Joint Rigid Registration of Multiple Generalized Point Sets With Anisotropic Positional Uncertainties in Image-Guided Surgery

In medical image analysis (MIA) and computer-assisted surgery (CAS), aligning two multiple point sets (PSs) together is an essential but also a challenging problem. For example, rigidly aligning multiple point sets into one common coordinate frame is a prerequisite for statistical shape modelling (SSM). Accurately aligning the pre-operative space with the intra-operative space in CAS is very crucial to successful interventions. In this article, we formally formulate the multiple generalized point set registration problem (MGPSR) in a probabilistic manner, where both the positional and the normal vectors are used. The six-dimensional vectors consisting of both positional and normal vectors are called as generalized points. In the formulated model, all the generalized PSs to be registered are considered to be the realizations of underlying unknown hybrid mixture models (HMMs). By assuming the independence of the positional and orientational vectors (i.e., the normal vectors), the probability density function (PDF) of an observed generalized point is computed as the product of Gaussian and Fisher distributions. Furthermore, to consider the anisotropic noise in surgical navigation, the positional error is assumed to obey a multi-variate Gaussian distribution. Finally, registering PSs is formulated as a maximum likelihood (ML) problem, and solved under the expectation maximization (EM) technique. By using more enriched information (i.e., the normal vectors), our algorithm is more robust to outliers. By treating all PSs equally, our algorithm does not bias towards any PS. To validate the proposed approach, extensive experiments have been conducted on surface points extracted from CT images of (i) a human femur bone model; (ii) a human pelvis bone model. Results demonstrate our algorithm's high accuracy, robustness to noise and outliers

Amphetamine Alters Acid-Sensing Ion Channel Expression in the Rat Striatum

Neuroscience - Vision and Functional Brain Imaging Poster SessionIntroduction: The acid-sensing ion channel (ASIC) is specifically activated by a drop in the extracellular pH level. These channels are widely expressed in mammalian brains and actively modulate synaptic transmission and a variety of neuronal activities. In the striatum, two ASIC subtypes (ASIC1 and ASIC2) are densely expressed. Given the fact that the striatum is a central site for processing biological actions of drugs of abuse, expression of abundant ASICs in this structure implies a potential involvement of the channel in drug effects. In this study, we examined the expression of ASIC1 and ASIC2 in the rat striatum in response to chronic exposure to the psychostimulant amphetamine in vivo. Methods: Following IACUC approval, adult male Wistar rats (2 groups, n = 6 per group) received intraperitoneal injections of saline or amphetamine (once daily for 7 days, 1.25 mg/kg for day 1 and day 7, 4 mg/kg for days 2-6). At 14 days after the termination of drug injection, rats were sacrificed after anesthesia. Brains were removed and sliced into coronal sections (400 [mu]m). The dorsal (caudate putamen, CPu) and ventral (nucleus accumbens, NAc) striatum were dissected in artificial cerebrospinal fluid. A membrane-impermeable cross-linking reagent bis(sulfosuccinimidyl)suberate (BS3) was added. BS3 only cross-links ASICs on the surface of live cells to form high-molecular weight aggregates which can be readily separated from normal intracellular monomer ASIC proteins. Densities of immunoblots were measured using optical scanning and the data were analyzed (t-test (p < 0.05)). Results: BS3-treated striatal tissue showed a high-molecular weight band of ASIC1 and ASIC2 (surface channels) and a monomeric molecular weight band of ASIC1 and ASIC2 (intracellular channels). Quantification analysis revealed that 70-80% of ASIC1 and ASIC2 are expressed in the surface membrane of normal striatal neurons. Chronic amphetamine administration induced parallel increases in ASIC1 protein levels in both surface and intracellular pools in the CPu at a 14-day withdrawal period. Similar results were also observed in the NAc. In contrast to ASIC1, ASIC2 and [alpha]-actinin in their protein levels remained unchanged in the CPu and NAc of amphetamine-treated rats. Conclusion: These data identified the central ASIC as a sensitive target to repeated stimulant exposure. Discussion: Various synaptic proteins have been screened for their responses to repeated drug exposure. Plastic changes in the expression and function of all responsive proteins are thought to operate in concert to control drug effects. In this study, a new responsive gene is identified. Following repeated amphetamine administration, ASIC expression was regulated in striatal regions. This identifies the channel as an important element of molecular adaptations to drug exposure. Indeed, ASICs have been implicated in various mental disorders1. This study represents an initial effort toward elucidating the precise role of ASICs in processing the addictive action of drugs of abuse

Regulation of Phosphorylation of Dopamine D3 Receptors in Mouse Striatal Neurons in vivo

Neuroscience - Vision and Functional Brain Imaging Poster SessionIntroduction: Dopamine D3 receptors (D3Rs) are G-protein-coupled receptors. These D3Rs inhibit adenylyl cyclase and the downstream formation of cAMP. Due to their preferential expression in the mesolimbic areas, especially in the nucleus accumbens (NAc), they are known to play a major role in the mesolimbic function. Recently, we found that D3Rs are phosphorylated at serine 229 (Ser229) by Ca2+/calmodulin-dependent protein kinase II (CaMKII). This phosphorylation is subject to the modulation, and the phosphorylation level controls receptor function. In this study, an effort was made to develop a phospho- and site-specific antibody. Using this antibody, we hypothesized that the modulation of D3R phosphorylation at Ser229 by dopamine D1 receptors would occur in the mouse NAc in vivo. Methods: To detect phosphorylation of D3Rs at Ser229 in striatal neurons in vivo, we developed a phospho- and site-specific antibody. A short peptide containing phospho-Ser229 (KRILTRQNpSQCISI) was synthesized and used as an immunogen for producing a polyclonal antibody from rabbits. Upon demonstration of the selectivity of this antibody, we used it in Western blot to monitor changes in Ser229 phosphorylation in striatal neurons in response to dopamine D1 receptor stimulation by a D1 selective agonist SKF81297. Following IACUC approval, adult male mice (CL57/BL6) were randomly divided into 2 groups (n = 3 per group). The animals received an intraperitoneal injection of saline or SKF81297 (1 mg/kg). Animals were sacrificed by cervical dislocation 15 min after drug injection. The NAc was removed and homogenized. Homogenates were centrifuged (1000 g, 10 min), and the supernatant was used for Western blot. Densities of immunoblots were measured using optical scanning and the data were analyzed using Student's t-test (p < 0.05). Results: A series of control experiments validated the selectivity of the antibody against phosphorylated D3Rs at Ser229 (pD3R-Ser229). Using this antibody, we found that the level of pD3R-Ser229 in the NAc was significantly increased in mice treated with a systemic injection of the D1 receptor agonist SKF81297 (1 mg/kg, 15 min) compared to mice treated with saline. Conclusion: Using a phospho- and site-specific antibody against phospho-D3Rs at Ser229, we found that stimulation of dopamine D1 receptors increases phosphorylation of D3Rs in the mouse NAc in vivo. Discussion: Developing a phospho- and site-specific antibody is necessary for detecting changes in D3R phosphorylation in vivo. Using this newly acquired antibody, we found that Ser229 phosphorylation of D3Rs is subject to the modulation by dopamine D1 receptors. This seems to indicate a previously-unrecognized D1-dependent negative feedback control of D3R function given that Ser229 phosphorylation inhibits D3Rs1. In a subpopulation of striatal neurons that co-express D3Rs and D1 receptors, dopamine is able to concurrently enhance the D1-mediated phosphorylation of D3Rs to induce a heterologous desensitization of D3Rs after their activation. This regulation is deemed important for maintaining normal homeostasis of D3R function and could be altered to contribute to various neurological disorders

A Survey on Energy-Efficient Strategies in Static Wireless Sensor Networks

A comprehensive analysis on the energy-efficient strategy in static Wireless Sensor Networks (WSNs) that are not equipped with any energy harvesting modules is conducted in this article. First, a novel generic mathematical definition of Energy Efficiency (EE) is proposed, which takes the acquisition rate of valid data, the total energy consumption, and the network lifetime of WSNs into consideration simultaneously. To the best of our knowledge, this is the first time that the EE of WSNs is mathematically defined. The energy consumption characteristics of each individual sensor node and the whole network are expounded at length. Accordingly, the concepts concerning EE, namely the Energy-Efficient Means, the Energy-Efficient Tier, and the Energy-Efficient Perspective, are proposed. Subsequently, the relevant energy-efficient strategies proposed from 2002 to 2019 are tracked and reviewed. Specifically, they respectively are classified into five categories: the Energy-Efficient Media Access Control protocol, the Mobile Node Assistance Scheme, the Energy-Efficient Clustering Scheme, the Energy-Efficient Routing Scheme, and the Compressive Sensing--based Scheme. A detailed elaboration on both of the basic principle and the evolution of them is made. Finally, further analysis on the categories is made and the related conclusion is drawn. To be specific, the interdependence among them, the relationships between each of them, and the Energy-Efficient Means, the Energy-Efficient Tier, and the Energy-Efficient Perspective are analyzed in detail. In addition, the specific applicable scenarios for each of them and the relevant statistical analysis are detailed. The proportion and the number of citations for each category are illustrated by the statistical chart. In addition, the existing opportunities and challenges facing WSNs in the context of the new computing paradigm and the feasible direction concerning EE in the future are pointed out

Similarities and differences between biliary sludge and microlithiasis: Their clinical and pathophysiological significances

The terms biliary sludge and cholesterol microlithiasis (hereafter referred to as microlithiasis) were originated from different diagnostic techniques and may represent different stages of cholesterol gallstone disease. Although the pathogenesis of biliary sludge and microlithiasis may be similar, microlithiasis could be preceded by biliary sludge, followed by persistent precipitation and aggregation of solid cholesterol crystals, and eventually, gallstone formation. Many clinical conditions are clearly associated with the formation of biliary sludge and microlithiasis, including total parenteral nutrition, rapid weight loss, pregnancy, organ transplantation, administration of certain medications, and a variety of acute and chronic illnesses. Numerous studies have demonstrated complete resolution of biliary sludge in approximately 40% of patients, a cyclic pattern of disappearing and reappearing in about 40%, and progression to gallstones in nearly 20%. Although only a minority of patients with ultrasonographic demonstration of biliary sludge develop gallstones, it is still a matter of controversy whether microlithiasis could eventually evolve to cholesterol gallstones. Biliary sludge and microlithiasis are asymptomatic in the vast majority of patients; however, they can cause biliary colic, acute cholecystitis, and acute pancreatitis. Biliary sludge and microlithiasis are most often diagnosed ultrasonographically and bile microscopy is considered the gold standard for their diagnosis. Specific measures to prevent the development of biliary sludge are not practical or cost-effective in the general population. Laparoscopic cholecystectomy offers the most definitive therapy on biliary sludge. Endoscopic sphincterotomy or surgical intervention is effective for microlithiasis-induced pancreatitis. Ursodeoxycholic acid can effectively prevent the recurrence of solid cholesterol crystals and significantly reduce the risk of recurrent pancreatitis. Keywords: Biliary sludge, Cholesterol microlithiasis, Acute cholecystitis, Acute pancreatitis, Biliary colic, Cholesterol monohydrate crystals, Lithogenic bil

X-ray detection of the most extreme star-forming galaxies at the cosmic noon via strong lensing

Hyperluminous infrared galaxies (HyLIRGs) are the most extreme star-forming systems observed in the early Universe, and their properties still elude comprehensive understanding. We have undertaken a large XMM–Newton observing programme to probe the total accreting black hole population in three HyLIRGs at z = 2.12, 3.25, and 3.55, gravitationally lensed by foreground galaxies. Selected from the Planck All-Sky Survey to Analyse Gravitationally lensed Extreme Starbursts (PASSAGES), these HyLIRGs have apparent infrared luminosities \u3e1014 L⊙. Our observations revealed X-ray emission in each of them. PJ1336+49 appears to be dominated by high-mass X-ray binaries (HMXBs). Remarkably, the luminosity of this non-AGN X-ray emission exceeds by a factor of about 3 the value obtained by calibration with local galaxies with much lower star formation rates. This enhanced X-ray emission most likely highlights the efficacy of dynamical HMXB production within compact clusters, which is an important mode of star formation in HyLIRGs. The remaining two (PJ0116−24 and PJ1053+60) morphologically and spectrally exhibit a compact X-ray component in addition to the extended non-AGN X-ray emission, indicating the presence of Active Galactic Nuclei (AGNs). The AGN appears to be centrally located in the reconstructed source plane images of PJ0116−24, which manifests its star-forming activity predominantly within an extended galactic disc. In contrast, the AGN in the field of PJ1053+60 is projected 60 kpc away from the extreme star-forming galaxy and could be ejected from it. These results underline the synergistic potential of deep X-ray observations with strong lensing for the study of high-energy astrophysical phenomena in HyLIRGs

Deep Reinforcement Learning-Based Offloading Scheduling for Vehicular Edge Computing

This is the author accepted manuscript. The final version is available from IEEE via the DOI in this recordVehicular edge computing (VEC) is a new computing paradigm that has great potential to enhance the capability of vehicle terminals (VT) to support resource-hungry in-vehicle applications with low latency and high energy efficiency. In this paper, we investigate an important computation offloading scheduling problem in a typical VEC scenario, where a VT traveling along an expressway intends to schedule its tasks waiting in the queue to minimize the long-term cost in terms of a trade-off between task latency and energy consumption. Due to diverse task characteristics, dynamic wireless environment, and frequent handover events caused by vehicle movements, an optimal solution should take into account both where to schedule (i.e., local computation or offloading) and when to schedule (i.e., the order and time for execution) each task. To solve such a complicated stochastic optimization problem, we model it by a carefully designed Markov decision process (MDP) and resort to deep reinforcement learning (DRL) to deal with the enormous state space. Our DRL implementation is designed based on the state-of-the-art proximal policy optimization (PPO) algorithm. A parameter-shared network architecture combined with a convolutional neural network (CNN) is utilized to approximate both policy and value function, which can effectively extract representative features. A series of adjustments to the state and reward representations are taken to further improve the training efficiency. Extensive simulation experiments and comprehensive comparisons with six known baseline algorithms and their heuristic combinations clearly demonstrate the advantages of the proposed DRL-based offloading scheduling method.European Commissio