bluuebunny/crossref_metadata_2025 huggingface dataset:
Semiautomated Detection of Design Errors in 2D Drawings Using 3D Reconstruction
Authors: Li Heng , Cao Yang , Lu Ming
Published: April 2004

Abstract:  This article reports an extension of a previous study on developing a systematic approach to construction rework diagnosis and reduction (Li and Love, 1998; Love, Li, and Mandal, 1998a,b; Love, Smith, and Li, 1998). Existing studies identified that design errors are a primary source (cause) of rework in construction, contributing to 51% of the total failure costs of rework (Li and Love, 1998; Hammarlund and Josephson, 1991). Among these design errors, most of them are attributable to dimensional inconsistencies presented in different sets or sections of engineering drawings (Mondal et al., 2000). In this article, we present a set of virtual reality (VR) enabled 3D reconstruction and collision‐detection techniques to automatically identify and minimize design errors. The 3D reconstruction technique can reconstruct 3D models from three 2D orthographic views. This process helps identify many dimensional inconsistencies within different orthographic views of the same object that give rise to incomplete/irregular 3D models. The 3D reconstruction technique is based on the algorithm developed in Wang et al. (2001) for automatic reconstruction of 3D models from three 2D orthographic views. The 3D models provide input to the collision detection study for identifying inter‐object dimensional inconsistencies. Thus, the integrated application of 3D reconstruction and the collision‐detection techniques is able to identify all the dimensional inconsistencies within and between objects. In this article, the 3D reconstruction technique and the collision detection technique are described through their applications in handling construction drawings.
Pavement Roughness Modeling Using Back‐Propagation Neural Networks
Authors: Choi Jae‐ho , Adams Teresa M. , Bahia Hussain U.
Published: April 2004

Abstract:  Quantifying the relationship between material and construction (M&C) variables and pavement performance is an on‐going important research area. It is, however, realized that deriving such relationships is too complex and too poorly understood to develop using traditional statistical methods. Therefore, this study is focused on the analysis of a data set from the long‐term pavement performance (LTPP) database to quantify the contribution of M&C variables of asphalt concrete on pavement performance (i.e., international roughness indicator) using a back‐propagation neural network (BPNN) algorithm. It was found that by using sensitivity analysis neural network trained with optimal number of epochs could be used effectively for better understanding of the factors controlling overall performance indicators, establishing quantitative functions to weigh the role of such factors, and for use in performance‐related specifications.
The bounded workplace: defence, development and domestication strategies amongst male shiftworkers
Authors: Speakman Sue , Marchington Mick
Published: April 2004

Unlike studies of women, studies of men in paid employment have tended to focus on them purely as workers, trade unionists and breadwinners, rather than on their roles beyond the workplace. This paper addresses this omission by exploring the relationship between paid work and aspects of family life amongst 69 male process workers from three manufacturing companies. It offers qualitative evidence to demonstrate that understanding men's wider domestic/familial roles and responsibilities is integral to analyses of their workplace behaviour. The conclusion from this study is that the boundary between home and work is selectively‐permeable, and the workers took aspects of their domestic life into the workplace whilst seeking to prevent their paid work from intruding on family and domestic life.
Neither fish nor fowl? An assessment of teacher capability procedures
Authors: Earnshaw Jill , Marchington Lorrie , Ritchie Eve , Torrington Derek
Published: April 2004

There has been an increasing focus on the performance of workers through appraisal, performance‐related pay and performance management and this emphasis on measuring performance has extended to the public sector—more specifically, to the teaching profession. This paper uses research commissioned by the DfES to investigate the operation of capability procedures introduced to deal with the perceived problem of incompetent teachers. It revealed that the procedures suffered from a number of defects both in modus operandi and style and there was little evidence that their application resulted in either improved performance or dismissal when satisfactory performance was not achieved.
Cutting through the Silence: A Sociological Construction of Self‐Injury
Authors: Hodgson Sarah
Published: April 2004

This project provides a sociological perspective on self‐injury by assessing whether cutting is a learned behavior and whether practitioners use stigma management techniques. In‐depth interviews via e‐mail with self‐reported self‐injurers indicate cutting is learned from the self or from outside sources. Interviewees also discussed the stigma management techniques they use and whether they choose to disclose their behavior. The findings point to a potential increase in learned cutting from outside sources, and the potential for outside sources to help cutters maintain their behavior by providing each other with support.
Constructing and Deconstructing the Body Malleable through Mother–Daughter Interactions
Authors: Ogle Jennifer Paff , Damhorst Mary Lynn
Published: April 2004

This interpretive study explores how mothers and their adolescent daughters respond to and interact about the body malleable ideology, or cultural discourses that normalize thinness and promote the body as changeable. In‐depth interviews were conducted with 20 mothers and their daughters. Grounded theory analysis revealed two responses to the body malleable ideology—the acceptance or rejection of the body as a malleable object. Participants expressed ambivalence about this ideology and related cultural discourses. Further, through their interactions, mothers and daughters both constructed and deconstructed the ideology of a malleable body. Three patterns of dyadic experience were identified: Pattern A, in which both the mother and daughter accepted the body malleable ideology, Pattern B, in which both the mother and daughter rejected the body malleable ideology, and Pattern C, in which the mother rejected and the daughter accepted the body malleable ideology. In taking an in‐depth look at the cases of three dyads, we explore defining characteristics of these patterns. We also present a grounded theory model developed to illustrate relationships discovered in this study.
Media Uses in Disaster Situations: A New Focus on the Impact Phase
Authors: Perez‐Lugo Marla
Published: April 2004

The media, in the sociology of natural disasters, are mainly viewed as management tools used to influence people's preparedness and response to natural disasters. As a consequence, research in this area has been limited to the warning, preparedness, and recovery phases. Through interviews with residents of eight communities in Mayagüez, Puerto Rico, impacted by Hurricane Georges in 1998, this paper shows that through integrating mass communication research to disaster theory we can obtain a more accurate picture of the media–audience relationship during natural disasters. In addition to the manifest functions of providing information, the media also have latent functions in disasters, which consist of emotional support and companionship. The media also help isolated individuals to feel connected with the “outside world.” These functions are most salient in the impact phase of disasters. These functions are also particularly crucial as they have been shown to reduce the negative effects of stressful life events.
Predicting Academic Misconduct: A Comparative Test of Four Sociological Explanations
Authors: Vowell Paul R. , Chen Jieming
Published: April 2004

Extant studies have shown academic misconduct, that is, cheating, to be a pervasive problem among college students. A number of avenues have been explored in order to determine those factors related to this type of deviant behavior. This study looks at a variety of traditional theoretical factors, including constructs representing social bond, self‐control, social strain, and differential association theories, using data from a stratified random sample of 674 undergraduates at a Southwestern university. We also enter into the equations a host of other factors that have been found to be related to academic misconduct in previous studies. Separate equations were estimated for each theory, and in the full model all theoretical variables were included for a total of six equations. In the full model, the data did not support strain or social bond theories, and moderate support was found for self‐control theory; however, strong support was found for differential association theory. The final equation accounted for 53.2 percent of the variance in academic misconduct.
Immunogenicity of a two‐dose regime of varicella vaccine in children with cancers
Authors: Leung Ting‐Fan , Li Chi‐Kong , Hung Emily C. W. , Chan Paul K. S. , Mo Chi‐Wai , Wong Raymond P. O. , Chik Ki‐Wai
Published: April 2004

Objective:  Live‐attenuated varicella vaccine is effective and safe in immunocompetent children. In this study, we assess the immunogenicity and adverse events following varicella vaccination in immunosuppressed cancer children.

Methods:  Varicella‐zoster virus (VZV)‐seronegative cancer children received two doses of live‐attenuated VZV vaccine (Varilrix®) in a span of 3 months. Patients with acute lymphoblastic leukaemia (ALL) were in the maintenance phase of chemotherapy, whereas those with solid tumours joined the study around 3–6 months from treatment discontinuation. VZV‐specific cellular and humoral immune responses were measured before and after VZV vaccination.

Results:  The median (range) age of the 17 patients was 4.4 yr (2.0–14.5). Thirteen had ALL, one had myelodysplastic syndrome and three had solid tumours. Following vaccination, the VZV‐specific stimulation index (SI) increased from 1.7 (0.9–2.9) to 17.9 (5.9–36.0) (P < 0.001). Similarly, SI to phytohaemagglutinin mitogen increased from 1136 (499–1930) to 1714 (848–2518) (P = 0.028). There were also significant increases in CD4+ cells and CD4 : CD8 ratio as well as a reduction in CD16/56+ cells in peripheral blood lymphocytes. Seroconversion rate to VZV was 19% after one dose and increased to 94% after the second dose of VZV vaccine. Serum VZV‐specific IgG concentrations also increased significantly following two doses when compared with one dose of VZV vaccine (P = 0.0004). One subject developed possibly vaccine‐related chickenpox with self‐limiting hepatitis at 5 wk following vaccination. None of the patients developed herpes‐zoster at a median (range) follow‐up of 27.5 months (24.0–30.0).

Conclusions:  Non‐immune cancer children can be effectively vaccinated against chickenpox at the defined period. However, the safety of chickenpox vaccine in these immunosuppressed children needs to be further studied.
Clinical impact of internal tandem duplications and activating point mutations in FLT3 in acute myeloid leukemia in elderly patients
Authors: Andersson Anna , Johansson Bertil , Lassen Carin , Mitelman Felix , Billström Rolf , Fioretos Thoas
Published: April 2004

Background:  The FLT3 gene is frequently mutated in acute myeloid leukemia (AML), either by an internal tandem duplication (ITD) of the juxtamembrane domain or by activating point mutations in the second tyrosine kinase domain (ATKD). Only a few investigations have focused on the prognostic significance of FLT3 alterations in AML among the elderly, yielding conflicting results. In the present study, the frequency and clinical relevance of FLT3 abnormalities were ascertained in a cohort of elderly AML patients.

Patients and methods:  A total of 109 AMLs, occurring in patients above the age of 60 yr (median 71.5), were investigated. DNA was extracted from fresh bone marrow cells or from cells in fixative and investigated for the presence of ITD of exons 14 and 15 and the ATKD D835 in exon 20.

Results:  ITDs and ATKDs were identified in 20 (18%) and 11 (10%) of the cases, respectively. Three cases displayed both an ITD and an ATKD. FLT3 abnormalities were associated with leukocytosis (ITD P < 0.01; ATKD P = 0.069), and the monocytic FAB subtypes M4 and M5 [ITD (P < 0.05), ATKD (P = 0.05)], and ITD and ATKD were significantly (P < 0.05) more common in cases with a normal karyotype. There was no correlation between the presence of FLT3 abnormalities and complete remission rates or overall survival.

Conclusion:  A correlation was observed between FLT3 abnormalities and leukocytosis, a normal karyotype, and the M4/M5 subtypes of leukemia. However, no clear‐cut prognostic impact of FLT3 abnormalities was identified in elderly AML patients.
Functional C3435T polymorphism of MDR1 gene: an impact on genetic susceptibility and clinical outcome of childhood acute lymphoblastic leukemia
Authors: Jamroziak Krzysztof , Młynarski Wojciech , Balcerczak Ewa , Mistygacz Magda , Treliǹska Joanna , Mirowski Marek , Bodalski Jerzy , Robak Tadeusz
Published: April 2004

The significance of genetic background in childhood acute lymphoblastic leukemia (ALL) is not well understood. Polymorphisms of genes encoding for xenobiotics and drug transporters are potential factors, which can influence the risk of developing ALL and its clinical outcome. P‐glycoprotein (P‐gp) is an adenosine triphosphate‐binding cassette (ABC)‐family transporter involved in protection against xenobiotics and multi‐drug resistance. Recently, the single‐nucleotide polymorphism C3435T of MDR1 gene has been found to be associated with altered tissue expression and function of P‐gp. To evaluate whether C3435T MDR1 polymorphism is associated with the occurrence and outcome of ALL, 113 children with ALL (median age 5.1 yr) and 175 healthy individuals of Polish Caucasian origin were studied by polymerase chain reaction‐restriction fragment‐length polymorhism (PCR‐RFLP) assay. The mutant homozygous TT genotype was found to be associated with occurrence of ALL (OR, 95% CI; 1.8, 1.1–3.1; P = 0.037). Besides, the analysis of factors influencing clinical outcome of our ALL patient cohort showed that CC genotype carriers had significantly lower event‐free survival probability (pEFS) (0.62 vs. 0.87; P = 0.007) and overall survival probability (pOS) (0.72 vs. 0.91; P = 0.006). The Cox proportional hazards model‐based analysis revealed that the hazard ratios for lower pEFS and lower pOS among CC homozygous subjects were 3.9 (P = 0.008) and 3.3 (P = 0.02), respectively. In conclusion, the results of the present study provide evidence that C3435T MDR1 polymorphism may involve both the susceptibility to and the clinical outcome of childhood ALL. Carriers of the TT genotype are more at risk of developing ALL than other individuals, whereas CC genotype carriers are supposed to have worse prognosis.
A compact multileaf collimator for conventional and intensity modulated fast neutron therapy
Authors: Farr Jonathan B.
Published: April 2004

A 120 leaf collimator of high resolution has been constructed to shape a fast neutron therapy (FNT) beam produced from a superconducting cyclotron using the reaction. The computer controlled multileaf collimator (MLC) replaces an aging, manually operated multirod collimator (MRC). The MLC was built to address two problems: The need to increase the efficiency of FNT at the Gershenson Radiation Oncology Center of the Karmanos Cancer Institute at Detroit, MI, and the desire to implement intensity modulated neutron radiotherapy for which a suitable computer controlled beam shaping device of high resolution and rapid shape changing not currently exist. The specific aims were to build a neutron MLC that would solve these problems and then verify its radiological performance as being clinically acceptable. The MLC leaves project 5 mm in the iso‐centric plane perpendicular to the beam axis. A taper has been included on the leaves matching the beam divergence along one axis. A 5 mm leaf projection width was chosen to give high resolution conformality across the entire field. The maximum field size provided is To reduce the interleaf transmission a 0.254 mm blocking step has been included. End‐leaf steps totaling 0.762 mm were also included allowing adjacent leaf pairs to close off within the primary radiation beam. The neutron MLC also includes individual and automated universal tungsten wedges. All electro‐mechanical functions of the MLC are governed by the multileaf collimator control system (MLCCS). The MLCCS control functions are leaf and wedge motion control, leaf and wedge position verification, switching on and off the radiation beam, and inputting certain cyclotron interlocks statuses as well as outputting MLC interlocks. The MLCCS is responsible for setting required shapes on the MLC, and verifying those shapes to be accurate to within for each leaf's projection in the plane perpendicular to the beam axis at the position of the iso‐center. The position verification function uses a machine vision system that images optical targets on the leaves to verify set field shape accuracy within at the level of iso‐center. The MLC transmission was measured to be 3.9±0.5% with an 11±2% gamma component which is slightly lower than the MRC measured transmission of 4.6±0.5% with a 17±2% gamma component. The difference in the measured gamma component ratio for the closed collimators agrees within 40% to a theoretical approximation of for tungsten to steel when considering equal attenuation lengths. The actual MLC penumbral measurements in water for a field at 5 cm depth were and along the focused and unfocused axes, respectively. The MRC penumbra measured under the same conditions along both of its focused axes suggesting penumbral equivalence between the MLC and MRC along the focused axis with slight degradation in the unfocused direction of the MLC. The many benefits of the fully automatic MLC over the semi‐manual MRC are considered to justify this compromise.
Dose rate and SDD dependence of commercially available diode detectors
Authors: Saini Amarjit S. , Zhu Timothy C.
Published: April 2004

The dose‐rate dependence of commercially available diode detectors was measured under both high instantaneous dose‐rate (pulsed) and low dose rate (continuous, Co‐60) radiation. The dose‐rate dependence was measured in an acrylic miniphantom at a 5‐cm depth in a collimator setting, by varying source–to‐detector distance (SDD) between at least 80 and 200 cm. The ratio of a normalized diode reading to a normalized ion chamber reading (both at was used to determine diode sensitivity ratio for pulsed and continuous radiation at different SDD. The inverse of the diode sensitivity ratio is defined as the SDD correction factor (SDD CF). The diode sensitivity ratio increased with increasing instantaneous dose rate (or decreasing SDD). The ratio of diode sensitivity, normalized to 4000 cGy/s, varied between 0.988 (1490 cGy/s)–1.023 (38 900 cGy/s) for unirradiated ‐type Isorad Gold, 0.981 (1460 cGy/s)–1.026 (39 060 cGy/s) for unirradiated QED Red type), 0.972 (1490 cGy/s)–1.068 (38 900 cGy/s) for preirradiated Isorad Red type), 0.985 (1490 cGy/s)–1.012 (38 990 cGy/s) for ‐type Pt‐doped Isorad‐3 Gold, 0.995 (1450 cGy/s)–1.020 (21 870 cGy/s) for ‐type Veridose Green, 0.978 (1450 cGy/s)–1.066 (21 870 cGy/s) for preirradiated Isorad‐p Red, 0.994 (1540 cGy/s)–1.028 (17 870 cGy/s) for ‐type preirradiated QED, 0.998 (1450 cGy/s)–1.003 (21 870 cGy/s) for the ‐type preirradiated Scanditronix and 0.998 (1490 cGy/s)–1.015 (38 880 cGy/s) for Scanditronix diodes. The ‐type diodes do not always show less dose‐rate dependence than the ‐type diodes. Preirradiation does not always reduce diode dose‐rate dependence. A comparison between the SDD dependence measured at the surface of a full scatter phantom and that in a miniphantom was made. Using a direct adjustment of radiation pulse height, we concluded that the SDD dependence of diode sensitivity can be explained by the instantaneous dose‐rate dependence if sufficient buildup is provided to eliminate electron contamination. An energy independent empirical formula was proposed to fit the dose‐rate dependence of diode sensitivity.
Aperture maneuver with compelled breath (AMC) for moving tumors: A feasibility study with a moving phantom
Authors: Suh Y. , Yi B. , Ahn S. , Kim J. , Lee S. , Shin S. , Shin S. , Choi E.
Published: April 2004

Respiration causes target motion, which is known to be one of the technical bottlenecks in radiotherapy, especially for stereotactic radio‐surgery and intensity modulated radiotherapy (IMRT). To overcome this problem, aperture maneuver with compelled breath (AMC) has been developed. In order to simulate compelled respiratory motion, a moving phantom using a ventilator was designed. As the air flow was forced to the bellows, which simulates the lungs, by a ventilator, a film connected to the ventilator moved like the respiratory target motion. A software was developed to transfer multileaf collimator motion from breathless to actual periodic breathing conditions. Static fields as well as step‐and‐shoot IMRT fields were modified in accordance with moving shapes to follow the target position, using the software with the controlled breathing information. Film dosimetry for a small field and for IMRT fields with a moving phantom was performed. To evaluate clinical implementation, five healthy volunteers were tested to breathe through a ventilator, and all of them could adapt the compelled breath without any difficulties. Additive margins for a moving target with AMC were not larger than 3 mm for respiratory organ motions up to 18 mm, while those with the static beam were 9 mm. For IMRT fields, large discrepancies were present between a static target and a moving target with the static beam, while they coincided well with AMC. Clinical acceptable differences between the dose distributions from a static target with the static beam and from a moving target with AMC revealed that this technique could be applied clinically.
Determination of dose‐area product from panoramic radiography using a pencil ionization chamber: Normalized data for the estimation of patient effective and organ doses
Authors: Perisinakis K. , Damilakis J. , Neratzoulakis J. , Gourtsoyiannis N.
Published: April 2004

The aims of the present study were (a) to investigate the potential of pencil ionization chamber to be used for the determination of dose‐width product (DWP) and dose‐area product (DAP) from panoramic radiographic exposures and (b) to provide data normalized to DAP for the determination of patient effective and gonadal dose from panoramic radiography performed in any laboratory. A pencil ionization chamber commonly used to measure CT dose index (CTDI) in CT scanners was employed to determine DWP for various combinations of panoramic exposure settings at the beam exit slit of a Cranex Tome panoramic x‐ray unit (Soredex, Helsinki, Finland). DWP values were also measured using an array of thermoluminescence dosimeters. Reproducibility of the DWP measurement was tested. The effect of milliamperage and kilovoltage of panoramic exposures on DWP was investigated. DAP was estimated using the value of DWP measured using the pencil ionization chamber and the beam exit slit length measured using dosimetric film attached on the beam exit slit. A Rando anthropomorphic phantom appropriately loaded with thermoluminescent dosimeters (TLDs) was used to obtain organ dose and effective dose values from panoramic radiography. Reproducibility of DWP determination using the proposed method was better than 1.5%. DWP was found to be linearly related to milliamperage and to kilovoltage raised in a power ranging from 2.18 to 2.55. DWP measured using the pencil chamber was found to be up to 11% higher than the corresponding values determined using TLD array. The panoramic exposure obtained with settings appropriate for the typical adult patient was found to result in 0.008 mSv patient effective dose, 0.0002 mGy gonadal dose, and DAP. The use of a pencil ionization chamber is proposed for the determination of DWP and DAP from panoramic radiographic exposures. Normalized data over DAP were provided for the determination of patient effective and gonadal dose from panoramic radiography.
Influence of iodine contrast agent on the range of ion beams for radiotherapy
Authors: Wertz Hansjörg , Jäkel Oliver
Published: April 2004

The basis for the range calculation of heavy ions in tissue is an empirical correlation between x‐ray CT numbers and ion ranges measured for tissue equivalent materials. Iodine contrast agents (CA), used during computed tomography (CT) imaging, lead to an increase of the Hounsfield units in tissue with increased CA uptake and cause errors in the calculation of the ranges. The aim of this work is to quantify how accurately ion range is calculated in CA loaded tissue. In order to quantify the mean change in Hounsfield units (HU), a statistical analysis of 25 CT data sets with and without CA was performed. To establish a relation between the change in Hounsfield units due to CA and changes in ion range, the Hounsfield number for various CA concentrations and the range of ions in CA was measured. The analysis of CT data sets showed that after intravenous injection of 100 ml contrast agent (Imeron®300) at a concentration of 300 mg iodine/ml an increase of the Hounsfield numbers in tumor tissue of up to 57 HU can be observed. The measured range shift in CA is much smaller than calculated by the treatment planning system (TPS). The maximum error in range resulting from the CA enhanced data is approximately 2.5% and results mainly from this wrong interpretation of HU by the TPS. For a tumor with an extent of 5 cm this leads to an exaggeration of the ion ranges during irradiation of This may be clinically relevant in cases where highest precision is needed and where organs at risk are close to the target volume. In view of these findings it may be safer to rely solely on native CT data for the purpose of dose and range optimization in therapy planning for heavy ions and protons.
The significant effects of bone structure on inherent patient‐specific DXA in vivo bone mineral density measurement inaccuracies
Authors: Bolotin H. H.
Published: April 2004

An extended analytic exposition is developed of the effects bone structure has on the form and extent of systematic inaccuracies in planar dual‐energy x‐ray absorptiometry (DXA) in vivo bone mineral density (BMD) measurements. Explicit expressions for absolute and percentage BMD inaccuracies are derived and criteria governing these BMD inaccuracies delineated. It is shown that the effect of bone structure is to introduce a scale factor which modulates the sizable and unavoidable DXA in vivo/in situ BMD inaccuracies that arise directly from patient‐specific anthropometric and x‐ray absorptiometric disparities among the several soft tissues present within the scan region of interest of any given bone site (i.e., lean muscle tissue, interposed and admixed fat, and red/yellow marrow combinations). Different magnitudes and patterns of BMD inaccuracies are shown to pertain for bone structures that are (i) essentially wholly trabecular, (ii) wholly cortical, and (iii) those containing both cortical and trabecular bone. Over the range of soft tissue anthropometrics typical of adult patients, the overall percentage inaccuracies in DXA‐measured BMD are shown to be quite sizable and to vary considerably for different bone structures. For a typical lumbar vertebral bone site, BMD inaccuracies are found to be as large as for normal patients, to exceed for osteopenics, and to approach 50% for osteoporotic individuals. For bone sites with non‐negligible cortical surrounds of trabecular structures (e.g., distal radius, some segments of proximal femur, etc.), it is shown that BMD percentage inaccuracies range up to for normal, osteopenic, and for osteoporotic patients. The BMD % inaccuracies associated with wholly cortical bone (trabecular‐free) sites (e.g., mid‐shaft femur, mid‐shaft radius, etc.) are comparatively small, being less than Depending on bone structure, bone size and shape, and patient‐specific intra‐ and extra‐osseous soft tissue particulars of any given adult patient, DXA in vivo BMD measurements can be grossly inaccurate, and can severely under‐ or over‐estimate the true value of BMD and mask or exaggerate true changes in BMD in ways not previously elucidated. It is concluded that in vivo DXA‐measured and actual BMD cannot be considered to be synonymous, and clinical reliance upon the two being the same may readily conduce to seriously flawed and misleading diagnostic, prognostic, and prospective results.
Computer‐aided diagnosis scheme for histological classification of clustered microcalcifications on magnification mammograms
Authors: Nakayama Ryohei , Uchiyama Yoshikazu , Watanabe Ryoji , Katsuragawa Shigehiko , Namba Kiyoshi , Doi Kunio
Published: April 2004

The histological classification of clustered microcalcifications on mammograms can be difficult, and thus often require biopsy or follow‐up. Our purpose in this study was to develop a computer‐aided diagnosis schemefor identifying the histological classification of clustered microcalcifications on magnification mammograms in order to assist the radiologists' interpretation as a “second opinion.” Our database consisted of 58 magnification mammograms, which included 35 malignant clustered microcalcifications (9 invasive carcinomas, 12 noninvasive carcinomas of the comedo type, and 14 noninvasive carcinomas of the noncomedo type) and 23 benign clustered microcalcifications (17 mastopathies and 6 fibroadenomas). The histological classifications of all clustered microcalcifications were proved by pathologic diagnosis. The clustered microcalcifications were first segmented by use of a novel filter bank and a thresholding technique. Five objective features on clustered microcalcifications were determined by taking into account subjective features that experienced the radiologists commonly use to identify possible histological classifications. The Bayes decision rule with five objective features was employed for distinguishing between five histological classifications. The classification accuracies for distinguishing between three malignant histological classifications were 77.8% (7/9) for invasive carcinoma, 75.0% (9/12) for noninvasive carcinoma of the comedo type, and 92.9% (13/14) for noninvasive carcinoma of the noncomedo type. The classification accuracies for distinguishing between two benign histological classifications were 94.1% (16/17) for mastopathy, and 100.0% (6/6) for fibroadenoma. This computerized method would be useful in assisting radiologists in their assessments of clustered microcalcifications.
Metrological and treatment planning improvements on external beam radiotherapy. Detector size effect and dose calculation in low‐density media (in Spanish)
Authors: Garcı́a‐Vicente Feliciano
Published: April 2004

The objective of this thesis is the improvement of the measurement and calculation accuracy for radiation therapy fields. Basically, it deals with two questions: the detector size effect and the heterogeneity dose calculation. The author analyzes both the metrological and computational effects and its clinical implications by simulation of the radiotherapy treatments in a treatment planning system. The detector size effect leads up to smoothing of the radiation profile increasing the penumbra (20%–80%) and beam fringe (50%–90%) values with the consequent clinical effect of over‐irradiation of the organs at risk close to the planning target volume (PTV). In this thesis this problem is analyzed finding mathematical solutions based on profile deconvolution or the use of radiation detectors of adequate size. On the other side, the author analyzes the dose computation on heterogeneous media by the superposition algorithms versus classical algorithms. The derived conclusion from this thesis is that in locations like lung and breast, the classical algorithms lead to a significant underdosage of the PTV with an important decrease of tumor control probability (TCP). On this basis, the author does not recommend the clinical use of these algorithms in the mentioned tumor locations.
Improving binding potential analysis in PET studies using cluster analysis
Authors: Glatting Gerhard , Mottaghy Felix M. , Karitzky Jochen , Baune Axel , Sommer Friedrich T. , Landwehrmeyer G. Bernhard , Reske Sven N.
Published: April 2004

To calculate binding potentials (BP) in brain PET studies a reference tissue model is widely used. The aim of the present study was to improve the determination of time activity curves (TAC) of reference tissue regions using cluster analysis. In four patients with Huntington disease TACs of a cerebellar reference region were calculated either from manually placed circular ROIs within the cerebellum or by cluster analysis. BP estimates derived from cluster analysis are independent from inter‐ and intraobserver variations and show an improved reproducibility combined with a low variability compared to manually placed cerebellar ROIs. This is of high value in longitudinal studies.
Correlation between mammographic density and volumetric fibroglandular tissue estimated on breast MR images
Authors: Wei Jun , Chan Heang‐Ping , Helvie Mark A. , Roubidoux Marilyn A. , Sahiner Berkman , Hadjiiski Lubomir M. , Zhou Chuan , Paquerault Sophie , Chenevert Thomas , Goodsitt Mitchell M.
Published: April 2004

Previous studies have found that mammographic breast density is highly correlated with breast cancer risk. Therefore, mammographic breast density may be considered as an important risk factor in studies of breast cancer treatments. In this paper, we evaluated the accuracy of using mammograms for estimating breast density by analyzing the correlation between the percent mammographic dense area and the percent glandular tissue volume as estimated from MR images. A dataset of 67 cases having MR images (coronal 3‐D SPGR T1‐weighted pre‐contrast) and corresponding 4‐view mammograms was used in this study. Mammographic breast density was estimated by an experienced radiologist and an automated image analysis tool, Mammography Density ESTimator (MDEST) developed previously in our laboratory. For the estimation of the percent volume of fibroglandular tissue in breast MR images, a semiautomatic method was developed to segment the fibroglandular tissue from each slice. The tissue volume was calculated by integration over all slices containing the breast. Interobserver variation was measured for 3 different readers. It was found that the correlation between every two of the three readers for segmentation of MR volumetric fibroglandular tissue was 0.99. The correlations between the percent volumetric fibroglandular tissue on MR images and the percent dense area of the CC and MLO views segmented by an experienced radiologist were both 0.91. The correlation between the percent volumetric fibroglandular tissue on MR images and the percent dense area of the CC and MLO views segmented by MDEST was 0.91 and 0.89, respectively. The root‐mean‐square (rms) residual ranged from 5.4% to 6.3%. The mean bias ranged from 3% to 6%. The high correlation indicates that changes in mammographic density may be a useful indicator of changes in fibroglandular tissue volume in the breast.
EUD‐based margin selection in the presence of set‐up uncertainties
Authors: Song William , Dunscombe Peter
Published: April 2004

To assess the impact of geometric uncertainties on treatment plan design, we have performed a numerical simulation in which both systematic and random errors were included. A clinical target volume (CTV) with an abutting organ at risk (OAR), both of 50 mm diameter, in a cubic phantom was modeled. A four‐field conformal treatment plan was designed in which one pair of parallel‐opposed beams traversed the OAR and CTV while the other pair intersected the CTV only. Field size, prescribed (isocenter) dose and systematic set‐up uncertainty were varied in two orthogonal directions to examine their impact on the outcome as predicted by the dose volume histogram (DVH) and the phenomenological form of equivalent uniform dose (EUD). Of the systematic uncertainty levels considered (0, 2, 4, and 6 mm standard deviations of a Gaussian distribution), 10 mm margin (CTV–PTV) was adequate to maintain the integrity of the dose distribution within the CTV. However, reducing the margin (and hence field size) without reducing set‐up errors required an increase in the isocenter dose to compensate for the loss in EUD. It was found that, in the direction containing both the CTV and OAR, with random and systematic uncertainties of 2 and 4 mm respectively, increasing the isocenter dose by about 3.5 Gy on a 6 mm‐margin plan resulted in the statistically equivalent EUD value to that with a 10 mm‐margin for the CTV, while the OAR EUD is dropped by 1 Gy. In general, though, the directional sensitivity to geometric uncertainties, and hence the required margin size in different directions, was dependent on beam geometries and the relative positions of the structures under consideration relative to the beam directions. Based on the validity of the EUD concept, our general conclusion is that modest dose escalation may result in plans that better achieve clinical objectives. Also, a simple single number plan quality index such as discussed in the paper, facilitates meaningful statistical comparisons between competing treatment strategies.
Computerized detection of colorectal masses in CT colonography based on fuzzy merging and wall‐thickening analysis
Authors: Näppi Janne J. , Frimmel Hans , Dachman Abraham H. , Yoshida Hiroyuki
Published: April 2004

In recent years, several computer‐aided detection (CAD) schemes have been developed for the detection of polyps in CT colonography (CTC). However, few studies have addressed the problem of computerized detection of colorectal masses in CTC. This is mostly because masses are considered to be well visualized by a radiologist because of their size and invasiveness. Nevertheless, the automated detection of masses would naturally complement the automated detection of polyps in CTC and would produce a more comprehensive computer aid to radiologists. Therefore, in this study, we identified some of the problems involved with the computerized detection of masses, and we developed a scheme for the computerized detection of masses that can be integrated into a CAD scheme for the detection of polyps. The performance of the mass detection scheme was evaluated by application to clinical CTC data sets. CTC was performed on 82 patients with helical CT scanners and reconstruction intervals of 1.0–5.0 mm in the supine and prone positions. Fourteen patients (17%) had a total of 14 masses of 30–50 mm, and sixteen patients (20%) had a total of 30 polyps 5–25 mm in diameter. Four patients had both polyps and masses. Fifty‐six of the patients (68%) were normal. The CTC data were interpolated linearly to yield isotropic data sets, and the colon was extracted by use of a knowledge‐guided segmentation technique. Two methods, fuzzy merging and wall‐thickening analysis, were developed for the detection of masses. The fuzzy merging method detected masses with a significant intraluminal component by separating the initial CAD detections of locally cap‐like shapes within the colonic wall into mass candidates and polyp candidates. The wall‐thickening analysis detected nonintraluminal masses by searching the colonic wall for abnormal thickening. The final regions of the mass candidates were extracted by use of a level set method based on a fast marching algorithm. False‐positive (FP) detections were reduced by a quadratic discriminant classifier. The performance of the scheme was evaluated by use of a leave‐one‐out (round‐robin) method with by‐patient elimination. All but one of the 14 masses, which was partially cut off from the CTC data set in both supine and prone positions, were detected. The fuzzy merging method detected 11 of the masses, and the wall‐thickening analysis detected 3 of the masses including all nonintraluminal masses. In combination, the two methods detected 13 of the 14 masses with 0.21 FPs per patient on average based on the leave‐one‐out evaluation. Most FPs were generated by extrinsic compression of the colonic wall that would be recognized easily and quickly by a radiologist. The mass detection methods did not affect the result of the polyp detection. The results indicate that the scheme is potentially useful in providing a high‐performance CAD scheme for the detection of colorectal neoplasms in CTC.
Accounting for center‐of‐mass target motion using convolution methods in Monte Carlo‐based dose calculations of the lung
Authors: Chetty Indrin J. , Rosu Mihaela , McShan Daniel L. , Fraass Benedick A. , Balter James M. , Ten Haken Randall K.
Published: April 2004

We have applied convolution methods to account for some of the effects of respiratory induced motion in clinical treatment planning of the lung. The 3‐D displacement of the GTV center‐of‐mass (COM) as determined from breath‐hold exhale and inhale CT scans was used to approximate the breathing induced motion. The time‐course of the GTV‐COM was estimated using a probability distribution function (PDF) previously derived from diaphragmatic motion [Med. Phys. 26, 715–720 (1990)] but also used by others for treatment planning in the lung [Int. J. Radiat. Oncol., Biol., Phys. 53, 822–834 (2002); Med. Phys. 30, 1086–1095 (2003)]. We have implemented fluence and dose convolution methods within a Monte Carlo based dose calculation system with the intent of comparing these approaches for planning in the lung. All treatment plans in this study have been calculated with Monte Carlo using the breath‐hold exhale CT data sets. An analysis of treatment plans for 3 patients showed substantial differences (hot and cold spots consistently greater than between the motion convolved and static treatment plans. As fluence convolution accounts for the spatial variance of the dose distribution in the presence of tissue inhomogeneities, the doses were approximately 5% greater than those calculated with dose convolution in the vicinity of the lung. DVH differences between the static, fluence and dose convolved distributions for the CTV were relatively small, however, larger differences were observed for the PTV. An investigation of the effect of the breathing PDF asymmetry on the motion convolved dose distributions showed that reducing the asymmetry resulted in increased hot and cold spots in the motion convolved distributions relative to the static cases. In particular, changing from an asymmetric breathing function to one that is symmetric results in an increase in the hot/cold spots of relative to the static plan. This increase is not unexpected considering that the target spends relatively more time at inhale as the asymmetry decreases (note that the treatment plans were generated using the exhale CT scans).
Wind at His Back
Authors: Chen Ingfei
Published: April 2004

The question of why and how organisms age has preoccupied Trey Powers since he was 14. By the time he was a high school senior, he had conducted his first experiments in a gerontology research group at the Jackson Laboratory in Maine. Today Powers is a third-year grad student at the University of Washington, Seattle. When he isn't probing the mechanisms of aging in baker's yeast, he races in sailing competitions on the Puget Sound.
Never Too Old?
Authors: Leslie Mitch
Published: April 2004

The elderly have to endure plenty of indignities, from balky joints and dimming vision to offspring impatient for their inheritance. Making matters worse, older animals might not benefit from a low-cal diet that extends the lives of younger ones. New work challenges that view, suggesting that slashing food consumption even fairly late in life can add time, although skeptics remain unconvinced.
Werner Syndrome Protein--Unwinding Function to Explain Disease
Authors: Monnat Jr. Raymond J. , Saintigny Yannick
Published: April 2004

Werner syndrome (WS) is one of three heritable human genetic instability/cancer predisposition syndromes that result from mutations in a member of the gene family encoding human RecQ helicases. Cellular defects are a prominent part of the WS phenotype. Here we review recent work to identify in vivo functions of the WS protein and discuss how loss of function leads to cellular defects. These new results provide clues to the origin of cell lineage-specific defects in WS patients and suggest a broader role for Werner protein function in determining disease risk in the general population.
Harnessing Nonlinearity: Predicting Chaotic Systems and Saving Energy in Wireless Communication
Authors: Jaeger Herbert , Haas Harald
Published: April 2004

We present a method for learning nonlinear systems, echo state networks (ESNs). ESNs employ artificial recurrent neural networks in a way that has recently been proposed independently as a learning mechanism in biological brains. The learning method is computationally efficient and easy to use. On a benchmark task of predicting a chaotic time series, accuracy is improved by a factor of 2400 over previous techniques. The potential for engineering applications is illustrated by equalizing a communication channel, where the signal error rate is improved by two orders of magnitude.
Formation of Al
13
I
-
: Evidence for the Superhalogen Character of Al
13
Authors: Bergeron Denis E. , Castleman A. Welford , Morisato Tsuguo , Khanna Shiv N.
Published: April 2004

Al
13
–
is a cluster known for the pronounced stability that arises from coincident closures of its geometric and electronic shells. We present experimental evidence for a very stable cluster corresponding to Al
13
I
–
. Ab initio calculations show that the cluster features a structurally unperturbed Al
13
–
core and a region of high charge density on the aluminum vertex opposite from the iodine atom. This ionically bound magic cluster can be understood by considering that Al
13
has an electronic structure reminiscent of a halogen atom. Comparisons to polyhalides provide a sound explanation for our chemical observations.
Development of a Human Adaptive Immune System in Cord Blood Cell-Transplanted Mice
Authors: Traggiai Elisabetta , Chicha Laurie , Mazzucchelli Luca , Bronz Lucio , Piffaretti Jean-Claude , Lanzavecchia Antonio , Manz Markus G.
Published: April 2004

Because ethical restrictions limit in vivo studies of the human hemato-lymphoid system, substitute human to small animal xenotransplantation models have been employed. Existing models, however, sustain only limited development and maintenance of human lymphoid cells and rarely produce immune responses. Here we show that intrahepatic injection of CD34
+
human cord blood cells into conditioned newborn Rag2
–/–
γ
c
–/–
mice leads to de novo development of B, T, and dendritic cells; formation of structured primary and secondary lymphoid organs; and production of functional immune responses. This provides a valuable model to study development and function of the human adaptive immune system in vivo.
Approaching the Quantum Limit of a Nanomechanical Resonator
Authors: LaHaye M. D. , Buu O. , Camarota B. , Schwab K. C.
Published: April 2004

By coupling a single-electron transistor to a high–quality factor, 19.7-megahertz nanomechanical resonator, we demonstrate position detection approaching that set by the Heisenberg uncertainty principle limit. At millikelvin temperatures, position resolution a factor of 4.3 above the quantum limit is achieved and demonstrates the near-ideal performance of the single-electron transistor as a linear amplifier. We have observed the resonator's thermal motion at temperatures as low as 56 millikelvin, with quantum occupation factors of N
TH
= 58. The implications of this experiment reach from the ultimate limits of force microscopy to qubit readout for quantum information devices.