bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron transport through single phenylene–ethynylene molecular junctions at low temperature
Authors: Khondaker Saiful I. , Yao Zhen , Cheng Long , Henderson Jay C. , Yao Yuxing , Tour James M.
Published: July 2004

We present low-temperature electron transport measurements of individual phenylene–ethynylene molecular wires, connected to nanometer-spaced gold electrodes. Low-bias current–voltage (I–V) characteristics measured at 4.2K are stable and show irregular steps. After application of a large voltage, the low-bias I–V curves switch between different stable configurations, some of which show negative differential resistance (NDR). Similar behavior, including the NDR, has been observed in molecules irrespective of whether they contain a NO2 side group or not. We suggest that different I–V curves measured, including the NDR, could be due either to conformational changes in the molecules or a change in coupling of the molecular junction.
Copper-related degradation of SiO2 in metal–oxide–semiconductor capacitors subjected to bias thermal stress: Leakage of the minority charge carriers in the inversion layer
Authors: Kohn A. , Lipp E. , Eizenberg M. , Shacham-Diamand Y.
Published: July 2004

We describe a mechanism of Cu-related degradation of SiO2 in metal–oxide–semiconductor capacitors subjected to bias thermal stress (BTS). The commonly used stress of bias larger than 1MV∕cm at 300°C results in increased oxide conductivity, which is large enough to enable the leakage of minority carrier charge generated at the inversion layer, while the oxide capacitance and high-frequency deep depletion capacitance can still be accurately measured. This is an intermediate degradation between the commonly reported flat-band voltage shifts and decrease in the breakdown voltage of the oxide. This phenomenon does not occur following BTS when the metallization is Al, or following thermal stress, even in Cu.
Broad-area laser diode with 0.02nm bandwidth and diffraction limited output due to double external cavity feedback
Authors: Chen Jun , Wu Xiaodong , Ge Jianhong , Hermerschmidt Andreas , Eichler Hans Joachim
Published: July 2004

External cavity feedback for a broad-area laser diode (BAL) with antireflection coating on the front facet is investigated experimentally. The feedback is created by a high-reflection mirror and a blazed grating, which reflect two parts of the laser emission back to the BAL, thereby forming an external resonator. When a Fabry–Perot etalon was inserted into the resonator an output beam with a bandwidth of 0.02nm and power of 150mW was obtained. The beam diffraction limited factor amounted to M2=1.16.
Current–voltage characteristics of a tetracene crystal:Space charge or injection limited conductivity?
Authors: Reynaert J. , Arkhipov V. I. , Borghs G. , Heremans P.
Published: July 2004

We show that current–voltage characteristics, measured on a tetracene crystal sandwiched between two gold electrodes, are in quantitative agreement with the concept of dopant-assisted charge injection across a metal–organic interface. This notion explains the wild range of carrier mobilities recently found by space-charge limited current measurements in apparently identical tetracene crystals [de Boer et al., J. Appl. Phys. 95, 1196 (2004)] and the difference between these data and the mobility measured in the time-of-flight experiments.
Diffusion barrier properties of carboxyl- and amine-terminated molecular nanolayers
Authors: Ganesan P. G. , Singh A. P. , Ramanath G.
Published: July 2004

Molecular nanolayers are attractive for preserving the integrity of Cu-dielectric interface in sub-50nm interconnect structures. Here, we demonstrate the use of carboxyl- and amine-terminated self-assembled molecular layers (SAMs) to immobilize Cu at the Cu∕SiO2 interface. Amine-terminated SAMs at the Cu∕SiO2 interface increase the Cu diffusion-induced device failure time by a factor of 3 compared to interfaces without a barrier. Carboxyl-terminated SAMs obtained by grafting succinyl chloride onto the amine-terminated SAM show more than an additional factor of 4 increase in failure time. Coordination complex formation though strong interactions between COOH and Cu+ at the Cu∕SAM interface is the likely reason for the effective immobilization of Cu.
Fabrication of strain tunable infrared frequency selective surfaceson electrostrictive poly(vinylidene fluoride–trifluoroethylene) copolymer films using a stencil mask method
Authors: Ye Yong-Hong , Jeong D.-Y. , Zhang Q. M.
Published: July 2004

We introduce a stencil mask method to fabricate metallic patch arrays on the electrostrictive poly(vinylidene fluoride–trifluoroethylene) copolymer films. The resulting frequency selective surfaces exhibit resonance responses in the infrared region. Furthermore, the resonant frequency can be tuned by the strain change in the copolymer films. The results demonstrate that the stencil mask method is useful for depositing metallic patterns on a subset of substrates such as polymers that would be damaged by solvents used in conventional photolithography techniques.
Growth and photoluminescence characteristics of AlGaAs nanowires
Authors: Wu Z. H. , Sun M. , Mei X. Y. , Ruda H. E.
Published: July 2004

Growth of high-quality single-crystal AlGaAs nanowires was demonstrated using the vapor–liquid–solid (VLS) mechanism with molecular-beam epitaxy (MBE). Highly ordered AlGaAs nanowire arrays and GaAs∕AlGaAs multilayer nanowires were also prepared. Photoluminescence (PL) from homogeneous AlGaAs and GaAs∕AlGaAs multilayer nanowires was measured. The Al composition of the AlGaAs nanowires was found to be significantly lower than that for planar MBE films grown under the same conditions, as determined from PL and energy-dispersive x-ray spectroscopy measurements. This is explained in terms of the different growth mechanisms for VLS and normal MBE. Such AlGaAs nanowires are expected to have a wide range of applications in electronic and photonic devices.
Enhanced photoelectrolysis of water with photoanode Nb:SrTiO3
Authors: Yin Jiang , Ye Jinhua , Zou Zhigang
Published: July 2004

The photoelectrolysis of water has been investigated in a photoelectrochemical cell with the single-crystal photoanodes Nb:SrTiO3 (0mol%, 0.07mol%, and 0.69mol%) and the electrolyte Na2SO4(0.1M,pH=5.92). The Nb:SrTiO3 anodes (0.07mol% and 0.69mol%) show much higher photocurrent density than the pure SrTiO3 anode in several orders of magnitude. The incident photon to current conversion efficiencies at 298.2nm and an applied potential 1.5V (versus the saturated calomel electrode) for three Nb:SrTiO3 (0mol%, 0.07mol%, and 0.69mol%) anodes are 0.92%, 15.67%, and 4.32%, respectively. The transmittance spectra of the Nb:SrTiO3 show an obvious optical absorption around 516nm (∼2.4eV). It is interpreted that two-photon process takes part in the charge transfer from the valence band to the conduction band through the intermediate states induced by Nb doping.
Spin-dependent transmission through a chain of rings: Influenceof a periodically modulated spin–orbit interaction strength or ring radius
Authors: Molnár B. , Vasilopoulos P. , Peeters F. M.
Published: July 2004

We study ballistic electron transport through a finite chain of quantum circular rings in the presence of spin–orbit interaction of strength α. For a single ring, the transmission and reflection coefficients are obtained analytically and from them the conductance for a chain of rings as a function of α and of the wave vector k of the incident electron. We show that due to destructive spin interferences, the chain can be totally opaque for certain ranges of k, the width of which depends on the value of α. A periodic modulation of the strength α or of the ring radius widens the gaps considerably and produces a nearly binary conductance output.
Interband type-II miniband-to-bound state diode lasers for the midinfrared
Authors: Mermelstein C. , Schmitz J. , Kiefer R. , Walther M. , Wagner J.
Published: July 2004

A design for midinfrared diode lasers based on interband type-II miniband-to-bound state transitions is proposed and has been demonstrated experimentally. Type-II miniband-to-bound state laser structures emitting at 3.25μm with active regions consisting of 5 and 10W periods were grown by solid-source molecular-beam epitaxy and processed into ridge waveguide lasers. Substrate-side down mounted devices with a 10 period active region and uncoated facets could be operated in continuous-wave (cw) mode up to 185K and as high as 260K in pulsed mode. A high characteristic temperature of 100K has been achieved for heat-sink temperatures below 140K, decreasing to 33K for the 140 to 185K interval. At 110K, a 5 period laser structure exhibited a threshold current density of 177A∕cm2 and a slope efficiency of 61mW∕A. Single-ended output powers of 144mW in cw mode and exceeding 330mW in pulsed operation were obtained for a substrate-side down mounted 5 period diode laser with high-reflection∕antireflection coated mirror facets, operated at 110K.
Multiplex nonresonant pump four-wave mixing
Authors: Lee Eun Seong , Choi Dae Sik , Lee Jae Yong , Hahn Jae Won
Published: July 2004

We propose a scheme of multiplex nonresonant pump four-wave mixing (NRP-FWM) process which is highly immune to saturation problems. The process is accomplished with two high-intensity pump beams detuned far from the resonance of the sample under investigation and a resonant probe beam as weak as possible not to give rise to nonlinear absorption. Only a single-broadband probe beam is used for the multiplex experiment to detect the electronic swan band spectrum of C2 molecules in a premixed acetylene–oxygen flame. Comparing the signal of the degenerate four-wave mixing (DFWM) experiment on the same sample, we found that the signal level at which the NRP-FWM starts to show saturation is about 250 times higher than in the case of the DFWM.
Evidence for a vacancy and interstitial mediated diffusion of As in Si and Si0.9Ge0.1
Authors: Uppal Suresh , Willoughby Arthur F. W. , Bonar Janet M. , Zhang Jing
Published: July 2004

Arsenic diffusion has been studied at 1000°C in Si and relaxed Si0.9Ge0.1 structures grown using molecular beam epitaxy. Intrinsic diffusivity of As in Si0.9Ge0.1 is shown to be enhanced over Si by a factor of 2, in agreement with the literature. Using selective point defect injection, obtained by surface reactions achieved using rapid thermal annealing process under oxygen atmosphere, clear evidence of the participation of both vacancy and interstitial defects in the diffusion process of As in Si as well as Si0.9Ge0.1 is obtained. Qualitatively, a higher contribution of vacancies in Si0.9Ge0.1 than in Si is apparent.
Specific heat and related thermodynamic properties of an undercooled germanium melt
Authors: Li Q. , Zhu Y. Y. , Liu R. P. , Li G. , Ma M. Z. , Yu J. K. , He J. L. , Tian Y. J. , Wang W. K.
Published: July 2004

Embedded in a flux of dehydrated B2O3, melts of pure germanium were undercooled by repeated melting and solidification of the specimens within a differential scanning calorimeter facility. The highest undercooling obtained in this way was 190K. The specific heat of the undercooled melt was measured by calorimetric diagnostics within the facility, and showed a linear dependence on temperature. The thermodynamic properties of germanium, such as the difference of Gibbs free energy, the difference of entropy, and the difference of enthalpy between the undercooled melt and the solid state, were derived from the measured specific heat.
Nanosize fabrication using etching of phase-change recording films
Authors: Shintani Toshimichi , Anzai Yumiko , Minemura Hiroyuki , Miyamoto Harukazu , Ushiyama Junko
Published: July 2004

An etching technique called phase-change etching was developed. In this technique, only crystalline regions in a phase-change recording film are selectively etched by an alkaline solution, and amorphous regions remain on the sample surface, which means that a phase-change recording film can be used as a resist for pattern formation. By combination of this technique and phase-change recording, fabrication of the dot pattern with a size of about 1∕10 of the fabricating spot was demonstrated. This result indicates the possibility of nanosize fabrication using the phase-change etching technique.
Molecular level control of donor/acceptor heterostructuresin organic photovoltaic devices
Authors: Pradhan Basudev , Bandyopadhyay Anirban , Pal Amlan J
Published: July 2004

We have fabricated donor/acceptor-type organic photovoltaic devices based on copper phthalocyanine and Rose Bengal with varied number of donor/acceptor interfaces. Device architecture, namely, the number of such interfaces in the molecular scale, has been controlled via layer-by-layer electrostatic self-assembled film deposition technique. The interface area between donor and acceptor has been varied in order to optimize effective exciton separation and carrier transport. The number of donor/acceptor interfaces has opposite effects on exciton dissociation and charge transport in the devices. The results show that interface area has to be optimized to enhance the combined effect of exciton dissociation and carrier transport in organic photovoltaic devices.
Low-temperature study of nonlinear transport across oxide grain boundaries
Authors: Shao Rui , Vavro Juro , Bonnell Dawn A.
Published: July 2004

Reduced 36.8° (Σ5) and 24° SrTiO3 bicrystals with carrier concentrations on the order of 1×1017to1.0×1018cm−3 were studied with dc transport measurement from room temperature to 1.4K. For lightly reduced samples, nonlinearity in I–V curves was observed at very low temperatures indicating the existence of a small grain-boundary potential barrier and the transport mechanism can be rationalized in terms of tunneling through a disordered region associated with the boundary. Samples with further reduction showed no nonlinearity. This reduction-dependent phenomenon is proposed to be due to the oxygen vacancy segregation to the grain boundary.
Nanoscale photothermal and photoacoustic transients probedwith extreme ultraviolet radiation
Authors: Tobey R. I. , Gershgoren E. H. , Siemens M. E. , Murnane M. M. , Kapteyn H. C. , Feurer T. , Nelson K. A.
Published: July 2004

We demonstrate the use of extreme ultraviolet (EUV) light for time-resolved measurements of the photothermal and photoacoustic response of materials. By using wavelengths that are 20× shorter than visible light, we demonstrate the potential for dramatically increased sensitivity and signal levels, in some cases by almost two orders of magnitude compared with visible light. This approach will enable probing of surface acoustic dynamics on nano-scale spatial dimensions of 50nm and below, using a small scale coherent EUV sources employing high-harmonic generation.
Aging effects around the glass and melting transitions inpoly(dimethylsiloxane) visualized by resistance measurements
Authors: Brom H. B. , Romijn I. G. , Magis J. G. , Vleuten M. van der , Michels M. A. J.
Published: July 2004

The process of aging in rubbers requires monitoring over long periods (days to years). To do so in nonconducting rubbers, small amounts of carbon-black particles were dispersed in a fractal network through the rubber matrix, to make the rubber conducting without modifying its properties. Continuous monitoring of the resistance reveals the structural changes around the glass and melting transitions and especially details about the hysteresis and aging processes. We illustrate the method for the semicrystalline polymer poly(dimethylsiloxane).
InP
photonic crystal membrane structures: Fabrication accuracy and optical performance
Authors: Xing Aimin , Darvanco Marcelo , Blumenthal Daniel J , Hu Evelyn L
Published: July 2004

Two-dimensional photonic crystal membranes with coupled ridge waveguides were fabricated in InP∕InGaAsP by using e-beam lithography and reactive ion etching. The optical transmission characteristics were measured and a photonic band gap with better than 20dB extinction ratio was observed. The band-gap dependence on radius-to-lattice constant ratio (r∕a) was numerically and experimentally investigated. Predictable, accurate placement of the band edge by varying r∕a is demonstrated.
Spin blockade in capacitively coupled quantum dots
Authors: Rogge M. C. , Fühner C. , Keyser U. F. , Haug R. J.
Published: July 2004

We present transport measurements on a lateral double dot produced by combining local anodic oxidation and electron beam lithography. We investigate the tunability of our device and demonstrate that we can switch on and off tunnel coupling between both dots in addition to capacitive coupling. In the regime of pure capacitive coupling, we observe the phenomenon of spin blockade in a magnetic field and analyze the influence of capacitive interdot coupling on this effect.
Additional phonon modes and close satellite valleys crucialfor electron transport in hexagonal gallium nitride
Authors: Brazis R. , Raguotis R.
Published: July 2004

Conventional models of electron transport in hexagonal GaN crystals predicting electron drift velocity peak value up to 3.2×107cm∕s at 140–220kV∕cm and a pronounced negative differential mobility at higher fields are revised. The new model is suggested accounting for the additional low-energy optical phonon modes (∼26meV) and the satellite valley location close (400meV) to the conduction band bottom. Electron scattering on these and conventional (∼92meV) LO-phonon modes together with the fast intervalley exchange is shown to limit electron drift velocity (<1.9×107cm∕s at T=300K), in excellent agreement with the time-of-flight experiment.
New approach for the measurement of damping properties of materials using the Oberst beam
Authors: Wojtowicki Jean-Luc , Jaouen Luc , Panneton Raymond
Published: July 2004

The Oberst method is widely used for the measurement of the mechanical properties of viscoelastic or damping materials. The application of this method, as described in the ASTM E756 standard, gives good results as long as the experimental set-up does not interfere with the system under test. The main difficulty is to avoid adding damping and mass to the beam owing to the excitation and response measurement. In this paper, a method is proposed to skirt those problems. The classical cantilever Oberst beam is replaced by a double sized free-free beam excited in its center. The analysis is based on a frequency response function measured between the imposed velocity at the center (measured with an accelerometer) and an arbitrary point on the beam (measured with a laser vibrometer). The composite beam (base beam + material) properties are first extracted from the measurement by an optimization algorithm. Young’s modulus and structural damping coefficient of the material under test can be deduced using classical formulations of the ASTM E756 standard for typical materials or using a finite element model for more complex cases. An application to a thick and soft viscoelastic material is presented, the results are shown to be consistent with Kramers–Kronig relations.
Surface density enhancement of gold in silica film under laser irradiation at 355nm
Authors: Jonnard P. , Dufour G. , Rullier J.-L. , Morreeuw J.-P. , Donohue J. T.
Published: July 2004

In order to understand the damage mechanisms inside the optics of the high power laser facilities, a model sample has been prepared by introducing gold nanoparticles into a silica film. The mean diameter of the gold clusters is 2.5nm. Different parts of the sample were irradiated at wavelength 355nm and fluences up to 1J∕cm2. By looking with x-ray photoelectron spectroscopy at the intensity of the Au4f peak relative to that of the Si2p peak, a surface Au density enrichment is observed. We interpret this as indicating that the gold atoms migrate toward the surface upon the laser irradiation.
Stabilized atomic force microscopy imaging in liquids using second harmonic of cantilever motion for setpoint control
Authors: Schiener Jens , Witt Susanne , Stark Martin , Guckenberger Reinhard
Published: July 2004

We present an automated stabilization of the imaging process in tapping mode atomic force microscopy. For biological applications, the requirement of stable imaging conditions to achieve reliable high resolution is contradicted by the necessity to work in solution to ensure biological functionality: thermal and saline variations of the viscosity, in particular when exchanging the solution the sample is surrounded with, strongly affect the cantilever motion rendering the imaging process instable. Using anharmonic contributions in the deflection signal, the amplitude setpoint is controlled to compensate for unavoidable drift in the free oscillation. By this additional feedback, the tip–sample interaction is maintained stable at a low value, making the instrument robust against drift and tolerant to environmental changes. As a delicate test sample, the “single ring”-mutant of the bacterial chaperonin GroEL from E. coli was imaged. To prove the efficiency of our setup, we show highly stabilized, continuous imaging with minimized user interaction while strong perturbations by exchange of the buffer solution were imposed during the scanning.
The role of πσ* state in intramolecular electron-transfer dynamics of 4-dimethylaminobenzonitrile and related molecules
Authors: Zgierski Marek Z. , Lim Edward C.
Published: July 2004

Evidence is presented which indicates that the photoinduced intramolecular charge transfer (ICT) in 4-dimethylaminobenzonitrile proceeds by a new mechanism in which πσC≡N* state is the intermediate of a consecutive process that takes the initially excited ππ* state to the fully charge-separated ICT state. The absence of the ICT-state formation in 4-aminobenzonitrile is attributed to the smaller electron-donor strength of the amino group relative to the dimethylamino group, which hinders the πσ*→ICT charge-shift reaction.
Endovascular coil embolization of residual or recurrent aneurysms after surgical clipping
Authors: Cekirge H.S. , Islak C. , Firat M.M. , Kocer N. , Saatci I.
Published: July 2004

Purpose: Treatment of residual or recurrent aneurysms after surgical clipping is a challenge and most surgeons prefer to avoid a second surgical attempt. We present treatment of 4 residual or recurrent aneurysms after surgical clipping with electrolytically detachable coils.

Material and Methods: In 3 of 4 patients, recurrent aneurysms were diagnosed with angiography 2 months, 5 years and 14 years after surgery, although the domes of the aneurysms were opened following clipping during the surgery. In the 4th patient, an early postoperative angiogram revealed filling of a residual aneurysm secondary to the incomplete neck clipping. Guglielmi detachable coils were used to occlude the residual or recurrent aneurysm.

Results: The endovascular approach was successful in all patients and the control angiograms showed complete obliteration of the aneurysms with no recanalization.

Conclusion: The endovascular approach is a good treatment option for patients in whom complete obliteration of the aneurysm cannot be achieved by surgical clipping. Opening of the aneurysm sac after clipping does not necessarily preclude aneurysm regrowth from a neck remnant proximal to the clip.
Infantile hemangioendothelioma: A case report
Authors: Kaniklides C. , Dimopoulos P.A. , Bajic D.
Published: July 2004

The case of a 3-month-old boy with a hepatic infantile hemangioendothelioma is reported. There was no previous history of disease and no symptoms, only an incidentally found abdominal mass. The case is presented as an example of establishing the diagnosis, deciding upon the treatment, and performing the follow-up using only non-invasive imaging techniques.
Evaluation of new sclerotic bone metastases in breast cancer patients during treatment
Authors: Çiray I. , Åström G. , Andréasson I. , Edekling T. , Hansen J. , Bergh J. , Ahlström H.
Published: July 2004

Purpose: According to the World Health Organization (WHO) criteria for response of bone metastases to therapy, new lesions indicate progressive disease. We intended to prove that a new sclerotic lesion on conventional radiography may also be a sign of a positive therapeutic response in a previously undetectable lytic metastasis.

Material and Methods: In a previous placebo-controlled clinical trial of clodronate (Ostac) therapy, 139 breast cancer patients with bone metastases underwent both conventional radiography and bone scan every 6 months for 2 years with 99mTc before and during clodronate treatment. WHO criteria were applied for therapy response evaluation.

Results: In 24 patients, 52 new sclerotic lesions observed during therapy were selected for re-evaluation of conventional radiographs and bone scans. In 8 of the 24 patients, 17 of 52 new sclerotic lesions (33%) had showed positive uptake on previous bone scans. These lesions were possibly misinterpreted as new when applying WHO criteria.

Conclusion: For better assessment of new sclerotic lesions during treatment, more sensitive techniques, e.g. bone scan, are needed as a complement to conventional radiography.
Imaging of aortoiliac arterial disease: Duplex ultrasound and MR angiography versus digital subtraction angiography
Authors: Lundin P. , Svensson Å. , Henriksen E. , Jonason T. , Forssell C. , Bäckbro B. , Bodlund M. , Ringqvist I.
Published: July 2004

Purpose: To evaluate and compare the diagnostic accuracy of duplex ultrasound (US) and MR angiography (MRA) at 1.0 T in aortoiliac arterial disease using digital subtraction angiography (DSA) as the reference standard. In addition, a comparison of the 2D time-of flight (TOF) and 3D contrast-enhanced MRA (CE MRA) techniques was performed.

Material and Methods: Prospectively, 39 patients with symptoms of lower-extremity arterial occlusive disease were examined using US, TOF MRA, CE MRA and DSA. Significant lesions (stenosis ≥50%) and occlusions were evaluated blindly for each method.

Results: For all segments, the sensitivity for US, TOF MRA and CE MRA with regard to significant lesions was 0.72, 0.81 and 0.81, respectively, and the specificity for each was 0.97, 0.91 and 0.92, respectively. For significant lesions above the inguinal ligament the corresponding sensitivity was 0.84, 0.89 and 0.94 and the specificity 0.93, 0.82 and 0.73, respectively. The specificity was higher when the two MRA methods were combined. TOF MRA overgraded 7 segments as occluded. In most cases, the length of the occlusions was correctly determined on CE MRA, overestimated on TOF MRA and uncertain on US.

Conclusion: Neither US nor MRA were sufficiently accurate to fully replace angiography. MRA was preferable to US as a non-invasive test when vascular intervention was contemplated. Although CE MRA was superior to TOF MRA, the most accurate results were achieved when the two methods were combined.
Improved Peripheral MRA using Multi-Velocity-Encoding Phase Contrast-Enhanced MRA Techniques
Authors: Goyen M. , Heuser L.J.G.
Published: July 2004

Phase contrast MR angiography (PC-MRA) depends on phase shifts caused by blood flow. Generally, PC sequences employ one VENC (velocity-encoding) value for each encoded spatial direction to optimize the signal in major vessels during peak systolic flow. We compared a mono- (30) with a multi- (20/30/45) VENC-PC-MRA technique in 10 patients with peripheral arterial occlusive disease. In all patients, the multi-VENC-PC sequence enhanced the vascular signal in vessels with very different flow velocities in one measurement. Large fields-of-view can be measured in a relatively short examination time to obtain an overview of the peripheral arterial system of the patient when contrast-enhanced MRA is not possible.
Bread and barium: Diagnostic value in patients with suspected primary esophageal motility disorders
Authors: Nellemann H. , Aksglaede K. , Funch-Jensen P. , Thommesen P.
Published: July 2004

Purpose: To evaluate the significance of bread and barium studies as a diagnostic tool as well as a supplement to manometric investigation of the esophagus in patients with suspected esophageal motility disorders.

Material and Methods: Eighty-nine patients suspected for primary esophageal motility disorders were examined. All patients were interviewed before the investigation to determine the prevalence of symptoms like heartburn, chest pain, and dysphagia. The patients underwent simultaneous roentgenologic and manometric investigations in the supine position during wet and solid barium swallow, and during continuous drinking, followed by investigation for gastroesophageal reflux (GER). The manometric examination was performed with triple-lumen catheters connected to a hydraulic capillary infusion system and external transducers.

Results: All patients with normal esophageal clearing (n=31) had normal manometry. Patients with delayed esophageal clearing (n=58) required manometry for identifying concommittant motility disorders; achalasia and diffuse esophageal spasms were found only in patients with delayed liquid and solid emptying. GER and/or esophageal rings was demonstrated in 31 patients.

Conclusion: We suggest bread and barium as the first diagnostic step in patients with clinical suspicion of primary esophageal motility disorders.
Dynamic MR imaging of liver metastases with Gd-EOB-DTPA
Authors: Stern W. , Schick F. , Kopp A.F. , Reimer P. , Shamsi K. , Claussen C.D. , Laniado M.
Published: July 2004

Purpose: To assess liver and lesion enhancements by dynamic MR imaging after bolus injection of the hepatobiliary contrast agent gadolinium ethoxybenzyldiethylenetriamine-pentaacetic acid (Gd-EOB-DTPA) in patients with liver metastases and to compare the effect of different doses.

Material and Methods: A randomized double-blinded trial with doses of 12.5, 25 and 50 µmol/kg Gd-EOB-DTPA was performed in 35 patients with liver metastases. Liver enhancement, tumor enhancement and liver lesion contrast-to-noise (C/N) ratios were calculated from breath-hold gradient echo images (100/5/80°) recorded precontrast and at different times up to 10 min postcontrast.

Results: Normal liver showed a characteristic enhancement pattern, with a rapid enhancement in the first 45 s postcontrast and a slight but significant further increase up to 600 s. The initial enhancement in the lesions was also pronounced, but the enhancement was slightly decreased after 240 s postcontrast. At dose levels of 12.5 and 25 µmol/kg Gd-EOB-DTPA, C/N ratios significantly increased compared to baseline from 90 to 600 s. Postcontrast C/N-values obtained using 50 µmol/kg Gd-EOB-DTPA were not significantly increased, except for the examinations 480 s postcontrast.

Conclusion: In liver metastases, C/N ratios obtained with doses of 12.5 and 25 µmol/kg Gd-EOB-DTPA were slightly superior to 50 µmol/kg Gd-EOB-DTPA. This finding is probably due to a more pronounced extracellular effect of the contrast medium at higher doses.
MR Cholangiography in Massive Hepatobiliary Ascariasis: A case report
Authors: Fitoz S. , Atasoy Ç.
Published: July 2004

The ultrasonographic and MR cholangiographic findings in a patient with massive hepatobiliary ascariasis are described.
Esophageal Rings and Strictures: Manometric characteristics in patients with food impaction
Authors: Røhl L. , Aksglæde K. , Funch-Jensen P. , Thommesen P.
Published: July 2004

Purpose: The purpose was to investigate the manometric characteristics in patients with lower esophageal rings or strictures with special reference to food impaction.

Material and Methods: The material comprised 344 patients (158 female and 186 male). Lower esophageal rings or strictures were diagnosed radiologically by the full column technique. Manometry was performed with triple lumen catheters connected to a hydraulic capillary system and external transducers.

Results: Forty patients had rings, and 21 patients strictures. The reference group comprised 283 patients. Dysphagia was seen most frequently in patients with rings. Food impaction was seen only in patients with rings or strictures, whereas chest pain and heartburn appeared with the same incidence in all 3 groups. Non-specific motor disorders were seen most frequently in patients with strictures, but as delayed esophageal emptying with no influence on the tendency to food impaction. Only ring diameter, but not stricture diameter, was of any significance with a higher incidence of food impaction in patients with narrow rings.

Conclusion: Radiology rather than manometry should be the first diagnostic step in patients with benign dysphagia suffering from food impaction.
Transrectal US and Endorectal MR Imaging in Partial and Complete Obstruction of the Seminal Duct System: A comparative study
Authors: Engin G. , Kadioǧlu A. , Orhan I. , Akdöl S. , Rozanes I.
Published: July 2004

Purpose: To evaluate transrectal ultrasonography (US) and MR imaging findings of infertile patients with suspected complete or partial obstruction of the seminal duct system.

Material and Methods: Two hundred and eighteen infertile patients with low ejaculate volume were evaluated by transrectal US. Endorectal MR imaging was performed on 62/218 patients. Prostatic cysts, ejaculatory duct (ED) dilatation (>2 mm in width), ED calculi or calcifications, seminal vesicle (SV) dilatation (a.p. diameter >15 mm), SV hypo/agenesis (a.p. diameter <7 mm), SV cysts (>5 mm), vasal agenesis and chronic prostatitis (coarse calcifications, heterogeneity in prostate) were considered significant findings for obstruction of the seminal duct system.

Results: Pathologic findings were detected in 75% and 61% of patients with azoospermia on transrectal US and MR imaging, respectively. Transrectal US and MR imaging did not reveal any pathologies in 64.7% and 59.1% of patients with nonazoospermia, respectively. The incidences of hypoplastic/atrophic SV (12/48 vs. 5/170), SV agenesis (6/48 vs. 1/170), vasal agenesis (5/48 vs. 1/170) were significantly higher in the azoospermic subgroup ( p < 0.002).

Conclusion: US is a good method for initial evaluation of these patients – especially in complete obstruction. Endorectal MR imaging should be reserved for selected patients in whom results of transrectal US are not conclusive.
Us Versus Conventional Radiography in the Diagnosis of Sternal Fractures
Authors: Engin G. , Yekeler E. , Güloǧlu R. , Acunaş B. , Acunaş G.
Published: July 2004

Purpose: To investigate the value of ultrasonography (US) in the diagnosis of sternal fractures.

Material and Methods: Twenty-three patients (mean age 35.4 years) with a clinical suspicion of sternal fracture after blunt chest trauma were retrospectively reviewed. At admission, a.p. and lateral chest radiographies and sternal US were obtained. Sternal fractures were classified as nondisplaced or displaced. US and conventional radiographic findings were compared.

Results: In 3/23 (13.0%) of the patients, no fracture was found by radiography or by US. Both radiography and US demonstrated sternal fractures in 16/23 (69.6%) of the patients. Sternal fractures were detected only by US while the conventional radiography was negative in 2/23 (8.7%) cases. Also in 2/23 (8.7%) of the patients with US positive for fracture, radiographies were suspicious. In 2 patients, the degree of fracture displacement on US was lesser than that found by radiography.

Conclusion: US was better than lateral radiography to diagnose sternal fractures; however, conventional radiography remains the standard means of demonstrating grade of displacement.
Neurologic Complications of Cerebral Angiography: A retrospective study of complication rate and patient risk factors
Authors: Leffers A. , Wagner A.
Published: July 2004

Purpose: To evaluate the neurologic complication rate and individual patient risk factors in cerebral angiographies using the digital subtraction angiography (DSA) technique and non-ionic contrast media in a department with many radiologists in training.

Material and Methods: A retrospective study of 483 cerebral angiographic examinations in 454 patients was carried out. The following parameters were registered: sex and age of the patient, indication for the angiography, cerebral CT diagnosis, laboratory data, type of anesthesia, type of angiographic procedure, level of training of the angiographer, number of participating angiographers, type of catheters, number of vessels catheterized, number of exposures, use of compression series, total amount of contrast media, diagnosis of the angiogram, complications and duration of complications.

Results: The frequency of all neurologic complications was 2.3%, the frequency of persistent neurologic deficits was 0.4%. Non-neurologic complications were observed in 14.7% of the examinations. Of all the parameters studied, the only factor that significantly increased neurologic risk was a normal angiogram, a finding we are inclined to ascribe to chance. Performance of a compression series showed a trend towards increasing the neurologic risk.

Conclusion: This study showed a complication rate of persistent neurologic deficits of 0.4% which is in accordance with other recent reports. A compression series should not be performed routinely, but only on special indication. This study confirms the low risk of cerebral angiography when performed in a neuroradiological department using the DSA technique and non-ionic contrast media.
MR Imaging After Sports-Induced Hip Dislocations: Report of three cases
Authors: Stiris M.G.
Published: July 2004

The MR findings in 3 patients who had sustained a posterior dislocation of the hip during sports activities are reported.
Ultrasound Demonstration of Mammographically Detected Microcalcifications
Authors: Gufler H. , Buitrago-Téllez C. Hernando , Madjar H. , Allmann K.-H. , Uhl M. , Rohr-Reyes A.
Published: July 2004

Purpose: To evaluate the capabilities of breast ultrasound (US) for identifying microcalcifications in benign breast changes, in situ carcinomas, and small non-palpable invasive carcinomas.

Material and Methods: Forty-six consecutive patients with 49 clustered microcalcifications detected by mammography were included in this prospective study. Patients with palpable breast lesions were excluded. Breast US was performed with knowledge of mammographic findings for presence and visibility of microcalcifications, and for parenchymal structure abnormalities. Mammographic and US findings were compared with histology.

Results: Nine ductal in situ carcinomas, 2 lobular in situ carcinomas, 11 invasive carcinomas and 27 benign lesions were confirmed by histology. For all lesions, US achieved a sensitivity of 75% in the detection of microcalcifications. The detection rate for microcalcification in invasive and in situ carcinomas was 100%. In 11 cases, no microcalcifications were visible on US; they all proved to be benign on histology.

Conclusion: Microcalcifications in malignant lesions are reliably recognized by US. They are, however, difficult to detect in fibrocystic breast changes.
The Potential Influence of Fine-Needle Aspiration on MR Imaging of the Breast
Authors: Wiberg M. Kristoffersen , Boné B. , Aspelin P.
Published: July 2004

Purpose: The aim of this study was to determine whether fine-needle aspiration biopsy (FNAB) of breast lesions causes structural changes or changes in contrast enhancement, that could impair the evaluation of these lesions at MR investigation of the breast.

Material and Methods: Fifteen patients with 17 lesions were examined with MR imaging of the breast both before and after the FNAB with a mean interval of 7.1 days. At both examinations, signal intensities were measured pre- and post-contrast enhancement in the lesions as well as in surrounding breast parenchyma and muscle. Imaging with contrast enhancement was performed semi-dynamically with two images obtained in rapid sequence (acquisition time 6.23 min) immediately after bolus injection of gadopentetate dimeglumine, 0.1 mmol/kg b.w., and the contrast enhancement in both images was calculated.

Results: The diagnostic value of MR images was unimpaired by FNAB, and no statistical difference between contrast enhancement in corresponding images obtained before and after FNAB was found, either within the lesions or in the breast parenchyma or muscle.

Conclusion: FNAB of the breast can be performed without impairing the diagnostic outcome of MR investigation.
Intracystic papillary carcinoma in the male breast: A case report
Authors: Anan H. , Okazaki M. , Fujimitsu R. , Hamada Y. , Sakata N. , Nanbu M.
Published: July 2004

Male breast cancer is a rare disease with an incidence between 0.5% and 2.4% of that in women. We report a case of intracystic papillary carcinoma of the breast in a 75-year-old Japanese man. The macroscopic features of the carcinoma could be accurately demonstrated by pneumocystography and ultrasonography preoperatively.
High-resolution CT in renal transplant patients with suspected pulmonary infections
Authors: Gulati M. , Kaur R. , Jha V. , Venkataramu N.K. , Gupta D. , Suri S.
Published: July 2004

Objective: This prospective study was carried out to assess the usefulness of high-resolution CT (HRCT) of the chest in immunocompromised renal transplant patients with suspected pulmonary infections.

Material and Methods: Twenty-one consecutive renal transplant patients with clinically suspected pulmonary infections underwent chest radiography, HRCT and other tests including bronchoalveolar lavage (BAL). HRCT was performed using a high spatial frequency algorithm with 2-mm-thick sections at 10-mm intervals from apices to domes of the diaphragm. The findings on chest radiography and HRCT were interpreted by two thoracic radiologists and the usefulness of HRCT was evaluated. The images were interpreted independently by two radiologists, who were blinded to the findings of other imaging modalities and the final diagnosis. Any differences regarding the imaging findings were resolved through consensus.

Results: Final diagnosis was obtained in 17 patients, and no cause for symptomatology was established in 4 patients. The spectrum of infections included pulmonary tuberculosis (TB) in 11 patients, cytomegalovirus pneumonia (CMV) in 2 patients, cryptococcal and streptococcal pneumonia, pulmonary aspergillosis and esophageal candidiasis in 1 patient each. Compared to chest radiography, HRCT revealed additional findings in 11 patients. HRCT findings were suggestive of underlying infection in 11 patients. The final diagnosis coincided with HRCT diagnosis in all but 1 patient. HRCT findings were non-specific in 3 patients and normal in 7. The findings were concordant in 19 cases. The results were not in agreement in only 2 cases.

Conclusion: HRCT can provide useful information and suggest the diagnosis in a significant proportion of renal transplant patients with pulmonary infection.
CT lung densitometry in assessing intralobular air content: An experimental and clinical study
Authors: Perhomaa M. , Jauhiainen J. , Lähde S. , Ojala A. , Suramo I.
Published: July 2004

Purpose: To introduce a parameter called “intralobular air content percentage” to replace the CT number of the lung and to establish a proper protocol for its assessment.

Material and Methods: We calibrated the HU (Hounsfield unit) scale for low densities with foam and evaluated the influence of certain acquisition and reconstruction parameters on the accuracy of CT densitometry of the lungs. The reproducibility of the results obtained in human experiments and the intralobular air content percentage of normal and diseased lung tissue were assessed.

Results: Air content could be reliably derived from the calibrated CT number of an area within a secondary lobulus. The mean intralobular air content of normal lungs varied from 77.8% to 88.0% in full inspiration. Helical or axial recording with a 10-mm slice thickness, a standard or soft algorithm and high tube currents and voltage settings, was suitable for the measurements.

Conclusion: Before absolute lung density measurements (as a HU number or an air content percentage), the CT equipment has to be calibrated for low densities. The intralobular air content percentages of cooperative patients were reliably reproducible.
Optimal tube current for lung cancer screening with low-dose spiral CT
Authors: Oguchi K. , Sone S. , Kiyono K. , Takashima S. , Maruyama Y. , Hasegawa M. , Feng L.
Published: July 2004

Purpose: To determine the optimal tube current for spiral CT for lung cancer screening.

Material and Methods: Low-dose spiral CT images from 20 subjects were obtained with 50 mA, 25 mA, 10 mA and 5 mA tube currents. The accuracy in detecting 21 nodules measuring 3 to 14 mm in diameter was tested using receiver operating characteristics (ROC) to determine the diagnostic accuracy and statistical significance.

Results: Compared with 50 mA, 25 mA showed no statistical difference. A significant difference was seen between 50 mA and 5 mA images and between 25 mA and 10 mA images, in the detection of lung parenchymal nodular lesions.

Conclusion: Approximately 25 mA is the optimal tube current for the detection of pulmonary nodules as it allows a reduction of the radiation dose without sacrificing diagnostic accuracy.
Detection and characterisation of renal lesions by multiphasic helical CT
Authors: Dahlman P. , Semenas E. , Brekkan E. , Bergman A. , Magnusson A.
Published: July 2004

Purpose: The fast helical CT technique allows examination of the kidneys during different phases of contrast medium enhancement. However, every additional phase increases the radiation dosage to the patients. We investigated the detection rate and characterisation of renal lesions during different phases and evaluated them separately, and considered the possibility of excluding phases without loss of important information.

Material and Methods: Sixty patients who underwent contrast-enhanced multiphasic renal helical CT examination were included. Every CT phase was evaluated separately. The number of lesions and the characteristics of the lesions were noted and all lesions were viewed together.

Results: A total of 153 cysts and 17 solid lesions were detected. The largest and an equal number of cysts (142/143) was detected in the nephrographic and excretory phases. However, the nephrographic phase detected more cortical cysts and the excretory phase detected more sinus cysts. All solid lesions were detected in all phases. Renal parenchymal tumours were best characterised in the cortical phase and angiomyolipomas in the native phase.

Conclusion: The cortical phase was best for characterisation of renal parenchymal tumours. The nephrographic and excretory phases were best in detecting and characterising renal cysts. The nephrographic phase was the phase giving the least diagnostic information.
Cranial epidural tuberculoma: A case report
Authors: Jacques C. , Boukobza M. , Polivka M. , Ferrario A. , George B. , Merland J.J.
Published: July 2004

A 33-year-old patient with cranial epidural tuberculoma without history of tuberculosis is described. CT and MR imaging showed a lesion located on both sides of a right frontotemporal bone destruction with epidural extent. Except for a small necrotic core, the lesion enhanced intensely after contrast medium administration. Osteitis and subgaleal abscess were associated. The displaced dura mater delineated the epidural tuberculoma. Diagnosis was verified by histology and identification of Mycobacterium tuberculosis. After removal of the tuberculoma and combination therapy, there was a complete regression of abnormalities. Differential diagnoses are dural tuberculoma, focal tuberculous pachymeningitis and tuberculous epidural empyema.