Spiral Scan Research Articles

Accelerated Nano-Optical Imaging through Sparse Sampling.

The integration time and signal-to-noise ratio are inextricably linked when performing scanning probe microscopy based on raster scanning. This often yields a large lower bound on the measurement time, for example, in nano-optical imaging experiments performed using a scanning near-field optical microscope (SNOM). Here, we utilize sparse scanning augmented with Gaussian process regression to bypass the time constraint. We apply this approach to image charge-transfer polaritons in graphene residing on ruthenium trichloride (α-RuCl3) and obtain key features such as polariton damping and dispersion. Critically, nano-optical SNOM imaging data obtained via sparse sampling are in good agreement with those extracted from traditional raster scans but require 11 times fewer sampled points. As a result, Gaussian process-aided sparse spiral scans offer a major decrease in scanning time.

Mirrorless MEMS imaging: a nonlinear vibrational approach utilizing aerosol-jetted PZT-actuated fiber MEMS scanner for microscale illumination.

This study introduces a novel image capture and lighting techniques using a cutting-edge hybrid MEMS scanner system designed for compact microscopic imaging. The scanner comprises a tapered optical fiber waveguide and innovative aerosol-jet printed PZT (lead zirconate titanate) bimorph push-pull actuators on a stainless-steel substrate, effectively addressing issues that are commonly associated with PZT on silicon substrates such as fracture and layer separation. By leveraging nonlinear vibration, the scanner achieves a spiral scan pattern from a single signal input, in addition to the expected two-dimensional scanning and target illumination from two phase-shifted inputs. This capability is further enhanced by a novel process to taper the optical fiber, which reduces illumination scattering and tunes the fiber to the resonant frequencies of the scanner. The precisely tapered tip enables large fields of view while maintaining independent 2-axis scanning through one-degree-of-freedom actuation. Experimental validation showcases the successful generation of a spiral scan pattern with a 60 μm diameter scan area and a 10 Hz frame rate, effectively reconstructing scanned images of 5 μm lines, cross patterns (15 μm in length with a 5 μm gap), and structures of a Psychodidae wing.

Reducing windmill artifacts in clinical spiral CT using a deep learning-based projection raw data upsampling: Method and robustness evaluation.

Multislice spiral computed tomography (MSCT) requires an interpolation between adjacent detector rows during backprojection. Not satisfying the Nyquist sampling condition along the z-axis results in aliasing effects, also known as windmill artifacts. These image distortions are characterized by bright streaks diverging from high contraststructures. The z-flying focal spot (zFFS) is a well-established hardware-based solution that aims to double the sampling rate in longitudinal direction and therefore reduce aliasing artifacts. However, given the technical complexity of the zFFS, this work proposes a deep learning-based approach as an alternativesolution. We propose a supervised learning approach to perform a mapping between input projections and the corresponding rows required for double sampling in the z-direction. We present a comprehensive evaluation using both a clinical dataset obtained using raw data from 40 real patient scans acquired with zFFS and a synthetic dataset consisting of 100 simulated spiral scans using a phantom specifically designed for our problem. For the clinical dataset, we utilized 32 scans as training set and 8 scans as validation set, whereas for the synthetic dataset, we used 80 scans for training and 20 scans for validation purposes. Both qualitative and quantitative assessments are conducted on a test set consisting of nine real patient scans and six phantom measurements to validate the performance of our approach. A simulation study was performed to investigate the robustness against different scan configurations in terms of detector collimation and pitchvalue. In the quantitative comparison based on clinical patient scans from the test set, all network configurations show an improvement in the root mean square error (RMSE) of approximately 20% compared to neglecting the doubled longitudinal sampling by the zFFS. The results of the qualitative analysis indicate that both clinical and synthetic training data can reduce windmill artifacts through the application of a correspondingly trained network. Together with the qualitative results from the test set phantom measurements it is emphasized that a training of our method with synthetic data resulted in superior performance in windmill artifactreduction. Deep learning-based raw data interpolation has the potential to enhance the sampling in z-direction and thus minimize aliasing effects, as it is the case with the zFFS. Especially a training with synthetic data showed promising results. While it may not outperform zFFS, our method represents a beneficial solution for CT scanners lacking the necessary hardware components forzFFS.

Laser Scanning Microscopy for Tomographic Imaging of Roughness and Point Absorbers in Optical Surfaces

High-precision laser interferometric instruments require optical surfaces with a close to perfect contour, as well as low scattering and absorption. Especially, point absorbers are problematic because they heat up and locally deform the otherwise flat surface, resulting in correlations between absorption and contour. Here, we present a spiral laser scanning microscopy approach for the reconstruction of the 2 complementary images of an optical surface. The “phase image” is related to the surface profile including roughness. Our experiment achieves a sensitivity of up to (3.1±1.4) fm/ Hz with a (5.29±0.06)-μm transversal resolution. The “loss image” localizes point absorbers. The 2 images show correlations for some features proving the particular strength of our tomographic approach, which should help further improving optical surfaces or to understand dynamic processes of surface physics.

The advanced motion control system in HEPS beamline

In synchrotron radiation facilities such as the High Energy Photon Source (HEPS), numerous motorized actuators are equipped on the optics devices of HEPS beamline to manipulate the orientation of crystals and mirrors, thereby altering the position and characteristics of X-rays. The motion control system (MCS) plays an important role in the optics devices of HEPS beamlines, such as monochromator, K-B mirror and sample plants. In order to acquire the specify properties of X-ray and satisfy the complex experimental requirements, MCS must have the ability to handle the complicated control demands. Therefore, HEPS has developed a standardized motion control system for synchrotron radiation applications, which is a distributed system based on EtherCAT fieldbus. The hardware of this system consists of the control unit and driver unit, which has the flexibility to suit for different applications. The software of MCS is designed under the Experimental Physics and Industrial Control System (EPICS), which is very popular in synchrotron radiation facilities all over the world. In this paper, the performance tests of IOC software were demonstrated, and a few flyscan applications were given, which include spiral scan, raster scan and position event trigger, to demonstrate the feasibility and effectiveness of this system.

Postmortem Computed Tomography: A Supplant Technique to Autopsy for Firearm Injuries in the Head

Background: Autopsy is more time-consuming if the bullet/bullets are lodged at the difficult-to-access sites of the head, especially maxillofacial regions. The procedure of suturing the deceased becomes even more difficult after the retrieval of bullets post-dissection of facial tissues. The altered aesthetics psychologically and emotionally disturb the already bereaved next of kin. The authors explored the utility of PMCT and propose a methodology of targeted dissection/minimally invasive approach to retrieve the bullet. The authors discussed the feasibility to conclude the cause of death in cases of single/multiple firearm injuries to the head using PMCT alone. Methods: The authors evaluated three cases of firearm deaths at a distance lesser than close range to the head. The deceased was subjected to PMCT scanning using a 16-slice Multi-Slice CT spiral scanner and findings were analyzed using the Vitrea software v.6.9.1 with the slice thickness ranging from 0.5mm to 5mm. A routine conventional autopsy was conducted post-scanning. Two of the three cases were suicide and succumbed to a single firearm injury while the third case was a homicide due to multiple firearm injuries. Conclusion: PMCT alone can be utilized and relied upon in deaths due to a single shot to the head and suggests a combined methodology of PMCT evaluation and minimally invasive approach in cases of multiple firearm injuries for better correlation of wound track. Lastly, PMCT helped in a targeted approach to reach the in situ bullets more precisely than any other radiological technique which upholds the humanitarian forensic aspect.

Feasibility study of using low-kilovoltage, prospective gating, high-pitch, dual-source computed tomography prior to transcatheter aortic valve replacement: analysis of image quality and radiation dose.

Computed tomography (CT) scans before transcatheter aortic valve replacement (TAVR) are used to evaluate the aortic valve and guide the selection of appropriate valve stents. Accurate imaging evaluation can ensure the success rate of surgery while reducing the incidence of complications. Multiple studies have adopted a protocol of coronary artery, aortic valve, and total aortic scan, with the patients receiving higher radiation doses. The aim of this study was to evaluate the image quality, radiation dose, and diagnostic performance of dual-source computed tomography (DSCT) with high-pitch spiral scanning for TAVR. A total of 240 patients being evaluated for TAVR were continuously enrolled. Based on the differences in electrocardiography (ECG) gating and tube voltage, the patients were divided into 4 groups: group A, 70-kV prospective ECG gating, high-pitch helical; group B, 70-kV retrospective ECG gating; group C, 100-kV prospective ECG gating, high-pitch helical; and group D, 120-kV prospective ECG gating, high-pitch helical. Image quality was evaluated on a 4-point scale. The image signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated for objective evaluation. The radiation doses of all patients were recorded. The image quality and radiation dose of each group were compared. There were no differences in age, body mass index (BMI), subjective image quality scores, CT values between the aorta and the coronary artery, or image CNR between the 4 groups. The mean radiation doses of groups A-D were 4.13±0.69, 4.79±0.58, 12.00±1.62, and 15.01±1.90 mSv, respectively. The mean radiation dose in group A (70-kV prospective ECG gating) decreased significantly (P<0.05). Using low-kilovoltage, high-pitch DSCT can provide comparable image quality for TAVR evaluation and significantly reduce the radiation dose.

Numerical Investigation of the Thermal Distortion in Multi-Laser Powder Bed Fusion (ML-PBF) Additive Manufacturing of Inconel 625

Metal additive manufacturing, especially laser powder bed fusion (L-PBF), is increasingly being used to fabricate complex parts with fine features. Emerging L-PBF systems have large build volumes and several lasers that operate simultaneously. Hence, they can produce large and complex parts at reduced costs and short build times. However, the thermal distortion remains a critical challenge. Hence, a thorough understanding of the impact of multiple lasers on part distortion in multi-laser PBF (ML-PBF) is imperative. Although experimental investigation is possible, a more conducive approach is to design and create suitable predictive models to understand the impact of multiple lasers consolidating a part into layers. To fulfill this goal, in this study, a commercially available and widely used thermo-mechanical model, Netfabb, was used to investigate the effects of multiple lasers for complex scan patterns such as raster, spiral, and Hilbert on the temperature distribution and thermal distortion. The results show that the thermal distortion is minimal for the spiral scan pattern. Additionally, multiple lasers were found to decrease the build time (as expected) while maintaining or reducing the thermal distortion compared with their single-laser counterparts for all scan patterns (except Hilbert). Therefore, the newly developed ML-PBF predictive model is capable of providing critical insights into the effects of using multiple lasers, thereby opening new possibilities for the faster production of complex parts. In the future, small-scale computational models will be expanded to include large-scale parts, and probabilistic models will be developed to establish correlations.

Machine learning for differentiation of lipid-poor adrenal adenoma and subclinical pheochromocytoma based on multiphase CT imaging radiomics

BackgroundThere is a paucity of research investigating the application of machine learning techniques for distinguishing between lipid-poor adrenal adenoma (LPA) and subclinical pheochromocytoma (sPHEO) based on radiomic features extracted from non-contrast and dynamic contrast-enhanced computed tomography (CT) scans of the abdomen.MethodsWe conducted a retrospective analysis of multiphase spiral CT scans, including non-contrast, arterial, venous, and delayed phases, as well as thin- and thick-thickness images from 134 patients with surgically and pathologically confirmed. A total of 52 patients with LPA and 44 patients with sPHEO were randomly assigned to training/testing sets in a 7:3 ratio. Additionally, a validation set was comprised of 22 LPA cases and 16 sPHEO cases from two other hospitals. We used 3D Slicer and PyRadiomics to segment tumors and extract radiomic features, respectively. We then applied T-test and least absolute shrinkage and selection operator (LASSO) to select features. Six binary classifiers, including K-nearest neighbor (KNN), logistic regression (LR), decision tree (DT), random forest (RF), support vector machine (SVM), and multi-layer perceptron (MLP), were employed to differentiate LPA from sPHEO. Receiver operating characteristic (ROC) curves and area under the curve (AUC) values were compared using DeLong’s method.ResultsAll six classifiers showed good diagnostic performance for each phase and slice thickness, as well as for the entire CT data, with AUC values ranging from 0.706 to 1. Non-contrast CT densities of LPA were significantly lower than those of sPHEO (P < 0.001). However, using the optimal threshold for non-contrast CT density, sensitivity was only 0.743, specificity 0.744, and AUC 0.828. Delayed phase CT density yielded a sensitivity of 0.971, specificity of 0.641, and AUC of 0.814. In radiomics, AUC values for the testing set using non-contrast CT images were: KNN 0.919, LR 0.979, DT 0.835, RF 0.967, SVM 0.979, and MLP 0.981. In the validation set, AUC values were: KNN 0.891, LR 0.974, DT 0.891, RF 0.964, SVM 0.949, and MLP 0.979.ConclusionsThe machine learning model based on CT radiomics can accurately differentiate LPA from sPHEO, even using non-contrast CT data alone, making contrast-enhanced CT unnecessary for diagnosing LPA and sPHEO.

Optimization of high-power short duration catheter radiofrequency ablation for pulmonary veins isolation in patients with artiral septial defect

Objective ‒ to perform the analysis and biophysical substantiation of a new technique of catheter radiofrequency ablation (RFA) with high power and short duration based on mathematical modeling of own clinical data of the electro-thermodynamic effect of RFA on the myocardium; to investigate the morphological characteristics of the myocardium in different areas of the atrium and to determine the morphometric parameters of the display on the electroanatomical model of the heart of the ablation zone in the EnSite Precision navigation system, necessary for effective and safe high-power and short-duration RFA.Materials and methods. Clinical studies were performed in Amosov National Institute of Cardiovascular Surgery NAMS of Ukraine. Specialized high-tech medical equipment was used for the objectivity of clinical data obtained and used in the work. Morphological characteristics of the myocardium (thickness of the wall of the left atrium, distance from the back wall of the heart to the esophagus, diameters of the pulmonary veins) were evaluated on the computed tomography images of the heart of the patients, which were obtained in the radiology department on a Toshiba device (Japan) using a spiral scanning. The morphometric parameters of the ablation zone, which were later used to evaluate the effectiveness of RFA and which formed the basis of standardized protocols for the operation, were determined for display on the electro-anatomical maps of the patients' hearts in the EnSite Precision system (Abbott, USA). Biophysical substantiation of the RFA technique with high power and short duration was performed using mathematical modeling of the electro-thermodynamic effect of RFA on the myocardium and own clinical data in the Comsol Multiphysics automated simulation of biophysical processes.Results. It is proposed for a group of patients with combined atrial fibrillation with an atrial septal defect to perform RFA using a new ablation technique with high power and short duration at one point of application of radio frequency energy. Achieving transmurality of ablation in a shorter time makes it possible to hold the electrode more precisely and stably in this area when isolating the pulmonary veins in a complex geometry and without support for the electrode in case of a defect. The morphological characteristics of the myocardium were studied and the morphometric parameters of the display on the electroanatomical heart model of the ablation zone, necessary for effective and safe RFA, were determined. These include: the diameter of the point-label of radiofrequency ablation on the anatomical model of the heart, which must correspond to the real data of the size of the destruction; the percentage of overlap of RFA points for the formation of an effective transmural line; estimated number of ablation points to standardize the evaluation of the effectiveness of the procedure.Conclusions. The conducted research made it possible to solve the current problems of catheter radiofrequency ablation in patients with atrial fibrillation and atrial septal defect, namely to increase the efficiency and safety of pulmonary vein isolation. Transmurality and integrity of the isolating line was achieved due to the determined morphological characteristics of the myocardium and the calculated morphometric parameters of the ablation zone. The obtained data are adapted to a real display visible to the surgeon on the electro-anatomical map of the heart in the EnSite Precision navigation system. This system is actively used in clinical practice, but it was necessary to optimize the clinical protocols of RFA with high power and short duration, which was achieved as a result of this work.

Hybrid spiral scanning in a double-clad fiber-based handheld confocal scanning light ophthalmoscope.

High-speed, accessible, and robust in vivo imaging of the human retina is critical for screening of retinal pathologies, such as diabetic retinopathy, age-related macular degeneration, and others. Scanning light ophthalmoscopy (SLO) is a retinal imaging modality that produces digital, en face images of the human retina with superior image gradability rates when compared to the current standard of care in screening for these diseases, namely the flood-illumination handheld fundus camera (HFC). However, current-generation commercial SLO systems are mostly tabletop devices, limiting their accessibility and utility in screening applications. Moreover, most existing SLO systems use raster scan patterns, which are both inefficient and lead to undesired subject gaze drift when used with visible or pseudo-visible illumination. Non-raster scan patterns, especially spiral scanning as described herein, promise advantages in both scan efficiency and reduced subject eye motion. In this work, we introduce a novel "hybrid spiral" scan pattern and the associated hardware design and real-time image reconstruction techniques necessary for its implementation in an SLO system. Building upon this core hybrid spiral scanning SLO (HSS-SLO) technology, we go on to present a complete handheld HSS-SLO system, featuring a fiber-coupled portable patient interface which leverages a dual-clad fiber (DCF) to form a single-path optical topology, thus ensuring mechanically robust co-alignment of illumination and collection apertures, a necessity for a handheld system. The feasibility of HSS-SLO for handheld, in vivo imaging is demonstrated by imaging eight human volunteers.

Consistency of spectral results in cardiac dual-source photon-counting CT

We evaluate stability of spectral results at different heart rates, acquisition modes, and cardiac phases in first-generation clinical dual-source photon-counting CT (PCCT). A cardiac motion simulator with a coronary stenosis mimicking a 50% eccentric calcium plaque was scanned at five different heart rates (0, 60–100 bpm) with the three available cardiac scan modes (high pitch prospectively ECG-triggered spiral, prospectively ECG-triggered axial, retrospectively ECG-gated spiral). Subsequently, full width half max (FWHM) of the stenosis, Dice score (DSC) for the stenosed region, and eccentricity of the non-stenosed region were calculated for virtual monoenergetic images (VMI) at 50, 70, and 150 keV and iodine density maps at both diastole and systole. FWHM averaged differences of − 0.20, − 0.28, and − 0.15 mm relative to static FWHM at VMI 150 keV across acquisition parameters for high pitch prospectively ECG-triggered spiral, prospectively ECG-triggered axial, and retrospectively ECG-gated spiral scans, respectively. Additionally, there was no effect of heart rate and acquisition mode on FWHM at diastole (p-values < 0.001). DSC demonstrated similarity among parameters with standard deviations of 0.08, 0.09, 0.11, and 0.08 for VMI 50, 70, and 150 keV, and iodine density maps, respectively, with insignificant differences at diastole (p-values < 0.01). Similarly, eccentricity illustrated small differences across heart rate and acquisition mode for each spectral result. Consistency of spectral results at different heart rates and acquisition modes for different cardiac phase demonstrates the added benefit of spectral results from PCCT to dual-source CT to further increase confidence in quantification and advance cardiovascular diagnostics.

Double spiral resonant MEMS scanning for ultra-high-speed miniaturized optical microscopy

Micro–electro–mechanical systems (MEMS)-based optical scanners play a vital role in the development of miniaturized optical imaging modalities. However, there is a longstanding challenge to balance the temporal resolution, field of view (FOV), and systematic fidelity. Here, we propose a double spiral scanning mechanism to enable high-frequency resonant scanning of MEMS scanners without sacrificing imaging quality, and offer a versatile imaging interface for applications in different scenarios. This arrangement, demonstrated by photoacoustic endoscopy, shows that the imaging rate and FOV can be improved by more than 60 and two times, respectively. The proposed method is general to address the limitations of MEMS-based scanning microscopies and can be adapted for various miniaturized imaging modalities, such as endoscopy, intraoperative image-guided surgery, and wearable devices.

An Effective Near-Field to Far-Field Transformation with Planar Spiral Scanning for Flat Antennas under Test.

The goal of this article is to provide numerical and experimental assessments of an effective near-field to far-field transformation (NF-FF T) technique with planar spiral scanning for flat antennas under test (AUTs), which requires a non-redundant, i.e., minimum, number of NF measurements. This technique has its roots in the theory of non-redundant sampling representations of electromagnetic fields and was devised by suitably applying the unified theory of spiral scans for non-volumetric antennas to the case in which the considered AUT is modeled by a circular disk having its radius equal to half of the AUT's maximum dimension. It makes use of a 2D optimal sampling interpolation (OSI) formula to accurately determine the massive amount of NF data required by the classical plane-rectangular NF-FF T technique from the non-redundant data gathered along the spiral. It must be emphasized that, when considering flat AUTs, the developed transformation allows one to further and significantly save measurement time as compared to that required by the previously developed NF-FF T techniques with planar spiral scans based on a quasi-planar antenna modeling, because the number of turns of the spiral and that of NF data to be acquired depend somewhat on the area of the modeling surface. The reported numerical simulations assess the accuracy of the proposed NF-FF T technique, whereas the experimental tests prove its practical feasibility.

Evaluation of the Relationship Between the Characteristics and Dimensions of Calcified Plaques and Coronary Artery Stenosis in Patients Undergoing Coronary Computed Tomography Angiography

Background: Despite the important role of coronary computed tomography angiography (CCTA) in determining the features of coronary atherosclerotic plaques, very few studies have investigated the role of plaque dimensions in the process of coronary artery obstruction. Therefore, this study aimed to assess the relationship between the characteristics and dimensions of calcified plaques and coronary artery stenosis using CCTA. Objectives: This study aimed to evaluate the relationship between calcified plaque dimensions and coronary artery stenosis in patients undergoing CCTA. Patients and Methods: This cross-sectional study was conducted on 211 plaques of candidate patients for prospective and retrospective electrocardiography (ECG)-gated CCTA, using spiral scanning at 120 kV. The length, width, thickness, and luminal areas of calcified plaques were assessed in all coronary arteries. Results: The mean rate of stenosis was estimated to be 56.1 ± 24.4%. The number of patients with stenosis &lt; 50% was 100 (47.3%). Stenosis had a significant relationship with the plaque luminal area and the luminal dimeter of the normal coronary artery proximal and distal to the plaque (P &lt; 0.05). However, there was no significant correlation between stenosis and normal luminal area (P &gt; 0.05). Meanwhile, a significant relationship was found between stenosis and the width and length of plaques (P &lt; 0.05). Conclusion: The present results indicated a significant association between stenosis and the width, length, and luminal area of plaques. It can be concluded that plaque dimensions are a predictive factor for stenosis.

Effect on Surface Properties of H13 Mold Steel Cladding Layer by Scanning Strategy

Laser cladding technology is used to clad the surface layer of H13 mold steel with Ni60A metal powder coating to solve the failure problem. The study used JMatPro software to extract and fit the thermophysical property parameters of the substrate and the clad material, and then used ANSYS APDL software to qualitatively analyze the distribution of melt pool morphology, nodal temperature versus time course curve and residual stress magnitude during the laser cladding process. Based on the results of the minimum residual stress in the cladding, reasonable scan paths were derived for the preparation of metal coatings on the surface layer of the die steel. The results show that the maximum peak temperature of the cladding process is 2515°C using short path scanning. The cladding layer can form a good metallurgical bond with the substrate at this temperature, with a stress of 406.68 MPa in the scanning direction and 284.45 MPa perpendicular to the scanning direction, which is significantly smaller than the residual stresses of other scanning methods. The residual stress values for the different strategies are from largest to smallest: spiral scan &gt; block scan &gt; long path scan &gt; short path scan.

Acoustic noise reduction for spiral MRI by gradient derating.

To show that the acoustic noise of spiral MRI can be reduced by derating the gradients with minimal penalty to image quality and scan time, and to illustrate an algorithm for optimal choice of derating parameters. Acoustic noise level was measured and compared for various values of maximum gradient amplitude and slew rate for T1 -weighted spin-echo spiral scans while maintaining image contrast, FOV and resolution, and readout time. A full gradient trajectory and a derated gradient (undersampled) trajectory were chosen for a volunteer scan followed by parallel imaging-aided reconstruction to illustrate comparable image SNR. Two auto-derating methods, which prioritize slew rate and gradient amplitude, respectively, were derived using analytical results from the WHIRLED PEAS variant of spiral waveforms and compared in their acoustic noise level under test use cases. Derating the gradients made the scan quieter by 16.6 dB(A) on average than a full gradient trajectory and required an undersampling factor R = 2 in order to maintain scan time, with no appreciable penalty in image SNR. Prioritizing reduced slew rate resulted in maximal loudness reduction. Scanner gradients can often be derated to reduce the acoustic noise for spiral MRI with minimal penalty in scan time and image quality with the help of parallel imaging. An automatic slew-priority derating method that maximizes loudness reduction is given.

Novel oviduct endoscope combining optical coherence tomography with intratubal ultrasonography for fallopian tube exploration: An in vivo rabbit pilot study

Background and study aimCurrently, several limitations exist in the examination of the oviduct. In this study, the usefulness and feasibility of a novel ultrafine dual-modality oviduct endoscopy device for in vivo assessment of the oviduct were evaluated. MethodsFive Japanese white rabbits were selected to undergo oviduct probing using a combination of optical coherence tomography (OCT) and intratubal ultrasonography. The feasibility of the procedure was evaluated through 152 pairs of clear, clinically interpretable images obtained using spiral scanning via the pull-back method. OCT images were compared with the oviduct histopathology sections. ResultsVisualization of the oviduct using both OCT and ultrasound revealed a differentiated three-layer tissue; however, ultrasound showed a poorer clarity than OCT. By comparing OCT images with the histological morphology of the oviduct, the inner low-reflective layer of the oviduct corresponds to the mucosal layer, the middle high-reflective layer corresponds to the fibrous muscle layer, and the outer low-reflective layer corresponds to the connective tissue layer. Postoperatively, the general condition of the animals was good. ConclusionThis study demonstrated the feasibility and potential clinical value of the novel ultrafine dual-modality oviduct endoscope. Dual-modality imaging of OCT and intratubal ultrasonography can provide clearer microstructure of the oviduct wall.

Geometrically accurate real-time volumetric visualization of the middle ear using optical coherence tomography.

We introduce a novel system for geometrically accurate, continuous, live, volumetric middle ear optical coherence tomography imaging over a field of view (FOV) from a handheld imaging probe. The system employs a discretized spiral scanning (DC-SC) pattern to rapidly collect volumetric data and applies real-time scan conversion and lateral angular distortion correction to reduce geometric inaccuracies to below the system's lateral resolution over 92% of the FOV. We validate the geometric accuracy of the resulting images through comparison with co-registered micro-computed tomography (micro-CT) volumes of a phantom target and a cadaveric middle ear. The system's real-time volumetric imaging capabilities are assessed by imaging the ear of a healthy subject while performing dynamic pressurization of the middle ear in a Valsalva maneuver.

Curved Synthetic Aperture Radar for Near-Field Terahertz Imaging

High resolution imaging technique will play an essential role in the future smart imaging applications to provide potential solutions for accurate detection, monitoring and classification of the target. The potential of synthetic aperture radar (SAR) systems to acquire high resolution images has opened new frontiers and led to its exploration in new applications. The conventional microwave radar imaging suffers limited range resolution in the sub-millimeter wave range and optical imaging methods are constrained by the diffraction limit. In the terahertz (THz) regime of the spectrum, the SAR systems could be operated in all the weather, all the time and are capable of penetrating through clouds, smoke, dust etc. to achieve high resolution images beyond the diffraction limit. The curved SAR presents a SAR system created by circularly encircling the target scene. The Circular SAR and Spiral SAR which are based on a circular and cylindrical spiral scanning trajectory, respectively are the scanning methods used for curved SAR. In this paper, we have explored a new toolbox that enables the rapid development of near-field THz-SAR imaging systems and generation of large near-field THz imaging scenarios with the goal to support and facilitate data driven research such as deep learning in the THz community through synthetically generated SAR images as well as its potential for THz based high resolution and 2D/3D near-field imaging application. Initially, the potential advantages of THz-SAR over Microwave SAR and optical imaging methods are presented. Further, a frequency modulated continuous wave (FMCW) radar testbed is simulated in multi-input multi-output (MIMO) configuration for the target frequency band. Moreover, the circular and cylindrical SAR scanning methods are explored for near-field imaging of point targets to obtain 2D and 3D THz-SAR images, respectively. Also, the radar images are reconstructed using the Back Propagation and Polar Formatting Algorithms, focusing on short range applications like indoor environments. Finally, the SAR performance evaluation metrics are reported and a roadmap for future work is presented.