GRASP reconstruction amplified with view-sharing and KWIC filtering reduces underestimation of peak velocity in highly-accelerated real-time phase-contrast MRI: A preliminary evaluation in pediatric patients with congenital heart disease

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.

Phase contrast micro-CT with adjustable in-slice spatial resolution at constant magnification

OBJECTIVE

To report on a micro computed tomography (micro-CT) system capable of x-ray phase contrast imaging and of increasing spatial resolution at constant magnification. Approach: The micro-CT system implements the edge illumination (EI) method, which relies on two absorbing masks with periodically spaced transmitting apertures in the beam path; these split the beam into an array of beamlets and provide sensitivity to the beamlets' directionality, i.e., refraction. In EI, spatial resolution depends on the width of the beamlets rather than on the source/detector point spread function (PSF), meaning that resolution can be increased by decreasing the mask apertures, without changing the source/detector PSF or the magnification. Main results: We have designed a dedicated mask featuring multiple bands with differently sized apertures and used this to demonstrate that resolution is a tuneable parameter in our system, by showing that increasingly small apertures deliver increasingly detailed images. Phase contrast images of bar pattern-based resolution phantom and a biological sample (a mouse embryo) were obtained at multiple resolutions. Significance: The new micro-CT system could find application in areas where phase contrast is already known to provide superior image quality, while the added tuneable resolution functionality could enable more sophisticated analyses in these applications, e.g., by scanning samples at multiple scales.

K-t PCA accelerated in-plane balanced steady-state free precession phase-contrast (PC-SSFP) for all-in-one diastolic function evaluation

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.

In vivo low-dose phase-contrast CT for quantification of functional and anatomical alterations in lungs of an experimental allergic airway disease mouse model

Introduction

Synchrotron-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.

Methods

Here, 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.

Results

At 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.

Discussion

Thus, we believe that our approach will permit longitudinal small animal lung disease studies, closely following the mice over longer time spans.

The Effects of Free Breathing on Cerebral Venous Flow: A Real-Time Phase Contrast MRI Study in Healthy Adults

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 × 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.

Measuring Quantitative Cerebral Blood Flow in Healthy Children: A Systematic Review of Neuroimaging Techniques

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.

Four-dimensional flow MRI for quantitative assessment of cerebrospinal fluid dynamics: Status and opportunities

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.

Quantitative two-dimensional phase-contrast magnetic resonance imaging characterization of lower extremity venous disease: venous reflux versus venous obstruction

Background

Lower extremity venous disease (LEVD) is a complex disorder, and determining the etiology of LEVD is paramount for treatment selection. Two-dimensional phase-contrast magnetic resonance imaging (2D PC-MRI) can provide an objective measure of hemodynamic status and may help differentiate between different etiologies of LEVD. A total of 271 participants, including 256 symptomatic patients with venous lower extremity disease and 15 healthy volunteers, were collected in this cohort study.

Methods

It is a single-center prospective observational study using 2D PC-MRI analysis to assess the hemodynamic characteristics of patients with LEVD among participants recruited between April 2017 and October 2021 at a tertiary hospital. The approval institutional review board number for this study were 201802137B0, 201901058B0, 202100938B0, and 202102344B0. Participants were classified as venous reflux (VR) and venous obstruction (VO) by standard ultrasonography. 2D PC-MRI by 1.5 T scanner revealed stroke volume (SV), forward flow volume (FFV), absolute stroke volume (ASV), mean flux (MF), velocity time integral (VTI), and mean velocity (MV) for each selected venous segments.

Results

2D PC-MRI assessed 167 diseased legs from the 116 VR patients [mean age ± standard deviation (SD): 57.9±12.8 years; 39 males] and 113 diseased legs from the 95 VO patients (mean age ± SD: 66.4±12.8 years; 42 males). 2D PC-MRI analysis demonstrated discrimination ability to differentiate from VR to VO [SV, FFV, ASV, MF, VTI, and MV in the various venous segments, respectively, P≤0.001; area under the curve (AUC) =62-68.8%, P≤0.001 by Mann-Whitney U test]. The ratio data (morbid limb to normal limb) in the same individual with single-leg disease revealed differences between VR and VO (SV, FFV, ASV, and MF in the various venous segments, respectively; P<0.05; AUC =60.2-68.7%, P≤0.05 by Mann-Whitney U test). The most favorable differentiating variables of ratios were FFV in the great saphenous veins [AUC =68.7%, 95% confidence interval (CI): 59.8-77.6%] and ASV in the external iliac veins (AUC =67.4%, 95% CI: 58.7-76.2%).

Conclusions

Quantitative 2D PC-MRI analysis is capable of differentiating VR from VO. It also provides an important diagnostic capability for preoperative evaluation.

3D Imaging of Striatal Transplants in a Small Animal Model of Huntington's Disease

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.

Human lung virtual histology by multi-scale x-ray phase-contrast computed tomography

As the central organ of the respiratory system, the human lung is responsible for supplying oxygen to the blood, which reaches the erythrocytes by diffusion through the alveolar walls and is then distributed throughout the body. By exploiting the difference in electron density detected by a phase shift in soft tissue, high-resolution X-ray phase-contrast computed tomography (XPCT) can resolve biological structures in a sub-μm range, shedding new light on the three-dimensional structure of the lungs, physiological functions and pathological mechanisms.&#xD;&#xD;This work presents both synchrotron and laboratory XPCT results of postmortem tissue from autopsies and biopsies embedded with various preparation protocols such as precision-cut lung slices, cryogenically fixed lung tissue, as well as paraffin and alcohol fixed tissue. The selection of pathological abnormalities includes channel of Lambert, bronchus-associated lymphoid tissue, alveolar capillary dysplasia with misalignment of pulmonary veins. Subsequently, quantification and visualization approaches are presented.&#xD;&#xD;The overall high image quality even of in-house XPCT scans for the case of FFPE biopsies can be exploited for a wide range of pulmonary pathologies and translated to dedicated and optimized instrumentation which could be operated in clinical setting. By using synchrotron radiation, contrast can be further increased to resolve sub-μm sized features down to the sub-cellular level. The results demonstrate that a wide range of preparation protocols including sample mounting in liquids can be used. &#xD;&#xD;With XPCT, poorly understood 3D structures can be identified in larger volume overview and subsequently studied in more detail at higher resolution. With the full 3D structure, the respective physiological functions of airways or vascular networks, and the different pathophysiologic mechanisms can be elucidated or at least underpinned with structural data. Moreover, synchrotron data can be used to validate laboratory protocols and provide ground truth for standardizing the method.&#xD;&#xD.

Hard X-ray full-field nanoimaging using a direct photon-counting detector

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.

Phase-contrast virtual chest radiography

Respiratory X-ray imaging enhanced by phase contrast has shown improved airway visualization in animal models. Limitations in current X-ray technology have nevertheless hindered clinical translation, leaving the potential clinical impact an open question. Here, we explore phase-contrast chest radiography in a realistic in silico framework. Specifically, we use preprocessed virtual patients to generate in silico chest radiographs by Fresnel-diffraction simulations of X-ray wave propagation. Following a reader study conducted with clinical radiologists, we predict that phase-contrast edge enhancement will have a negligible impact on improving solitary pulmonary nodule detection (6 to 20 mm). However, edge enhancement of bronchial walls visualizes small airways (< 2 mm), which are invisible in conventional radiography. Our results show that phase-contrast chest radiography could play a future role in observing small-airway obstruction (e.g., relevant for asthma or early-stage chronic obstructive pulmonary disease), which cannot be directly visualized using current clinical methods, thereby motivating the experimental development needed for clinical translation. Finally, we discuss quantitative requirements on distances and X-ray source/detector specifications for clinical implementation of phase-contrast chest radiography.

A versatile laboratory setup for high resolution X-ray phase contrast tomography and scintillator characterization

BACKGROUND

X-ray micro-tomography (μCT) is a powerful non-destructive 3D imaging method applied in many scientific fields. In combination with propagation-based phase-contrast, the method is suitable for samples with low absorption contrast. Phase contrast tomography has become available in the lab with the ongoing development of micro-focused tube sources, but it requires sensitive and high-resolution X-ray detectors. The development of novel scintillation detectors, particularly for microscopy, requires more flexibility than available in commercial tomography systems.

OBJECTIVE

We aim to develop a compact, flexible, and versatile μCT laboratory setup that combines absorption and phase contrast imaging as well as the option to use it for scintillator characterization. Here, we present details on the design and implementation of the setup.

METHODS

We used the setup for μCT in absorption and propagation-based phase-contrast mode, as well as to study a perovskite scintillator.

RESULTS

We show the 2D and 3D performance in absorption and phase contrast mode, as well as how the setup can be used for testing new scintillator materials in a realistic imaging environment. A spatial resolution of around 1.3μm is measured in 2D and 3D.

CONCLUSIONS

The setup meets the needs for common absorption μCT applications and offers increased contrast in phase contrast mode. The availability of a versatile laboratory μCT setup allows not only for easy access to tomographic measurements, but also enables a prompt monitoring and feedback beneficial for advances in scintillator fabrication.

Calibration of concomitant field offsets using phase contrast MRI for asymmetric gradient coils

PURPOSE

Asymmetric gradient coils introduce zeroth- and first-order concomitant field terms, in addition to higher-order terms common to both asymmetric and symmetric gradients. Salient to compensation strategies is the accurate calibration of the concomitant field spatial offset parameters for asymmetric coils. A method that allows for one-time calibration of the offset parameters is described.

THEORY AND METHODS

A modified phase contrast pulse sequence with single-sided bipolar flow encoding is proposed to calibrate the offsets for asymmetric, transverse gradient coils. By fitting the measured phase offsets to different gradient amplitudes, the spatial offsets were calculated by fitting the phase variation. This was used for calibrating real-time pre-emphasis compensation of the zeroth- and first-order concomitant fields.

RESULTS

Image quality improvement with the proposed corrections was demonstrated in phantom and healthy volunteers with non-Cartesian and Cartesian trajectory acquisitions. Concomitant field compensation using the calibrated offsets resulted in a residual phase error <3% at the highest gradient amplitude and demonstrated substantial reduction of image blur and slice position/selection artifacts.

CONCLUSIONS

The proposed implementation provides an accurate method for calibrating spatial offsets that can be used for real-time concomitant field compensation of zeroth and first-order terms, substantially reducing artifacts without retrospective correction or sequence specific waveform modifications.

A computer vision approach for analyzing label free leukocyte trafficking dynamics on a microvascular mimetic

High-content imaging techniques in conjunction with in vitro microphysiological systems (MPS) allow for novel explorations of physiological phenomena with a high degree of translational relevance due to the usage of human cell lines. MPS featuring ultrathin and nanoporous silicon nitride membranes (µSiM) have been utilized in the past to facilitate high magnification phase contrast microscopy recordings of leukocyte trafficking events in a living mimetic of the human vascular microenvironment. Notably, the imaging plane can be set directly at the endothelial interface in a µSiM device, resulting in a high-resolution capture of an endothelial cell (EC) and leukocyte coculture reacting to different stimulatory conditions. The abundance of data generated from recording observations at this interface can be used to elucidate disease mechanisms related to vascular barrier dysfunction, such as sepsis. The appearance of leukocytes in these recordings is dynamic, changing in character, location and time. Consequently, conventional image processing techniques are incapable of extracting the spatiotemporal profiles and bulk statistics of numerous leukocytes responding to a disease state, necessitating labor-intensive manual processing, a significant limitation of this approach. Here we describe a machine learning pipeline that uses a semantic segmentation algorithm and classification script that, in combination, is capable of automated and label-free leukocyte trafficking analysis in a coculture mimetic. The developed computational toolset has demonstrable parity with manually tabulated datasets when characterizing leukocyte spatiotemporal behavior, is computationally efficient and capable of managing large imaging datasets in a semi-automated manner.

Quantitative cerebrovascular reactivity MRI in mice using acetazolamide challenge

PURPOSE

To develop a quantitative MRI method to estimate cerebrovascular reactivity (CVR) in mice.

METHODS

We described an MRI procedure to measure cerebral vasodilatory response to acetazolamide (ACZ), a vasoactive agent previously used in human clinical imaging. Vascular response was determined by cerebral blood flow (CBF) measured with phase-contrast or pseudo-continuous arterial spin labeling MRI. Vasodilatory input intensity was determined by plasma ACZ level using high-performance liquid chromatography. We verified the source of the CVR MRI signal by comparing ACZ injection to phosphate-buffered saline injection and noninjection experiments. Dose dependence and feasibility of regional CVR measurement were also investigated.

RESULTS

Cerebral blood flow revealed an exponential increase following intravenous ACZ injection, with a time constant of 1.62 min. In contrast, phosphate-buffered saline or noninjection exhibited a slow linear CBF increase, consistent with a gradual accumulation of anesthetic agent, isoflurane, used in this study. When comparing different ACZ doses, injections of 30, 60, 120, and 180 mg/kg yielded a linear increase in plasma ACZ concentration (p < 0.0001). On the other hand, CBF changes under these doses were not different from each other (p = 0.50). The pseudo-continuous arterial spin labeling MRI with multiple postlabeling delays revealed similar vascular responses at different postlabeling delay values. There was a regional difference in CVR (p = 0.005), with isocortex (0.81 ± 0.17%/[μg/ml]) showing higher CVR than deep-brain regions. Mice receiving multiple ACZ injections lived for a minimum of 6 months after the study without noticeable aberrant behavior or appearance.

CONCLUSIONS

We demonstrated the proof-of-principle of a new quantitative CVR mapping technique in mice.

Accelerated two-dimensional phase-contrast for cardiovascular MRI using deep learning-based reconstruction with complex difference estimation

PURPOSE

To develop and validate a deep learning-based reconstruction framework for highly accelerated two-dimensional (2D) phase contrast (PC-MRI) data with accurate and precise quantitative measurements.

METHODS

We propose a modified DL-ESPIRiT reconstruction framework for 2D PC-MRI, comprised of an unrolled neural network architecture with a Complex Difference estimation (CD-DL). CD-DL was trained on 155 fully sampled 2D PC-MRI pediatric clinical datasets. The fully sampled data ( n = 29 $$ n=29 $$ ) was retrospectively undersampled (6-11 × $$ \times $$ ) and reconstructed using CD-DL and a parallel imaging and compressed sensing method (PICS). Measurements of peak velocity and total flow were compared to determine the highest acceleration rate that provided accuracy and precision within ± 5 % $$ \pm 5\% $$ . Feasibility of CD-DL was demonstrated on prospectively undersampled datasets acquired in pediatric clinical patients ( n = 5 $$ n=5 $$ ) and compared to traditional parallel imaging (PI) and PICS.

RESULTS

The retrospective evaluation showed that 9 × $$ \times $$ accelerated 2D PC-MRI images reconstructed with CD-DL provided accuracy and precision (bias, [95 % $$ \% $$ confidence intervals]) within ± 5 % $$ \pm 5\% $$ . CD-DL showed higher accuracy and precision compared to PICS for measurements of peak velocity (2.8 % $$ \% $$ [ - 2 . 9 $$ -2.9 $$ , 4.5] vs. 3.9 % $$ \% $$ [ - 11 . 0 $$ -11.0 $$ , 4.9]) and total flow (1.8 % $$ \% $$ [ - 3 . 9 $$ -3.9 $$ , 3.4] vs. 2.9 % $$ \% $$ [ - 7 . 1 $$ -7.1 $$ , 6.9]). The prospective feasibility study showed that CD-DL provided higher accuracy and precision than PICS for measurements of peak velocity and total flow.

CONCLUSION

In a retrospective evaluation, CD-DL produced quantitative measurements of 2D PC-MRI peak velocity and total flow with ≤ 5 % $$ \le 5\% $$ error in both accuracy and precision for up to 9 × $$ \times $$ acceleration. Clinical feasibility was demonstrated using a prospective clinical deployment of our 8 × $$ \times $$ undersampled acquisition and CD-DL reconstruction in a cohort of pediatric patients.

Machine-Learning-Aided Quantification of Area Coverage of Adherent Cells from Phase-Contrast Images

The advances in machine learning (ML) software availability, efficiency, and friendliness, combined with the increase in the computation power of personal computers, are harnessed to rapidly and (relatively) effortlessly analyze time-lapse image series of adherent cell cultures, taken with phase-contrast microscopy (PCM). Since PCM is arguably the most widely used technique to visualize adherent cells in a label-free, noninvasive, and nondisruptive manner, the ability to easily extract quantitative information on the area covered by cells, should provide a valuable tool for investigation. We demonstrate two cases, in one we monitor the shrinking of cells in response to a toxicant, and in the second we measure the proliferation curve of mesenchymal stem cells (MSCs).

Time-lapse imaging using dual-color coded quantitative differential phase contrast microscopy

SIGNIFICANCE

Quantitative differential phase contrast (qDPC) microscopy enhances phase contrast by asymmetric illumination using partially coherent light and multiple intensity measurements. However, for live cell imaging, motion artifacts and image acquisition time are important issues. For live cell imaging, a large number of intensity measurements can limit the imaging quality and speed. The minimum number of intensity measurements in qDPC can greatly enhance performance for live imaging.

AIM

To obtain high-contrast, isotropic qDPC images with two intensity measurements and perform time-lapse imaging of biological samples.

APPROACH

Based on the color-coded design, a dual-color linear-gradient pupil is proposed to achieve isotropic phase contrast response with two intensity measurements. In our method, the purpose of designing a dual-color coded pupil is twofold: first, to obtain a linear amplitude gradient for asymmetric illumination, which is required to get a circular symmetry of transfer function, and second, to reduce the required number of frames for phase retrieval.

RESULTS

To demonstrate the imaging performance of our system, standard microlens arrays were used as samples. We performed time-lapse quantitative phase imaging of rat astrocytes under a low-oxygen environment. Detailed morphology and dynamic changes such as the apoptosis process and migration of cells were observed.

CONCLUSIONS

It is shown that dual-color linear-gradient pupils in qDPC can outperform half-circle and vortex pupils, and isotropic phase transfer function can be achieved with only two-axis measurements. The reduced number of frames helps in achieving faster imaging speed as compared to the typical qDPC system. The imaging performance of our system is evaluated by time-lapse imaging of rat astrocytes. Different morphological changes in cells during their life cycle were observed in terms of quantitative phase change values.

Evaluation of Cardiac- and Respiratory-driven Cerebrospinal Fluid Motions by Applying the S-transform to Steady-state Free Precession Phase Contrast Imaging

PURPOSE

To extract the status of hydrocephalus and other cerebrospinal fluid (CSF)-related diseases, a technique to characterize the cardiac- and respiratory-driven CSF motions separately under free breathing was developed. This technique is based on steady-state free precession phase contrast (SSFP-PC) imaging in combination with a Stockwell transform (S-transform).

METHODS

2D SSFP-PC at 3 T was applied to measure the CSF velocity in the caudal-cranial direction within a sagittal slice at the midline (N = 3) under 6-, 10-, and 16-s respiratory cycles and free breathing. The frequency-dependent window width of the S-transform was controlled by a particular scaling factor, which then converted the CSF velocity waveform into a spectrogram. Based on the frequency bands of the cardiac pulsation and respiration, as determined by the electrocardiogram (ECG) and respirator pressure sensors, Gaussian bandpass filters were applied to the CSF spectrogram to extract the time-domain cardiac- and respiratory-driven waveforms.

RESULTS

The cardiac-driven CSF velocity component appeared in the spectrogram clearly under all respiratory conditions. The respiratory-driven velocity under the controlled respiratory cycles was observed as constant frequency signals, compared to a time-varying frequency signal under free breathing. When the widow width was optimized using the scale factor, the temporal change in the respiratory-driven CSF component was even more apparent under free breathing.

CONCLUSION

Velocity amplitude variations and transient frequency changes of both cardiac- and respiratory-driven components were successfully characterized. These findings indicated that the proposed technique is useful for evaluating CSF motions driven by different cyclic forces.

Problems with Evaluation of Micro-Pore Size in Silicon Carbide Using Synchrotron X-ray Phase Contrast Imaging

We report near- and far-field computer simulations of synchrotron X-ray phase-contrast images using a micropipe in a SiC crystal as a model system. Experimental images illustrate the theoretical results. The properties of nearly perfect single crystals of silicon carbide are strongly affected by μm-sized pores even if their distribution in a crystal bulk is sparse. A non-destructive technique to reveal the pores is in-line phase-contrast imaging with synchrotron radiation. A quantitative approach to evaluating pore sizes is the use of computer simulations of phase-contrast images. It was found that near-field phase-contrast images are formed at very short distances behind a sample. We estimated these distances for tiny pores. The Fresnel zones did not provide any information on the pore size in the far-field, but a contrast value within the first Fresnel zone could be used for simulations. Finally, general problems in evaluating a micro-pore size via image analysis are discussed.

Treatment decision in a 4-year-old-boy with left ventricular outpouching after advanced hemodynamical flow evaluation with 4Dflow CMR: A case report

BACKGROUND

The present study presents a diagnostic course for the characterization of a congenital left ventricular outpouching (LVO) in a 4-year-old boy with severe neonatal heart failure, evaluating the added value of cardiac magnetic resonance (CMR) 4Dflow.

CASE PRESENTATION

A boy, born at full term, presented with heart failure immediately after birth. Echocardiography showed dilated left ventricle with poor function and LVO was initially interpreted as an aneurysm. No infection, inflammation, or other cause for heart failure was found. With intensive medical treatment, the heart function returned to normal, and eventually, all medication was terminated. At follow-up, surgical treatment of the LVO was discussed but after CMR 4Dflow, a thorough evaluation of the function of the left ventricle as well as the LVO was possible and the LVO was determined a double-chambered left ventricle with a good prognosis.

CONCLUSIONS

The present case demonstrates the clinical usability of CMR 4Dflow for improved decision-making and risk assessment, revealing advanced hemodynamic flow patterns with no need for operation.

Quantitative time-of-flight MR angiography for simultaneous luminal and hemodynamic evaluation of the intracranial arteries

PURPOSE

To report a quantitative time-of-flight (qTOF) MRA technique for simultaneous luminal and hemodynamic evaluation of the intracranial arteries.

METHODS

Implemented using a thin overlapping slab 3D stack-of-stars based 3-echo FLASH readout, qTOF was tested in a flow phantom and for imaging the intracranial arteries of 10 human subjects at 3 Tesla. Display of the intracranial arteries with qTOF was compared to resolution-matched and scan time-matched standard Cartesian 3D time-of-flight (TOF) MRA, whereas quantification of mean blood flow velocity with qTOF, done using a computer vision-based inter-echo image analysis procedure, was compared to 3D phase contrast MRA. Arterial-to-background contrast-to-noise ratio was measured, and intraclass correlation coefficient was used to evaluate agreement of flow velocities.

RESULTS

For resolution-matched protocols of similar scan time, qTOF portrayed the intracranial arteries with good morphological correlation with standard Cartesian TOF, and both techniques provided superior contrast-to-noise ratio and arterial delineation compared to phase contrast (20.6 ± 3.0 and 37.8 ± 8.7 vs. 11.5 ± 2.2, P < .001, both comparisons). With respect to phase contrast, qTOF showed excellent agreement for measuring mean flow velocity in the flow phantom (intraclass correlation coefficient = 0.981, P < .001) and good agreement in the intracranial arteries (intraclass correlation coefficient = 0.700, P < .001). Stack-of-stars data sampling used with qTOF eliminated oblique in-plane flow misregistration artifacts that were seen with standard Cartesian TOF.

CONCLUSION

qTOF is a new 3D MRA technique for simultaneous luminal and hemodynamic evaluation of the intracranial arteries that provides significantly greater contrast-to-noise ratio efficiency than phase contrast and eliminates misregistration artifacts from oblique in-plane blood flow that occur with standard 3D TOF.

Simultaneous 3D-TOF angiography and 4D-flow MRI with enhanced flow signal using multiple overlapping thin slab acquisition and magnetization transfer

PURPOSE

To investigate the fusion of 3D time-of-flight principles into 4D-flow MRI to enhance vessel contrast and signal without an exogenous contrast agent, enabling simultaneous in-flow based angiograms.

METHODS

A 4D-flow MRI technique was developed consisting of multiple overlapping slabs with intermittent magnetization transfer preparation. The scan time penalty associated with multiple slab acquisitions was mitigated by using undersampled distributed spiral trajectories and compressed sensing reconstruction. A flow phantom was used to characterize in-flow enhancement, velocity noise improvement, and flow rate measurements against the single-slab 4D-flow MRI. In a patient-volunteer cohort (n = 15), magnitude-based angiograms were radiologically evaluated against 3D time-of-flight, and velocity measurements were compared pixel-wise against single-slab and contrast-enhanced 4D-flow MRI.

RESULTS

Multiple-slab acquisitions, together with magnetization transfer preparation, substantially improved vessel signal, contrast, and vessel conspicuity in magnitude angiograms. Both clinical 3D time-of-flight and the proposed technique produced equivalent vessel depictions with no statistically significant difference (p < .1). Both techniques also produced clear depictions of brain aneurysms in all patients; however, very small vessels tended to show reduced conspicuity in the proposed technique. Velocity measurements agreed with contrast-enhanced and single-slab scans with high correlations (R² = 0.941-0.974) and agreements (slopes = 0.994-1.071). Slab boundary and magnetization transfer-related artifacts were not observed in velocity measurements, and velocity noise was reduced with in-flow enhancement over single-slab scans (phantom).

CONCLUSION

The vessel signal and contrast can be improved in 4D-flow MRI without exogenous contrast agents by utilizing in-flow enhancement, efficient sampling, and compressed sensing. The in-flow enhancement also enables simultaneous 3D time-of-flight angiograms useful for flow quantification and diagnosis.

Before and after Endovascular Aortic Repair in the Same Patients with Aortic Dissection: A Cohort Study of Four-Dimensional Phase-Contrast Magnetic Resonance Imaging

(1) Background: We used four-dimensional phase-contrast magnetic resonance imaging (4D PC-MRI) to evaluate the impact of an endovascular aortic repair (TEVAR) on aortic dissection. (2) Methods: A total of 10 patients received 4D PC-MRI on a 1.5-T MR both before and after TEVAR. (3) Results: The aortas were repaired with either a GORE TAG Stent (Gore Medical; n = 7) or Zenith Dissection Endovascular Stent (Cook Medical; n = 3). TEVAR increased the forward flow volume of the true lumen (TL) (at the abdominal aorta, p = 0.047). TEVAR also reduced the regurgitant fraction in the TL at the descending aorta but increased it in the false lumen (FL). After TEVAR, the stroke distance increased in the TL (at descending and abdominal aorta, p = 0.018 and 0.015), indicating more effective blood transport per heartbeat. Post-stenting quantitative flow revealed that the reductions in stroke volume, backward flow volume, and absolute stroke volume were greater when covered stents were used than when bare stents were used in the FL of the descending aorta. Bare stents had a higher backward flow volume than covered stents did. (4) Conclusions: TEVAR increased the stroke volume in the TL and increased the regurgitant fraction in the FL in patients with aortic dissection.

Brain metabolism in tau and amyloid mouse models of Alzheimer's disease: An MRI study

Alzheimer's disease (AD) is the leading cause of cognitive impairment and dementia in elderly individuals. According to the current biomarker framework for "unbiased descriptive classification", biomarkers of neurodegeneration, "N", constitute a critical component in the tri-category "A/T/N" system. Current biomarkers of neurodegeneration suffer from potential drawbacks such as requiring invasive lumbar puncture, involving ionizing radiation, or representing a late, irreversible marker. Recent human studies have suggested that reduced brain oxygen metabolism may be a new functional marker of neurodegeneration in AD, but the heterogeneity and the presence of mixed pathology in human patients did not allow a full understanding of the role of oxygen extraction and metabolism in AD. In this report, global brain oxygen metabolism and related physiological parameters were studied in two AD mouse models with relatively pure pathology, using advanced MRI techniques including T2 -relaxation-under-spin-tagging (TRUST) and phase contrast (PC) MRI. Additionally, regional cerebral blood flow (CBF) was determined with pseudocontinuous arterial spin labeling. Reduced global oxygen extraction fraction (by -18.7%, p = 0.008), unit-mass cerebral metabolic rate of oxygen (CMRO2 ) (by -17.4%, p = 0.04) and total CMRO2 (by -30.8%, p < 0.001) were observed in Tau4RΔK mice-referred to as the tau AD model-which manifested pronounced neurodegeneration, as measured by diminished brain volume (by -15.2%, p < 0.001). Global and regional CBF in these mice were not different from those of wild-type mice (p > 0.05), suggesting normal vascular function. By contrast, in B6;SJL-Tg [APPSWE]2576Kha (APP) mice-referred to as the amyloid AD model-no brain volume reduction, as well as relatively intact brain oxygen extraction and metabolism, were found (p > 0.05). Consistent with the imaging data, behavioral measures of walking distance were impaired in Tau4RΔK mice (p = 0.004), but not in APP mice (p = 0.88). Collectively, these findings support the hypothesis that noninvasive MRI measurement of brain oxygen metabolism may be a promising biomarker of neurodegeneration in AD.

Bias and Precision in Magnetic Resonance Imaging-Based Estimates of Renal Blood Flow: Assessment by Triangulation

BACKGROUND

Renal blood flow (RBF) can be measured with dynamic contrast enhanced-MRI (DCE-MRI) and arterial spin labeling (ASL). Unfortunately, individual estimates from both methods vary and reference-standard methods are not available. A potential solution is to include a third, arbitrating MRI method in the comparison.

PURPOSE

To compare RBF estimates between ASL, DCE, and phase contrast (PC)-MRI.

STUDY TYPE

Prospective.

POPULATION

Twenty-five patients with type-2 diabetes (36% female) and five healthy volunteers (HV, 80% female).

FIELD STRENGTH/SEQUENCES

A 3 T; gradient-echo 2D-DCE, pseudo-continuous ASL (pCASL) and cine 2D-PC.

ASSESSMENT

ASL, DCE, and PC were acquired once in all patients. ASL and PC were acquired four times in each HV. RBF was estimated and split-RBF was derived as (right kidney RBF)/total RBF. Repeatability error (RE) was calculated for each HV, RE = 1.96 × SD, where SD is the standard deviation of repeat scans.

STATISTICAL TESTS

Paired t-tests and one-way analysis of variance (ANOVA) were used for statistical analysis. The 95% confidence interval (CI) for difference between ASL/PC and DCE/PC was assessed using two-sample F-test for variances. Statistical significance level was P < 0.05. Influential outliers were assessed with Cook's distance (D_i  > 1) and results with outliers removed were presented.

RESULTS

In patients, the mean RBF (mL/min/1.73m² ) was 618 ± 62 (PC), 526 ± 91 (ASL), and 569 ± 110 (DCE). Differences between measurements were not significant (P = 0.28). Intrasubject agreement was poor for RBF with limits-of-agreement (mL/min/1.73m² ) [-687, 772] DCE-ASL, [-482, 580] PC-DCE, and [-277, 460] PC-ASL. The difference PC-ASL was significantly smaller than PC-DCE, but this was driven by a single-DCE outlier (P = 0.31, after removing outlier). The difference in split-RBF was comparatively small. In HVs, mean RE (±95% CI; mL/min/1.73 m² ) was significantly smaller for PC (79 ± 41) than for ASL (241 ± 85).

CONCLUSIONS

ASL, DCE, and PC RBF show poor agreement in individual subjects but agree well on average. Triangulation with PC suggests that the accuracy of ASL and DCE is comparable.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 2.

Imaging with Coherent X-rays: From the Early Synchrotron Tests to SYNAPSE

The high longitudinal and lateral coherence of synchrotron X-rays sources radically transformed radiography. Before them, the image contrast was almost only based on absorption. Coherent synchrotron sources transformed radiography into a multi-faceted tool that can extract information also from "phase" effects. Here, we report a very simple description of the new techniques, presenting them to potential new users without requiring a sophisticated background in advanced physics. We then illustrate the impact of such techniques with a number of examples. Finally, we present the international collaboration SYNAPSE (Synchrotrons for Neuroscience-an Asia-Pacific Strategic Enterprise), which targets the use of phase-contrast radiography to map one full human brain in a few years.

Motion artifacts assessment and correction using optical tracking in synchrotron radiation breast CT

Purpose

The SYRMA‐3D collaboration is setting up a breast computed tomography (bCT) clinical program at the Elettra synchrotron radiation facility in Trieste, Italy. Unlike the few dedicated scanners available at hospitals, synchrotron radiation bCT requires the patient's rotation, which in turn implies a long scan duration (from tens of seconds to few minutes). At the same time, it allows the achievement of high spatial resolution. These features make synchrotron radiation bCT prone to motion artifacts. This article aims at assessing and compensating for motion artifacts through an optical tracking approach.

Methods

In this study, patients’ movements due to breathing have been first assessed on seven volunteers and then simulated during the CT scans of a breast phantom and a surgical specimen, by adding a periodic oscillatory motion (constant speed, 1 mm amplitude, 12 cycles/minute). CT scans were carried out at 28 keV with a mean glandular dose of 5 mGy. Motion artifacts were evaluated and a correction algorithm based on the optical tracking of fiducial marks was introduced. A quantitative analysis based on the structural similarity (SSIM) index and the normalized mean square error (nMSE) was performed on the reconstructed CT images.

Results

CT images reconstructed through the optical tracking procedure were found to be as good as the motionless reference image. Moreover, the analysis of SSIM and nMSE demonstrated that an uncorrected motion of the order of the system's point spread function (around 0.1 mm in the present case) can be tolerated.

Conclusions

Results suggest that a motion correction procedure based on an optical tracking system would be beneficial in synchrotron radiation bCT.

PyPhase - a Python package for X-ray phase imaging

X-ray propagation-based imaging techniques are well established at synchrotron radiation and laboratory sources. However, most reconstruction algorithms for such image modalities, also known as phase-retrieval algorithms, have been developed specifically for one instrument by and for experts, making the development and diffusion of such techniques difficult. Here, PyPhase, a free and open-source package for propagation-based near-field phase reconstructions, which is distributed under the CeCILL license, is presented. PyPhase implements some of the most popular phase-retrieval algorithms in a highly modular framework supporting its deployment on large-scale computing facilities. This makes the integration, the development of new phase-retrieval algorithms, and the deployment on different computing infrastructures straightforward. Its capabilities and simplicity are presented by application to data acquired at the synchrotron source MAX IV (Lund, Sweden).

Technical Note: Practical implementation strategies of cycloidal computed tomography

PURPOSE

Cycloidal computed tomography is a novel imaging concept which combines a highly structured x-ray beam, offset lateral under-sampling, and mathematical data recovery to obtain high-resolution images efficiently and flexibly, even with relatively large source focal spots and detector pixels. The method reduces scanning time and, potentially, delivered dose compared to other sampling schemes. This study aims to present and discuss several implementation strategies for cycloidal computed tomography (CT) in order to increase its ease of use and facilitate uptake within the imaging community.

METHODS

The different implementation strategies presented are step-and-shoot, continuous unidirectional, continuous back-and-forth, and continuous pixel-wise scanning. In step-and-shoot scans the sample remains stationary while frames are acquired, whereas in all other cases the sample moves through the scanner continuously. The difference between the continuous approaches is the trajectory by which the sample moves within the field of view.

RESULTS

All four implementation strategies are compatible with a standard table-top x-ray setup. With the experimental setup applied here, step-and-shoot acquisitions yield the best spatial resolution (around 30 µm), but are the most time-consuming (1.4 h). Continuous unidirectional and back-and-forth images have resolution between 30 and 40 µm, and are faster (35 min). Continuous pixel-wise images are equally time-efficient, although technical challenges caused a small loss in image quality with a resolution of about 50 µm.

CONCLUSION

The authors show that cycloidal CT can be implemented in a variety of ways with high quality results. They believe this posits cycloidal CT as a powerful imaging alternative to more time-consuming and less flexible methods in the field.

PUMA - An open-source 3D-printed direct vision microscope with augmented reality and spatial light modulator functions

3D-printed microscopes are a topical emerging field in the literature. However most microscopes presented to date are quite novel re-imaginings of the microscope's mechanical design and they are either solely dependent on, or primarily geared towards, camera-based observations rather than ergonomic direct vision screening through an ocular lens. The reliance on camera, computer and monitor for observation introduces a compromise between portability, cost and the quality of an instant wide field of view. In this report, I introduce the Portable Upgradeable Modular and Affordable (PUMA) microscope which is an open-source 3D-printed multimodality microscope that employs a traditional upright design for ease of human direct visual observations and slide screening. PUMA uses standard RMS or C-mount objectives, with a tube length 160 mm, 170 mm or infinity and wide field high eye point ocular lenses. PUMA can use simple mirror-based illumination or can be configured to a full Köhler system with Abbe condenser for high numerical aperture observations including oil immersion. PUMA also has advanced digital/optical imaging features such as a digital spatial light modulator and - unique to any 3D printed microscope to date - an augmented reality heads-up display for interactive calibrated measurements. Digital camera imaging can also be used with PUMA - in fact PUMA can take up to three separate digital cameras simultaneously. PUMA can also function as a direct vision multi-header microscope for teaching or discussion. The illumination system is also modular and includes transillumination, epi-illumination, fluorescence, polarisation, dark ground and also Schlieren-based phase contrast and other Fourier optics filtering modalities. All these advanced features are available through an on-board, battery operated, microprocessor so no mains supply, smartphone, network connection, PC or external monitor are required making PUMA a truly portable system suitable for remote field work.

Comparison of microstructural imaging of the root canal isthmus using propagation-based X-ray phase-contrast and absorption micro-computed tomography

Clear and complete microstructural imaging of the root canal isthmus is an important part of pathological investigations in research and clinical practice. X-ray micro-computed tomography (μCT) is a widely used non-destructive imaging technique, which allows for distortion-free three-dimensional (3D) visualisation. While absorption μCT typically has poor contrast resolution for observing the root canal isthmus, especially for weak-absorbing tissues, propagation-based X-ray phase-contrast imaging (PBI) is a powerful imaging method, which in its combination with μCT (PB-PCμCT) enables high-resolution and high-contrast microstructural imaging of the weak-absorbing tissues in samples. To investigate the feasibility and ability of PB-PCμCT in microstructural imaging of the root canal isthmus, conventional absorption μCT and PB-PCμCT experiments were performed. The two-dimensional (2D) and 3D comparison results demonstrated that, compared to absorption μCT, PB-PCμCT has the ability to image the root canal isthmus more clearly and completely, and thus, it has great potential to serve as a valuable tool for biomedical and preclinical studies on the root canal isthmus.

DiSpect: Displacement spectrum imaging of flow and tissue perfusion using spin-labeling and stimulated echoes

PURPOSE

We propose a new method, displacement spectrum (DiSpect) imaging, for probing in vivo complex tissue dynamics such as motion, flow, diffusion, and perfusion. Based on stimulated echoes and image phase, our flexible approach enables observations of the spin dynamics over short (milliseconds) to long (seconds) evolution times.

METHODS

The DiSpect method is a Fourier-encoded variant of displacement encoding with stimulated echoes, which encodes bulk displacement of spins that occurs between tagging and imaging in the image phase. However, this method fails to capture partial volume effects as well as blood flow. The DiSpect variant mitigates this by performing multiple scans with increasing displacement-encoding steps. Fourier analysis can then resolve the multidimensional spectrum of displacements that spins exhibit over the mixing time. In addition, repeated imaging following tagging can capture dynamic displacement spectra with increasing mixing times.

RESULTS

We demonstrate properties of DiSpect MRI using flow phantom experiments as well as in vivo brain scans. Specifically, the ability of DiSpect to perform retrospective vessel-selective perfusion imaging at multiple mixing times is highlighted.

CONCLUSION

The DiSpect variant is a new tool in the arsenal of MRI techniques for probing complex tissue dynamics. The flexibility and the rich information it provides open the possibility of alternative ways to quantitatively measure numerous complex spin dynamics, such as flow and perfusion within a single exam.

Quantification of Regional Cerebral Blood Flow Using Diffusion Imaging With Phase Contrast

BACKGROUND

The perfusion-related diffusion coefficient obtained from triexponential diffusion analysis is closely correlated with regional cerebral blood flow (rCBF), as assessed by arterial spin labeling (ASL) methods. However, this provides only a semiquantitative measure of rCBF, thereby making absolute rCBF quantification challenging.

PURPOSE

To obtain rCBF in a noninvasive manner using a novel diffusion imaging method with phase contrast (DPC), in which the total CBF from phase-contrast (PC) MRI was utilized to convert perfusion-related diffusion coefficients to rCBF values.

STUDY TYPE

Prospective.

SUBJECTS

Eleven healthy volunteers (nine men and two women; mean age, 23.9 years) participated in this study.

FIELD STRENGTH/SEQUENCE

A 3.0 T, single-shot diffusion echo-planar imaging with multiple b-values (0-3000 s/mm² ), PC-MRI, pulsed continuous ASL, and 3D T₁ -weighted fast field echo.

ASSESSMENT

rCBF and its correlations in the gray matter (GM) and white matter (WM) were compared between DPC and ASL methods. rCBF in the GM and WM and the GM/WM ratio were compared with the literature values obtained using [¹⁵ O]-water positron emission tomography (¹⁵ O-H₂ O PET).

STATISTICAL TESTS

Spearman's correlation coefficient and Wilcoxon signed-rank test were used. Significance was set at P < 0.05.

RESULTS

A significant positive correlation between DPC and ASL in terms of rCBF was observed in GM (R = 0.9), whereas the correlation between the two methods was poor in WM (R = 0.09). The rCBF in GM and WM and the GM/WM ratio obtained using DPC were consistent with the literature values assessed using ¹⁵ O-H₂ O PET. The rCBF value obtained using DPC was significantly higher in the GM and WM than that using ASL.

DATA CONCLUSION

DPC enabled noninvasive quantification of rCBF.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 1.

The evaluation of cerebral venous normal anatomy and variations by phase-contrast cranial magnetic resonance venography

BACKGROUND

The aim of our study is to determine the ability of the PC-CMRV technique to detect cranial anatomy, variations, thrombosis, to reveal the deficits of the technique and to discuss the reasons for these deficits on a physics basis.

MATERIALS AND METHODS

PC's detection rates of anatomic variations and physiological filling defects (FDs) were evaluated in 136 patients and compared with the time-of-flight (TOF) technique MRI and cadaveric studies.

RESULTS

The dominance correlation between the three evaluated sinuses (transverse sinus (TS), sigmoid sinus, jugular vein) which originated from different embryological buds were statistically significant and the right vessel chain was dominant. PC is inadequate to show some vessels like inferior sagittal sinus (anatomically, this vessel is approximately present in 100% of the cases, but it was only visualized in 41.2% of the patients in PC-MRI). Visualization of major veins was sufficient. PC-MRI creates physiological FDs in 27.2% (72,3% middle,10.3% inner,17% outer part) of the patients. The FDs were concentrated in the middle part and not observed in the dominant sinus.

CONCLUSIONS

The defects of visualization are present due to the PC's technique. It can be misdiagnosed as agenesis or thrombosis. PC creates a high incidence of physiologic FDs in TS. The results are not reliable, especially if FDs are in the middle part or non-dominant side.

Laboratory phase-contrast nanotomography of unstained Bombus terrestris compound eyes

Imaging the visual systems of bumblebees and other pollinating insects may increase understanding of their dependence on specific habitats and how they will be affected by climate change. Current high-resolution imaging methods are either limited to two dimensions (light- and electron microscopy) or have limited access (synchrotron radiation x-ray tomography). For x-ray imaging, heavy metal stains are often used to increase contrast. Here, we present micron-resolution imaging of compound eyes of buff-tailed bumblebees (Bombus terrestris) using a table-top x-ray nanotomography (nano-CT) system. By propagation-based phase-contrast imaging, the use of stains was avoided and the microanatomy could more accurately be reconstructed than in samples stained with phosphotungstic acid or osmium tetroxide. The findings in the nano-CT images of the compound eye were confirmed by comparisons with light- and transmission electron microscopy of the same sample and finally, comparisons to synchrotron radiation tomography as well as to a commercial micro-CT system were done.

Development and preclinical evaluation of a patient-specific high energy x-ray phase sensitive breast tomosynthesis system

BACKGROUND

This article reports the first x-ray phase sensitive breast tomosynthesis (PBT) system that is aimed for direct translation to clinical practice for the diagnosis of breast cancer.

PURPOSE

To report the preclinical evaluation and comparison of the newly built PBT system with a conventional digital breast tomosynthesis (DBT) system.

METHODS AND MATERIALS

The PBT system is developed based on a comprehensive inline phase contrast theoretical model. The system consists of a polyenergetic microfocus x-ray source and a flat panel detector mounted on an arm that is attached to a rotating gantry. It acquires nine projections over a 15° angular span in a stop-and-shoot manner. A dedicated phase retrieval algorithm is integrated with a filtered back-projection method that reconstructs tomographic slices. The American College of Radiology (ACR) accreditation phantom, a contrast detail (CD) phantom and mastectomy tissue samples were imaged at the same glandular dose levels by both the PBT and a standard of care DBT system for image quality characterizations and comparisons.

RESULTS

The PBT imaging scores with the ACR phantom are in good to excellent range and meet the quality assurance criteria set by the Mammography Quality Standard Act. The CD phantom image comparison and associated statistical analyses from two-alternative forced-choice reader studies confirm the improvement offered by the PBT system in terms of contrast resolution, spatial resolution, and conspicuity. The artifact spread function (ASF) analyses revealed a sizable lateral spread of metal artifacts in PBT slices as compared to DBT slices. Signal-to-noise ratio values for various inserts of the ACR and CD phantoms further validated the superiority of the PBT system. Mastectomy sample images acquired by the PBT system showed a superior depiction of microcalcifications vs the DBT system.

CONCLUSION

The PBT imaging technology can be clinically employed for improving the accuracy of breast cancer screening and diagnosis.

Impact of resveratrol-mediated increase in uterine artery blood flow on fetal haemodynamics, blood pressure and oxygenation in sheep

NEW FINDINGS

What is the central question of this study? Uterine artery blood flow helps to maintain fetal oxygen and nutrient delivery. We investigated the effects of increased uterine artery blood flow mediated by resveratrol on fetal growth, haemodynamics, blood pressure regulation and oxygenation in pregnant sheep. What is the main finding and its importance? Fetuses from resveratrol-treated ewes were significantly larger and exhibited a haemodynamic profile that might promote peripheral growth. Absolute uterine artery blood flow was positively correlated with umbilical vein oxygen saturation, absolute fetal oxygen delivery and fetal growth. Increasing uterine artery blood flow with compounds such as resveratrol might have clinical significance for pregnancy conditions in which fetal growth and oxygenation are compromised.

ABSTRACT

High placental vascular resistance hinders uterine artery (UtA) blood flow and fetal substrate delivery. In the same group of animals as the present study, we have previously shown that resveratrol (RSV) increases UtA blood flow, fetal weight and oxygenation in an ovine model of human pregnancy. However, the mechanisms behind changes in growth and the effects of increases in UtA blood flow on fetal circulatory physiology have yet to be investigated. Twin-bearing ewes received s.c. vehicle (VEH, n = 5) or RSV (n = 6) delivery systems at 113 days of gestation (term = 150 days). Magnetic resonance imaging was performed at 123-124 days to quantify fetal volume, blood flow and oxygen saturation of major fetal vessels. At 128 days, i.v. infusions of sodium nitroprusside and phenylephrine were administered to study the vascular tone of the fetal descending aorta. Maternal RSV increased fetal body volume (P = 0.0075) and weight (P = 0.0358), with no change in brain volume or brain weight. There was a positive relationship between absolute UtA blood flow and umbilical vein oxygen saturation, absolute fetal oxygen delivery and combined fetal twin volume (all P ≤ 0.05). There were no differences between groups in fetal haemodynamics or blood pressure regulation except for higher blood flow to the lower body in RSV fetuses (P = 0.0170). The observed increase in fetal weight might be helpful in pregnancy conditions in which fetal growth and oxygen delivery are compromised. Further preclinical investigations on the mechanism(s) accounting for these changes and the potential to improve growth in complicated pregnancies are warranted.

Empirical beam hardening and ring artifact correction for x-ray grating interferometry (EBHC-GI)

PURPOSE

Talbot-Lau grating interferometry enables the use of polychromatic x-ray sources, extending the range of potential applications amenable to phase contrast imaging. However, these sources introduce beam hardening effects not only from the samples but also from the gratings. As a result, grating inhomogeneities due to manufacturing imperfections can cause spectral nonuniformity artifacts when used with polychromatic sources. Consequently, the different energy dependencies of absorption, phase, and visibility contrasts impose challenges that so far have limited the achievable image quality. The purpose of this work was to develop and validate a correction strategy for grating-based x-ray imaging that accounts for beam hardening generated from both the imaged object and the gratings.

METHODS

The proposed two-variable polynomial expansion strategy was inspired by work performed to address beam hardening from a primary modulator. To account for the multicontrast nature of grating interferometry, this approach was extended to each contrast to obtain three sets of correction coefficients, which were determined empirically from a calibration scan. The method's feasibility was demonstrated using a tabletop Talbot-Lau grating interferometer micro-computed tomography (CT) system using CT acquisitions of a water sample and a silicon sample, representing low and high atomic number materials. Spectral artifacts such as cupping and ring artifacts were quantified using mean squared error (MSE) from the beam-hardening-free target image and standard deviation within a reconstructed image of the sample. Finally, the model developed using the water sample was applied to a fixated murine lung sample to demonstrate robustness for similar materials.

RESULTS

The water sample's absorption CT image was most impacted by spectral artifacts, but following correction to decrease ring artifacts, an 80% reduction in MSE and 57% reduction in standard deviation was observed. The silicon sample created severe artifacts in all contrasts, but following correction, MSE was reduced by 94% in absorption, 96% in phase, and 90% in visibility images. These improvements were due to the removal of ring artifacts for all contrasts and reduced cupping in absorption and phase images and reduced capping in visibility images. When the water calibration coefficients were applied to the lung sample, ring artifacts most prominent in the absorption contrast were eliminated.

CONCLUSIONS

The described method, which was developed to remove artifacts in absorption, phase, and normalized visibility micro-CT images due to beam hardening in the system gratings and imaged object, reduced the MSE by up to 96%. The method depends on calibrations that can be performed on any system and does not require detailed knowledge of the x-ray spectrum, detector energy response, grating attenuation properties and imperfections, or the geometry and composition of the imaged object.

Reliable phase-contrast flow volume magnetic resonance measurements are feasible without adjustment of the velocity encoding parameter

Purpose: To show that adjustment of velocity encoding (VENC) for phase-contrast (PC) flow volume measurements is not necessary in modern MR scanners with effective background velocity offset corrections. Approach: The independence on VENC was demonstrated theoretically, but also experimentally on dedicated phantoms and on patients with chronic aortic regurgitation ( n = 17 ) and one healthy volunteer. All PC measurements were performed using a modern MR scanner, where the pre-emphasis circuit but also a subsequent post-processing filter were used for effective correction of background velocity offset errors. Results: The VENC level strongly affected the velocity noise level in the PC images and, hence, the estimated peak flow velocity. However, neither the regurgitant blood flow volume nor the mean flow velocity displayed any clinically relevant dependency on the VENC level. Also, the background velocity offset was shown to be close to zero ( < 0.6    cm / s ) for a VENC range of 150 to 500    cm / s , adding no significant errors to the PC flow volume measurement. Conclusions: Our study shows that reliable PC flow volume measurements are feasible without adjustment of the VENC parameter. Without the need for VENC adjustments, the scan time can be reduced for the benefit of the patient.

Accelerated aortic 4D flow MRI with wave-CAIPI

PURPOSE

The aim of this study was to investigate the acceleration potential of wave-CAIPI (controlled aliasing in parallel imaging) for 4D flow MRI, provided that image quality and precision of flow parameters are maintained.

METHODS

The 4D flow MRIs with acceleration factor R = 2 were performed on 10 healthy volunteers, using both wave-CAIPI and standard Cartesian/2D-CAIPI sampling for reference. In addition, 1 patient with known aortic valve stenosis was examined. The flow rate ( Q ), net flow ( Q net ), peak velocity v max , and net average through-plane velocity ( v ¯ ⊥ ) were calculated in eight analysis planes in the ascending and descending aorta. The acquisitions were retrospectively undersampled (R = 6), and deviations of flow parameters and hemodynamic flow patterns were evaluated.

RESULTS

Flow parameters measured with an undersampled wave-CAIPI trajectory showed considerably smaller deviations to the references than the 2D-CAIPI images. For v max , the mean absolute differences were 6.02 ± 2.08 cm/s versus 14.36 ± 5.68 cm/s; for Q net , the mean absolute differences were 3.67 ± 1.40 ml versus 5.87 ± 1.91 ml for wave-CAIPI versus 2D-CAIPI, respectively. Noise calculations indicate that the 2D-CAIPI sampling exhibits a 43 ± 38 % higher average noise level than the wave-CAIPI technique. Qualitative discrepancies in hemodynamic flow patterns, visualized through streamlines, particle traces and flow velocity vectors, could be reduced by using the undersampled wave-CAIPI trajectory.

CONCLUSION

Use of wave-CAIPI instead of 2D-CAIPI sampling in retrospectively 6-fold accelerated 4D flow MRI enhances the precision of flow parameters. The acquisition time of 4D flow measurements could be reduced by a factor of 3, with minimal differences in flow parameters.

Acute-stage MRI cerebral oxygen consumption biomarkers predict 24-hour neurological outcome in a rat cardiac arrest model

Brain injury following cardiac arrest (CA) is thought to be caused by a sudden loss of blood flow resulting in disruption in oxygen delivery, neural function and metabolism. However, temporal trajectories of the brain's physiology in the first few hours following CA have not been fully characterized. Furthermore, the extent to which these early measures can predict future neurological outcomes has not been determined. The present study sought to perform dynamic measurements of cerebral blood flow (CBF), oxygen extraction fraction (OEF) and cerebral metabolic rate of oxygen (CMRO₂ ) with MRI in the first 3 hours following the return of spontaneous circulation (ROSC) in a rat CA model. It was found that CBF, OEF and CMRO₂ all revealed a time-dependent increase during the first 3 hours after the ROSC. Furthermore, the temporal trajectories of CBF and CMRO₂ , but not OEF, were different across rats and related to neurologic outcomes at a later time (24 hours after the ROSC) (P < .001). Rats who manifested better outcomes revealed faster increases in CBF and CMRO₂ during the acute stage. When investigating physiological parameters measured at a single time point, CBF (ρ = 0.82, P = .004) and CMRO₂ (ρ = 0.80, P = .006) measured at ~ 3 hours post-ROSC were positively associated with neurologic outcome scores at 24 hours. These findings shed light on brain physiological changes following CA, and suggest that MRI measures of brain perfusion and metabolism may provide a potential biomarker to guide post-CA management.

Analysis of accelerated 4D flow MRI in the murine aorta by radial acquisition and compressed sensing reconstruction

Preclinical 4D flow MRI remains challenging and is restricted for parallel imaging acceleration due to the limited number of available receive channels. A radial acquisition with combined parallel imaging and temporal compressed sensing reconstruction was implemented to achieve accelerated preclinical 4D flow MRI. In order to increase the accuracy of the measured velocities, a quantitative evaluation of different temporal regularization weights for the compressed sensing reconstruction based on velocity instead of magnitude data is performed. A 3D radial retrospectively triggered phase contrast sequence with a combined parallel imaging and compressed sensing reconstruction with temporal regularization was developed. It was validated in a phantom and in vivo (C57BL/6 J mice), against an established fully sampled Cartesian sequence. Different undersampling factors (USFs [12, 15, 20, 30, 60]) were evaluated, and the effect of undersampling was analyzed in detail for magnitude and velocity data. Temporal regularization weights λ were evaluated for different USFs. Acceleration factors of up to 20 compared with full Nyquist sampling were achieved. The peak flow differences compared with the Cartesian measurement were the following: USF 12, 3.38%; USF 15, 4.68%; USF 20, 0.95%. The combination of 3D radial center-out trajectories and compressed sensing reconstruction is robust against motion and flow artifacts and can significantly reduce measurement time to 30 min at a resolution of 180 μm³ . Concisely, radial acquisition with combined compressed sensing and parallel imaging proved to be an excellent method for analyzing complex flow patterns in mice.

Stasis Leg Ulcers: Venous System Revises by Triggered Angiography Non-Contrast-Enhanced Sequence Magnetic Resonance Imaging

Objectives: The distribution of venous pathology in stasis leg ulcers is unclear. The main reason for this uncertainty is the lack of objective diagnostic tools. To fill this gap, we assessed the effectiveness of triggered angiography non-contrast-enhanced (TRANCE)-magnetic resonance imaging (MRI) in determining the venous status of patients with stasis leg ulcers. Methods: This prospective observational study included the data of 23 patients with stasis leg ulcers who underwent TRANCE-MRI between April 2017 and May 2020; the data were retrospectively analyzed. TRANCE MRI utilizes differences in vascular signal intensity during the cardiac cycle for subsequent image subtraction, providing not only a venogram but also an arteriogram without the use of contrast agents or radiation. Results: TRANCE MRI revealed that the stasis leg ulcers of nine of the 23 patients could be attributed to valvular insufficiency and venous occlusion (including deep venous thrombosis [DVT], May–Thurner syndrome, and other external compression). Moreover, TRANCE MRI demonstrated no venous pathology in five patients (21.7%). We analyzed TRANCE MRI hemodynamic parameters, namely stroke volume, forward flow volume, backward flow volume, regurgitant fraction, absolute volume, mean flux, stroke distance, and mean velocity, in the external iliac vein, femoral vein, popliteal vein, and great saphenous vein (GSV) in three of the patients with valvular insufficiency and three of those with venous occlusion. We found that the mean velocity and stroke volume in the GSV was higher than that in the popliteal vein in all patients with venous valvular insufficiency. Conclusions: Stasis leg ulcers may have no underlying venous disease and could be confirmed by TRANCE-MRI. TRANCE MRI has good Interrater reliability between Duplex study in greater saphenous venous insufficiency. It also potentially surpasses existing diagnostic modalities in terms of distinguishable hemodynamic figures. Accordingly, TRANCE-MRI is a safe and useful tool for examining stasis leg ulcers and is extensively applied currently.

Left Ventricular Blood Flow Kinetic Energy Assessment by 4D Flow Cardiovascular Magnetic Resonance: A Systematic Review of the Clinical Relevance

Background: There is an emerging body of evidence that supports the potential clinical value of left ventricular (LV) intracavity blood flow kinetic energy (KE) assessment using four-dimensional flow cardiovascular magnetic resonance imaging (4D flow CMR). The aim of this systematic review is to summarize studies evaluating LV intracavity blood flow KE quantification methods and its potential clinical significance. Methods: A systematic review search was carried out on Medline, Pubmed, EMBASE and CINAHL. Results: Of the 677 articles screened, 16 studies met eligibility. These included six (37%) studies on LV diastolic function, another six (37%) studies on heart failure or cardiomyopathies, three (19%) studies on ischemic heart disease or myocardial infarction and finally, one (6%) study on valvular heart disease, namely, mitral regurgitation. One of the main strengths identified by these studies is high reproducibility of LV blood flow KE hemodynamic assessment (mean coefficient of variability = 6 ±  2%) for the evaluation of LV diastolic function. Conclusions: The evidence gathered in this systematic review suggests that LV blood flow KE has great promise for LV hemodynamic assessment. Studies showed increased diagnostic confidence at no cost of additional time. Results were highly reproducible with low intraobserver variability.

3D virtual pathohistology of lung tissue from Covid-19 patients based on phase contrast X-ray tomography

We present a three-dimensional (3D) approach for virtual histology and histopathology based on multi-scale phase contrast x-ray tomography, and use this to investigate the parenchymal architecture of unstained lung tissue from patients who succumbed to Covid-19. Based on this first proof-of-concept study, we propose multi-scale phase contrast x-ray tomography as a tool to unravel the pathophysiology of Covid-19, extending conventional histology by a third dimension and allowing for full quantification of tissue remodeling. By combining parallel and cone beam geometry, autopsy samples with a maximum cross section of 8 mm are scanned and reconstructed at a resolution and image quality, which allows for the segmentation of individual cells. Using the zoom capability of the cone beam geometry, regions-of-interest are reconstructed with a minimum voxel size of 167 nm. We exemplify the capability of this approach by 3D visualization of diffuse alveolar damage (DAD) with its prominent hyaline membrane formation, by mapping the 3D distribution and density of lymphocytes infiltrating the tissue, and by providing histograms of characteristic distances from tissue interior to the closest air compartment.

Quantitative perfusion mapping with induced transient hypoxia using BOLD MRI

PURPOSE

Gadolinium-based dynamic susceptibility contrast (DSC) is commonly used to characterize blood flow in patients with stroke and brain tumors. Unfortunately, gadolinium contrast administration has been associated with adverse reactions and long-term accumulation in tissues. In this work, we propose an alternative deoxygenation-based DSC (dDSC) method that uses a transient hypoxia gas paradigm to deliver a bolus of paramagnetic deoxygenated hemoglobin to the cerebral vasculature for perfusion imaging.

METHODS

Through traditional DSC tracer kinetic modeling, the MR signal change induced by this hypoxic bolus can be used to generate regional perfusion maps of cerebral blood flow, cerebral blood volume, and mean transit time. This gas paradigm and blood-oxygen-level-dependent (BOLD)-MRI were performed concurrently on a cohort of 66 healthy and chronically anemic subjects (age 23.5 ± 9.7, female 64%).

RESULTS

Our results showed reasonable global and regional agreement between dDSC and other flow techniques, such as phase contrast and arterial spin labeling.

CONCLUSION

In this proof-of-concept study, we demonstrated the feasibility of using transient hypoxia to generate a contrast bolus that mimics the effect of gadolinium and yields reasonable perfusion estimates. Looking forward, optimization of the hypoxia boluses and measurement of the arterial-input function is necessary to improve the accuracy of dDSC. Additionally, a cross-validation study of dDSC and DSC in brain tumor and ischemic stroke subjects is warranted to evaluate the clinical diagnostic utility of this approach.

Comprehensive characterization of TSV etching performance with phase-contrast X-ray microtomography

Comprehensive evaluation of through-silicon via (TSV) reliability often requires deterministic and 3D descriptions of local morphological and statistical features of via formation with the Bosch process. Here, a highly sensitive phase-contrast X-ray microtomography approach is presented based on recorrection of abnormal projections, which provides comprehensive and quantitative characterization of TSV etching performance. The key idea is to replace the abnormal projections at specific angles in principles of linear interpolation of neighboring projections, and to distinguish the interface between silicon and air by using phase-retrieval algorithms. It is demonstrated that such a scheme achieves high accuracy in obtaining the etch profile based on the 3D microstructure of the vias, including diameter, bottom curvature radius, depth and sidewall angle. More importantly, the 3D profile error of the via sidewall and the consistency of parameters among all the vias are achieved and analyzed statistically. The datasets in the results and the 3D microstructure can be applied directly to a reference and model for further finite element analysis. This method is general and has potentially broad applications in 3D integrated circuits.

Deep Learning of Cancer Stem Cell Morphology Using Conditional Generative Adversarial Networks. Biomolecules. 2020;10. [PMID: 32575396 PMCID: PMC7355573 DOI: 10.3390/biom10060931]

Deep-learning workflows of microscopic image analysis are sufficient for handling the contextual variations because they employ biological samples and have numerous tasks. The use of well-defined annotated images is important for the workflow. Cancer stem cells (CSCs) are identified by specific cell markers. These CSCs were extensively characterized by the stem cell (SC)-like gene expression and proliferation mechanisms for the development of tumors. In contrast, the morphological characterization remains elusive. This study aims to investigate the segmentation of CSCs in phase contrast imaging using conditional generative adversarial networks (CGAN). Artificial intelligence (AI) was trained using fluorescence images of the Nanog-Green fluorescence protein, the expression of which was maintained in CSCs, and the phase contrast images. The AI model segmented the CSC region in the phase contrast image of the CSC cultures and tumor model. By selecting images for training, several values for measuring segmentation quality increased. Moreover, nucleus fluorescence overlaid-phase contrast was effective for increasing the values. We show the possibility of mapping CSC morphology to the condition of undifferentiation using deep-learning CGAN workflows.