Modified-cs-residual for Recursive Reconstruction of Highly Undersampled Functional MRI Sequences

Functional magnetic resonance imaging(fMRI) is a non-invasive technique to investigate brain function. It is done by inferring the neural activity by acquiring the MR images when the subject is provided with controllable stimulus. Like other MR techniques, fMRI provides high quality images while suffering the burden of slow data acquisition time and thus the sacrifice in the spatial\temporal resolution. In MR imaging, the scan time is roughly proportional to the number of measurements, therefore sampling fewer measurements can reduce the acquisition time. The recent theory of compressive sensing (CS) states that under certain conditions, images with a sparse representation can be recovered from randomly undersampled measurements. In this dissertation, we propose a recursive sparse reconstruction algorithm to causally reconstruct fMRI sequence from a limited number of measurements. The proposed solution modified-CS-residual uses the time correlation between the image sequences in two novel ways: (a) it uses the fact that the sparsity pattern changes slowly over the time and (b) it also uses the fact that the significant nonzero signal\pixel values also changes slowly. We also demonstrate that our solution provides a very fast and accurate reconstruction while using only about 30% measurements per frame. Extensive experiment results also show the adaptability of modified- CS-residual to different types of blood oxygenation level dependence (BOLD) contrast signals. As a result, our proposed modified-CS-residual can causally reconstruct fMRI sequences and significantly reduce the image acquisition time to enable higher spatial and temporal resolution, which is of great practical use in rapid and dynamic fMRI

Nonlinear asymptotic stability and transition threshold for 2D Taylor-Couette flows in Sobolev spaces

In this paper, we investigate the stability of the 2-dimensional (2D) Taylor-Couette (TC) flow for the incompressible Navier-Stokes equations. The explicit form of velocity for 2D TC flow is given by $u=(Ar+\frac{B}{r})(-\sin \theta, \cos \theta)^T$ with $(r, \theta)\in [1, R]\times \mathbb{S}^1$ being an annulus and $A, B$ being constants. Here, $A, B$ encode the rotational effect and $R$ is the ratio of the outer and inner radii of the annular region. Our focus is the long-term behavior of solutions around the steady 2D TC flow. While the laminar solution is known to be a global attractor for 2D channel flows and plane flows, it is unclear whether this is still true for rotating flows with curved geometries. In this article, we prove that the 2D Taylor-Couette flow is asymptotically stable, even at high Reynolds number ($Re\sim \nu^{-1}$), with a sharp exponential decay rate of $\exp(-\nu^{\frac13}|B|^{\frac23}R^{-2}t)$ as long as the initial perturbation is less than or equal to $\nu^\frac12 |B|^{\frac12}R^{-2}$ in Sobolev space. The powers of $\nu$ and $B$ in this decay estimate are optimal. It is derived using the method of resolvent estimates and is commonly recognized as the enhanced dissipative effect. Compared to the Couette flow, the enhanced dissipation of the rotating Taylor-Couette flow not only depends on the Reynolds number but also reflects the rotational aspect via the rotational coefficient $B$. The larger the $|B|$, the faster the long-time dissipation takes effect. We also conduct space-time estimates describing inviscid-damping mechanism in our proof. To obtain these inviscid-damping estimates, we find and construct a new set of explicit orthonormal basis of the weighted eigenfunctions for the Laplace operators corresponding to the circular flows. These provide new insights into the mathematical understanding of the 2D Taylor-Couette flows.Comment: 50 page

Dosimetric Performance and Planning/Delivery Efficiency of a Dual-Layer Stacked and Staggered MLC on Treating Multiple Small Targets: A Planning Study Based on Single-Isocenter Multi-Target Stereotactic Radiosurgery (SRS) to Brain Metastases.

Purpose: To evaluate the dosimetric performance and planning/delivery efficiency of a dual-layer MLC system for treating multiple brain metastases with a single isocenter. Materials and Methods: 10 patients each with 6-10 targets with volumes from 0.11 to 8.57 cc, and prescription doses from 15 to 24 Gy, were retrospectively studied. Halcyon has only coplanar delivery mode. Halcyon V1 MLC modulates only with the lower layer at 1 cm resolution, whereas V2 MLC modulates with both layers at an effective resolution of 0.5 cm. For each patient five plans were compared varying MLC and beam arrangements: the clinical plan using multi-aperture dynamic conformal arc (DCA) and non-coplanar arcs, Halcyon-V1 using coplanar-VMAT, Halcyon-V2 using coplanar-VMAT, HDMLC-0.25 cm using coplanar-VMAT, and HDMLC-0.25 cm using non-coplanar-VMAT. All same-case plans were generated following the same planning protocol and normalization. Conformity index (CI), gradient index (GI), V12Gy, V6Gy, V3Gy, and brain mean dose were compared. Results: All VMAT plans met clinical constraints for critical structures. For targets with diameter \u3c 1 cm, Halcyon plans showed inferior CI among all techniques. For targets with diameter \u3e1 cm, Halcyon VMAT plans had CI similar to non-coplanar VMAT plans, and better than non-coplanar clinical DCA plans. For GI, Halcyon MLC plans performed similarly to coplanar HDMLC plans and inferiorly compared to non-coplanar HDMLC plans. All coplanar VMAT plans (Halcyon MLC and HDMLC) and clinical DCA plans had similar V12Gy, but were inferior compared to non-coplanar VMAT plans. Halcyon plans had slightly reduced V3Gy and mean brain dose compared to HDMLC plans. The difference between Halcyon V1 and V2 is only significant in CI of tumors less than 1cm in diameter. Halcyon plans required longer optimization than Truebeam VMAT plans, but had similar delivery efficiency. Conclusion: For targets with diameter \u3e1 cm, Halcyon\u27s dual-layer stacked and staggered MLC is capable of producing similar dose conformity compared to HDMLC while reducing low dose spill to normal brain tissue. GI and V12Gy of Halcyon MLC plans were, in general, inferior to non-coplanar DCA or VMAT plans using HDMLC, likely due to coplanar geometry and wider MLC leaves. HDMLC maintained its advantage in CI for smaller targets with diameter \u3c1 cm. © 2019 Li, Irmen, Liu, Shi, Alonso-Basanta, Zou, Teo, Metz and Dong

Adaptive Kaczmarz method for cardiac activity reconstruction in electrical impedance tomography

An adaptive Kaczmarz method to reconstruct conductivity changes from 2D EIT data is described. The framework to combine the adaptive Kaczmarz method and the adaptive mesh refinement is also outlined in the paper. Reconstructions from data collected on a human chest torso are shown. The results accurately recover the conductivity changes during a cardiac cycle and demonstrate the reconstruction performance of the adaptive Kaczmarz method

A real-world study of antifibrotic drugs-related adverse events based on the United States food and drug administration adverse event reporting system and VigiAccess databases

Objectives: This study aims to investigate adverse events (AEs) and adverse drug reactions (ADRs) associated with pirfenidone and nintedanib, two antifibrotic drugs used to treat idiopathic pulmonary fibrosis (IPF).Methods: Reporting odds ratio (ROR) and proportional reporting ratio (PRR) analyses were conducted to assess the association between these drugs and signals at both the preferred term (PT) and system organ class (SOC) levels.Results: 55,949 reports for pirfenidone and 35,884 reports for nintedanib were obtained from the FAERS database. The VigiAccess database provided 37,187 reports for pirfenidone and 23,134 reports for nintedanib. Male patients and individuals over the age of 65 were more likely to report AEs. Gastrointestinal disorders emerged as the most significant signal at SOC level for both drugs. Furthermore, nausea, diarrhoea, and decreased appetite were observed at the PT level. We further identified notable signals, including hemiplegic migraine for pirfenidone and asthenia, constipation, and flatulence for nintedanib, which were previously unknown or underestimated ADRs.Conclusion: This study has identified AEs and ADRs associated with pirfenidone and nintedanib, confirming that the majority of the corresponding label information indicates relative safety. However, it is essential to take unexpected risk signals seriously, necessitating further research to manage the safety profiles of these drugs

High-Capacity, Dendrite-Free, and Ultrahigh-Rate Lithium-Metal Anodes Based on Monodisperse N-Doped Hollow Carbon Nanospheres

To unlock the great potential of lithium metal anodes for high-performance batteries, a number of critical challenges must be addressed. The uncontrolled dendrite growth and volume changes during cycling (especially, at high rates) will lead to short lifespan, low Coulombic efficiency (CE), and security risks of the batteries. Here it is reported that Li metal anodes, employing the monodisperse, lithiophilic, robust, and large-cavity N-doped hollow carbon nanospheres (NHCNSs) as the host, show remarkable performances—high areal capacity (10 mAh cm−2), high CE (up to 99.25% over 500 cycles), complete suppression of dendrite growth, dense packing of Li anode, and an extremely smooth electrode surface during repeated Li plating/stripping. In symmetric cells, a highly stable voltage hysteresis over a long cycling life >1200 h is achieved, and a low and stable voltage hysteresis can be realized even at an ultrahigh current density of 64 mA cm−2. Furthermore, the NHCNSs-based anodes, when paired with a LiFePO4 (LFP) cathode in full cells, give rise to highly improved rate capability (104 mAh g−1 at 10 C) and cycling stability (91.4% capacity retention for 200 cycles), enabling a promising candidate for the next-generation high energy/power density batteries