bluuebunny/crossref_metadata_2025 huggingface dataset:
Neurologic Wilson's disease
Authors: Lorincz Matthew T.
Published: November 2009

Despite a long history, Wilson's disease, an autosomal recessive disease caused by mutations in the ATP7B gene, remains a commonly misdiagnosed import disease. Mutations in ATP7B result in abnormal copper metabolism and subsequent toxic accumulation of copper. Clinical manifestations of neurologic Wilson's disease include variable combinations of dysarthria, dystonia, tremor, and choreoathetosis. Among neurodegenerative diseases, it is unusual in that misdiagnosis and delay in treatment are clinically relevant because treatments can prevent and cure Wilson's disease, if they are given appropriately. If left untreated, Wilson's disease progresses to hepatic failure or severe neurologic disability and death, while those adequately treated have normal life spans. This review focuses on the neurologic features of Wilson's disease, its diagnosis, and treatment options.
Sleep disorders in children
Authors: Hoban Timothy F.
Published: November 2009

Although sleep disorders such as insomnia and obstructive sleep apnea are common in both children and adults, the clinical features and treatments for these conditions differ considerably between these two populations. Whereas an adult with obstructive sleep apnea typically presents with a history of obesity, snoring, and prominent daytime somnolence, a child with the condition is more likely to present with normal body weight, tonsillar hypertrophy, and inattentiveness during school classes. The adult with suspected sleep apnea almost always undergoes a baseline polysomnogram and proceeds to treatment only if this test confirms the diagnosis, while many children with suspected sleep apnea are treated empirically with adenotonsillectomy without ever receiving a sleep study to verify the diagnosis. This article reviews sleep disorders in children, with a particular focus on age‐related changes in sleep, conditions that primarily affect children, and disorders for which clinical manifestations and treatment differ substantially from the adult population.
Lewy body pathology in fetal grafts
Authors: Chu Yaping , Kordower Jeffrey H.
Published: November 2009

Although fetal nigral transplants have been shown to survive grafting into the striatum, increased [18F]6‐fluroro‐l‐3,4‐dihydroxyphenylalanine (18F‐DOPA) uptake and improved motor function in open‐label assessments have failed to establish any clinical benefits in double‐blind, sham‐controlled studies. To understand morphological and neurochemical alterations of grafted neurons, we performed postmortem analyses on six Parkinson's disease (PD) patients who had received fetal tissue transplantation 18–19 months, 4 years, and 14 years previously. These studies revealed robust neuronal survival with normal dopaminergic phenotypes in 18‐month‐old grafts and decreased dopamine transporter and increased cytoplasmic α‐synuclein in 4‐year‐old grafts. We also found a decline of both dopamine transporter and tyrosine hydroxylase and the formation of Lewy body–like inclusions in 14‐year‐old grafts, which stained positive for α‐synuclein and ubiquitin proteins. These pathological changes suggest that PD is an ongoing process that affects grafted cells in the striatum in a manner similar to how resident dopamine neurons are affected in the substantia nigra.
AIDS Exceptionalism: On the Social Psychology of HIV Prevention Research
Authors: Fisher William A. , Kohut Taylor , Fisher Jeffrey D.
Published: November 2009

The current analysis considers the human immunodeficiency virus (HIV) prevention research record in the social sciences. We do so with special reference to what has been termed “AIDS Exceptionalism”—departures from standard public health practice and prevention research priorities in favor of alternative approaches to prevention that, it has been argued, emphasize individual rights at the expense of public health protection. In considering this issue, we review the historical context of the HIV epidemic; empirically demonstrate a pattern of prevention research characterized by systematic neglect of prevention interventions for HIV‐infected persons; and articulate a rationale for “Prevention for Positives,” supportive prevention efforts tailored to the needs of HIV+ individuals. We then propose a social psychological conceptualization of processes that appear to have influenced developments in HIV prevention research and directed its focus to particular target populations. Our concluding section considers whether there are social and research policy lessons to be learned from the record of HIV prevention research that might improve our ability to address effectively, equitably, and in timely fashion future epidemics that play out, as HIV does, at the junction of biology and behavior.
Investigating Attitudes Toward International Students: Program and Policy Implications for Social Integration and International Education
Authors: Ward Colleen , Masgoret Anne‐Marie , Gezentsvey Michelle
Published: November 2009

International education is a thriving industry, but relatively little is known about its consequences for the social integration of international scholars in educational institutions or the wider community. This article reviews research on attitudes toward international students as a key component of intercultural relations and a significant marker of social cohesion. An organizational framework for the investigation of these attitudes is proposed with threat mediating the influences of personal and situational factors on attitudinal outcomes. Broader contextual factors are also seen to exert influence on the process of attitude development and maintenance. A model derived from this framework is then tested with student, teacher, and community samples. A “tipping point” in attitudes toward international students as a function of the proportion of international enrolments in educational institutions is also explored. Finally, the applicability of the findings for promoting social cohesion in educational institutions and the wider community is discussed.
The Effects and Effectiveness of Using Torture as an Interrogation Device: Using Research to Inform the Policy Debate
Authors: Costanzo Mark A. , Gerrity Ellen
Published: November 2009

Governments sometimes characterize torture as an indispensable interrogation tool for gathering strategic intelligence. In this article, we review the relevant social scientific research on the effectiveness, impact, and causes of torture. First, we summarize research on false confessions and examine the relevance of that research for torture‐based interrogations. Next, we review research on the mental health consequences of torture for survivors and perpetrators. Finally, we explore the social‐psychological conditions that promote acts of cruelty (such as those seen at Abu Ghraib) and examine the arguments typically offered to justify the use of torture. We argue that any hypothesized benefits from the use of torture must be weighed against the substantial proven costs of torture. These costs include the unreliable information extracted through interrogations using torture, the mental and emotional toll on victims and torturers, loss of international stature and credibility, and the risk of retaliation against soldiers and civilians.
The Food Marketing Defense Model: Integrating Psychological Research to Protect Youth and Inform Public Policy
Authors: Harris Jennifer L. , Brownell Kelly D. , Bargh John A.
Published: November 2009

Marketing practices that promote calorie‐dense, nutrient‐poor foods directly to children and adolescents present significant public health risk. Worldwide, calls for government action and industry change to protect young people from the negative effects of food marketing have increased. Current proposals focus on restricting television advertising to children under 12 years old, but current psychological models suggest that much more is required. All forms of marketing pose considerable risk; adolescents are also highly vulnerable; and food marketing may produce far‐reaching negative health outcomes. We propose a food marketing defense model that posits four necessary conditions to effectively counter harmful food marketing practices: awareness, understanding, ability, and motivation to resist. A new generation of psychological research is needed to examine each of these processes, including the psychological mechanisms through which food marketing affects young people, to identify public policy that will effectively protect them from harmful influence.
The impact of asymmetric regulation on surplus and welfare: the case of gas release programmes
Authors: Clastres Cédric , David Laurent
Published: November 2009

Gas release programmes, or capacities release, and market shares constraints are the two asymmetric regulations imposed on incumbents in energy markets. In this paper, we focus on gas release, its impact on welfare or consumer surplus and on the optimal level of released quantities set by regulators. We use a Cournot model with capacity constraints in order to study gas release and we put forward two conclusions. First, we compute the impact of these strategies on consumer surplus and welfare. We show that there is no impact on consumer surplus, but welfare can decrease as gas release can induce raising rival's costs (RRC) or ‘self‐sabotage’ strategies. Then, we demonstrate that the regulator must set released quantities according to the information held on the incumbent's supplies to maximise welfare. Finally, we conclude that the regulator can avoid RRC or self‐sabotage strategies by setting gas‐released quantities. As proven from empirical studies, these quantities should not be too high so that a significant difference between capacities of both competitor and incumbent make it possible to avoid collusive behaviours.
Control of Moderate‐to‐Severe Plaque Psoriasis with Efalizumab: 24‐Week, Open‐Label, Phase IIIb/IV Latin American Study Results
Authors: Stengel Fernando M. , Petri Valeria , Campbell Gladys A.M. , Dorantes Gladys Leon , López Magdalina , Galimberti Ricardo L. , Valdez Raúl P. , De Arruda Lucia F. , Guerra Mario Amaya , Chouela Edgardo N. , Licu Daiana ,   International IMP25161 Study Group
Published: November 2009

Introduction.  Psoriasis is a debilitating, chronic inflammatory systemic disease affecting around 2% of the South American population. Biological therapies offer the possibility of long‐term therapy with improved safety and efficacy.

Methods.  We conducted a multicentre, open‐label, single‐arm, Phase IIIb/IV study of adult patients (18–75 years) with moderate‐to‐severe plaque psoriasis who were candidates for systemic therapy or phototherapy. Patients received efalizumab subcutaneously (1.0 mg/kg/wk). The primary endpoint was the proportion of patients achieving a Physician Global Assessment (PGA) rating of “excellent” or “cleared” at Week 24. Safety outcomes were adverse events (AEs), serious AEs (SAEs) and abnormalities on laboratory tests.

Results.  Of 189 patients included in the intent‐to‐treat and safety populations, 104 (55.0%) were of Hispanic or Latino ethnicity. At Week 24, 92/189 (48.7%) patients achieved or maintained a PGA rating of “excellent” or “cleared”. AEs were reported by 161/189 (85.2%) patients, SAEs by 21/189 (11.1%). One patient died during the study (meningoencephalitis). Laboratory findings were consistent with previous experience.

Conclusions.  Efalizumab demonstrated sustained control of psoriasis up to 24 weeks in patients from Latin America, confirming results seen in Phase III studies conducted in North America and Europe.
Antagonists of ionotropic γ‐aminobutyric acid receptors impair the NiCl2‐mediated stimulation of the electroretinogram b‐wave amplitude from the isolated superfused vertebrate retina
Authors: Siapich Siarhei A , Banat Mohammed , Albanna Walid , Hescheler Jürgen , Lüke Matthias , Schneider Toni
Published: November 2009

Purpose:  NiCl2 (15 μM) stimulates the electroretinogram (ERG) b‐wave amplitude of vertebrate retina up to 1.5‐fold through its blocking of E/R‐type voltage‐gated Ca2+ channels. Assuming that such an increase is mediated by blocking the release of the inhibitory neurotransmitter γ‐aminobutyric acid (GABA) via ionotropic GABA receptors, we tested the effect of both GABA itself and GABA‐receptor antagonists such as (−)bicuculline (1.51‐fold increase) and (1,2,5,6‐tetrahydropyridin‐4‐yl)methylphosphinic acid (TPMPA; 1.46‐fold increase) on the b‐wave amplitude.

Methods:  Recording of the transretinal potentials from the isolated bovine retina.

Results:  GABA (100 μM) reduced the b‐wave amplitude only when NiCl2 (15 μM) was applied first. Each antagonist applied on its own stimulated the b‐wave amplitude only partially: subsequent NiCl2 superfusion caused a small but additional increase, leading to a 1.69‐ and a 1.88‐fold total increase of the amplitude by Ni2+ plus (−)bicuculline or Ni2+ plus TPMPA, respectively. Only the application of both antagonists in combination, before superfusing low NiCl2 (15 μM), completely prevented subsequent stimulation by NiCl2 with a similar 1.90‐fold total increase of b‐wave amplitude. Those retina segments that did not respond to NiCl2 could not be stimulated by (−)bicuculline and vice versa.

Conclusion:  The stimulatory effect of NiCl2 on the ERG b‐wave amplitude is mainly, but not only, mediated by a NiCl2‐sensitive, Cav2.3‐triggered GABA release acting through ionotropic GABA‐A and GABA‐C receptors.
A new invasive method of measuring pulsatile ocular blood flow
Authors: DASTIRIDOU AI , TSILIMBARIS MK , GINIS HS , DE BROUWERE D , PALLIKARIS IG
Published: November 2009

Purpose The purpose of this study is to demonstrate proof of principle of a new rigidity based invasive technique to assess pulsatile ocular blood flow in a wide range of clinically relevant IOP levels.

Methods An invasive manometric dynamic measurement procedure is employed, using a computer controlled device, comprising a pressure transducer and a microdosimetric pump. The anterior chamber is cannulated under topical anaesthesia with drops with a 21 gauge needle and the initial IOP is recorded. The IOP is artificially set to 10 mmHg and the eye is infused with predetermined volumes of BSS in a stepping sequence. After each infusion step, the IOP is continuously recorded for 2 sec, in order to calculate the pulsatile change in IOP. Ocular rigidity is measured from the pressure volume relationship in the stepping sequence. Pulsatile Ocular Blood Flow (POBF) is obtained through algorithms converting the IOP readings to the corresponding change of ocular volume derived from the rigidity diagram. Forty eyes of 40 cataract patients were measured with this technique. The study was approved by the Institutional Board and performed under the patient’s informed consent. Systemic blood pressure and pulse rate were monitored during the measurement.

Results There were no complications related to the procedure. The average Friedenwald’s Rigidity Coefficient was 0.0206 mmHg/μL (SD=0.0054). The corresponding POBF was 888(SD=185) μL/min at 15mmHg decreasing to 548(SD=146) μL/min at 40mmHg.

Conclusion The invasive method described is safe and effective. It can provide accurate estimates of POBF by incorporating the individual eye’s measured rigidity coefficient. Moreover, POBF can be estimated in relation to the IOP.
EQUIVALENCE OF COMPETITION MODE IN A VERTICALLY DIFFERENTIATED DUOPOLY WITH DELEGATION
Authors: Wang Ya‐chin , Wang Leonard F.s.
Published: November 2009

This paper aims to examine the equivalence of competition mode in a vertically differentiated product market with the relative performance delegation. It demonstrates the equivalence of product quality and social welfare in this delegation game, irrespective of modes of product competition. In addition, in a three‐stage game of quality‐delegation‐quantity (or price), it shows that the delegation coefficient is different between high‐quality and low‐quality firms in an asymmetric vertical differentiated model, and a high‐quality firm makes better use of the delegation than a low‐quality firm.
CAPITAL CONTROLS, TWO‐TIERED EXCHANGE RATE SYSTEMS AND EXCHANGE RATE POLICY: THE SOUTH AFRICAN EXPERIENCE
Authors: Schaling Eric
Published: November 2009

South Africa's 40 years of experience with capital controls on residents and non‐residents (1961‐2001) reads like a collection of examples of perverse unanticipated effects of legislation and regulation. We show that the presence of capital controls on residents and non‐residents enabled the South African Reserve Bank to target domestic interest rates (and or the exchange rate) via interventions in the (commercial) foreign exchange market. This provides an early rationale for anchoring SA monetary policy via the exchange rate, rather than via domestic interest rates. This suggests not only that the capital controls themselves exhibited substantial institutional inertia, but that this same institutional inertia also applied to the monetary policy regime. A plausible reason for this is that for most of the 20th century in South Africa. (partial) capital controls and exchange rate based monetary policies were like Siamese twins – almost impossible to separate.
LIQUIDITY AND VALUATION IN EAST AFRICAN SECURITIES MARKETS
Authors: Hearn Bruce
Published: November 2009

This study estimates liquidity premiums using the recently developed Liu measure within a multifactor capital asset pricing model including size premiums and a time‐varying parameter model for the East African emerging markets of Uganda, Tanzania and Kenya together with London and South Africa. The evidence suggests that while size and liquidity effects are significant in the smaller emerging markets of Uganda and Kenya, they are less important in explaining returns in South Africa and London. Costs of equity are highest in Uganda followed by Kenya, with industrial and consumer non‐cyclical sectors being lowest, and then South Africa and London.
Separating oral burning from burning mouth syndrome: unravelling a diagnostic enigma
Authors: Balasubramaniam R , Klasser GD , Delcanho R
Published: November 2009

Burning mouth syndrome (BMS) is characterized by burning pain in the tongue or other oral mucous membrane often associated with symptoms such as subjective dryness of the mouth, paraesthesia and altered taste for which no medical or dental cause can be found. The difficulty in diagnosing BMS lies in excluding known causes of oral burning. A pragmatic approach in clarifying this issue is to divide patients into either primary (essential/idiopathic) BMS, whereby other disease is not evident or secondary BMS, where oral burning is explained by a clinical abnormality. The purpose of this article was to provide the practitioner with an understanding of the local, systemic and psychosocial factors which may be responsible for oral burning associated with secondary BMS, therefore providing a foundation for diagnosing primary BMS.
Dental caries experience in young Australian Army recruits 2008
Authors: Hopcraft MS , Yapp KE , Mahoney G , Morgan MV
Published: November 2009

Background:  Recent studies have shown a substantial decline in caries experience in Australian Army recruits between 1996 and 2002–2003, and in Australian adults between 1987–1988 and 2004–2006. However, studies in children have reported an increasing trend in caries experience between 1998 and 2002. The aim of this study was to investigate caries experience in Australian Army recruits in 2008.

Methods:  A cross‐sectional study involving 1084 Australian Army recruits was conducted from January to May 2008. Data were obtained from a clinical dental examination with bitewing radiographs, and a questionnaire elicited socio‐demographic data and history on lifetime exposure to fluoridated drinking water.

Results:  Mean DMFT scores were 3.16, 4.08, 5.16 and 7.11 for recruits aged 17–20, 21–25, 26–30 and 31–35 years, respectively. Recruits with a lifetime exposure to fluoridated drinking water had a mean DMFT of 3.02, while recruits with no exposure had a mean DMFT of 3.87.

Conclusions:  Caries experience in Australian Army recruits aged 17–25 years increased between 2002–2003 and 2008. Recruits with lifetime exposure to fluoridated drinking water had 25 per cent less caries experience compared with recruits who had no exposure to fluoridated drinking water after adjusting for the effects of age, gender, education and socio‐economic status.
Comparison of efficacy of fluconazole mouthrinse and clotrimazole mouthpaint in the treatment of oral candidiasis
Authors: Sholapurkar AA , Pai KM , Rao S
Published: November 2009

Candidiasis is by far the most common oral fungal infection in humans and has a variety of clinical features. It is considered to be an opportunistic infection, affecting individuals who are debilitated by another disease. Fluconazole, one of the newer azoles available for systemic use and clotrimazole as a topical ointment are both shown to be effective in the treatment of oral candidiasis and are considered to be well tolerated and useful medications. No study has evaluated the comparison of clinical and mycological response of oral candidiasis to fluconazole mouthrinse and clotrimazole mouthpaint. The aim of this study was to evaluate the efficacy of fluconazole mouthrinse and compare it with clotrimazole mouthpaint in the treatment of oral candidiasis.
Water fluoridation in the Blue Mountains reduces risk of tooth decay
Authors: Evans RW , Hsiau ACY , Dennison PJ , Patterson A , Jalaludin B
Published: November 2009

Background:  In April 1992, the fluoride concentration in the Blue Mountains water supply was adjusted to 1 mg/L. Baseline dmft/DMFT has been determined in children attending schools in the region and in the adjacent reference region of Hawkesbury, fluoridated since 1968. The aim of this study was to evaluate the effect of the water fluoridation programme in the Blue Mountains.

Methods:  In 2003, children attending the same schools were sampled. Residential history data were obtained by questionnaire and caries experience was assessed according to WHO guidelines. The analysis was restricted to lifelong resident children aged 5–11 years.

Results:  The baseline and follow‐up dmft scores for Blue Mountains children aged 5–8 years were 2.36 and 0.67, respectively. The age‐adjusted decrease in odds of experiencing one or more dmft due to fluoridation was 0.26 (CI95 0.19, 0.37). The corresponding DMFT scores for Blue Mountains children aged 8–11 were 0.76 and 0.21 and the corresponding decrease in odds of experiencing one or more DMFT due to fluoridation was 0.25 (CI95 0.16, 0.40).

Conclusions:  Tooth decay reduction observed in the Blue Mountains corresponds to high rates reported elsewhere and demonstrates the substantial benefits of water fluoridation.
Data-Driven Decision Tree Classification for Product Portfolio Design Optimization
Authors: Tucker Conrad S. , Kim Harrison M.
Published: November 2009

The formulation of a product portfolio requires extensive knowledge about the product market space and also the technical limitations of a company’s engineering design and manufacturing processes. A design methodology is presented that significantly enhances the product portfolio design process by eliminating the need for an exhaustive search of all possible product concepts. This is achieved through a decision tree data mining technique that generates a set of product concepts that are subsequently validated in the engineering design using multilevel optimization techniques. The final optimal product portfolio evaluates products based on the following three criteria: (1) it must satisfy customer price and performance expectations (based on the predictive model) defined here as the feasibility criterion; (2) the feasible set of products/variants validated at the engineering level must generate positive profit that we define as the optimality criterion; (3) the optimal set of products/variants should be a manageable size as defined by the enterprise decision makers and should therefore not exceed the product portfolio limit. The strength of our work is to reveal the tremendous savings in time and resources that exist when decision tree data mining techniques are incorporated into the product portfolio design and selection process. Using data mining tree generation techniques, a customer data set of 40,000 responses with 576 unique attribute combinations (entire set of possible product concepts) is narrowed down to 46 product concepts and then validated through the multilevel engineering design response of feasible products. A cell phone example is presented and an optimal product portfolio solution is achieved that maximizes company profit, without violating customer product performance expectations.
Deformation of Multicomponent Models With Nonmatching Interfaces
Authors: Zhou Aifang , Hui Kinchuen
Published: November 2009

In this paper, a traction superimposition method for simulating the deformation of multicomponent elastic models with different interfacial mesh densities is introduced. By applying linear interpolation method, the displacement data can be transferred between nonconforming interfaces. With the application of energy conservation principle, a relationship between the forces on different surfaces is constructed. By considering the displacement compatibility conditions together with force equilibrium conditions over the common interfaces, a relation between different components of a system is established. However, this interpolation method is only applicable to object components with the same or similar mesh densities. For models with different mesh densities between neighboring components, abnormities arise in the deformation. The causes of these abnormities are parsed by experiments and theoretical analysis. To eliminate the abnormal deformation, a traction superimposition method is proposed to enforce the force constraints on the interfaces. Experimental results are provided to verify this approach.
Identification of breast calcification using magnetic resonance imaging
Authors: Fatemi‐Ardekani Ali , Boylan Colm , Noseworthy Michael D.
Published: November 2009

MRI phase and magnitude images provide information about local magnetic field variation , which can consequently be used to understand tissue properties. Often, phase information is discarded. However, corrected phase images are able to produce contrast as a result of magnetic susceptibility differences and local field inhomogeneities due to the presence of diamagnetic and paramagnetic substances. Three‐dimensional (3D) susceptibility weighted imaging (SWI) can be used to probe changes in MRI phase evolution and, subsequently, result in an alternate form of contrast between tissues. For example, SWI has been useful in the assessment of negative phase induced modulation due to the presence of paramagnetic substances such as iron. Very little, however, has been done to assess positive phase induced contrast changes resulting from the presence of diamagnetic substances such as precipitated calcium. As ductal carcinoma in situ, which is the precursor of invasive ductal cancer, is often associated with breast microcalcification, the authors proposed using SWI as a possible visualization technique. In this study, breast phantoms containing calcifications were imaged using mammography, computed tomography (CT), and SWI. Corrected phase and magnitude images acquired using SWI allowed identification and correlation of all calcifications seen on CT. As the approach is a 3D technique, it could potentially allow for more accurate localization and biopsy and maybe even reduce the use of gadolinium contrast. Furthermore, the approach may be beneficial to women with dense breast tissue where the ability to detect microcalcification with mammography is reduced.
Functional representation of tissue phantom ratios for photon fields
Authors: Sauer Otto A. , Wilbert J.
Published: November 2009

Purpose:

The tissue phantom ratio (TPR) is a common dosimetric quantity used in photon dose calculations. For small photon fields with side lengths less than, TPR data hardly exist in literature. In this work, a self‐contained functional representation of TPR is proposed, valid for the whole range of clinically relevant depth and field sizes. This is especially useful for small fields shaped by multileaf collimators.

Methods:

TPRs were measured for quadratic fields with side lengths between 0.4 and. The measured data were fitted to a physically meaningful function taking electron buildup, buildup of scattered photons, beam attenuation, and beam hardening into account. The achievable accuracy was tested against measurement and data from the literature.

Results:

A set of parameters for the proposed function was derived for 6 and beams. The comparison of the calculated and the measured data generally yielded a difference of less than 1%. For field sizes below , a systematic discrepancy between the author's data and those from Cheng et al. [Med. Phys 34, 3149–3157 (2007)] was found.

Conclusions:

With the proposed model, TPRs can be calculated for the full range of field sizes and depths required by treatment planning system algorithms and monitor unit check programs with very high accuracy. The method is also useful in detecting and reducing errors in measurement.
Development and evaluation of an ultrasound‐guided tracking and gating system for hepatic radiotherapy
Authors: Jacso Ferenc , Kouznetsov Alexei , Smith Wendy L.
Published: November 2009

Purpose:

Respiratory motion must be accounted for daily in order to permit optimum radiotherapy of hepatic malignancies. However, existing tracking systems are often invasive or poorly tolerated by patients. The authors describe the development and validation of an ultrasound‐guided tracking and gating system for stereotactic body radiation therapy of the liver.

Methods:

This noninvasive system is designed to determine the correlation between tumor and external fiducial motion and to verify the optimum gating level for treatment delivery daily. A tracked ultrasound probe moves with patient respiration, obtaining 2D ultrasound images of tumor motion throughout the respiratory cycle. The target volume is registered to the static radiotherapy treatment beams in order to verify optimum gating levels. These gating levels are then transferred to an existing gating system for treatment delivery. The authors examined the temporal and spatial accuracy of this system using a custom‐built phantom and verified the accuracy of gating level transfer and delivery.

Results:

The temporal accuracy of the ultrasound‐guided system was shown to be comparable to the existing clinical x‐ray imaging system. Using ultrasound rather than x‐rays to image internal targets provides good soft‐tissue contrast without the invasiveness of implanting fiducial markers. High frame rates enable continuous monitoring of the target throughout the respiratory cycle. The authors anticipate this passive monitoring system should be well tolerated by patients.

Conclusions:

The system developed provides good quality video of the laboratory motion phantom and can be successfully used in gated beam delivery.
Single x‐ray absorptiometry method for the quantitative mammographic measure of fibroglandular tissue volume
Authors: Malkov Serghei , Wang Jeff , Kerlikowske Karla , Cummings Steven R. , Shepherd John A.
Published: November 2009

Purpose:

This study describes the design and characteristics of a highly accurate, precise, and automated single‐energy method to quantify percent fibroglandular tissue volume (%FGV) and fibroglandular tissue volume (FGV) using digital screening mammography.

Methods:

The method uses a breast tissue‐equivalent phantom in the unused portion of the mammogram as a reference to estimate breast composition. The phantom is used to calculate breast thickness and composition for each image regardless of x‐ray technique or the presence of paddle tilt. The phantom adheres to the top of the mammographic compression paddle and stays in place for both craniocaudal and mediolateral oblique screening views. We describe the automated method to identify the phantom and paddle orientation with a three‐dimensional reconstruction least‐squares technique. A series of test phantoms, with a breast thickness range of 0.5–8 cm and a %FGV of 0%–100%, were made to test the accuracy and precision of the technique.

Results:

Using test phantoms, the estimated repeatability standard deviation equaled 2%, with a ±2% accuracy for the entire thickness and density ranges. Without correction, paddle tilt was found to create large errors in the measured density values of up to 7%/mm difference from actual breast thickness. This new density measurement is stable over time, with no significant drifts in calibration noted during a four‐month period. Comparisons of %FGV to mammographic percent density and left to right breast %FGV were highly correlated ( and 0.94, respectively).

Conclusions:

An automated method for quantifying fibroglandular tissue volume has been developed. It exhibited good accuracy and precision for a broad range of breast thicknesses, paddle tilt angles, and %FGV values. Clinical testing showed high correlation to mammographic density and between left and right breasts.
Number of partitions (gates) needed to obtain motion‐free images in a respiratory gated 4D‐PET/CT study as a function of the lesion size and motion displacement
Authors: Bettinardi V. , Rapisarda E. , Gilardi M. C.
Published: November 2009

Purpose:

In this study we evaluate the number of data partitions (gates) needed to sort 4D‐PET and 4D‐CT data to obtain motion‐free images as a function of lesion size and motion displacement.

Methods:

Plexiglas spheres of various diameters (8, 10, 15, 20, and 25 mm) were filled with a radioactive solution of water and. A PET/CT study was acquired for each sphere in a rest condition to reconstruct a motion‐free image as a reference in terms of radioactivity concentration and spatial distribution. Each sphere was then moved sinusoidally in the superior‐inferior direction over different motion displacements (5, 10, 15, 20, and 25 mm) with a periodic motion of 4 s. During motion a 4D‐CT scan followed by a 4D‐PET scan were acquired. Each set of 4D‐CT and 4D‐PET data was retrospectively sorted to generate one, two, four, six, eight, ten, and 12 partitions (gates) over the whole cycle of motion. 4D‐PET gates were reconstructed by using the corresponding 4D‐CT gates for attenuation correction, while PET data acquired, with the sphere in the rest condition were corrected for attenuation by using the corresponding CT image set. For each series of PET images, data analysis was performed by measuring (1) the maximum value of the radioactivity concentration in a VOI encompassing the radioactivity distribution over the volume of motion and (2) the axial‐profile of the radioactivity distribution (Ax‐p).

Results:

The results show that radioactivity concentration is strongly underestimated due to motion in most conditions considered in this study. In particular, the underestimation of for the smallest sphere varied from −10.6% to −66.3% with motion displacements ranging from 5 to 25 mm. For the largest sphere, errors ranged from −1.4% to −26.7%. The 4D‐PET/CT methodology allows motion‐free or nearly motion‐free images to be obtained. It also permits both radioactivity concentration and Ax‐p to be recovered with residual differences with respect to the rest condition, depending on the number of partitions used to process the data. Within the limitation of the regular sinusoidal motion, used to simulate a general breathing condition, a scheme describing the number of partitions needed to obtain nearly motion‐free images with Ax‐p differences of around 10% with respect to the rest data is presented as a function of the lesion size and motion displacement. Such a scheme is proposed to guide the setup of a 4D‐PET/CT acquisition and processing protocol for clinical applications.

Conclusions:

By using the 4D‐PET/CT acquisition technique, it is possible to compensate for the degradation effect of lesion motion on the reconstructed PET images.
Temporal subtraction in chest radiography: Mutual information as a measure of image quality
Authors: Armato Samuel G. , Sensakovic William F. , Passen Samantha J. , Engelmann Roger , MacMahon Heber
Published: November 2009

Purpose:

Temporal subtraction is used to detect the interval change in chest radiographs and aid radiologists in patient diagnosis. This method registers two temporally different images by geometrically warping the lung region, or “lung mask,” of a previous radiographic image to align with the current image. The gray levels of every pixel in the current image are subtracted from the gray levels of the corresponding pixels in the warped previous image to form a temporal subtraction image. While temporal subtraction images effectively enhance areas of pathologic change, misregistration of the images can mislead radiologists by obscuring the interval change or by creating artifacts that mimic change. The purpose of this study was to investigate the utility of mutual information computed between two registered radiographic chest images as a metric for distinguishing between clinically acceptable and clinically unacceptable temporal subtraction images.

Methods:

A radiologist subjectively rated the image quality of 138 temporal subtraction images using a 1 (poor) to 5 (excellent) scale. To objectively assess the registration accuracy depicted in the temporal subtraction images, which is the main factor that affects the quality of these images, mutual information was computed on the two constituent registered images prior to their subtraction to generate a temporal subtraction image. Mutual information measures the joint entropy of the current image and the warped previous image, yielding a higher value when the gray levels of spatially matched pixels in each image are consistent. Mutual information values were correlated with the radiologist's subjective ratings. To improve this correlation, mutual information was computed from a spatially limited lung mask, which was cropped from the bottom by 10%–60%. Additionally, the number of gray‐level values used in the joint entropy histogram was varied. The ability of mutual information to predict the clinical acceptability of a temporal subtraction image was evaluated through receiver operating characteristic (ROC) analysis.

Results:

The mean correlation coefficient obtained between mutual information computed on constituent images and the subjective rating of temporal subtraction image quality was 0.785. ROC analysis yielded an average value of 0.852 for the ability of mutual information to distinguish between temporal subtraction images of clinically acceptable and clinically unacceptable quality.

Conclusions:

The results of this study establish a relationship between mutual information and temporal subtraction registration accuracy and demonstrate the ability of mutual information to objectively indicate the presence of misregistration artifacts.
High‐DQE EPIDs based on thick, segmented BGO and CsI:Tl scintillators: Performance evaluation at extremely low dose
Authors: Wang Yi , Antonuk Larry E. , Zhao Qihua , El‐Mohri Youcef , Perna Louis
Published: November 2009

Purpose:

Electronic portal imaging devices (EPIDs) based on active matrix, flat‐panel imagers (AMFPIs) have become the gold standard for portal imaging and are currently being investigated for megavoltage cone‐beam computed tomography (CBCT) and cone‐beam digital tomosynthesis (CBDT). However, the practical realization of such volumetric imaging techniques is constrained by the relatively low detective quantum efficiency (DQE) of AMFPI‐based EPIDs at radiotherapy energies, at 6 MV. In order to significantly improve DQE, the authors are investigating thick, segmented scintillators, consisting of 2D matrices of scintillating crystals separated by septal walls.

Methods:

A newly constructed segmented BGO scintillator (11.3 mm thick) and three segmented CsI:Tl scintillators (11.4, 25.6, and 40.0 mm thick) were evaluated using a 6 MV photon beam. X‐ray sensitivity, modulation transfer function, noise power spectrum, DQE, and phantom images were obtained using prototype EPIDs based on the four scintillators.

Results:

The BGO and CsI:Tl prototypes were found to exhibit improvement in DQE ranging from to 25 times that of a conventional AMFPI‐based EPID at zero spatial frequency. All four prototype EPIDs provide significantly improved contrast resolution at extremely low doses, extending down to a single beam pulse. In particular, the BGO prototype provides contrast resolution comparable to that of the conventional EPID, but at 20 times less dose, with spatial resolution sufficient for identifying the boundaries of low‐contrast objects. For this prototype, however, the BGO scintillator exhibited an undesirable radiation‐induced variation in x‐ray sensitivity.

Conclusions:

Prototype EPIDs based on thick, segmented BGO and CsI:Tl scintillators provide significantly improved portal imaging performance at extremely low dose (i.e., down to 1 beam pulse corresponding to), creating the possibility of soft‐tissue visualization using MV CBCT and CBDT at clinically practical dose.
Simulation of large x‐ray fields using independently measured source and geometry details
Authors: Sawkey D. , Faddegon B. A.
Published: November 2009

Purpose:

Obtain an accurate simulation of the dose from the 6 and 18 MV x‐ray beams from a Siemens Oncor linear accelerator by comparing simulation to measurement. Constrain the simulation by independently determining parameters of the treatment head and incident beam, in particular, the energy and spot size.

Methods:

Measurements were done with the treatment head in three different configurations: (1) The clinical configuration, (2) the flattening filter removed, and (3) the target and flattening filter removed. Parameters of the incident beam and treatment head were measured directly. Incident beam energy and spectral width were determined from the percent‐depth ionization of the raw beam (as described previously), spot size was determined using a spot camera, and the densities of the flattening filters were determined by weighing them. Simulations were done with EGSnrc/BEAMnrc code. An asymmetric simulation was used, including offsets of the spot, primary collimator, and flattening filter from the collimator rotation axis.

Results:

Agreement between measurement and simulation was obtained to the least restrictive of 1% or 1 mm at 6 MV, both with and without the flattening filter in place, except for the buildup region. At 18 MV, the agreement was 1.5%/1.5 mm with the flattening filter in place and 1%/1 mm with it removed, except for in the buildup region. In the buildup region, the discrepancy was 2%/2 mm at 18 MV and 1.5%/1.5 mm at 6 MV with the flattening filter either removed or in place. The methodology for measuring the source and geometry parameters for the treatment head simulation is described. Except to determine the density of the flattening filter, no physical modification of the treatment head is necessary to obtain those parameters. In particular, the flattening filter does not need to be removed as was done in this work.

Conclusions:

Good agreement between measured and simulated dose distributions was obtained, even in the buildup region. The simulation was tightly constrained by independent measurements of parameters of the incident beam and treatment head. The method of obtaining the input parameters is described, and can be carried out on a clinical linear accelerator.
Partial scan artifact reduction (PSAR) for the assessment of cardiac perfusion in dynamic phase‐correlated CT
Authors: Stenner Philip , Schmidt Bernhard , Bruder Herbert , Allmendinger Thomas , Haberland Ulrike , Flohr Thomas , Kachelrieß Marc
Published: November 2009

Purpose:

Cardiac CT achieves its high temporal resolution by lowering the scan range from to plus fan angle (partial scan). This, however, introduces CT‐value variations, depending on the angular position of the range. These partial scan artifacts are of the order of a few HU and prevent the quantitative evaluation of perfusion measurements. The authors present the new algorithm partial scan artifact reduction (PSAR) that corrects a dynamic phase‐correlated scan without a priori information.

Methods:

In general, a full scan does not suffer from partial scan artifacts since all projections in [0,] contribute to the data. To maintain the optimum temporal resolution and the phase correlation, PSAR creates an artificial full scan by projectionwise averaging a set of neighboring partial scans from the same perfusion examination (typically phase‐correlated partial scans distributed over and ). Corresponding to the angular range of each partial scan, the authors extract virtual partial scans from the artificial full scan . A standard reconstruction yields the corresponding images , , and . Subtracting the virtual partial scan image from the artificial full scan image yields an artifact image that can be used to correct the original partial scan image: , where is the corrected image.

Results:

The authors evaluated the effects of scattered radiation on the partial scan artifacts using simulated and measured water phantoms and found a strong correlation. The PSAR algorithm has been validated with a simulated semianthropomorphic heart phantom and with measurements of a dynamic biological perfusion phantom. For the stationary phantoms, real full scans have been performed to provide theoretical reference values. The improvement in the root mean square errors between the full and the partial scans with respect to the errors between the full and the corrected scans is up to 54% for the simulations and 90% for the measurements.

Conclusions:

The phase‐correlated data now appear accurate enough for a quantitative analysis of cardiac perfusion.
Autoadaptive phase‐correlated (AAPC) reconstruction for 4D CBCT
Authors: Bergner Frank , Berkus Timo , Oelhafen Markus , Kunz Patrik , Pan Tinsu , Kachelrieß Marc
Published: November 2009

Purpose:

Kilovoltage cone‐beam computed tomography (CBCT) is widely used in image‐guided radiation therapy for exact patient positioning prior to the treatment. However, producing time series of volumetric images (4D CBCT) of moving anatomical structures remains challenging. The presented work introduces a novel method, combining high temporal resolution inside anatomical regions with strong motion and image quality improvement in regions with little motion.

Methods:

In the proposed method, the projections are divided into regions that are subject to motion and regions at rest. The latter ones will be shared among phase bins, leading thus to an overall reduction in artifacts and noise. An algorithm based on the concept of optical flow was developed to analyze motion‐induced changes between projections. The technique was optimized to distinguish patient motion and motion deriving from gantry rotation. The effectiveness of the method is shown in numerical simulations and patient data.

Results:

The images reconstructed from the presented method yield an almost the same temporal resolution in the moving volume segments as a conventional phase‐correlated reconstruction, while reducing the noise in the motionless regions down to the level of a standard reconstruction without phase correlation. The proposed simple motion segmentation scheme is yet limited to rotation speeds of less than.

Conclusions:

The method reduces the noise in the reconstruction and increases the image quality. More data are introduced for each phase‐correlated reconstruction, and therefore the applied dose is used more efficiently.
mTOR Regulation and Therapeutic Rejuvenation of Aging Hematopoietic Stem Cells
Authors: Chen Chong , Liu Yu , Liu Yang , Zheng Pan
Published: November 2009

Rapamycin reverses aging-related declines in hematopoietic stem cell function.
Systemic View of Stem Cells
Authors: Ray L. Bryan
Published: November 2009

Multiple system-level analyses provide insights into the regulatory events that underlie differentiation of embryonic stem cells.
PARt of the Response to DNA Damage
Authors: Wong Wei
Published: November 2009

PARP-1 promotes the formation of a complex that ultimately leads to NF-κB activation in the DNA damage response.