in‐one diastolic function evaluation. [ABSTRACT FROM AUTHOR]

X-ray phase-contrast imaging (XPCI) is a family of imaging techniques that makes contrast visible due to phase shifts in the sample. Phase-sensitive techniques can potentially be several orders of magnitude more sensitive than attenuation-based techniques, finding applications in a wide range of fields, from biomedicine to materials science. The accurate simulation of XPCI allows for the planning of imaging experiments, potentially reducing the need for costly synchrotron beam access to find suitable imaging parameters. It can also provide training data for recently proposed machine learning-based phase retrieval algorithms. The simulation of XPCI has classically been carried out using wave optics or ray optics approaches. However, these approaches have not been capable of simulating all the artifacts present in experimental images. The increased interest in dark-field imaging has also prompted the inclusion of scattering in XPCI simulation codes. Scattering is classically simulated using Monte Carlo particle transport codes. The combination of the two perspectives has proven not to be straightforward, and several methods have been proposed. We review the available literature on the simulation of XPCI with attention given to particular methods, including the scattering component, and discuss the possible future directions for the simulation of both wave and particle effects in XPCI. [ABSTRACT FROM AUTHOR]

Quantifying the effects of free breathing on cerebral venous flow is crucial for understanding cerebral circulation mechanisms and clinical applications. Unlike conventional cine phase-contrast MRI sequences (CINE-PC), real-time phase-contrast MRI sequences (RT-PC) can provide a continuous beat-to-beat flow signal that makes it possible to quantify the effect of breathing on cerebral venous flow. In this study, we examined 28 healthy human participants, comprising of 14 males and 14 females. Blood flows in the right/left internal jugular veins in the extracranial plane and the superior sagittal sinus (SSS) and straight sinus in the intercranial plane were quantified using CINE-PC and RT-PC. The first objective of this study was to determine the accuracy of RT-PC in quantifying cerebral venous flow, relative to CINE-PC. The second, and main objective, was to quantify the effect of free breathing on cerebral venous flow, using a time-domain multiparameter analysis method. Our results showed that RT-PC can accurately quantify cerebral venous flow with a 2 x 2 mm² spatial resolution and 75 ms/image time resolution. The mean flow rate, amplitude, stroke volume, and cardiac period of cerebral veins were significantly higher from the mid-end phase of expiration to the mid-end phase of inspiration. Breathing affected the mean flow rates in the jugular veins more than those in the SSS and straight sinus. Furthermore, the effects of free breathing on the flow rate of the left and right jugular veins were not synchronous. These new findings provide a useful reference for better understanding the mechanisms of cerebral circulation. [ABSTRACT FROM AUTHOR]

Cerebral blood flow (CBF) is an important hemodynamic parameter to evaluate brain health. It can be obtained quantitatively using medical imaging modalities such as magnetic resonance imaging and positron emission tomography (PET). Although CBF in adults has been widely studied and linked with cerebrovascular and neurodegenerative diseases, CBF data in healthy children are sparse due to the challenges in pediatric neuroimaging. An understanding of the factors affecting pediatric CBF and its normal range is crucial to determine the optimal CBF measuring techniques in pediatric neuroradiology. This review focuses on pediatric CBF studies using neuroimaging techniques in 32 articles including 2668 normal subjects ranging from birth to 18 years old. A systematic literature search was conducted in PubMed, Embase, and Scopus and reported following the preferred reporting items for systematic reviews and meta‐analyses (PRISMA). We identified factors (such as age, gender, mood, sedation, and fitness) that have significant effects on pediatric CBF quantification. We also investigated factors influencing the CBF measurements in infants. Based on this review, we recommend best practices to improve CBF measurements in pediatric neuroimaging. Level of Evidence: 1 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

Heart failure (HF) is a clinical syndrome with a wide variety of clinical presentations, pathophysiologies, and natural histories. HF is becoming more prevalent globally, thus increasing effects on healthcare systems. Cardiac magnetic resonance (CMR) imaging is a valuable tool for better understanding HF and its prognosis. The commonly used reference standard of CMR cine imaging provides accurate assessment of chamber size and function. Phase contrast imaging can be used to assess the degree of valvular regurgitation and complex flow patterns. Stress perfusion imaging can detect subtle areas of ischemia and microvascular dysfunction. Late gadolinium enhancement imaging aids in diagnosing causes of HF and guiding revascularization in ischemic cardiomyopathy. Supported by histological validation, T1 and T2 mapping provides non-invasive information on tissue characteristics in inflammatory and infiltrative cardiomyopathies. CMR also provides various techniques to measure strain in the atria and ventricles at high spatial and temporal resolution. CMR continues to serve as an important modality for the evaluation of HF. [ABSTRACT FROM AUTHOR]

High-resolution imaging in small animal models of neurologic disease is a technical challenge. In a pilot project, we have explored a non-destructive synchrotron imaging technique for the 3D visualization of intracerebral tissue transplants in a well-established small animal model of Huntington’s disease. Four adult female Sprague Dawley rats each received injections of 0.12 M quinolinic acid (QA) into two target positions in the left striatum, thus creating unilateral left-sided striatal lesions similar to those frequently seen in patients suffering from Huntington’s disease. One week after lesioning, the animals received transplants prepared from whole ganglionic eminences (wGEs) obtained from 13- to 14-day-old rat embryos. Of the four lesioned animals, three received transplants of GNP-loaded cells and one animal received a transplant of naïve cells, serving as control. Post-mortem synchrotron-based microCT was used to obtain images of the neurotransplants. The images obtained of GNP-loaded tissue transplants at the synchrotron corresponded in size and shape to the histological images of transplants developed from naïve cells. Thus, we conclude that non-destructive synchrotron imaging techniques such as phase-contrast imaging are suitable to obtain high-resolution images of GNP-loaded tissue transplants.

IntroductionSynchrotron-based propagation-based imaging (PBI) is ideally suited for lung imaging and has successfully been applied in a variety of in vivo small animal studies. Virtually all these experiments were tailored to achieve extremely high spatial resolution close to the alveolar level while delivering high x-ray doses that would not permit longitudinal studies. However, the main rationale for performing lung imaging studies in vivo in small animal models is the ability to follow disease progression or monitor treatment response in the same animal over time. Thus, an in vivo imaging strategy should ideally allow performing longitudinal studies.MethodsHere, we demonstrate our findings of using PBI-based planar and CT imaging with two different detectors—MÖNCH 0.3 direct conversion detector and a complementary metal-oxide-semiconductor (CMOS) detector (Photonics Science)—in an Ovalbumin induced experimental allergic airway disease mouse model in comparison with healthy controls. The mice were imaged free breathing under isoflurane anesthesia.ResultsAt x-ray dose levels below those once used by commercial small animal CT devices at similar spatial resolutions, we were able to resolve structural changes at a pixel size down to 25 μm and demonstrate the reduction in elastic recoil in the asthmatic mice in cinematic planar x-ray imaging with a frame rate of up to 100 fps.DiscussionThus, we believe that our approach will permit longitudinal small animal lung disease studies, closely following the mice over longer time spans.

ABSTRACT: Background: There is a growing interest in the development and application of mid-field (0.55T) for cardiovascular magnetic resonance (CMR), including flow imaging. However, aortic flow imaging at 0.55T has limited signal-to-noise ratio (SNR), especially in diastolic phases where there is reduced inflow-driven contrast for spoiled gradient recalled echo (GRE) sequences. The low SNR can limit the accuracy of flow and regurgitant fraction measurements. Methods: In this work, we developed a two-dimensional phase contrast (PC) acquisition with balanced steady-state free precession (bSSFP), termed PC-SSFP, for flow imaging and quantification at 0.55T. This PC-SSFP approach precisely nulls the zeroth and first gradient moments at both the echo time (TE) and repetition time, except for the flow-encoded acquisition, for which the first gradient moment at the TE is determined by the velocity encoding. Our proposed sequence was tested in both phantoms and in healthy volunteers (n = 11), to measure aortic flow. In volunteers, both a breath-hold (bh) and a free-breathing (fb) protocol, with averaging to increase SNR, were obtained. Total flow, peak flow, cardiac output, and SNR were compared for PC-SSFP and PC-GRE. Stroke volumes were also measured and compared to planimetry method. Results: In a phantom, SNR was significantly higher using PC-SSFP compared to PC-GRE (25.5 ± 9.6 vs 8.2 ± 2.9), and the velocity measurements agreed well (R = 1.00). In healthy subjects, for both bh and fb protocols, PC-SSFP measured accurate peak flow (fb: R = 0.99, bh: R = 0.96) and cardiac output (fb: R = 0.98, bh: R = 0.88), compared to PC-GRE, accurate stroke volume (fb: R = 0.94, bh: R = 0.97), compared to planimetry measurement, and offered constant high SNR (fb: 28 ± 9 vs 18 ± 6, bh: 24 ± 7 vs 11 ± 3) over the cardiac cycle in 11 subjects. Conclusion: PC-SSFP is a more reliable evaluation tool for aortic flow quantification, when compared to the conventional PC-GRE method at 0.55T, providing higher SNR, and thus potentially more accurate flows.

The method of X-ray phase contrast imaging has found wide application in coherent-synchrotron-radiation sources. In this study, this method is used in combination with X-ray diffraction topography to investigate structural defects and inhomogeneities in the volume of basal-faceted sapphire ribbons. The phase-contrast images of gas pores are analyzed in detail using computer simulations. X-ray topography methods are used to study the generation of dislocations by pores. The combination of methods provides information that is impossible to obtain using traditional optical microscopy. [ABSTRACT FROM AUTHOR]

There are several imaging modes in AFM, and the tapping mode is the most commonly used scanning mode. Tapping mode can acquire the height information and phase information of the sample surface, among which the phase information has more value, which can reflect the physical properties of the sample surface. In order to understand the phase imaging mechanism of AFM, this paper uses the vibration theory to derive the theoretical expression of phase, and finds that the excitation frequency will directly affect the phase contrast. Based on this, this paper finds, through theoretical and experimental analysis, that there exists an optimal excitation frequency that maximizes the phase contrast during the scanning process. These results are important for interpreting the phase image of AFM and thus optimizing the phase imaging in experiments. [ABSTRACT FROM AUTHOR]

Full-field X-ray nanoimaging is a widely used tool in a broad range of scientific areas. In particular, for low-absorbing biological or medical samples, phase contrast methods have to be considered. Three well established phase contrast methods at the nanoscale are transmission X-ray microscopy with Zernike phase contrast, near-field holography and near-field ptychography. The high spatial resolution, however, often comes with the drawback of a lower signal-to-noise ratio and significantly longer scan times, compared with microimaging. In order to tackle these challenges a single-photon-counting detector has been implemented at the nanoimaging endstation of the beamline P05 at PETRA III (DESY, Hamburg) operated by Helmholtz-Zentrum Hereon. Thanks to the long sample-to-detector distance available, spatial resolutions of below 100 nm were reached in all three presented nanoimaging techniques. This work shows that a single-photon-counting detector in combination with a long sample-to-detector distance allows one to increase the time resolution for in situ nanoimaging, while keeping a high signal-to-noise level.

Cell culture monitoring necessitates thorough attention for the continuous characterization of cultivated cells. Machine learning has recently emerged to engage in a process, such as a microscopy segmentation task; however, the trained data may not be comprehensive for other datasets. Most algorithms do not encompass a wide range of data attributes and require distinct system workflows. Thus, the main objective of the research is to propose a segmentation pipeline specifically for fibroblast cell images on phase contrast microscopy at different magnifications and to achieve reliable predictions during deployment. The research employs patch-based segmentation for predictions, with U-Net as the baseline architecture. The proposed segmentation pipeline demonstrated significant performance for the UNet-based network, achieving an IoU score above 0.7 for multiple magnifications, and provided predictions for cell confluency value with less than 3% error. The study also found that the proposed model could segment the fibroblast cells in under 10 seconds with the help of OpenVINO and Intel Compute Stick 2 on Raspberry Pi, with its optimal precision limited to approximately 80% cell confluency which is sufficient for real-world deployment as the cell culture is typically ready for passaging at the threshold.

High-resolution imaging in small animal models of neurologic disease is a technical challenge. In a pilot project, we have explored a non-destructive synchrotron imaging technique for the 3D visualization of intracerebral tissue transplants in a well-established small animal model of Huntington's disease. Four adult female Sprague Dawley rats each received injections of 0.12 M quinolinic acid (QA) into two target positions in the left striatum, thus creating unilateral left-sided striatal lesions similar to those frequently seen in patients suffering from Huntington's disease. One week after lesioning, the animals received transplants prepared from whole ganglionic eminences (wGEs) obtained from 13- to 14-day-old rat embryos. Of the four lesioned animals, three received transplants of GNP-loaded cells and one animal received a transplant of naïve cells, serving as control. Post-mortem synchrotron-based microCT was used to obtain images of the neurotransplants. The images obtained of GNP-loaded tissue transplants at the synchrotron corresponded in size and shape to the histological images of transplants developed from naïve cells. Thus, we conclude that non-destructive synchrotron imaging techniques such as phase-contrast imaging are suitable to obtain high-resolution images of GNP-loaded tissue transplants. [ABSTRACT FROM AUTHOR]

Achieving optimal design and precise control of the internal structure of laser-target materials are the primary objectives in various laser physics experiments, particularly in generating high flux photon and neutron beams. The study of low-density materials poses considerable challenges for X-ray analysis due to their high transparency and minimal contrast. In this study, to obtain clear visualization of foams with sparse structures, we used phase-contrast X-ray tomography, utilizing a high-quality monochromatic X-ray beam from the synchrotron radiation source PETRA-III at DESY. Employing phase-contrast algorithms, the 3D structure of a foam-suspended glass microsphere inside the plastic cylinder was reconstructed with a level of image quality sufficient to visualize uniformity, displacement, and surface roughness on both sides of the microsphere. The primary focus of this investigation was a CH plastic capillary including 10 mg/cc CHO foam with a glass microsphere positioned at the center. The results of this study demonstrate that phase-contrast X-ray tomography with coherent synchrotron radiation is an effective and valuable technique for the development of new laser targets containing structured low-density materials. [ABSTRACT FROM AUTHOR]

Purpose: Phellinus fastuosus (Lév.) S. (Hymenochaetaceae, Hymenochaetales, Agaricomycetes, Basidiomycota) is a member of wood-rotting polyporoid fungi that contains numerous metabolites reported with many medicinal properties and has been used in traditional medicine for the treatment of various diseases. Inspired by the medicinal properties of this polypore the present study on the antioxidant and antiproliferative potential of methanolic extract of Phellinus fastuosus using various in vitro assays was proposed. Methods: The extraction of the basidiocarp of Ph. fastuosus was done sequentially in hot water (Pfaq), methanol (Pfme) and ethyl acetate (Pfea) to obtain the respective extracts. The antioxidant potential of different extracts was examined with 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assay, Ferric ion reducing antioxidant power and Phosphomolybdate assay. The cytotoxicity activity was determined by using MTT assay in human epidermoid carcinoma cells (A431), human cervical cancer (HeLa cells), human osteosarcoma (MG-63) and normal epidermoid cells (L929). For the assessment of changes in cell morphology, and apoptotic induction in A431 cell line was further investigated using phase-contrast microscopy, Hoechst 33342 staining and AO/EtBr dual staining. Flow cytometry was used for the estimation of production of reactive oxygen species (ROS) andmitochondrial membrane potential (MMP). Results: Among all, Pfme extract showed effective free radical scavenging potential in DPPH assay, as compared to the other extracts. Therefore the Pmfe extract was further evaluated for the antiproliferative activity in A431, HeLa and MG-63 cell lines. This extract was very effective in A431 with GI50 (growth inhibitory dose 50%) value of 81.39 compared to its effect in HeLa and MG-63 cells with GI50 values of 173.47 and 191.53 μg/ml respectively. The Pfme extract was further investigated to explore its role in apoptosis induction in A431 cell line. Phase-contrast and fluorescence microscopic studies exhibited all the characteristics indicative of apoptosis, viz., shape change, cell shrinkage, cell rounding-off and nuclear condensation. To understand the cause of effectiveness of Pfme extract, HPLC analysis was carried out which showed the presence of different polyphenols. Conclusions: A critical examination of results highlighted that the Pmfe extract induced apoptosis in A431 cells via ROS-mediated apoptotic pathway which may be ascribed to the presence of polyphenols in it. [ABSTRACT FROM AUTHOR]

Precise morphological analysis of tumour tissue samples is crucial for accurate diagnosis and staging of colorectal cancer (CRC), but remains limited by the 2D nature of conventional histology. Our aim is to offer a 3D representation of tissue samples by means of X-ray-based imaging to facilitate the evaluation of clinically relevant features in cancer tissue, a process that is currently subject to various restrictions. In this study, we show that propagation-based synchrotron radiation-based free propagation phase-contrast microcomputed tomography (SRµCT) is suitable for the generation of 3D tumour volumes with 2-µm voxel size using standard formalin-fixed, paraffin-embedded tissue from CRC patients and provides sufficient contrast for virtual histology. We demonstrate that, using an existing registration pipeline, a 2D histologic haematoxylin–eosin slice can be placed in the context of the 3D µCT volume. The precisely registered histologic section can then be used as a “seed point” for the segmentation and depiction of major histologic features. This approach allows for a more comprehensive understanding of the organisation of the tumour in space with respect to other structures such as vessels, fat, and lymph nodes, and has the potential to improve patients’ prognostic outcomes.