Introduction of external magnetic fields in entropic moment modelling for radiotherapy.

One of the big challenges of the emerging MRI-guided radiotherapy is the prediction of an external magnetic field effect on the deposited dose induced by a beam of charged particles. In this paper, we present the results of the implementation of the Lorentz force in the deterministic M1 model. The validation of our code is performed by comparisons with the Monte-Carlo code FLUKA. The relevant examples show a significant modification of the shape of dose deposition volume induced by the external magnetic field in presence of heterogeneities. A gamma-index analysis 3%/3mm shows a good agreement of our model with FLUKA simulations.

Deterministic model for the transport of energetic particles: Application in the electron radiotherapy.

A new deterministic method for calculating the dose distribution in the electron radiotherapy field is presented. The aim of this work was to validate our model by comparing it with the Monte Carlo simulation toolkit, GEANT4. A comparison of the longitudinal and transverse dose deposition profiles and electron distributions in homogeneous water phantoms showed a good accuracy of our model for electron transport, while reducing the calculation time by a factor of 50. Although the Bremsstrahlung effect is not yet implemented in our model, we propose here a method that solves the Boltzmann kinetic equation and provides a viable and efficient alternative to the expensive Monte Carlo modeling.

Effect of the plasma-generated magnetic field on relativistic electron transport.

In the fast-ignition scheme, relativistic electrons transport energy from the laser deposition zone to the dense part of the target where the fusion reactions can be ignited. The magnetic fields and electron collisions play an important role in the collimation or defocusing of this electron beam. Detailed description of these effects requires large-scale kinetic calculations and is limited to short time intervals. In this paper, a reduced kinetic model of fast electron transport coupled to the radiation hydrodynamic code is presented. It opens the possibility to carry on hybrid simulations in a time scale of tens of picoseconds or more. It is shown with this code that plasma-generated magnetic fields induced by noncollinear temperature and density gradients may strongly modify electron transport in a time scale of a few picoseconds. These fields tend to defocus the electron beam, reducing the coupling efficiency to the target. This effect, that was not seen before in shorter time simulations, has to be accounted for in any ignition design using electrons as a driver.

Analysis of return to competition and repeat rupture for 298 anterior cruciate ligament reconstructions with patellar or hamstring tendon autograft in sportspeople.

OBJECTIVES: To establish the influence of the type of surgical technique, competitive level, type of sport and the time before returning to competition on the reinjury rate after anterior cruciate ligament (ACL) surgery. METHODS: The authors followed-up 540 competitive sportspeople who had undergone ACL surgery via patellar or hamstring tendon autograft (HTA) techniques in 2003 and 2004. The sportspeople (all of whom had competed at a regional or higher level) were asked to fill out a questionnaire during their fourth postoperative year. RESULTS: The 298 respondees (reply rate: 55.1%) had the same characteristics as the initial (operated) population. The reinjury rates after HTA and patellar tendon autograft (PTA) were 12.7 and 6.1%, respectively. There was no statistically significant difference between these two values (P=0.14). Age and gender were not correlated with the frequency of reinjury. The reinjury rate rose slightly with increasing competitive level (regional level: 8.1%; national level: 10.4%; international level: 12.5%) but these differences were not statistically significant. Soccer had the highest reinjury rate (20.8%). Regardless of the surgical technique, sportspeople returning to competition within seven months of surgery had a greater risk of reinjury than those returning after this time point (15.3 versus 5.2%, P=0.014). The risk dropped from 13.9 to 2.6% (P=0.047) for PTA and from 16.6 to 7.6% (P=0.2) for HTA. Of the four reinjuries in sportspeople returning to competition with the first six months postoperative, three occurred within one month of resumption. CONCLUSION: Post-HTA reinjury rates are higher than post-PTA rates but the difference is not statistically significant. For sportspeople at a regional or higher level, the time interval before the return to competition has an influence on the risk of reinjury.

A deterministic partial differential equation model for dose calculation in electron radiotherapy.

High-energy ionizing radiation is a prominent modality for the treatment of many cancers. The approaches to electron dose calculation can be categorized into semi-empirical models (e.g. Fermi-Eyges, convolution-superposition) and probabilistic methods (e.g.Monte Carlo). A third approach to dose calculation has only recently attracted attention in the medical physics community. This approach is based on the deterministic kinetic equations of radiative transfer. We derive a macroscopic partial differential equation model for electron transport in tissue. This model involves an angular closure in the phase space. It is exact for the free streaming and the isotropic regime. We solve it numerically by a newly developed HLLC scheme based on Berthon et al (2007 J. Sci. Comput. 31 347-89) that exactly preserves the key properties of the analytical solution on the discrete level. We discuss several test cases taken from the medical physics literature. A test case with an academic Henyey-Greenstein scattering kernel is considered. We compare our model to a benchmark discrete ordinate solution. A simplified model of electron interactions with tissue is employed to compute the dose of an electron beam in a water phantom, and a case of irradiation of the vertebral column. Here our model is compared to the PENELOPE Monte Carlo code. In the academic example, the fluences computed with the new model and a benchmark result differ by less than 1%. The depths at half maximum differ by less than 0.6%. In the two comparisons with Monte Carlo, our model gives qualitatively reasonable dose distributions. Due to the crude interaction model, these so far do not have the accuracy needed in clinical practice. However, the new model has a computational cost that is less than one-tenth of the cost of a Monte Carlo simulation. In addition, simulations can be set up in a similar way as a Monte Carlo simulation. If more detailed effects such as coupled electron-photon transport, bremsstrahlung, Compton scattering and the production of delta electrons are added to our model, the computation time will only slightly increase. Its margin of error, on the other hand, will decrease and should be within a few per cent of the actual dose. Therefore, the new model has the potential to become useful for dose calculations in clinical practice.

Short- and long-term risk factors for sudden death in patients with stable angina.

Sudden death is most common and often the first manifestation of coronary heart disease although its risk is difficult to predict. It has been studied mainly in patients with severe ventricular arrhythmia or recent myocardial infarction, but little is known about the different risk factors for short- and long-term risk of sudden death in patients with stable angina. To assess risk factors for sudden death in patients with stable angina and angiographically proven coronary artery disease, 319 consecutive patients were recruited prospectively and followed-up. Patients with clinical heart failure or recent myocardial infarction were excluded. Clinical, angiographic and biological variables were recorded. The association between each variable and the risk of sudden death was assessed in univariate and logistic multivariate analysis. There were 25 sudden deaths during the follow-up period (97+/-29 months). The univariate predictors in the short-term (2 years) were: peripheral arterial disease, left ventricular hypertrophy, low density lipoprotein cholesterol and ejection fraction. The independent predictors were: peripheral arterial disease (relative risk: 6.3), ejection fraction (relative risk 1.05) and low density lipoprotein (relative risk: 1.8). In the long-term (8-10 years), body mass index, coronary score, ejection fraction and fibrinogen were univariate predictors. Only body mass index (relative risk: 1. 2), ejection fraction (relative risk: 1.06) and fibrinogen (relative risk: 2) remained independent predictors. The risk factors for sudden death in stable angina were time-dependent, peripheral arterial disease appeared as the best predictor with LDL for short time, and body mass index (obesity: index >27) and fibrinogen for long time. Ejection fraction was the only time-independent predictor.

Detection of coronary stenoses by stress echocardiography using a previously implanted pacemaker for ventricular pacing: preliminary report of a new method.

BACKGROUND: The number of patients with pacemakers has been increasing and a large number of them will present with chest pain or symptoms suggesting angina pectoris. Myocardial ischemia and presence of coronary artery disease are difficult to detect and assess by noninvasive methods in patients with a pacemaker; the electrocardiogram (ECG) at rest and during exercise is usually very difficult to analyze in terms of ischemia or even presence of an acute myocardial infarction. HYPOTHESIS: To detect significant coronary stenosis in patients with previously implanted pacemakers, we tested a new stress echocardiography method using incremental ventricular pacing by already implanted pacemakers. METHODS: We studied prospectively 25 consecutive patients who underwent stress echocardiography with increasing ventricular pacing up to either 85% of the age-predicted maximal heart rate or chest pain. Positive tests were defined by new hypokinesia or worsening of a preexisting alteration in wall motion in at least two adjacent territories. All patients underwent coronary angiograms to define the presence and severity of coronary stenoses. RESULTS: Among the 25 tests, 11 (44%) were stopped for chest pain. 1 (4%) for moderate discomfort, 1 (4%) for a drop in blood pressure, and the target pacing rate was achieved in the tests of the remaining 12 patients (48%). There were no complications. Thirteen patients had significant stenoses. In 10 cases, stress echocardiography was a true positive test with respect to coronary angiography. There were 11 true negative, 1 false positive, and 3 false negative tests. The sensitivity was 77%, specificity was 90%, the positive predictive value was 91%, and the negative predictive value 79%. The accuracy was 84%. CONCLUSIONS: This new stress echocardiography method appears feasible, easy, safe, and effective for detection of significant coronary stenoses in patients with pacemakers.

Incidence and predictors of drug-treated diabetes in elderly French subjects. The PAQUID Epidemiological Survey.

AIMS: To estimate the incidence and predictors of drug-treated diabetes in elderly subjects. METHODS: The PAQUID epidemiological survey, a population-based study, has followed up 3,777 subjects older than 65 years since 1988. At each visit (baseline, 1, 3, 5 and 8 years), treatment regimen was used to identify new drug-treated diabetic subjects. Potential predictors of drug-treated diabetes were collected during the baseline visit (body mass index (BMI), educational level, cigarette smoking and wine consumption, physical activity, depressive symptomatology, subjective health, treatment, and hypertension) and analysed by using a multivariate backward stepwise regression Cox model with delayed entry. RESULTS: The prevalence rate of drug-treated diabetes was 7.5% at baseline and 7.1% after 8 years' follow-up. The incidence rate of drug-treated diabetes was 3.8/1,000 person-years, 5.9/1,000 person-years in men and 2.4/1,000 person-years in women, with no significant variation according to age group. Male sex (relative risk (RR) 2.4, 95% confidence interval (CI) 1.4-4.0, P < 0.001, attributable risk (AR) 0.36), elevated BMI (for one point increase, RR 1.1, 95% CI 1.1-1.1, P < 0.001, > or = 25 vs. < 25, RR 2.1, 95% CI 1.2-3.5, AR 0.33), thiazide diuretics used alone (RR 5.9, 95% CI 1.8-19.6, P = 0.02), and poorer subjective health ('the same' vs. 'better' RR 1.8, 95% CI 1.0-3.1, P = 0.04; 'worse' vs. 'better' RR 2.3, 95% CI 0.9-5.7, P = 0.06) were independent predictors of drug-treated diabetes in this population. CONCLUSIONS: In older French individuals, men seem to be particularly exposed to drug-treated diabetes although being overweight was found to be a strong predictor as in younger populations.

Relationships between cholesterol, apolipoprotein E polymorphism and dementia: a cross-sectional analysis from the PAQUID study.

This study assesses the cross-sectional relationship between serum cholesterol level and dementia, controlling for apolipoprotein E (apoE) genotype, in a nested case-control study of 334 elderly French subjects aged 73 and over who participated in the PAQUID study (37 demented subjects and 297 nondemented controls). A diagnosis of dementia was established by two-step screening: (1) psychometric testing and DSM-III-R criteria and (2) neurologist's confirmation. Cholesterol, its fractions and apoE genotype were determined from a blood sample. Elevated high-density lipoprotein cholesterol was associated with a significantly decreased risk of dementia, independent of apoE status and other potential confounding variables, suggesting that cholesterol fractions could be involved in both Alzheimer's disease and vascular dementia.

Five-year mortality in elderly French subjects from the PAQUID epidemiologival survey: the burden of diabetes.

We describe the 5-year mortality and its risk factors in a cohort of elderly people with and without known diabetes mellitus. The PAQUID cohort was representative of the population older than 65 living in Gironde, south-west France. Potential mortality risk factors were collected during a baseline evaluation, using a health questionnaire, from 68.9% of a randomly selected sample of over-65s in 1988. A total of 237 subjects (8.5%) had diabetes. Annual review occurred for 5 years and cause of any death was ascertained from family doctors. After 5 years, 623 people (22.3%) had died, of whom 576 were non-demented; 30.0% of the diabetic group versus 20.3% of the non-diabetic group had died. Survival of the known diabetic group was lower than that of the non-diabetic group (p < 0.001), although this excess mortality was significant only in the 65 to 75 age range (relative risk 1.8; 95% confidence interval 1.2 to 2.8, p = 0.04). Cardiovascular mortality rate did not differ between the diabetic and non-diabetic groups (RR 1.2 [0.8-2.0]). Death related to neoplasia was significantly higher in the known diabetic group (RR 2.2 [1.2-3.3], p = 0.01). In the final model, integrating diabetes as a mortality risk factor in the total cohort, known diabetes at the baseline examination was an independent risk factor for mortality (RR 1.4 [1.0-1.8], p = 0.01), in addition to tobacco use, hypertension and functional dependency. These results confirm suggestions that diabetes increases mortality in the over-65 age group, perhaps with an adverse interaction with other pathology.

Comparative view of the socioeconomic impact of migraine versus low back pain.

The burden of migraine in terms of cost and impact on socioeconomic indicators is still controversial. In a recent comparative study between migraineurs and controls from the French general population, we show that only general practitioner (GP) consultations and complementary examinations are more frequent in migraineurs. In this paper, we compare the socioeconomic impact of migraine versus another common neurological disease, low back pain, which has similar consequences in term of deficiencies, disabilities, and handicaps. Our study is a subproject of the Gazel cohort study, conducted on 20,000 volunteers working in the "Electricité et Gaz de France" company. The socioeconomic impact was evaluated prospectively by the number of workdays missed between 1989 and 1992 in 436 subjects with migraine but without low back pain (M group), 590 subjects with low back pain but without migraine (L group), 555 subjects with migraine and low back pain (ML group), and in 1005 subjects without headache or low back pain (C group). Moreover, in 1993 all subjects completed a mailed questionnaire on their 6-months' history of use of medical services. The number of workdays missed during this 4-year period was statistically greater in the ML group (58.1 days), followed by the L group (38.4 days), the C group (35.1 days), and the M group (31.8 days) (p = 0.0001). For the use of medical services, the results were different according to the different indicators: GP consultations were more frequent in the ML and M groups, specialist consultations and complementary examinations in the L and C groups. In conclusion, migraine and low back pain seem to have a similar socioeconomic impact. Absenteeism is particularly high when both neurological disorders are present.

Dependency in Parkinson's disease: a population-based survey in nondemented elderly subjects.

Little epidemiological data are available on the dependency status of elderly patients with Parkinson's disease (PD) living in the community. This study assessed the activities of daily living (ADL), the instrumental activities of daily living (IADL), and mobility in a representative sample of elderly nondemented PD subjects (n = 20), compared to a control population (n = 2,697). We found a significantly higher level of dependency in the PD sample based on ADL, IADL, and mobility scales. Half of the PD subjects were dependent for ADL (versus 13.2% for controls), 80% were dependent for IADL (versus 28% for controls), and 20% had their mobility restricted to their home (versus 1.5% for controls). The proportion of PD patients tended to be higher in those more depressed or with more severe motor symptoms. PD patients were not found to be more isolated socially or from family than was the control group and, in any case, dependency seemed not to be associated with isolation. When adjusting for age, sex, depressive symptoms, Mini Mental Status examination score, and dyspnea, PD remained significantly associated with dependency. PD thus constitutes a significant factor of dependency in elderly subjects living at home. Institutionalization occurred over four times more frequently in the PD group than in the general population, but no specific factor of institutionalization was noted.

Restenosis or rapid progression in non-dilated sites are not predictors of late spontaneous coronary events.

The present study was designed to assess the prognostic value of clinical and angiographic factors, and especially restenosis or rapid progression in non-dilated sites, on major spontaneous coronary events at long-term follow-up after a first successful coronary angioplasty performed for angina pectoris. A second aim was to assess the prognostic factors and especially restenosis in asymptomatic patients after angioplasty. The first 352 consecutive patients undergoing a successful coronary angioplasty were selected and followed-up. The following variables: age, sex, unstable angina, previous myocardial infarction, diabetes, hypercholesterolemia, tobacco consumption, hypertension, fibrinogen, coronary extent, single or multiple dilatation, restenosis, new progression, clinical deterioration of anginal status just before angiographic restudy or asymptomatic status were subjected to a stepwise regression analysis. Restenosis (a loss of 30% in diameter and/or a return to a >50% stenosis) and progression in non-dilated segments (a 20% reduction in diameter) were assessed by a computer-assisted method. Cardiac death, new myocardial infarction or new unstable angina, at long-term follow-up after angiographic restudy, were regarded as spontaneous coronary events and pooled in a single dependent variable. Thus 41 patients had a coronary event. In the overall population, clinical deterioration of anginal status (p<0.001, relative risk: 3.65) and fibrinogen (p<0.05, relative risk: 1.03) were independent predictors of spontaneous coronary events. Restenosis or new progression were not predictors. In asymptomatic patients (n=187), fibrinogen (p<0.01, relative risk=1.06) was the only predictor and restenosis was not an independent predictor of spontaneous coronary events. The best predictor of spontaneous coronary events at long-term follow-up after a first successful coronary angioplasty is clinical deterioration in anginal status in the months following the procedure. Restenosis does not appear as an independent predictor. Rapid progression observed in non-dilated sites is not an important prognostic factor.

Prevalence of diabetes and effect on quality of life in older French living in the community: the PAQUID Epidemiological Survey.

OBJECTIVES: To evaluate the prevalence of diabetes mellitus in older French subjects and to examine the different aspects of quality of life in an older diabetic population. DESIGN: From a random sample of 2792 people older than age 65 living in the community, a diabetic sample was selected using three items from a questionnaire: Are you diabetic? Are you on a diabetic diet? What kind of medications do you take daily? Validation of the questionnaire was carried out previously to correct the observed prevalence. MEASUREMENTS: The questionnaire assessed social and demographic aspects, physical, mental, and subjective health, and functional disabilities. Because quality of life assessment was mainly subjective, demented subjects were excluded. RESULTS: The diabetic group consisted of 237 subjects from the older sample of 2792 (8.5%). No age difference was demonstrated between the two groups (mean, distribution), but the male/female ratio was significantly higher in those with diabetes (49.4% vs 39.3%, P = .003). Corrected prevalence of diabetes was 10.3%. After exclusion of demented subjects, 230/2726 people were investigated. Diabetic subjects were heavier (P < .001), had higher systolic blood pressure (P < .001), and had more frequent symptoms of ischemic heart disease (P < .001) and painful peripheral arterial disease (P < .001) and dyspnea (P < .001), but antecedents of stroke were similar in both groups. Diabetics were more often lacking in autonomy according to the IADL Lawton scale (P < .001), Rosow and Breslow scale (P < .001), and Mobility scale (P = .043), but not according to the Katz ADL scale. They more often exhibited symptoms of depression on the CES-D self-rating scale (21.3% vs 12.7%, P < .001), but evaluation of cognitive function was similar in both groups. Thirteen percent of diabetics, compared with 7.6% of non-diabetics, were unsatisfied with their own situation (P = .002). Health was rated as fair, bad, or very bad by 67.8% of diabetics compared with 49% of non-diabetics (P < .001). Diabetics rated themselves as feeling worse than others (15.3% vs 9.2%, P < < .001) and worried more about their health status (78% vs 63%, P < < .001). CONCLUSION: The observed prevalence of diabetes in older French people living in the community was 8.5%. Quality of life in older diabetics was poorer than that of other people of the same age.

Frequency of severe attacks in migraine sufferers of the Gazel cohort.

The concept of severe migraine was raised to define migraineurs most in need of care and for use in clinical practice. We aimed to measure the frequency of severe attacks in a working sample of 276 migraine sufferers using a diary over a 3-month period. Migraine sufferers recorded each attack's clinical features, the degree of their disability, their use of drugs and the effectiveness of the drugs. Since the definition of severe attack is not standardized, we studied the impact of different definitions on the frequency. The frequency of severe attacks was 0.9% and appeared to be very sensitive to the definitions, ranging between 0.4 and 13%. In France, the extrapolated number of severe attacks is nearly one million out of a total of 115 million. In the migraineurs who had had at least one severe attack, the individual variability of intensity, duration or disability was very high, so the proportion of severe attacks in a given sufferer was low--between 15% and 50%. We conclude that the global concept of severe migraine is not relevant and should be split into two components--severe attack and severe migraine sufferer. The goals are different, too. Regarding treatment, for example, the severe attack concept is more valid for acute treatment strategies, whereas the severe migraine sufferer concept should be preferred to determine the need for prophylactic treatment. Since much work is being done nowadays to define acute treatment strategies, definition of the criteria of severe attack and validation of a measurement tool should be a priority.