bluuebunny/crossref_metadata_2025 huggingface dataset:
A large upstream region is not necessary for gene expression or hypersensitive site formation at the mouse β-globin locus
Authors: Farrell Catherine M. , Grinberg Alexander , Huang Sing Ping , Chen Dan , Pichel José G. , Westphal Heiner , Felsenfeld Gary
Published: July 2002

Developmental expression at the β-globin locus is regulated
in part by the locus control region, a region upstream of the genes
containing at least five major DNase I hypersensitive sites (HSs) in
mammalian erythrocytes. Sequences farther 5′ of these HSs are conserved
in mouse and human, and both loci are embedded within a cluster of
functional odorant receptor genes. In humans, distant upstream
sequences have been implicated in regulation of the β-globin genes.
In this study, the role of the 5′-most HSs and their adjacent sequence
was investigated by deletion of an 11-kb region from the mouse locus,
including 5′HS 4.2, 5′HS 5, 5′HS 6, and the 5′β1 odorant receptor
gene. Mice that were homozygous for this deletion were fully viable,
and no significant effect on adult β-globin gene expression was seen.
5′HSs 1–4, which are located downstream of the deletion, were still
present in the mutant mice. In addition, two new upstream HSs, HS
−60.7 and HS −62.5, were found in erythroid tissue of both wild-type
and mutant mice. Therefore, although the possibility of a minor role
still exists, neither the HSs nor the other regions deleted in this
study are essential for β-globin gene expression, and it is unlikely
that chromatin structure is affected either upstream or downstream of
the deletion. This is the largest deletion at the mouse locus control
region to show no apparent phenotype, and focuses attention on the
possible contribution of sequences even farther upstream.
Le modèle écoculturel: un cadre pour la psychologie culturelle comparative
Authors: Troadec Bertrand
Published: July 2002

L'objectif de cet article est d'argumenter, à partir d'une conception constructiviste de la connaissance scientifique, les fondements épistémologiques d'une approche culturelle comparative contemporaine, en invoquant la nécessité d'un paradigme heuristique de recherches, tel que peut l'être le modèle écoculturel de John Berry. Ce modèle est envisagé comme la modélisation systémique par un psychologue de phénomènes perçus complexes, en l'occurrence les relations “esprit‐cerveau‐culture” et leur développement. Au niveau individuel de l'analyse, on défend la nécessité de dépasser la distinction classique entre des compétences et des performances. Les compétences sont différenciées ici en croyances intuitives (ou fonctions mentales élémentaires) et croyances réflexives (ou fonctions mentales supérieures). Celles‐ci restent conçues comme étant conjointement à l'origine des comportements observables. Il en ressort la possibilité théorique d'un “constructivisme relativiste” qui pourrait convenir mieux que le “constructivisme universaliste”, tel que Jean Piaget l'a proposé.
The Conditioned Attention Theory and Bifactorial Theory on the Learned Helplessness Syndrome in Appetitive Contexts
Authors: Ferrándiz P. , Vicente F.
Published: July 2002

The purpose of the present experiment was to explore the theory that deficits in learned helplessness, normally produced by inescapable shock or noncontingent events, are eliminated in subsequent learning discrimination when a combination of exteroceptive cues or feedback stimuli and a predictable stimulus are present. We used 48 pigeons in 6 groups: Group P+C+ training with predictable and controllable events; Group P+U— training with predictable and uncontrollable events; Group U—F training with unpredictable and uncontrollable events and feedback stimulus; Group P+U—F training with predictable and uncontrollable events and feedback stimulus; Group U‐RE training with unpredictable, uncontrollable and random events; Group CG did not receive any treatment. Our results demonstrated that a combination of feedback stimuli and predictability was found to be the most effective training against effects of noncontingent events in appetitive contexts.
L'évaluation subjective directe des émotions ressenties au sein du couple
Authors: Bégin Catherine , Sabourin Stéphane , Lussier Yvan , Wright John
Published: July 2002

Cette étude vise à déterminer la valeur d'une évaluation subjective directe des émotions ou des affects ressentis au sein des relations de couple. Pour ce faire, nous vérifierons si—au‐delà des relations observées entre la satisfaction conjugale, d'une part, et, d'autre part, la personnalité, les symptômes psychologiques et le style d'attachement—l'évaluation subjective directe des émotions ajoute à notre compréhension de l'adaptation conjugale. L'échantillon se compose de 204 couples francophones mariés ou cohabitant. Les résultats laissent entrevoir des différences liées au sexe et au degré de détresse conjugale. Les femmes éprouvent plus d'insécurité, d'injustice, de dévalorisation et d'impuissance que les hommes. Les conjoints insatisfaits se démarquent par la présence de forts sentiments d'insécurité, d'injustice, de dévalorisation et d'impuissance.
The Influence of Social Context on Requests in Young Iranian Children
Authors: Marcos Haydée , Verba Mina
Published: July 2002

This study concerns the influence of social contexts on young children's communication. The aim was to show that, at a very young age, children take into account the conversational context and certain conventions governing social relations. Iranian children's request behaviours were analyzed in three situations: (a) the adult immediately complies (satisfaction), (b) the adult asks a clarification question (clarification), and (c) the adult refuses to comply (refusal). Two groups of 12 children aged 18 and 30 months were observed in day‐care centres during dyadic interaction with an Iranian adult. The verbal and nonverbal productions of the two groups were considered. The results showed that the children modified their behaviours in accordance with the adult's attitude. Comparison with a study conducted in France suggests that reformulations in the clarification situation are similar in the two cultures. The intercultural differences observed concern both overall request production and the characteristics of reformulations in the refusal situation. These specificities reflect the early influence of cultural values concerning the difference between the social status of children and adults.
Imagining the past: the use of archive pictures in secondary school history textbooks
Authors: David Robert G.
Published: July 2002

This article examines the use of archive pictures (paintings, photographs and engravings) in school textbooks, in the controversial setting of the Key Stage 3 (11–14) and Key Stage 4 (14–16) topics of the American West and the Native Peoples of North America, where pictorial images have created powerful stereotypes. Attention is drawn to the 1994 Schools Curriculum and Assessment Authority's report on history textbooks, which criticized the lack of supporting information for archive pictures. Textbooks written prior to the 1994 report are contrasted with those written since. It is noted that despite the report and recent historical interest in the study of representations, there has been little improvement in textbook design. The methods of analysis that should be used on paintings, photographs and engravings are explained in some detail, and the effect of not providing the essential background for pupils to develop a reasoned discussion of their value as historical evidence is demonstrated through a number of case‐studies. Finally a checklist is provided for authors, publishers, teachers, trainee teachers and teacher educators to help them incorporate essential background material, in order to ensure that pupils can bring the same critical awareness to pictorial images as they have become accustomed to with written sources.
A tale of two cities: HIV risk behaviours among injecting drug users in Hanoi and Ho Chi Minh City, Vietnam
Authors: ABDUL‐QUADER ABU S. , QUAN VU MINH , O'REILLY KEVIN
Published: July 2002

The aim of this study was to describe and highlight HIV drug risk behaviours among injecting drug users (IDUs) in Hanoi and Ho Chi Minh City, Vietnam. Using a cross‐sectional design 470 IDUs (Hanoi, n = 302; Ho Chi Minh City, n = 168) were recruited and interviewed by trained interviewers. The IDUs in Ho Chi Minh City were older, more likely to be employed and less likely to be single than those in Hanoi. History of injecting also varied: on average, IDUs in Ho Chi Minh City had been injecting longer (17 years in Ho Chi Minh City compared with 3 years in Hanoi). Three‐quarters of the IDUs injected at least once a day and a similar proportion had their last injections administered by someone else. Eighty‐two per cent had seen and/or read something on HIV/AIDS and 73% mentioned to have initiated risk reduction; however, no significant difference was found between two cities. Even though there is a significant difference between IDUs in Hanoi and Ho Chi Minh City in terms of certain risk behaviours, the IDUs in both cities continue to expose themselves to HIV infection. In addition, no significant difference was observed between the IDUs in these two cities in terms of initiating HIV risk reduction, even though prevention programmes were implemented in Ho Chi Minh City earlier than in Hanoi. The presence of high‐risk behaviours and absence of any meaningful risk reduction among IDUs in both cities indicate the need for intensive targeted intervention. [Abdul‐Quader A, Quan VM, O'Reilly K. A tale of two cities: HIV risk behaviours among injecting drug users in Hanoi and Ho Chi Minh City, Vietnam. Drug Alcohol Rev 1999;18:401–407]
The Relationship Between Parental History and Substance Use Severity in Drug Treatment Patients
Authors: Boyd Susan J. , Plemons Bradford W. , Schwartz Robert P. , Johnson Jeannette L. , Pickens Roy W.
Published: July 2002

The authors explored the relationship between the history of parental problematic alcohol and drug use and their adult children's alcohol and drug use disorders. Subjects were 347 admissions to an outpatient substance abuse program. There was a positive relationship between the number of parents affected by alcohol and/or drug problems and the percentage of probands with co‐existing alcohol and drug use disorders for probands with alcohol use disorders but not for those with only drug abuse. Probands with two affected parents had significantly higher alcohol abuse scores and drug, family, and psychiatric composite test scores than those with a negative family history. This preliminary study indicates that the severity of a proband's substance use disorder may be influenced by parental substance use history.
Induction of Fos protein by 3,4‐ methylenedioxymethamphetamine (Ecstasy) in rat brain: regional differences in pharmacological manipulation
Authors: HASHIMOTO KENJI , TOMITAKA SHIN‐ICHIRO , NARITA NATSUKO , MINABE YOSHIO , IYO MASAOMI
Published: July 2002

Psychostimulant drugs have been reported to increase the expression of some immediate‐early genes in the brain. In the present study, immunohistochemical techniques were used to assess the pattern of Fos protein produced by 3,4‐methylenedioxymethamphetamine (MDMA) in several brain regions. Furthermore, we also studied the role of the dopamine D and D receptors and the N‐methyl‐ D‐aspartate (NMDA) receptor in the induction of Fos protein by MDMA. A single administration of MDMA (5, 10 or 20 mg/kg) caused marked induction of Fos‐immunoreactivity in several regions including frontal cortex, striatum and olfactory tubercle of rat brain, in a dose‐dependent manner. However, in the hippocampus and cerebellum, there were few or no Fos immunoreactive cells induced by MDMA. Furthermore, the induction of Fos protein in the striatum and olfactory tubercle after administration of MDMA (10 mg/kg) was blocked by pre‐treatment with the dopamine D receptor antagonist SCH 23390 (1 mg/kg) or the NMDA receptor antagonist dizocilpine (1 mg/kg), but not by the dopamine D receptor antagonist (‐)‐sulpiride (100 mg/kg). However, the induction of Fos protein in the frontal cortex and hippocampus by MDMA was unaltered by pretreatment with SCH 23390 (1 mg/kg) or (‐)‐sulpiride (100 mg/kg). These results suggest that MDMA induces the expression of Fos protein in several regions of rat brain, and that the expression of Fos protein by MDMA in the striatum and olfactory tubercle appears to be mediated at least in part by the dopamine D and NMDA receptors.
Central pontine myelinolysis in a normonatraemic alcoholic patient
Authors: MUNDLE GÖTZ , FRIESE SIGRID , KÖHNKE MICHAEL D.
Published: July 2002

Central pontine myelinolysis (CPM) is a rare disease which has been associated with hyponatraemia and its rapid correction. We describe a malnourished 32‐year‐old alcohol‐dependent woman suffering from an infection who had developed CPM without any known prior derangement in serum electrolytes or its iatrogenic correction. Computerized tomography (CT) and magnetic resonance imaging (MRI) played an important role in the diagnosis. Even when an electrolyte derangement is absent, alcoholism, malnourishment and infection should be considered as important possible aetiological factors of CPM.
Pancreatitis‐associated proteins: experimental and clinical studies
Authors: PAAJANEN HANNU , NORDBACK ISTO
Published: July 2002

Various novel biochemical markers indicate pancreatic cellular injury more accurately than serum amylase or lipase. One of these is a non‐enzymatic secretory protein called pancreatitis‐associated protein (PAP).The main function of PAP is unclear at present but it may be an acute phase protein in the defence reactions of pancreatic cells. The protein was characterized in 1984 as a serum marker of pancreatitis. The serum PAP is expressed 6 hours after the induction of pancreatitis, and it increases to maximal levels within 2–4 days: PAP is not sufficiently sensitive for the diagnosis of acute pancreatitis in the emergency room. The sensitivity and specificity of PAP in the differentiation of severe from mild pancreatitis is between 60–70%. This is not superior to serum CRP assays or CT scans. PAP increases in pancreatic cellular injury without pancreatitis (subclinical cell damage, graft rejection) where PAP may have a diagnostic role.
Traffic through the Golgi apparatus
Authors: Pelham Hugh R.B.
Published: July 2002

The role of vesicles in cargo transport through the Golgi apparatus has been controversial. Large forms of cargo such as protein aggregates are thought to progress through the Golgi stack by a process of cisternal maturation, balanced by a return flow of Golgi resident proteins in COPI-coated vesicles. However, whether this is the primary role of vesicles, or whether they also serve to transport small cargo molecules in a forward direction has been debated. Two papers (Martínez-Menárguez et al., 2001; Mironov et al., 2001, this issue) use sophisticated light and electron microscopy to provide evidence that the vesicular stomatitis virus membrane glycoprotein (VSV G)**Abbreviation used in this paper: VSV G, vesicular stomatitis virus membrane glycoprotein. is largely excluded from vesicles in vivo, and does not move between cisternae, whereas resident Golgi enzymes freely enter vesicles as predicted by the cisternal maturation model. Both papers conclude that vesicles are likely to play only a minor role in the anterograde transport of cargo through the Golgi apparatus in mammalian tissue culture cells.
Triggering a Second T Cell Receptor on Diabetogenic T Cells Can Prevent Induction of Diabetes
Authors: Fossati Gianluca , Cooke Anne , Papafio Ruby Quartey , Haskins Kathryn , Stockinger Brigitta
Published: July 2002

In this paper, we test the hypothesis that triggering of a second T cell receptor (TCR) expressed on diabetogenic T cells might initiate the onset of diabetes. A cross between two TCR-transgenic strains, the BDC2.5 strain that carries diabetogenic TCRs and the A18 strain that carries receptors specific for C5, was set up to monitor development of diabetes after activation through the C5 TCR. F1 BDC2.5 × A18 mice developed diabetes spontaneously beyond 3–4 mo of age. Although their T cells express both TCRs constitutively, the A18 receptor is expressed at extremely low levels. In vitro activation of dual TCR T cells followed by adoptive transfer into neonatal or adult F1 mice resulted in diabetes onset and death within 10 d after transfer. In contrast, in vivo immunization of F1 mice with different forms of C5 antigen not only failed to induce diabetes but protected mice from the spontaneous onset of diabetes. We propose that antigenic stimulation of cells with low levels of TCR produces signals inadequate for full activation, resulting instead in anergy.
Accelerated polynomial approximation of finite order entire functions by growth reduction
Authors: Müller Jürgen
Published: July 2002

Let

f
f

be an entire function of positive order and finite type. The subject of this note is the convergence acceleration of polynomial approximants of

f
f

by incorporating information about the growth of

f
(
z
)

f(z)

for

z
→
∞

z\to \infty

. We consider “near polynomial approximation” on a compact plane set

K
K

, which should be thought of as a circle or a real interval. Our aim is to find sequences

(

f
n

)
n

(f_n)_n

of functions which are the product of a polynomial of degree

≤
n

\le n

and an “easy computable” second factor and such that

(

f
n

)
n

(f_n)_n

converges essentially faster to

f
f

on

K
K

than the sequence

(

P
n
∗

)
n

(P_n^*)_n

of best approximating polynomials of degree

≤
n

\le n

. The resulting method, which we call Reduced Growth method (

R
G

RG

-method) is introduced in Section 2. In Section 5, numerical examples of the

R
G

RG

-method applied to the complex error function and to Bessel functions are given.
“SMART” GUNS: A TECHNOLOGICAL FIX FOR REGULATING THE SECONDARY MARKET
Authors: Cook Philip J. , Leitzel James A.
Published: July 2002

A “personalized” or “smart” gun will not fire unless it is being used by an authorized individual. Such guns have the potential to reduce the negative externalities of gun ownership while preserving the benefits. Ongoing efforts to develop practical “smart” designs make it timely to consider regulations that would favor or mandate them in the market for new guns. The likely consequences would depend on the design details, in particular the costs of transferring the “key” to firing such guns. With an “ideal” design, transferring the key would require special equipment that could be monitored by appropriate authorities. The result would be to block thefts and other transfers of such guns in the secondary market and, in the long run, reduce access by individuals who are proscribed from possessing a gun. Personalized guns, therefore, could make existing firearms regulations more effective and reduce the social costs associated with gun misuse. Though personalized guns have advantages relative to standard guns in a wide variety of situations, some of the potential benefits of personalized guns could be captured through alternative policy measures.
ARE POLICY RULES BETTER THAN THE DISCRETIONARY SYSTEM IN TAIWAN?
Authors: Cover James Peery , Hueng C. James , Yau Ruey
Published: July 2002

This article investigates whether the Central Bank of China in Taiwan (CBC) would have had a more successful monetary policy during the period 1978:3 to 1999:4 if it had followed an optimal rule rather than the discretionary policies that were actually employed. The article examines the use of three different instruments—the rediscount rate, M2, and reserve money—with several different targets—the growth rate of nominal output, inflation, the percentage change in the exchange rate, and the growth rate of a monetary aggregate. Only 4 of 64 rules considered resulted in a statistically significant improvement in the performance of the Taiwanese economy. Given that this study analyzes the economy of Taiwan with revised data that were not available to the CBC in real time, and given that so few of the rules would have improved the economy's performance, it is concluded that the performance of the CBC has been very good.
A COST‐BENEFIT ANALYSIS OF ENLARGING THE JAPANESE JUDICIAL SYSTEM
Authors: Kinoshita Tomio
Published: July 2002

This article presents a cost‐benefit analysis of enlarging the Japanese judicial system, especially the civil section of District Courts (CSDC). Constructing a simple econometric model of CSDC, the effects of increase of judges on the supply of judicial services and the trial time are analyzed. Then a cost and benefit calculation is done. The basic assumption is that the total benefit of the judicial system is the aggregate of monetary value of a suit (MVS). The main conclusions are: (1) The demand elasticity for a civil trial with respect to trial time is –1.3 to about –1.4, and its income elasticity is 0.95. (2) The supply of civil trials is proportional to the number of judges. (3) Ten‐percent increase of judges will shorten the average trial time by 5.2%. (4) The net benefit of CSDC is estimated to be ¥466 billion per year if the annual discount rate is 10%. (5) Judging from the demand and supply relation, if CSDC is doubled, the net increase of total benefit per year will be ¥543 billion. (6) If the benefit of the external effect on lawyers' market is added, the total net benefit will reach almost ¥1 trillion, which is 0.22% of gross domestic product.
Octopamine: a new feeding modulator in Lymnaea
Authors: Vehovszky Á , Elliott C. J. H. , Voronezhskaya E. E. , Hiripi L. , Elekes K.
Published: July 2002

The role of octopamine (OA) in the feeding system of the pond snail,Lymnaea stagnalis, was studied by applying behavioural tests on intact animals, and a combination of electrophysiological analysis and morphological labelling in the isolated central nervous system. OA antagonists phentolamine, demethylchlordimeform (DCDM) and 2–chloro–4–methyl–2–(phenylimino)–imidazolidine (NC–7) were injected into intact snails and the sucrose–induced feeding response of animals was monitored. Snails that received 25–50 mg kg-1phentolamine did not start feeding in sucrose, and the same dose of NC–7 reduced the number of feeding animals by 80–90% 1–3 hours after injection. DCDM treatment reduced feeding by 20–60%. In addition, both phentolamine and NC–7 significantly decreased the feeding rate of those animals that still accepted food after 1–6 hours of injection. In the central nervous system a pair of buccal neurons was identified by electrophysiological and morphological criteria. After double labelling (intracellular staining with Lucifer yellow followed by OA–immunocytochemistry) these neurons were shown to be OA immunoreactive, and electrophysiological experiments confirmed that they are members of the buccal feeding system. Therefore the newly identified buccal neurons were called OC neurons (putative OA containing neurons or OAergic cells). Synchronous intracellular recordings demonstrated that the OC neurons share a common rhythm with feeding neurons either appearing spontaneously or evoked by intracellularly stimulated feeding interneurons. OC neurons also have synaptic connections with identified members of the feeding network: electrical coupling was demonstrated between OC neurons and members of the B4 cluster motoneurons, furthermore, chemically transmitted synaptic responses were recorded both on feeding motoneurons (B1, B2 cells) and the SO modulatory interneuron after the stimulation of OC neurons. However, elementary synaptic potentials could not be recorded on the follower cells of OC neurons. Prolonged (20 to 30 s) intracellular stimulation of OC cells activated the buccal feeding neurons leading to rhythmic activity pattern (fictive feeding) in a way similar to OA applied by perfusion onto isolated central nervous system (CNS) preparations. Our results suggest that OA acts as a modulatory substance in the feeding system ofLymnaea stagnalisand the newly identified pair of OC neurons belongs to the buccal feeding network.
Conventional immunosuppression and co-stimulation blockade
Authors: Adams Andrew B. , Pearson Thomas C. , Larsen Christian P.
Published: July 2002

Organ transplantation has become an accepted and successful therapeutic intervention for many patients with end–stage organ disease. Current conventional immunosuppressive regimens achieve very good short–term allograft survival but long–term outcomes are less than adequate. Furthermore, non–specific immunosuppression has its attendant side–effects including increased risks of malignancy and infection as well as drug–specific sequellae. With recent advances in the field of immunology, promising new therapies have arisen that could potentially eliminate lifelong drug therapy and promote indefinite acceptance of the donor tissue. Identification of co–stimulatory signals essential for T–cell activation has provided exciting new possibilities for controlling the alloimmune response. The compatibility of these new agents with proven conventional therapeutics has yielded mixed results. When used in combination, their immunosuppressive properties appear synergistic. However, if the goal of therapy is sustained, specific T–cell hyporesponsiveness, many conventional agents antagonize the effects of co–stimulatory blockade in several immune tolerance models.
New directions for migration policy in Europe
Authors: Laczko Frank
Published: July 2002

There is a growing debate about the future direction of migration policy in Europe. After nearly 30 years of pursuing restrictive immigration and asylum policies, many European Union (EU) governments are beginning to re–assess their migration policies and to call for a new approach. For the first time in many years, several EU governments have begun to talk again about the benefits of labour migration and, even more significantly, have even begun to take action to recruit more migrants, especially skilled workers. This paper looks at the background to current calls for a new approach to migration in Europe and public reaction to these new initiatives. It first describes recent trends in migration in Europe and then briefly considers the demographic case for more migration. This is followed by a brief outline of some of the measures being considered by European governments to promote selective labour migration. The remainder of the paper is devoted to a discussion of some of the implications of this change in policy, focusing on two main issues: the likely consequences for sending countries, and the implications for the fight against the smuggling and trafficking of people.
Mammographic imaging with a small format CCD‐based digital cassette: Physical characteristics of a clinical system
Authors: Vedantham Srinivasan , Karellas Andrew , Suryanarayanan Sankararaman , Levis Ilias , Sayag Michel , Kleehammer Robert , Heidsieck Robert , D'Orsi Carl J.
Published: July 2002

The physical characteristics of a clinical charge coupled device (CCD)‐based imager (Senovision, GE Medical Systems, Milwaukee, WI) for small‐field digital mammography have been investigated. The imager employs a MinR 2000™ (Eastman Kodak Company, Rochester, NY) scintillator coupled by a 1:1 optical fiber to a front‐illuminated CCD operating at a pixel pitch of 30 microns. Objective criteria such as modulation transfer function (MTF), noise power spectrum (NPS), detective quantum efficiency (DQE), and noise equivalent quanta (NEQ) were employed for this evaluation. The results demonstrated a limiting spatial resolution (10% MTF) of 10 cy/mm. The measured DQE of the current prototype utilizing a 28 kVp, Mo–Mo spectrum beam hardened with 4.5 cm Lucite is ∼40% at close to zero spatial frequency at an exposure of 8.2 mR, and decreases to ∼28% at a low exposure of 1.1 mR. Detector element nonuniformity and electronic gain variations were not significant after appropriate calibration and software corrections. The response of the imager was linear and did not exhibit signal saturation under tested exposure conditions.
Improved contralateral subtraction images by use of elastic matching technique
Authors: Li Qiang , Katsuragawa Shigehiko , Doi Kunio
Published: July 2002

A contralateral subtraction technique has been developed to assist radiologists in the detection of asymmetric abnormalities such as lung nodules on a single chest radiograph. With this technique, a contralateral subtraction image is obtained by subtracting a right/left reversed “mirror” image from the original one. The lesions in the subtraction image may be enhanced because most of the symmetric skeletal structures, such as peripheral ribs, are eliminated. Although the quality of the previous contralateral subtraction images is relatively good, severe misregistration artifacts, mainly due to serious asymmetry of the ribs in the two lungs of the original image, were observed in some cases, and minor misregistration artifacts were also observed in many cases. In this study, we employed three image warping techniques. An initial global warping technique was applied to reduce severe misregistration artifacts in the subtraction image caused by asymmetric rib structures. Additional two iterative warping techniques based on an elastic matching technique were used for accurate registration of the local structures of ribs, so that minor artifacts present in many subtraction images obtained with the previous technique were greatly reduced. With the new technique, the percentage of chest images, which were rated as being of adequate, good, or excellent quality of subtraction images by use of a subjective evaluation method, was improved from 91% to 97%. In particular, the number of cases with excellent quality was greatly increased from 15% to 42%. The contralateral subtraction technique can be used for detection of asymmetric abnormalities, such as lung nodules, pneumothorax, pneumonia, and emphysema, on peripheral lungs in single chest radiographs, and it therefore has potential utility in a large proportion of abnormal chest images.
Compensation of x‐ray beam penumbra in conformal radiotherapy
Authors: Sharpe M. B. , Miller B. M. , Wong J. W.
Published: July 2002

In radiotherapy, the gross tumor volume is surrounded by a clinically defined margin to allow for the presence of undetected malignant cells. Additional margins are added to accommodate positioning uncertainties and organ motion, creating a planning target volume, or PTV. Finally, a margin is included in the beam apertures surrounding the PTV to account for the dose fall‐off at the beam edges (i.e., the “penumbra”). For higher energy beams and for low density tissues adjacent to the PTV, the beam aperture margin should be increased to account for the increased range of scattered photons and electrons. However, increased margins also increase the volume of normal tissue irradiated. In this work, the beam aperture margin is reduced by using filters and multileaf collimator (MLC) techniques to create compensating rinds of increased beam intensity. These compensation techniques were evaluated for 6 and 18 MV x rays by calculating penumbral widths as a function of the increased beam intensity in the rind, the rind width, and tissue density. Dose calculations were performed using a 3D superposition algorithm, which includes an extrafocal source model. Calculations were validated experimentally with film dosimetry. Results show the distance between the 95%–50% isodose lines is reduced from 11 mm to 4 mm for 6 MV x rays in the lung phantom, when the beam intensity is increased by 20% in a 10 mm wide rind. At 18 MV, this distance is reduced from 16 mm to 6 mm with a 20% increase in rind intensity, but a 15 mm wide rind is required. In all cases, penumbra compensation did not result in any appreciable increase in scatter dose outside the field boundaries. These results suggest that penumbra compensation is a practical means of controlling the beam aperture margin.
A computerized analysis of masses on mammograms (in Japanese)
Authors: Goto Miki
Published: July 2002

Two new schemes for analysis of mammographic images were developed, a diagnostic logic for classifying masses on mammograms and a multistage pendulum filter for detecting spicules around the mass. To construct a computer‐aided diagnosis scheme for detecting breast cancer requires a knowledge of the diagnostic process. We investigated the classification logic for the diagnosis of breast masses on mammograms in cooperation with a radiologist specialized in mammography. We tested our classification logic by use of 99 mammograms in which the diagnosis had been confirmed. The accuracy for classifying the mass as malignant or benign was very high (sensitivity of 84% and specificity of 96%). Existence of spicules around a mass is one of the important signs which characterize malignant tumors. We developed an automated method for detecting spicules. The detection was performed with a newly developed “multistage pendulum filter.” A “spicule value,” which indicates the probability of “spicule presence” around the mass, was calculated. This filter was evaluated on 71 digitized mammograms. Digitized mammograms were obtained with a laser film scanner with a 0.1 mm×0.1 mm pixel size and 1024 gray levels. The digitized data were then reduced to image with effective pixel size of 0.2 mm for detecting spicules. It detected most of the spicules seen by a radiologist. The sensitivity was 89% and the specificity was 80%, which demonstrates the effectiveness of our method.
Modification and benchmarking of MCNP for low‐energy tungsten spectra
Authors: Mercier J. R. , Kopp D. T. , McDavid W. D. , Dove S. B. , Lancaster J. L. , Tucker D. M.
Published: July 2002

The MCNP Monte Carlo radiation transport code was modified for diagnostic medical physics applications. In particular, the modified code was thoroughly benchmarked for the production of polychromatic tungsten x‐ray spectra in the 30–150 kV range. Validating the modified code for coupled electron–photon transport with benchmark spectra was supplemented with independent electron‐only and photon‐only transport benchmarks. Major revisions to the code included the proper treatment of characteristic K x‐ray production and scoring, new impact ionization cross sections, and new bremsstrahlung cross sections. Minor revisions included updated photon cross sections, electron–electron bremsstrahlung production, and K x‐ray yield. The modified MCNP code is benchmarked to electron backscatter factors, x‐ray spectra production, and primary and scatter photon transport.
Dose distribution along the transverse axis of a new source for interstitial brachytherapy
Authors: Nath Ravinder , Yue Ning
Published: July 2002

A new encapsulated source of has been introduced for interstitial brachytherapy. This source, isoSTAR™ model 12501 (manufactured by Imagyn Corp.), consists of a welded titanium tube containing as silver iodide uniformly coated on five silver beads. The dose rate constant and the radial dose function for this source were measured using lithium fluoride thermoluminescent dosimeters in a Solid Water® phantom. The value of the dose rate constant is where the unit of air kerma strength is The air kerma strength was traceable to the year 2000 primary air kerma strength standard for the model 12501 source at the National Institute of Technology and Standards. The radial dose function for the source was very similar to that for the model 6711 source (manufactured by Nycomed Amersham) for radial distances up to 6 cm. However, the radial dose function is lower in value than that for the model 6702 source (manufactured by Nycomed Amersham) and the model MED3631‐A/M Iogold source (manufactured by North American Scientific).
Image quality evaluation of a desktop computed radiography system
Authors: Fetterly Kenneth A. , Hangiandreou Nicholas J.
Published: July 2002

The modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) of the Lumisys ACR‐2000 desktop computed radiography (CR) reader were measured and compared to equivalent measurements acquired from a Fuji AC‐3 CR system. The one‐dimensional (1D) MTF was measured from an image of a sharp edge and the 1D NPS was derived from a 2D NPS measured from a uniform field exposure. The energy dependent ideal input signal to noise ratio of the incident x‐ray beams was estimated using published x‐ray spectra and attenuation coefficients. Measurements were acquired using Agfa, Fuji, and Kodak storage phosphor plates and it was concluded that use of the Fuji plates resulted in the highest system DQE for the ACR‐2000. The DQE was measured using exposures of 0.10, 1.0, and 10.0 mR from 70 and 120 kVp x‐ray beams filtered with aluminum. The DQE of the Lumisys ACR‐2000 was lower than that of the Fuji AC‐3.
An improved method for rapid objective measurement of gamma camera resolution
Authors: Hander Trish A. , Lancaster Jack L. , McDavid William , Kopp David T.
Published: July 2002

An improved method for an easy, rapid measurement of the intrinsic spatial resolution of a gamma camera is presented. A simplified model was previously developed based solely on mean and standard deviation measurements taken from a region of interest in bar pattern images. This led to an estimate of the modulation transfer function and the full width at half maximum (FWHM) of a line spread function (LSF). The improved method involved expanding the simplified model to incorporate input modulation, square wave input versus the assumed sinusoidal input, aperture (pixel) size, and scatter from the plastic in the bar pattern. The input square wave modulation was calculated to be unity for the typical bar patterns used for gamma camera quality control assessment. For the typical range of bar sizes available, in combination with the typical resolving capabilities of gamma cameras, the sinusoidal approximation of the bar pattern was found to be valid contribution to the measured resolution from higher harmonic frequencies present in a square wave input with an effective input modulation greater than unity by a factor of 4/π). The aperture correction factor was calculated for numerous bar and pixel size combinations. Applying the aperture correction factor results in an improvement in the accuracy of the calculated FWHM values, especially for large apertures (pixel sizes). For a camera with a specified FWHM value of 3.5 mm, the simplified model predicts values ranging from 3.2 to 4.1 mm, when the acquisition matrix varies from to When the expanded model is used with the aperture correction applied, this range was reduced to 3.6–3.9 mm. The scatter correction further improved the calculated FWHM (from 3.6 to 3.8 mm). It is suggested that the expanded model should be used when more accurate measurements are desired, such as in acceptance testing.
Cascade analysis for medical imaging detectors with stages involving both amplification and dislocation processes
Authors: Lachaine M. , Fallone B. G.
Published: July 2002

Cascade analysis is a powerful tool which can be used to calculate the signal and noise properties of medical imaging detectors. It involves the conceptual separation of the imaging chain into stages which consist of either pure amplification or pure dislocation stages. It is, however, not always possible to break the physical processes down to these elementary stages. In this work we derive a new cascade equation which is applicable to any stage which involves multiple amplifications and dislocations. The equation simplifies to the known equations for pure amplification and pure dislocation stages in the appropriate limits, and can be numerically calculated using Monte Carlo techniques for more complicated situations. We demonstrate the use of this equation with an example: we derive an expression for the DQE of a metal/phosphor detector for megavoltage imaging with our formalism, and evaluate the expression with Monte Carlo techniques. We have found that there is excellent agreement between theory and experimental results, and believe that the formalism could be useful for other applications where the amplification and dislocation processes cannot be divided into elementary stages.
A constrained formulation for the receiver operating characteristic (ROC) curve based on probability summation
Authors: Swensson Richard G. , King Jill L. , Gur David
Published: July 2002

We propose a principled formulation of the ROC curve that is constrained in a realistic way by the mechanism of probability summation. The constrained and conventional ROC formulations were fitted to 150 separate sets of rating data taken from previous observer studies of 250 or 529 chest radiographs. A total of 20 different readers had used either discrete or continuous rating scales to evaluate those chest cases for likelihood of separate specified abnormalities: interstitial disease, pulmonary nodule, pneumothorax, alveolar infiltrate, or rib fracture. Both ROC formulations were fitted separately to every set of rating data using maximum‐likelihood statistical procedures that specified each ROC curve by normally distributed latent variables with two scaling parameters, and estimated the area below the ROC curve with its standard error. The conventional and constrained binormal formulations usually fitted ROC curves that were nearly indistinguishable in form and in But when fitted to asymmetric rating data that contained few false‐positive cases, the conventional ROC curves often rose steeply, then flattened and extrapolated into an unrealistic upward “hook” at the higher false‐positive rates. For those sets of rating data, the constrained ROC curves (without hooks) estimated larger values for with smaller standard errors. The constrained ROC formulation describes observers' ratings of cases at least as well as the conventional ROC, and always guarantees a realistic fitted curve for observer performance. Its estimated parameters are easy to interpret, and may also be used to predict observer accuracy in localizing the image abnormalities.
Evaluating the effectiveness of a longitudinal magnetic field in reducing underdosing of the regions around upper respiratory cavities irradiated with photon beams—A Monte Carlo study
Authors: Wadi‐Ramahi Shada J. , Naqvi Shahid A. , Chu James C. H.
Published: July 2002

The problem of underdosing lesions adjacent to upper respiratory cavities and a proposal to correct it are presented in this work. The EGS4 Monte Carlo code was used to simulate a 6 MV x‐ray beam passing through a block of tissues with air cavities 2, 4, and 6 cm wide. The geometry used approximates the tracheal geometry used by previous researchers who investigated the underdosing phenomenon. A uniform longitudinal magnetic field of 0.5 T strength is used to reduce secondary electron outscatter caused by the presence of an air gap, and thus improving the dose at the distal surface of air cavities. We introduce the term “percent dose reduction” (PDR), which is defined as the difference between the dose after the air cavity and the dose at the same depth in soft‐tissue phantom normalized to the dose in the tissue phantom, to quantify the reduction in dose after an air gap. We also introduce the term dose improvement ratio (DIR), which is defined as the dose ratio with magnetic field to the dose, at the same point, without magnetic field, to quantify the improvement in dose when the magnetic field is applied. For and air cavities irradiated by beams, we found PDRs of 38% and 52%, respectively. This means that for these cavities, there is a 38% and a 52% reduction in dose at the cavity edge compared to the same dose in tissue at the same depth for each cavity. The dose improved by and respectively, when applying the magnetic field. The worst effect on dose at the distal side came from larger cavities irradiated with small fields. In these situations, the improvement in dose due to the presence of magnetic field was the largest. This article deals with “ideal” head and neck geometries with a uniform magnetic field. In a paper to follow we will use a CT‐based phantom to study the effect in realistic geometries with the presence of a magnetic field from a Helmholtz coil pair.
On few‐view tomographic reconstruction with megavoltage photon beams
Authors: Loose Stephen , Leszczynski Konrad W.
Published: July 2002

Currently portal imaging devices are used to obtain information on patient localization during radiation therapy treatments. Such obtained information is two dimensional in nature, limited to the plane of the captured image. It has been proposed that megavoltage computed tomography images be reconstructed to overcome this limitation. This study explores the feasibility of reconstructing tomographic images from fan‐beam projection data acquired with a commercial portal imaging device on a standard radiotherapy linear accelerator. Several CT reconstruction algorithms are examined as to their performance and suitability for applications in radiation therapy verification. The results show that it is possible, using some of the iterative reconstruction techniques, to obtain an image useful for patient localization from only several (⩽10) projection views.
Noise aliasing in interline‐video‐based fluoroscopy systems
Authors: Lai H. , Cunningham I. A.
Published: July 2002

Video‐based imaging systems for continuous (nonpulsed) x‐ray fluoroscopy use a variety of video formats. Conventional video‐camera systems may operate in either interlaced or progressive‐scan modes, and CCD systems may operate in interline‐ or frame‐transfer modes. A theoretical model of the image noise power spectrum corresponding to these formats is described. It is shown that with respect to frame‐transfer or progressive‐readout modes, interline or interlaced cameras operating in a frame‐integration mode will result in a spectral shift of 25% of the total image noise power from low spatial frequencies to high. In a field‐integration mode, noise power is doubled with most of the increase occurring at high spatial frequencies. The differences are due primarily to the effect of noise aliasing. In interline or interlaced formats, alternate lines are obtained with each video field resulting in a vertical sampling frequency for noise that is one half of the physical sampling frequency. The extent of noise aliasing is modified by differences in the statistical correlations between video fields in the different modes. The theoretical model is validated with experiments using an x‐ray image intensifier and CCD‐camera system. It is shown that different video modes affect the shape of the noise‐power spectrum and therefore the detective quantum efficiency. While the effect on observer performance is not addressed, it is concluded that in order to minimize image noise at the critical mid‐to‐high spatial frequencies for a specified x‐ray exposure, fluoroscopic systems should use only frame‐transfer (CCD camera) or progressive‐scan (conventional video) formats.