Description: In dynamic MRI, spatial and temporal parallel imaging can be exploited to reduce scan time. Real-time reconstruction enables immediate visualization during the scan. Commonly used view-sharing techniques suffer from limited temporal resolution, and many of the more advanced reconstruction methods are either retrospective, time-consuming, or both. A Kalman filter model capable of real-time reconstruction can be used to increase the spatial and temporal resolution in dynamic MRI reconstruction. The original study describing the use of the Kalman filter in dynamic MRI was limited to non-Cartesian trajectories because of a limitation intrinsic to the dynamic model used in that study. Here the limitation is overcome, and the model is applied to the more commonly used Cartesian trajectory with fast reconstruction. Furthermore, a combination of the Kalman filter model with Cartesian parallel imaging is presented to further increase the spatial and temporal resolution and signal-to-noise ratio. Simulations and experiments were conducted to demonstrate that the Kalman filter model can increase the temporal resolution of the image series compared with view-sharing techniques and decrease the spatial aliasing compared with TGRAPPA. The method requires relatively little computation, and thus is suitable for real-time reconstruction. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.

Description: Accurately measuring the bulk minority carrier lifetime is one of the greatest challenges in evaluating photoactive materials used in photovoltaic cells. One-photon time-resolved photoluminescence decay measurements are commonly used to measure lifetimes of direct bandgap materials. However, because the incident photons have energies higher than the bandgap of the semiconductor, most carriers are generated close to the surface, where surface defects cause inaccurate lifetime measurements. Here we show that two-photon absorption permits sub-surface optical excitation, which allows us to decouple surface and bulk recombination processes even in unpassivated samples. Thus with two-photon microscopy we probe the bulk minority carrier lifetime of photovoltaic semiconductors. We demonstrate how the traditional one-photon technique can underestimate the bulk lifetime in a CdTe crystal by 10× and show that two-photon excitation more accurately measures the bulk lifetime. Finally, we generate multi-dimensional spatial maps of optoelectronic properties in the bulk of these materials using two-photon excitation. Scientific Reports 3 doi: 10.1038/srep02098

Description: Author(s): D. Heinert, K. Craig, H. Grote, S. Hild, H. Lück, R. Nawrodt, D. A. Simakov, D. V. Vasilyev, S. P. Vyatchanin, and H. Wittel Current gravitational-wave detectors rely on the use of Michelson interferometers. One crucial limitation of their sensitivity is the thermal noise of their optical components. Thus, for example, fluctuational deformations of the mirror surface are probed by a laser beam being reflected from the mir... [Phys. Rev. D 90, 042001] Published Thu Aug 07, 2014

Description: Non-invasive imaging techniques are highly desirable as an alternative to conventional biopsy for the characterization of the remodeling of tissues associated with disease progression, including end-stage heart failure. Cardiac diffusion tensor imaging (DTI) has become an established method for the characterization of myocardial microstructure. However, the relationships between diffuse myocardial fibrosis, which is a key biomarker for staging and treatment planning of the failing heart, and measured DTI parameters have yet to be investigated systematically. In this study, DTI was performed on left ventricular specimens collected from patients with chronic end-stage heart failure as a result of idiopathic dilated cardiomyopathy ( n  = 14) and from normal donors ( n  = 5). Scalar DTI parameters, including fractional anisotropy (FA) and mean (MD), primary ( D 1 ), secondary ( D 2 ) and tertiary ( D 3 ) diffusivities, were correlated with collagen content measured by digital microscopy. Compared with hearts from normal subjects, the FA in failing hearts decreased by 22%, whereas the MD, D 2 and D 3 increased by 12%, 14% and 24%, respectively ( P  〈 0.01). No significant change was detected for D 1 between the two groups. Furthermore, significant correlation was observed between the DTI scalar indices and quantitative histological measurements of collagen (i.e. fibrosis). Pearson's correlation coefficients ( r ) between collagen content and FA, MD, D 2 and D 3 were –0.51, 0.59, 0.56 and 0.62 ( P  〈 0.05), respectively. The correlation between D 1 and collagen content was not significant ( r  = 0.46, P  = 0.05). Computational modeling analysis indicated that the behaviors of the DTI parameters as a function of the degree of fibrosis were well explained by compartmental exchange between myocardial and collagenous tissues. Combined, these findings suggest that scalar DTI parameters can be used as metrics for the non-invasive assessment of diffuse fibrosis in failing hearts. Copyright © 2014 John Wiley & Sons, Ltd. Myocardial diffuse fibrosis has been linked to arrhythmias and sudden cardiac death. Although diffusion tensor imaging (DTI) is increasingly being used to characterize cardiac diseases, quantitative correlation between DTI scalar metrics and diffuse fibrosis remains lacking. In this study, DTI parameters obtained on heart specimens from patients with idiopathic dilated cardiomyopathy and from normal donors were correlated with histological collagen content measurements. The results indicated that diffuse fibrosis is significantly correlated with water diffusivity and inversely correlated with diffusion anisotropy. Computational analysis showed that the behaviors of the DTI parameters are well explained by compartmental exchange between myocardial and collagenous tissues.

Description: Purpose To develop and assess a three-dimensional refocused turbo spin-echo (rTSE) sequence for generating peripheral angiograms. This sequence combines the rapid T 2 -weighting of TSE and the better flow performance of the fully-refocused gradients of balanced steady state free precession (bSSFP), along with bSSFP-style phase alternation of refocusing radiofrequency (RF) pulses. Materials and Methods The signal behavior generated by such a sequence was explored through Bloch equation simulations. The rTSE and TSE sequences were both used to generate peripheral angiograms in nine normal volunteers. The signal to noise ratio, contrast resolution, and vessel sharpness of the resulting images were used as bases for comparison. Additionally, the rTSE sequence was applied in four patients with peripheral artery disease to preliminarily assess its efficacy in a clinical setting through quality scoring by two experienced radiologists. Results The rTSE's RF phase alternation approach out-performs a simple balanced-gradient CPMG (Carr-Purcell-Meiboom-Gill) -style TSE sequence in the presence of B 0 and B 1 inhomogeneities. In volunteers, the rTSE sequence yielded better arterial–venous contrast (0.378 ± 0.145 versus 0.155 ± 0.202; P 〈 0.01) and increased vessel sharpness (0.340 ± 0.034 versus 0.263 ± 0.034; P 〈 0.005) over TSE images. Stenoses visible in conventional angiographic images in patients were successfully imaged with the rTSE sequence; however, image quality scores in patients were lower than in volunteers (1.2 ± 0.38 versus 3.0 ± 1.0; P 〈 0.05). Conclusion The rTSE sequence generates nonsubtractive, flow-independent, peripheral MR angiograms with better arterial–venous contrast and vessel sharpness in normal volunteers than a conventional TSE sequence. J. Magn. Reson. Imaging 2013 . © 2013 Wiley Periodicals, Inc .

Description: BACKGROUND Brentuximab vedotin (BV) is an anti-CD30 monoclonal antibody-drug conjugate that was approved in 2011 for the treatment of patients with anaplastic large cell and Hodgkin lymphomas. The product label indicates that 3 patients who were treated with BV developed progressive multifocal leukoencephalopathy (PML), a frequently fatal JC virus-induced central nervous system infection. Prior immunosuppressive therapy and compromised immune systems were postulated risk factors. In the current study, the authors reported 5 patients who developed BV-associated PML, including 2 immunocompetent patients. METHODS Case information was obtained from clinicians (4 patients) or a US Food and Drug Administration database (1 patient). RESULTS All 5 patients had lymphoid malignancies. Two patients with cutaneous T-cell lymphomas had not previously received chemotherapy. PML developed after a median of 3 BV doses (range, 2 doses-6 doses) and within a median of 7 weeks after BV initiation (range, 3 weeks-34 weeks). Presenting findings included aphasia, dysarthria, confusion, hemiparesis, and gait dysfunction; JC virus in the cerebrospinal fluid (2 patients) or central nervous system biopsy (3 patients); and brain magnetic resonance imaging scans with white matter abnormalities (5 patients). Four patients died at a median of 8 weeks (range, 6 weeks-16 weeks) after PML diagnosis. The sole survivor developed immune reconstitution inflammatory syndrome. CONCLUSIONS PML can develop after a few BV doses and within weeks of BV initiation. Clinicians should be aware of this syndrome, particularly when neurologic changes develop after the initiation of BV treatment. The decision to administer BV to patients with indolent cutaneous lymphomas should be based on consideration of risk-benefit profiles and of alternative options. Cancer 2014 . © 2014 American Cancer Society .

Description: Purpose To develop a spin echo train sequence with spiral readout gradients with improved artery–vein contrast for noncontrast angiography. Theory Venous T 2 becomes shorter as the echo spacing is increased in echo train sequences, improving contrast. Spiral acquisitions, due to their data collection efficiency, facilitate long echo spacings without increasing scan times. Methods Bloch equation simulations were performed to determine optimal sequence parameters, and the sequence was applied in five volunteers. In two volunteers, the sequence was performed with a range of echo times and echo spacings to compare with the theoretical contrast behavior. A Cartesian version of the sequence was used to compare contrast appearance with the spiral sequence. Additionally, spiral parallel imaging was optionally used to improve image resolution. Results In vivo, artery–vein contrast properties followed the general shape predicted by simulations, and good results were obtained in all stations. Compared with a Cartesian implementation, the spiral sequence had superior artery–vein contrast, better spatial resolution (1.2 mm 2 versus 1.5 mm 2 ), and was acquired in less time (1.4 min versus 7.5 min). Conclusion The spiral spin echo train sequence can be used for flow-independent angiography to generate three-dimensional angiograms of the periphery quickly and without the use of contrast agents. Magn Reson Med, 2014. © 2014 Wiley Periodicals, Inc.

Description: Nature Genetics 45, 1134 (2013). doi:10.1038/ng.2760 Authors: Travis I Zack, Steven E Schumacher, Scott L Carter, Andrew D Cherniack, Gordon Saksena, Barbara Tabak, Michael S Lawrence, Cheng-Zhong Zhang, Jeremiah Wala, Craig H Mermel, Carrie Sougnez, Stacey B Gabriel, Bryan Hernandez, Hui Shen, Peter W Laird, Gad Getz, Matthew Meyerson & Rameen Beroukhim

Description: Receiver functions sampling the Sierra Nevada batholith and adjacent regions exhibit significant variations in the structure of the crust and upper mantle. Crustal Vp/Vs values are lower in the core of the batholith and higher in the northern Sierra Nevada, portions of the Basin and Range, and near young volcanic fields in the eastern Sierra Nevada and Owens Valley. P- to S-wave conversions from the Moho vary from high amplitude and shallow (〉25% of the direct P-arrival amplitude, 25-35 km depth) along the eastern Sierra Nevada to low amplitude and deep (

Description: The widespread presumption that the Farallon plate subducted along the base of North American lithosphere under most of the western United States and [~]1000 km inboard from the trench has dominated tectonic studies of this region, but a number of variations of this concept exist due to differences in interpretation of some aspects of this orogeny. We contend that five main characteristics are central to the Laramide orogeny and must be explained by any successful hypothesis: thick-skinned tectonism, shutdown and/or landward migration of arc magmatism, localized deep foreland subsidence, deformation landward of the relatively undeformed Colorado Plateau, and spatially limited syntectonic magmatism. We detail how the first two elements can be well explained by a broad flat slab, the others less so. We introduce an alternative hypothesis composed of five particular processes: (1) a more limited segment of shallowly subducting slab is created by viscous coupling between the slab and the Archean continental keel of the Wyoming craton, leaving some asthenosphere above most of the slab; (2) dynamic pressures from this coupling localize subsidence at the edge of the Archean Wyoming craton; (3) foreland shortening occurs after the subsidence of the region decreases gravitational potential energy, increasing deviatoric stresses in lithosphere beneath the basin with no change to boundary stresses near the subduction zone or changes to basal shear stress; (4) shear between the slab and overriding continent induces a secondary convective system aligned parallel to relative plate motion, producing the Colorado Mineral Belt above upwelling aligned along the convection cell; (5) the development of this convective system interrupts the flow of fresh asthenosphere into the arc region farther west, cutting off magmatism even in segments of the arc not over the shallowly dipping slab.