Single-shot Imaging Research Articles

A straightforward approach for 3D single-shot arterial spin labeling-based brain perfusion imaging: Preventing artifacts due to signal fluctuations.

The present work aims to evaluate the performance of three-dimensional (3D) single-shot stack-of-spirals turbo FLASH (SOS-TFL) acquisition for pseudo-continuous arterial spin labeling (PCASL) and velocity-selective ASL (VSASL)-based cerebral blood flow (CBF) mapping, as well as VSASL-based cerebral blood volume (CBV) mapping. Digital phantom simulations were conducted for both multishot echo planar imaging and spiral trajectories with intershot signal fluctuations. PCASL-derived CBF (PCASL-CBF), VSASL-derived CBF (VSASL-CBF), and CBV (VSASL-CBV) were all acquired using 3D multishot gradient and spin-echo and SOS-TFL acquisitions following background suppression. Both simulation and in vivo images were compared between multishot and single-shot compressed sensing-regularized sensitivity encoding (CS-SENSE) reconstructions. Artifacts were observed in both simulated multishot echo planar imaging and spiral readouts, as well as in in vivo multishot ASL perfusion images. A high correlation was found between the levels of signal fluctuations among interleaves and the severity of artifacts in both simulated and in vivo data. Image artifacts were more apparent in the inferior region of the brain, especially in CBF scans. These artifacts were effectively eliminated when single-shot CS-SENSE reconstruction was applied to the same data set. ASL images obtained from 3D segmented gradient and spin-echo or SOS-TFL acquisitions can exhibit artifacts caused by signal fluctuations among different shots, which persist even after the application of background suppression pulses. In contrast, these artifacts were prevented when single-shot CS-SENSE reconstruction was applied to the same SOS-TFL data set.

Squared diffusion-weighted imaging for improving the detection of clinically significant prostate cancer

Aim of this study was to proof the concept of optimizing the contrast between prostate cancer (PC) and healthy tissue by DWI post-processing using a quadrature method. DWI post-processing was performed on 30 patients (median age 67 years, prostate specific antigen 8.0 ng/ml) with PC and clear MRI findings (PI-RADS 4 and 5). Multiparametric MRI was performed at 3 Tesla. A multi-shot readout segmentation (rs-EPI) plus zoomed single-shot imaging (z-EPI) sequence was used in 15 patients (group 1) and a single-shot echo-planar imaging (ss-EPI) plus rs-EPI sequence in 15 patients (group 2). B-value images (b1000 and b1800/2000) were squared and then evaluated objectively software-based and subjectively using a 5-point. The squared DWI technique showed a significantly higher contrast ratio (CR) for ss-EPI b1800 (p < 0.001), rs-EPI b1000 (p < 0.001), rs-EPI b1800 (p < 0.001), z-EPI b1000 (p = 0.008) and for z-EPI b2000 (p < 0.001). After post-processing, a significant improvement in the subjective assessment of image quality was observed for rs-EPI b1000 (p < 0.001), rs-EPI b1800 (p < 0.001) and z-EPI b1000 (p < 0.001). The application of the square post-processing to DWI results in a significant improvement in the CR between PC and healthy tissue, especially at high b-values of ss-EPI or re-EPI. This method may help to improve the detection and differentiation of PC lesions.

Single-shot Digital Image Correlation-assisted Digital Holography for Simultaneous 3D Shape and Displacement Measurement

Single-shot Digital Image Correlation-assisted Digital Holography for Simultaneous 3D Shape and Displacement Measurement

Adaptive focusing optical coherence tomography for corneal imaging.

Optical coherence tomography (OCT) plays a crucial role in diagnosing corneal diseases due to its capacity to provide high-resolution three-dimensional imaging. However, the convex shape of the cornea and the inherent trade-off between depth of field (DOF) and lateral resolution in OCT systems often result in defocusing issues, leading to reduced lateral resolution and sensitivity in single-shot high-resolution imaging. Traditional methods typically involve multiple focusing at different depths followed by image stitching to achieve full-depth high-resolution imaging of the cornea, which increases imaging times and introduces potential stitching artifacts. To address these limitations, we propose a novel adaptive focusing OCT system. By leveraging the symmetry of the corneal structure and the periodic focusing stability of an electrically tunable lens, our system can achieve full-depth high-resolution imaging of the entire cornea in a single scan, covering an 11 mm imaging range and 1.5 mm depth variation with a lateral resolution of 10 µm. This approach not only halves the imaging time but also eliminates the need for image stitching. Imaging of curved tape samples and excised porcine corneas demonstrates the potential of this novel technique for high-resolution and fast corneal imaging.

Advanced Quantitative Phase Microscopy Achieved with Spatial Multiplexing and a Metasurface.

Quantitative optical phase information provides an alternative method to observe biomedical properties, where conventional phase imaging fails. Phase retrieval typically requires multiple intensity measurements and iterative computations to ensure uniqueness and robustness against detection noise. To increase the measurement speed, we propose a single-shot quantitative phase imaging method with metasurface optics that can be conveniently integrated into conventional imaging systems with minimal modification. The improvement of the measurement speed is simultaneously made possible by combining deep learning with the transport-of-intensity equation. As a proof-of-concept, we demonstrate phase retrieval on both calibrated phase objects and biological specimens by using an imaging system integrated with our metasurface. When combined with the matched neural network, the system yields result with errors as low as 5% and increased space-bandwidth-product. A multitude of commercial applications can benefit from the compactness and rapid implementation of our proposed method.

Phantom-based gradient waveform measurements with compensated variable-prephasing: Description and application to EPI at 7 T.

Introducing compensated variable-prephasing (CVP), a phantom-based method for gradient waveform measurements. The technique is based on the variable-prephasing (VP) method, but takes into account the effects of all gradients involved in the measurement. We conducted measurements of a trapezoidal test gradient and of an EPI readout gradient train with three approaches: VP, CVP, and fully compensated variable-prephasing (FCVP). We compared them to one another and to predictions based on the gradient system transfer function. Furthermore, we used the measured and predicted EPI gradients for trajectory corrections in phantom images on a 7 T scanner. The VP gradient measurements are confounded by lingering oscillations of the prephasing gradients, which are compensated in the CVP and FCVP measurements. FCVP is vulnerable to a sign asymmetry in the gradient chain. However, the trajectories determined by all three methods resulted in comparably high EPI image quality. We present a new approach allowing for phantom-based gradient waveform measurements with high precision, which can be useful for trajectory corrections in non-Cartesian or single-shot imaging techniques. In our experimental setup, the proposed "compensated variable-prephasing" method provided the most reliable gradient measurements of the different techniques we compared.

Broadband spectropolarimetry based on single-shot intensity images of polychromatic structured vector beams

Broadband spectropolarimetry based on single-shot intensity images of polychromatic structured vector beams

Single-shot Compressive Hyperspectral Imaging Utilizing Both Positive and Negative Diffracted Waves

Single-shot Compressive Hyperspectral Imaging Utilizing Both Positive and Negative Diffracted Waves

Compact single-shot multispectral polarization imager through joint spectral-polarization encoding.

The technique of spectral polarization imaging (SPI) is a potent detection tool in various fields due to its ability to capture multi-dimensional information. However, existing SPI systems usually face challenges associated with architectural complexity and computational requirements, rendering them unsuitable for handheld, on-board, and real-time applications. Consequently, a compact single-shot multispectral polarization imager (CSMPI) is proposed, which employs a combined spectral-polarization encoding strategy to address the aforementioned issues. It incorporates a coded aperture for encoding multiple spectral channels together with linear polarization into a single measurement, enabling the simultaneous detection of up to nine light components with just one exposure. The resulting prototype consists solely of a color polarization detector and an imaging lens inserted with the small and easily fabricable coded aperture, which features compact dimensions of Φ5.5 cm × 21.5 cm and a light weight of approximately 670 g. This is particularly advantageous for application areas that require system miniaturization and rapid multi-dimensional detection.

Information merging and reconstruction of single-shot dual-mode wide-field imaging with high spatial resolution

In many scenarios, it is really desirable but challenging for wide-field imaging to gather both the clear morphologies and fine details of the target. This paper realizes this imaging by a dual-mode imaging on optical parametric amplification (OPA) with a vortex laser pump. This design includes signal imaging and idler imaging, which have complementary point spread functions with each other. The signal acts as bright-field imaging to record morphologic information, whereas the idler does so for spiral phase contrast imaging to capture the featured details with high brightness and contrast, which has been experimentally confirmed with a target of herb tissue. By utilizing the coupling relation among the pump, signal, and idler, the information from the recorded signal and idler images can be merged, which allows us to reconstruct the target picture owning both high-contrast morphologies and high-brightness fine details. Due to high OPA gain, our imaging can work with weak illumination. Its field-of-view covers an area of 0.33 × 0.33 mm2 with a spatial resolution up to 228 lp/mm. This OPA imaging also provides an effective way for the imaging required nonlinear frequency conversion.

Transformer-guided exposure-aware fusion for single-shot HDR imaging

Transformer-guided exposure-aware fusion for single-shot HDR imaging

Bridging the gap: A slice-to-volume registration technique for converting 2D single-shot LGE images into 3D volumetric data

Bridging the gap: A slice-to-volume registration technique for converting 2D single-shot LGE images into 3D volumetric data

Free-breathing single-shot late gadolinium enhancement imaging with variable inversion time (vTI LGE) for imaging of scar and lipomatous metaplasia

Free-breathing single-shot late gadolinium enhancement imaging with variable inversion time (vTI LGE) for imaging of scar and lipomatous metaplasia

Investigating MRI-Associated Biological Aspects of Racial Disparities in Prostate Cancer for African American and White Men.

Understanding the characteristics of multiparametric MRI (mpMRI) in patients from different racial/ethnic backgrounds is important for reducing the observed gaps in clinical outcomes. To investigate the diagnostic performance of mpMRI and quantitative MRI parameters of prostate cancer (PCa) in African American (AA) and matched White (W) men. Retrospective. One hundred twenty-nine patients (43 AA, 86 W) with histologically proven PCa who underwent mpMRI before radical prostatectomy. 3.0 T, T2-weighted turbo spin echo imaging, a single-shot spin-echo EPI sequence diffusion-weighted imaging, and a gradient echo sequence dynamic contrast-enhanced MRI with an ultrafast 3D spoiled gradient-echo sequence. The diagnostic performance of mpMRI in AA and W men was assessed using detection rates (DRs) and positive predictive values (PPVs) in zones defined by the PI-RADS v2.1 prostate sector map. Quantitative MRI parameters, including Ktrans and ve of clinically significant (cs) PCa (Gleason score ≥ 7) tumors were compared between AA and W sub-cohorts after matching age, prostate-specific antigen (PSA), and prostate volume. Weighted Pearson's chi-square and Mann-Whitney U tests with a statistically significant level of 0.05 were used to examine differences in DR and PPV and to compare parameters between AA and matched W men, respectively. A total number of 264 PCa lesions were identified in the study cohort. The PPVs in the peripheral zone (PZ) and posterior prostate of mpMRI for csPCa lesions were significantly higher in AA men than in matched W men (87.8% vs. 68.1% in PZ, and 89.3% vs. 69.6% in posterior prostate). The Ktrans of index csPCa lesions in AA men was significantly higher than in W men (0.25 ± 0.12 vs. 0.20 ± 0.08 min-1; P < 0.01). This study demonstrated race-related differences in the diagnostic performances and quantitative MRI measures of csPCa that were not reflected in age, PSA, and prostate volume. 3 TECHNICAL EFFICACY: Stage 2.

Comparisons of integrated slice-specific dynamic shimming EPI and single-shot EPI diffusion-weighted imaging of the liver.

To compare the quality of DWI images, signal loss of left hepatic lobe and diagnostic performance of apparent diffusion coefficient (ADC) values between SS-EPI and iShim-EPI in liver lesions. Totally 142 patients were involved, images using SS-EPI and the prototype iShim-EPI were acquired before injection of gadoxetic acid-enhanced liver MRI.Image quality of demarcation of liver capsule, resolution, lesion distortion, artifacts, lesion confidence score, and signal loss in left hepatic lobe was assessed by two radiologists. Mean ADC values of the largest lesions were measured, and the correlations, agreements, and diagnostic performances were compared between the two sequences. Image quality of the iShim-EPI was significantly improved over that of SS-EPI (ICC 0.843 to 0.991, p<0.05), the signal loss in the left hepatic lobe was greatly reduced. The ADC values were highly correlated (r=0.93, p<0.001) and had good agreement (CI -475.5∼722.1×10-6 mm2/s) between the two sequences. Compared with SS-EPI,iShim-EPI had better performance in detecting benign (hepatic haemangioma and cyst) and malignant (primary liver cancer and hepatic metastases) diseases. Furthermore, iShim-EPI had a significantly larger AUC in differentiating cancer from benign lesions (both hepatic haemangioma and cyst) (p<0.05). IShim-EPI DWI is a promising method for differentiating benign and malignant liver lesions with better image quality, less signal loss of left hepatic lobe and could enhance the confidence of diseases diagnosis compared with SS-EPI.

Feasibility/clinical utility of half-Fourier single-shot turbo spin echo imaging combined with deep learning reconstruction in gynecologic magnetic resonance imaging.

When antispasmodics are unavailable, the periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER; called BLADE by Siemens Healthineers) or half Fourier single-shot turbo spin echo (HASTE) is clinically used in gynecologic MRI. However, their imaging qualities are limited compared to Turbo Spin Echo (TSE) with antispasmodics. Even with antispasmodics, TSE can be artifact-affected, necessitating a rapid backup sequence. This study aimed to investigate the utility of HASTE with deep learning reconstruction and variable flip angle evolution (iHASTE) compared to conventional sequences with and without antispasmodics. This retrospective study included MRI scans without antispasmodics for 79 patients who underwent iHASTE, HASTE, and BLADE and MRI scans with antispasmodics for 79 case-control matched patients who underwent TSE. Three radiologists qualitatively evaluated image quality, robustness to artifacts, tissue contrast, and uterine lesion margins. Tissue contrast was also quantitatively evaluated. Quantitative evaluations revealed that iHASTE exhibited significantly superior tissue contrast to HASTE and BLADE. Qualitative evaluations indicated that iHASTE outperformed HASTE in overall quality. Two of three radiologists judged iHASTE to be significantly superior to BLADE, while two of three judged TSE to be significantly superior to iHASTE. iHASTE demonstrated greater robustness to artifacts than both BLADE and TSE. Lesion margins in iHASTE had lower scores than BLADE and TSE. iHASTE is a viable clinical option in patients undergoing gynecologic MRI with anti-spasmodics. iHASTE may also be considered as a useful add-on sequence in patients undergoing MRI with antispasmodics.

Incoherent light interferometer for single-shot, dual wavelength, areal topography measurements of a reflective surface.

This paper introduces an interferometer for single-shot areal quantitative phase imaging at two wavelengths simultaneously, suitable for use with low coherence sources. It operates in reflection geometry with on-axis illumination, so that it can be conveniently applied to surface texture measurements. The system consists of two identical 4f systems forming the reference and sample arm. The reference arm is terminated by an optical assembly consisting of a dichroic mirror and two diffraction gratings, providing two separate dispersed off-axis reference beams. Two sets of distinct, separable interference fringes allow the use of the synthetic wavelength technique to obtain an extended unambiguous range of measurement recorded in a single frame. The implementation presented here was operating with superluminescent diode (SLED) sources with central wavelengths of 757 nm and 841 nm, giving a theoretical unambiguous range of 3.79 µm. The system was experimentally tested by measuring a sample with a 1 µm deep groove in electroformed nickel. The result shows good agreement with a contact stylus profiler measurement, although further work is needed to limit the noise in the interference signals.

V-shaped PSF for 3D imaging over an extended depth of field in wide-field microscopy.

Single-shot 3D optical microscopy that can capture high-resolution information over a large volume has broad applications in biology. Existing 3D imaging methods using point-spread-function (PSF) engineering often have limited depth of field (DOF) or require custom and often complex design of phase masks. We propose a new, to the best of our knowledge, PSF approach that is easy to implement and offers a large DOF. The PSF appears to be axially V-shaped, engineered by replacing the conventional tube lens with a pair of axicon lenses behind the objective lens of a wide-field microscope. The 3D information can be reconstructed from a single-shot image using a deep neural network. Simulations in a 10× magnification wide-field microscope show the V-shaped PSF offers excellent 3D resolution (<2.5 µm lateral and ∼15 µm axial) over a ∼350 µm DOF at a 550 nm wavelength. Compared to other popular PSFs designed for 3D imaging, the V-shaped PSF is simple to deploy and provides high 3D reconstruction quality over an extended DOF.

Geometric phases arising from strong measurements of weak values

Abstract Geometric phases and weak values (WVs) are two fundamental concepts that were originally introduced in the realm of quantum mechanics. In the course of time, it became clear that the two concepts apply in both the quantum domain and the classical domain. Moreover, the two concepts proved to be intimately connected with one another, as disclosed by Sjöqvist some years ago (Sjöqvist 2006 Phys. Lett. A 359 187). WVs were so named in reference to very weak couplings between a system’s observable, e.g. light polarization, and its measuring device, the ‘pointer’. However, the actual definition of WVs does not involve the system-pointer coupling strength. We have addressed the strong coupling regime both theoretically and experimentally, thereby obtaining geometric phases out of WVs. We report experimental results as a proof-of-concept, using classical light beams and single-shot images. Our approach applies without essential modifications also to single photons.

Half-pixel sliding window processing for fourfold resolution improvement on single-shot quantitative phase imaging with polarization cameras

Half-pixel sliding window processing for fourfold resolution improvement on single-shot quantitative phase imaging with polarization cameras