bluuebunny/crossref_metadata_2025 huggingface dataset:
Rate‐Independent QT Shortening During Exercise in Healthy Subjects: Terminal Repolarization Does Not Shorten with Exercise
Authors: KANNANKERIL PRINCE J. , HARRIS PAUL A. , NORRIS KRIS J. , WARSY IRFAN , SMITH PHILLIP D. , RODEN DAN M.
Published: July 2008

Introduction: QT interval for a given heart rate differs between exercise and recovery (QT hysteresis) due to slow QT adaptation to changes in heart rate. We hypothesized that QT hysteresis is evident within stages of exercise and investigated which component of the QT contributes to hysteresis.

Methods and Results: Nineteen healthy volunteers performed a staged exercise test (four stages, 3 min each). Continuous telemetry was analyzed with software to compare QT intervals in a rate‐independent fashion. QRST complexes during each minute were sorted by RR interval, and complexes in bins of 20 ms width were signal‐averaged. QT and QTp (onset of QRS to peak T wave) were measured, and terminal QT calculated (peak to end of T wave, Tpe = QT – QTp). QT, QTp, and Tpe at the same heart rate were compared between the first and last minute of each stage. QT shortened from the first to last minute of exercise in each stage (Stage I: 358 ± 30 to 346 ± 25 ms, P < 0.001; Stage II: 342 ± 27 to 331 ± 24 ms, P = 0.003; Stage III: 329 ± 21 to 322 ± 18 ms, P = 0.03; Stage IV: 313 ± 22 to 303 ± 23 ms, P = 0.005). QTp also shortened in each stage, while Tpe was unchanged.

Conclusion: QT hysteresis occurs during exercise in normals, and the major determinant is shortening of the first component of the T wave. Terminal repolarization (peak to end of T wave), a surrogate for transmural dispersion of repolarization, does not shorten significantly with exercise.
Hypersensitivity to local anaesthetics – update and proposal of evaluation algorithm
Authors: Thyssen Jacob Pontoppidan , Menné Torkil , Elberling Jesper , Plaschke Peter , Johansen Jeanne Duus
Published: July 2008

Local anaesthetics (LA) are widely used drugs. Adverse reactions are rare but may be caused by delayed‐type hypersensitivity reactions and probably also immediate‐type reactions. As it is not always easy to clinically differ between these subtypes, allergy skin testing should be considered. Although numerous test protocols have been published, how patients with hypersensitivity reactions to LA are ideally evaluated remains a topic of discussion. This review attempts to generate a comprehensive update on allergic reactions to LA and to present an algorithm that can be used for the evaluation of patients suspected with immediate‐ and delayed‐type immune reactions. Literature was examined using PubMed‐Medline, EMBASE, Biosis and Science Citation Index. Based on the literature, the proposed algorithm may safely and rapidly distinguish between immediate‐type and delayed‐type allergic immune reactions.
Diagnosis, symptoms, frequency and mortality of 260 patients with urea cycle disorders from a 21‐year, multicentre study of acute hyperammonaemic episodes
Authors: Summar Marshall L , Dobbelaere Dries , Brusilow Saul , Lee Brendan
Published: July 2008

Aim: A large longitudinal interventional study of patients with a urea cycle disorder (UCD) in hyperammonaemic crisis was undertaken to amass a significant body of data on their presenting symptoms and survival.

Methods: Between 1982 and 2003, as part of the FDA approval process, data were collected on patients receiving an intravenous combination of nitrogen scavenging drugs (Ammonul® sodium phenylacetate and sodium benzoate (10%, 10%)) for the treatment of hyperammonaemic crises caused by urea cycle disorders.

Results: A final diagnosis of a UCD was made for 260 patients, representing 975 episodes of hospitalization. Only 34% of these patients presented within the first 30 days of life and had a mortality rate of 32%. The most common presenting symptoms were neurological (80%), or gastrointestinal (33%). This cohort is the largest collection of patients reported for these diseases and the first large cohort in the United States.

Conclusion: Surprisingly, the majority (66%) of patients with heritable causes of hyperammonaemia present beyond the neonatal period (>30 days). Patients with late‐onset presenting disorders exhibited prolonged survival compared to the neonatal‐presenting group.
Ethnic differences in metabolic syndrome among overweight and obese children and adolescents: the Oslo Adiposity Intervention Study
Authors: Pollestad Kolsgaard Magnhild L. , Andersen Lene Frost , Tonstad Serena , Brunborg Cathrine , Wangensteen Teresia , Joner Geir
Published: July 2008

Aim: Are there differences in the prevalence of metabolic syndrome between obese and overweight Norwegian and immigrant children and adolescents?

Methods: Two hundred and three overweight and obese Norwegian, Pakistani, Tamil and Turkish patients aged 6–17 years living in Norway were included. Metabolic syndrome was defined as the presence of at least three abnormal values of waist circumference, blood pressure, fasting triglycerides, fasting glucose and HDL cholesterol.

Results: The prevalence of metabolic syndrome was significantly higher among the immigrant compared to Norwegian subjects when adjusted for age, gender and BMI‐Z‐score (20.8 vs. 30.6%; OR = 2.2, 95% CI = 1.05–4.77). The prevalence of metabolic syndrome increased with increasing severity of obesity and reached 50% in severely obese immigrants and 30% in severely obese Norwegians. Among the overweight subjects metabolic syndrome prevalence was 23.5% among immigrants and 19.4% among Norwegians.

Conclusion: Metabolic syndrome was found more frequently among children and adolescents with Middle Eastern and South Asian origins than Norwegians. Differences were found even after adjustment for age, sex and degree of obesity. This suggests that ethnic minorities may have an increased sensitivity to adiposity and need more aggressive prevention and treatment than their Norwegian counterparts.
Role of Endogenous Vintage Specific Depreciation in the Optimal Behavior of Firms
Authors: Saglam Cagri , Veliov Vladimir M.
Published: July 2008

This paper studies the firms' capital accumulation process in a vintage capital model with embodied technological change. We take into account that depreciation is endogenous and in particular associated with vintage specific maintenance expenditure. We prove that maintenance is a local substitute for investment as soon as the marginal cost of maintenance is strictly increasing. We show that maintenance and investment in new capital goods appear as complements with respect to the changes in productivity, cost of maintenance, fixed cost of operation, efficiency of maintenance services and appear as substitutes with respect to the price of new machines. Allowing for investment in old vintages, we determine that investment in old machines appears as a substitute of both investments in new machines and maintenance services. We end up by analyzing the effects of technological progress on optimal plans and prove that a negative anticipation effect can occur even without any market imperfections.
Comment on “Ellsberg's two‐color experiment, portfolio inertia and ambiguity”
Authors: Higashi Youichiro , Mukerji Sujoy , Takeoka Norio , Tallon Jean‐Marc
Published: July 2008

In the setting of Ellsberg's two‐color experiment, Mukerji and Tallon (2003) claim, without relying on particular representations, that ambiguity‐averse behavior implies subjective portfolio inertia. In this note, we point out using a counterexample that their axioms are not enough to establish the result. We fill in the gap in their argument using additional axioms and argue that these axioms are of their own interest in that they behaviorally separate two prominent models of ambiguity: the maximin expected utility and smooth ambiguity models.
Origin and evolution of magnetars
Authors: Ferrario Lilia , Wickramasinghe Dayal
Published: July 2008

We present a population synthesis study of the observed properties of the magnetars investigating the hypothesis that they are drawn from a population of progenitors that are more massive than those of the normal radio pulsars. We assume that the anomalous X-ray emission is caused by the decay of a toroidal or tangled up field that does not take part in the spin-down of the star. Our model assumes that the magnetic flux of the neutron star is distributed as a Gaussian in the logarithm about a mean value that is described by a power law , where Mp is the mass of the progenitor. We find that we can explain the observed properties of the magnetars for a model with Φ0 = 2 × 1025 G cm2 and γ= 5 if we suitably parametrize the time evolution of the anomalous X-ray luminosity as an exponentially decaying function of time. Our modelling suggests that magnetars arise from stars in the high-mass end (20 M⊙≤Mp≤ 45 M⊙) of this distribution. The lower mass progenitors are assumed to give rise to the radio pulsars.

The high value of γ can be interpreted in one of two ways. It may indicate that the magnetic flux distribution on the main sequence is a strong function of mass and that this is reflected in the magnetic fluxes of the neutron stars that form from this mass range (the fossil field hypothesis). The recent evidence for magnetic fluxes similar to those of the magnetars in a high fraction (∼25 per cent) of massive O-type stars lends support to such a hypothesis. Another possibility is that the spin of the neutron star is a strong function of the progenitor mass, and it is only for stars that are more massive than ∼20 M⊙ that magnetar-type fields can be generated by the α−ω dynamo mechanism (the convective dynamo hypothesis). In either interpretation, it has to be assumed that all or a subset of stars in the mass range ∼20–45 M⊙, which on standard stellar evolution models lead to black holes via the formation of a fall-back disc, must give rise to magnetars.

Unlike with the radio pulsars, the magnetars only weakly constrain the birth spin period, due to their rapid spin-down. Our model predicts a birthrate of ∼1.5–3 × 10−3 yr−1 for the magnetars.
PROTECTIVE CULTURES USED FOR THE BIOPRESERVATION OF HORSE MEAT FERMENTED SAUSAGE: MICROBIAL AND PHYSICOCHEMICAL CHARACTERIZATION
Authors: EL MALTI JAZILA , AMAROUCH HAMID
Published: July 2008

In this paper, 150 isolates, originating from horse meat, were subjected to step‐by‐step screening and characterization to search for potential protective cultures to be used in the meat industry. Isolates were first tested on their homofermentative and salt tolerance. Second, the antibacterial capacities toward Listeria monocytogenes were determined in an agar spot test. In total, 50% of the tested isolates were inhibitory toward Listeria monocytogenes. However, only 12 isolates produced a bacteriocin. Finally, three isolates with the strong bacteriocin activity were evaluated on their competitive nature by comparing their growth rate, acidifying character and lactic acid production at 15C under anaerobic conditions in a liquid broth. All three isolates combined a fast growth rate with a deep and rapid acidification caused by the production of high levels of lactic acid. Lactobacillus sakei was used as starter culture for producing sausage horse meat. In this study, fermentations were followed analyzing the microbiological and physicochemical aspects of this product. The sausages were characterized by an important microbial activity of lactic acid bacteria that resulted in a product with a final pH of about 4.56. No Listeria monocytogenes, Salmonella spp. or sulfite reducing clostridia were ever isolated from the raw materials or the fermented sausages during the maturation, underlining the microbial safety of this product. The final water activity of the product was 0.85. Starter cultures showed that Lactobacillus sakei was really efficient in reducing the amine production since this strain caused a quick pH drop during sausage fermentation.

PRACTICAL APPLICATIONS

A starter culture can be defined as a microbial preparation of large numbers of cells of at least one microorganism to be added to a raw material to produce a fermented food by accelerating and steering its fermentation process. The group of lactic acid bacteria (LAB) occupies a central role in these processes, and has a long and safe history of application and consumption in the production of fermented foods and beverages. They cause rapid acidification of the raw material through the production of organic acids, mainly lactic acid. Also, their production of acetic acid, ethanol, aroma compounds, bacteriocins, exopolysaccharides and several enzymes is of importance. The main reason for suitability of LAB is their natural origin, and they can contribute to food safety and/or offer one or more organoleptic, technological, nutritional or health advantages.
PERSISTENCE OF SALMONELLA SEROTYPES ON CHICKEN SKIN AFTER EXPOSURE TO KOSHER SALT AND RINSING*
Authors: OSCAR THOMAS P.
Published: July 2008

A series of experiments was undertaken to determine whether kosher salt reduces persistence of Salmonella serotypes that might cross‐contaminate chicken skin on the conveyor belt between the soaking and salting stations in a kosher processing line. The line was simulated in the laboratory because Salmonella could not be inoculated onto chickens in a commercial plant. Prevalence of Salmonella Typhimurium (0.5 log10 cfu) was reduced (P < 0.0001) from 93 to 21% by kosher salt followed by rinsing as compared with 48% for rinsing alone; results were similar for Salmonella Kentucky and for 12 and 24C. Salmonella Hadar was less persistent than the other serotypes. The beneficial effect of kosher salt on reducing persistence of Salmonella was not observed when initial pathogen levels were greater than 2.5 log10 cfu and when kosher salt was applied without rinsing. These results suggest that the application of kosher salt followed by rinsing is an important pathogen reduction step in the kosher processing of chickens.

PRACTICAL APPLICATIONS

Jewish dietary laws have been in existence for thousands of years but have received little attention from the scientific community for their potential beneficial effects for improving the quality and safety of poultry products. Practices employed during the kosher processing of poultry may be amendable to non‐kosher processing of poultry. Results of this study suggest that application of dry kosher salt might reduce attachment of Salmonella during processing and facilitate their removal by carcass washing. Further studies are needed to validate these results in a commercial plant and to evaluate other types of salt for their effects on Salmonella persistence and the potential application of the process to non‐kosher poultry.
EVALUATION OF AMOMUM SUBULATUM ROXB OIL AS A SOURCE OF BOTANICAL FUNGITOXICANT FOR THE PROTECTION OF MANGO FRUITS FROM FUNGAL ROTTING
Authors: DUBEY R.K. , KUMAR RAJESH , JAYA  , CHANSOURIA J.P.N. , DUBEY N.K.
Published: July 2008

The essential oil extracted from the leaves of Amomum subulatum Roxb. (Zingiberaceae) has been evaluated for efficacy in the control of mango fruit rotting due to fungal infections. The essential oil of A. subulatum exhibited absolute antifungal activity against two mango rotting fungi viz. Botryodiplodia theobromae Pat. and Colletotrichum gloeosporioides Penz, the common storage fungi causing stem end rot and anthracnose disease of mango fruits. The oil showed its absolute fungitoxicity at the minimum inhibitory concentration of 500 µL/L. Its fungitoxic potency did not alter even on a high inoculum density of the test fungi. The Amomum oil significantly enhanced the shelf life of mango fruits by controlling anthracnose disease as well as stem end rot for an additional five and six days, respectively. The oil also inhibited pectinase and cellulase enzymes secreted by the test fungi during pathogenesis and exhibited a wide range of fungitoxicity against 13 fungal isolates. Gas chromatography‐mass spectrometry analysis of the oil found 1, 8 cineole to be a major component. The LD50 of Amomum oil was found to be 22,070 mg/kg of body weight in mice (Mus musculus L.) when administered for acute oral toxicity. Keeping in view the side effects of synthetic fungicides, A. subulatum oil may be recommended as a botanical fungitoxicant of plant origin to control the rotting of mango fruits and to enhance their shelf life because of its nonmammalian toxicity and in vivo efficacy.
PREVALENCE OF SALMONELLA SPP. IN RAW AND COOKED FOODS IN ISFAHAN‐IRAN
Authors: JALALI MOHAMMAD , ABEDI DARYOUSH , POURBAKHSH SEYED ALI , GHOUKASIN KARINE
Published: July 2008

A total of 645 samples of raw and cooked foods were examined for the presence of Salmonella spp. Salmonella was detected in 43 (6.66%) of the samples. Salmonella was isolated from 24/134 (17.91%) of raw poultry, 3/56 (5.35%) of cooked poultry, 8/101 (7.92%) of raw meat, 2/118 (1.69%) of cooked meat, 1/3 (33.3%) of turkey, 2/5 (40.00%) of quail and 3/38 (7.89%) of vegetables. All samples taken from fish, yogurt, ready‐to‐eat olovieh salad, hamburger, mayonnaise souse and smallgoods were free of Salmonella. Of the 31 strains of Salmonella, 11 different serotypes were separated; among them S. enteritidis (29%) and S. baibouknown (29%) were the most frequent in raw foods. Furthermore, a high proportion of poultry was contaminated with Salmonella. Salmonella spp. were present in a small proportion of cooked foods, that is, they were not killed during the cooking process, or the contamination might have occurred after thermal treatment. These findings have a clear implication for public health, indicating the needs for improvement of hygienic condition in food processing centers.

PRACTICAL APPLICATIONS

To control and reduce human salmonellosis, periodic surveillance is necessary to determine the occurrence of Salmonella in various foods.Therefore, this study investigated the presence of Salmonella serovar in raw and cooked foods in one of the most populated provinces in Iran.

The data presented here will help the food industry, regulatory agencies and health policymakers target sectors which need additional monitoring or more effective control. As no documented information is provided on the sources of disease in Iran, this report may assist in further assessment of the sources of Salmonella in the human population. The number of salmonellosis cases will decrease following the introduction of mandatory Hazard Analysis and Critical Control Point (HACCP) in food industries. Hence, this study may convince governmental authority and private sectors to apply the HACCP system to ensure food safety. This study also underlines the need for adequate consumer protection against pathogens transmitted by foods in Iran.
BSAVA Manual of Rabbit Medicine and Surgery
Authors: Eatwell Kevin
Published: July 2008

BSAVA Manual of Rabbit Medicine and Surgery
 Anna Meredith and Paul Flecknell Published by the BSAVA, 2006, 2nd edition, paperback, 224 pages, Price 74.00, ISBN‐10: 090521496X; ISBN‐13: 978‐0905214962
Many‐valued Logic in Multistate and Vague Stochastic Systems
Authors: Sellers Kimberly F. , Singpurwalla Nozer D.
Published: July 2008

The state of the art in coherent structure theory is driven by two assertions, both of which are limiting: (1) all units of a system can exist in one of two states, failed or functioning; and (2) at any point in time, each unit can exist in only one of the above states. In actuality, units can exist in more than two states, and it is possible that a unit cansimultaneouslyexist in more than one state. This latter feature is a consequence of the view that it may not be possible to precisely define the subsets of a set of states; such subsets are calledvague. The first limitation has been addressed via work labeled ‘multistate systems’; however, this work has not capitalized on the mathematics of many‐valued propositions in logic. Here, we invoke its truth tables to define the structure function of multistate systems and then harness our results in the context of vagueness. A key contribution of this paper is to argue that many‐valued logic is a common platform for studying both multistate and vague systems but, to do so, it is necessary to lean on several principles of statistical inference.
Early intervention in bipolar disorder, part II: therapeutics
Authors: Salvadore Giacomo , Drevets Wayne C. , Henter Ioline D. , Zarate Carlos A. , Manji Husseini K.
Published: July 2008

Recent evidence has shown that early pharmacological and psychosocial treatment dramatically ameliorates poor prognosis and outcome for individuals with psychotic disorders, reducing conversion rates to full‐blown illness and decreasing symptom severity. In a companion paper, we discussed methodological issues pertaining to early intervention in bipolar disorder (BPD), reviewed clinical studies that focus on high‐risk subjects as well as first‐episode patients, and reviewed findings from brain imaging studies in the offspring of individuals with BPD as well as in first‐episode patients.

In this paper, we discuss how drugs that modulate cellular and neural plasticity cascades are likely to benefit patients in the very early stages of BPD, because they target some of the core pathophysiological mechanisms of this devastating illness. Cellular and molecular mechanisms of action of agents with neurotrophic and neuroplastic properties are discussed, with a particular emphasis on lithium and valproate. We also discuss their potential use as early intervention strategies for improving symptoms and functioning in patients in the earliest stages of BPD, as well as high‐risk individuals.
Family strengths: a potential determinant of the duration of untreated psychosis among hospitalized African‐American first‐episode patients
Authors: Goulding Sandra M. , Leiner Amy S. , Thompson Nancy J. , Weiss Paul S. , Kaslow Nadine J. , Compton Michael T.
Published: July 2008

Aim: Evidence suggests that treatment delay, represented by the duration of untreated illness (DUI) and the duration of untreated psychosis (DUP), may be a potentially powerful determinant of the early course of primary psychotic disorders. Yet, research on the predictors of treatment delay has only just begun. To date, there are virtually no empirical data on the relationship between family functioning and treatment delay in the context of first‐episode psychosis. In this study, it was hypothesized that family strengths would be inversely correlated with DUI and DUP; and families of patients with a short DUI/DUP would have greater family strengths than those of patients with a long DUI/DUP.

Methods: Family strengths (including pride and accord dimensions), DUI and DUP were assessed in 34 African Americans hospitalized for first‐episode psychosis and their respective 34 family members most involved in initiating care.

Results: The total score of the Family Strengths scale and the accord subscale score were significantly inversely correlated with both DUI and DUP, although the correlation between the pride subscale score and DUI/DUP was not as strong and failed to reach statistical significance. Similarly, the family members of patients with a short DUI/DUP had higher family strength scores than those of patients with a long DUI/DUP.

Conclusions: Given the dearth of research on the functioning of families beginning to initiate care for individuals with first‐episode psychosis, it is imperative to further clarify the role family characteristics may play in understanding treatment delay (DUI/DUP) and in the development of preventive interventions to facilitate early intervention for at‐risk populations.
Clinical and neurocognitive course in early‐onset psychosis: a longitudinal study of adolescents with schizophrenia‐spectrum disorders*
Authors: Wozniak Jeffrey R. , Block Erin E. , White Tonya , Jensen Jonathan B. , Schulz S. Charles
Published: July 2008

Aim: Adolescents with psychotic disorders show deficits in IQ, attention, learning and memory, executive functioning, and processing speed that are related to important clinical variables including negative symptoms, adaptive functioning and academics. Previous studies have reported relatively consistent deficits with varying relationships to illness status and symptoms. The goals of this study were to examine these relationships in a larger sample at baseline, and also to examine the longitudinal course of these deficits in a smaller subset of adolescents.

Method: Thirty‐six subjects, aged 10 to 17 years, were included at baseline. All had Diagnostic and Statistical Manual‐Fourth Edition diagnoses of schizophrenia, schizoaffective disorder, schizophreniform disorder and psychosis – not otherwise specified, as determined by Kiddie‐Schedule for Affective Disorders and Schizophrenia for School‐Age Children structured interviews. Patients were administered a neuropsychological battery, and Positive and Negative Syndrome Scale ratings were completed at baseline and again at 1 year (n = 14). Most participants were inpatients at baseline, and 13 of 14 were on atypical antipsychotic medication during both sessions.

Results: At baseline, the patients demonstrated impairments in working memory, processing speed, executive function and verbal learning. No significant cognitive change was detected at 1‐year follow‐up. In contrast, clinical symptoms were variable across 1 year, with an improvement in positive symptoms at 1 year. No relationships between clinical and cognitive symptoms were observed, with the exception of baseline IQ predicting negative symptoms at 1 year.

Conclusions: Young patients with schizophrenia‐spectrum disorders displayed neurocognitive impairments at baseline. Despite measurable fluctuations in clinical symptoms over the year, no significant changes were measured in cognition. Lower IQ at baseline was predictive of more negative symptoms at 1 year.
SU‐DD‐A1‐02: Parameter Optimization in Head and Neck IMRT for Elekta Linacs
Authors: Worthy D , Wu Q
Published: July 2008

Purpose: Planning and delivery in HN‐IMRT is challenging for Elekta linacs because of numerous constraints on beam delivery systems. The purpose of this study is to find a set of planning parameters that are applicable to most patients and optimal in terms of plan quality, delivery efficiency and dosimetric accuracy. Method and Materials: Four types of plans were created for each of 12 patients: ideal fluence optimization (FO), conventional two‐step optimization (TS) consisting of FO followed by MLC conversion, segment weight optimization (SW) and direct machine parameter optimization (DMPO). Maximum number of segments (NS) and minimum segment area (MSA) were varied in DMPO. Plan quality was evaluated based on score, dose distributions and dosimetric indices. Delivery efficiency was evaluated by irradiation time, and dosimetric accuracy by Mapcheck. Results: Plan quality deviates most from ideal FO for TS, with slight improvement for SW. DMPO is the closest to FO with the least variation among patients. NS of 80–160 in DMPO yield optimal plans. At larger NS (⩾80), plan quality decreases with MSA as expected, except for MSA <8cm2, which suggests presence of local minima in the DMPO algorithm. The irradiation time is strongly dependent on the plan segments (NSactual), weakly dependent on MUs, and independent of MSA. Typical plans with 79 segments and 8cm2 MSA have ∼747 MU and take ∼ 8 minutes to deliver; this increases to ∼13 minutes for 158 segments. Dosimetric accuracy is independent of DMPO parameters. Conclusion: The superior quality of DMPO plans makes it ideal for planning HN‐IMRT on Elekta linacs and its consistency allows development of class solutions. However, the vulnerability of local minima warrants such a study to systematically evaluate the effect of parameters in new planning techniques. The optimal set of parameters should be chosen to balance plan quality and delivery efficiency.
SU‐DD‐A1‐03: On the Quantification of the Dosimetric Accuracy of Collapsed Cone Convolution Superposition Algorithm for Small Lung Volumes Using IMRT
Authors: Gutiérrez A , Calvo O , Stathakis S , Rassiah‐Szegedi P , Esquivel C , Papanikolaou N
Published: July 2008

Purpose: To quantify the accuracy of a collapsed cone convolution superposition (CCCS) algorithm against Monte Carlo (MC) simulations for small lung lesions subject to electronic disequilibrium when very small segments are used during the IMRT optimization process. Method and Materials: IMRT plans for eleven (n=11) lung patients were created using Pinnacle3 7.6 planning system (TPS). Lung lesions measuring <3 cm in max. diameter and <27 cm3 were previously treated in our institution with SBRT techniques. The optimized intensity maps of each plan were then used to calculate the dose distributions using the CCCS algorithm. For each patient, seven optimized plans were created with varying MLC minimum segment sizes—0.25cm2 to 6cm2. The linear accelerator was modeled using MC code EGSnrc\BEAMnrc and verified against commissioned measured data. Intensity maps for each plan and the patient CT dataset from the TPS were exported to our MC software. All patients were planned using a 5‐field IMRT plan (Millennium 120‐leaf MLC and Varian 2100C 6MV beam). Dose distributions were calculated and normalized so that the isocenter receives 45.0Gy. Isodose distributions, DVH, and ROI statistics were used for comparison between the two calculation methods. Results: Comparison of the DVHs from Pinnacle3 and MC show similar target coverage between CCCS algorithm and MC. Differences in the minimum, maximum and mean dose of the PTV were less than ±5% while doses to critical structures agreed within ±6% for all cases investigated. Discrepancies in the dose to very small structures have been observed and due to volume effects between the two systems. Conclusion: Good agreement exists in the dose distributions predicted by the CCCS algorithm and MC method. The CCCS algorithm can accurately predict doses to small lung tumors.
SU‐DD‐A1‐04: Impact of Prescription Dose Gradient Discretization On Dose Painting
Authors: Bowen S , Flynn R , Bentzen S , Jeraj R
Published: July 2008

Purpose: Continuous prescription gradients may not be practical or necessary in the implementation of dose painting. This study optimized dose distributions to various discrete prescriptions and tested them for conformity to continuous, non‐uniform prescriptions. Method and Materials: The planning geometry consisted of a virtual cylindrical water phantom, containing a concentric heterogeneous tumor volume. The tumor was prescribed a uniform dose with boost subvolumes receiving escalated doses of 20, 50, or 100 % relative to background. Variable dose gradients extended up to 2 cm from the edge of 1 cm radius boost regions. Prescriptions were defined over gradient regions either continuously or in discrete steps. An iterative linear least squares method was employed to optimize helical tomotherapy dose distributions. Tumor, normal tissue, and subvolume importances were fixed relative to one another. Dosimetric evaluation included quantification of the volumetric percentage of boost and gradient regions whose plans conformed to prescriptions within 5 %. Results: Dose conformity to prescriptions in high dose contrast boost regions increased from 47 % of the volume for an infinite gradient to 100 % of the volume for a continuous gradient over 2 cm. In high contrast gradient regions of 1 cm radial distance, conformity ascended from 22 % of the volume for a single step to 91 % of the volume for a continuous gradient. To achieve dose conformity in 90 % of a 1 cm gradient region volume at low contrast, the prescription step size must be no larger than 0.5 cm. Conclusion: Results demonstrate that finite thresholds in prescription discretization exist to ensure planned dose conformity to continuous prescriptions. Adequate prescription gradient step size is dependent on beamlet dimensions, boost region size, and local gradient magnitude. Evaluation of prescription discretization may impact dose painting treatment planning protocols in its application to clinical cases.
SU‐DD‐A2‐03: Measurement of Skin Dose When Using FlexiShield® with the Axxent® Electronic Brachytherapy System
Authors: Kelley L , Axelrod S , Dutta A
Published: July 2008

Purpose: To study the skin surface dose delivered when FlexiShield, a flexible tungsten silicone sheet, is placed on the skin to shield personnel in the treatment room. This surface dose is compared to the surface dose delivered when no FlexiShield is present and when a silicone and tungsten‐only shielding is used. Method and Materials: Axxent FlexiShield is designed to shield the operator and other personnel from x‐ray radiation from the Axxent® Model S700 X‐ray Source. In order to attenuate fluorescence photons from tungsten in the shield, a barrier layer containing a tuned‐Z material was added to the silicone tungsten. A source holder was fabricated to hold FlexiShield against the surface of a PTW 34013 soft x‐ray ionization chamber while allowing for the placement of the x‐ray source at varying distances from the shield surface with water‐equivalent material filing the intervening space. The skin dose is defined as the dose measured by the ionization chamber whose active face is recessed ∼0.3mm from the FlexiShield inner surface. Results: For a source to skin distance of 3cm, the increased skin dose was measured to be 6.9% ± 0.5% for FlexiShield compared to no shielding. Silicon and tungsten‐only shielding produced an increased skin dose of 14.4% % ± 1.9%. These measurements compare well with MCNP5 simulations of the dose to the basal layer of the skin for a 3cm source to skin distance, which predict an increase of 7% for FlexiShield and 16% for a tungsten‐only shield for a simulated Axxent x‐ray source spectrum. Conclusion: The use of FlexiShield produces a slightly increased dose near the surface of the skin when compared no shielding used. The tuned‐Z layer added to FlexiShield decreases the measured dose near the skin surface by about a factor of two. Conflict of Interest: Research sponsored by Xoft, Inc.
SU‐DD‐A4‐01: Model‐Based Deconvolution for 4D PET
Authors: Li T , Li X , Yang Y , Li F , Heron D , Huq M
Published: July 2008

Purpose: An inherent problem in four‐dimensional (4D) PET imaging is the poor statistics in each phase, because the total coincidence events are divided into several phase bins during image acquisition. We propose in this work a simple but efficient image post‐processing method to improve the 4DPET image quality. Method and Materials: In this method, the entire acquired coincidence events are used for each individual phase to enhance their signal‐to‐noise ratios (SNRs). A summed 3D PET image is first obtained from the noisy 4DPET images, which represents the maximum SNR achievable. By deconvolving the 3D image with a deformable model derived from 4DCT, an improved 4DPET phase series can be obtained. For the best image quality, voice coaching was used to assure a regular and consistent breathing pattern during the course of PET and CT scans. The method was quantitatively evaluated with numerical and physical phantom experiments. Three clinical studies of pancreatic, lung and liver cancer patients were then carried out. Results: Numerical simulations showed that the model‐based 4D‐PET deconvolution method converged monotonically to the “ground truth” within a few iterations, and the SNR of the physical phantom images showed an increase of 83% over the conventional 4D PET without sacrificing spatial resolution. Similar performance was also observed for the patient study. Conclusion: We have developed a new method for improved 4D‐PET imaging. A salient feature of the method is that the coincidence events acquired at different time points are considered simultaneously when reconstructing each phase‐resolved image, leading to substantially improved 4D‐PET images.
SU‐DD‐A4‐03: Radiological Low Dose Measurement with An OSL Dosimetric System
Authors: Charron G , Deschenes S , Beaudoin G
Published: July 2008

Purpose: A method has been developed to measure low dose in radiology using the Landauer microStar OSL reader and microdot dosimeters. The depletion rate (the fraction of trapped electrons participating in the formation of the signal in a reading) has been established and the noise behavior following consecutive readings modeled. Method and Materials: While microdot dosimeters can be used to measure dose levels as low as 10 μGy, caution must be used as repeated expositions of these dose integrators rapidly limits the accuracy of the readings. Around 4000 doses were measured with a set of 362 dosimeters, each dosimeter being reused after reading. Each dosimeter was read multiple times, and a bank of nearly 70000 measurements was acquired. In order to obtain exposition dose, a method taking the multiple readings of the dosimeter into account was devised to estimate accumulated dose before and after exposition. The difference between these two values was the estimated exposition dose. It was found that low doses were more accurately measured when dosimeter accumulated dose was kept below 1500 μGy. This was achieved by exposing the microdot dosimeters to tungsten light for twelve hours. The dosimeter accumulated dose was reset to 30 μGy, without affecting significantly the dosimeter operating characteristics. Results: We found that the relation between the noise variance and the accumulated dose is quadratic for doses between 50 μGy and 10 mGy in the case of 90–140 kV exposure. Noise variance dictates that 200 readings be done in order to estimate the dosimeter rate of depletion with sufficient accuracy. The rate of depletion for the microdot dosimeter is −0.29% ± 0.03 (2 standard deviations). Conclusion: OSL allows measuring 10 μGy doses with an error of ± 3 μGy, but only with multiple readings after exposition and light induced resetting to zero.
SU‐EE‐A2‐02: Verification of Source and Collimator Configuration for Gamma‐Knife® Perfexion TM using Panormaric Imaging
Authors: Cho Y , van Prooijen M , Jaffray D , Islam M
Published: July 2008

Purpose: To develop a method of verifying the source and collimator configuration of Leksell Gamma Knife® Perfexion™. Method and Materials: The new model of stereotactic radiosurgery machine, Perfexion™, with modified source configuration allows extended reach of targets located in the cranial, neck and cervical regions. The control system allows automatic selection of appropriate built‐in collimator modules eliminating the need of time consuming manual installation of collimator helmets as in the older model of Gamma Knife system. However, the geometric configuration of collimator modules cannot be easily verified. The conventional method of exposing a film at the isocenter plane provides only a composited dose image, which is difficult to interpret in terms of the integrity of each individual source and corresponding collimator system. A method has been developed to capture a panoramic view of 192 Cobalt sources and corresponding images are utilized to verify the integrity and configuration of 192 sources. The images were acquired by exposing Gafchromic films wrapped around the surface of a specially designed 16 cm diameter cylindrical phantom. The phantom was mounted at the isocenter, with its axis aligned along the longitudinal axis of the couch. Depending upon the azimuthal angle of the source location, the shape and size of the source images were calculated and compared with the acquired images. Results: The images allowed clear identification of each of the 192 sources, verifying their integrity and selected collimator sizes. In this presentation the results of the source image alignment with respect to the expected collimator geometry will be described. In addition, the feasibility of relative dosimetric evaluation of the individual sources by the panoramic images will be presented. Conclusion: This method of source/collimator verification by panoramic imaging can provide an enhancement of commissioning and routine quality assurance of the Gamma Knife systems.
SU‐EE‐A2‐05: Tissue Ablation by Medium Intensity Focused Ultrasound for Breast Cancer Treatment: Preliminary Study
Authors: Hu Y , Podder T , Yan K , Winey B , Liao L , Parker K , Yu Y
Published: July 2008

Purpose: Focused ultrasonic radiation is known for its ability to induce thermal effects for therapy deep in tissue without surgical intervention. To design a medium intensity focused ultrasound (MIFU) system with distributed ultrasound transducers for breast cancer therapy, physical properties of the acoustic field must be fully characterized. Method and Materials: Custom made ultrasound transducers and driving system were calibrated with 1MHz sine wave input (1mW power). Calibrated gain of RF amplifier was utilized for ultrasound power control. Numerical simulation of the ultrasound radiation field was carried out with Rayleigh‐Sommerfold integral. The mathematical model for simulation was verified by measuring the acoustic output with a hydrophone. Heat distribution model was established based on the simulated ultrasound field. The heating experiment was implemented under different control strategies (duty cycle, pulse repetition) with tissue‐mimicking phantoms (12W each transducer) and animal tissue phantoms (20W each transducer). Results: The output power for MIFU can be controlled accurately with calibration of ultrasound driving system. The focal length of the transducer was found to be 6.9cm with resonance frequency 1MHz. At −6dB focal zone, the beam width was 0.3cm and the focal zone depth was about 3cm. The mathematical model of the ultrasound field was quite comparable with the measured results. In the simulation of ultrasound fields generated by two orthogonal transducers, the area of −6dB focal zone was 6mm×6mm. The mathematical model of thermal field distribution was verified with heating experiment. The temperature of the target point rose up to 65°C from ambient temperature within 3 minutes of sonication. Significant lesion was visible in the tissue ablation experiment. Conclusion: From the mathematical model and experimental results, it appears that MIFU can potentially be used for soft tissue ablation such as treating breast cancer with better skin sparing. Acknowledgement: Supported by NCI‐R33‐CA107860.
SU‐EE‐A3‐04: On‐Line CT‐Guided Adaptive Re‐Planning Based On Deformed Original Dose Distributions
Authors: Kang Y , Dong L , Bzdusek K , Vicic M , Zhang L , Zhang X , Mohan R
Published: July 2008

Purpose: Daily image‐guided setup based on soft tissue target may improve target coverage. However, when significant anatomical changes occur, a simple isocenter shift may not be adequate. In this study, we propose an online IMRT replanning strategy for prostate cancer which uses the deformed dose distributions from the original treatment plan as its objective. Method and Materials: The replanning procedure used was as follows: (1) the dose distribution on the planning CT was deformed to the daily CT and used as the reference objective dose distribution for IMRT replanning; (2) the prescription isodose line on the reference dose distribution was auto‐segmented and used as the fictitious “target volume” to set the initial MLC leaf positions; (3) we developed and implemented a voxel‐by‐voxel dose‐based cost function. The IMRT treatment plan was optimized using the direct machine parameter optimization algorithm to achieve the following goals: (a) inside the region enclosed by the original prescription dose line, the replanned dose distribution was optimized to match with the reference objective; (b) outside this region, the objective function was chosen to lower the dose value and to penalize the dose value exceeding the reference dose for each voxel. The replanning process does not need re‐auto‐segmentation of patient's anatomy, although re‐segmented anatomic contours were used to evaluate the effectiveness of this approach. Results: We compared the dose distributions and the DVHs of the original plan and the daily plans using (1) image‐guided setup based on prostate alignment, (2) deformed dose distribution from the original plan, and (3) our re‐planning method. We found that our re‐planning strategy matched well with the original plan. Conclusion: The replanning strategy using the original dose distribution as the goal for optimization produces dose distributions similar to the original approved plan and is an effective approach for on‐line CT‐guided adaptive radiotherapy.
SU‐EE‐A3‐05: A Protocol to Extend On‐Board Cone‐Beam CT Longitudinal Coverage with Multiple Orbits
Authors: Zheng D , Lu J , Wu J , Weiss E , Dogan N , Williamson J
Published: July 2008

Purpose: To develop, evaluate and optimize a protocol for acquiring on‐board cone‐beam CT (CBCT) images for larger longitudinal coverage than the maximum 14 cm coverage allowed by the Varian OBI half‐fan single‐orbit mode. Extended coverage is needed to fully image many standard pelvic, thoracic, and head‐and‐neck treatment volumes and to support such tasks as deformable image registration and dose reconstruction on serial CBCT images. Method and Materials: Multiple Varian single‐orbit data acquisitions separated by couch shifts were performed with small overlaps to provide the desired coverage. Simple approaches to aligning the two image volumes based on the nominal couch shift were validated against rigid image registration based upon orthogonal radiographic projections. An automatic algorithm was devised to decode the DICOM headers of the original slices and get corresponding position information, subsequently join the volumes, and finally rewrite the headers so that the resultant CBCT image set will be correlated as a single DICOM image volume. Validation of the volume reconstruction was performed with AP/PA radiographs and CatPhan QA phantom to evaluate the combining accuracy and the image quality in the abutment region where data sampling violates Tuy's data sufficiency condition. Results: The above protocol successfully provides OBI CBCT images with any desirable longitudinal coverage. An optimized protocol is implemented clinically, based upon the dose consequences and application simplicity. Conclusion: A practical method was developed to effectively extend the OBI longitudinal coverage, which improved the applicability of the OBI CBCT images in image‐guided adaptive radiation therapy.

This work was supported by NIH P01 CA116602.
SU‐EE‐A4‐01: Stereoscopic Visualization Of Diffusion Tensor Imaging Data: A Comparative Survey Of Several DTI Visualization Techniques
Authors: Raslan O , Schellingerhout D , Ketonen L , Debnam M , Kumar A , Wang J
Published: July 2008

Purpose: To compare several methods for displaying DTI data in MRI for clinical use. Method and Materials: A diffusion tensor imaging (DTI) visualization tool was developed at our institution by graphically displaying the principal eigenvector as a headless arrow, using either regular or stereoscopic LCD monitors. This tool utilizes stereoscopic vision to represent diffusion tensor's spatio‐directional information, while allowing color, the traditional tool for displaying directional information, to be used for other diffusion characteristics, such as functional anisotropy (FA). In this tool, the principal eigenvector at each voxel, Vmax, is depicted as a headless arrow, while a color scale is used to encode the FA index. We compared: a) grayscale FA map (GSFM), b) coded orientation map (CCOM), c) Vmax maps using regular non‐stereoscopic display (VM), and d) Vmax maps using stereoscopic display (VMS). A survey of clinical utility was performed by eight board‐certified neuroradiologists, using a paired comparison questionnaire format with forced and graded choices. Five representative cases were selected based on the typical brain tumor patient population at our institution. Results: Vmax map was favored over traditional methods of display in most of the cases (80% vs. 10%, 10% no preference). However, when stereoscopic (VMS) and the non‐stereoscopic (VM) modes were compared, VMS was preferred in 45% of them while VM was 35% and 30% had no preference. The main reason given for the preference of the stereoscopic DTI visualization tool (VMS, VM) to the conventional DTI visualization methods (CCOM and GSFM) was better delineation of white matter tract and improved 3D anatomy effect. Conclusion: DTI data displayed by our Vmax based display methodology seems to be preferred over traditional display methods in tests of clinical utility.