bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study on High Performance Welding Materials for Pipeline Steels
Authors: Huang Zhijun , Miao Kai , Cao Xiudi , Wang Yutao
Published: December 2008

West-to-East Natural Gas Transmission Project is in great need of high quality steels of API grade X70 and suitable high quality welding materials. The weld of pipe should have high strength, high toughness and low sulphur and arsenic contents (less than or equal to 0.005 wt % respectively). The work performed in WISCO concerning welding wires of SAW, GMAW and SMAW and weldability of pipe steel is reported in this article. Steel grade X70 is a TMCP high strength and high toughness steel with low carbon equivalent. It has good weldability and is less susceptible to cold cracking in the heat-affected zone. Generally in order for weld to gain the same strength as the base metal, more alloying elements should be added into the weld. Therefore, it is likely that the weld is expected to be more susceptible to cold cracking. The mechanism of strengthening and toughening of the weld should be carefully investigated. WISCO has made great progress in both property improvement and manufacturing of welding materials. Through the addition of alloying elements, the influences of some alloying elements on the strength and toughness of welds, especially on the low temperature toughness were carried out. The results show that the upper shelves of the Charpy V transition curves for the weld metals remain high despite the different alloying elements. However, the influence of alloying degree on the low-temperature toughness is significant. The weld metals micro-alloyed with Ti,B and Ni, etc. have high acicular ferrite volume fractions in the metallographs, thereby possessing high strengths and high toughness. For SAW weld, the strength is more than 590MPa, the Charpy impact energy at −40°C above 180J; for the weld of gas metal arc welding, the Charpy impact energy at −30°C reaches 190J which are far better than some current specifications. If the welding is performed with caution, no cracks were found. HIC and SSCC test for corrosion resistance of the welds were also performed and the results fully met the requirements concerned. With respect to strength and toughness, chemistry and metallography, the HIC performance of welds was analysed.
Brazilian Onshore Pipelines Rehabilitation Program
Authors: Vasconcelos Elinaldo Albuquerque , Pessoa de Resende Marcos Jose´ , Silva Ju´nior Jose´ Lu´cio , Lira Menezes Carlos Alberto , Ribeiro Santos Jose´ Edson
Published: December 2008

The majority of the pipeline system in Brazil has more than 20 years in operation. The economy and demand for hydrocarbons, including natural gas, is growing in Brazil. Nowadays PETROBRAS-TRANSPETRO, Latin America’s largest carrier, is developing services to upgrade and rehabilitate sections of pipelines to provide compatible operational pressures with the actual and future demands for products. Services include pigging to check the pipe wall thickness, corrosion section replacement, evaluation of the class locations during the operation life of the pipeline, upgrading wall thickness where necessary and installation of new block valves. This is a case study of a 424 km pipeline in northeastern Brazil that crosses 32 municipal districts and supplies 180 direct consumers. The work included 37 replacements and upgrades that were completed in 36 days without affecting consumers. In Brazil, PETROBRAS-TRANSPETRO provides high investments for the rehabilitation of its pipelines, in order to guarantee the integrity and to increase the flow capacity. It is an important market that opens up in Latin America for engineering, construction and specialized inspection services companies.
Diverless Underwater GMA Welding for Pipeline Repair Using a Fillet Welded Sleeve
Authors: Woodward N. J. , Yapp D. , Blackman S. , Richardson I. M. , Widgery D. , Armstrong M. A. P. , Verley R. L. P. , Berge J. O.
Published: December 2008

The hyperbaric GMA welding procedure development carried out for underwater pipeline repair using a fillet welded sleeve is described. The fillet welded sleeve for repair offers greater alignment and installation tolerances than those associated with V-butt welding. In comparison with the hyperbaric TIG process, currently operated offshore with diver-assistance, GMA welding offers a relatively high deposition rate and is well suited to fillet joints. Parameter development enabling the stable deposition necessary for a large fillet weld is described, in addition to the repeatability of the weld quality and results from material property testing. Positional linear fillet welding work has been performed on API 5L X65 pipeline and sleeve material, using a specially developed metal-cored wire at an initial target depth of 360m. Previous work has demonstrated the robust nature of the hyperbaric GMAW process, with results produced at water depths down to 2,500m. The procedure development forms part of the Remote PRS programme, designing, building and testing a diverless underwater hyperbaric GMA welding repair spread, to be operated fully remotely.
PCE-1 Oil Pipeline/Point A 24” - Inspection Alternatives for a “Non-Piggable” Pipeline
Authors: Franzoi Aldo R. , Camerini Cla´udio S. , da Silva Jose´ A. P. , Bueno Se´rgio I. O. , de C. Lima Vinicius
Published: December 2008

The PCE-1, 24” pipeline was completed in 1982 and carries 15% of the Campos Basin’s oil production to the continent at about 800 m3/h. In 1995, it was repaired by inserting three subset mechanical connectors. This repair made it impossible to run any conventional “rigid pigs” with instruments or for cleaning. Through the adaptation of accessories and electronic devices in flexpigs, it became possible to clean and inspect geometrically and to evaluate the internal corrosion of the pipeline. The results permitted the safe operation of the pipeline with the connectors.
A Smart Location System
Authors: da Silva Jose´ Augusto Pereira , Antunes Rodrigo de Castro , Ribeiro Afonso Orlando de Jesus , Matsuura Minoru , Santa Cruz Se´rgio de Freitas , Costa dos Santos Jose´ Alberto , Hashiguchi De´cio Issao
Published: December 2008

This paper describes the technology used in the Intelligent Location System developed by PIPEWAY and includes some of the results already obtained optimizing repair time and logistic costs during the location of anomalies detected by intelligent pigs, a joint operation within the scope of the contract for Subsea Pipeline Recovery in the Guanabara Bay with Petrobras/Transpetro and GDK Engenharia. The system uses the ELF (Extra Low Frequency) transmission and reception technology at points near a pipe, with or without concrete coating, whose signals are recorded in the inspection tool memory to accurately establish reference points, thus preventing excessive dig work or dredging when human and operational risks tend to be high. By recording the frequencies transmitted by the Smart Location System in the inspection tool memory, this extremely serviceable technology for approaching anomalies in onshore or offshore pipelines has proved to be a powerful tool, with centimetric precision and low costs when facing adverse conditions, where a slight difference of meters or the difficulty to visualize the anomaly from the outside may represent significant savings. This system provides a solution for the lack of fixed reference points such as valves, magnets and other equipments that could help to locate the anomalies. The idea of finding an engineering solution that would provide a faster and efficient method for identifying those anomalies was started in 2002, after some inspections were made with geometric and/or thickness loss instrumented pigs in an attempt to approach anomalies detected in offshore pipelines in the Guanabara Bay, whose bottom is intensely silted up, offering poor visibility, and where no physical references were installed in less than a one-kilometer distance from the target features. The main purpose of using this technology is the improvement in pipeline and operational reliability so that the operator is able to quickly relate the severity of the situation to the actual operating conditions. A short analysis of the main costs involved in the application of this localization system, including the mobilization of a geometry inspection tool, would show that investments could benefit from this technique. This becomes clear when considering diving, dragging or digging costs required by traditional methods whose intrinsic high costs and risks may represent non-anticipated costs when new exploitations are required to identify anomalies.
Monitoring of Pull-Load and Borehole Pressure During HDD Installations
Authors: Alloche Erez N. , Baumert Mike E.
Published: December 2008

Quality control and quality assurance during horizontal directional drilling installations (HDD) is a topic that is gaining increasing interest and concern in the engineering community as HDD is becoming a mainstream construction technology. The paper describes a method for increasing the transparency of pulled-in-place trenchless installations using an array of sensors mounted within a protective casing, located ahead of the pipe product pull head. The data collected by the sensors, including pull-load and borehole pressure, is stored on a memory chip placed onboard the platform, thus creating a permanent electronic record of the installation. This data can be used by contractors, consultants and owners for quality control purposes and the improvement of design models and construction practices. In addition, real-time information can be provided to the operator, giving him/her the opportunity to detect potential problems in a timely manner so that appropriate mitigation measures can be taken.
Research on Contamination Caused by the Topographical Difference in Batch Transportation
Authors: Gong Jing , Kang Zhengling , Yan Dafan
Published: December 2008

This paper presents the mixing model for illuminating the influence of density, viscosity and the topographical height difference on the interfacial product-mixing in pipeline, in which a new virtual axial dispersion coefficient related with contamination concentration and its gradient was utilized. With the simplification of the Reynolds number of the mixture unvaried with the concentration, contamination concentration distribution relevant to density difference and gravitation acceleration etc was developed. When the Reynolds number of the mixture was a function of concentration, the mixing model was solved numerically by Crank-Nicholson implicit difference scheme. Analysis indicated that the effect of inclination angle on contamination decreases gradually with the increase of the distance traveled by the interface and the contamination Reynolds number. Particularly, the degree of effect became invisible when pipeline is in completely turbulent flow, and the Reynolds number is greater than the critical Reynolds number defined by Austin and Palfrey while the pipeline was considerably long. In the undulate long-distance multi-products pipeline, contamination due to topographical height difference can be ignored in turbulent flow while the Reynolds number is greater than critical Reynolds number.
Hydrotest Protocol for Applications Involving Lower-Toughness Steels
Authors: Leis B. N. , Galliher R. D. , Sutherby R. L. , Sahney R.
Published: December 2008

Hydrotesting has been used by the transmission pipeline industry for decades, and remains the only effective means to control stress-corrosion cracking until in-line inspection is proven. This paper addresses the conditions for effective proof-pressure testing in terms of ductile fracture referenced to peak pressure and hold-time, and then contrasts these to the response in low-toughness situations. Fracture properties typical of an early-vintage electrical-resistance weld (ERW) seam were determined and used as the basis to simulate the response at toughness levels typical of some lower-toughness steels. Fracture properties characterized via Charpy-vee notch (CVN) energy showed low energy to failure, and confined inelastic response characteristic of linear-elastic fracture mechanics. Hydrotest and service breaks associated with cracking in an ERW seam showed a very small shear lip and often showed chevrons pointing back toward the origins — features consistent with the CVN results and characteristic of low fracture ductility. The results indicate hydrotest protocols derived and effective for ductile fracture are not directly applicable when brittle-like fracture controls. Hydrotesting was indicated to be an effective means to expose defects in ERW seams, as rupture is indicated to occur under typical hydrotest conditions. Simulated growth of the scope of defect lengths and depths evident along hydrotest breaks showed virtually no time dependent cracking, which means the hold time at maximum pressure should be reduced to the minimum time required to ensure all pipe in the test section has reached its target pressure.
Two Case Studies of Trenchless Technologies in the Urban Environment
Authors: Krywiak Dave , Kiefer Werner , Arnold David , Hull Kirstine
Published: December 2008

In 1998, EPCOR undertook an inspection program on the condition of 14 of their underground high voltage transmission lines where they crossed the riverbed of the North Saskatchewan River within the City of Edmonton. Based on the findings of this investigation, it was determined that two of the river crossings were at serious risk of mechanical damage. It was decided that they would be replaced by horizontal directional drilling (HDD) methods, at a sufficient depth into the bedrock below the river bottom to remove any risk of failure due to mechanical damage. This paper examines all phases of the work carried out from project inception to construction of the two crossings, first in the spring of 2003 and then in the dead of winter of 2004. Some of the technical considerations inherent in the design of the HDD installations included geotechnical concerns with potential drilling fluid frac-out and slope stability, as well as heat dissipation rates and operating constraints of the 72 kV oil-filled pipe type high voltage cables. This paper will focus on project constraints imposed by the existing urban (park and residential) locations, community and stakeholder concerns and the regulatory and approval requirements of three levels of government. In addition to the necessary geotechnical investigations, other investigations included addressing potential impacts on the river, vegetation, wildlife, archaeological, noise and construction concerns. An extensive public communications program was completed that included a number of open houses, delivery of construction notices to all surrounding residences, meetings with community league executives and other stakeholder groups. The paper will describe the challenges that the project team faced and how they were overcome and the amount of time and effort that went in to meeting those challenges. The paper will end with a discussion of the costs and time frames required to complete such a project.
Source Influence for Focusing Potential of Guided Waves in Hollow Cylinders by Using a Circumferential Phased Array
Authors: Zhang Li , Gavigan Brian J. , Rose Joseph L.
Published: December 2008

The phased array focusing technique is being developed with the intent to inspect hundreds of feet of pipeline from a single array position. The single array position is beneficial if access to a pipe is limited, e.g. steam pipes onboard U.S. Naval ships, nuclear power plant pipes, oil and natural gas pipelines. The steam pipes have a protective coating which would ordinarily be removed and replaced for an inspection. From a single array position, ultrasonic guided waves propagate under the coating, down the length of the pipe and return information about potential defects. Focusing the ultrasonic energy at a predetermined location along the length of the pipe enhances the ability to detect defects that current state of the art inspection systems cannot. Focusing is achieved by applying excitation time delays to a multi-channel signal generation system. The excitation sources are equally spaced about the circumference of the pipe. Time delays are calculated using theoretically generated angular displacement profiles in a hollow cylinder. These theoretical displacement profiles are dependent upon excitation source influences. In this paper, the excitation source influence on focusing potential in pipe was studied. Further, focusing potential contour plots for different frequencies and distances from the excitation source were created. Based on the contour plots, sample focusing experiments were carried out.
Modeling of Annular Pressures in Horizontal Directional Drilling
Authors: Ariaratnam Samuel T. , Stauber Richard , Harbin Bruce
Published: December 2008

Horizontal Directional Drilling (HDD) is an established trenchless construction method for the installation of underground utilities and pipelines. Subsequently, the method is becoming widely accepted as a cost-effective alternative to traditional open-cut construction. However, the occurrence of hydraulic fracturing, resulting in the migration of drilling fluid to the surface has placed the HDD process under scrutiny, especially when being considered for environmentally sensitive projects. Hydraulic fracturing results from an excess buildup of fluidic pressure within the borehole. Models have been developed to predict borehole pressures; however, there is limited information available on the relationship between drilling returns and fluid composition to these pressures. A research program was undertaken to model and determine flow characteristics for drilling returns under a variety of soil conditions and bore penetration rates. Nine soil samples were gathered based on the Unified Soil Classification System (USCS) and their respective rheological properties were obtained for different drilling fluids and target slurry densities. This paper presents, as an example, a comparison and analysis of the predicted borehole pressures of clayey-sand (SC) soil in a large directional drill rig application and provides recommendations for contractors when attempting installations in various geological formations. The pressure effects of pipe eccentricity within a borehole were analyzed using a computer model. The result of this research is a simplified approach for predicting downhole fluid pressures for a wide range of project parameters that can be used as a guide to minimize the occurrence of hydraulic fracturing.
SCC Detection and Coating Disbondment Detection Improvements Using the High Resolution EMAT ILI-Technology
Authors: Beuker Thomas , Alers Ron , Brown Bryce , Alers George
Published: December 2008

Pipeline deterioration by stress corrosion cracking (SCC) is an increasing challenge for the pipeline industry. Recent incidents and the lately issued OPS advisory bulletin in the U.S., emphasize the worldwide focus on this phenomenon. Coating disbondment is understood as a precursor to SCC by increasing the susceptibility of the pipeline for corrosion. The presented High Resolution ILI-technology, based on a novel concept of an Electromagnetic Acoustic Transducer (EMAT), allows both, the detection of SCC and the detection of disbonded coating, using two independent measurement methods. Thus, the technology combines proactive and reactive measures to improve the reliability of a pipeline that is susceptible to SCC. Data from a series of full-scale tests, obtained with the ILI-EMAT prototype, will be presented. The tests were conducted on pipe containing natural SCC colonies. The improvement of SCC detection capability will be demonstrated.
Reliability Based Assessment of Minimum Reelable Wall Thickness for Reeling
Authors: Brown George , Tkaczyk Tomasz , Howard Brett
Published: December 2008

The traditional calculation of minimum reelable wall thickness assumes that there is no variation in pipe properties, and that the curvature increases to a maximum on the reel. When a designer checks that a pipe will not buckle during reeling, the designer is usually checking that the curvature at which the peak plastic moment occurs is less than the vessel reel curvature. Design codes specify appropriate safety factors to ensure this requirement is met, where the curvature at which the peak plastic moment occurs is based upon the testing of pipes under pure moment loading. However, it is known that mismatches between adjacent pipe ends at a weld can cause high localised curvatures in excess of the reel curvature and in extreme cases buckling can occur. This paper examines the pipe behaviour during reeling when strength mismatches are present between adjacent pipes at a weld. It shows that the traditional, and currently used, method of calculating the minimum reelable wall thickness does not consider the maximum bending strain during the actual reeling process. The method does however consider a broadly equivalent process and it is shown that the simplified traditional approach is a credible criterion that provides a more than adequate margin to failure when combined with limited extra control of the specification of pipe purchased for reeling. The assessment procedure is outlined along with a description of the detailed Finite Element Analysis (FEA) modelling, full scale testing and field measurements performed to verify the method and results.
3D Finite Element Modeling of Buried Pipelines: On the Interaction of Beam Action of Pipelines and Cross Sectional Behavior
Authors: Hendriks Max A. N. , ’t Hart C. Marcel P. , Frissen Chantal M.
Published: December 2008

A common finite element modeling approach for buried pipelines is the combined use of beam and spring elements. Typical loads are soil settlements, temperature variations, internal pressures, neutral topsoil weight load and traffic loads. The beam elements represent the pipeline; assemblies of spring elements represent the surrounding soil comprising an elastoplastic bedding with friction. The choice for such finite element models is a pragmatic one. The models are relatively easy to construct and the analyses can be performed within reasonable calculation time on an average PC. From a mechanical point of view the problem of a buried pipeline subjected to subsidence, or an offshore pipeline subjected to sand waves, is of a full 3D nature. Beam elements and spring elements only partly incorporate full 3D effects. In practice the common finite element models are therefore enhanced to take into account 3D effects that would be otherwise omitted. A major point is the distinction between beam action and cross sectional behavior of pipes in straight and curved sections and their mutual interaction. This paper discusses the pros and cons of two possible finite element approaches which deal with this full 3D problem. In the final example it is illustrated that the two approaches gives similar results for the relatively simple problem of a buried bended pipe subjected to a temperature load and internal pressure.
Full-Scale Tests of Cold Bend Pipes
Authors: Sen M. , Cheng J. J. R. , Murray D. W. , Zhou J. , Adams K. , Yoshizaki K. , Fukuda N. , Como M. , Cerelli E.
Published: December 2008

An experimental program sponsored jointly by SNAM Rete Gas, Tokyo Gas Co., Ltd. and TransCanada Pipelines Ltd. was conducted on cold bend pipes under combined loading. These tests were designed to study the local buckling behavior and to develop the critical compressive strain criteria for cold bend pipes under combined loading. The test program includes eight full-scale specimens of NPS24 and NPS30 pipes with pipe thickness up to 14.3 mm. The test parameters include different D/t ratios (44, 69, and 93), material grades (X60, X65, and X80), bend angles (1.0 to 1.5 degree/diameter), and operation pressures (0%, 40%, 60%, and 80% of SMYS). In addition to full-scale tests, initial imperfections and residual strains due to cold bend processes were also measured. This paper describes the test specimens, test setup, instrumentation, and test procedures used in the program. A brief discussion of the test results is also covered in the paper.
The Application of the Environmental and Social Standards (“Safeguard Policies”) of the World Bank to Pipeline Projects
Authors: Nickel Elke , Robelus Robert
Published: December 2008

The procedural standard “Environmental Assessment” and the qualitative standards of the World Bank (International Bank for Reconstruction and Development) have gained additional significance in the environmental risk analysis of multilateral banks since they were compiled into the system of “Safeguard Policies” in 1998. Their position in international lending was further consolidated by the strict application of the Safeguard Policies in the EIA for the Chad-Cameroon pipeline project which was approved in June 2000 by the Board of the World Bank. Finally, the largest internationally active commercial banks (e.g. WESTLB [Germany] CITIBANK [USA]) in 2003 voluntarily committed themselves to compliance with the World Bank standards in major projects. The “test project” for compliance with this voluntary standard is the Baku-Tiblisi-Ceyhan oil pipeline, which is being financed by both multilateral and commercial banks. The presentation concentrates on the application of the Safeguard Policies in pipeline projects during the planning and implementation phases. Using the example of the the Baku-Tiblisi-Ceyhan oil pipeline, the requirements established under Operational Directive (OP) 4.01 Environmental Assessment are discussed on the basis of selected criteria, and certain developments in the area of “best practice” are demonstrated. A further main focus of the presentation is the discussion over recent tendencies in the application of the Safeguard Policies and the demand of further developments and research.
Effect of Pipe and Weld Metal Post-Yield Characteristics on Plastic Straining Capacity of Axially Loaded Pipelines
Authors: Denys Rudi , De Waele Wim , Lefevre Anton
Published: December 2008

Girth welds in pipelines subject to longitudinal plastic tensile strains are critical regions of the pipeline. As girth welds might contain flaws of some form or other, it is of paramount interest to have a thorough understanding of the deformation characteristics of girth welds in the post-yield loading range. The response of a defective weld to plastic strains depends on many variables. While toughness is an important variable, large-scale tests demonstrate that the plastic straining capacity is directly affected by the mechanical properties of the materials surrounding the defect. The purpose of this paper is to describe the effect of the interrelation between the pipe and weld metal post-yield characteristics on the straining capacity of girth welds containing a defect.
Revision of Boltzmann statistics for a finite number of particles
Authors: Kakorin S.
Published: December 2008

The Stirling approximation, ln(N!)≈Nln(N)−N, is used in the literature to derive the exponential Boltzmann distribution. We generalize the latter for a finite number of particles by applying the more exact Stirling formula and the exact function ln(N!). A more accurate and analytical formulation of Boltzmann statistics is found in terms of the Lambert W-function. The Lambert-Boltzmann distribution is shown to be a very good approximation to the exact result calculated by numerical inversion of the Digamma-function. For a finite number of particles N the exact distribution yields results that differ from the usual exponential Boltzmann distribution. As an example, the exact Digamma-Boltzmann distribution predicts that the constant-volume heat capacity of an Einstein solid decreases with decreasing N. The exact Digamma-Boltzmann distribution imposes a constraint on the maximum energy of the highest populated state, consistent with the finite total energy of the microcanonical ensemble.
When hot water freezes before cold
Authors: Katz J. I.
Published: December 2008

I suggest that the origin of the Mpemba effect (the freezing of hot water before cold) is due to freezing-point depression by solutes, either gaseous or solid, whose solubility decreases with increasing temperature so that they are removed when water is heated. The solutes are concentrated ahead of the freezing front by zone refining in water that has not been heated, reducing the temperature of the freezing front, and thereby reducing the temperature gradient and heat flux, slowing the progress of the freezing front. I present a simple calculation of this effect, and suggest experiments to test this hypothesis.
Commissioning and quality assurance for intensity‐modulated radiotherapy with dynamic multileaf collimator: Experience of the Pontificia Universidad Católica de Chile
Authors: Venencia Carlos Daniel , Besa Pelayo
Published: December 2008

The objective of this paper is to present our experience in the commissioning and quality assurance (QA) for intensity‐modulated radiotherapy (IMRT) using the dynamic multileaf collimator (dMLC), sliding window technique. The connectivity and operation between all IMRT chain components were checked on the Varian equipment. Then the following tests were performed: stability of leaf positioning and leaf speed, sensitivity to treatment interruptions (acceleration and deceleration), evaluation of standard field patterns, stability of dMLC output, segmental dose accuracy check, average leaf transmission, dosimetric leaf separation, effects of lateral disequilibrium between adjacent leaves in dose profiles, and multiple carriage field verification. Standard patterns were generated for verification: uniform field, pyramid, hole, wedge, peaks, and chair. Weekly QA protocol includes sweeping gap output, garden fence test (narrow bands, 2 mm wide, of exposure spaced at 2‐cm intervals), and segmental dose accuracy check. Monthly QA includes sweeping gap output at multiple gantry and collimator angles, sweeping gap off‐axis output, picket fence test (eight consecutive movements of a 5‐cm wide rectangular field spaced at 5‐cm intervals), stability of leaf speed and leaf motor current test (PWM test). Our patient QA procedure consists of an absolute dose measurement for all treatment fields in the treatment condition, analysis of actual leaf position versus planned leaf position (dynalog files) for each treatment field, film relative dose determination for each field, film relative dose determination for the plan (all treatment fields) in two axial planes, and patient positioning verification with orthogonal films. The tests performed showed acceptable results. After over one year of IMRT treatment, the routine QA machine checks confirmed the precision and stability of the IMRT system.

PACS number: 87.53.Xd, 87.53.Dq, 87.53.Mr
Book Review
Authors: Benedict Stanley H.
Published: December 2008

Review of Radiation Oncology Physics: A Handbook for Teachers and Students, edited by Ervin B. Podgorsak, PhD
A comparison of two commercial treatment‐planning systems for IMRT
Authors: Petric M. Peter , Clark Brenda G. , Robar James L.
Published: December 2008

This study compared the clinical functionality of BrainSCAN (BrainLAB) and Helios (Eclipse, Varian) for intensity‐modulated radiation therapy (IMRT) treatment planning with the aim of identifying practical and technical issues. The study considered implementation and commissioning, dose optimization, and plan assessment. Both systems were commissioned for the same 6 MV photon beam equipped with a high‐resolution multileaf collimator (Varian Millennium 120 leaf). The software was applied to three test plans having identical imaging and contour data. Analysis considered 3D axial dose distributions, dose‐volume histograms, and monitor unit calculations. Each system requires somewhat different input data to characterize the beam prior to use, so the same data cannot be used for commissioning. In addition, whereas measured beam data was entered directly into Helios with minimal data processing, the BrainSCAN system required configured beam data to be sent to BrainLAB before clinical use. One key difference with respect to system commissioning was that BrainSCAN required high resolution data, which necessitated the use of detectors with small active volumes. This difference was found to impact on the ability of the systems to accurately calculate dose for highly modulated fields, with BrainSCAN being more successful than Helios. In terms of functionality, the BrainSCAN system uses a dynamically penalized likelihood inverse planning algorithm and calculates four plans at once with various relative weighting of the planning target and organ‐at‐risk volumes. Helios uses a gradient algorithm that allows the user to make changes to some of the input parameters during optimization. An analysis of the dosimetry output shows that, although the systems are different in many respects, they are each capable of producing substantially equivalent dose plans in terms of target coverage and normal tissue sparing.

PACS number: 87.53.Tf
Intraoperative radiotherapy using a mobile electron LINAC: A retroperitoneal sarcoma case
Authors: Beddar A. Sam , Krishnan Sunil
Published: December 2008

The advent of mobile LINACs for use in intraoperative radiation therapy (IORT) promises to make IORT more accessible than before and easier to deliver to patients undergoing surgery. Although mobile IORT systems have been available since 1999, few treatment centers currently use them. Here, we present the case of a typical patient undergoing IORT for retroperitoneal sarcoma to show how easy these mobile systems are to use and how adaptable they are within the operating room (OR) environment. We also discuss the roles and coordination of multidisciplinary team members during IORT and the feasibility of using mobile LINACs for IORT.

PACS number(s):
Accuracy of 3D volumetric image registration based on CT, MR and PET/CT phantom experiments
Authors: Li Guang , Xie Huchen , Ning Holly , Citrin Deborah , Capala Jacek , Maass‐Moreno Roberto , Guion Peter , Arora Barbara , Coleman Norman , Camphausen Kevin , Miller Robert W.
Published: December 2008

Registration is critical for image‐based treatment planning and image‐guided treatment delivery. Although automatic registration is available, manual, visual‐based image fusion using three orthogonal planar views (3P) is always employed clinically to verify and adjust an automatic registration result. However, the 3P fusion can be time consuming, observer dependent, as well as prone to errors, owing to the incomplete 3‐dimensional (3D) volumetric image representations. It is also limited to single‐pixel precision (the screen resolution). The 3D volumetric image registration (3DVIR) technique was developed to overcome these shortcomings. This technique introduces a 4th dimension in the registration criteria beyond the image volume, offering both visual and quantitative correlation of corresponding anatomic landmarks within the two registration images, facilitating a volumetric image alignment, and minimizing potential registration errors. The 3DVIR combines image classification in real‐time to select and visualize a reliable anatomic landmark, rather than using all voxels for alignment. To determine the detection limit of the visual and quantitative 3DVIR criteria, slightly misaligned images were simulated and presented to eight clinical personnel for interpretation. Both of the criteria produce a detection limit of 0.1 mm and 0.1°. To determine the accuracy of the 3DVIR method, three imaging modalities (CT, MR and PET/CT) were used to acquire multiple phantom images with known spatial shifts. Lateral shifts were applied to these phantoms with displacement intervals of . The accuracy of the 3DVIR technique was determined by comparing the image shifts determined through registration to the physical shifts made experimentally. The registration accuracy, together with precision, was found to be: for CT/CT images, for MR/MR images, and for PET/CT images. This accuracy is consistent with the detection limit, suggesting an absence of detectable systematic error. This 3DVIR technique provides a superior alternative to the 3P fusion method for clinical applications.

PACS numbers: 87.57.nj, 87.57.nm, 87.57.‐N, 87.57.‐s
Rotational total skin electron irradiation with a linear accelerator
Authors: Reynard Eric P. , Evans Michael D.C. , Devic Slobodan , Parker William , Freeman Carolyn R. , Roberge David , Podgorsak Ervin B.
Published: December 2008

The rotational total skin electron irradiation (RTSEI) technique at our institution has undergone several developments over the past few years. Replacement of the formerly used linear accelerator has prompted many modifications to the previous technique. With the current technique, the patient is treated with a single large field while standing on a rotating platform, at a source‐to‐surface distance of 380 cm. The electron field is produced by a Varian 21EX linear accelerator using the commercially available 6 MeV high dose rate total skin electron mode, along with a custom‐built flattening filter. Ionization chambers, radiochromic film, and MOSFET (metal oxide semiconductor field effect transistor) detectors have been used to determine the dosimetric properties of this technique. Measurements investigating the stationary beam properties, the effects of full rotation, and the dose distributions to a humanoid phantom are reported. The current treatment technique and dose regimen are also described.

PACS numbers: 87.55.ne, 87.53.Hv, 87.53.Mr
Compensator‐based intensity‐modulated radiation therapy for malignant pleural mesothelioma post extrapleural pneumonectomy
Authors: Javedan Khosrow , Stevens Craig W. , Forster Kenneth M.
Published: December 2008

The present work investigated the potential of compensator‐based intensity‐modulated radiation therapy (CB‐IMRT) as an alternative to multileaf collimator (MLC)–based intensity‐modulated radiation therapy (IMRT) to treat malignant pleural mesothelioma (MPM) post extrapleural pneumonectomy.

Treatment plans for 4 right‐sided and 1 left‐sided MPM post‐surgery cases were generated using a commercial treatment planning system, XIO/CMS (Computerized Medical Systems, St. Louis, MO). We used a 7‐gantry‐angle arrangement with 6 MV beams to generate these plans. The maximum required field size was . We evaluated IMRT plans with brass compensators (•Decimal, Sanford, FL) by examining isodose distributions, dose–volume histograms, metrics to quantify conformal plan quality, and homogeneity. Quality assurance was performed for one of the compensator plans.

Conformal dose distributions were achieved with CB‐IMRT for all 5 cases, the average planning target volume (PTV) coverage being 95.1% of the PTV volume receiving the full prescription dose. The average lung (volume of lung receiving 20 Gy) was 1.8%, the mean lung dose was 6.7 Gy, and the average contralateral kidney was 0.6%. The average liver dose was 34.0% for the right‐sided cases and 10% for the left‐sided case. The average monitor units (MUs) per fraction were 980 MUs for the 45‐Gy prescriptions (mean: 50 Gy) and 1083 MUs for the 50‐Gy prescriptions (mean: 54 Gy).

Post surgery, CB‐IMRT for MPM is a feasible IMRT technique for treatment with a single isocenter. Compensator plans achieved dose objectives and were safely delivered on a Siemens Oncor machine (Siemens Medical Solutions, Malvern, PA). These plans showed acceptably conformal dose distributions as confirmed by multiple measurement techniques. Not all linear accelerators can deliver large‐field MLC‐based IMRT, but most can deliver a maximum conformal field of . It is possible and reasonable to deliver IMRT with compensators for fields this size with most conventional linear accelerators.

PACS numbers: 87.56.ng, 87.56.N, 87.55.D, 87.55.dk
An empirical model of electronic portal imager response implemented within a commercial treatment planning system for verification of intensity‐modulated radiation therapy fields
Authors: Khan Rao F.H. , Ostapiak Orest Z. , Szabo Joe J.
Published: December 2008

Quality assurance (QA) of an intensity‐modulated radiation therapy (IMRT) plan is more complex than that of a conventional plan. To improve the efficiency of QA, electronic portal imaging devices (EPIDs) can be used. The major objective of the present work was to use a commercial treatment planning system to model EPID response for the purpose of pre‐treatment IMRT dose verification.

Images were acquired with an amorphous silicon flat panel portal imager (aS500: Varian Medical Systems, Palo Alto, CA) directly irradiated with a 6‐MV photon beam from a Clinac 21EX linear accelerator (Varian Medical Systems). Portal images were acquired for a variety of rectangular fields, from which profiles and relative output factors were extracted. A dedicated machine model was created using the physics tools of the Pinnacle3 (Philips Medical Systems, Madison, WI) treatment planning system to model the data. Starting with the known photon spectrum and assuming an effective depth of 7 cm, machine model parameters were adjusted to best fit measured profile and output factors. The machine parameters of a second model, which assumed a 0.8 MeV monoenergetic photon spectrum and an effective depth in water of 3 cm, were also optimized. The second EPID machine model was used to calculate planar dose maps of simple geometric IMRT fields as well as a 9‐field IMRT plan developed for clinical trials credentialing purposes.

The choice of energy and depth for an EPID machine model influenced the best achievable fit of the optimized machine model to the measured data. When both energy and depth were reduced by a significant amount, a better overall fit was achieved. In either case, the secondary source size and strength could be adjusted to give reasonable agreement with measured data. The gamma evaluation method was used to compare planar dose maps calculated using the second EPID machine model with the EPID images of small IMRT fields. In each case, more than 95% of points fell within 3% of the maximum dose or 3 mm distance to agreement. These results are slightly poorer than those obtained using an ion chamber array, which confirms agreement to within 2% of the maximum dose or 2 mm distance to agreement for all points within these fields.

PACS numbers: 87.55Qr, 87.56.Fc
A plesiotherapy technique for the post‐operative treatment of skin cancer using Ir192 microSelectron.
Authors: Abatzoglou Ioannis , Tsoutsou Pelagia , Koukourakis Michael I.
Published: December 2008

We describe a technique of postoperative irradiation of skin cancer using plesiotherapy with Ir192 high dose rate microSelectron afterloading system (Nucletron, Veenendaal, Netherlands). The clinically defined area is drawn on the skin and the flexible ‘skin applicator’ is then orientated so that the drawn skin area is encompassed within the catheter defined surface. Using a thin pewter wire, the skin drawn area is copied on the air‐adjacent surface of the applicator. Ex vivo CT simulation follows. The data are then transferred to the radiotherapy planning computer and the catheters are virtually reconstructed. The isodose curve chosen to prescribe the dose is 3 mm to 5 mm away from the skin surface. Three fractions of 8Gy are scheduled, 1 week apart, delivering a radiobiological equivalent of 48Gy of standard radiotherapy within 2 weeks. Our preliminary experience shows excellent early skin tolerance. The study is ongoing to assess efficacy and late effects.

PACS number: 87.53.Jw
Interleukin-6 is an important in vivo inhibitor of intestinal epithelial cell death in mice
Authors: Jin Xiaoling , Zimmers Teresa A , Zhang Zongxiu , Pierce Robert H , Koniaris Leonidas G
Published: December 2008

Background and aims

Interleukin-6 (IL-6) is a well-recognised mediator of liver disease and regeneration. However, the in vivo effects of IL-6 on enterocytes and the intestinal tract have not been elucidated. We sought to determine the in vivo effects of IL-6 on enterocytes.

Methods

Murine models of increased or absent IL-6 were examined.

Results

Systemic, high-dose IL-6 administration to mice over 7–10 days resulted in intestinal hyperplasia with a ∼40% increase in small bowel mass and in intestinal villus height. No increase in crypt cell proliferation was noted. IL-6 administration was associated with induction of pSTAT3 in enterocytes along the lower and middle regions of villi but not in crypts. IL-6 administration was also associated with induction of anti-apoptotic proteins including pAKT, and FLIP along with decreased executor caspase activity and PARP cleavage. Pulse bromodeoxyuridine labelling demonstrated equivalent crypt cell proliferation rates but prolonged enterocyte lifespan and slowed enterocyte migration rates in IL-6 treated mice. Furthermore, IL-6 treated mice showed less intestinal injury and improved barrier function following ischaemia reperfusion of the small bowel. Conversely, Il6 null mice exhibited impaired recovery following massive enterectomy and increased apoptosis after 5-fluorouracil chemotherapy relative to wild-type controls.

Conclusions

IL-6 inhibited both constitutive and induced enterocyte cell death in vivo. Loss of IL-6 in mice resulted in increased activation of pro-apoptotic and necrotic pathways in enterocytes after injury. Therapies that augment IL-6 or its signalling pathways may help manage intestinal disorders associated with increased apoptosis, necrosis and gut injury.
Rare earth elements in the bimodal Mount Peyton batholith: Evidence of crustal anatexis by mantle-derived magma
Authors: Strong D. F. , Dupuy C.
Published: December 2008

The Mount Peyton batholith of central Newfoundland is one of many Siluro-Devonian ("Acadian") plutons of the Appalachians with contrasting mafic and silicic compositions. The distributions of rare earth and other trace elements in 18 representative samples indicate that the contrasting rock types are not genetically related by any crystal–liquid fractionation process. Rather they support earlier suggestions that the granitic melt was generated by crustal melting due to intrusion of the mantle-derived mafic magma, and the two evolved independently through processes involving some crystal fractionation and contamination with country rocks during ascent.
Analysis of a rock slope with internal dilation
Authors: Martin C. D. , Kaiser P. K.
Published: December 2008

A class of rock slope failures exists in which the mode of failure requires the existence or creation of internal shears to accommodate large internal slide mass distortion. These internal displacements are required to allow motion along the basal slip surface. This paper demonstrates that the more traditional limit equilibrium methods of analysis are often conservative when used to assess the stability of slopes with this failure mechanism. As a result, back analysis may overestimate the available shear resistance. A method of analysis capable of handling this failure mechanism was proposed by S. K. Sarma. A case history from the Revelstoke Hydroelectric Project, British Columbia, is used to demonstrate that these internal shears were required for movement to occur and that passive anchors inside the sliding rock mass can be used to improve the overall slope stability. No attempt is made to evaluate the actual factor of safety of the three-dimensional slide mass. Key words: rock slope, foliation shear, stability analysis, dilation, internal shears, passive anchors.