Group feature selection for enhancing information gain in MRI reconstruction

Magnetic resonance imaging (MRI) has revolutionized the radiology. As a leading medical imaging modality, MRI not only visualizes the structures inside body, but also produces functional imaging. However, due to the slow imaging speed constrained by the MR physics, MRI cost is expensive, and patient may feel not comfortable in a scanner for a long time. Parallel MRI has accelerated the imaging speed through the sub-Nyquist sampling strategy and the missing data are interpolated by the multiple coil data acquired. Kernel learning has been used in the parallel MRI reconstruction to learn the interpolation weights and re-construct the undersampled data. However, noise and aliasing artifacts still exist in the reconstructed image and a large number of auto-calibration signal lines are needed. To further improve the kernel learning-based MRI reconstruction and accelerate the speed, this paper proposes a group feature selection strategy to improve the learning performance and enhance the reconstruction quality. An explicit kernel mapping is used for selecting a subset of features which contribute most to estimate the missing k-space data. The experimental results show that the learning behaviours can be better predicted and therefore the reconstructed image quality is improved.

An Imaging Enhancement Method for a Terahertz Rotation Mirror Imaging System Based on a Scale-Recurrent Network

The terahertz (THz) rotation mirror imaging system is an alternative to the THz array imaging system. A THz rotation mirror imaging system costs less than a THz array imaging system, while the imaging speed of a THz rotation mirror imaging system is much higher than the imaging speed of a THz raster-scan imaging system under the same hardware conditions. However, there is some distortion in the THz image from the THz rotation mirror imaging system. The distortion, which makes images from the THz rotation mirror imaging system difficult to identify, results from the imaging principle of the THz rotation mirror imaging system. In this article, a method based on the scale-recurrent network (SRN) is put in place to correct the distortion. A comparison between distorted THz images and corrected images shows that the proposed method significantly increases the structural similarity between the THz images and the samples.

Recent trends in AFM imaging speed and improvement methods

: Atomic Force Microscope (AFM) has become the primary tool for observation and manipulation in nanotechnology research due to its nano-meter high resolution. However, the slow imaging speed is one of the critical reasons hindering the further development of AFM. This article first introduces the applications of AFM in cell biology in recent years, then expresses the importance of rapid imaging in cell biology, and finally summarizes the reasons affecting the imaging speed of AFM from three aspects: the limited bandwidth of system mechanical components, obvious inherent characteristics of piezoelectric scanners, and complex image processing algorithms. The improvement and optimization methods of mechanical parts or structure, control algorithm, and image processing are reviewed for different influence reasons. Then, the advantages of different improvement methods and improved imaging speed are discussed, and imaging quality improvement effects are compared. Imaging speed and resolution both are much higher than before while ensuring image quality without damaging the samples. This review aims to enable students, the public, and even experts of different knowledge backgrounds to learn directly and select realizable improvement method according to realistic conditions. Finally, the future development trend and further prospects of high-speed AFM are discussed.

Consequences of the Nyquist-Shannon sampling criterion in Mesoscopic Multiphoton Microscopy to avail full-field sub-micron resolution resolvability

With a limited effective voxel rate, to date, each laser-scanning mesoscopic multiphoton microscope (MPM), despite securing an ultra-large field of view (FOV) and an ultra-high optical resolution simultaneously, experiences a fundamental issue with digitization; i.e., inability to satisfy the Nyquist-Shannon sampling criterion to resolve the optics-limited sub-micron resolution over the whole FOV. Such a system either neglects the criterion degrading the digital resolution to twice the pixel size, or significantly reduces the imaging area and/or the imaging speed to respect the digitization. Here we introduce a Nyquist figure of merit parameter to assess this issue, further to comprehend a maximum aliasing-free FOV and a cross-over excitation wavelength for a laser scanning MPM system. Based on our findings we demonstrate an ultra-high voxel rate acquisition in a custom-built mesoscopic MPM system to exceed the Nyquist-rate for a >3800 FOV-resolution ratio while not compromising the imaging speed as well as the photon-budget.

Author Correction: Improvement of nerve imaging speed with coherent anti-Stokes Raman scattering rigid endoscope using deep-learning noise reduction

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Hardware Considerations for Preclinical Magnetic Resonance of the Kidney

Magnetic resonance imaging (MRI) is a noninvasive imaging technology that offers unparalleled anatomical and functional detail, along with diagnostic sensitivity. MRI is suitable for longitudinal studies due to the lack of exposure to ionizing radiation. Before undertaking preclinical MRI investigations of the kidney, the appropriate MRI hardware should be carefully chosen to balance the competing demands of image quality, spatial resolution, and imaging speed, tailored to the specific scientific objectives of the investigation. Here we describe the equipment needed to perform renal MRI in rodents, with the aim to guide the appropriate hardware selection to meet the needs of renal MRI applications.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This chapter on hardware considerations for renal MRI in small animals is complemented by two separate publications describing the experimental procedure and data analysis.

Two-photon microscopy at >500 volumes/second

We demonstrate a multi-focal multi-photon volumetric microscopy via combination of 32-beam parallel lateral-scanning, a 70-kHz axial-scanning acoustic lens, and a 32-channel photodetector, enabling unprecedented data rate (2-10 GHz) and >500-volumes/second imaging speed over ~200×200×200-μm3.

High-Resolution, Large Field-of-View, and Multi-View Single Objective Light-Sheet Microscopy

Light-sheet microscopy has become the preferred method for long-term imaging of large living samples because of its low photo-invasiveness and good optical sectioning capabilities. Unfortunately, refraction and scattering often pose obstacles to light-sheet propagation and limit imaging depth. This is typically addressed by imaging multiple complementary views to obtain high and uniform image quality throughout the sample. However, multi-view imaging often requires complex multi-objective configurations that complicate sample mounting, or sample rotation that decreases imaging speed. Recent developments in single-objective light-sheet microscopy have shown that it is possible to achieve high spatio-temporal resolution with a single objective for both illumination and detection. Here we describe a single-objective light-sheet microscope that achieves: (i) high-resolution and large field-of-view imaging via a custom remote focusing objective; (ii) simpler design and ergonomics by remote placement of coverslips; (iii) fast volumetric imaging by means of light-sheet stabilised stage scanning – a novel scanning modality that extends the imaging volume without compromising imaging speed nor quality; (iv) multi-view imaging by means of dual orthogonal light-sheet illumination. Finally, we demonstrate the speed, field of view and resolution of our novel instrument by imaging zebrafish tail development.