A 20-channel receive-only mouse array coil for a 3 T clinical MRI system

A 20-channel phased-array coil for MRI of mice has been designed, constructed, and validated with bench measurements and high-resolution accelerated imaging. The technical challenges of designing a small, high density array have been overcome using individual small-diameter coil elements arranged on a cylinder in a hexagonal overlapping design with adjacent low impedance preamplifiers to further decouple the array elements. Signal-to-noise ratio (SNR) and noise amplification in accelerated imaging were simulated and quantitatively evaluated in phantoms and in vivo mouse images. Comparison between the 20-channel mouse array and a length-matched quadrature driven small animal birdcage coil showed an SNR increase at the periphery and in the center of the phantom of 3- and 1.3-fold, respectively. Comparison with a shorter but SNR-optimized birdcage coil (aspect ratio 1:1 and only half mouse coverage) showed an SNR gain of twofold at the edge of the phantom and similar SNR in the center. G-factor measurements indicate that the coil is well suited to acquire highly accelerated images.

Coil embolization of an infected superior gluteal artery pseudoaneurysm caused by methicillin-resistant Staphylococcus aureus

We describe the successful selective coil embolization of an infected superior gluteal pseudoaneurysm secondary to methicillin-resistant Staphylococcus aureus (MRSA) in a 36-year old women. The patient presented with a long history of drug abuse and perisacral abscesses due to chronic sacroilitis. The chosen strategy provides a safe and successful management of infected false gluteal artery aneurysm.

Closing the gap between coil and balloon in the neurointerventional armamentarium? Initial clinical experience with a nitinol vascular occlusion plug

INTRODUCTION: The use of vascular plug devices for the occlusion of high-flow lesions is a relatively new and successful procedure in peripheral and cardiopulmonary interventions. We report on the use and efficiency of the Amplatzer vascular plug in a small clinical series and discuss its potential for occlusion of large vessels and high-flow lesions in neurointerventions. METHODS: Between 2005 and 2007 four patients (mean age 38.5 years, range 16-62 years) were treated with the device, in three patients to achieve parent artery occlusion of the internal carotid artery, in one patient to occlude a high-flow arteriovenous fistula of the neck. The application, time to occlusion, and angiographic and clinical results and the follow-up were evaluated. RESULTS: Navigation, positioning and detachment of the device were satisfactory in all cases. No flow-related migration of the plug was seen. The cessation of flow was delayed by a mean of 10.5 min after deployment of the first device. In the procedures involving vessel sacrifice, two devices had to be deployed to achieve total occlusion. No patient experienced new neurological deficits; the 3-month follow-up revealed stable results. CONCLUSION: The Amplatzer vascular plug can be adapted for the treatment of high-flow lesions and parent artery occlusions in the head and neck. In this small series the use of the devices was uncomplicated and safe. The rigid and large delivery device and the delayed cessation of flow currently limit the device's use in neurointerventions.

Orbital venous malformation: percutaneous treatment using an electrolytically detachable fibred coil

PURPOSE: To report the efficacy of percutaneous treatment of an orbital venous malformation with an electrolytically detachable fibred coil. METHODS: We report an instance of radiography-guided percutaneous treatment with an electrolytically detachable fibred coil in a 16-year-old boy with acute, spontaneous, painless proptosis on the left side, which progressed with time. RESULTS: Magnetic resonance imaging, angiography and orbitophlebography revealed a low-flow, intraorbital venous malformation. Percutaneous puncture and drainage were followed by a short remission. Following an acute recurrence, a single detachable fibred coil was deployed via a percutaneous approach under angiographic guidance. No radiological or clinical recurrences were observed over 4 years. CONCLUSIONS: Embolization of a deep orbital venous malformation with detachable fibred coils via a percutaneous approach can be highly effective, and may be considered before proceeding with open surgery.

High-resolution morphological and biochemical imaging of articular cartilage of the ankle joint at 3.0 T using a new dedicated phased array coil: in vivo reproducibility study

OBJECTIVE: The objective of this study was to evaluate the feasibility and reproducibility of high-resolution magnetic resonance imaging (MRI) and quantitative T2 mapping of the talocrural cartilage within a clinically applicable scan time using a new dedicated ankle coil and high-field MRI. MATERIALS AND METHODS: Ten healthy volunteers (mean age 32.4 years) underwent MRI of the ankle. As morphological sequences, proton density fat-suppressed turbo spin echo (PD-FS-TSE), as a reference, was compared with 3D true fast imaging with steady-state precession (TrueFISP). Furthermore, biochemical quantitative T2 imaging was prepared using a multi-echo spin-echo T2 approach. Data analysis was performed three times each by three different observers on sagittal slices, planned on the isotropic 3D-TrueFISP; as a morphological parameter, cartilage thickness was assessed and for T2 relaxation times, region-of-interest (ROI) evaluation was done. Reproducibility was determined as a coefficient of variation (CV) for each volunteer; averaged as root mean square (RMSA) given as a percentage; statistical evaluation was done using analysis of variance. RESULTS: Cartilage thickness of the talocrural joint showed significantly higher values for the 3D-TrueFISP (ranging from 1.07 to 1.14 mm) compared with the PD-FS-TSE (ranging from 0.74 to 0.99 mm); however, both morphological sequences showed comparable good results with RMSA of 7.1 to 8.5%. Regarding quantitative T2 mapping, measurements showed T2 relaxation times of about 54 ms with an excellent reproducibility (RMSA) ranging from 3.2 to 4.7%. CONCLUSION: In our study the assessment of cartilage thickness and T2 relaxation times could be performed with high reproducibility in a clinically realizable scan time, demonstrating new possibilities for further investigations into patient groups.

Syntheses and structures of molybdenum and tungsten complexes capable of epoxidaton and copper coordination polymers and dendrimers

We are interested in the syntheses of new complexes and in their characterization by single crystal X-ray diffraction techniques. Once we understand the structures, studies aimed at understanding uses of these complexes in the field of catalytic epoxidation using complexes soluble in water and syntheses of thin films (not assessed) were conducted. The syntheses, characterization and catalytic properties of a series of mononuclear, dinuclear and tetranuclear molybdenum and tungsten oxo complexes are described. The syntheses and structural characterization of two copper coordination polymers with 3,5-dihydroxylbenzoate ligand, and five paddlewheel shaped copper dendrimers coordinated with Fréchet-type dendrons are also detailed. The background of this dissertation is outlined in Chapter 1. Chapter 2 describes the syntheses, and characterization of two new mononuclear molybdenum(VI) and tungsten(VI) oxo complexes, MoO2Cl2(OPPh2CH2OH)2, and WO2Cl2(OPPh2CH2OH)2, bearing hydrophilic phosphine oxide ligand. The catalytic properties of these complexes for the epoxidation of cis-cyclooctene were also studied. Two new dinuclear molybdenum(VI) and tungsten(VI) oxo complexes Mo2O4Cl2[(HOCH2)PhPOO]2, and (CH3O)2(O)W(μ-O)(μ-O2PPh2)2W(O)(CH3O)2, bearing organophosphinate ligand are described in Chapter 3 and 4. Chapter 4 and 5 describes the syntheses and characterization of tetranuclear molybdenum(V) oxo complexes bearing various organophosphinate ligands. The catalytic abilities of these complexes for the epoxidation of cis-cyclooctene in the presence of hydrogen peroxide as oxidant were explored as well. Various spectroscopic methods, such as IR, UV-vis, and NMR are used to characterize the nature of these complexes. Crystal structures of compounds MoO2Cl2(OPPh2CH2OH)2, WO2Cl2(OPPh2CH2OH)2, Mo2O4Cl2[(HOCH2)PhPOO]2, (CH3O)2(O)W(μ-O)(μ-O2PPh2)2W(O)(CH3O)2, and Mo4(µ3-O)4(µ-O2PR2)4O4 (R=Ph, Me, ClCH2, o-C6H4(CH2)2) are also presented. The syntheses, and structural characterization of three copper(II) coordination polymers bearing 3,5-dihydroxybenzoate ligand are described in Chapter 6. Two copper(II) coordination polymers, [Cu2(3,5-dhb)2(pyridine)4]n, and [Cu2(3,5-dhb)4]n were afforded based on different amount of pyridine used in the reaction. The structures of these complexes are further built into 2D or 3D networks via inter or intra hydrogen bonds. The syntheses and structural characterization of the zinc(II) monomer, Zn(3,5-dhb)2(pyridine)2 is also described in this Chapter. Chapter 7 describes the syntheses, and characterization of five dendronized dicopper complexes bearing different generations of Fréchet-type dendrons. The structures of 3,5- bis(benzoyloxl)benzoic acid, 3,5-(PhCOO)2PhCOOH (G1), Cu2(3,5-dhb)4(THF)2, Cu2(G1)4(pyridine)2, and Cu2(G1)4(CH3OH)2 were characterized unambiguously by single X-ray diffraction. In addition, all compounds were characterized by FT-IR, UV-vis spectroscopy and elemental analyses.

Significance of coil orientation for motor evoked potentials from nasalis muscle elicited by transcranial magnetic stimulation

OBJECTIVE: In transcranial magnetic stimulation (TMS) of the motor cortex, the optimal orientation of the coil on the scalp is dependent on the muscle under investigation, but not yet known for facial muscles. METHODS: Using a figure-of-eight coil, we compared TMS induced motor evoked potentials (MEPs) from eight different coil orientations when recording from ipsi- and contralateral nasalis muscle. RESULTS: The MEPs from nasalis muscle revealed three components: The major ipsi- and contra-lateral middle latency responses of approximately 10 ms onset latency proved entirely dependent on voluntary pre-innervation. They were most easily obtained from a coil orientation with posterior inducing current direction, and in this respect resembled the intrinsic hand rather than the masseter muscles. Early short duration responses of around 6 ms onset latency were best elicited with an antero-lateral current direction and not pre-innervation dependent, and therefore most probably due to stimulation of the nerve roots. Late responses (>18 ms) could inconsistently be elicited with posterior coil orientations in pre-innervated condition. CONCLUSIONS: By using the appropriate coil orientation and both conditions relaxed and pre-innervated, cortically evoked MEP responses from nasalis muscle can reliably be separated from peripheral and reflex components and also from cross talk of masseter muscle activation.

Impact of coil position and electrophysiological monitoring on determination of motor thresholds to transcranial magnetic stimulation

OBJECTIVE: We compared motor and movement thresholds to transcranial magnetic stimulation (TMS) in healthy subjects and investigated the effect of different coil positions on thresholds and MEP (motor-evoked potential) amplitudes. METHODS: The abductor pollicis brevis (APB) 'hot spot' and a standard scalp position were stimulated. APB resting motor threshold (APB MEP-MT) defined by the '5/10' electrophysiological method was compared with movement threshold (MOV-MT), defined by visualization of movements. Additionally, APB MEP-MTs were evaluated with the '3/6 method,' and MEPs were recorded at a stimulation intensity of 120% APB MEP-MT at each position. RESULTS: APB MEP-MTs were significantly lower by stimulation of the 'hot spot' than of the standard position, and significantly lower than MOV-MTs (n=15). There were no significant differences between the '3/6' and the '5/10' methods, or between APB MEP amplitudes by stimulating each position at 120% APB MEP-MT. CONCLUSIONS: Coil position and electrophysiological monitoring influenced motor threshold determinations. Performing 6 instead of 10 trials did not produce different threshold measurements. Adjustment of intensity according to APB MEP-MT at the stimulated position did not influence APB MEP amplitudes. SIGNIFICANCE: Standardization of stimulation positions, nomenclature and criteria for threshold measurements should be considered in design and comparison of TMS protocols.

The Testing and Concentration of a Tungsten Ore

At the present time the principal uses for tungsten lie in the manufacture of ferro-alloys and tungsten steels. Due to it’s hardening and strengthening characteristics it holds an important position among steel hardening metals. The great rush for it’s production during the World War years clearly points to it’s importance in the manufacture of armament.