bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation of Calcium Channels by Group I and Group II Metabotropic Glutamate Receptors in Dentate Gyrus Neurons from Patients with Temporal Lobe Epilepsy
Authors: Schumacher T. B. , Beck H. , Steffens R. , Blümcke I. , Schramm J. , Elger C. E. , Steinhäuser C.
Published: November 2007

Purpose: Metabotropic glutamate receptors (raGluRs) might be promising new drug targets for the treatment of epilepsy because the expression of certain mGluRs is regulated in epilepsy and because activation of mGluRs results in distinctive anti‐ and proconvulsant effects. Therefore, we examined how mGluR activation modulates high‐voltage‐activated (HVA) Ca2+ channels.

Methods: Whole‐cell patch‐clamp recordings were obtained from granule cells and interneuron‐like cells acutely isolated from the dentate gyrus of patients with pharmacoresistent temporal lobe epilepsy.

Results: Agonists selective for either group I or group II mGluRs rapidly and reversibly reduced HVA currents in most dentate gyrus cells. These modulatory effects were inhibited by the respective group I and group IT mGluR antagonists. The specific Ca2+ channel antagonists nifedipine and w‐conotoxin GVLA potently occluded the effects of group I and II mGluR agonists, respectively, indicating that group I mGluRs acted on L‐type channels and group II mGluRs affected N‐type channels. About two thirds of the responsive neurons were sensitive either to group I or group II mGluRs, whereas a minority of cells showed effects to agonists of both groups, indicating a variable mGluR expression pattern.

Conclusions: Group I and group II mGluRs are expressed in human dentate gyrus neurons and modulate L‐ and N‐type HVA channels, respectively. The data shed light on the possible cellular sequelae of the mGluRl upregulation observed in human epileptic dentate gyrus as well as on possible mGluR‐mediated anticonvulsant mechanisms.
How Well Can Epilepsy Syndromes Be Identified at Diagnosis? A Reassessment 2 Years After Initial Diagnosis
Authors: Berg Anne T. , Shinnar Shlorao , Levy Susan R. , Testa Francine M. , Smith‐Rapaport Susan , Beckerman Barbara
Published: November 2007

Purpose: Epilepsy syndromes can be identified very early in the course of a seizure disorder. It is unclear how accurate and resilient such early classifications are. We compared the classification of epilepsy syndromes made previously on the basis of information available at diagnosis with those made 2 years later in a cohort of children with newly diagnosed epilepsy.

Methods: Children (n = 613) were prospectively identified at me time of initial diagnosis by participating physicians in Connecticut between 1993 and 1997. Classification of epilepsy syndrome according to International League Against Epilepsy guidelines was made previously based on all relevant information available at diagnosis. All cases were reclassified again after 2 years of additional evidence had accumulated. The distributions of syndromes at diagnosis and at 2 years are compared and reasons for changes examined.

Results: After 2 years, syndromes remained the same in 86.3% of the cohort and changes occurred in 13.7% (n = 84). Evolution of the syndrome occurred in 24 children (3.9%), and rectification to the initial diagnosis occurred in 60 children (9.8%). The most common scenario for evolution of a syndrome was from West syndrome (n = 5), undetermined (n = 4), or symptomatic localization‐related epilepsy (n = 3) to the Lennox‐Gastaut syndrome. The most common rectification of initial classifications involved incompletely classified syndromes (cryptogenic localization‐related and undetermined syndromes; n = 36). In a few instances, a fully specified syndrome was reclassified to another apparently unrelated syndrome. In these cases, initial information at diagnosis had been difficult to interpret.

Conclusions: Epilepsy syndromes can, for the most part, be identified at the time of initial diagnosis. Two years later, rectifications were made in only 9.8% of cases, and most of these involved syndromes that represented incomplete classifications in the first place. Significant changes were rare. The International League Against Epilepsy classification of the epilepsies can be meaningfully applied in epidemiological studies of newly diagnosed pediatric epilepsy.
Sulthiame as Monotherapy in Children with Benign Childhood Epilepsy with Centrotemporal Spikes: A 6‐Month Randomized, Double‐Blind, Placebo‐Controlled Study
Authors: Rating Dietz , Wolf Christian , Bast Thomas
Published: November 2007

Purpose: To evaluate the efficacy and tolerability of sulthiame (STM) as monotherapy in children with benign childhood epilepsy with centrotemporal spikes (BECTS).

Methods: Sixty‐six BECTS patients entered a 6‐month double‐blind trial and were randomized to receive either STM (5 mg/kg/day) or a placebo. All patients had had two or more seizures during the 6 months preceding the trial and were aged 3–11 years. Seizures were recorded by parents in a diary. STM plasma levels and electroencephalograms (EEGs) were overseen by patient‐blinded observers. The primary effectiveness variable was the rate of treatment failure events (TFEs) per group. TFEs consisted of a first seizure after a 7‐day run‐in period, intolerable adverse events (AEs), development of another epileptic syndrome, or termination of the trial by parents or patient.

Results: Twenty‐five of the 31 STM‐treated patients (81%) and 10 of the 35 placebo‐treated patients (29%) completed the trial without any TFEs (p = 0.00002). Most TFEs were seizures (n = 4 for the STM patients, n = 21 for the placebo group). Parents requested termination for two placebo‐treated patients. Four patients were terminated for administrative reasons. No patient was withdrawn for AEs. While all patients displayed at least one specific focus in either the awake or asleep EEG initially, 11 STM‐treated patients had a normal awake EEG and 10 had a normal asleep one after 6 months.

Conclusions: STM was remarkably effective in preventing seizures in patients with BECTS. Patients suffering from ≥2 seizures during the past 6 months had a high risk of early recidivism. STM was well tolerated and should be considered for children with BECTS who are in need of treatment.
Gabapentin Versus Vigabatrin as First Add‐On for Patients with Partial Seizures That Failed to Respond to Monotherapy: A Randomized, Double‐Blind, Dose Titration Study
Authors: Lindberger Martin , Alenius Martin , Frisén Lars , Johannessen Svein I. , Larsson Sirkku , Malmgren Kristina , Torason Torbjorn
Published: November 2007

Purpose: Our objective was to compare the efficacy and safety of gabapentin and vigabatrin as first‐line addon treatment in patients with partial epilepsy.

Methods: This was a multicenter, double‐blind, randomized dose titration study. After baseline assessment and randomization, the dose could be increased if seizures persisted and reduced if side effects occurred. Health‐related quality of life was assessed at baseline and at the end of the study. By a protocol amendment post hoc, all randomized patients were offered a standardized perimetry examination at the end of the study. Improvement rate was the proportion of patients with a reduction of seizure frequency of at least 50% during an 8‐week period without any adverse events causing withdrawal.

Results: One hundred two patients were randomized and analyzed on an intent‐to‐treat basis. The improvement rate was 48% in the gabapentin group and 56% in the vigabatrin group. The improvement rate, when per protocol criteria were fulfilled, was 57% in the gabapentin group and 59% in the vigabatrin group. The proportion of seizure‐free patients was 31 % in the gabapentin group and 39% in the vigabatrin group. There was no difference in quality‐of‐life scores between the groups. Perimetry after termination of the study on 64 patients showed abnormal results in 3 of 32 patients in the vigabatrin group.

Conclusion: Approximately one third of the patients in both groups became seizure‐free. Although no major differences were seen in terms of the improvement rate between the groups, equivalence between the two drugs was not found.
Epilepsy and Antiepileptic Drug Therapy in Juvenile Neuronal Ceroid Lipofuscinosis
Authors: Åberg L. E. , Bäckman M. , Kirveskari E. , Santavuori P.
Published: November 2007

Purpose: To survey the characteristics of epilepsy in patients with juvenile neuronal ceroid lipofuscinosis (JNCL) and determine the antiepileptic drug (AED) treatment most suitable for these patients.

Methods: The study included 60 patients with JNCL; their mean age was 16.5 years (range 5–33). The age at onset of epilepsy, type of seizures, effect of the first AED on seizures, and the current seizure frequency and AED therapy were studied. The side effects of the AEDs were also clarified.

Results: Fifty of the 60 patients had epilepsy. Patients' first epileptic seizure occurred at a mean age of 10.0 years (range 5–16), the most common type being generalized seizures. As the first AED tried, valproate (VPA) and lamotrigine (LTG) appeared equally effective, with 80% of the patients responding to these AEDs. During the study year, the median seizure frequency was four seizures a year (range 0–120), and 72% of the patients had good or satisfactory seizure control (0–6 seizures a year). In the different AED therapy groups, the proportion of patients with good or satisfactory seizure control ranged from 25% to 100%. LTG in monotherapy or in combination with clonazepam (CZP) was superior to other AEDs or combinations, but VPA also seemed effective. Adverse effects leading to the discontinuation of an AED were observed in 25% of the patients, most frequently in patients receiving phenobarbital (PB). No patient receiving LTG had to discontinue the drug due to adverse effects.

Conclusion: Epilepsy in JNCL can usually be successfully treated with the current AEDs. In Finnish patients with JNCL, treatment is based on LTG, or, secondarily, VPA. In combination therapy, CZP seems a valuable add‐on AED.
Significance of Cerebellar Atrophy in Intractable Temporal Lobe Epilepsy: A Quantitative MRI Study
Authors: Sandok Evan K. , O'Brien Terence J. , Jack Clifford R. , So Elson L.
Published: November 2007

Purpose: To determine the incidence of cerebellar atrophy (CA) in patients with intractable temporal lobe epilepsy, whether any clinical factors are significantly associated with CA, whether CA is unilateral or asymmetric and whether this feature has any relationship to the side of epileptogenicity, and whether the presence of CA is related to epilepsy surgery outcome.

Methods: We developed a magnetic resonance imaging method of measuring the presurgical volumes of the cerebellar hemispheres of 185 patients who underwent temporal lobectomy for intractable epilepsy and of 80 control subjects. In addition, cerebellar volumes were normalized to the total brain volumes. CA was determined as being present when the measured volume was smaller than two standard deviations from the mean value found in control subjects.

Results: Both absolute and normalized cerebellar volumes were found to be significantly reduced in the epilepsy patients compared with the control subjects. Without normalization of the cerebellar volumes, CA was present in 25.9% of the epilepsy patients; with normalization, it was present in only 16.2%. The atrophy was symmetric between the cerebellar hemispheres, and there was no significant difference in volume between the hemisphere ipsilateral and the hemisphere contralateral to the side of the temporal lobectomy. The duration of epilepsy was significantly longer and the age at onset of epilepsy was younger in patients with CA than in those without CA. The presence of CA was not associated with the outcome of temporal lobectomy.

Conclusions: CA is symmetric and common in patients with intractable temporal lobe epilepsy. However, the results suggest that the atrophy in one third of patients with CA also proportionately affects the cerebral hemispheres. The duration of epilepsy and the age at onset of epilepsy are associated with the occurrence of CA. Seizure control after temporal lobectomy is not influenced by the presence of CA.
New Insights into the Clinical Management of Partial Epilepsies
Authors: Hirsch Edouard , de Saint‐Martin Anne , Arzimanoglou Alexis
Published: November 2007

Summary The diagnosis, treatment, and prognosis of seizure disorders depend on the correct identification of epileptic syndromes. Partial epilepsies are heterogeneous and can be divided into idiopathic, cryptogenic, and symptomatic epilepsies. The most common of the idiopathic localization‐related epilepsies is benign epilepsy with rolandic or centrotemporal spikes (BECTS). Seizures remain rare and the use of antiepileptic drug (AED) treatment in all patients does not appear justified. Children who present with some of the electroclinical characteristics of BECTS may also display severe unusual neurologic, neuropsychological, or atypical symptoms. In some cases, carbamazepine has been implicated as a triggering factor. Primary reading epilepsy and idiopathic occipital lobe epilepsies with photosensitivity are examples of an overlap between idiopathic localization‐related and generalized epilepsies and respond well to sodium valproate. Autosomal dominant nocturnal frontal lobe epilepsy and benign familial infantile convulsions are recently described syndromes, differing in several ways from classical idiopathic localization‐related epileptic syndromes. In cryptogenic or symptomatic epilepsy, the topography of the epileptogenic zone might influence drug efficacy. An individualized approach to AED selection, tailored to each patient's needs, should be used. Resistance of seizures to antiepileptic therapy may be due to diagnostic and/or treatment error or may be the result of noncompliance. Increasing the dosage, discontinuation or replacement of a drug, or addition of a second drug is indicated in truly resistant cases. The use of more than two AEDs rarely optimizes seizure control, and in some cases reduction of treatment may improve seizure control while lessening side effects. EEG‐video assessment of patients with refractory epilepsy is important. Indications for and timing of epilepsy surgery should be reconsidered. Surgical therapy should probably be used more often and earlier than it is at present.
Estimated Functional Capacity Predicts Mortality in Older Adults
Authors: Sui Xuemei , Laditka James N. , Hardin James W. , Blair Steven N.
Published: November 2007

OBJECTIVES: To examine associations between functional capacity estimated from cardiorespiratory fitness (CRF) and mortality risks in adults aged 60 and older.

DESIGN: Prospective study, averaging 13.6 years follow‐up.

SETTING: Preventive medical clinic.

PARTICIPANTS: Four thousand sixty adults who completed preventive medical examinations between 1971 and 2001; 24.7% women, mean age±standard deviation 64.6±4.9, body mass index (BMI) 25.9±3.8 kg/m2.

MEASUREMENTS: CRF was quantified as metabolic equivalents (METs) achieved during maximal treadmill exercise. The lowest 20% of the age‐ and sex‐specific MET distribution was defined as having low CRF, the middle 40% moderate CRF, and the upper 40% high CRF. Cox regression was used to estimate death rates (per 1,000 person‐years), hazard ratios (HRs), and their 95% confidence intervals (CIs).

RESULTS: Nine hundred eighty‐nine deaths occurred during follow‐up. Death rates adjusted for age, sex, and examination year were 30.9, 18.3, and 13.4 for all causes (P<.001); 15.9, 8.6, and 5.4 for cardiovascular disease (CVD) (P<.001); and 6.1, 4.9, and 4.2 for cancer (P=.04) for subjects with low, moderate, and high CRF, respectively. After adjusting for smoking, abnormal electrocardiograms at rest or while exercising, percentage of age‐predicted maximal heart rate achieved during exercise testing, baseline medical conditions, BMI, hypercholesterolemia, and family CVD and cancer history, subjects with high CRF had notably lower mortality risk than those with low CRF from all causes (HR=0.59, 95% CI=0.47–0.74) and from CVD (HR=0.57, 95% CI=0.41–0.80).

CONCLUSION: CRF is an important independent predictor of death in older adults. The results add to the existing evidence that promoting physical activity in older adults provides substantial health benefits, even in the oldest old.
Geriatric Patients' Preferences for Treatment of Urinary Incontinence: A Study of Hospitalized, Cognitively Competent Adults Aged 80 and Older
Authors: Pfisterer Mathias H.‐D. , Johnson Theodore M. , Jenetzky Ekkehart , Hauer Klaus , Oster Peter
Published: November 2007

OBJECTIVES: To elicit preferences for different urinary incontinence (UI) treatments of geriatric patients, to contrast these answers with answers from potential health proxies and providers, and to understand how select demographic factors might explain differences in patients' preferences.

DESIGN: Cross‐sectional, descriptive.

SETTING: German geriatric hospital.

PARTICIPANTS: Medical inpatients aged 80 and older in a geriatric hospital, their physicians and nurses, and their family members.

MEASURES: Six forced‐choice paired comparisons of four UI treatments were measured on an 11‐point visual analog scale, with verbal anchors.

RESULTS: One hundred seventeen patients (mean age 84.6; 43% with UI), 72 staff members, and 71 family members participated. Although some preferred even “unpopular” management strategies, most respondents preferred diapers (79%), medications (78%), and scheduled toileting (79%) to urinary catheters; 64% preferred scheduled toileting to diapers. When choosing between diapers and medication, equal proportions preferred each option. In regression models, sex, activity of daily living score, and past treatment experience were significantly associated with expressed preferences. Proxies expressed greater preference for scheduled toileting than for diapers than patients did (P<.001). Intraclass correlation coefficients indicated at most only slight to fair agreement between patients and most other groups; spouses showed moderate to almost perfect agreement with patients.

CONCLUSION: Preferences of cognitively competent geriatric patients for treatment of UI differed from those of their potential proxies (other than spouses), which emphasizes the need for focused communication to properly elicit patient preferences to achieve appropriate treatment decisions.
Comparison of Stress Experienced by Family Members of Patients Treated in Hospital at Home with That of Those Receiving Traditional Acute Hospital Care
Authors: Leff Bruce , Burton Lynda , Mader Scott L. , Naughton Bruce , Burl Jeffrey , Koehn Debbie , Clark Rebecca , Greenough William B. , Guido Susan , Steinwachs Donald , Burton John R.
Published: November 2007

OBJECTIVES: To compare differences in the stress experienced by family members of patients cared for in a physician‐led substitutive Hospital at Home (HaH) and those receiving traditional acute hospital care.

DESIGN: Survey questionnaire completed as a component of a prospective, nonrandomized clinical trial of a substitutive HaH care model.

SETTING: Three Medicare managed care health systems and a Veterans Affairs Medical Center.

PARTICIPANTS: Two hundred fourteen community‐dwelling elderly patients who required acute hospital admission for community‐acquired pneumonia, exacerbation of chronic heart failure, exacerbation of chronic obstructive pulmonary disease, or cellulitis.

INTERVENTION: Treatment in a substitutive HaH model.

MEASUREMENTS: Fifteen‐question survey questionnaire asking family members whether they experienced a potentially stressful situation and, if so, whether stress was associated with the situation while the patient received care.

RESULTS: The mean and median number of experiences, of a possible 15, that caused stress for family members of HaH patients was significantly lower than for family members of acute care hospital patients (mean ± standard deviation 1.7 ± 1.8 vs 4.3 ± 3.1, P<.001; median 1 vs 4, P<.001). HaH care was associated with lower odds of developing mean levels of family member stress (adjusted odds ratio=0.12, 95% confidence interval=0.05–0.30).

CONCLUSION: HaH is associated with lower levels of family member stress than traditional acute hospital care and does not appear to shift the burden of care from hospital staff to family members.
An update on airborne contact dermatitis: 2001–2006
Authors: Santos Raquel , Goossens An
Published: November 2007

Reports on airborne dermatoses are mainly published in the context of occupational settings. Hence, in recent years, dermatologists and also occupational physicians have become increasingly aware of the airborne source of contact dermatitis, resulting mainly from exposure to irritants or allergens. However, their occurrence is still underestimated, because reports often omit the term ‘airborne’ in relation to dust or volatile allergens. For the present update, we screened the journals ‘Contact Dermatitis’ (July 2000 to December 2006); ‘Dermatitis’, formerly named ‘American Journal of Contact Dermatitis’; ‘La Lettre du Gerda’ (January 2000 to December 2006); and also included relevant articles from other journals published during the same period. This resulted in an updated list of airborne dermatitis causes.
Occupational airborne allergic contact dermatitis from methacrylates in a dental nurse
Authors: Isaksson Marléne , Zimerson Erik , Svedman Cecilia
Published: November 2007

Background:  There are very few reports of airborne allergic contact dermatitis from methacrylates.

Objectives:  To report a dental nurse with facial eczema supposedly caused by airborne methacrylates present in the work environment.

Methods:  Patch testing with serial dilutions of several methacrylates and work provocations in environments containing methacrylates was performed.

Results:  Patch testing with serial dilutions of several methacrylates disclosed a high patch test reactivity. Repeated provocations when working with methacrylates resulted in facial eczema that resolved out of work. Attempts to collect the sensitizers using air pumps for the collection of vapors and filters for the collection of air‐born aerosols failed.

Conclusions:  The clinical presentation was that of a facial dermatitis due to airborne exposure to methacrylates. It seems likely that 1 or several of these allergens caused the dermatitis.
Dandy–Walker syndrome and chromosomal abnormalities
Authors: Imataka George , Yamanouchi Hideo , Arisaka Osamu
Published: November 2007

ABSTRACT Dandy–Walker syndrome (DWS) is a brain malformation of unknown etiology, but several reports have been published indicating that there is a causal relationship to various types of chromosomal abnormalities and malformation syndromes. In the present article, we present a bibliographical survey of several previously issued reports on chromosomal abnormalities associated with DWS, including our case of DWS found in trisomy 18. There are various types of chromosomal abnormalities associated with DWS; most of them are reported in chromosome 3, 9, 13 and 18. We also summarize some other chromosomal abnormalities and various congenital malformation syndromes.
Congenital malformations in infants whose mothers reported the use of folic acid in early pregnancy in Sweden. A prospective population study
Authors: Källén Bengt
Published: November 2007

ABSTRACT  The use of folic acid prior to conception is generally recommended for the prevention of birth defects, notably neural tube defects. In a previous study from Sweden, based on interviews of women in early pregnancy, no such effect was found on the general malformation rate, but data for neural tube defects were scarce. Using data from the Swedish Medical Birth Register for the years 1995–2004, 20 891 women were identified who reported the use of folic acid in early pregnancy, but not of anticonvulsants. These women were compared to all other women who gave birth during the study period. Malformations in the infants born were identified from multiple sources. No reduction in the general malformation rate was seen among infants born to women who reported the use of folic acid (OR = 1.09, 95% CI 1.02–1.17) and no effect of neural tube defect rate was seen (RR = 1.35, 95% CI 0.82–2.22), based on 16 infants with neural tube defect whose mother reported the use of folic acid. No effect was seen on the rates of other malformations except for cardiac defects, where a statistically significant increased risk (notably for severe defects) was found (OR = 1.19, 95% CI 1.05–1.35). The effect of various deficiencies in data collection is discussed, but is unlikely to explain the lack of protective effect noticed. So far, it has not been possible to demonstrate a beneficial effect of folic acid supplementation on malformation risk in Sweden. A more complete ascertainment and detailed timing and dosage of folic acid use in a prospective study is recommended.
Cross–regulatory interactions between Fgf8 and Shh in the avian frontonasal prominence
Authors: Abzhanov Arhat , Cordero Dwight R. , Sen Jonaki , Tabin Clifford J. , Helms Jill A.
Published: November 2007

ABSTRACT  The frontonasal prominence of the developing avian embryo contains an organizing center, defined by juxtaposition of the Sonic hedgehog (Shh) and Fibroblast growth factor 8 (Fgf8) expression domains. This molecular interface presages any detectable growth of the frontonasal prominence, and experiments involving transplantation of this boundary epithelium have demonstrated it is a source of dorsal‐ventral and rostral‐caudal patterning information for the neural crest‐derived mesenchyme of the upper beak. We explored the ontogeny of this organizing center by mapping the expression domains of both genes and their receptors and downstream targets. We tested the extent to which Shh and Fgf8 regulate each other's expression in this frontonasal organizer by either blocking or ectopically activating these pathways. Our experiments revealed mutual antagonism between the two molecules, which aids in establishing and maintaining a molecular boundary that subsequently influences patterning and growth of the middle and upper face.
Transient Behavior of Turbomachineries: Applications to Radial Flow Pump Startups
Authors: Dazin Antoine , Caignaert Guy , Bois Gérard
Published: November 2007

A theoretical analysis of the fast transients of turbomachineries, based on the study of unsteady and incompressible fluids mechanics equations applied to an impeller, is proposed. It leads to internal torque, internal power, and impeller head of an impeller during transient periods. The equations show that the behavior of a pump impeller is not only depending on the acceleration rate and flow rate, as it is usually admitted, but also on velocity profiles and their evolution during the transient. Some hypotheses on the flow in a radial flow pump are proposed. They are validated by comparison with the experimental results of a single stage, single volute radial flow pump during some fast acceleration periods. The model is also used to analyze the behavior of the pump during a fast startup.
Assessment of Predictive Capabilities of Detached Eddy Simulation to Simulate Flow and Mass Transport Past Open Cavities
Authors: Chang Kyoungsik , Constantinescu George , Park Seung-O
Published: November 2007

The three-dimensional (3D) incompressible flow past an open cavity in a channel is predicted using the Spalart–Almaras (SA) and the shear-stress-transport model (SST) based versions of detached eddy simulation (DES). The flow upstream of the cavity is fully turbulent. In the baseline case the length to depth (L∕D) ratio of the cavity is 2 and the Reynolds number ReD=3360. Unsteady RANS (URANS) is performed to better estimate the performance of DES using the same code and meshes employed in DES. The capabilities of DES and URANS to predict the mean flow, velocity spectra, Reynolds stresses, and the temporal decay of the mass of a passive contaminant introduced instantaneously inside the cavity are assessed based on comparisons with results from a well resolved large eddy simulation (LES) simulation of the same flow conducted on a very fine mesh and with experimental data. It is found that the SA-DES simulation with turbulent fluctuations at the inlet gives the best overall predictions for the flow statistics and mass exchange coefficient characterizing the decay of scalar mass inside the cavity. The presence of inflow fluctuations in DES is found to break the large coherence of the vortices shed in the separated shear layer that are present in the simulations with steady inflow conditions and to generate a wider range of 3D eddies inside the cavity, similar to LES. The predictions of the mean velocity field from URANS and DES are similar. However, URANS predictions show poorer agreement with LES and experiment compared to DES for the turbulence quantities. Additionally, simulations with a higher Reynolds number (ReD=33,600) and with a larger length to depth ratio (L∕D=4) are conducted to study the changes in the flow and shear-layer characteristics, and their influence on the ejection of the passive contaminant from the cavity.
Hybrid Two-Fluid DEM Simulation of Gas-Solid Fluidized Beds
Authors: Sun Jin , Battaglia Francine , Subramaniam Shankar
Published: November 2007

Simulations of gas-solid fluidized beds have been performed using a hybrid simulation method, which couples the discrete element method (DEM) for particle dynamics with the averaged two-fluid (TF) continuum equations for the gas phase. The coupling between the two phases is modeled using an interphase momentum transfer term. The results of the hybrid TF-DEM simulations are compared to experimental data and TF model simulations. It is found that the TF-DEM simulation is capable of predicting general fluidized bed dynamics, i.e., pressure drop across the bed and bed expansion, which are in agreement with experimental measurements and TF model predictions. Multiparticle contacts and large contact forces distribute in the regions away from bubbles, as demonstrated from the TF-DEM simulation results. The TF-DEM model demonstrates the capability to capture more heterogeneous structural information of the fluidized beds than the TF model alone. The implications to the solid phase constitutive closures for TF models are discussed. However, the TF-DEM simulations depend on the form of the interphase momentum transfer model, which can be computed in terms of averaged or instantaneous particle quantities. Various forms of the interphase momentum transfer model are examined, and simulation results from these models are compared.
Representing Polydispersed Droplet Behavior in Nucleating Steam Flow
Authors: Gerber A. G. , Mousavi A.
Published: November 2007

The quadrature method of moments (QMOM) is applied to the particle size distribution (PSD) present in nucleating steam flow, with a particular emphasis on conditions relevant to low-pressure steam turbines. These machines exhibit heterogeneous and homogeneous phase transition in the presence of strong flow discontinuities due to shocks and complex geometry. They offer a particularly difficult two-phase modeling situation. The present work shows that QMOM is a robust and efficient method and, in comparison to current practice of using a monodispersed PSD in computational fluid dynamics (CFD) models, offers promise for dealing with the complex two-phase conditions present in real machines.
Reduction of a grid moiré pattern by integrating a carbon‐interspaced high precision x‐ray grid with a digital radiographic detector
Authors: Yoon Jai‐Woong , Park Young‐Guk , Park Chun‐Joo , Kim Do‐Il , Lee Jin‐Ho , Chung Nag‐Kun , Choe Bo‐Young , Suh Tae‐Suk , Lee Hyoung‐Koo
Published: November 2007

The stationary grid commonly used with a digital x‐ray detector causes a moiré interference pattern due to the inadequate sampling of the grid shadows by the detector pixels. There are limitations with the previous methods used to remove the moiré such as imperfect electromagnetic interference shielding and the loss of image information. A new method is proposed for removing the moiré pattern by integrating a carbon‐interspaced high precision x‐ray grid with high grid line uniformity with the detector for frequency matching. The grid was aligned to the detector by translating and rotating the x‐ray grid with respect to the detector using microcontrolled alignment mechanism. The gap between the grid and the detector surface was adjusted with micrometer precision to precisely match the projected grid line pitch to the detector pixel pitch. Considering the magnification of the grid shadows on the detector plane, the grids were manufactured such that the grid line frequency was slightly higher than the detector sampling frequency. This study examined the factors that affect the moiré pattern, particularly the line frequency and displacement. The frequency of the moiré pattern was found to be sensitive to the angular displacement of the grid with respect to the detector while the horizontal translation alters the phase but not the moiré frequency. The frequency of the moiré pattern also decreased with decreasing difference in frequency between the grid and the detector, and a moiré‐free image was produced after complete matching for a given source to detector distance. The image quality factors including the contrast, signal‐to‐noise ratio and uniformity in the images with and without the moiré pattern were investigated.
Anisotropic imaging performance in breast tomosynthesis
Authors: Badano Aldo , Kyprianou Iacovos S. , Jennings Robert J. , Sempau Josep
Published: November 2007

We describe the anisotropy in imaging performance caused by oblique x‐ray incidence in indirect detectors for breast tomosynthesis based on columnar scintillator screens. We use MANTIS, a freely available combined x‐ray, electron, and optical Monte Carlo transport package which models the indirect detection processes in columnar screens, interaction by interaction. The code has been previously validated against published optical distributions. In this article, initial validation results are provided concerning the blur for particular designs of phosphor screens for which some details with respect to the columnar geometry are available from scanning electron microscopy. The polyenergetic x‐ray spectrum utilized comes from a database of experimental data for three different anode/filter/kVp combinations: at , at , and at . The x‐ray spectra were then filtered with breast tissue (3, 4, and thickness), compression paddle, and support base, according to the oblique paths determined by the incidence angle. The composition of the breast tissue was adipose/glandular tissue mass ratio. Results are reported on the pulse‐height statistics of the light output and on spatial blur, expressed as the response of the detector to a pencil beam with a certain incidence angle. Results suggest that the response is nonsymmetrical and that the resolution properties of a tomosynthesis system vary significantly with the angle of x‐ray incidence. In contrast, it is found that the noise due to the variability in the number of light photons detected per primary x‐ray interaction changes only a few percent. The anisotropy in the response is not less in screens with absorptive backings while the noise introduced by variations in the depth‐dependent light output and optical transport is larger. The results suggest that anisotropic imaging performance across the detector area can be incorporated into reconstruction algorithms for improving the image quality of breast tomosynthesis. This study also demonstrates that the assessment of image quality of breast tomosynthesis systems requires a more complete description of the detector response beyond local, center measurements of resolution and noise that assume some degree of symmetry in the detector performance.
Shielding properties of lead‐free protective clothing and their impact on radiation doses
Authors: Schlattl Helmut , Zankl Maria , Eder Heinrich , Hoeschen Christoph
Published: November 2007

The shielding properties of two different lead‐free materials—tin and a compound of 80% tin and 20% bismuth—for protective clothing are compared with those of lead for three typical x‐ray spectra generated at tube voltages of 60, 75, and . Three different quantities were used to compare the shielding capability of the different materials: (1) Air‐kerma attenuation factors in narrow‐beam geometry, (2) air‐kerma attenuation factors in broad‐beam geometry, and (3) ratios of organ and effective doses in the human body for a whole‐body irradiation with a parallel beam directed frontally at the body. The thicknesses of tin and the tin/bismuth compound to be compared against lead correspond to a lead equivalence value of for the spectrum. The narrow‐beam attenuation factors for tin are 54% and 32% lower than those for lead for 60 and ; those for tin/bismuth are 12% and 32% lower, respectively. The decrease of the broad‐beam air‐kerma attenuation factors compared to lead is 74%, 46%, and 41% for tin and 42%, 26%, and 33% for tin/bismuth and the spectra at 60, 75, and , respectively. Therefore, it is recommended that the characterization of the shielding potential of a material should be done by measurements in broad‐beam geometry. Since the secondary radiation that is mainly responsible for the shielding reduction in broad‐beam geometry is of low penetrability, only more superficially located organs receive significantly enhanced doses. The increase for the dose to the glandular breast tissue (female) compared to being shielded by lead is 143%, 37%, and 45% when shielded by tin, and 35%, 15%, and 39% when shielded by tin/bismuth for 60, 75, and , respectively. The effective dose rises by 60%, 6%, and 38% for tin, and 14%, 3% and, 35% for tin/bismuth shielding, respectively.
A short‐scan reconstruction for cone‐beam CT using shift‐invariant FBP and equal weighting
Authors: Zhu Lei , Yoon Sungwon , Fahrig Rebecca
Published: November 2007

A 3D reconstruction formula has been derived for a circular cone‐beam (CB) short scan using 1D shift‐invariant filtering, CB backprojection, and equal weighting. By first converting the divergent projections to parallel projections, we analyze the circular CB data using the classic central slice theorem. The sampling density in Fourier space is investigated and 1D shift‐invariant filtering before backprojection can be used to compensate for the nonuniformity. The final formula consists of a conventional FDK reconstruction and a correction term using differential backprojection and the 1D Hilbert transform in the image domain. On a full scan, the approach reduces to the FDK algorithm, while for a short scan, the CB artifacts are suppressed by the second term. This algorithm outperforms the modified FDK algorithm with Parker's weighting, as illustrated by computer simulations and experimental results. Due to its shift‐invariant filtered‐backprojection structure, the proposed algorithm is implemented efficiently, and requires a simple adaptation of the FDK algorithm.
A three‐dimensional statistical approach to improved image quality for multislice helical CT
Authors: Thibault Jean‐Baptiste , Sauer Ken D. , Bouman Charles A. , Hsieh Jiang
Published: November 2007

Multislice helical computed tomography scanning offers the advantages of faster acquisition and wide organ coverage for routine clinical diagnostic purposes. However, image reconstruction is faced with the challenges of three‐dimensional cone‐beam geometry, data completeness issues, and low dosage. Of all available reconstruction methods, statistical iterative reconstruction (IR) techniques appear particularly promising since they provide the flexibility of accurate physical noise modeling and geometric system description. In this paper, we present the application of Bayesian iterative algorithms to real 3D multislice helical data to demonstrate significant image quality improvement over conventional techniques. We also introduce a novel prior distribution designed to provide flexibility in its parameters to fine‐tune image quality. Specifically, enhanced image resolution and lower noise have been achieved, concurrently with the reduction of helical cone‐beam artifacts, as demonstrated by phantom studies. Clinical results also illustrate the capabilities of the algorithm on real patient data. Although computational load remains a significant challenge for practical development, superior image quality combined with advancements in computing technology make IR techniques a legitimate candidate for future clinical applications.
Fast DRR splat rendering using common consumer graphics hardware
Authors: Spoerk Jakob , Bergmann Helmar , Wanschitz Felix , Dong Shuo , Birkfellner Wolfgang
Published: November 2007

Digitally rendered radiographs (DRR) are a vital part of various medical image processing applications such as 2D/3D registration for patient pose determination in image‐guided radiotherapy procedures. This paper presents a technique to accelerate DRR creation by using conventional graphics hardware for the rendering process. DRR computation itself is done by an efficient volume rendering method named wobbled splatting. For programming the graphics hardware, NVIDIAs C for Graphics (Cg) is used. The description of an algorithm used for rendering DRRs on the graphics hardware is presented, together with a benchmark comparing this technique to a CPU‐based wobbled splatting program. Results show a reduction of rendering time by about 70%–90% depending on the amount of data. For instance, rendering a volume of voxels is feasible at an update rate of compared to on a common Intel‐based PC using the graphics processing unit (GPU) of a conventional graphics adapter. In addition, wobbled splatting using graphics hardware for DRR computation provides higher resolution DRRs with comparable image quality due to special processing characteristics of the GPU. We conclude that DRR generation on common graphics hardware using the freely available Cg environment is a major step toward 2D/3D registration in clinical routine.
Improved dynamic‐programming‐based algorithms for segmentation of masses in mammograms
Authors: Domínguez Alfonso Rojas , Nandi Asoke K.
Published: November 2007

In this paper, two new boundary tracing algorithms for segmentation of breast masses are presented. These new algorithms are based on the dynamic programming‐based boundary tracing (DPBT) algorithm proposed in Timp and Karssemeijer, [S. Timp and N. Karssemeijer, Med. Phys. 31, 958–971 (2004)] The DPBT algorithm contains two main steps: (1) construction of a local cost function, and (2) application of dynamic programming to the selection of the optimal boundary based on the local cost function. The validity of some assumptions used in the design of the DPBT algorithm is tested in this paper using a set of 349 mammographic images. Based on the results of the tests, modifications to the computation of the local cost function have been designed and have resulted in the Improved‐DPBT (IDPBT) algorithm. A procedure for the dynamic selection of the strength of the components of the local cost function is presented that makes these parameters independent of the image dataset. Incorporation of this dynamic selection procedure has produced another new algorithm which we have called . Methods for the determination of some other parameters of the DPBT algorithm that were not covered in the original paper are presented as well. The merits of the new IDPBT and algorithms are demonstrated experimentally by comparison against the DPBT algorithm. The segmentation results are evaluated with base on the area overlap measure and other segmentation metrics. Both of the new algorithms outperform the original DPBT; the improvements in the algorithms performance are more noticeable around the values of the segmentation metrics corresponding to the highest segmentation accuracy, i.e., the new algorithms produce more optimally segmented regions, rather than a pronounced increase in the average quality of all the segmented regions.
A method based on moving least squares for XRII image distortion correction
Authors: Yan Shiju , Wang Chengtao , Ye Ming
Published: November 2007

This paper presents a novel integrated method to correct geometric distortions of XRII (x‐ray image intensifier) images. The method has been compared, in terms of mean‐squared residual error measured at control and intermediate points, with two traditional local methods and a traditional global methods. The proposed method is based on the methods of moving least squares (MLS) and polynomial fitting. Extensive experiments were performed on simulated and real XRII images. In simulation, the effect of pincushion distortion, sigmoidal distortion, local distortion, noise, and the number of control points was tested. The traditional local methods were sensitive to pincushion and sigmoidal distortion. The traditional global method was only sensitive to sigmoidal distortion. The proposed method was found neither sensitive to pincushion distortion nor sensitive to sigmoidal distortion. The sensitivity of the proposed method to local distortion was lower than or comparable with that of the traditional global method. The sensitivity of the proposed method to noise was higher than that of all three traditional methods. Nevertheless, provided the standard deviation of noise was not greater than 0.1 pixels, accuracy of the proposed method is still higher than the traditional methods. The sensitivity of the proposed method to the number of control points was greatly lower than that of the traditional methods. Provided that a proper cutoff radius is chosen, accuracy of the proposed method is higher than that of the traditional methods. Experiments on real images, carried out by using a 9 in. XRII, showed that residual error of the proposed method is lower than that of the traditional global method and local methods ( and , respectively).
Choosing the optimal fit function: Comparison of the Akaike information criterion and the F‐test
Authors: Glatting Gerhard , Kletting Peter , Reske Sven N. , Hohl Kathrin , Ring Christina
Published: November 2007

In many circumstances of data fitting one has to choose the optimal fitting function or model among several alternatives. Criteria or tests on which this decision is based are necessary and have to be well selected. In this preliminary analysis the application of the corrected Akaike information criterion is demonstrated considering the example of determining pharmacokinetic parameters for the blood serum time activity curves of ‐labeled anti‐CD66 antibody. Another model selection criterion, the F‐test, is used for comparison. For the investigated data the corrected Akaike information criterion has proved to be an effective and efficient approach, applicable to nested and non‐nested models.