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1.
Phys Rev Lett ; 125(18): 183003, 2020 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-33196257

RESUMO

We show that jet emission from a Bose condensate with periodically driven interactions, also known as "Bose fireworks", contains essential information on the condensate wave function, which is difficult to obtain using standard detection methods. We illustrate the underlying physics with two examples. When condensates acquire phase patterns from external potentials or from vortices, the jets display novel substructure, such as oscillations or spirals, in their correlations. Through a comparison of theory, numerical simulations, and experiments, we show how one can quantitatively extract the phase and the helicity of a condensate from the emission pattern. Our work, demonstrating the strong link between jet emission and the underlying quantum system, bears on the recent emphasis on jet substructure in particle physics.

2.
Qual Life Res ; 28(11): 2957-2967, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31399859

RESUMO

PURPOSE: Central cancer registries collect data and provide population-level statistics that can be tracked over time; yet registries may not capture the full range of clinically relevant outcomes. Patient-generated health data (PGHD) include health/treatment history, biometrics, and patient-reported outcomes (PROs). Collection of PGHD would broaden registry outcomes to better inform research, policy, and care. However, this is dependent on the willingness of patients to share such data. This study examines cancer survivors' perspectives about sharing PGHD with central cancer registries. METHODS: Three U.S. central registries sampled colorectal, non-Hodgkin lymphoma, and metastatic breast cancer survivors 1-4 years after diagnosis, recruiting them via mail to participate in one of seven focus groups (n = 52). Group discussions were recorded, transcribed, and thematically analyzed. RESULTS: Most survivor-participants were unaware of the existence of registries. After having registries explained, all participants expressed their willingness to share PGHD with them if treated confidentially. Participants were willing to provide information on a variety of topics (e.g., medical history, medications, symptoms, financial difficulties, quality of life, biometrics, nutrition, exercise, and mental health), with a focus on long-term effects of cancer and its treatment. Participants' preferred mode for providing data varied. Participants were also interested in receiving information from registries. CONCLUSIONS: Our results suggest that registry-based collection of PGHD is acceptable to most cancer survivors and could facilitate registry-based efforts to collect PGHD/PROs. Central cancer registry-based collection of PGHD/PROs, especially on long-term effects, could enhance registry support of cancer control efforts including research and population health management.


Assuntos
Sobreviventes de Câncer/psicologia , Coleta de Dados/métodos , Gerenciamento de Dados/métodos , Atenção à Saúde/métodos , Medidas de Resultados Relatados pelo Paciente , Qualidade de Vida/psicologia , Sistema de Registros/normas , Feminino , Grupos Focais , Humanos , Masculino , Pessoa de Meia-Idade
3.
Phys Rev Lett ; 121(3): 030402, 2018 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-30085820

RESUMO

We demonstrate a density-dependent gauge field, induced by atomic interactions, for quantum gases. The gauge field results from the synchronous coupling between the interactions and micromotion of the atoms in a modulated two-dimensional optical lattice. As a first step, we show that a coherent shaking of the lattice in two directions can couple the momentum and interactions of atoms and break the fourfold symmetry of the lattice. We then create a full interaction-induced gauge field by modulating the interaction strength in synchrony with the lattice shaking. When a condensate is loaded into this shaken lattice, the gauge field acts to preferentially prepare the system in different quasimomentum ground states depending on the modulation phase. We envision that these interaction-induced fields, created by fine control of micromotion, will provide a stepping stone to model new quantum phenomena within and beyond condensed matter physics.

4.
Phys Rev Lett ; 121(24): 243001, 2018 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-30608768

RESUMO

A Bose condensate, subject to periodic modulation of the two-body interactions, was recently observed to emit matter-wave jets resembling fireworks [Nature (London) 551, 356 (2017)NATUAS0028-083610.1038/nature24272]. In this Letter, combining experiment with numerical simulation, we demonstrate that these "Bose fireworks" represent a late stage in a complex time evolution of the driven condensate. We identify a "density wave" stage which precedes jet emission and results from the interference of matter waves. The density waves self-organize and self-amplify without breaking long range translational symmetry. This density wave structure deterministically establishes the template for the subsequent patterns of the emitted jets. Moreover, our simulations, in good agreement with experiment, address an apparent asymmetry in the jet pattern, and show that it is fully consistent with momentum conservation.

5.
Maturitas ; 103: 23-31, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28778328

RESUMO

OBJECTIVE: This study examines mean length of stay (LOS) and rates of emergency bed days during the course of the Reshaping Care for Older People (RCOP) programme in Glasgow City. METHODS: An ecological small-area study design was used. Standardised monthly rates of bed days and LOS were calculated, between April 2011 and March 2015, for residents of Glasgow City aged 65 years and over. Multilevel negative binomial models for the square root of each outcome nested by datazone were created, adjusting for sex, 5-year age group, area-level deprivation, season, month and month squared. Relative index of inequality (RII) and slope index of inequality (SII) were calculated for each year and the trend was examined. RESULTS: The rate of bed days first rose then fell during the study period, while LOS first fell then rose. Relative risk (RR) of an additional bed day was greater for males (RR=1.14 (1.12, 1.16)) and increased with increasing age group. There was no gender difference in LOS. Bed days per head of population first increased then fell; for 12-month period RR=1.01 (0.98, 1.05) and for 12-month period squared, RR=0.999 (0.999, 0.999). RII and SII for rate of bed days per head of population were significant, though not for LOS. SII for bed days per head of population did not change significantly over time, while RII reduced at the 87% level of confidence. CONCLUSIONS: The results suggest a reduction in secondary care use by older people during the RCOP programme, and a possible reduction in socioeconomic inequalities in bed days in the longer term.


Assuntos
Hospitalização/tendências , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Coleta de Dados , Feminino , Humanos , Lactente , Recém-Nascido , Masculino , Pessoa de Meia-Idade , Risco , Escócia , Fatores Socioeconômicos , Adulto Jovem
6.
Phys Rev Lett ; 118(22): 220401, 2017 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-28621968

RESUMO

We address band engineering in the presence of periodic driving by numerically shaking a lattice containing a bosonic condensate. By not restricting to simplified band structure models we are able to address arbitrary values of the shaking frequency, amplitude, and interaction strengths g. For "near-resonant" shaking frequencies with moderate g, a quantum phase transition to a finite momentum superfluid is obtained with Kibble-Zurek scaling and quantitative agreement with experiment. We use this successful calibration as a platform to support a more general investigation of the interplay between (one particle) Floquet theory and the effects associated with arbitrary g. Band crossings lead to superfluid destabilization, but where this occurs depends on g in a complicated fashion.

7.
Phys Rev Lett ; 115(24): 240401, 2015 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-26705613

RESUMO

In this paper we follow the analysis and protocols of recent experiments, combined with simple theory, to arrive at a physical understanding of quasi-condensation in two dimensional Fermi gases. A key signature of quasi-condensation, which contains aspects of Berezinskii-Kosterlitz-Thouless behavior, is a strong zero momentum peak in the pair momentum distribution. Importantly, this peak emerges at a reasonably well defined onset temperature. The resulting phase diagram, pair momentum distribution, and algebraic power law decay are compatible with recent experiments throughout the continuum from BEC to BCS.

8.
Clin Ter ; 166(3): 105-9, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26152616

RESUMO

BACKGROUND AND AIMS: Obesity has taken the 21st century by storm, posing negative effects on of the various facades of health, healthcare and global economy. With regards to pulmonary performance, numerous studies have proven the detrimental effects of obesity while reinstating the positive effects of weight loss on overall pulmonary function. However, effects of exercise on pulmonary function and correlation between changes in pulmonary function test with weight loss have yet to be described. We performed a prospective interventional study to determine the effects of regular exercise on Pulmonary Function Tests (PFT) and ascertain the relationship between weight loss and change in PFT in obese patients. MATERIALS AND METHODS: Twenty-five obese patients were enrolled, giving an 80% power of study. Baseline weight and PFT consisting of FEV1, FVC, TLC, mean ERV and VC were recorded prior to commencement of the 8 week long Standard Exercise Regimen (SER). PFT and weight were recorded again at the end of 8 weeks. RESULTS: All parameters of the PFT studied improved significantly with exercise. The participants lost an average of 1kg of body weight post-exercise (p<0.0005). The correlations between mean changes in weight and PFT were negligible. CONCLUSIONS: A period of supervised regular exercise improves the pulmonary function of obese patients and this improvement is independent of the amount of weight loss. Hence, SER should be recommended to all obese patients, especially when bariatric surgery is desired.


Assuntos
Exercício Físico/fisiologia , Obesidade/fisiopatologia , Obesidade/terapia , Peso Corporal , Humanos , Estudos Prospectivos , Testes de Função Respiratória
9.
Eur J Public Health ; 25(3): 464-6, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25788475

RESUMO

The adolescent population of Glasgow, the city with the highest mortality in the UK, has a higher prevalence of risk behaviours than elsewhere in Scotland. Previous research has highlighted the importance of social context in interpreting such differences. Contextual variables from the 2010 Health Behaviour in School-aged Children Scotland survey were analysed. Glaswegian adolescents were more likely to live in low socioeconomic status, single-parent or step-families, or with neither parent in employment, less likely to share family meals, more likely to buy lunch outside school, and spend time with friends after school and in the evenings. They also had a poorer perception of their local neighbourhood. Family affluence only partially explained these differences.


Assuntos
Comportamento do Adolescente , Características de Residência/estatística & dados numéricos , Assunção de Riscos , Classe Social , Meio Social , Adolescente , Família , Feminino , Humanos , Masculino , Pais , Fatores de Risco , Escócia , Fatores Socioeconômicos
10.
Dalton Trans ; 44(6): 2819-26, 2015 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-25515251

RESUMO

CaMg(2)AlN(3) was synthesized in a closed system by solid state reaction from binary nitrides. Structure refinements based on powder X-ray diffraction data suggested ambiguity about the occupancy of magnesium and aluminum tetrahedral sites. Solid-state (27)Al and (25)Mg NMR studies were used to adjudicate amongst possible space groups. With reference to projector augmented wave calculations of the quadrupolar coupling constants, the measured values of CQ and the numbers of crystallographically inequivalent Al and Mg sites indicate that CaMg(2)AlN(3) crystallizes in the space group P6(3)/mmc with partial occupancy of the distorted tetrahedral Al site and possibly also mixing of Mg(2+) and Al(3+) ions on opposite sites. The compound obtained by synthesis with a flux shows orange defect-related luminescence at room temperature.

11.
Eur J Pain ; 19(1): 77-84, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24807819

RESUMO

BACKGROUND: There is considerable variation in adolescent pain prevalence across epidemiological studies, with limited information on pain-related behaviours among adolescents, including medicine use. The aims of this study were (1) to examine the prevalence of recurrent pain among 15-year-old adolescents internationally; (2) to investigate the association between recurrent pain and medicine use behaviours among boys and girls; and (3) to evaluate the consistency of these associations across countries. METHODS: The World Health Organization (WHO) collaborative international Health Behaviour in School-aged Children 2009/2010 study collects data about self-reported aches and medicine use from 36,762 15-year-old adolescents from 22 countries/regions in Europe and the United States. Multi-level multivariate logistic regression, stratified by gender, was used to analyse the association between recurrent pain and medicine use for headache, stomachache, nervousness and difficulties in getting to sleep. RESULTS: More than 30% of adolescents reported recurrent headache, almost 30% recurrent backache and approximately 20% recurrent stomachache. Although pain prevalence and medicine use for aches were much higher for girls, the association between pain and medicine use was similarly strong for both genders. Adolescents with recurrent pain are more likely to use medicines also for non-corresponding pain, nervousness and difficulties in getting to sleep. The association between recurrent pain and medicine use was consistent across countries despite large-country differences in the prevalence of recurrent pain and medicine use. CONCLUSIONS: Recurrent pain in adolescence is common cross-nationally. Adolescents with recurrent pain are more likely to use medicine in general. Recurrent pain and medicine use should be addressed in adolescent health policies.


Assuntos
Dor Abdominal/tratamento farmacológico , Dor nas Costas/tratamento farmacológico , Cefaleia/tratamento farmacológico , Dor/tratamento farmacológico , Dor Abdominal/epidemiologia , Adolescente , Dor nas Costas/epidemiologia , Feminino , Cefaleia/epidemiologia , Humanos , Masculino , Dor/epidemiologia , Prevalência , Recidiva , Fatores Sexuais , Inquéritos e Questionários
12.
J Public Health (Oxf) ; 37(1): 107-15, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24917568

RESUMO

BACKGROUND: This study examined urban-rural and socioeconomic differences in adolescent toothbrushing. METHODS: The data were modelled using logistic multilevel modelling and the Markov Chain Monte Carlo method of estimation. Twice-a-day toothbrushing was regressed upon age, family affluence, family structure, school type, area-level deprivation and rurality, for boys and girls separately. RESULTS: Boys' toothbrushing was associated with area-level deprivation but not rurality. Variance at the school level remained significant in the final model for boys' toothbrushing. The association between toothbrushing and area-level deprivation was particularly strong for girls, after adjustment for individuals' family affluence and type of school attended. Rurality too was independently significant with lower odds of brushing teeth in accessible rural areas. CONCLUSION: The findings are at odds with the results of a previous study which showed lower caries prevalence among children living in rural Scotland. A further study concluded that adolescents have a better diet in rural Scotland. In total, these studies highlight the need for an examination into the relative importance of diet and oral health on caries, as increases are observed in population obesity and consumption of sugars.


Assuntos
Comportamento do Adolescente/psicologia , Comportamentos Relacionados com a Saúde , População Rural/estatística & dados numéricos , Escovação Dentária/estatística & dados numéricos , População Urbana/estatística & dados numéricos , Adolescente , Fatores Etários , Estudos Transversais , Feminino , Humanos , Masculino , Escócia , Fatores Sexuais , Fatores Socioeconômicos
13.
Phys Rev Lett ; 113(12): 125301, 2014 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-25279634

RESUMO

We present numerical simulations of phase imprinting experiments in ultracold trapped Fermi gases, which were obtained independently and are in good agreement with recent experimental results. Our focus is on the sequence and evolution of defects using the fermionic time-dependent Ginzburg-Landau equation, which contains dissipation necessary for equilibration. In contrast to other simulations, we introduce small, experimentally unavoidable symmetry breaking, particularly that associated with thermal fluctuations and with the phase-imprinting tilt angle, and we illustrate their dramatic effects. As appears consistent with experiment, the former causes vortex rings in confined geometries to move to the trap surface and rapidly decay into more stable vortex lines. The latter aligns the precessing and relatively long-lived vortex filaments, rendering them difficult to distinguish from solitons.

14.
Soc Sci Med ; 107: 162-70, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24607678

RESUMO

The objective of the study was to present socioeconomic and geographic inequalities in adolescent smoking in Scotland. The international literature suggests there is no obvious pattern in the geography of adolescent smoking, with rural areas having a higher prevalence than urban areas in some countries, and a lower prevalence in others. These differences are most likely due to substantive differences in rurality between countries in terms of their social, built and cultural geography. Previous studies in the UK have shown an association between lower socioeconomic status and smoking. The Scottish Health Behaviour in School-aged Children study surveyed 15 year olds in schools across Scotland between March and June of 2010. We ran multilevel logistic regressions using Markov chain Monte Carlo method and adjusting for age, school type, family affluence, area level deprivation and rurality. We imputed missing rurality and deprivation data using multivariate imputation by chained equations, and re-analysed the data (N = 3577), comparing findings. Among boys, smoking was associated only with area-level deprivation. This relationship appeared to have a quadratic S-shape, with those living in the second most deprived quintile having highest odds of smoking. Among girls, however, odds of smoking increased with deprivation at individual and area-level, with an approximate dose-response relationship for both. Odds of smoking were higher for girls living in remote and rural parts of Scotland than for those living in urban areas. Schools in rural areas were no more or less homogenous than schools in urban areas in terms of smoking prevalence. We discuss possible social and cultural explanations for the high prevalence of boys' and girls' smoking in low SES neighbourhoods and of girls' smoking in rural areas. We consider possible differences in the impact of recent tobacco policy changes, primary socialization, access and availability, retail outlet density and the home environment.


Assuntos
Comportamento do Adolescente/psicologia , Disparidades nos Níveis de Saúde , Áreas de Pobreza , Características de Residência/estatística & dados numéricos , População Rural/estatística & dados numéricos , Fumar/epidemiologia , População Urbana/estatística & dados numéricos , Adolescente , Estudos Transversais , Feminino , Humanos , Masculino , Análise Multinível , Fatores de Risco , Escócia/epidemiologia , Fatores Socioeconômicos
15.
J Clin Endocrinol Metab ; 99(4): 1420-4, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24432994

RESUMO

AIMS: Reduced glucose effectiveness is a predictor of future glucose tolerance in individuals with a family history of type 2 diabetes. We examined retrospectively at 10 years in normoglycemic relatives of diabetic subjects (RELs) the pathophysiological role of glucose effectiveness in the development of isolated impaired fasting glucose, glucose intolerance, and acute insulin release. METHODS: At 0 years, 19 RELs and 18 matched control subjects had glucose effectiveness (GE), insulin sensitivity, acute insulin release (AIR)IVGTT, and disposition index measured during an iv glucose tolerance test (IVGTT), using the minimal model analysis. At 0 and 10 years, oral glucose tolerance (OGTT) and AIROGTT were determined. RESULTS: At 0 years, fasting glucose (FG) and GE were raised in RELs, but insulin sensitivity and AIROGTT were reduced (P ≤ .05) compared with controls. At 10 years, RELs developed raised fasting and 2-hour OGTT glucose. FG10y correlated significantly with FG0y and body mass index0y and negatively with √GE and 2-hour OGTT glucose10y with FG0y and negatively with AIRIVGTT0y and AIROGTT0y. Log AIROGTT10y correlated with √GE, log AIRIVGTT0y and log AIROGTT0y. Multiple regression analyses demonstrated the following: REL FG10y was predicted by combined FG0y, √GE and body mass index0y (radj(2) = 56%; P ≤ .001) and 2-hour OGTT glucose10y weakly related by FG0y,and √GE (r(adj)(2) = 25%; P = .06). Log AIROGTT10y was predicted by AIRIVGTT0y and √GE (r(adj)(2) = 46%; P ≤ .004). CONCLUSION: In normoglycemic RELs, a relative reduction of glucose effectiveness is an important contributor over 10 years to the development of isolated impaired fasting glucose and reduced acute insulin secretion.


Assuntos
Glicemia/metabolismo , Diabetes Mellitus Tipo 2 , Intolerância à Glucose/epidemiologia , Células Secretoras de Insulina/fisiologia , Adulto , Estudos de Casos e Controles , Família , Feminino , Seguimentos , Intolerância à Glucose/metabolismo , Teste de Tolerância a Glucose , Humanos , Resistência à Insulina , Masculino , Estado Pré-Diabético/epidemiologia , Estado Pré-Diabético/metabolismo , Estudos Retrospectivos
17.
J Public Health (Oxf) ; 34(4): 523-31, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-22431257

RESUMO

BACKGROUND: Improving the diet of the Scottish population has been a government focus in recent years. Health promotion is known to be more effective in affluent groups. Alongside trends in eating behaviour, changes in socioeconomic inequalities must be monitored. METHODS: Eating behaviour data from the 2002, 2006 and 2010 Scotland Health Behaviour in School-Aged Children survey were modelled using multilevel linear modelling. RESULTS: Fruit and vegetable consumption increased between 2002 and 2010 by 0.26 and 0.27 days per week, respectively, while consumption of sweets, chips and crisps fell by 0.73, 1.25 and 0.99 days per week, respectively. An overall healthy eating score, calculated by summing food item weekly consumption, increased significantly (at 95% level of significance) over this period. Fruit and vegetable consumption was more frequent among children with high family affluence (individual measure of socioeconomic status), while consumption of crisps and chips was less frequent. When an interaction term was added between year and family affluence, this was not significant for any outcome. Variance at the education authority and school levels remained significant for all outcomes. CONCLUSIONS: Adolescent eating behaviours in Scotland have improved over time across the family affluence scale gradient as a whole, with persistent inequalities. Alongside population programmes, initiatives directed at more deprived groups are required.


Assuntos
Comportamento do Adolescente , Dieta/tendências , Comportamento Alimentar , Comportamentos Relacionados com a Saúde , Adolescente , Criança , Estudos Transversais , Dieta/estatística & dados numéricos , Inquéritos sobre Dietas , Gorduras na Dieta , Sacarose Alimentar , Características da Família , Feminino , Frutas , Humanos , Modelos Lineares , Masculino , Escócia , Fatores Socioeconômicos , Verduras
18.
Diabetologia ; 55(4): 1114-27, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22282162

RESUMO

AIMS/HYPOTHESIS: The molecular mechanisms underlying insulin resistance in skeletal muscle are incompletely understood. Here, we aimed to obtain a global picture of changes in protein abundance in skeletal muscle in obesity and type 2 diabetes, and those associated with whole-body measures of insulin action. METHODS: Skeletal muscle biopsies were obtained from ten healthy lean (LE), 11 obese non-diabetic (OB), and ten obese type 2 diabetic participants before and after hyperinsulinaemic-euglycaemic clamps. Quantitative proteome analysis was performed by two-dimensional differential-gel electrophoresis and tandem-mass-spectrometry-based protein identification. RESULTS: Forty-four protein spots displayed significant (p < 0.05) changes in abundance by at least a factor of 1.5 between groups. Several proteins were identified in multiple spots, suggesting post-translational modifications. Multiple spots containing glycolytic and fast-muscle proteins showed increased abundance, whereas spots with mitochondrial and slow-muscle proteins were downregulated in the OB and obese type 2 diabetic groups compared with the LE group. No differences in basal levels of myosin heavy chains were observed. The abundance of multiple spots representing glycolytic and fast-muscle proteins correlated negatively with insulin action on glucose disposal, glucose oxidation and lipid oxidation, while several spots with proteins involved in oxidative metabolism and mitochondrial function correlated positively with these whole-body measures of insulin action. CONCLUSIONS/INTERPRETATION: Our data suggest that increased glycolytic and decreased mitochondrial protein abundance together with a shift in muscle properties towards a fast-twitch pattern in the absence of marked changes in fibre-type distribution contribute to insulin resistance in obesity with and without type 2 diabetes. The roles of several differentially expressed or post-translationally modified proteins remain to be elucidated.


Assuntos
Diabetes Mellitus Tipo 2/metabolismo , Resistência à Insulina/fisiologia , Mitocôndrias/metabolismo , Músculo Esquelético/metabolismo , Obesidade/metabolismo , Feminino , Técnica Clamp de Glucose , Glicólise , Humanos , Insulina/metabolismo , Masculino , Pessoa de Meia-Idade , Proteômica , Espectrometria de Massas em Tandem
19.
Med Phys ; 39(6Part17): 3817, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28517472

RESUMO

PURPOSE: We hypothesize that PTV margin dose is an important factor for local tumor control. We evaluated dose distributions for patients originally treated with pencil-beam (PB)-based plans and retrospectively calculated with Monte Carlo (MC) method, with emphasis on the spatial region between the ITV and PTV (PTV-margin), where the largest dose differences were expected. METHODS: Forty-six stage I-II lung cancer patients with 51 lesions treated with SABR were retrospectively analyzed (23 central and 28 peripheral tumors). All patients received 4DCT imaging, and an ITV was generated from the maximum intensity projection and subsequent review of four 4DCT phases. An isotropic 3mm ITV-to-PTV margin was used. The iPlan TPS was used to generate the original treatment plans using PB-based heterogeneity correction. MC doses were recalculated using the same MUs as in the PB plan. Dose distributions for the ITV, PTV-margin, and PTV were analyzed using generalized equivalent uniform dose (gEUD) with a = - 20. Student's paired t-test elucidated differences between PB and MC-based gEUD and the two different tumor locations. RESULTS: Mean ITV and PTV volumes were 24.2 cc (range: 2.2 to 99.3 cc) and 50.4 cc (range: 6.4 to 229.7 cc), respectively. The mean gEUDs of ITV, PTV-margin and PTV, normalized to PB-based 100% isodose were 1.02+/-0.04, 1.01+/-0.04 and 1.01+/-0.04 for PB-based plans, compared to 0.94+/-0.06, 0.88+/-0.08 and 0.90+/-0.08 (all p<0.05) for MC-based plans. The maximum overestimations with the PB algorithm in the PTV-margin average dose were 10.4% and 19.6% (p < 0.05) for peripheral tumor cases and central tumor cases, respectively. CONCLUSIONS: PB-based dose distributions showed the highest dose overestimation (relative to MC) in the PTV-margin spatial region. Analysis of spatial dose differences is an important precursor toward assessment of patterns-of-local failure, to be investigated in future work to explore possible association between dose and regions of failure. Acknowledgement: supported in part by grants from NIH R01 CA106770 and from Varian Medical Systems.

20.
Med Phys ; 39(6Part6): 3666, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28517577

RESUMO

PURPOSE: To compare localization accuracies between an ExacTrac and cone beam computed tomography (CBCT) systems for single fraction spine adiosurgery. The work also aimed to evaluate the inherent systematic deviation of both ExacTrac and CBCT systems to achieve highly accurate localization in the spine radiosurgery. METHODS: ExacTrac and CBCT imaging systems were evaluated using the linac isocenter as the mutual reference point. First, a BB was placed in an anthropomorphic pelvic phantom. The phantom was localized with both imaging systems and the procedure was repeated 12 times. These results were used to devise a localization protocol using both imaging systems in spine radiosurgery, and employed for 51 patients (81 isocenters) prescribed for single fraction treatment. The displacement discrepancy between the isocenter and two systems were quantified in four dimensions (three translations, one rotation). A Student's two-tailed t-test was used to test for significant differences between the two imaging systems. RESULTS: The phantom study showed 1.4±0.5, 0.6±0.5, and 0.1±0.5 mm differences between the two imaging systems in the anterior/posterior (A/P), superior/inferior (S/I) and left/right (L/R) directions, respectively. The angular difference was minimal along all three axes. The patient study revealed similar isocenter discrepancies between ExacTrac and CBCT of 1.1 ± 0.7 mm, 1.0±0.9 mm, and 0.2±0.9 mm in the A/P, S/I, and L/R directions, respectively, with the A/P and S/I directions showing statistical significance ((t(80) = 13.5 and 7.6 respectively, p = 0.000). The couch yaw discrepancy was 0 ± 0.3°. Overall, 1 mm systematic differences were observed in the A/P and S/I directions between ExacTrac and CBCT localization systems, both in phantom and patient. A procedure was developed to mitigate this systematic discrepancy. CONCLUSIONS: These findings have justified our patient localization tolerance levels of 2 mm translation and 1 degree rotation for spine SRS treatment.

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