Experimental demonstration of scene-based cophasing in optical synthetic aperture imaging using the SPGD algorithm.

Large-aperture telescopes based on optical synthetic aperture imaging are investigated for recent high-resolution spaceborne observations. An enabling technique of aperture synthesis is a cophasing method to suppress a piston-tip-tilt error between sub-apertures. This paper proposes a scene-based cophasing technique using the stochastic parallel gradient descent (SPGD) algorithm, assuming application to high-resolution Earth observation. A significant advantage of the SPGD algorithm is a model-less cophasing capability based on extended scenes, but the simultaneous scene-based piston-tip-tilt correction between multiple apertures has not been demonstrated. In this paper, we developed a tabletop synthetic aperture imaging system with 37 sub-apertures and demonstrated extended-scene-based piston-tip-tilt control by optimizing applied voltages to 111 actuators simultaneously. The demonstration experiments used not only static scenes but also a time-varying dynamic scene for observation targets. In every measurement, the proposed scene-based approach reduced the initially defined piston-tip-tilt errors, and the image sharpness significantly improved, although the correction rate in the dynamic scene observation was slower. Finally, this paper discusses the influence of scene dynamics on image-based cophasing.

Sequential phase diversity for wavefront correction using a deformable mirror with modeling errors: publisher's note.

This publisher's note corrects an error in Appl. Opt.62, 7931 (2023)APOPAI0003-693510.1364/AO.497155.

Sequential phase diversity for wavefront correction using a deformable mirror with modeling errors.

The phase diversity (PD) method is effective for scene-based wavefront sensing and control (WFSC) in spaceborne high-resolution imagers for Earth observation. The simplest way of performing the PD WFSC is offering a diversity wavefront by directly actuating a corrective device, such as a deformable mirror. However, this strategy faces a challenge in constructing a numerical model of the provided diversity wavefront because some corrective actuators' properties prevent us from precisely determining their deflection behaviors. To avoid this modeling issue, we propose the sequential PD (SPD) method to compensate for static aberration using a corrective device with modeling errors. The SPD WFSC repeats the PD WFSC to gradually correct the aberration, where the estimated corrective wavefront is regarded as the known diversity in the subsequent PD WFSC. The numerical simulation validated that the proposed idea improved the correction performance when a corrective device had a linear modeling error. Additionally, a demonstration experiment succeeded in aberration removal using a face-sheet deformable mirror with inter-actuator coupling and non-linear responses. An additional simulation demonstrated that the proposed method effectively corrected the discontinuous wavefront aberration in multi-aperture imaging systems. The SPD WFSC can potentially bring us optical remote sensing systems with unprecedentedly high resolution.

Deviation-based wavefront correction using the SPGD algorithm for high-resolution optical remote sensing.

Model-free image-based wavefront correction techniques, such as the stochastic parallel gradient descent (SPGD) algorithm, will be useful in achieving diffraction-limited optical performance in near-future optical remote sensing systems. One difficulty facing the image-based method is that the correction performance depends on the evaluation metric and the evaluated scene. We propose several evaluation functions and investigate the relationship between the optimization speed and the scene textures for each metric in the SPGD algorithm. Based on the simulation results, the study experimentally compared wavefront correction performance using four cost functions and two extended aerial images. Consequently, we found that the deviation-based cost function allowed efficient wavefront correction for versatile extended scenes. In addition, observing extended scenes with distinct structures can facilitate correction speed. Furthermore, we numerically validated this approach in a segmented-aperture imaging system for large telescopes. We believe that the presented approach allows us to realize spaceborne remote sensing with unprecedented high angular resolution.

Chest compressions become deeper when pushing with forward lean: A simulation study.

AIM: Chest compression depth (CCD) in cardiopulmonary resuscitation is important. However, lightweight rescuers have difficulty achieving an appropriate depth. Chest compression force (CCFORCE) can be increased by placing the arms at 100° to the patient's frontal plane. In a simulation manikin study, we compared the CCD at 90° and 100° among lightweight Asian females and hypothesized that the CCD would be greater when the arms were placed at 100°. METHODS: We included 35 lightweight female students from Shimane University who performed compressions 30 times each at 90° and 100°. The CCFORCE and CCD and the residual force on the chest wall during decompression for each chest compression were compared using CPRmeter-2. RESULTS: Of the 35 participants, 3 were excluded because their angles deviated from the prescribed angle. Thirty-two participants were categorized according to CCD at 90°: ≤40 mm (group 1), 41-49 mm (group 2), and ≥ 50 mm (group 3). The overall mean CCD increased from 90° to 100° (44.3 ± 8.2 mm vs. 48.1 ± 7.2 mm; p < 0.05). The mean CCD changes between 90° and 100° were 34.4 ± 4.7 mm vs. 42.9 ± 4.8 mm (p < 0.05) in group 1, 44.9 ± 2.5 mm vs. 47.0 ± 4.2 mm (p = 0.17) in group 2, and 53.0 ± 2.7 mm vs. 55.4 ± 5.6 mm (p < 0.05) in group 3. The residual force was greater when the chest compression angle was 100°. CONCLUSION: CCD can be increased for lightweight rescuers when using a forward leaning position of 100° to the frontal plane of the patient. Further research is required to obtain more realistic situations.

Nanoscale Visualization of Phase Transition in Melting of Sn-Bi Particles by In situ Hard X-ray Ptychographic Coherent Diffraction Imaging.

The phase transition in the melting of Sn­Bi eutectic solder alloy particles was observed by in situ hard X-ray ptychographic coherent diffraction imaging with a pin-point heating system. Ptychographic diffraction patterns of micrometer-sized Sn­Bi particles were collected at temperatures from room temperature to 540 K. The projection images of each particle were reconstructed at a spatial resolution of 25 nm, showing differences in the phase shifts due to two crystal phases in the Sn­Bi alloy system and the Sn/Bi oxides at the surface. By quantitatively evaluating the Bi content, it became clear that the nonuniformity of the composition of Sn and Bi at the single-particle level exists when the particles are synthesized by centrifugal atomization.

Nanoscale determination of interatomic distance by ptychography-EXAFS method using advanced Kirkpatrick-Baez mirror focusing optics.

This work demonstrates a combination technique of X-ray ptychography and the extended X-ray absorption fine structure (ptychography-EXAFS) method, which can determine the interatomic distances of bulk materials at the nanoscale. In the high-resolution ptychography-EXAFS method, it is necessary to use high-intense coherent X-rays with a uniform wavefront in a wide energy range, hence a ptychographic measurement system installed with advanced Kirkpatrick-Baez mirror focusing optics is developed and its performance is evaluated. Ptychographic diffraction patterns of micrometre-size MnO particles are collected by using this system at 139 energies between 6.504 keV and 7.114 keV including the Mn K absorption edge, and then the EXAFS of MnO is derived from the reconstructed images. By analyzing the EXAFS spectra obtained from a 48 nm × 48 nm region, the nanoscale bond lengths of the first and second coordination shells of MnO are determined. The present approach has great potential to elucidate the unclarified relationship among the morphology, electronic state and atomic arrangement of inhomogeneous bulk materials with high spatial resolution.

Multibeam ptychography with synchrotron hard X-rays.

We report the first demonstration of multibeam ptychography using synchrotron hard X-rays, which can enlarge the field of view of the reconstructed image of objects by efficiently using partially coherent X-rays. We measured the ptychographic diffraction patterns of a Pt test sample and MnO particles using three mutually incoherent coherent beams with a high intensity that were produced by using both the multiple slits and a pair of focusing mirrors. We successfully reconstructed the phase map of the samples at a spatial resolution of 25 nm in a field of view about twice as wide as that in the single-beam ptychography. We also computationally simulated a feasible experimental setup using random modulators to further enlarge the field of view by increasing the number of available beams. The present method has the potential to enable the high spatial resolution and large field-of-view observation of specimens in materials science and biology.

Diagnosis of infective endocarditis with cardiac CT in an adult.

The diagnosis of infective endocarditis is based on modified Duke's criteria, which includes clinical, biological, and echocardiographic findings. However, computed tomography (CT) has not been mentioned as a diagnostic tool in the criteria. We report a case of infective endocarditis confirmed by cardiac CT in which we could identify vegetations and perivalvular abscess not on transthoracic echocardiography and transesophageal echocardiography. Cardiac CT was feasible imaging modality for evaluating and diagnosing infective endocarditis. Cardiac CT should be recommended in patients with clinical suspicion of infective endocarditis even when transthoracic echocardiography and transesophageal echocardiography is negative for infective endocarditis.

A Homozygous CASQ2 Mutation in a Japanese Patient with Catecholaminergic Polymorphic Ventricular Tachycardia.

A 62-year-old female had suffered from recurrent syncopal episodes triggered by physical and emotional stress since childhood. She had no family history of sudden death. An intensive examination could not detect any structural disease, and exercise stress testing provoked polymorphic ventricular ectopy followed by polymorphic ventricular tachycardia accompanied with syncope leading to a diagnosis of catecholaminergic polymorphic ventricular tachycardia (CPVT). A genetic analysis with a next generation sequencer identified a homozygous W361X mutation in the CASQ2 gene. Careful history taking disclosed that her parents had a consanguineous marriage. Here we present a Japanese patient with a recessive form of CPVT.

[Rapid Recanalization of Cerebral Venous Sinus Thrombosis Secondary to Severe Dehydration:A Case Report].

A 41-year-old healthy man presented with sudden disturbance of consciousness and convulsion during a marathon. Computed tomography revealed a lateral sinus sign in the posterior fossa, and magnetic resonance(MR)venography revealed a flow gap in the posterior part of the superior sagittal sinus and bilateral transverse sinus, although the other MR image sequences were normal. Laboratory data revealed dehydration, acute kidney failure, and rhabdomyolysis. Owing to immediate correction of dehydration, clinical symptoms and radiological abnormality improved rapidly. Cerebral venous sinus thrombosis(CVST)is a rare condition, accounting for <1% of all stroke cases. In all cases, CVST cannot cause cerebral infarction or hemorrhagic change but in any case, may present a transient ischemic attack-like event because of rapid spontaneous recanalization. Therefore, CVST may occur more frequently than expected.

Three-dimensional iterative multislice reconstruction for ptychographic X-ray computed tomography.

Ptychographic X-ray computed tomography (PXCT) is a potential tool for visualizing three-dimensional (3D) structures of large-volume samples at high spatial resolution. Currently, both the requirement of a large number of views and the narrow depth of field limit the range of applications of PXCT. Here, we propose an improved 3D reconstruction algorithm for PXCT that is based on 3D iterative reconstruction and multislice phase retrieval calculation. Computer simulations showed that the proposed algorithm can reduce the number of required views without degrading the spatial resolution. In a synchrotron experiment, ptychographic diffraction data sets of a flat and thick processor specimen were collected under a limited-angle condition, and then high-resolution multislice images of the Cu multilevel interconnects were clearly reconstructed using the proposed algorithm. The proposed algorithm is expected to open up a new frontier of large-volume 3D nanoimaging in various fields.

Visualization of Heterogeneous Oxygen Storage Behavior in Platinum-Supported Cerium-Zirconium Oxide Three-Way Catalyst Particles by Hard X-ray Spectro-Ptychography.

The cerium density and valence in micrometer-size platinum-supported cerium-zirconium oxide Pt/Ce2 Zr2 Ox (x=7-8) three-way catalyst particles were successfully mapped by hard X-ray spectro-ptychography (ptychographic-X-ray absorption fine structure, XAFS). The analysis of correlation between the Ce density and valence in ptychographic-XAFS images suggested the existence of several oxidation behaviors in the oxygen storage process in the Ce2 Zr2 Ox particles. Ptychographic-XAFS will open up the nanoscale chemical imaging and structural analysis of heterogeneous catalysts.

Multislice imaging of integrated circuits by precession X-ray ptychography.

A method for nondestructively visualizing multisection nanostructures of integrated circuits by X-ray ptychography with a multislice approach is proposed. In this study, tilt-series ptychographic diffraction data sets of a two-layered circuit with a ∼1.4 µm gap at nine incident angles are collected in a wide Q range and then artifact-reduced phase images of each layer are successfully reconstructed at ∼10 nm resolution. The present method has great potential for the three-dimensional observation of flat specimens with thickness on the order of 100 µm, such as three-dimensional stacked integrated circuits based on through-silicon vias, without laborious sample preparation.

[A Case of Cerebral Venous Sinus Thrombosis, Secondary to Subclinical Basedow Disease].

Cerebral venous sinus thrombosis(CVST)is a rare condition accounting for <1% of all strokes. It has been linked to a multitude of risk factors, including infections, oral contraceptive use, coronary disease, malignant disease, trauma, surgery, coagulopathy and several others. However, the association between hyperthyroidism and CVST is poorly understood. We describe here a rare case of CVST, secondary to subclinical Basedow disease. A 68-year-old woman with general fatigue, headache, speech disturbance and slow behavior was admitted to our hospital. Computed tomography(CT)and magnetic resonance imaging revealed a fresh infarction in the left temporal lobe, and CT angiography revealed filling defects of superior sagittal sinus and transverse sinus. Moreover, the patient was diagnosed with Basedow disease for the first time, by examination for tachycardia. This case suggests that it is essential to have a new awareness that hyperthyroidism is an important risk factor for CVST.

[A Case of Dural Arteriovenous Fistula in the Anterior Cranial Fossa that Developed Remote from the Craniotomy Site after Surgery].

Dural arteriovenous fistula(dAVF)is relatively rare, and its etiology remains uncertain. Generally, dAVF is thought to be acquired and has been reported to develop secondary to sinus thrombosis, head injury, infection, and surgery. We report a rare case of dAVF in the anterior cranial fossa that developed remote from the craniotomy site after surgery. A 52-year-old man underwent surgery for hypertensive intracerebral hemorrhage 4 years prior. Perioperative imaging modalities demonstrated no abnormal vascular malformation except for an un-ruptured anterior communicating artery aneurysm. Four years later, follow-up magnetic resonance angiography showed abnormal vascular malformation in the anterior cranial fossa, and cerebral angiography demonstrated dAVF. dAVF and aneurysm were successfully treated. Possible formation of a dAVF should be considered after craniotomy.

Use of Kramers-Kronig relation in phase retrieval calculation in X-ray spectro-ptychography.

Coherent diffraction imaging (CDI) is a method for reconstructing the complex-valued image of an object from diffraction intensities by using iterative phasing methods. X-ray ptychography is a scanning type of CDI using X-rays, allowing us to visualize the complex transmission function of an extended specimen. We here propose the use of the Kramers-Kronig relation (KKR) as an additional constraint in phase retrieval algorithms for multiple-energy X-ray ptychography using the absorption edge of a specific element. A numerical simulation showed that the speed of convergence was increased by using the improved algorithm with the KKR. We successfully demonstrated its usefulness in a proof-of-principle experiment at SPring-8. The present algorithm is particularly useful for imaging X-ray absorption fine structures of a specific element buried within thick samples by hard X-ray spectro-ptychography.

[A Very Rare Case of Diffuse Subependymal Metastases from Small Cell Lung Carcinoma].

While parenchymal metastases are common in solid systemic cancers, subependymal metastases are rare. Approximately half of the reported cases of intraventricular metastases originate from renal carcinoma. A 65-year-old man presented with general fatigue, appetite loss, nausea, and disorientation. Radiological examination revealed diffuse periventricular tumors. The patient underwent an open biopsy via right frontotemporal craniotomy. The patient was diagnosed with metastatic small cell lung carcinoma after histopathological examination. Although subependymal metastases from solid systemic cancer are very rare, this ventricular wall abnormality in the cancer patients must not be overlooked. Many small subependymal metastases might be missed on routine examination.

[A Case of Intracranial Localized Castleman's Disease Mimicking Convexity Meningioma].

A 68-year-old man presented with abnormal behavior and Todd's paralysis on the right side after having taken a bath. Computed tomography and magnetic resonance imaging revealed a tumor mimicking convexity meningioma that had a perifocal edema, although its mass was not very large. The patient underwent surgery, and full recovery was achieved following a total removal of the lesion. Pathohistological examination demonstrated an intermediate type of Castleman's disease. The final diagnosis was intracranial localized Castleman's disease because the results of the full physical examination and laboratory analyses were normal. Castleman's disease is a rare lymphoproliferative disorder of unknown etiology. Moreover, intracranial involvement is very rare. In cases of intracranial meningeal tumors with perifocal edema, we should take this disease into consideration in the differential diagnosis.