bluuebunny/crossref_metadata_2025 huggingface dataset:
In Practice: Defining Mediator Knowledge and Skills
Authors: Herrman Margaret S. , Jerry Gale Nancy Hollett , Foster Mark
Published: July 2007

A two‐year collaboration among researchers, practitioners, and advisers from the major national organizations of mediators produced a job analysis relevant to mediators involved in interpersonal disputes (i.e., divorce, community, formal parent‐child mediation, etc.). One byproduct of the job analysis is an extensive list of the knowledge areas and skills important to effective job performance. This essay defines the knowledge and skill areas that emerged from the analysis.
Dealcrafting: The Substance of Three‐Dimensional Negotiations
Authors: Lax David A. , Sebenius James K.
Published: July 2007

Much of our understanding of negotiation focuses on the process at the table involving a complicated set of interpersonal dynamics and strategies, or a “one‐dimensional” approach to the subject. Conceptually independent of one‐dimensional process factors is a second dimension of negotiation, “dealcrafting,” which focuses on substance in the effort to create joint value. A third dimension of negotiation, involving entrepreneurial moves “away from the table,” includes the first two dimensions but offers ways in which negotiators can change the game advantageously. Within this overall 3‐D perspective, the second dimension (dealcrafting) calls for a relentless focus on creating maximum value and an equally relentless focus on differences as means to create joint gains. Following their description of the overall 3‐D approach, the authors use numerous case examples to illustrate how principles of dealcrafting work in practice.
Supporting Accountability in the Field of Mediation
Authors: Herrman Margaret S. , Hollett Nancy , Eaker Dawn Goettler , Gale Jerry , Foster Mark
Published: July 2007

Over time, many fields of work—law, medicine, and teaching—matured from informal bodies of knowledge and skills, passed from one practitioner to another, into professions. In the process each began enumerating and affirming their intellectual and practical roots. Each also began testing practitioners to insure comprehension of relevant knowledge and an ability to demonstrate relevant skills. Family mediators in Canada have moved in this direction. In the United States, people who mediate interpersonal disputes also feel pressured to take additional steps to assure the quality of our work. This article summarizes what mediation organizations in the United States have done and could do to vouch for work in our field. But, taking additional steps calls for a clearer understanding of what a mediator should know and what they are expected to do. These two critical pieces of information remain nebulous. So, this article goes beyond describing ways of insuring accountability by also describing a recently completed job analysis, a tool frequently used in other fields of work to describe the skills and knowledge relevant to a particular job.
The Intersection of Religion, Race, Class, and Ethnicity in Community Conflict
Authors: Nolan‐Haley Jacqueline
Published: July 2007

This brief essay explores some ways of defining what we need to know — but don't — about conflict within and between communities where there are strong identity differences based on religion, culture, gender, and race. Its particular focus is on the role that religion and religious leaders play in attempting to resolve identity‐based conflict.
Perspectives on Managing Intractable Conflict
Authors: Eliasson Jan
Published: July 2007

The author, a Swedish diplomat with extensive experience in peace‐keeping initiatives of the United Nations, focuses on two questions that are prominent in the management of intractable international conflict: (1) the interplay between short‐term and long‐term interventions; and (2) the growing “tools” that are available to mediators and other peacemakers, and how to judge their effectiveness. This brief essay is an adaptation of the autor's informal remarks at the March, 2002 Hewlett Centers meeting in New York City.
A Framework for Understanding Consensus‐Building Initiation
Authors: Poitras Jean , Bowen Robert E.
Published: July 2007

The potential of cosnensus building is dependent upon overcoming difficulties associated with the challenges in getting parties to the table. This article builds a framework for understanding the factors and vaiables most fundamentally involved in the initial of consensus‐building efforts. Nine factors involved at the beginning of a consensus‐building process are identified and outlined. The framework is structured on three major functions of the initiation phase: the definition of the porblem, the stucture of negotiation, and the motivation to participate.
Service‐Learning and Negotiation: Engaging Students in Real‐World Projects That Make a Difference
Authors: Kenworthy‐U'Ren Amy
Published: July 2007

In recent years, the normative approach to teaching negotiation (i.e., using a combination of lectures, case discussions, and simulation exercises) has been under scrutiny. Calls for change stem from the need to increase the “real‐world” applicability of our courses. The author presents service‐learning as a potential pedagogical solution. In doing so, she addresses the fit between service‐learning and recent calls for change in teaching negotiation; discusses issues related to student learning, course design, and faculty member involvement; and provides sample reflections from past service‐learning negotiation students.
Justice, Understanding, and Mediation: When Talk Works, Should We Ask for More?
Authors: D'Alo Grace E.
Published: July 2007

Stimulated by reading Susan Silbey's compelling (1994) profile of Patrick Davis, who mediates special education disputes in Massachusetts, the author discusses the dimensions of these disputes and what it is that parents hope to gain by participating in the process. Recent research suggests that procedural justice is important to them: having the opportunity to voice their concerns, having those concerns acknowledged, and being treated with dignity and respect. These aspects of the process often contribute to personal and emotional goals as well. But parents are also clearly seeking a substantively fair and just result. Substantive justice may sometimes be overlooked as programs develop evaluative tools and other measures to assure quality in mediation. The author also traces the legal history of special education law and points to her research and personal experience as Director of Pennsylvania's special education mediation system in reflecting on mediation's potential in this area. She concludes by observing that skilled mediation is people‐centered and has the potential to improve the relationship between the parties; it also can routinely attend to rights‐based concerns.
The Management of Power in Municipalities: Psychoanalytically Informed Negotiation
Authors: Twemlow Stuart W. , Sacco Frank C.
Published: July 2007

The paper takes the view that the psychoanalytic process is a form of negotiation or mutually constructed reality and applies these clinical insights to dispute resolution between two municipal entities: a fire department and a city government. The success of the mediation process is described as depending on the disputants' developing awareness of the impact of power struggles on their own thinking and functioning, and how group dynamics shape perceptions. Operating as a change agent, the mediator needs to be aware of three commonly recurring issues that interfere with the negotiation process: transference/counter‐transference enactments, enactment by fundamental attribution error, self‐serving enactments, and self fulfilling enactments. Vignettes are given to illustrate these conceptual issues.
Reappraisal of a consecutive autopsy series of patients with primary degenerative dementia: Lewy‐related pathology
Authors: OINAS M. , SULKAVA R. , POLVIKOSKI T. , KALIMO H. , PAETAU A.
Published: July 2007

Dementia with Lewy bodies (DLB) is a common but underdiagnosed dementing disorder. Its criteria were defined in 1996, and revised in 2005. DLB is characterised neuropathologically by widely distributed cortical Lewy bodies (LBs), usually associated with Alzheimer‐type pathology. We have re‐evaluated the neuropathology of 55 autopsied patients with clinically diagnosed primary degenerative dementia to determine the frequency of DLB in this cohort, which was originally examined when neither the entity of DLB nor its diagnostic criteria had been defined. We also evaluated how discovery of a new entity affects previous diagnoses. Of the 55 brains, 16 (29%) contained LBs. All 16 originally had a neuropathological diagnosis of Alzheimer's disease (AD). 11 (20%) fulfilled the neuropathological criteria for DLB. Three patients had AD with LBs in the brain stem only, and two patients had LBs in the limbic cortex only. Because the criteria and reliable markers for DLB were not available at the time of the autopsies, the diagnosis of DLB had not been possible. The common co‐occurrence of AD‐type pathology in DLB makes the clinical diagnosis of DLB problematic even today. This study also raises the question of the relative significances of Lewy‐related and AD‐type pathologies to the development of dementia.
Hypoxia‐inducible factor‐1α expression in experimental cirrhosis: correlation with vascular endothelial growth factor expression and angiogenesis
Authors: BOZOVA SEVGI , ELPEK GÜLSÜM ÖZLEM
Published: July 2007

Angiogenesis progresses together with fibrogenesis during chronic liver injury. Hypoxia‐inducible factor‐1α (HIF‐1α), a master regulator of homeostasis, plays a pivotal role in hypoxia‐induced angiogenesis through its regulation of vascular endothelial growth factor (VEGF). The association between hypoxia, angiogenesis and VEGF expression has been demonstrated in experimental cirrhosis. However, expression of HIF‐1α has yet to be reported. The aim of this study was to investigate the significance of HIF‐1α expression during experimental liver fibrosis and the relationships between HIF‐1α expression, VEGF expression and angiogenesis. Cirrhosis was induced in male Wistar rats by intraperitoneal administration of diethyl nitrosamine (DEN) (100 mg/kg, once a week). The serial sections from liver tissues were stained with anti‐HIF‐1α, anti‐VEGF and anti‐CD34 antibodies before being measured by light microscopy. Our results showed that HIF‐1α expression gradually increases according to the severity of fibrosis (p<0.01). Moreover, its expression was found to be correlated with angiogenesis (r=0.916) and VEGF expression (r=0.969). The present study demonstrates that HIF‐1α might have a role in the development of angiogenesis via regulation of VEGF during experimental liver fibrogenesis and suggests that this factor could be a potential target in the manipulation of angiogenesis in chronic inflammatory diseases of the liver.
Nuclear Localization of Endogenous RGK Proteins and Modulation of Cell Shape Remodeling by Regulated Nuclear Transport
Authors: Mahalakshmi Ramasubbu N. , Ng Mei Yong , Guo Ke , Qi Zeng , Hunziker Walter , Béguin Pascal
Published: July 2007

The members of the RGK small GTP‐binding protein family, Kir/Gem, Rad, Rem and Rem2, are multifunctional proteins that regulate voltage‐gated calcium channel activity and cell shape remodeling. Calmodulin (CaM) or CaM 14‐3‐3 are regulators of RGK functions and their association defines the subcellular localization of RGK proteins. Abolition of CaM association results in the accumulation of RGK proteins in the nucleus, whereas 14‐3‐3 binding maintains them in the cytoplasm. Kir/Gem possesses nuclear localization signals (NLS) that mediate nuclear accumulation through an importin α5‐dependent pathway (see Mahalakshmi RN, Nagashima K, Ng MY, Inagaki N, Hunziker W, Béguin P. Nuclear transport of Kir/Gem requires specific signals and importin α5 and is regulated by Calmodulin and predicted service phosphorylations. Traffic 2007; doi: 10.1111/j.1600‐0854.2007.00598.x). Because the extent of nuclear localization depends on the RGK protein and the cell type, the mechanism and regulation of nuclear transport may differ. Here, we extend our analysis to the other RGK members and show that Rem also binds importin α5, whereas Rad associates with importins α3, α5 and β through three conserved NLS. Predicted phosphorylation of a serine residue within the bipartite NLS affects, as observed for Kir/Gem, nuclear accumulation of Rem, but not that of Rad or Rem2. We also identify an additional regulatory phosphorylation for all RGK proteins that prevents binding of 14‐3‐3 and thereby interferes with their cytosolic relocalization by 14‐3‐3. Functionally, nuclear localization of RGK proteins contributes to the suppression of RGK‐mediated cell shape remodeling. Importantly, we show that endogenous RGK proteins are localized predominantly in the nucleus of individual cells of the brain cortex ‘in situ’ as well as in primary hippocampal cells, indicating that transport between the nucleus and their site of action in the cytoplasm (i.e., cytoskeleton, endoplasmic reticulum or plasma membrane) is of physiological relevance for the regulation of RGK protein function.
Membranous Structures Transfer Cell Surface Proteins Across NK Cell Immune Synapses
Authors: Williams Geoffrey S. , Collinson Lucy M. , Brzostek Joanna , Eissmann Philipp , Almeida Catarina R. , McCann Fiona E. , Burshtyn Deborah , Davis Daniel M.
Published: July 2007

Intercellular transfer of cell surface proteins is widespread and facilitates several recently discovered means for immune cell communication. Here, we examined the molecular mechanism for intercellular exchange of the natural killer (NK) cell receptor KIR2DL1 and HLA‐C, prototypical proteins that swap between NK cells and target cells. Transfer was contact dependent and enhanced for cells expressing cognate receptor/ligand pairs but did not depend on KIR2DL1 signaling. To a lesser extent, proteins transferred independent from specific recognition. Intracellular domains of transferred proteins were not exposed to the extracellular environment and transferred proteins were removed by brief exposure to low pH. By fluorescence microscopy, transferred proteins localized to discrete regions on the recipient cell surface. Higher resolution scanning electron micrographs revealed that transferred proteins were located within specific membranous structures. Transmission electron microscopy of the immune synapse revealed that membrane protrusions from one cell interacted with the apposing cell surface within the synaptic cleft. These data, coupled with previous observations, lead us to propose that intercellular protein transfer is mediated by membrane protrusions within and surrounding the immunological synapse.
N‐terminal extension of the yeast IA3 aspartic proteinase inhibitor relaxes the strict intrinsic selectivity
Authors: Winterburn Tim J. , Phylip Lowri H. , Bur Daniel , Wyatt David M. , Berry Colin , Kay John
Published: July 2007

Yeast IA3 aspartic proteinase inhibitor operates through an unprecedented mechanism and exhibits a remarkable specificity for one target enzyme, saccharopepsin. Even aspartic proteinases that are very closely similar to saccharopepsin (e.g. the vacuolar enzyme from Pichia pastoris) are not susceptible to significant inhibition. The Pichia proteinase was selected as the target for initial attempts to engineer IA3 to re‐design the specificity. The IA3 polypeptides from Saccharomyces cerevisiae and Saccharomyces castellii differ considerably in sequence. Alterations made by deletion or exchange of the residues in the C‐terminal segment of these polypeptides had only minor effects. By contrast, extension of each of these wild‐type and chimaeric polypeptides at its N‐terminus by an MK(H)7MQ sequence generated inhibitors that displayed subnanomolar potency towards the Pichia enzyme. This gain‐in‐function was completely reversed upon removal of the extension sequence by exopeptidase trimming. Capture of the potentially positively charged aromatic histidine residues of the extension by remote, negatively charged side‐chains, which were identified in the Pichia enzyme by modelling, may increase the local IA3 concentration and create an anchor that enables the N‐terminal segment residues to be harboured in closer proximity to the enzyme active site, thus promoting their interaction. In saccharopepsin, some of the counterpart residues are different and, consistent with this, the N‐terminal extension of each IA3 polypeptide was without major effect on the potency of interaction with saccharopepsin. In this way, it is possible to convert IA3 polypeptides that display little affinity for the Pichia enzyme into potent inhibitors of this proteinase and thus broaden the target selectivity of this remarkable small protein.
Transient elastography for patients with chronic hepatitis B and C virus infection: Non‐invasive, quantitative assessment of liver fibrosis
Authors: Ogawa Eiichi , Furusyo Norihiro , Toyoda Kazuhiro , Takeoka Hiroaki , Otaguro Shigeru , Hamada Maki , Murata Masayuki , Sawayama Yasunori , Hayashi Jun
Published: July 2007

Aim/Methods: The aim of the present study was to compare the diagnostic performance of transient elastography (FibroScan) with that of serum fibrosis markers and stages of hepatic fibrosis by biopsy in 68 patients with chronic hepatitis B virus (HBV) and in 161 patients with hepatitis C virus (HCV) infection.

Results: The serum levels of hyaluronic acid (r = 0.601) and type IV collagen (r = 0.663) significantly positively associated with the FibroScan values (allP < 0.05). Classified by fibrosis stages, the median values of FibroScan were 3.5 kPa for F0, 6.4 kPa for F1, 9.5 kPa for F2, 11.4 kPa for F3, and 15.4 kPa forF4 in patients with chronic HBV infection, and were 6.3 kPa for F0, 6.7 kPa for F1, 9.1 kPa for F2, 13.7 kPa for F3, and 26.4 kPa for F4 in those with chronic HCV infection. The values were significantly correlated with fibrosis stage for both (HBV,r = 0.559,P = 0.0093, and HCV,r = 0.686,P < 0.0001).

Conclusion: These results suggest that FibroScan is an efficient and simple method for evaluating liver fibrosis in patients with chronic infection, both for HBV and HCV.
Atypical hepatic focal nodular hyperplasia presenting as acute abdomen and misdiagnosed as hepatocellular carcinoma
Authors: Li Tao , Qin Lun‐Xiu , Ji Yuan , Sun Hui‐Chuan , Ye Qing‐Hai , Wang Lu , Pan Qi , Fan Jia , Tang Zhao‐You
Published: July 2007

Focal nodular hyperplasia (FNH) is a rare benign hepatic lesion, which is usually asymptomatic and solitary. Complications such as rupture and bleeding are extremely rare and only five cases have existed since 1975. We report a case of a 26‐year‐old woman with spontaneous rupture and hemorrhage of huge FNH presenting as acute abdomen. Different to previously recorded cases, this case was concomitant with multiple hepatic adenomas, which was misdiagnosed as rupture of hepatocellular carcinoma (HCC) with multiple intrahepatic spreading in another hospital. Our case highlights thepossible association between the size of FNH and the risk of rupture, and emphasizes the need to consider this in making treatment decisions. Although a conservative approach for asymptomatic FNH is well established, the potential for surgical intervention should always be considered, especially for large FNH. We recommend surgical resection of large FNH (>5 cm), symptomatic or not, rather than observation.
A Theoretical Study of the In Vivo Mechanical Properties of Angiosperm Roots: Constitutive Theories and Methods of Parameter Estimation
Authors: Sadovsky Alexander V. , Baldi Pierre F. , Wan Frederic Y.-M.
Published: July 2007

To investigate the constitutive relation of a plant tissue regarded as a deformable continuum, stress and strain must be determined experimentally for the same configurations. Such experiments are hindered by the inherent theoretical complexity of continuum mechanics, and by the technical difficulties of effecting external stress loads or body forces on the tissue without invasion, especially on a small scale. An understanding of appropriate mechanical problems and their solutions can help the experimentalist overcome these difficulties to a certain extent. Based on recent work on fiber-reinforced material, we formulate a constitutive theory for the root of different angiosperm species and suggest a set of loading conditions to determine the parameter values in a specific tissue sample. The loading conditions are formulated with a view toward experimental realization in vivo or with minimal invasion. For each loading condition, we formulate the corresponding mechanical problem and show how to obtain the values of the elastic parameters from known solutions. This framework can be used to analyze the interplay between mechanical and metabolic behavior in plants and to study the elastodynamics of plant tissues.
Tracking lung tissue motion and expansion/compression with inverse consistent image registration and spirometry
Authors: Christensen Gary E. , Song Joo Hyun , Lu Wei , El Naqa Issam , Low Daniel A.
Published: July 2007

Breathing motion is one of the major limiting factors for reducing dose and irradiation of normal tissue for conventional conformal radiotherapy. This paper describes a relationship between tracking lung motion using spirometry data and image registration of consecutive CT image volumes collected from a multislice CT scanner over multiple breathing periods. Temporal CT sequences from 5 individuals were analyzed in this study. The couch was moved from 11 to 14 different positions to image the entire lung. At each couch position, 15 image volumes were collected over approximately 3 breathing periods. It is assumed that the expansion and contraction of lung tissue can be modeled as an elastic material. Furthermore, it is assumed that the deformation of the lung is small over one‐fifth of a breathing period and therefore the motion of the lung can be adequately modeled using a small deformation linear elastic model. The small deformation inverse consistent linear elastic image registration algorithm is therefore well suited for this problem and was used to register consecutive image scans. The pointwise expansion and compression of lung tissue was measured by computing the Jacobian of the transformations used to register the images. The logarithm of the Jacobian was computed so that expansion and compression of the lung were scaled equally. The log‐Jacobian was computed at each voxel in the volume to produce a map of the local expansion and compression of the lung during the breathing period. These log‐Jacobian images demonstrate that the lung does not expand uniformly during the breathing period, but rather expands and contracts locally at different rates during inhalation and exhalation. The log‐Jacobian numbers were averaged over a cross section of the lung to produce an estimate of the average expansion or compression from one time point to the next and compared to the air flow rate measured by spirometry. In four out of five individuals, the average log‐Jacobian value and the air flow rate correlated well ( on average for the entire lung). The correlation for the fifth individual was not as good ( on average for the entire lung) and can be explained by the small variation in tidal volume for this individual. The correlation of the average log‐Jacobian value and the air flow rate for images near the diaphragm correlated well in all five individuals ( on average). These preliminary results indicate a strong correlation between the expansion/compression of the lung measured by image registration and the air flow rate measured by spirometry. Predicting the location, motion, and compression/expansion of the tumor and normal tissue using image registration and spirometry could have many important benefits for radiotherapy treatment. These benefits include reducing radiation dose to normal tissue, maximizing dose to the tumor, improving patient care, reducing treatment cost, and increasing patient throughput.
Cluster computing software for GATE simulations
Authors: De Beenhouwer Jan , Staelens Steven , Kruecker Dirk , Ferrer Ludovic , D'Asseler Yves , Lemahieu Ignace , Rannou Fernando R.
Published: July 2007

Geometry and tracking (GEANT4) is a Monte Carlo package designed for high energy physics experiments. It is used as the basis layer for Monte Carlo simulations of nuclear medicine acquisition systems in GEANT4 Application for Tomographic Emission (GATE). GATE allows the user to realistically model experiments using accurate physics models and time synchronization for detector movement through a script language contained in a macro file. The downside of this high accuracy is long computation time. This paper describes a platform independent computing approach for running GATE simulations on a cluster of computers in order to reduce the overall simulation time. Our software automatically creates fully resolved, nonparametrized macros accompanied with an on‐the‐fly generated cluster specific submit file used to launch the simulations. The scalability of GATE simulations on a cluster is investigated for two imaging modalities, positron emission tomography (PET) and single photon emission computed tomography (SPECT). Due to a higher sensitivity, PET simulations are characterized by relatively high data output rates that create rather large output files. SPECT simulations, on the other hand, have lower data output rates but require a long collimator setup time. Both of these characteristics hamper scalability as a function of the number of CPUs. The scalability of PET simulations is improved here by the development of a fast output merger. The scalability of SPECT simulations is improved by greatly reducing the collimator setup time. Accordingly, these two new developments result in higher scalability for both PET and SPECT simulations and reduce the computation time to more practical values.
Evaluating computer‐aided detection algorithms
Authors: Jun Yoon Hong , Zheng Bin , Sahiner Berkman , Chakraborty Dev P.
Published: July 2007

Computer‐aided detection (CAD) has been attracting extensive research interest during the last two decades. It is recognized that the full potential of CAD can only be realized by improving the performance and robustness of CAD algorithms and this requires good evaluation methodology that would permit CAD designers to optimize their algorithms. Free‐response receiver operating characteristic (FROC) curves are widely used to assess CAD performance, however, evaluation rarely proceeds beyond determination of lesion localization fraction (sensitivity) at an arbitrarily selected value of nonlesion localizations (false marks) per image. This work describes a FROC curve fitting procedure that uses a recent model of visual search that serves as a framework for the free‐response task. A maximum likelihood procedure for estimating the parameters of the model from free‐response data and fitting CAD generated FROC curves was implemented. Procedures were implemented to estimate two figures of merit and associated statistics such as 95% confidence intervals and goodness of fit. One of the figures of merit does not require the arbitrary specification of an operating point at which to evaluate CAD performance. For comparison a related method termed initial detection and candidate analysis was also implemented that is applicable when all suspicious regions are reported. The two methods were tested on seven mammography CAD data sets and both yielded good to excellent fits. The search model approach has the advantage that it can potentially be applied to radiologist generated free‐response data where not all suspicious regions are reported, only the ones that are deemed sufficiently suspicious to warrant clinical follow‐up. This work represents the first practical application of the search model to an important evaluation problem in diagnostic radiology. Software based on this work is expected to benefit CAD developers working in diverse areas of medical imaging.
Correction of CT artifacts and its influence on Monte Carlo dose calculations
Authors: Bazalova Magdalena , Beaulieu Luc , Palefsky Steven , Verhaegen Frank
Published: July 2007

Computed tomography (CT) images of patients having metallic implants or dental fillings exhibit severe streaking artifacts. These artifacts may disallow tumor and organ delineation and compromise dose calculation outcomes in radiotherapy. We used a sinogram interpolation metal streaking artifact correction algorithm on several phantoms of exact‐known compositions and on a prostate patient with two hip prostheses. We compared original CT images and artifact‐corrected images of both. To evaluate the effect of the artifact correction on dose calculations, we performed Monte Carlo dose calculation in the EGSnrc/DOSXYZnrc code. For the phantoms, we performed calculations in the exact geometry, in the original CT geometry and in the artifact‐corrected geometry for photon and electron beams. The maximum errors in photon beam dose calculation were found to exceed 25% in original CT images when the standard DOSXYZnrc/CTCREATE calibration is used but less than 2% in artifact‐corrected images when an extended calibration is used. The extended calibration includes an extra calibration point for a metal. The patient dose volume histograms of a hypothetical target irradiated by five photon beams in a hypothetical treatment differ significantly in the original CT geometry and in the artifact‐corrected geometry. This was found to be mostly due to miss‐assignment of tissue voxels to air due to metal artifacts. We also developed a simple Monte Carlo model for a CT scanner and we simulated the contribution of scatter and beam hardening to metal streaking artifacts. We found that whereas beam hardening has a minor effect on metal artifacts, scatter is an important cause of these artifacts.
TG‐69: Radiographic film for megavoltage beam dosimetry
Authors: Pai Sujatha , Das Indra J. , Dempsey James F. , Lam Kwok L. , LoSasso Thomas J. , Olch Arthur J. , Palta Jatinder R. , Reinstein Lawrence E. , Ritt Dan , Wilcox Ellen E.
Published: July 2007

TG‐69 is a task group report of the AAPM on the use of radiographic film for dosimetry. Radiographic films have been used for radiation dosimetry since the discovery of x‐rays and have become an integral part of dose verification for both routine quality assurance and for complex treatments such as soft wedges (dynamic and virtual), intensity modulated radiation therapy (IMRT), image guided radiation therapy (IGRT), and small field dosimetry like stereotactic radiosurgery. Film is convenient to use, spatially accurate, and provides a permanent record of the integrated two dimensional dose distributions. However, there are several challenges to obtaining high quality dosimetric results with film, namely, the dependence of optical density on photon energy, field size, depth, film batch sensitivity differences, film orientation, processing conditions, and scanner performance. Prior to the clinical implementation of a film dosimetry program, the film, processor, and scanner need to be tested to characterize them with respect to these variables. Also, the physicist must understand the basic characteristics of all components of film dosimetry systems. The primary mission of this task group report is to provide guidelines for film selection, irradiation, processing, scanning, and interpretation to allow the physicist to accurately and precisely measure dose with film. Additionally, we present the basic principles and characteristics of film, processors, and scanners. Procedural recommendations are made for each of the steps required for film dosimetry and guidance is given regarding expected levels of accuracy. Finally, some clinical applications of film dosimetry are discussed.
Characterization of a fiber‐optic‐coupled radioluminescent detector for application in the mammography energy range
Authors: Benevides Luis A. , Huston Alan L. , Justus Brian L. , Falkenstein Paul , Brateman Libby F. , Hintenlang David E.
Published: July 2007

Fiber‐optic‐coupled radioluminescent (FOC) dosimeters are members of a new family of dosimeters that are finding increased clinical applications. This study provides the first characterization of a Cu doped quartz FOC dosimeter at diagnostic energies, specifically across the range of x‐ray energies and intensities used in mammographies. We characterize the calibration factors, linearity, angular dependence, and reproducibility of the FOC dosimeters. The sensitive element of each dosimeter was coupled to a photon counting photomultiplier module via long optical fibers. A computer controlled interface permitted real‐time monitoring of the dosimeter output and rapid data acquisition. The axial‐angular responses for all dosimeter models show nearly uniform response without any marked decrease in sensitivity. However, the normal‐to‐axial angular response showed a marked decrease in sensitivity of about and . In most clinical applications, appropriate dosimeter positioning can minimize the contributions of the varying normal‐to‐axial response. The FOC dosimeters having the greatest sensitive length provided the greatest sensitivity, with greatest to lowest sensitivity observed for 4.0, 1.9, 1.6, and length sensitive elements. The average sensitivity of the dosimeters varies linearly with sensitive volume and as a function of tube potential and target/filter combinations, generally exhibiting an increased sensitivity for higher energies. The dosimeter sensitivity as a function of tube potential had an average increase of for dosimeter models and three target‐filter combinations tested (, , and ) over a range of . All dosimeter models exhibited a linear response to exposure for all target‐filter combinations, tube potentials, and tube current‐time product stations evaluated and demonstrated reproducibility within 2%. All of the dosimeters examined in this study provided a response adequate for the accurate measurement of doses in clinical mammography applications.
Optically stimulated luminescence (OSL) of carbon‐doped aluminum oxide for film dosimetry in radiotherapy
Authors: Schembri V. , Heijmen B. J. M.
Published: July 2007

Introduction and Purpose: Conventional x‐ray films and radiochromic films have inherent challenges for high precision radiotherapy dosimetry. Here we have investigated basic characteristics of optically stimulated luminescence (OSL) of irradiated films containing carbon‐doped aluminum oxide for dosimetry in therapeutic photon and electron beams. Materials and Methods: The OSL films consist of a polystyrene sheet, with a top layer of a mixture of single crystals of , ground into a powder, and a polyester base. The total thickness of the films is . Measurements have been performed in a water equivalent phantom, using 4, 6, 10, and photon beams, and electron beams. The studies include assessment of the film response (acquired OSL signal/delivered dose) on delivered dose (linearity), dose rate , beam quality, field size and depth (, ranges , ). Doses have been derived from ionization chamber measurements. OSL films have also been compared with conventional x‐ray and GafChromic films for dosimetry outside the high dose area, with a high proportion of low dose scattered photons. In total, 787 OSL films have been irradiated. Results: Overall, the OSL response for electron beams was 3.6% lower than for photon beams. Differences between the various electron beam energies were not significant. The 6 and photon beams differed in response by 4%. No response dependencies on dose rate were observed. For the beam, the field size and depth dependencies of the OSL response were within . The observed inter‐film response variation for films irradiated with the same dose varied from 1% to 3.2% , depending on the measurement day. At a depth of , outside the 6 and beams, an over response of 17% was observed. In contrast to GafChromic and conventional x‐ray films, the response of the films is linear in the clinically relevant dose range . Conclusions: Measurement of the OSL signal of irradiated films containing is a promising technique for film dosimetry in radiotherapy with no or small response variations with dose rate, beam quality, field size and depth, and a linear response from .
SU‐DD‐A4‐02: Autosegmentation and Internal Target Volume (ITV) Generation in 4DCT Lung Imaging Using Deformable Image Registration
Authors: Samant S , Xia J , Huang M , Chung H , Liu C , Palta J
Published: July 2007

Purpose: To present a methodology using an improved intensity based deformable image registration algorithm (i.e. Juggler algorithm) for autosegmentation of normal anatomical structures, and algorithm generation of internal target volume (ITV). Method and Materials: The Juggler algorithm separately registers high intensity gradient and low intensity gradient features, and is particularly well suited for maintaining the topological properties of individual structures. Simulated CT imaging consisted of algorithm deformed clinical CT lung imaging. Clinical imaging, acquired from 4DCT, consisted of free breathing (FB) CT and 10 phased CT sets associated with the respiratory cycle. Manual image segmentation of normal structures was carried out on a reference CT (i.e. FB or end of exhalation phase), and the registration map between the reference and target CTs was used to autosegment the structures onto the target CT. This map was also used for automatic generation of ITV based either on “union target volume” (UTV) (i.e. the union of all the separate 3D segmentations), or “probability density function target volume” (PDFTV). Results: Based on known displacement vectors for simulated data, and difference imaging and cross‐correlation values for clinical data, Juggler yielded superior and faster registration compared to current deformable registration algorithms used in radiotherapy: demons, accelerated demons, free‐form deformation. Based on 4DCTs for 5 patients, normal anatomical structures (lung, skin, trachea, esophagus, heart) were automatically autosegmented onto target 3D CT sets within ⩽2mm accuracy based on visual agreement. The UTV computed ITV increased the FB GTV by up to 5mm. Total computation time was <3min (including deformable registration). Conclusions: The proposed methodology using an improved registration algorithm allowed for accurate autosegmentation of normal structures from initial manual segmentations, and the computation of ITV. It provides an effective treatment planning tool for 4DCT. New computer hardware could potentially reduce computation time to <30sec.
SU‐DD‐A4‐03: A Validation Study of Concurrent Multimodality Segmentation
Authors: El Naqa I , Mutic S , Yang D , Khullar D , Deasy J
Published: July 2007

Purpose: The acquisition of multiple images of varied yet complementary information is rapidly becoming the norm in radiotherapy treatment planning. Beside CT data sets, PET and/or MRI or MRS images are also being used to aid in the definition of the target volume (or normal structures) for treatment optimization. We have been developing new methods to integrate available imaging information (anatomical and/or physiological) for concurrent target registration and segmentation. Towards this goal, we have investigated several clustering and active contour methods for simultaneous 2D/3D segmentation/registration of multi‐modality images consisting of combinations of PET, CT, or MRI datasets. In this work, we present a phantom validation study of this approach. Method and Materials: A commercial anthropomorphic head phantom of average human size was used. Targets consisting of plastic spheres and rods were placed throughout the cranium section of the phantom. Tap water was used for CT imaging. For MRI and PET imaging, the water inside the phantom was doped with CuNO3 and 18F‐FDG, respectively. The cold spots spheres were considered as the segmentation targets (four spheres each is 25.4 mm in diameter). The rods were used as landmarks to assist in alignment. A geometric deformable model known as the multi‐valued level set (MVLS) method was applied as our computational vehicle. Results: The MVLS algorithm achieved 90% segmentation accuracy and less than 2% volume error when integrating all of the three modalities. This is contrasted with 74% segmentation accuracy and 4.4% volume error when using CT‐based systems only. Conclusion: We have validated a semi‐automatic method for integrating information from different imaging modalities. Our phantom study demonstrates the feasibility of the proposed image integration approach. This approach could potentially provide radiologists/oncologists with reliable and efficient tools to analyze simultaneously different modality data in different cancer sites.

This work was supported by ACS‐IRG‐58‐010‐50 grant.
SU‐DD‐A3‐01: Dosimetric Evaluation of Daily Rigid and Non‐Rigid Geometric Correction Strategies During On‐Line Image‐Guided Radiation Therapy (IGRT) of Prostate Cancer
Authors: Song W , Wong E , Bauman G , Battista J , Van Dyk J
Published: July 2007

Purpose: To evaluate a geometric image guidance strategy that simultaneously correct for various interfractional rigid and non‐rigid geometric uncertainties in an on‐line environment, using field shape corrections (by modifying MLC). This technique was dosimetrically compared to simpler and more popular image guidance strategies (e.g., linear corrections). Method and Materials: Five prostate cancer patients with daily CT studies were analyzed. All patients were planned with a simplified intensity modulated radiation therapy (SIMAT) technique. A uniform 5‐mm margin was used. The image‐guided geometric correction strategies simulated were (1) translational correction based on daily gross CTV registration (“CTV”), (2) translational correction with daily MU recalculation (“MU‐CTV”), and finally, (3) translational correction with MU re‐calculation and daily MLC corrections to account for prostate deformations (“MU‐MLC”). Deformable image registration was performed on all treatment CT studies for dose accumulation. Generalized equivalent uniform dose (gEUD) index was used for dosimetric comparisons. Results: As expected, some dosimetric differences in the target volume were observed between the three image guidance strategies. For example, up to ± 2% discrepancy in prostate minimum dose were observed among the techniques. Of them, only the “MU‐MLC” technique did not reduce the prostate minimum dose for all patients (i.e., ⩾ 100%). However, the differences were clinically not significant to indicate the preference of one strategy over another, when using a uniform 5‐mm margin size. For the organ‐at‐risks (OARs), large rectum sparing effect (⩽ 5.7 Gy, gEUD) and bladder overdosing effect (⩽ 16 Gy, gEUD) were observed. Conclusion: The results suggest that a linear translational correction (i.e., “CTV”) is adequate to maintain target coverage, for margin sizes at least as large as 5 mm. In addition, due to large fluctuations in OAR volumes, innovative image guidance strategies are needed to minimize dose and maintain consistent sparing during the whole course of radiation therapy.
SU‐FF‐I‐29: Optimizing Radiation Dose and Image Quality in a Multi‐Detector Computed Tomography
Authors: Changkaew P , Pongnapang N
Published: July 2007

Purpose: The study was carried out to find optimal scanning parameters for an MDCT at Ramathibodi hospital. Method and materials: Two types of phantom were employed to assess image quality and standard ionization chamber was used to measure radiation dose. Tube current, slice thickness, pixel size and pitch were varied from routine techniques to evaluate factors affecting image quality (spatial resolution, contrast detectability and image noise) and dose (CTDIair) with aim of optimization. Results: From our study showed that, optimization of radiation dose and image quality could be achieved by proper selection of scanning parameters. Reduction of tube current could be made 22 – 28%, pitch could be doubled from 0.75 to 1.5 (50% dose reduction) in slice thickness less than 7.5 mm without any significant effects on noise and contrast. In examinations that do not require high spatial resolution, larger pixel size could be made and could result in 15 – 17% dose reduction. Conclusions: We concluded from our study that, optimal scanning parameters were 115, 105, 150 and 170 mA for head (above/below posterior fossa) and abdomen (pre‐ and post‐ contrast) protocols, respectively. Slice thickness should be made thinnest possible before the penumbra dose penalty becomes significant. Pitch and pixel size should be selected based on clinical requirements.
SU‐FF‐I‐33: A Technical Solution to Avoid Partial Scan Artifacts in Myocardial Perfusion Imaging Using MDCT
Authors: Primak AN , Dong Y , Dzyubak OP , Jorgensen SM , McCollough CH , Ritman EL
Published: July 2007

Purpose: Partial scan reconstruction methods improve temporal resolution but cause large CT number fluctuations in MDCT systems. The purpose of this study was to assess the feasibility of a new approach to solve this problem. Method and Materials: An anthropomorphic cardiac phantom was scanned on a dual‐source CT scanner (Siemens Definition) using several perfusion modes both with and without ECG‐gating. An additional ECG‐gated acquisition was conducted using the ECG‐signal synchronized with the gantry rotation. The central insert of the cardiac phantom was replaced with a water‐filled tank containing a syringe filled with different iodine solutions (500, 1000, 1500 and 2000 HU). Images were reconstructed using both full (360°, 330 ms) and partial (180° + fan angle, 83 ms) approaches. A ring ROI was placed outside the syringe concentrically with the iodine circle and the mean CT number fluctuations were plotted vs. time. In addition, in‐vivo animal data were acquired using the regular perfusion mode and the mode when the pig's ECG was synchronized with the gantry rotation. A simple x‐ray detector was used to generate a so‐called ‘once‐around’ signal for every gantry rotation. This signal was then modified and used to pace the pig's heart. Results: When the ECG signal was synchronized with the gantry rotation, the same cardiac phase always corresponded to the same x‐ray tube positions and, hence, the same scattering geometry. As a result, the range in the CT number fluctuations was reduced from 20 HU for the regular perfusion mode down to only 3 HU for the synchronized mode. Conclusion: The new approach for myocardial CT perfusion based on synchronizing the ECG signal with the x‐ray tube position significantly improves the quality of the perfusion data by reducing the CT number fluctuations. Conflict of Interest: ANP, OPD, and CHM receive research support from Siemens Medical Solutions.