bluuebunny/crossref_metadata_2025 huggingface dataset:
Elastic full waveform inversion of multicomponent ocean-bottom cable seismic data: Application to Alba Field, U. K. North Sea
Authors: Sears Timothy J. , Barton Penny J. , Singh Satish C.
Published: December 2010

Elastic full waveform inversion of multichannel seismic data represents a data-driven form of analysis leading to direct quantification of the subsurface elastic parameters in the depth domain. Previous studies have focused on marine streamer data using acoustic or elastic inversion schemes for the inversion of P-wave data. In this paper, P- and S-wave velocities are inverted for using wide-angle multicomponent ocean-bottom cable (OBC) seismic data. Inversion is undertaken using a two-dimensional elastic algorithm operating in the time domain, which allows accurate modeling and inversion of the full elastic wavefield, including P- and mode-converted PS-waves and their respective amplitude variation with offset (AVO) responses. Results are presented from the application of this technique to an OBC seismic data set from the Alba Field, North Sea. After building an initial velocity model and extracting a seismic wavelet, the data are inverted instages. In the first stage, the intermediate wavelength P-wave velocity structure is recovered from the wide-angle data and then the short-scale detail from near-offset data using P-wave data on the [Formula: see text] (vertical geophone) component. In the second stage, intermediate wavelengths of S-wave velocity are inverted for, which exploits the information captured in the P-wave’s elastic AVO response. In the third stage, the earlier models are built on to invert mode-converted PS-wave events on the [Formula: see text] (horizontal geophone) component for S-wave velocity, targeting first shallow and then deeper structure. Inversion of [Formula: see text] alone has been able to delineate the Alba Field in P- and S-wave velocity, with the main field and outlier sands visible on the 2D results. Inversion of PS-wave data has demonstrated the potential of using converted waves to resolve shorter wavelength detail. Even at the low frequencies [Formula: see text] inverted here, improved spatial resolution was obtained by inverting S-wave data compared with P-wave data inversion results.
Eigenvector analysis of gravity gradient tensor to locate geologic bodies
Authors: Beiki Majid , Pedersen Laust B.
Published: December 2010

We have developed a new method to locate geologic bodies using the gravity gradient tensor. The eigenvectors of the symmetric gravity gradient tensor can be used to estimate the position of the source body as well as its strike direction. For a given measurement point, the eigenvector corresponding to the maximum eigenvalue points approximately toward the center of mass of the causative body. For a collection of measurement points, a robust least-squares procedure is used to estimate the source point as the point that has the smallest sum of square distances to the lines defined by the eigenvectors and the measurement positions. It’s assumed that the maximum of the first vertical derivative of the vertical component of gravity vector [Formula: see text] is approximately located above the center of mass. Observation points enclosed in a square window centered at the maximum of [Formula: see text] are used to estimate the source location. By increasing the size of the window, the number of eigenvectors used in the robust least squares and subsequently the number of solutions increase. As a criterion for selecting the best solution from a set of previously computed solutions, we chose that solution having the minimum relative error (less than a given threshold) of its depth estimate. The strike direction of the source can be estimated from the direction of the eigenvectors corresponding to the smallest eigenvalue for quasi 2D structures. To study the effect of additive random noise and interfering sources, the method was tested on synthetic data sets, and it appears that our method is robust to random noise in the different measurement channels. The method was also tested on gravity gradient tensor data from the Vredefort impact structure, South Africa. The results show a very good agreement with the available geologic information.
Acoustic and elastic numerical wave simulations by recursive spatial derivative operators
Authors: Kosloff Dan , Pestana Reynam C. , Tal-Ezer Hillel
Published: December 2010

A new scheme for the calculation of spatial derivatives has been developed. The technique is based on recursive derivative operators that are generated by an [Formula: see text] fit in the spectral domain. The use of recursive operators enables us to extend acoustic and elastic wave simulations to shorter wavelengths. The method is applied to the numerical solution of the 2D acoustic wave equation and to the solution of the equations of 2D dynamic elasticity in an isotropic medium. An example of reverse-time migration of a synthetic data set shows that the numerical dispersion can be significantly reduced with respect to schemes that are based on finite differences. The method is tested for the solutions of the equations of dynamic elasticity by comparing numerical and analytic solutions to Lamb’s problem.
An interferometric theory of source-receiver scattering and imaging
Authors: Halliday David , Curtis Andrew
Published: December 2010

It is known that there is a link between the theory of seismic interferometry and theories of seismic imaging and inversion. However, although this has been discussed in several studies, there are few where any explicit links have been derived. We use reciprocity theorems for scattering media to derive a new form of seismic interferometry that describes the scattered wavefield between a source and a receiver in an acoustic medium, using both sources and receivers on two enclosing boundaries. This form of seismic interferometry is equivalent to a generalized imaging condition (IC) that combines the full wavefield inside any finite-sized subregion of the medium of interest. By using the Born (single-scattering) approximation, this generalized IC reduces to the method of imaging by double-focusing originally derived by Michael Oristaglio in 1989. Thus an explicit link is made between seismic interferometry, new generalized full-wavefield ICs, and existing single-scattering imaging methods.
Laboratory measurements of porosity, permeability, resistivity, and velocity on Fontainebleau sandstones
Authors: Gomez Carmen T. , Dvorkin Jack , Vanorio Tiziana
Published: December 2010

The relations among the resistivity, elastic-wave velocity, porosity, and permeability in Fontainebleau sandstone samples from the Ile de France region, around Paris, France were experimentally revisited. These samples followed a permeability-porosity relation given by Kozeny-Carman’s equation. For the resistivity measurements, the samples were partially saturated with brine. Archie’s equation was used to estimate resistivity at 100% water saturation, assuming a saturation exponent, [Formula: see text]. Using self-consistent (SC) approximations modeling with grain aspect ratio 1, and pore aspect ratio between 0.02 and 0.10, the experimental data fall into this theoretical range. The SC curve with the pore aspect ratio 0.05 appears to be close to the values measured in the entire porosity range. The elastic-wave velocity was mea-sured on these dry samples for confining pressure between 0 and [Formula: see text]. A loading and unloading cycle was used and did not produce any significant hysteresis in the velocity-pressure behavior. For the velocity data, using the SC model with a grain aspect ratio 1 and pore aspect ratios 0.2, 0.1, and 0.05 fit the data at [Formula: see text]; pore aspect ratios ranging between 0.1, 0.05, and 0.02 were a better fit for the data at [Formula: see text]. Both velocity and resistivity in clean sandstones can be modeled using the SC approximation. In addition, a linear fit was found between the P-wave velocity and the decimal logarithm of the normalized resistivity, with deviations that correlate with differences in permeability. Combining the stiff sand model and Archie for cementation exponents between 1.6 and 2.1, resistivity was modeled as a function of P-wave velocity for these clean sandstones.
Deconvolution imaging conditions and cross-talk suppression
Authors: Poole Travis L. , Curtis Andrew , Robertsson Johan O. , van Manen Dirk-Jan
Published: December 2010

Deconvolution imaging conditions offer improved resolution over standard, crosscorrelation-based imaging conditions. Additionally, these imaging conditions produce a result more directly related to a reflection coefficient than do crosscorrelation-based imaging conditions. In simple analytical cases, deconvolution imaging conditions also offer the possibility of eliminating crosstalk (i.e., energy in the image due to reflected energy arriving at a location at the same time as incident energy that did not cause the reflected energy) when the full up- and down-going wavefields are used. This means that in such cases, surface-related multiples can be eliminated from the image, or that multiple shots could potentially be fired simultaneously without degrading the image. However, this cross-talk-suppression property is not observed in most situations. We show that this is due to a number of issues: the correct order of deconvolution must be used, stabilization causes imperfect deconvolution, finite apertures lead to some of the signal being lost, and an assumption of horizontal stratification is often not being met. Further, imperfect knowledge of the incident and reflected field due to such factors as anisotropy, poorly estimated velocity fields, and measurement noise can also lead to imperfect deconvolution. Thus, deconvolution imaging conditions should not be counted on to completely eliminate crosstalk from images.
Wavelet distortion correction due to domain conversion
Authors: Bansal Rishi , Matheney Mike
Published: December 2010

Converted-wave (PS) data, when converted to PP time, develop time- and location-varying compression of the seismic wavelet due to a variable subsurface [Formula: see text] [Formula: see text]. The time-dependent compression distorts the wavelet in a seismic trace. The lack of a consistent seismic wavelet in a domain-converted PS volume can eventually lead to an erroneous joint PP/PS inversion result. Depth-converted seismic data also have wavelet distortion due to velocity-dependent wavelet stretch. A high value of seismic velocity produces more stretch in a seismic wavelet than a low value. Variable wavelet stretch renders the depth data unsuitable for attribute analysis. A filtering scheme is proposed that corrects for distortion in seismic wavelets due to domain conversions (PS to PP time and time-to-depth) of seismic data in an amplitude-preserving manner. The method uses a Fourier scaling theorem to predict the seismic wavelet in the converted domain and calculates a shaping filter for each time/depth sample that corrects for the distortion in the wavelet. The filter is applied to the domain-converted data using the method of nonstationary filtering. We provide analytical expressions for the squeeze factor [Formula: see text] that is used to predict the wavelet in the converted domain. The squeeze factor [Formula: see text] for PS to PP time conversion is a function of the subsurface [Formula: see text] whereas for PP time-to-depth conversion [Formula: see text] is dependent on subsurface P-wave velocity. After filtering, the squeezed wavelets in domain-converted PS data appear to have resulted from a constant subsurface [Formula: see text], which we denote as [Formula: see text]. Similarly, the filtered depth-converted data appear to have resulted from a constant subsurface P-wave velocity [Formula: see text].
Nonlinear extended images via image-domain interferometry
Authors: Vasconcelos Ivan , Sava Paul , Douma Huub
Published: December 2010

Wave-equation, finite-frequency imaging and inversion still face many challenges in addressing the inversion of highly complex velocity models as well as in dealing with nonlinear imaging (e.g., migration of multiples, amplitude-preserving migration). Extended images (EIs) are particularly important for designing image-domain objective functions aimed at addressing standing issues in seismic imaging, such as two-way migration velocity inversion or imaging/inversion using multiples. General one- and two-way representations for scattered wavefields can describe and analyze EIs obtained in wave-equation imaging. We have developed a formulation that explicitly connects the wavefield correlations done in seismic imaging with the theory and practice of seismic interferometry. In light of this connection, we define EIs as locally scattered fields reconstructed by model-dependent, image-domain interferometry. Because they incorporate the same one- and two-way scattering representations usedfor seismic interferometry, the reciprocity-based EIs can in principle account for all possible nonlinear effects in the imaging process, i.e., migration of multiples and amplitude corrections. In this case, the practice of two-way imaging departs considerably from the one-way approach. We have studied the differences between these approaches in the context of nonlinear imaging, analyzing the differences in the wavefield extrapolation steps as well as in imposing the extended imaging conditions. When invoking single-scattering effects and ignoring amplitude effects in generating EIs, the one- and two-way approaches become essentially the same as those used in today’s migration practice, with the straightforward addition of space and time lags in the correlation-based imaging condition. Our formal description of the EIs and the insight that they are scattered fields in the image domain may be useful in further development of imaging and inversion methods in the context of linear, migration-based velocity inversion or in more sophisticated image-domain nonlinear inverse scattering approaches.
Application of the magnetic resonance sounding method to the investigation of aquifers in the presence of magnetic materials
Authors: Legchenko Anatoly , Vouillamoz Jean-Michel , Roy Jean
Published: December 2010

It has been previously reported that the magnetic resonance sounding (MRS) method does not produce reliable data in areas where magnetic rocks perturb the geomagnetic field. The applicability of the MRS can be extended by using the spin echo (SE) measuring technique instead of the commonly used measuring scheme based on recordings of the free induction decay (FID) signal. Modifications to the MRS method are presented for measuring and interpreting SE signals. Field results obtained in Cyprus (1999), Canada (2008), and India (2008) reveal that in test sites MRS measurements in the SE mode make it possible to apply the MRS method where the subsurface is composed of sand and gravel that contain magnetite or basalt and in aquifers composed of nonmagnetic sand overlying a magnetic basement. Con-sidering the widespread occurrence of magnetic rocks, this development increases the area where MRS can be applied. However, experience shows that it is more time consuming to measure the SE and more complicated to interpret the field data than it is to work with FID measurements. Numerical results show that the MRS method in the SE mode is less efficient than the FID technique because of the smaller amplitude and wider band of the SE signal. Due to instrumental limitations and unknown distribution of the magnetic fields within the investigated volume, accuracy of the presented MRS-SE approach is site dependent. In a general case, MRS-SE in its current implementation is not able to provide robust estimates of the initial amplitude, which renders MRS estimate of the water content qualitative. For accurate estimate of the water content, more sophisticated approaches need to be developed.
Geostatistical inference using crosshole ground-penetrating radar
Authors: Looms Majken C. , Hansen Thomas M. , Cordua Knud S. , Nielsen Lars , Jensen Karsten H. , Binley Andrew
Published: December 2010

High-resolution tomographic images obtained from crosshole geophysical measurements have the potential to provide valuable information about the geostatistical properties of unsaturated-zone hydrologic-state variables such as moisture content. Under drained or quasi-steady-state conditions, the moisture content will reflect the variation of the physical properties of the subsurface, which determine the flow patterns in the unsaturated zone. Deterministic least-squares inversion of crosshole ground-penetrating-radar (GPR) traveltimes result in smooth, minimum-variance estimates of the subsurface radar wave velocity structure, which may diminish the utility of these images for geostatistical inference. We have used a linearized stochastic inversion technique to infer the geostatistical properties of the subsurface radar wave velocity distribution using crosshole GPR traveltimes directly. Expanding on a previous study, we have determined that it is possible to obtain estimates of global variance andmean velocity values of the subsurface as well as the correlation lengths describing the subsurface velocity structures. Accurate estimation of the global variance is crucial if stochastic realizations of the subsurface are used to evaluate the uncertainty of the inversion estimate. We have explored the full potential of the geostatistical inference method using several synthetic models of varying correlation structures and have tested the influence of different assumptions concerning the choice of covariance function and data noise level. In addition, we have tested the methodology on traveltime data collected at a field site in Denmark. There, inferred correlation structures indicate that structural differences exist between two areas located approximately [Formula: see text] apart, an observation confirmed by a GPR reflection profile. Furthermore, the inferred values of the subsurface global variance and the mean velocity have been corroborated with moisture-content measurements, obtained gravimetrically from samples collected at the field site.
Assessment of Delaware and Groningen effects on dual-laterolog measurements with a self-adaptive hp finite-element method
Authors: Nam Myung Jin , Pardo David , Torres-Verdín Carlos
Published: December 2010

We describe numerical simulations of anomalous dual-laterolog (DLL) borehole measurements, including Delaware and Groningen effects. Both effects give rise to abnormally high readings of DLL measurements under extreme logging conditions. Specifically, a low resistive bed below a highly resistive layer causes electrical currents to concentrate within the borehole, which generates a negative potential at the reference electrode and, consequently, an abnormally high reading in DLL measurements. These effects are exacerbated by the presence of casing and/or at nonzero frequencies. Simulations are performed with a 2D goal-oriented, high-order, self-adaptive [Formula: see text] finite-element method together with an embedded postprocessing method. Results indicate that the presence of electrodes [Formula: see text] and [Formula: see text] is critical for proper simulation of Delaware effects on DLL measurements. Delaware effects on DLL logs decrease as the current return electrode is moved farther away from either the logging point or the borehole. The frequency of operation also affects deep laterolog measurements, generating the so-called Groningen effect.
Mapping formation radial shear-wave velocity variation by a constrained inversion of borehole flexural-wave dispersion data
Authors: Tang Xiao-Ming , Patterson Douglas J.
Published: December 2010

We have developed a novel constrained inversion method for estimating a radial shear-wave velocity profile away from the wellbore using dipole acoustic logging data and have analyzed the effect of the radial velocity changes on dipole-flexural-wave dispersion characteristics. The inversion of the dispersion data to estimate the radial changes is inherently a nonunique problem because changing the degree of variation or the radial size of the variation zone can produce similar wave-dispersion characteristics. Nonuniqueness can be solved by developing a constrained inversion method. This is done by constraining the high-frequency portion of the model dispersion curve with another curve calculated using the near-borehole velocity. The constraint condition is based on the physical principle that a high-frequency dipole wave has a shallow penetration depth and is therefore sensitive to the near-borehole shear-wave velocity. We have validated the result of the constrained inversion with synthetic data testing. Combining the new inversion method with four-component crossed-dipole anisotropy processing obtains shear radial profiles in fast and slow shear polarization directions. In a sandstone formation, the fast and slow shear-wave profiles show substantial differences caused by the near-borehole stress field, demonstrating the ability of the technique to obtain radial and azimuthal geomechanical property changes near the wellbore.
On the connection between artifact filtering in reverse-time migration and adjoint tomography
Authors: Douma Huub , Yingst David , Vasconcelos Ivan , Tromp Jeroen
Published: December 2010

Finite-frequency sensitivity kernels in seismic tomography define the volumes inside the earth that influence seismic waves as they traverse through it. It has recently been numerically observed that an image obtained using the impedance kernel is much less contaminated by low-frequency artifacts due to the presence of sharp wave-speed contrasts in the background model, than is an image obtained using reverse-time migration. In practical reverse-time migration, these artifacts are routinely heuristically dampened by Laplacian filtering of the image. Here we show analytically that, for an isotropic acoustic medium with constant density, away from sources and receivers and in a smooth background medium, Laplacian image filtering is identical to imaging with the impedance kernel. Therefore, when imaging is pushed toward using background models with sharp wave-speed contrasts, the impedance kernel image is less prone to develop low-frequency artifacts than is the reverse-time migration image, due to the implicit action of the Laplacian that amplifies the higher-frequency reflectors relative to the low-frequency artifacts. Thus, the heuristic Laplacian filtering commonly used in practical reverse-time migration is fundamentally rooted in adjoint tomography and, in particular, closely connected to the impedance kernel.
Intellectual Property
Authors: Walker David A.
Published: December 2010

The Intellectual Property department in each issue of Geophysics provides U.S. patent abstracts, published patent abstracts of U.S. patent applications, and published abstracts filed under the Patent Cooperation Treaty (PCT).
Synthesis and Photoisomerization of Highly Fluorescent Stilbene Ionic Liquids
Authors: Tamura Hiroyasu , Shinohara Yoshihiro , Arai Tatsuo
Published: December 2010

Photoresponsive stilbenes with imidazolium cation directly attached to the para-position of the phenyl ring were prepared and their properties were examined. Although the cis isomer was liquid at room temperature and practically gave no fluorescence, the trans isomer was solid and gave fluorescence emission with quantum yield as high as ca. 0.2. Furthermore photoisomerization from pure cis isomer in the liquid state to trans isomer in the solid state was observed.
Ultrasensitive and Highly Selective Detection of Testosterone Using a Surface Plasmon Resonance Sensor Combined with Molecularly Imprinted Films
Authors: Wei Qingquan , Wei Tianxin , Wu Xiaoguang
Published: December 2010

An ultrasensitive and highly selective testosterone detection method by surface plasmon resonance (SPR) combined with molecularly imprinted films (MIFs) was developed. The coupling angle shifts were highly selective to testosterone and showed a linear relationship to the logarithmic concentrations (from 10−15 to 10−10 mol L−1) of the testosterone in the acetonitrile. The selectivity of the thin testosterone-imprinted films was examined by 10−4 mol L−1 progesterone acetonitrile solution, no observable binding was detected.
Stable Transport of Gas-born Ag Nanoparticles into Liquid Phase Mediated by Poly(vinylpyrrolidone) Molecules
Authors: Hashimoto Naomi , Nishida Naoki , Murayama Haruno , Tanaka Hideki
Published: December 2010

We demonstrate that gas-born nanoparticles can be transported into solution successfully. Our results show that Ag nanoparticles produced in gas phase are introduced into poly(vinylpyrrolidone) solution without structural changes such as nanoparticle aggregation. It is also shown that Ag nanoparticles in solution show surface plasmon resonance, suggesting that the optical properties of nanoparticles are not impaired by the transport from gas to liquid.
Why Have Economic Reforms in Mexico Not Generated Growth?
Authors: Kehoe Timothy J , Ruhl Kim J
Published: December 2010

Following its opening to trade and foreign investment in the mid-1980s, Mexico's economic growth has been modest at best, particularly in comparison with that of China. Comparing these countries and reviewing the literature, we conclude that the relation between openness and growth is not a simple one. Using standard trade theory, we find that Mexico has gained from trade, and by some measures, more so than China. We sketch out a theory in which developing countries can grow faster than the United States by reforming. As a country becomes richer, this sort of catch-up becomes more difficult. Absent continuing reforms, Chinese growth is likely to slow down sharply, perhaps leaving China at a level less than Mexico's real GDP per working-age person. (JEL E23, E65, F14, O10, O20, O47)
Designing Climate Mitigation Policy
Authors: Aldy Joseph E , Krupnick Alan J , Newell Richard G , Parry Ian W. H , Pizer William A
Published: December 2010

This paper provides (for the nonspecialist) a highly streamlined discussion of the main issues, and controversies, in the design of climate mitigation policy. The first part of the paper discusses how much action to reduce greenhouse gas emissions at the global level is efficient under both the cost-effectiveness and welfare-maximizing paradigms. We then discuss various issues in the implementation of domestic emissions control policy, instrument choice, and incentives for technological innovation. Finally, we discuss alternative policy architectures at the international level. (JEL Q54, Q58)
Quality Disclosure and Certification: Theory and Practice
Authors: Dranove David , Jin Ginger Zhe
Published: December 2010

This essay reviews the theoretical and empirical literature on quality disclosure and certification. After comparing quality disclosure with other quality assurance mechanisms and describing a brief history of quality disclosure, we address two sets of theoretical issues. First, why don't sellers voluntarily disclose through a process of “unraveling” and, given the lack of unraveling, is it desirable to mandate seller disclosure? Second, when we rely on certifiers to act as the intermediary of quality disclosure, do certifiers necessarily report unbiased and accurate information? We further review empirical evidence on these issues, with a particular focus on healthcare, education, and finance. The empirical review covers quality measurement, the effect of third-party disclosure on consumer choice and seller behavior, as well as the economics of certifiers. (JEL D18, K32, L15, M31)
Why Isn't Mexico Rich?
Authors: Hanson Gordon H
Published: December 2010

Over the last three decades, Mexico has aggressively reformed its economy, opening to foreign trade and investment, achieving fiscal discipline, and privatizing state owned enterprises. Despite these efforts, the country's economic growth has been lackluster, trailing that of many other developing nations. In this paper, I review arguments for why Mexico hasn't sustained higher rates of economic growth. The most prominent suggest that some combination of poorly functioning credit markets, distortions in the supply of nontraded inputs, and perverse incentives for informality creates a drag on productivity growth. These are factors internal to Mexico. One possible external factor is that the country has the bad luck of exporting goods that China sells, rather than goods that China buys. I assess evidence from recent literature on these arguments and suggest directions for future research. (JEL E23, E65, F14, O10, O20, O47)
Pre-operative patient education reduces length of stay after knee joint arthroplasty
Authors: Jones Samantha , Alnaib Mustafa , Kokkinakis Michail , Wilkinson Michael , St Clair Gibson Alan , Kader Deiary
Published: December 2010

INTRODUCTION

The aim of this study was to evaluate the impact of a pre-operative education programme on length of hospital stay after surgery for primary and revision knee arthroplasty patients. The programme was introduced at our hospital in October 2006 to encourage patients to play an active role in their recovery process after surgery.

PATIENTS AND METHODS

A multidisciplinary team educated knee arthroplasty patients about their care pathway, knee surgery, pain management, expected discharge goals, in-patient and out-patient arthroplasty rehabilitation. Prospective data were collected from 472 consecutive patients who underwent (primary or revision) knee arthroplasty in the period between January 2006 and November 2007. Patients were separated into two groups, one that received conventional pre-operative treatment (n = 150; Conventional group) and another that received the pre-operative education (n = 322; Education group). Length of hospital stay was compare using the Mann Whitney U test. In-patient complications, hospital re-admissions within 24 h and 3 months of hospital discharge were compared using the chi-squared test.

RESULTS

The mean length of stay was significantly reduced from 7 days in the Conventional group to 5 days in the Education group (P < 0.01). In addition, 20% more patients were discharged early (within 1–4 days) in the Education group compared to the Conventional group (P < 0.01). There was no difference in the percentage of in-patient complications and re-admissions in 24 h (P = 1.00) and 3 months of discharge (P = 0.92) between the two groups.

CONCLUSIONS

The results suggest that pre-operative education is a safe and effective method of reducing length of stay for knee arthroplasty patients.
Evolution in the management of Hirschsprung’s disease in the UK and Ireland: a national survey of practice revisited
Authors: Bradnock TJ , Walker GM
Published: December 2010

INTRODUCTION

The management of Hirschsprung’s disease continues to evolve. This questionnaire survey aimed to determine current surgical management strategies for Hirschsprung’s disease in Britain.

SUBJECTS AND METHODS

The survey was sent electronically to all British paediatric surgeons. Initial questions explored individual experience and regional service provision. Additional questions, reserved for surgeons who perform definitive Hirschsprung’s disease surgery, addressed specific clinical scenarios.

RESULTS

Surveys were sent to 142 surgeons yielding 85 responses. After exclusions, 64 surveys from 21 centres were analysed. Forty-seven respondents worked in centres with designated ‘Hirschsprung’s disease surgeons’. Forty respondents perform definitive Hirschsprung’s disease surgery. In a well neonate with left-sided Hirschsprung’s disease, 34 of 40 surgeons favour primary pull-through following bowel decompression with rectal washouts; 35 of 40 surgeons aim to perform definitive surgery at less than 3 months of age, with 17 favouring laparoscopic-assisted Soave–Boley and 15 favouring an open Duhamel pull-through. Of the 40 surgeons, 36 use a staged approach to right-sided/total colonic Hirschsprung’s disease with 23 favouring a Duhamel or Long Duhamel pull-through.

CONCLUSIONS

The primary pull-through, using an open Duhamel or laparoscopic-assisted Soave–Boley technique, during the first 3 months of life, has become the operative strategy of choice in rectosigmoid Hirschsprung’s disease in Britain. Marked variation in practice remains for right-sided Hirschsprung’s disease.
Recurrent laryngeal nerve and voice preservation: routine identification and appropriate assessment – two important steps in thyroid surgery
Authors: Mohil Ravindra Singh , Desai Pragnesh , Narayan Nitisha , Sahoo Maheswar , Bhatnagar Dinesh , Venkatachalam VP
Published: December 2010

INTRODUCTION

The aims of this study were to assess and compare vocal cord functions before and after thyroid surgery after intra-operative identification of recurrent laryngeal nerve.

PATIENTS AND METHODS

Recurrent laryngeal nerve (RLN) is seen intra-operatively in all cases undergoing thyroid surgeries. Vocal cord functions including any voice change were evaluated by indirect laryngoscopy (I/L) and direct laryngoscopy (D/L) before and after surgery.

RESULTS

Prospective study on 100 patients over 18 months with a total of 146 nerves at risk (NAR). Majority were women (n = 86) with mean age of 37.48 years (range, 13–60 years). RLN was seen in all patients and 19 patients complained of some change in quality of their voice after surgery. Evaluation by I/L and D/L at 6 weeks showed recurrent laryngeal nerve palsy (RLNP) in nine (47.36%) and five (26%) of these 19 patients respectively. Analysed according to total NAR, the incidence of voice change and temporary RLN palsy (I/L and D/L) at 6 weeks was still less at 13.01%, 6.16% and 3.42%, respectively. Voice change improved in all cases at 3 months with no RLNP palsy by I/L or D/L. All these 19 patients had undergone difficult or extensive surgery for malignancy, large gland, extratyhroidal spread or fibrosis.

CONCLUSIONS

Despite identification and preservation of RLN, patients can develop postoperative voice change and RLNP although all voice change cannot be attributed to damaged RLN. Proper assessment of vocal cord functions by I/L and D/L laryngoscopy is required to rule out injuries to these nerves. Risk of damage is higher in patients undergoing more difficult surgery.
Safety and application of laparoscopic gastrectomy for benign gastric disease and gastric cancer
Authors: Zia MK , Morris-Stiff G , Luhmann A , Jeffries R , Ehsan O , Hassn A
Published: December 2010

INTRODUCTION

Laparoscopic gastrectomy is rapidly expanding despite reservations by some surgeons regarding its safety and radicality. The aim of this study was to evaluate patients undergoing laparoscopic gastrectomy for both benign and malignant disease with particular emphasis on technical feasibility, safety, effectiveness and complications.

PATIENTS AND METHODS

Review of prospectively collected data of patients who underwent laparoscopic gastrectomy from May 2005 to September 2009 under the care of one consultant surgeon.

RESULTS

A total of 61 laparoscopic gastrectomies were performed (35 men and 26 women) with a median age of 68 years (range, 41–90 years). There were 39 distal gastrectomies (19 adenocarcinoma, 6 gastrointestinal stromal tumour [GIST], 4 benign gastric outlet obstruction, 4 high-grade dysplasia in gastric adenomas, 4 non-healing ulcers, 2 gastric antral vascular ectasia [GAVE]); 15 sub-total gastrectomies (13 adenocarcinomas, 2 GIST); and 7 total gastrectomies (5 adenocarcinomas, 1 GIST, 1 carcinoid). Median follow-up was for 48 months (range, 1–72 months). There was one death, two major and six minor complications. All patients with complications made a satisfactory recovery.

CONCLUSIONS

Laparoscopic gastrectomy is associated with a low mortality (1.75%) and major morbidity (3.50%). Although technically demanding, especially when a D2 lymphadenectomy is performed, our results have shown that tailored laparoscopic resection based on tumour characteristics with either D1 or D2 lymphadenectomy results in good surgical and oncological outcomes.
Factors affecting wound ooze in total knee replacement
Authors: Butt U , Ahmad R , Aspros D , Bannister GC
Published: December 2010

INTRODUCTION

Wound ooze is common following total knee arthroplasty (TKA) and persistent wound infection is a risk factor for infection, and increased length and cost of hospitalisation.

PATIENTS AND METHODS

We undertook a prospective study to assess the effect of tourniquet time, peri-articular local anaesthesia and surgical approach on wound oozing after TKA.

RESULTS

The medial parapatellar approach was used in 59 patients (77%) and subvastus in 18 patients (23%). Peri-articular local anaesthesia (0.25% Bupivacaine with 1:1,000,000 adrenalin) was used in 34 patients (44%). The mean tourniquet time was 83 min (range, 38–125 min). We found a significant association between cessation of oozing and peri-articular local anaesthesia (P = 0.003), length of the tourniquet time (P = 0.03) and the subvastus approach (P = 0.01).

CONCLUSIONS

Peri-articular local anaesthesia, the subvastus approach and shorter tourniquet time were all associated with less wound oozing after total knee arthroplasty.
Hip fractures: public perceptions
Authors: McBride TJ , Panrucker S , Clothier JC
Published: December 2010

INTRODUCTION

Hip fractures are common injuries in elderly patients presenting to the trauma surgeon. Mortality following such injuries approaches 10% at one month, rising to 30% at one year. Of those who survive, most experience a decrease in mobility and independence. The authors believe that the general public are not aware of these facts and in particular do not perceive hip fractures to be injuries of serious consequence.

SUBJECTS AND METHODS

This study aims to assess the perception of hip fractures amongst the general public. Subjects were recruited from a population attending a general orthopaedic clinic in a district general hospital during March 2008. All participants were asked to fill out a questionnaire relating to their perception of hip fracture epidemiology, aetiology, presentation, treatment and both physical and social outcomes.

RESULTS

A total of 142 people completed a questionnaire. Of those, 27 (19%) had been filled out by either hip fracture patients or their relatives. A significant majority of subjects underestimated both the hospital length of stay and mortality figures; however, most people did know that some form of surgery would be required.

CONCLUSIONS

This study underlines the need for detailed counselling of the patient and relatives following a hip fracture in order to create realistic expectations and to allow those involved to prepare for potential outcomes. Written patient information may also be useful to allow patients and relatives the opportunity to digest relevant information and to pose questions relating to what they have read.
The correlation between ultrasonography and histology in the search for gallstones
Authors: Ahmed M , Diggory R
Published: December 2010

INTRODUCTION

The majority of published data on the sensitivity and specificity of ultrasound in the diagnosis of gallbladder pathology was conducted over 30 years ago and, since the 1990s, ultrasound imaging has been the accepted gold standard. The quality and resolution of ultrasonography has improved significantly since then and we have, therefore, set out to assess whether the progression in technology has translated into improved diagnostic accuracy.

PATIENTS AND METHODS

In the period December 2005 to December 2008, a total of 2100 patients underwent laparoscopic cholecystectomy for symptoms related to gallbladder disease. All patients underwent ultrasound examination prior to their surgery and histopathological analysis of their gallbladder postoperatively. We undertook a retrospective analysis of these patients comparing their pre-operative ultrasound scan and their histopathology report for the presence or absence of gallstones. Ultrasound scans were performed by a combination of radiologists and ultrasonographers.

RESULTS

The study identified a sensitivity of 0.85 and a specificity of 1 for ultrasound in the identification of gallstones. We found a sensitivity of 0.84 and 0.83 for the radiologists and ultrasonographers, respectively.

CONCLUSIONS

This study suggests that, despite an evolution in the resolution of ultrasound imaging, there has not been a corresponding improvement in sensitivity. There is a false positive rate of 16% which remains unchanged since the early 1990s.
Minimising the risk of extensor pollicis longus rupture following volar plate fixation of distal radius fractures: a cadaveric study
Authors: Perry DC , Machin DMG , Casaletto JA , Brown DJ
Published: December 2010

INTRODUCTION

Rupture of extensor pollicis longus (EPL) tendon is a recognised complication following volar plate fixation of distal radius fractures, usually from attrition caused by prominent screws. We sought to identify the screw holes in some of the most commonly used plates which may precipitate tendon injury.

SUBJECTS AND METHODS

Three fixed-angle volar locking plates were sequentially positioned into 18 cadaveric arms. A wire was passed through each of the holes in the plates using a locking guide and the dorsal relationships noted.

RESULTS

Each plate had specific ‘high-risk’ holes which directed the wire towards the EPL groove. The central screw holes appeared mostly implicated in EPL injury.

CONCLUSIONS

Awareness of ‘high-risk’ holes and appropriate minor alterations in surgical technique may consequently decrease the incidence of EPL irritation and rupture.
Prospective audit of cross-sectional imaging and radiation exposure in general surgical patients
Authors: Cadwallader RA , Walsh SR , Burrows B , Chappell CL , Cousins C
Published: December 2010

INTRODUCTION

Most patients admitted with an acute surgical problem undergo some imaging during their in-patient stay. As computed tomography (CT) scanning becomes more readily available, it is becoming the mainstay of assessment. Recent studies have commented on the potential adverse effects of early cross-sectional imaging. This audit aimed to determine the use of early cross-sectional imaging and associated radiation dose in an acute surgical cohort.

PATIENTS AND METHODS

Data from 500 acute surgical patients were prospectively collected over a 3-month period. CT scans were undertaken, the effect on subsequent diagnostic and management decisions and the potential associated risks were evaluated.

RESULTS

Almost 40% of subjects underwent CT scanning. Of these, 20% did not alter management and could be deemed unnecessary. The radiation exposure equated to an age- and gender-specific risk of fatal cancer induction between 1 in 1675 and 1 in 7130.

CONCLUSIONS

Early-cross sectional imaging provides a valuable diagnostic adjunct. Decisions to expose patients to potentially hazardous radiation need to acknowledge the anticipated benefits versus risks.
Variation in Diagnosis of Apnea in Moderately Preterm Infants Predicts Length of Stay
Authors: Eichenwald Eric C. , Zupancic John A. F. , Mao Wen-Yang , Richardson Douglas K. , McCormick Marie C. , Escobar Gabriel J.
Published: December 2010

OBJECTIVE:

Apnea of prematurity is one of the most common diagnoses in the NICU. Because resolution of apnea is a usual precondition for discharge from the hospital, different monitoring practices might affect length of stay for premature infants. Our objective was to compare the proportion of 33 to 34 weeks' gestational age infants diagnosed with apnea in different NICUs and to assess whether variability in length of stay would be affected by the rate of documented apnea.

METHODS:

This was a prospective cohort study of moderately preterm infants who survived to discharge in 10 NICUs in Massachusetts and California.

RESULTS:

The study population comprised 536 infants born between 33 and 3467 weeks of which 264 (49%) were diagnosed with apnea. The mean postmenstrual age at discharge was higher in infants diagnosed with apnea compared with those without apnea (36.4 ± 1.3 vs 35.7 ± 0.8; P < .001, analysis of variance). Significant inter-NICU variation existed in the proportion of infants diagnosed with apnea (range: 24%–76%; P < .001). Postmenstrual age at discharge also varied between NICUs (range: 35.5 ± 0.6 to 36.7 ± 1.5 weeks; P < .001). As much as 28% of the variability in postmenstrual age at discharge between NICUs could be explained by the variability in the proportion of infants diagnosed with apnea.

CONCLUSIONS:

NICUs vary in the proportion of moderately preterm infants diagnosed with apnea, which significantly affects length of stay. Standardization of monitoring practices and definition of clinically significant cardiorespiratory events could have a significant impact on reducing the length of stay in moderately preterm infants.
Clinical Prediction Rule for RSV Bronchiolitis in Healthy Newborns: Prognostic Birth Cohort Study
Authors: Houben Michiel L. , Bont Louis , Wilbrink Berry , Belderbos Mirjam E. , Kimpen Jan L. L. , Visser Gerard H. A. , Rovers Maroeska M.
Published: December 2010

OBJECTIVE:

Our goal was to determine predictors of respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) among healthy newborns.

METHODS:

In this prospective birth cohort study, 298 healthy term newborns born in 2 large hospitals in the Netherlands were monitored throughout the first year of life. Parents kept daily logs and collected nose/throat swabs during respiratory tract infections. The primary outcome was RSV LRTI, which was defined on the basis of the combination of positive RSV polymerase chain reaction results and acute wheeze or moderate/severe cough.

RESULTS:

Of the 298 children, 42 (14%) developed RSV LRTI. Independent predictors for RSV LRTI were day care attendance and/or siblings, high parental education level, birth weight of >4 kg, and birth in April to September. The area under the receiver operating characteristic curve was 0.72 (95% confidence interval: 0.64–0.80). We derived a clinical prediction rule; possible scores ranged from 0 to 5 points. The absolute risk of RSV LRTI was 3% for children with scores of ≤2 (20% of all children) and 32% for children with all 4 factors (scores of 5; 8% of all children). Furthermore, 62% of the children with RSV LRTI experienced wheezing during the first year of life, compared with 36% of the children without RSV LRTI.

CONCLUSIONS:

A simple clinical prediction rule identifies healthy newborns at risk of RSV LRTI. Physicians can differentiate between children with high and low risks of RSV LRTI and subsequently can target preventive and monitoring strategies toward children at high risk.