Clinical and imaging features of pituitary apoplexy and role of imaging in differentiation of clinical mimics

To discuss the clinical syndrome, review common imaging findings of pituitary apoplexy (PA) and role of imaging in therapy and follow-up. Also, to review other acute clinical scenarios with similar clinical and/or imaging findings as PA. PA is a severe and potentially life-threatening medical emergency, characterized by constellation of symptoms/signs that occur as a result of acute hemorrhage and/or infarction in pituitary gland. Patients present with acute and sudden onset of symptoms/signs, most commonly with severe headache, vision deficits/ophthalmoplegia, altered mental status, and possible pan hypopituitarism. Pre-existing macro adenoma (65-90%), especially non-functioning and prolactinomas, are most susceptible to apoplexy, which undergoes hemorrhage or infarct, but PA can occur with normal pituitary or microadenoma. Because of the probable grave prognosis of PA, imaging characteristics of PA and other acute clinical scenarios with similar clinical and/or imaging findings should be familiar to radiologists. PA is potentially a life-threatening clinical syndrome, however, imaging and clinical findings can lead the radiologist towards appropriate diagnosis, and rule out other clinical mimics. When hemorrhage is secondary to an underlying lesion, regrowth of the pituitary tumor years after a PA episode is possible and patients require long-term clinical and imaging surveillance.

Design considerations for patient-specific surgical templates for total hip arthroplasty with respect to acetabular cartilage

Patient-specific instruments (PSIs) are clinically used to support the surgeon during a planned intervention. The planning is typically done based on volumetric image data from medical imaging systems, e.g. computed tomography (CT). The PSI uses the known surface structure of a bone for orientation during the intervention. Some surfaces of human bone are covered with a layer of cartilage which is hardly visible in clinically applied CT-imaging. This experimental study investigates ten different PSI designs and their effect to the overall accuracy when neglecting the cartilage in the design process. Therefore, a model of an acetabulum is used to simulate the use case of PSI in total hip arthroplasty. The concept of the different designs is to create structural elasticities in the PSI to avoid shifting of the whole instrument and rather have a small part of it deformed by cartilage. A needle array structure, for instance, should also be able to oust or penetrate remaining soft tissue in the acetabulum.

Electrical spin injection into high mobility 2D systems

We report on spin injection into a high mobility 2D electron system confined at an (Al,Ga)As/GaAs interface, using (Ga,Mn)As Esaki diode contacts as spin aligners. We measured a clear nonlocal spin valve signal, which varies nonmonotonically with the applied bias voltage. The magnitude of the signal cannot be described by the standard spin drift-diffusion model, because at maximum this would require the spin polarization of the injected current to be much larger than 100%, which is unphysical. A strong correlation of the spin signal with contact width and electron mean free path suggests that ballistic transport in the 2D region below ferromagnetic contacts should be taken into account to fully describe the results.

Visualization of the diaphragm muscle with ultrasound improves diagnostic accuracy of phrenic nerve conduction studies

INTRODUCTION

Evaluation of phrenic neuropathy (PN) with phrenic nerve conduction studies (PNCS) is associated with false negatives. Visualization of diaphragmatic muscle twitch with diaphragm ultrasound (DUS) when performing PNCS may help to solve this problem.

METHODS

We performed bilateral, simultaneous DUS-PNCS in 10 healthy adults and 12 patients with PN. The amplitude of the diaphragm compound muscle action potential (CMAP) (on PNCS) and twitch (on DUS) was calculated.

RESULTS

Control subjects had <38% side-to-side asymmetry in twitch amplitude (on DUS) and 53% asymmetry in phrenic CMAP (on PCNS). In the 12 patients with PN, 12 phrenic neuropathies were detected. Three of these patients had either significant side-to-side asymmetry or absolute reduction in diaphragm movement that was not detected with PNCS. There were no cases in which the PNCS showed an abnormality but the DUS did not.

CONCLUSIONS

The addition of DUS to PNCS enhances diagnostic accuracy in PN.

Identifying the electronic character and role of the Mn states in the valence band of (Ga,Mn)As

We report high-resolution hard x-ray photoemission spectroscopy results on (Ga,Mn)As films as a function of Mn doping. Supported by theoretical calculations we identify, for both low (1%) and high (13%) Mn doping values, the electronic character of the states near the top of the valence band. Magnetization and temperature-dependent core-level photoemission spectra reveal how the delocalized character of the Mn states enables the bulk ferromagnetic properties of (Ga,Mn)As.

Growth of ultrathin epitaxial Fe/MgO spin injector on (0, 0, 1) (Ga, Mn)As

We have grown an ultrathin epitaxial Fe/MgO bilayer on (Ga, Mn)As by e-beam evaporation in UHV. The system structure has been investigated by high resolution transmission electron microscopy (TEM) experiments which show that the Fe and MgO films, covering completely the (Ga, Mn)As, grow with the epitaxial relationship Fe[100](001) [parallel] MgO[110](001) [parallel] (Ga,Mn)As[110](001). The magnetic reversal process, studied by the magneto-optical Kerr effect (MOKE) at room temperature, demonstrates that the iron is ferromagnetic and possesses a cubic anisotropy, confirming the epitaxy relationship found with TEM. Resistivity measurements across the barrier display a non-Ohmic behavior characterized by cubic conductance as a function of the applied voltage suggesting tunneling-dominated transport across the barrier.

Identification of different electron screening behavior between the bulk and surface of (Ga,Mn)As

We report x-ray photoemission spectroscopy results on (Ga,Mn)As films as a function of both temperature and Mn doping. Analysis of Mn 2p core level spectra reveals the presence of a distinct electronic screening channel in the bulk, hitherto undetected in more surface sensitive analysis. Comparison with model calculations identifies the character of the Mn 3d electronic states and clarifies the role, and the difference between surface and bulk, of hybridization in mediating the ferromagnetic coupling in (Ga,Mn)As.

Proximity induced enhancement of the Curie temperature in hybrid spin injection devices

We investigate the increase of the Curie temperature T(C) in a lateral spin injection geometry where the ferromagnetic (Ga,Mn)As injector and detector contacts are capped by a thin iron film. Because of interlayer coupling between Fe and (Ga,Mn)As T(C) gets enhanced by nearly 100% for the thinnest (Ga,Mn)As films. The use of the proximity effect might pave the way for practical implementation of spintronic devices.

All-electrical measurement of the density of states in (Ga,Mn)As

We report on electrical measurements of the effective density of states in the ferromagnetic semiconductor material (Ga,Mn)As. By analyzing the conductivity correction to an enhanced electron-electron interaction the electrical diffusion constant was extracted for (Ga,Mn)As samples of different dimensionality. Using the Einstein relation allows us to deduce the effective density of states of (Ga,Mn)As at the Fermi energy.

Efficient reconstruction of multiphase morphologies from correlation functions

A highly efficient algorithm for the reconstruction of microstructures of heterogeneous media from spatial correlation functions is presented. Since many experimental techniques yield two-point correlation functions, the restoration of heterogeneous structures, such as composites, porous materials, microemulsions, ceramics, or polymer blends, is an inverse problem of fundamental importance. Similar to previously proposed algorithms, the new method relies on Monte Carlo optimization, representing the microstructure on a discrete grid. An efficient way to update the correlation functions after local changes to the structure is introduced. In addition, the rate of convergence is substantially enhanced by selective Monte Carlo moves at interfaces. Speedups over prior methods of more than two orders of magnitude are thus achieved. Moreover, an improved minimization protocol leads to additional gains. The algorithm is ideally suited for implementation on parallel computers. The increase in efficiency brings new classes of problems within the realm of the tractable, notably those involving several different structural length scales and/or components.

Atomistic simulation of aging and rejuvenation in glasses

Slow structural relaxation ("aging") observed in many atomic, molecular, and polymeric glasses substantially alters their stress-strain relations and can produce a distinctive yield point. Using Monte Carlo simulation for a binary Lennard-Jones mixture, we have observed these phenomena and their cooling-rate dependences for the first time in an atomistic model system. We also observe that aging effects can be reversed by plastic deformation ("rejuvenation"), whereby the system is expelled from the vicinity of deep minima in its potential energy surface.

Determination of orientational anisotropy in glassy solids by 2D dipolar spectra with sample flipping

A method is proposed for the quantitative measurement of orientational anisotropy in glassy solids based on 2D dipolar NMR spectra with sample flipping (dipolar DECODER experiment). Purely dipolar spectra are obtained by chemical shift refocusing by a multiple pulse sequence. The experiment is applied to an investigation of a doubly 13C-labeled sample of bisphenol-A polycarbonate deformed in a channel-die apparatus. The orientational distribution function is determined by an expansion of the distribution in terms of spherical harmonics up to degree four.

Immunocytochemical discordance in localization of pregnancy specific beta-1 glycoprotein, alpha-fetoprotein and human chorionic gonadotropin in testicular cancers

Immunocytochemical discordance of human chorionic gonadotropin, alpha-fetoprotein and pregnancy specific beta-1 glycoprotein was studied in formaldehyde-fixed tissues of 26 patients with germinal testicular cancer. The cellular localization of these 3 markers has been correlated with the serum markers in the 26 patients. Serum alpha-fetoprotein, human chorionic gonadotropin and specific beta-1 glycoprotein were elevated in 15 of 26 (58 per cent), 17 of 26 (65 per cent) and 7 of 26 (27 per cent) patients, respectively, and in 22 of 26 (85 per cent) when all markers were considered. The cellular alpha-fetoprotein was localized in 5 of 26 (19 per cent), human chorionic gonadotropin in 12 of 26 (46 per cent) and specific beta-1 glycoprotein in 9 of 26 (35 per cent) patients. When all the markers were considered 15 of 26 patients (58 per cent) had either alpha-fetoprotein, human chorionic gonadotropin or specific beta-1 glycoprotein localized in the cancer cells.