bluuebunny/crossref_metadata_2025 huggingface dataset:
Spin-polarized current effects in disordered La0.7Ba0.3MnO3 half-metal thin films
Authors: Barone C , Aruta C , Galdi A , Orgiani P , Quaranta O , Maritato L , Pagano S
Published: June 2010

We have investigated by means of noise spectroscopy the transport properties of half-metal La0.7Ba0.3MnO3 (LBMO) thin films deposited on MgO substrates. A reduced metal–insulator transition temperature and a peculiar noise behaviour are observed in the films grown on MgO substrates, when compared with similar films grown on SrTiO3 substrates. In particular, a large increase in noise is observed below the metal–insulator transition temperature, associated with a current induced reduction in the excess noise level. This finding is explained in terms of the spin torque effect between regions with depressed Curie temperatures among the ferromagnetic metallic domains. The proposed theoretical model, taking into account the half-metal character of manganites, describes well the experimental data.
LPG sensor based on complete inorganic n-Bi2S3-p-CuSCN heterojunction synthesized by a simple chemical route
Authors: Ladhe R D , Baviskar P K , Tan W W , Zhang J B , Lokhande C D , Sankapal B R
Published: June 2010

An effective and versatile room temperature soft chemical route was employed to deposit n-Bi2S3 films followed by p-CuSCN films onto fluorine doped tin oxide (FTO) coated glass substrates. Well optimized preparative parameters led to the formation of a good heterojunction between the n-Bi2S3 and p-CuSCN films without any post-annealing treatment. An interconnected microflake of CuSCN on to the nanocrystalline Bi2S3 film enables a high porous structure in the top layer. The device was completed by ensuring silver as a front and FTO as a back ohmic contact, and exposed to sense the liquefied petroleum gas (LPG) at room temperature (27 °C). The upper porous structure allowed enough room for the gas species to adsorb and de-adsorb easily at the interface. The device exhibited more than 70% response at 1370 ppm of LPG, and the process suggests the possibility to develop a room temperature LPG sensing device with a low cost chemical method.
Patterned synthesis of laterally oriented ultrafine ZnO nanowires by controlled metalorganic chemical vapour deposition
Authors: Lee D H , Son K , Park W I
Published: June 2010

Selective and lateral growth of ultrafine ZnO nanowires using metalorganic chemical vapour deposition (MOCVD) is studied. For selective growth of ZnO nanowires, oxidized substrates were patterned with Au layers, which serve as nucleation sites for the initial stage of ZnO nanowire growth. Electron microscopy confirmed that ultrafine ZnO nanowires with a mean diameter in the range ∼8–20 nm were rooted selectively in Au patterns and laterally extended to several micrometres on the substrate surfaces. Interestingly, nanowire bridges crosslinking the Au patterns or nanowire link-ups were frequently observed, indicating that self-organizing electrical interconnects and optical networks can be developed. Photoresponse measurements showed that exposure of the ultrafine ZnO nanowires to ultraviolet light rapidly increased the channel current from ∼150 to ∼400 nA at an applied bias voltage of 1 V.
Clowns Benefit Children Hospitalized for Respiratory Pathologies
Authors: Bertini Mario , Isola Elena , Paolone Giuseppe , Curcio Giuseppe
Published: June 2010

The study aims at evaluating health‐generating function of humor therapy in a hospital ward hosting children suffering from respiratory pathologies. The main scope of this study is to investigate possible positive effects of the presence of a clown on both the clinical evolution of the on‐going disease, and on some physiological and pain parameters. Forty‐three children with respiratory pathologies participated in the study: 21 of them belonged to the experimental group (EG) and 22 children to the control group (CG). During their hospitalization, the children of the EG interacted with two clowns who were experienced in the field of pediatric intervention. All participants were evaluated with respect to clinical progress and to a series of physiological and pain measures both before and after the clown interaction. When compared with the CG, EG children showed an earlier disappearance of the pathological symptoms. Moreover, the interaction of the clown with the children led to a statistically significant lowering of diastolic blood pressure, respiratory frequency and temperature in the EG as compared with the control group. The other two parameters of systolic pressure and heart frequency yielded results in the same direction, without reaching statistical significance. A similar health‐inducing effect of clown presence was observed on pain parameters, both by self evaluation and assessment by nurses. Taken together, our data indicate that the presence of clowns in the ward has a possible health‐inducing effect. Thus, humor can be seen as an easy‐to‐use, inexpensive and natural therapeutic modality to be used within different therapeutic settings.
Evolution and Function of the Plant Cell Wall Synthesis-Related Glycosyltransferase Family 8
Authors: Yin Yanbin , Chen Huiling , Hahn Michael G. , Mohnen Debra , Xu Ying
Published: June 2010

Carbohydrate-active enzyme glycosyltransferase family 8 (GT8) includes the plant galacturonosyltransferase1-related gene family of proven and putative α-galacturonosyltransferase (GAUT) and GAUT-like (GATL) genes. We computationally identified and investigated this family in 15 fully sequenced plant and green algal genomes and in the National Center for Biotechnology Information nonredundant protein database to determine the phylogenetic relatedness of the GAUTs and GATLs to other GT8 family members. The GT8 proteins fall into three well-delineated major classes. In addition to GAUTs and GATLs, known or predicted to be involved in plant cell wall biosynthesis, class I also includes a lower plant-specific GAUT and GATL-related (GATR) subfamily, two metazoan subfamilies, and proteins from other eukaryotes and cyanobacteria. Class II includes galactinol synthases and plant glycogenin-like starch initiation proteins that are not known to be directly involved in cell wall synthesis, as well as proteins from fungi, metazoans, viruses, and bacteria. Class III consists almost entirely of bacterial proteins that are lipooligo/polysaccharide α-galactosyltransferases and α-glucosyltransferases. Sequence motifs conserved across all GT8 subfamilies and those specific to plant cell wall-related GT8 subfamilies were identified and mapped onto a predicted GAUT1 protein structure. The tertiary structure prediction identified sequence motifs likely to represent key amino acids involved in catalysis, substrate binding, protein-protein interactions, and structural elements required for GAUT1 function. The results show that the GAUTs, GATLs, and GATRs have a different evolutionary origin than other plant GT8 genes, were likely acquired from an ancient cyanobacterium (Synechococcus) progenitor, and separate into unique subclades that may indicate functional specialization.
Icelandic and United States families of adolescents with asthma: predictors of health‐related quality of life from the parents’ perspective
Authors: Svavarsdottir Erla K , Burkhart Patricia V , Rayens Mary K , Orlygsdottir Brynja , Oakley Marsha G
Published: June 2010

Aims.  To evaluate cultural differences in sociodemographic factors, illness severity and parents’ perception of their adolescent’s quality of life for Icelandic and USA families of adolescents with asthma; and to determine predictors of parent‐rated quality of life.

Background.  Asthma is known to have an impact on the quality of life of affected adolescents and their families, but few studies have addressed parents’ perception of their adolescent’s health‐related quality of life.

Design.  Cross‐sectional exploratory study.

Method.  The study involved families of adolescents with asthma included 15 from Iceland and 15 from USA, recruited from paediatric practices. Parent and adolescent participants completed questionnaires; this study is based on the parent responses. Data were collected from January–May 2006.

Findings.  While parents from Iceland and USA were similar in demographic characteristics, parents from Iceland rated their children’s health‐related quality of life (PedsQLTM 3.0, Varni 1998) more positively than did USA parents, even though Icelandic parents were more likely than their USA counterparts to report that their adolescent’s asthma is severe. Significant predictors of parent‐rated quality of life included location (higher scores for Icelandic parents), gender (higher scores for parents of boys), exposure to second hand smoke in the home (higher scores for those not exposed) and frequency of troublesome wheezing (higher scores for lower frequency).

Conclusion.  Quality of life has been acknowledged as an essential health outcome measure. Even though gender difference was not found in asthma severity, parents of boys perceived their adolescent’s quality of life as more positive compared with parents of girls. It might be helpful for Icelandic and USA families to integrate into care delivery models, cultural differences in parent‐rated quality of life.

Relevance to clinical practice.  Asthma management interventions may improve quality of life for adolescents with asthma by reducing symptoms. Interventions promoting smoke‐free homes and enhanced self‐monitoring to prevent exacerbations may improve quality of life.
Insight and quality of life in long‐term hospitalized Japanese patients with chronic schizophrenia
Authors: Nakamae Takashi , Kitabayashi Yurinosuke , Okamura Aiko , Shibata Keisuke , Iwahashi Sachiko , Naka Fumiko , Morinobu Midori , Watanabe Mika , Narumoto Jin , Kitabayashi Masaki , Fukui Kenji
Published: June 2010

Aim:  The aim of the study was to investigate the relationship between insight and quality of life (QOL) and the respective predictive factors in long‐term hospitalized patients with chronic schizophrenia.

Methods:  The present subjects were 47 Japanese patients with chronic schizophrenia who were hospitalized for >1 year (mean hospitalization period, 9.8 years). Assessments were made using the Scale of Unawareness of Mental Disorder (SUMD) and the EuroQoL‐5 Dimensions (EQ‐5D) scale. Sociodemographic details and illness‐related variables were also evaluated, including use of the Positive and Negative Syndrome Scale.

Results:  There was no association between SUMD and EQ‐5D scores. Hallucinatory behavior was a predictor of good insight. Poor rapport was a predictor of bad insight. Poor attention was a predictor of bad QOL.

Conclusion:  The relationship between insight and QOL and the respective predictive factors might be different between acute and chronic stages. Further studies are needed to investigate how these changes occur.
Current development and future prospects in chemotherapy of tuberculosis
Authors: NUERMBERGER Eric L. , SPIGELMAN Melvin K. , YEW Wing Wai
Published: June 2010

Although treatment of drug‐susceptible tuberculosis (TB) under ideal conditions may be successful in ≥95% of cases, cure rates in the field are often significantly lower due to the logistical challenges of administering and properly supervising the intake of combination chemotherapy for 6–9 months. Success rates are far worse for multidrug‐resistant and extensively drug‐resistant TB cases. There is general agreement that new anti‐TB drugs are needed to shorten or otherwise simplify treatment for drug‐susceptible and multidrug‐resistant/extensively drug‐resistant‐TB, including TB associated with HIV infection. For the first time in over 40 years, a nascent pipeline of new anti‐TB drug candidates has been assembled. Eleven candidates from seven classes are currently being evaluated in clinical trials. They include novel chemical entities belonging to entirely new classes of antibacterials, agents approved for use against infections other than TB, and an agent already approved for limited use against TB. In this article, we review the current state of TB treatment and its limitations and provide updates on the status of new drugs in clinical trials. In the conclusion, we briefly highlight ongoing efforts to discover new compounds and recent advances in alternative drug delivery systems.
Fulminant community‐acquired pneumonia probably caused by Acinetobacter lwoffii
Authors: TOYOSHIMA Mikio , CHIDA Kingo , SUDA Takafumi
Published: June 2010

We describe a case of fulminant community‐acquired pneumonia probably caused by Acinetobacter lwoffii. A 63‐year‐old woman was admitted with an acute respiratory illness and consolidation in the right upper lobe. She deteriorated rapidly despite antibiotic therapy, and required ventilatory support. The patient died of multiple organ failure and intractable shock, 7 days after admission to hospital; her disease was probably caused by A. lwoffii.
Local‐ to continental‐scale variation in the richness and composition of an aquatic food web
Authors: Buckley Hannah L. , Miller Thomas E. , Ellison Aaron M. , Gotelli Nicholas J.
Published: June 2010

Aim  We investigated patterns of species richness and composition of the aquatic food web found in the liquid‐filled leaves of the North American purple pitcher plant, Sarracenia purpurea (Sarraceniaceae), from local to continental scales.

Location  We sampled 20 pitcher‐plant communities at each of 39 sites spanning the geographic range of S. purpurea– from northern Florida to Newfoundland and westward to eastern British Columbia.

Methods  Environmental predictors of variation in species composition and species richness were measured at two different spatial scales: among pitchers within sites and among sites. Hierarchical Bayesian models were used to examine correlates and similarities of species richness and abundance within and among sites.

Results  Ninety‐two taxa of arthropods, protozoa and bacteria were identified in the 780 pitcher samples. The variation in the species composition of this multi‐trophic level community across the broad geographic range of the host plant was lower than the variation among pitchers within host‐plant populations. Variation among food webs in richness and composition was related to climate, pore‐water chemistry, pitcher‐plant morphology and leaf age. Variation in the abundance of the five most common invertebrates was also strongly related to pitcher morphology and site‐specific climatic and other environmental variables.

Main conclusions  The surprising result that these communities are more variable within their host‐plant populations than across North America suggests that the food web in S. purpurea leaves consists of two groups of species: (1) a core group of mostly obligate pitcher‐plant residents that have evolved strong requirements for the host plant and that co‐occur consistently across North America, and (2) a larger set of relatively uncommon, generalist taxa that co‐occur patchily.
Rotifer species richness along an altitudinal gradient in the Alps
Authors: Obertegger Ulrike , Thaler Bertha , Flaim Giovanna
Published: June 2010

Aim  Biodiversity patterns along altitudinal gradients are less studied in aquatic than terrestrial systems, even though aquatic sites provide a more homogeneous environment independent of moisture constraints. We studied the altitudinal species richness pattern for planktonic rotifers in freshwater lakes and identified the environmental predictors for which altitude is a proxy.

Location  Two hundred and eighteen lakes of Trentino–South Tyrol (Italy) in the eastern Alps; lakes covered 98% (range 65–2960 m above sea level) of the altitudinal gradient in the Alps.

Methods  We performed: (1) linear regression between species richness and altitude to evaluate the general pattern, (2) multiple linear regression between species richness and environmental predictors excluding altitude to identify the most important predictors, and (3) linear regression between the residuals of the best model of step (2) and altitude to investigate any additional explanatory power of altitude. Selection of environmental predictors was based on limnological importance and non‐parametric Spearman correlations. We applied ordinary least squares regression, generalized linear, and generalized least squares modelling to select the most statistically appropriate model.

Results  Rotifer species richness showed a monotonic decrease with altitude independent of scale effects. Species richness could be explained (R2= 51%) by lake area as a proxy for habitat diversity, reactive silica and total phosphorus as proxies for productivity, water temperature as a proxy for energy, nitrate as a proxy for human influence and north–south and east–west directions as covariates. These predictors completely accounted for the species richness–altitude pattern, and altitude had no additional effect on species richness.

Main conclusions  The linear decrease of species richness along the altitudinal gradient was related to the interplay of habitat diversity, productivity, heat content and human influence. These factors are the same in terrestrial and aquatic habitats, but the greater environmental stability of aquatic systems seems to favour a linear pattern.
The Medieval World View: Contemplating the Mappamundi
Authors: Edson Evelyn
Published: June 2010

Looking at a medieval mappamundi (or world map) is a disorienting experience. Oriented to the east, displaying unfamiliar geographical forms and blanketed with images of strange animals and monstrous humans, it does not correspond to our modern concept of a world map. In the late 19th century scholars of the history of cartography dismissed medieval maps as a sign of ignorance. More recent studies have cast new light on these complex symbolic constructions, and scholars are searching for insights into medieval concepts of time and space, as well as clues to the ways in which knowledge of ancient geography was transmitted to the medieval intellectual world.
Oral squamous cell carcinoma and cultural oral risk habits in Vietnam
Authors: Priebe SL , Aleksejūnienė J , Zed C , Dharamsi S , Thinh DHQ , Hong NT , Cuc TTK , Thao NTP
Published: June 2010

To cite this article:
 
Int J Dent Hygiene 8, 2010; 159–168 DOI: 10.1111/j.1601‐5037.2010.00461.x Priebe SL, Aleksejūnienė J, Zed C, Dharamsi S, Thinh DHQ, Hong NT, Cuc TTK, Thao NTP. Oral squamous cell carcinoma and cultural oral risk habits in Vietnam.

Objectives:  In South‐Central Asia, 80% of head and neck cancers are found in the oral cavity and oropharynx. In Vietnam, oral cancer is often not being detected until people experience debilitating circumstances to normal oral function. The aims of the study were to explore the patterns of oral squamous cell carcinoma (OSCC) and its risk indicators, the structure of oral health care in Vietnam and trends in prevalence of cultural risk habits in southern Vietnamese patients.

Materials and Methods:  A retrospective clinical study was performed from 1 July 2005 to 1 April 2006 at Ho Chi Minh City Oncology hospital in Vietnam. Of the 161 cases, 147 subjects were diagnosed with OSCC, including 100 male and 47 female adults aged 24–85 years. Data were collected by a structured interview and clinical examination.

Results:  Over 40% of the women with OSCC reported chewing betel quid and the most prevalent risk habit in males was smoking (91.0%). Daily alcohol use was reported by 79.0% of males and 2.1% of females. Two‐thirds of the cases of OSCC were diagnosed at the 2nd and 3rd stage of cancer. The more advanced stages of cancer were observed in males than in females. The prevalence of tobacco and alcohol use in males with OSCC was higher in this study than in the previous Vietnamese studies.

Conclusion:  High frequency of risk habits in both genders was reported in OSCC Vietnamese patients. A trend of increased tobacco and alcohol use was observed in male OSCC patients. A lower prevalence of later staging in Vietnam was observed in this study than in earlier studies.
Up to D[eb]ate on Raising and Control Part 1: Properties and Analyses of the Constructions
Authors: Kirby Susannah , Davies William D. , Dubinsky Stanley
Published: June 2010

This is the first part of a two‐part article that reviews a number of the current debates regarding raising and control constructions. The issues addressed in this part include the syntactic attributes governing their distribution, the characterization of the relevant silent elements, and the empirical properties that may distinguish/unify the two classes of constructions (on either syntactic or semantic grounds).
Changing Spaces: Locating Public Space at the Intersection of the Physical and Digital
Authors: Alex de Freitas C.
Published: June 2010

It is widely held that the introduction of information communication technologies (ICTs) has resulted in significant changes to the organisation of cities, public spaces and everyday social life. Despite this, the extent and nature of these changes is something that is less than well established. This paper argues that conceptions of space and time have been radically altered by the new forms of accessibility and connectivity that are afforded by ICTs; in particular, wireless technologies, which continue to blur the boundaries between the public and private spaces of the city. The contemporary urban public spatial realm is neither physical nor digital, but an intricate and relational combination of the two. There is a need for a (re)conceptualisation of public space in light of this interconnection. Concepts such as ‘hybrid’ space might have been useful to some extent, but a fluid, less dualistic, more abstract mental image of public spaces is now required. The paper concludes that future research of urban public spaces must be situated in‐between the physical and digital and necessarily extend its scope beyond the traditional theoretical and methodological boundaries of the geographical discipline.
Aestheticizing Space: Art, Gentrification and the City
Authors: Mathews Vanessa
Published: June 2010

This article explores the relationship between art and gentrification at the urban scale. In particular, it maps shifting conceptualizations of this relationship through a focus on art, artists and arts spaces in the successive waves of gentrification. The first half of the article outlines the conceptualization of the arts in the first and second waves of gentrification, beginning with artist location preferences, detailing how and why these areas become attractive for higher income groups, and the agency prescribed to artists within the process. In the second half, the article places these findings in conversation with current debates taking place in the field surrounding third wave gentrification, in particular, how the arts are incorporated into public‐policy and urban regeneration with a focus on public art and arts infrastructure. The conclusion raises questions about how the incorporation of the arts in city programming complicates understandings of gentrification, and presents future avenues for research.
Designing Piezoelectric Interdigitated Microactuators Using Finite Element Analysis
Authors: Myers Oliver J. , Anjanappa M. , Freidhoff C.
Published: June 2010

This paper presents a methodology toward designing, analyzing, and optimizing piezoelectric interdigitated microactuators using multiphysics finite element analysis. The models used in this paper were based on a circularly interdigitated design that takes advantage of primarily the d33 electromechanical piezoelectric constant coefficient. Because of the symmetric nature of the devices, a small number of 2D axisymmetric parametric models were developed to characterize the behavior of the diaphragms. The parametric models offered a large range of possible results from a very small number of models. The variations in the design parameters and their effects on deflection were captured using these models. The models also showed that several of the design parameters were naturally coupled. Discrete models were then used to capture the variations in the key design parameters during fabrication. The numerical models correlate well to the maximum deflection of the experimental devices.
Registration‐based segmentation with articulated model from multipostural magnetic resonance images for hand bone motion animation
Authors: Chen Hsin‐Chen , Jou I‐Ming , Wang Chien‐Kuo , Su Fong‐Chin , Sun Yung‐Nien
Published: June 2010

Purpose

The quantitative measurements of hand bones, including volume, surface, orientation, and position are essential in investigating hand kinematics. Moreover, within the measurement stage, bone segmentation is the most important step due to its certain influences on measuring accuracy. Since hand bones are small and tubular in shape, magnetic resonance (MR) imaging is prone to artifacts such as nonuniform intensity and fuzzy boundaries. Thus, greater detail is required for improving segmentation accuracy. The authors then propose using a novel registration‐based method on an articulated hand model to segment hand bones from multipostural MR images.

Methods

The proposed method consists of the model construction and registration‐based segmentation stages. Given a reference postural image, the first stage requires construction of a drivable reference model characterized by hand bone shapes, intensity patterns, and articulated joint mechanism. By applying the reference model to the second stage, the authors initially design a model‐based registration pursuant to intensity distribution similarity, MR bone intensity properties, and constraints of model geometry to align the reference model to target bone regions of the given postural image. The authors then refine the resulting surface to improve the superimposition between the registered reference model and target bone boundaries.

Results

For each subject, given a reference postural image, the proposed method can automatically segment all hand bones from all other postural images. Compared to the ground truth from two experts, the resulting surface image had an average margin of error within 1 mm (mm) only. In addition, the proposed method showed good agreement on the overlap of bone segmentations by dice similarity coefficient and also demonstrated better segmentation results than conventional methods.

Conclusions

The proposed registration‐based segmentation method can successfully overcome drawbacks caused by inherent artifacts in MR images and obtain more accurate segmentation results automatically. Moreover, realistic hand motion animations can be generated based on the bone segmentation results. The proposed method is found helpful for understanding hand bone geometries in dynamic postures that can be used in simulating 3D hand motion through multipostural MR images.
Catching errors with in vivo EPID dosimetry
Authors: Mans A. , Wendling M. , McDermott L. N. , Sonke J.‐J. , Tielenburg R. , Vijlbrief R. , Mijnheer B. , van Herk M. , Stroom J. C.
Published: June 2010

The potential for detrimental incidents and the ever increasing complexity of patient treatments emphasize the need for accurate dosimetric verification in radiotherapy. For this reason, all curative treatments are verified, either pretreatment or in vivo, by electronic portal imaging device (EPID) dosimetry in the Radiation Oncology Department of the Netherlands Cancer Institute‐Antoni van Leeuwenhoek hospital, Amsterdam, The Netherlands. Since the clinical introduction of the method in January 2005 until August 2009, treatment plans of 4337 patients have been verified. Among these plans, 17 serious errors were detected that led to intervention. Due to their origin, nine of these errors would not have been detected with pretreatment verification. The method is illustrated in detail by the case of a plan transfer error detected in a intensity‐modulated radiotherapy (IMRT) rectum treatment. The EPID reconstructed dose at the isocenter was 6.3% below the planned value. Investigation of the plan transfer chain revealed that due to a network transfer error, the plan was corrupted. 3D analysis of the acquired EPID data revealed serious underdosage of the planning target volume: On average 11.6%, locally up to 20%. This report shows the importance of in vivo (EPID) dosimetry for all treatment plans as well as the ability of the method to assess the dosimetric impact of deviations found.
On the insensitivity of single field planar dosimetry to IMRT inaccuracies
Authors: Kruse Jon J.
Published: June 2010

Purpose

To report on the sensitivity of single field planar measurements in identifying IMRT plans with poor calculational accuracy.

Methods

Three IMRT plans for head and neck cancer were subjected to extensive quality assurance. The plans were recalculated on a cylindrical phantom and between eight and 18 low gradient points were measured in each plan with an ion chamber. Every point measured in these plans agreed to within 4% of the dose predicted by the planning system and the plans were judged acceptable for clinical use. Each plan was then reoptimized with aggressive dose constraints so that the new treatment fields were more highly modulated than the ones from the original plans. Very complex fields can be calculated less accurately and ion chamber measurements of these plans in the cylindrical phantom confirmed significant dosimetric errors—Several of the measured points in each plan differed from the calculated dose by more than 4%, with a maximum single deviation of 10.6%. These three plans were judged unacceptable for clinical use. All six plans (three acceptable, three unacceptable) were then analyzed with two means of individual field planar dosimetry: Portal imaging with an electronic portal imaging device (EPID) and an ion chamber array. Gamma analysis was performed on each set of planar measurements with 2%/2 mm distance to agreement (DTA) and 3%/3 mm DTA criteria to try to determine a gamma analysis threshold which would differentiate the flawed plans from the acceptable ones.

Results

With the EPID and 2%/2 mm DTA criteria, between 88.2% and 92.8% of pixels from the acceptable IMRT plans passed the gamma analysis, and between 87.5% and 91.9% passed for the unacceptable IMRT plans. With the ion chamber array and 2%/2 mm DTA criteria, between 92.4% and 94.9% of points in the acceptable plans passed the gamma analysis, while 86.8% to 98.3% of the points in the unacceptable plans passed the gamma analysis. The difference between acceptable and unacceptable plans was diminished further when gamma criteria were expanded to 3%/3 mm DTA. A fraction of pixels passing the gamma analysis was found to be a poor predictor of dosimetric accuracy with both planar dosimeters, as well as both sets of gamma criteria.

Conclusions

Deconstruction of an IMRT plan for field‐by‐field QA requires complex analysis methods such as the gamma function. Distance to agreement, a component of the gamma function, has clinical relevance in a composite plan but when applied to individual, highly modulated fields, it can mask important dosimetric errors. While single field planar dosimetry may comprise one facet of an effective QA protocol, gamma analysis of single field measurements is insensitive to important dosimetric inaccuracies of the overall plan.
Significant dose can be lost by extended delivery times in IMRT with x rays but not high‐LET radiations
Authors: Joiner Michael C. , Mogili Nagaraju , Marples Brian , Burmeister Jay
Published: June 2010

Purpose

To experimentally simulate IMRT delivery using two human cell modelsin vitro and test the hypothesis that a loss in effective dose resulting from the prolongation of megavoltage x‐ray treatment delivery time would be greatly reduced in corresponding IMRT simulations using higher‐LET radiation.

Methods

The effect of prolonging the delivery time of a treatment fraction was investigatedin vitro using human PC‐3 prostate and HGL21 glioblastoma tumor cell lines. Cells were irradiated with x rays from a conventional linear accelerator or with neutrons from a clinical radiotherapy beam and maintained at throughout. The delivery time for six closely spaced doses, simulating six multiple‐port segments, was varied from acute to 60 min for x‐ray irradiation, and acute to 120 min for neutron irradiation. Cell survival was measured following summed doses for the six segments of 0.5–6 Gy for x rays and 0.16–2 Gy for neutrons, covering the most likely range of dose per fraction used in clinical radiotherapy.

Results

Prolonging x‐ray delivery time (from initiation of segment 1 to initiation of segment 6) from 5 to 45 min resulted in a loss in effective total dose (in equivalent 2 Gy multifraction treatments) of 5.6% in the PC‐3 cell line and 11.7% in the HGL21 cell line. More clinically common prolongations of 5–30 and 5–15 min resulted in effective dose reductions of 3.8% and 1.7% for PC‐3, and 7.3% and 2.9% for HGL21. A loss of less than 0.5% in effective dose was observed for prolongations up to 45 min of similarly effective neutron irradiation of PC‐3 and HGL21 cells.

Conclusions

Prolonged delivery times of photon fractions could have a significant impact on treatment outcome especially for tumors with a low ratio and short repair halftime. These effects are significant at delivery times commonly associated with IMRT and are variable with cell type. X‐ray IMRT should therefore always be planned to minimize dose‐fraction delivery time. However, if IMRT treatments are delivered with high‐LET radiation, this considerably reduces the dependence of the biological effect on fraction delivery time even out to 2 h.
A method to correct the influence of carbon fiber couchtop and patient positioning device on image quality of cone beam CT
Authors: Men Kuo , Dai Jianrong , Li Minghui , Zhang Yin
Published: June 2010

Purpose

To evaluate the influence of carbon fiber couchtop and patient positioning devices on cone beam CT (CBCT) image quality and develop an effective method to correct the influence.

Methods

A standard CT phantom (Catphan 500) was used to evaluate the influence of iBeam evo carbon fiber couchtop on the quality of CBCT image obtained from an Elekta synergy machine. The evaluation indices were contrast‐to‐noise ratio (CNR), spatial resolution, image uniformity, and image noise. With using the Beer–Lambert law and the energy‐response function of the flat‐panel imager, a method was applied to deduct the image signal of the couchtop (and the positioning devices) from each projection image of a phantom/patient, and then used all corrected projection images to reconstruct a CBCT image. The performance of the correction method was evaluated using the CBCT images of a Catphan 500 phantom, a head‐and‐neck cancer patient, and a prostate cancer patient.

Results

In two phantom studies (the phantom to simulate a human head and neck and the one to simulate a human body), the CNR of the CBCT images obtained with the couchtop reduced 18.1% and 29.8%, respectively with respect to those obtained without the couchtop; meanwhile, the image uniformity reduced 16.4% and 24.1% due to the use of the carbon fiber couchtop. The couchtop also induced extra image noise (16.5% for the h&n phantom and 4.2% for the body phantom). However, CBCT imaging with the couchtop did not affect the spatial resolution. After applying the projection image correction, there was a significant improvement in CNR (by 19.5% and 25.8%), image uniformity (by 9.2% and 13.1%), and image noise (by 10.2% and 3.9%), with respect to CBCT images obtained with the couchtop.

Conclusions

The presence of the carbon fiber couchtop and the patient positioning devices can significantly impair CBCT image quality in terms of the CNR, the image uniformity, and the image noise. By removing the influence of the couchtop and the patient‐positioning devices from CB projection images, the correction method improves CBCT image quality and thus image guidance in radiotherapy.
Dose correction strategy for the optimization of volumetric modulated arc therapya)
Authors: Zhang Pengpeng , Yang Jie , Hunt Margie , Mageras Gig
Published: June 2010

Purpose

Dose calculation during optimization of volumetric modulated arc therapy (VMAT) is necessarily simplified to keep computation time manageably low; however the approximations used in the scatter dose calculation lead to discrepancy with more accurate dose calculation following optimization. The purpose of this study is to develop a dose correction strategy in optimization that can minimize the disagreement.

Methods

VMAT delivery is modeled using a number of static equispaced beams. Dose correction factors are associated with each beam and point inside the region of interest. is calculated as the ratio of dose obtained from the full scatter dose calculation over that from the partial scatter dose calculation in optimization. VMAT optimization algorithm is a multiple resolution approach. The dose correction factors are calculated at the beginning of each resolution and applied as multiplicative corrections to the partial scatter dose during optimization. Clinical cases for brain, prostate, paraspinal, and esophagus are utilized to evaluate the method. Treatment plans created with and without the correction scheme are normalized such that the complication rates of organs at risk (OARs) are comparable. The resulting planning target volume (PTV) mean doses are used to compare plan quality.

Results

The difference between the dose calculated at the end of optimization and at the end of the final forward dose calculation is reduced from 7% and 5% for the PTV and OAR mean doses without correction to approximately 1% with correction. Applying dose correction during optimization saves planners 2–4 h in average in treatment planning, and has a positive impact on plan quality, evidenced by a noticeably higher PTV mean dose: 2.1%, 2.4%, 0.5%, and 9.3% of the corresponding prescription dose in the brain, esophagus, prostate, and paraspinal cases, respectively.

Conclusions

When dose correction is applied during optimization, dose discrepancies between optimization and full dose calculation are reduced. Integrating dose correction in VMAT optimization allows planners to adjust the optimization constraints more easily and confidently during optimization and has the potential to improve plan quality.
Age‐ and race‐dependence of the fibroglandular breast density analyzed on 3D MRI
Authors: Nie Ke , Su Min‐Ying , Chau Man‐Kwun , Chan Siwa , Nguyen Hoanglong , Tseng Tiffany , Huang Yuhong , McLaren Christine E. , Nalcioglu Orhan , Chen Jeon‐Hor
Published: June 2010

Purpose

The purpose of this study was to evaluate the age‐ and race‐dependence of the breast fibroglandular tissue density based on three‐dimensional breast MRI.

Methods

The normal breasts of 321 consecutive patients including Caucasians, Asians, and Hispanics were studied. The subjects were separated into three age groups: Younger than 45, between 45 and 55, and older than 55. Computer algorithms based on body landmarks were used to segment the breast, and fuzzy c‐means algorithm was used to segment the fibroglandular tissue. Linear regression analysis was applied to compare mean differences among different age groups and race/ethnicity groups. The obtained parameters were not normally distributed, and the transformed data, natural log (ln) for the fibroglandular tissue volume, and the square root for the percent density were used for statistical analysis.

Results

On the average, the transformed fibroglandular tissue volume and percent density decreased significantly with age. Racial differences in mean transformed percent density were found among women older than 45, but not among women younger than 45. Mean percent density was higher in Asians compared to Caucasians and Hispanics; the difference remained significant after adjustment for age, but not significant after adjusted for both age and breast volume. There was no significant difference in the density between the Caucasians and the Hispanics.

Conclusions

The results analyzed using the MRI‐based method show age‐ and race‐dependence, which is consistent with literature using mammography‐based methods.
Extraction of tube current values from DICOM CT images for patient dose estimation
Authors: Lin Pei‐Jan Paul , Kubo Takeshi , Krishnapillai Rajeev
Published: June 2010

Purpose

When CT examinations are conducted with automatic mA modulation (‐axis modulation), the tube current (mA) may vary from one CT slice to next, i.e., mA is no longer a fixed constant. Hence, patient dose calculation is no longer a straightforward process. The purpose of this article is to show how the mA information may be extracted from DICOM CT images without having to manually read off “mA values” from the displayed images one at a time.

Methods

A statistical programming language called “R,” which is capable of reading DICOM files, is employed to extract the mA values from a series of DICOM CT images. This task is carried out with a “script” designed to read the mA values from the DICOM CT images and generate a file in “delimited ASCII” format. This file can be imported into a spreadsheet program such as Excel (a Microsoft spreadsheet program) for further processing, calculation, and chart production. A CT examination of the chest was selected to carry out this operation for demonstration purposes.

Results

The “script” generated a delimited ASCII “file” which is a two column data sheet with the slice location and its corresponding mA values. After the file is imported into Excel for calculation, and with other pertinent scan parameters, the average mA can now be plugged into a CT dosimetry calculation program such as ImPACT for calculation of CTDIw, CTDIvol, dose‐length‐product, and critical organ doses. Furthermore, a graphical presentation of the “mA” vs slice location can be produced with Excel. The chart generated by Excel shows the variation in tube current as a function of slice location. The area under the mA curve is equal to a rectangle of . Here, the distance is the range covered by the CT scan.

Conclusions

The script that the authors have written is able to extract mA values from DICOM CT images, generating a delimited ASCII file for further processing with Microsoft Excel spreadsheet program. After the DICOM images are imported into a personal computer, this semiautomated process of extracting mA values enabled the authors to perform dose calculation for patients undergoing CT examination scanned with automatic mA modulation control.
Determination of exit skin dose for intracavitary accelerated partial breast irradiation with thermoluminescent dosimeters
Authors: Raffi Julie A. , Davis Stephen D. , Hammer Cliff G. , Micka John A. , Kunugi Keith A. , Musgrove Jana E. , Winston John W. , Ricci‐Ott Terresa J. , DeWerd Larry A.
Published: June 2010

Purpose

Intracavitary accelerated partial breast irradiation (APBI) has become a popular treatment for early stage breast cancer in recent years due to its shortened course of treatment and simplified treatment planning compared to traditional external beam breast conservation therapy. However, the exit dose to the skin is a major concern and can be a limiting factor for these treatments. Most treatment planning systems (TPSs) currently used for high dose‐rate (HDR) brachytherapy overestimate the exit skin dose because they assume a homogeneous water medium and do not account for finite patient dimensions. The purpose of this work was to quantify the TPS overestimation of the exit skin dose for a group of patients and several phantom configurations.

Methods

The TPS calculated skin dose for 59 HDR APBI patients was compared to the skin dose measured with LiF:Mg,Ti thermoluminescent dosimeters (TLDs). Additionally, the TPS calculated dose was compared to the TLD measured dose and the Monte Carlo (MC) calculated dose for eight phantom configurations. Four of the phantom configurations simulated treatment conditions with no scattering material beyond the point of measurement and the other four configurations simulated the homogeneous scattering conditions assumed by the TPS. Since the calibration TLDs for this work were irradiated with and the experimental irradiations were performed with , experiments were performed to determine the intrinsic energy dependence of the TLDs. Correction factors that relate the dose at the point of measurement (center of TLD) to the dose at the point of interest (basal skin layer) were also determined and applied for each irradiation geometry.

Results

The TLD intrinsic energy dependence for relative to was . The TPS overestimated the exit skin dose by an average of 16% for the group of 59 patients studied, and by 9%–15% for the four phantom setups simulating treatment conditions. For the four phantom setups simulating the conditions assumed by the TPS, the TPS calculated dose agreed well with the TLD and MC results (within 3% and 1%, respectively). The inverse square geometry correction factor ranged from 1.023 to 1.042, and an additional correction factor of 0.978 was applied to account for the lack of charged particle equilibrium in the TLD and basal skin layer.

Conclusions

TPS calculations that assume a homogeneous water medium overestimate the exit skin dose for intracavitary APBI treatments. It is important to determine the actual skin dose received during intracavitary APBI to determine the skin dose‐response relationship and establish dose limits for optimal skin sparing. This study has demonstrated that TLDs can measure the skin dose with an expanded uncertainty of 5.6% when the proper corrections are applied.
A randomization approach to handling data scaling in nuclear medicine
Authors: Bai Chuanyong , Conwell Richard , Kindem Joel
Published: June 2010

Purpose

In medical imaging, data scaling is sometimes desired to handle the system complexity, such as uniformity calibration. Since the data are usually saved in short integer, conventional data scaling will first scale the data in floating point format and then truncate or round the floating point data to short integer data. For example, when using truncation, scaling of 9 by 1.1 results in 9 and scaling of 10 by 1.1 results in 11. When the count level is low, such scaling may change the local data distribution and affect the intended application of the data.

Methods

In this work, the authors use an example gated cardiac SPECT study to illustrate the effect of conventional scaling by factors of 1.1 and 1.2. The authors then scaled the data with the same scaling factors using a randomization approach, in which a random number evenly distributed between 0 and 1 is generated to determine how the floating point data will be saved as short integer data. If the random number is between 0 and 0.9, then 9.9 will be saved as 10, otherwise 9. In other words, the floating point value 9.9 will be saved in short integer value as 10 with 90% probability or 9 with 10% probability. For statistical analysis of the performance, the authors applied the conventional approach with rounding and the randomization approach to 50 consecutive gated studies from a clinical site.

Results

For the example study, the image reconstructed from the original data showed an apparent perfusion defect at the apex of the myocardium. The defect size was noticeably changed by scaling with 1.1 and 1.2 using the conventional approaches with truncation and rounding. Using the randomization approach, in contrast, the images from the scaled data appeared identical to the original image. Line profile analysis of the scaled data showed that the randomization approach introduced the least change to the data as compared to the conventional approaches. For the 50 gated data sets, significantly more studies showed quantitative differences between the original images and the images from the data scaled by 1.2 using the rounding approach than the randomization approach [46/50 (92%) versus 3/50 (6%), ]. Likewise, significantly more studies showed visually noticeable differences between the original images and the images from the data scaled by 1.2 using the rounding approach than randomization [29/50 (58%) versus 1/50 (2%), ].

Conclusions

In conclusion, the proposed randomization approach minimizes the scaling‐introduced local data change as compared to the conventional approaches. It is preferred for nuclear medicine data scaling.