k-Space Deep Learning for Parallel MRI: Application to Time-Resolved MR Angiography

Time-resolved angiography with interleaved stochastic trajectories (TWIST) has been widely used for dynamic contrast enhanced MRI (DCE-MRI). To achieve highly accelerated acquisitions, TWIST combines the periphery of the k-space data from several adjacent frames to reconstruct one temporal frame. However, this view-sharing scheme limits the true temporal resolution of TWIST. Moreover, the k-space sampling patterns have been specially designed for a specific generalized autocalibrating partial parallel acquisition (GRAPPA) factor so that it is not possible to reduce the number of view-sharing once the k-data is acquired. To address these issues, this paper proposes a novel k-space deep learning approach for parallel MRI. In particular, we have designed our neural network so that accurate k-space interpolations are performed simultaneously for multiple coils by exploiting the redundancies along the coils and images. Reconstruction results using in vivo TWIST data set confirm that the proposed method can immediately generate high-quality reconstruction results with various choices of view- sharing, allowing us to exploit the trade-off between spatial and temporal resolution in time-resolved MR angiography

Optimization of magnetic flux density for fast MREIT conductivity imaging using multi-echo interleaved partial fourier acquisitions

BACKGROUND: Magnetic resonance electrical impedance tomography (MREIT) has been introduced as a non-invasive method for visualizing the internal conductivity and/or current density of an electrically conductive object by externally injected currents. The injected current through a pair of surface electrodes induces a magnetic flux density distribution inside the imaging object, which results in additional magnetic flux density. To measure the magnetic flux density signal in MREIT, the phase difference approach in an interleaved encoding scheme cancels out the systematic artifacts accumulated in phase signals and also reduces the random noise effect by doubling the measured magnetic flux density signal. For practical applications of in vivo MREIT, it is essential to reduce the scan duration maintaining spatial-resolution and sufficient contrast. In this paper, we optimize the magnetic flux density by using a fast gradient multi-echo MR pulse sequence. To recover the one component of magnetic flux density B(z), we use a coupled partial Fourier acquisitions in the interleaved sense. METHODS: To prove the proposed algorithm, we performed numerical simulations using a two-dimensional finite-element model. For a real experiment, we designed a phantom filled with a calibrated saline solution and located a rubber balloon inside the phantom. The rubber balloon was inflated by injecting the same saline solution during the MREIT imaging. We used the multi-echo fast low angle shot (FLASH) MR pulse sequence for MRI scan, which allows the reduction of measuring time without a substantial loss in image quality. RESULTS: Under the assumption of a priori phase artifact map from a reference scan, we rigorously investigated the convergence ratio of the proposed method, which was closely related with the number of measured phase encode set and the frequency range of the background field inhomogeneity. In the phantom experiment with a partial Fourier acquisition, the total scan time was less than 6 seconds to measure the magnetic flux density B(z) data with 128×128 spacial matrix size, where it required 10.24 seconds to fill the complete k-space region. CONCLUSION: Numerical simulation and experimental results demonstrated that the proposed method reduces the scanning time and provides the recovered B(z) data comparable to what we obtained by measuring complete k-space data

Transvaginal Endoscopic Appendectomy

Since Kalloo and colleagues first reported the feasibility and safety of a peroral transgastric approach in the porcine model in 2004, various groups have reported more complex natural orifice transluminal endoscopic surgery (NOTES) procedures, such as the cholecystectomy, splenectomy and liver biopsy, in the porcine model. Natural orifice access to the abdominal cavity, such as transgastric, transvesical, transcolonic, and transvaginal, has been described. Although a novel, minimally invasive approach to the abdominal cavity is a peroral endoscopic transgastric approach, there are still some challenging issues, such as the risk of infection and leakage, and the method of gastric closure. Hybrid-NOTES is an ideal first step in humans. Human hybrid transvaginal access has been used for years by many surgeons for diagnostic and therapeutic purposes. Here, we report a transvaginal flexible endoscopic appendectomy, with a 5-mm umbilical port using ultrasonic scissors in a 74-year-old woman with acute appendicitis

A Novel BEST1 Mutation in Autosomal Recessive Bestrophinopathy

Citation: Lee CS, Jun I, Choi S, et al. A novel BEST1 mutation in autosomal recessive bestrophinopathy. Invest Ophthalmol Vis Sci. 2015;56:8141-8150. DOI:10.1167/iovs.15-18168 PURPOSE. To describe the clinical characteristics associated with a newly identified mutant of autosomal recessive bestrophinopathy (ARB) and confirm the associated physiological functional defects. METHODS. Two patients with ARB from one family underwent a full ophthalmic examination, including dilated fundus examination, fundus photography, fluorescein angiography, fundus autofluorescence imaging, spectral-domain optical coherence tomography (OCT), electroretinography (ERG), and electrooculography (EOG). Subsequently, genetic analysis for bestrophin-1 (BEST1) mutations was conducted through direct Sanger sequencing. The effect of ARB-associated mutations of BEST1 on the cellular localization was determined by in vitro experiments. Whole-cell patch clamping was conducted to measure the chloride conductance of wild-type BEST1 and the identified BEST1 mutants in transfected HEK293T cells. RESULTS. Two related patients (66-year-old brother and 52-year-old sister) presented with reduced visual acuity and bilateral symmetrical subretinal deposits of hyperautofluorescent materials in the posterior pole. Spectral-domain OCT showed macular thinning with submacular fluid. The female patient had a concomitant macular edema associated with branched retinal vein occlusion in the left eye, which responded well to intravitreal bevacizumab injections. Genetic analysis demonstrated that both patients were compound heterozygous for one novel (Leu40Pro) and one previously identified (Ala195Val) BEST1 variant. HEK293T cells transfected with the identified BEST1 mutant showed significantly small currents compared to those transfected with the wild-type gene, whereas cells cotransfected with mutant and wild-type BEST1 showed good chloride conductance. Cellular localization of BEST1 was well conserved to the plasma membrane in the mutants. CONCLUSIONS. We have identified and described the phenotype and in vitro functional aspects of a new BEST1 mutation causing ARB. Clinically suspected ARB cases warrant genetic confirmation to confirm the diagnosis

Use of Aripiprazole in Clozapine Induced Enuresis: Report of Two Cases

This report describes the efficacy of combined use of aripiprazole in the treatment of a patient with clozapine induced enuresis. Aripiprazole acts as a potential dopamine partial agonist and the dopamine blockade in the basal ganglia might be one of the causes of urinary incontinence and enuresis. We speculate that aripiprazole functioned as a D2 agonist in hypodopaminergic state of basal ganglia caused by clozapine and maintained dopamine level that would improve enuresis ultimately