bluuebunny/crossref_metadata_2025 huggingface dataset:
Corrosion Monitoring as an Integral Component of an Effective Corrosion Management Program
Authors: Bich Nguyen N. , Kubian Eric
Published: December 2008

An effective pipeline integrity management program requires four components: a comprehensive understanding of corrosion mechanisms taking place in the pipeline, an effective corrosion mitigation plan responsive to the expected mechanisms, a monitoring plan to provide feedback to the corrosion mitigation plan and a selective inspection plan to validate the corrosion mechanisms and mitigation effectiveness and to confirm the pressure-containment capability of the pipeline. This paper describes several case studies where the use of a suitable corrosion monitoring device has led to an early warning of the lack of performance of the mitigation measures which, if left unchecked, could result in more severe corrosion and eventually, failure.
Deep Water Remote Pipeline Repair Using Welded Sleeve Technique
Authors: Berge Jan Olav , Armstrong Michael , Verley Richard
Published: December 2008

A technique for sub-sea pipeline repair using remote welding without the use of diverse has been developed. The technique involves the installation of an oversized pipe segment (sleeve) over the join by threading the pipe ends through the sleeve and performing a sub-sea fillet weld between the pipe and sleeve on each end. Current traditional welding techniques use pipe end butt to butt welding performed with the aid of divers in a habitat and are therefore depth limited. This technique is fully remote controlled and has been proven by simulating conditions in a hyperbaric chamber to work down to at least 2500 msw represented by 250 bar. This paper describes the technique, the structural considerations, and the equipment currently being built to perform this task, which will be in test in the second half of 2004 with sub-sea trials to follow. This paper compliments the paper IPC04-0630 “Diverless underwater GMA welding for pipeline repair using a fillet welded sleeve” [2], in which the welding procedural development is described. When compared with traditional welding or mechanical options (in particular for large pipes), the technique provides a much cheaper repair option.
Pressure Based Leak Detection for Pipelines, Implemented at Business Unit of Production and Exploration of Petrobras in Rio Grande do Norte and Ceara´
Authors: Hovey Diane J. , Rolim Tuerte A. , de Oliveira Abelindo A.
Published: December 2008

This paper presents the experiences of the Petrobras Business Unit (UN-RNCE), located in Rio Grande del Norte state of Brazil, during the installation and startup of a pipeline leak detection system. The application involves nine multiphase oil pipelines that link several productions facilities together over a total distance of 450-Km. Prior to the selection and installation of this leak detection system a significant pipeline accident resulted in the pollution of Guanabara bay. The leak was not detected by the existing monitoring equipment because of the two phase and multiphase pipeline characteristics. The UN-RNCE decided to install EFA Technologies, Inc., Pressure Point Analysis (PPA)™ technology in order to detect leaks. It is a sophisticated statistical method for leak detection, uses very simple field instrumentation, which facilitates ease of installation and maintenance. However, in order to get the best performance out of the system, it is necessary to understand how the pipeline control processes operate and to have a fast, reliable SCADA system for long distance communication. This paper includes the test results, conclusions and the recommendations to expand the system.
Deflected Stress Corrosion Cracks in the Pipeline Steel
Authors: Sutherby Robert , Chen Weixing
Published: December 2008

This research reports a special case of stress corrosion cracks (SCC) in the pipeline steels that had propagated in the direction deviated from the pipe radial direction. It was characterized that the cracks were intergranular in nature with relatively wide crack crevice. Most of crack being characterized consisted of two segments: a crack segment near pipe surface that is normal to the axis of hoop stress, and the subsequent segment that is inclined to the axis of the hoop stress. The segment near the surface was usually less than 1.5 mm long, and the inclined one was up to 10 mm in length. The angle of the inclined segment was dominantly in the range of 30° to 60°. To understand the mechanisms related to the deflected crack growth, the microstructure of the pipeline steels was studied. It was found that The pipeline steel is characterized with a sandwich-like microstructure, for which it is harder at the surface (∼ 1.5 mm thick) and progressively softer towards the center of the wall. This particular structure might have caused a complex loading condition to the pipe wall material such that yielding of the soft material become possible, particularly when crack has propagated into the soft region of the pipe wall. As a result, corrosion attack may take place in a direction consistent with the maximum shear stress, and cracking preceded by the concurrent interaction between corrosion attack and mechanical damage.
Geotechnical Assessments for Trenchless Water Crossings in Alberta
Authors: Heinz Heinrich K. , Moore Trempess , Cullum-Kenyon Simon
Published: December 2008

The use of trenchless methods for pipeline water crossings in the Province of Alberta has grown significantly during the past decade, primarily as a result of increasingly strict water protection regulations. Because the feasibility of using a trenchless method is dependent on subsurface conditions, a geotechnical assessment should be performed during the planning stages. The results of this assessment are used in the selection of the most appropriate crossing method, and to assess the risk of encountering difficulties during construction. A discussion of the current state of practice for geotechnical investigations of trenchless projects in Alberta is initially presented. The importance of a good understanding of the engineering geological framework and associated geological-geotechnical complexities is highlighted. Recommended stages of a geotechnical assessment are described, namely the desk study, the site reconnaissance, and the field exploration, which involves drilling and sampling and geophysical surveys where appropriate. It is described how each stage interacts with, and is dependent on the others. It is noted that because the cost of a field drilling and sampling can be expensive when compared to the construction costs, obtaining as much information as possible during the desk study and field reconnaissance stages is considered to be a cost effective strategy. Drilling and sampling techniques currently used in Alberta are briefly reviewed, including continuous flight and hollow stem augering, wet rotary, and cased down-hole air percussion methods. Emphasis is placed on describing the advantages and limitations of each method. Some of the concepts presented are illustrated through evaluation of a recent case study of a recent major river crossing in Central Alberta.
Drop Weight Tear Testing of High Toughness Pipeline Material
Authors: Halsen Kjell Olav , Heier Espen
Published: December 2008

Drop Weight Tear Testing is a common test method for determining a material’s ability to arrest a propagating crack. This testing method was developed by Battelle Memorial Institute, and is conducted in accordance with standards as API RP 5L3 ‘Recommended Practice for Conducting Drop Weight Tear testing on Line Pipe’ and EN 10274 ‘Metallic Materials - Drop Weight Tear Test’. One problem that has been encountered when performing Drop Weight Tear Testing of high toughness TMCP materials is that the pre-deformed material in the pressed notch is not sufficiently embrittled to ensure initiation of a brittle fracture. According to prevailing standards a brittle initiation is necessary for a valid test result. The material opposite the notched side (impact side) will deform quite considerably and is due to strain hardening expected to loose toughness prior to the actual fracture initiation takes place. Consequently high toughness material may give poor test results. In that respect, DNV initiated a Joint Industry Project called ‘Drop Weight Tear Testing of High Toughness Pipeline Material’, where the main objective was to obtain a better understanding on how the results from the DWTT should be interpreted for high toughness pipeline steels. During the project an extensive amount of Drop Weight Tear tests (DWTT) were performed on relevant modern pipeline steels. The resulting shear ratios were determined according to conventional fracture surface evaluation methods as well as newly developed methods as presented in the literature. The appearance of energy curves for both regular DWTT specimens and specimens with varying back gouge depths was also considered in the investigation and the consistency between the estimated shear ratios and the corresponding measured absorbed energies were thoroughly evaluated. This paper summarizes the results and recommendations obtained in the performed investigations.
The Research of Small Leakage Diagnostic Technique for Liquid Delivery Pipeline
Authors: Wang Zhao-hui , Zhang Lai-bin
Published: December 2008

The small leakage diagnostic method based on negative pressure wave method for Liquid delivery pipeline is introduced, which uses two ram circle-based uninterrupted data acquisition technique, GPS synchronizing technique, and can diagnose the small leakage effectively, orientate the leakage point precisely. The experiment has shown that the diagnostic system based on these techniques has high stability, reliability and diagnostic precision.
Optimizing the Steady Operation of an Double Oil Pipeline System by Decompostion Method
Authors: Wu Changchun , Shao Guotai
Published: December 2008

As a main channel for long distance transportation of Daqing crude oil, Daqing-Tieling oil pipeline system consists of two pipelines in parallel. With its capacity of 45 million tons per year, the system is the largest oil pipeline system in China and plays an important role in the petroleum industry and national economy of China. Due to the complicated interconnection between the two pipelines in the system, the optimization of steady operation of the system is much more difficult than a single pipeline so that it can be considered as an optimization problem on large scale system. Besides the interconnection of the two pipelines, because of high pour point of Daqing crude oil, another difficulty to solve the problem comes from the fact that the two pipelines are hot oil pipeline, of which the heating-pumping stations are equipped with some heaters to heat the crude oil so as to improve its flow ability. For the optimization problem, the basic decision variables can be divided into two types, the discharge temperature of each heating-pumping station and the 0–1 variable which assigns a pump online or offline, and they are dependent to each other. Under certain conditions, the problem can be decomposed into two relatively independent sub-problems, one being the optimization of the oil temperatures in the system, another being the optimization of the matching between a pump combination and the all pipe segments of the system. The first sub-problem has been modeled as a nonlinear programming problem with 55 decision variables and more than one hundred constraints. For simplifying the solving process of the sub-problem, it has been further decomposed into a set of sub-problems, again, each of which can be easily solved. The second sub-problem can be modeled as a dynamic programming problem. On the basis of the models and the algorithms proposed for the above-mentioned problem, a software QTOPT has been developed specially for the Daqing-Tieling oil pipeline system, and has been used in evaluating and optimizing the process design of the system. Also the software can be used to optimize the steady operation of the system.
State of Research on Negative Pressure Techniques Applied to Leak Detection in Liquid Pipelines
Authors: Liang Wei , Zhang Lai-bin , Wang Zhao-hui
Published: December 2008

In China, the rarefaction-pressure wave techniques are widely used to diagnose the leakage fault for liquid pipelines. Many leaking propagating assumptions, such as stable single-phased flow hypothesis and none rarefaction wave front hypothesis, are often uncertain in the process of leak detection, which can easily result in some errors. Thus the rarefaction-pressure wave techniques should be integrated with other analytical techniques to compute a more accurate leak location. Additionally, the development trends of rarefaction-pressure wave techniques lie in three aspects. First, rarefaction-pressure wave detection techniques will be integrated with other compatible detection techniques and modern signal processing methods to solve the complex problems encountered in leak detection. Second, studies of rarefaction-pressure wave techniques have advanced to a new stage. The deductions on propagation mechanism of rarefaction-pressure wave have been successfully applied to determine leaks qualitatively. Third, analysis on rarefaction-pressure wave detection techniques will be made from a quantitative point of view. The quantitative data have been used to deduce leak amounts and location. The purpose of this paper is to present the recent achievements in the study of improved rarefaction-pressure wave detection techniques. The rarefaction-pressure wave detection methods, effects of incomplete information conditions, the improvements of rarefaction-pressure wave detection techniques with modified factors and propagation mechanisms are comprehensively investigated. The disfigurements of rarefaction-pressure wave are analyzed. The corresponding methods for resolving such problems as ill diagnostic information and weak amplitude values are put forward. Several methods for stronger small leakage detection ability, higher leakage positioning precision, lower false alarm rates are proposed. The application of rarefaction-pressure wave detection techniques to safety protection of liquid pipelines is also introduced. Finally, the prospect of rarefaction-pressure wave detection techniques is predicted.
Low Cycle Fatigue Strength of X65 Pipeline Girth Welds
Authors: Gotoh Koji , Berge Stig
Published: December 2008

During pipe laying at large water depth using S-lay over a stinger, the pipe may be subjected to reversed plastic strains which could lead to low cycle fatigue failure. X65 pipeline girth welds with wall thickness 22mm were tested in cyclic strain control. Undermatched and overmatched welds were tested. Two types of cyclic strain programs were applied. In the first test series the welds were subjected to a tensile-tensile cyclic strain, simulating pipe going over the stinger, to validate that a pipe going over a stinger would not violate criteria for low cycle fatigue design. In the second test series, the specimens were initially pre-strained to 2% and subsequently fatigue-cycled with a maximum strain of 2% to obtain design criteria for a pipe laying stationary over the stinger for a period of time, subjected to cyclic loads due to waves. The results are presented in terms of Δε–N curves, with proposed design curves for the two types of welds.
Geometric Magnetic and Discriminator Sensor for Smart Pigs
Authors: de C. Lima Vinicius , da Silva Jose´ A. P. , von der Weid Jean Pierre , Camerini Claudio Soligo , de Oliveira Carlos H. F.
Published: December 2008

A result of a research partnership between Catholic University of Rio de Janeiro – PUC-Rio, PETROBRAS and PIPEWAY is presented: The development of an innovative sensor head for high resolution MFL Pigs, the GMD sensor, Geometric Magnetic and Discriminator. This head makes high resolution magnetic pipeline readings using the MFL - Magnetic Flux Leakage technique, with the addition of geometric readings and the outside/inside defects discriminations. This technique makes possible, with only one crown of GMD sensors, the caliper, metal loss and outside/inside discrimination pipeline inspection. Technical aspects of the development, e.g.: the construction details of the sensor, evaluation tests and laboratory results are also presented.
Simplified Method for Profiling Residual Stress Distributions in Plate and Pipe Components
Authors: Lee Hyeong Y. , Nikbin Kamran M. , O’Dowd Noel P.
Published: December 2008

A comprehensive review of through thickness transverse residual stress distributions in a range of as-welded and mechanically bent components made up of a range of steels has been carried out. The geometries consisted of welded pipe butt joints, pipe on plate joints, tubular Y-joints, tubular T-joints and T-plate joints as well as in cold bent tubes and pipes and the collected data cover a range of engineering steels including ferritic, austenitic, C-Mn and Cr-Mo steels. Measured residual stress data, normalised with respect to the parent material yield stress, have shown a good linear correlation versus the normalised crack depth (of upto half thickness) of the region containing the residual stress resulting from the welding or cold-bending operation. The proposed simplified generic residual stress profiling based on a family of linear distribution lines, derived from the mean statistical linear fit of all the analysed data, is shown to provide different levels of conservatism on the calculated stress intensity factors. Whereas the profiles in assessment procedures are fixed and case specific the proposed linear method can be varied by a combination of mean and bending shifts from the mean regression line to produce lower or higher safety factors on stress intensity factor values depending on the level of safety required.
Prediction of the Consequences of Accidental Releases From Liquid Pipelines
Authors: Ronnie S. E.
Published: December 2008

Pipelines are one of the safest ways of transporting hazardous liquids, such as crude oil, gasoline, kerosene and diesel oil. However, few models exist that predict the spread of a liquid over a general topography following accidental release from a pipeline. The methodology presented in this paper allows the route taken by an accidental release of liquid from a pipeline to be predicted. The porosity of the ground is included to enable the extent of spread of the liquid and the proportion of the release reaching an important location, such as a river, to be established. The resulting flow for any given release and topography is determined by interpolation between data contained in a series of tables constructed from simulations using liquid spread software. The methodology has been applied to a release and subsequent fire, which occurred in Bellingham, Washington, in 1999. The extents of the pipeline, which, should a release occur, would result in the spill reaching sensitive areas, have been established. The results obtained are of the correct order of magnitude and are realistic. However, more data on the case studies would be required to quantitatively assess the accuracy of the methodology.
Risk Assessment of Petroleum Transportation Pipeline in Some Turkish Oil Fields
Authors: Ogutcu Gokcen , Akin Serhat
Published: December 2008

This study concentrates on risk factors in oil field pipeline systems and covers identification of failure rate and reasons of failure comparison of the failure data, which are collected from oilfield pipeline systems located in South East Turkey. There are many methods and techniques to reduce or eliminate risk factors in pipeline systems. In this study, quantitative risk assessment method, which depends on statistical calculations, was applied. Monte Carlo Simulation was used to assess the risk in the system. This study focuses on identification of relationship between all parameters. History matching frequency, identification of critical factors, probability of density function have been estimated and calculated. The most significant failures are identified as corrosion, third party damage, mechanical failure, operational failure, weather effect and sabotage.
Experimental Study of Thickness and Fatigue Precracking Influence on the CTOA Toughness Values of High Grade Gas Pipeline Steel
Authors: Hashemi Sayyed H. , Howard Ian C. , Yates John R. , Andrews Robert M. , Edwards Alan M.
Published: December 2008

Recent experimental and computational studies have revealed that the CTOA fracture criterion has the potential to assess steady state ductile rupture resistance during large amounts of crack growth. One of the major difficulties currently limiting the more extensive use of CTOA is its practical estimation either on a real structure or in a laboratory scale test. The authors have recently developed a novel test technique for direct measurement of CTOA. It is a single CTOA test (SCT) method using a modified double cantilever beam (DCB) specimen. Photographic and video techniques are used to register the progression of the crack tip in real time on the faces of the DCB. The CTOA profile is estimated from the uniform variations of the slope of a reference fine mesh scored on the surface of the specimen. Its value is representative of the material CTOA. So far the method has been successfully tested on gas pipeline steels of grade API X80 and X100 and 6000 series aluminium alloy. In all tests, it generated large amounts of highly consistent CTOA data, even from a single test specimen. This paper describes recent results from the CTOA testing of X100 steel specimens with different ligament thicknesses in the range of 8 to 12 mm, equivalent to 42 to 63% of the original pipe wall thickness. In total 18 sets of CTOA test data were obtained from opposite sides of fractured specimens. Analysis of these showed that the CTOA values were thickness independent in the examined range. An average CTOA value of 8.5° was found for X100 steel in the steady state crack propagation phase. The development of slant fracture associated with the steady CTOA region was completed after an average crack growth of 1.3–2.7 times the specimen ligament thickness. The fatigue precracking resulted in a 10–23% drop in the initiation load depending on the gauge thickness of the specimen and the initial crack length.
Vertical Pipe Inspection Using Swarm of Independent Robots
Authors: Pellizzari Daniela , Ramirez-Serrano Alejandro , Pettinaro Giovanni C.
Published: December 2008

The work reported here describes a solution to the problem of inside vertical pipe inspection using a swarm of independent mobile robots. The proposed solution assumes the pipe diameter to be known, however, it does not make any further assumptions concerning the height to be climbed/inspected or the material and characteristics of the pipe. The robots considered are fully independent/intelligent/autonomous units and are able to connect to each other firmly as needed so as to form diverse rigid configuration structures (swarms). By exploiting the rigidity of such connections, the robots composing a swarm climb the inner vertical walls of a pipe simply by exerting together a force towards the pipe walls and by jointly moving forward at the same speed (as a team). During the joint motion, the robots are able to monitor their peers as well as the integrity of the surface by using a small CCD camera mounted on top of each robot. If one of them detects an unusual condition, it lits up and continues its motion waiting for all the other to acknowledge the situation by litting up them-selves. When this happens, they all jointly stop preventing in this way a sudden break of the force exerted on the walls and a consequent collapse of the swarm structure. In this way diverse pipe configurations can be effectively inspected.
Development of a New Dual Powder Coating
Authors: Edmondson Stephen J. , Waslen Doug W. , Fogg Graham
Published: December 2008

This paper discusses the development of a new dual powder system designed to prevent damage during pipeline transportation and installation and thus achieve a lower net installed cost. The development involved the formulation of two new fusion bond epoxies (FBEs), a base layer FBE that gives improved resistance to disbondment, and an improved damage resistant topcoat. This new system gives exceptional resistance to damage at a lower total film thickness than the original dual powder system. Extensive laboratory testing will be presented which has demonstrated the ability of the system to resist disbondment at elevated temperatures and to provide enhanced resistance to mechanical damage. Details of the challenges associated with the development will be presented.
Investigation on Potential SCC in Gas Transmission Pipeline in China
Authors: Shuai Jian , Yang Zupei , Mei Yunxin
Published: December 2008

The safety and reliability of pipelines will bring a huge challenge upon the construction of a large number of gas transmission pipelines in China. It has been known that two types of SCC (near-neutral SCC and high-pH SCC) commonly occur on the pipelines. Thus, there is an urgent need to investigate the potential SCC on the pipelines in China. In this paper, we report the SCC investigation on three gas transmission pipelines (one pipeline over 30 years old and two newly-constructed pipelines) in western and middle China. (i) For the old pipeline, we reviewed the failure cases and corrosion investigation collected in past years and excavated dozens of field sites to detect the anti-corrosion coating and cathode protection, and analyzed the reasons why SCC didn’t occur in the old pipeline yet. (ii) For these three pipelines, we evaluated the SCC sensitivity of line pipe steels in typical soil environment by using slow strain rate tests and other experiments. (iii) For pipelines in western China, we also analyzed the soil environment and operation pressure fluctuation. Based on the analysis, we summarized some conditions that are prone to SCC and present measurements of SCC prevention. Our investigation will build a solid foundation for the SCC prevention on all gas pipelines in the near future.
Defect Characteristic Prediction of Pipeline by Means of Wavelet Neural Network Based on the Hierarchical Clustering Algorithm
Authors: Wei Maoan , Jin Shijiu , Wang Likun , Zhou Yan
Published: December 2008

It is very difficult to generalize the relationship between MFL signal and the defect geometric parameters of the pipeline because the relationship is nonlinear. Many applications of wavelet neural network on this field show that the defect geometric parameters can be obtained with this method to some extent. However, the initial centers have great influence on performance of the network. Hierarchical clustering algorithm is proposed in this paper and applied to classification of defect samples, centers selection and calculation of basis function width. With this algorithm, clusters similarity is computed to create tree structure and the perfect clustering is obtained. The sample set created from finite element defect simulation are used to train and validate the efficiency and reliability of the network based on hierarchical clustering algorithm. The experiment shows that the training speed and the prediction precision of the network can be improved simulataneously.
Managing Climate Change Risk: Emerging Financial Sector Expectations
Authors: Williams Richard
Published: December 2008

During the third quarter of 2003, Eos Research & Consulting Ltd. conducted a two part study examining emerging standards for how energy companies manage climate change related risks. The first part was a survey of financial institutions in Canada, U.S. and internationally to determine their expectations for how energy companies should approach risks associated with climate change and policies to address it. In a parallel effort, using criteria which were based in part on the results from the financial sector survey, eleven leading energy companies were compared in a benchmarking study which examined response to climate change risks to date. The result provided two facets of the emerging standard for climate change risk management in the energy sector. This paper examines the results of the financial sector survey, drawing conclusions about the role that sector will play in setting expectations for how energy companies respond to climate change risks in the foreseeable future.
Transient Leak Detection in Crude Oil Pipelines
Authors: Beushausen Rainer , Tornow Stefan , Borchers Harald , Murphy Keefe , Zhang Jun
Published: December 2008

This paper addresses the specific issues of transient leak detection in crude oil pipelines. When a leak occurs immediately after pumps are switched on or off, the pressure wave generated by the transients dominates the pressure wave that results from the leak. Traditional methods have failed to detect such leaks. Over the years, NWO has developed and implemented various leak detection systems both in-house and by commercial vendors. These systems work effectively under steady-state conditions but they are not able to detect leaks during transients. As it is likely for a leak to develop during transients, NWO has decided to have the ATMOS Pipe statistical leak detection system installed on their pipelines. This paper describes the application of this statistical system to two crude oil pipeline systems. After addressing the main difficulties of transient leaks, the field results will be presented for both steady-state and transient conditions.
Quality assurance evaluation of delivery of respiratory‐gated treatments
Authors: Cardenas Alex , Fontenot Jonas , Forster Kenneth M. , Stevens Craig W. , Starkschall George
Published: December 2008

We describe a method for evaluating the quality of respiratory‐gated radiation delivery using a commercially available device. During irradiation, gating traces for one field for each treatment were extracted from the system for each of 14 patients. The data were then transferred to a spreadsheet. Software was developed to evaluate the following parameters: duty cycle, amplitude of fiducial motion, fraction of amplitude of motion during gated delivery, and respiratory cycle time. Criteria were established for acceptability of gating traces. In our sample, over 85% of the traces indicated acceptability. An example of results for one patient extracted from analyzed gating traces is as follows: mean duty cycle, 57%; average amplitude of motion, 0.89 cm; average fraction of motion during gated delivery, 0.45; mean respiratory cycle time, 4.5 s. This technique can be used to evaluate delivery of respiratory‐gated radiation therapy for quality assurance purposes and to assess various techniques for improving delivery of gated therapy. A hard copy of the gating traces can be used to document gated treatment delivery for potential billing of the gated delivery process.

PACS numbers: 87.53‐j, 87.53.Tf
Improving a scissor‐action couch for conformal arc radiotherapy and radiosurgery
Authors: Li Kaile , Yu Cedric X. , Ma Lijun
Published: December 2008

We have developed a method to improve the setup accuracy of a Varian Clinac 6/100 couch for delivering conformal arc therapy using a tertiary micro multileaf collimator (MLC) system. Several immobilization devices have been developed to improve the mechanical stability and isocenter alignment of the couch: turn‐knob harnesses, double‐track alignment plates, and a drop‐in rod that attaches the couch to the concrete floor. These add‐on components minimize the intercomponent motion of the couch's scissor elevator, which allows consistent treatment setup. The accuracy of our isocenter couch alignment is an improvement over the above devices, within 1 mm of their accuracy. The couch has been used with over 15 patients and with over 50 modulated conformal arc treatment deliveries at our institution.

PACS numbers: 87.53.Kn, 87.53.Ly, 87.56.Da
HDR brachytherapy combined with 3D conformal versus IMRT in left‐sided breast cancer patients including internal mammary chain: Comparative analysis of dosimetric and technical parameters
Authors: Kinhikar Rajesh Ashok , Deshpande Sudesh Sharad , Mahantshetty Umesh , Sarin Rajiv , Shrivastava Shyam Kishore , Deshpande Deepak Dattatraya
Published: December 2008

Treatment of the internal mammary chain (IMC) with radiation therapy (RT) for patients with breast cancer remains a controversial issue. Different treatment techniques have been proposed, including oblique electrons, electron‐photon combination, and partially wide tangents (PWTs). However, the residual heart dose can remain significant mainly for left‐sided lesions. With PWTs and intensity‐modulated radiotherapy (IMRT), respiratory movement and errors in IMC localization remain a problem. The goal of this paper is to evaluate the impact of IMC brachytherapy (IMCBT) combined with 3D conformal radiotherapy (3DCRT) planning on heart, lung, and contralateral breast doses compared with IMRT. All plans including IMCBT plus 3DCRT were done on PLATO; IMRT plans were generated using the Cadplan‐Helios inverse treatment‐planning software module with the “sliding window” technique. Dose‐volume histograms (DVHs) were calculated for all volumes of interest. Conformity and homogeneity index was also calculated for the planning target volume (PTV). Dose distribution in the surrounding normal tissue was evaluated. The mean conformity of the PTV was found to be 1.06 with IMCBT plus 3DCRT and 1.12 with IMRT. The mean homogeneity (HI95/107) was found to be 1.4 with IMCBT plus 3DCRT and 3.32 with IMRT. Using the IMCBT plus 3DCRT technique, the mean dose to the heart, contralateral breast, ipsilateral lung, and contralateral lung decreased with values of 32%, 6.76%, 20% and 5.52%, respectively, compared with IMRT. This novel technique of IMCBT plus 3DCRT can potentially reduce the dose to the heart and lungs. In addition, it rivals IMRT because of its unique advantages in localization, obviating the need for respiratory gating and maximum sparing of heart and other structures.

PACS numbers: 87.53.Jw, 87.53.Kn, 87.53.Mr, 87.53, 87.53.Tf
Measurement of dose‐area product with GafChromic XR Type R film
Authors: Thomas George , Li Yushan , Chu Robert Y.L. , Cheung John Y. , Maqbool Feroz , Rabe Frank , Burns G. Scott
Published: December 2008

Many of the newer X‐ray machines are equipped with electronic means to provide dose–area product (DAP) information. For machines without that ability, an alternative method is to record radiation on a film that can handle a large amount of cumulative exposure. The use of GafChromic XR Type R film was investigated for this purpose by placing it at the X‐ray tube assembly to record the radiation in interventional radiological procedures. Dose‐area product was determined with a reflective densitometer and then with a flatbed scanner. Precisions were demonstrated to be 5% and 2%, respectively. In a comparison with the machine‐recorded DAP, a regression analysis showed the validity of both techniques for values less than 1200 Gy‐cm2.

PACS numbers: 87.52.Df, 87.66.Cd
Generation of wedge‐shaped dose distributions through dynamic multileaf collimator dose delivery
Authors: Zhu Jingeng
Published: December 2008

A new method of generating wedge‐shaped dose distributions through dynamic multileaf collimator dose delivery rather than computer‐controlled jaw motion is presented. The method starts with the calculation of a wedge‐shaped beam profile for the desired wedge angle. The resultant wedge beam profile is then passed to the intensity‐modulated radiation therapy (IMRT) leaf sequence generation algorithm to create multileaf collimator (MLC) segments for dose delivery. Wedge‐shaped dose distributions are achieved through dynamic MLC dose delivery guided with the generated MLC segments. The method has been tested by generating wedge‐shaped doses for a set of conventional wedge angles (i.e., 15°, 30°, 45°, and 60°). Film dosimetry is used for dose distribution verification. For each dose delivery guided with MLC segments created for the indicated wedge angle, the desired wedge‐shaped dose distributions are observed. It is concluded that the dynamic MLC can be used to implement dynamic wedges in the clinic. This technique is different from the virtual wedge or the dynamic wedge developed for a particular type of LINAC. The same method can be applied to any machine equipped with a MLC. Other advantages are that it can generate a wedge field at an arbitrary orientation as the omni wedge does, and it creates wedged and shaped fields using a MLC only.

PACS number(s): 87.53.Mr.
A 3D digitization system for conventional radiation therapy simulation
Authors: Lu Hsiao‐Ming
Published: December 2008

While the majority of patients receiving external beam radiation therapy treatment are planned by CT simulation, a significant number of them are still planned using conventional simulators for various reasons. The information‐collection process in a conventional simulation is often fragmented and done with primitive tools. For example, in many institutions body contours are still acquired using solder wires and tracing paper, a time‐consuming and error‐prone procedure. We have developed a 3D digitization system to assist the information‐acquisition process at conventional simulations. The system consists of an infrared camera assembly, a wireless digitizer probe, and Windows‐based software. The system can provide 3D coordinates of any points in space accessible by the probe with submillimeter accuracy. It can be used to capture body contours, to record the coordinates of portal points, and to take various measurements for dose calculations as well as for patient setup. The software can display all the captured data together with the planned treatment fields, providing a comprehensive geometric verification of the treatment configuration. The system can also transfer all the information to dose‐planning programs in DICOM‐RT format, providing an integrated information flow from simulation to dose planning.

PACS: 87.53.Vb, 87.53.Xd
Performance of magnetic field‐guided navigation system for interventional neurosurgical and cardiac procedures
Authors: Chu James C.H. , Hsi Wen Chien , Hubbard Lincoln , Zhang Yunkai , Bernard Damian , Reeder Pamela , Lopes Demetrius
Published: December 2008

A hospital‐based magnetic guidance system (MGS) was installed to assist a physician in navigating catheters and guide wires during interventional cardiac and neurosurgical procedures. The objective of this study is to examine the performance of this magnetic field‐guided navigation system. Our results show that the system's radiological imaging components produce images with quality similar to that produced by other modern fluoroscopic devices. The system's magnetic navigation components also deflect the wire and catheter tips toward the intended direction. The physician, however, will have to oversteer the wire or catheter when defining the steering angle during the procedure. The MGS could be clinically useful in device navigation deflection and vessel access.

PACS numbers: 07.55.Db, 07.85.‐m
A technique for reducing patient setup uncertainties by aligning and verifying daily positioning of a moving tumor using implanted fiducials
Authors: Nelson Christopher , Balter Peter , Morice Rodolfo C. , Choi Bum , Kudchadker Rajat J. , Bucci Kara , Chang Joe Y. , Dong Lei , Tucker Susan , Vedam Sastry , Briere Tina , Starkschall George
Published: December 2008

This study aimed to validate and implement a methodology in which fiducials implanted in the periphery of lung tumors can be used to reduce uncertainties in tumor location.

Alignment software that matches marker positions on two‐dimensional (2D) kilovoltage portal images to positions on three‐dimensional (3D) computed tomography data sets was validated using static and moving phantoms. This software also was used to reduce uncertainties in tumor location in a patient with fiducials implanted in the periphery of a lung tumor.

Alignment of fiducial locations in orthogonal projection images with corresponding fiducial locations in 3D data sets can position both static and moving phantoms with an accuracy of 1 mm. In a patient, alignment based on fiducial locations reduced systematic errors in the left–right direction by 3 mm and random errors by 2 mm, and random errors in the superior–inferior direction by 3 mm as measured by anterior–posterior cine images.

Software that matches fiducial markers on 2D and 3D images is effective for aligning both static and moving fiducials before treatment and can be implemented to reduce patient setup uncertainties.

PACS number: 81.40.Wx
Patient dosimetry for total body irradiation using single‐use MOSFET detectors
Authors: Briere Tina Marie , Tailor Ramesh , Tolani Naresh , Prado Karl , Lane Richard , Woo Shiao , Ha Chul , Gillin Michael T. , Beddar A. Sam
Published: December 2008

We studied the usefulness of a new type of solid‐state detector, the OneDose single‐use MOSFET (metal oxide semiconductor field effect transistor) dosimeter, for entrance dose measurements for total body irradiation (TBI). The factory calibration factors supplied by the manufacturer are applicable to conventional radiotherapy beam arrangements and therefore may not be expected to be valid for TBI dosimetry because of the large field sizes and extended source‐to‐axis distances used. OneDose detectors were placed under a 1‐cm thick bolus at the head, neck, and umbilicus of 9 patients undergoing TBI procedures. Thermoluminescent dosimeters (TLDs) were placed beside the detectors. We found that the OneDose readings differed from the TLD readings by 4.6% at the head, 1.7% at the neck, and 3.9% at the umbilicus, with corresponding standard deviations of 3.9%, 2.2%, and 2.7%. For all patient measurements, 95% of the OneDose readings fell within 3. of the TLD readings. Anthropomorphic phantom measurements showed differences of at the neck and midway between the phantom's carina and umbilicus. Our results suggest that these detectors could be used for TBI quality assurance monitoring, although TLDs should remain the standard when critical dose measurements are performed. If OneDose detectors are to be used for TBI, the use of more than one at each location is strongly recommended. Because the detectors are designed for single use, they cannot be individually calibrated. However, to obtain institution‐specific correction factors for better applicability to TBI dosimetry, measurements of several detectors taken from a particular lot could also be obtained in phantom with the TBI geometry configurations used for patient treatment.

PACS numbers: 87.53.Bn, 85.30.Tv, 87.55.‐x
Electron beam therapy at extended source‐to‐surface distance: a Monte Carlo investigation
Authors: O'Shea Tuathan P. , Foley Mark J. , Rajasekar David , Downes Patrick A. , van der Putten Wil , Moore Margaret , Shearer Andrew
Published: December 2008

Electron‐beam therapy is used to treat superficial tumors at a standard 100 cm source‐to‐surface distance (SSD). However, certain clinical situations require the use of an extended SSD. In the present study, Monte Carlo methods were used to investigate clinical electron beams, at standard and non‐standard SSDs, from a Siemens Oncor Avant Garde (Siemens Healthcare, Erlangen, Germany) linear accelerator (LINAC). The LINAC treatment head was modeled in BEAMnrc for electron fields 5 cm in diameter and , , and ; for 6 MeV, 9 MeV, and 12 MeV; and for 100 cm, 110 cm, and 120 cm SSD. The DOSXYZnrc code was used to calculate extended SSD factors and dose contributions from various parts of the treatment head.

The main effects of extended SSD on water phantom dose distributions were verified by Monte Carlo methods. Monte Carlo–calculated and measured extended SSD factors showed an average difference of . For the field 5 cm in diameter, the relative output at extended SSD declined more rapidly than it did for the larger fields. An investigation of output contributions showed this decline was mainly a result of a rapid loss of scatter dose reaching the point from the lower scrapers of the electron applicator. The field 5 cm in diameter showed a reduction in dose contributions; the larger fields generally showed an increased contribution from the scrapers with increase in SSD. Angular distributions of applicator‐scattered electrons have shown a large number of acute‐angle electron tracks contributing to the output for larger field sizes, explaining the shallow output reduction.

PACS numbers: 87.53.Wz, 87.53.Vb, 87.53.Hv
An investigation of temporal resolution parameters in cine‐mode four‐dimensional computed tomography acquisition
Authors: Mutaf Yildirim D. , Brinkmann Debra H.
Published: December 2008

The accuracy of four‐dimensional computed tomography (4DCT) imaging depends on temporal characteristics of the acquisition protocol—for example, the temporal spacing of the reconstructed images (also known as cine duration between images) and the gantry rotation speed. These parameters affect the temporal resolution of 4DCT images, and a single default acquisition protocol, as commonly used in most clinics, may be suboptimal for a subset of respiratory motion characteristics. It could lead to substantial inaccuracies in target delineation. The aim of the present study was to evaluate the interplay between parameters affecting temporal resolution and the accuracy of the resulting images.

We acquired 4DCT images of cylindrical phantoms under repetitive motion induced by a translation platform. Acquisition settings varied with respect to temporal spacing, gantry rotation speed, and motion period of the phantoms. Reconstructed images were sorted into 10 phase bins and were compared to static phantom images acquired at corresponding positions of the respiration phase. Acquisitions with different temporal spacing did not play a significant role in the amount of motion observed in full‐cycle maximum intensity projection images. Target delineation accuracy at end‐of‐inhalation phase was observed to be constant up to a threshold in the value of the reconstruction interval, beyond which it varied arbitrarily. This threshold was found to be correlated with the number of phase bins and the motion period. No observable variations were noted with images from the end of exhalation when temporal spacing was varied. Target delineation accuracy was observed to be enhanced in acquisitions using faster gantry rotation speeds. An evaluation of the acquisition parameters needs to be performed depending on the period of the motion and limiting factors such as the availability of acquisition settings, X‐ray tube workload, image storage, and processing power.

PACS numbers: 87.53.Xd, 87.57.‐s, 87.57.Gg, 87.59.Fm