Uncertainties in individual doses in a case-control study of thyroid cancer after the Chernobyl accident

Individual radiation doses to the thyroid were reconstructed for 2239 subjects of a case-control study of thyroid cancer among young people that was carried out in regions of Belarus and Russia contaminated by radioactive fallout from the Chernobyl accident. Although the process of dose reconstruction provides a point estimate of each subject's dose, it is obvious that there is uncertainty associated with these dose calculations. The following main sources of uncertainty in the estimated individual doses were identified: (1) shared and unshared errors associated with parameters of the dosimetry model; and (2) unshared errors that are associated with the variability, reliability and ability of information from the personal interviews. Besides setting up proper distributions for the parameters of the dosimetry model, inter-individual correlations were also defined to take into account shared errors. By the application of Monte Carlo simulations, a set of approximately log-normally distributed thyroid doses was obtained for each subject; the geometric standard deviations of the distributions are found to vary among individuals from 1.7 to 3.7.     

Diseases, consumption of medicines and responsibility for a road crash: a case-control study

The role of medical conditions in crashes is a topic of public debate. Some studies suggest that there has been a reduction in road traffic crashes subsequent to the medical restrictions introduced on drivers with medical deficiencies. As in today's society the car is an important factor for independence and socialization, it seems important to consider whether diseases or consumption of drugs increase the risk of causing a road crash in comparison to well-known major crash risk factors. A case-control study was conducted (733 injured drivers). The cases were subjects who were partly or totally responsible for their crash. The 304 controls were the non-responsible drivers. Diseases and medicine consumption were analyzed using logistic regression models. Cases were characterized by a higher percentage of young men. They were more frequently affected by fatigue, as were subjects who had consumed alcohol. A higher risk in subjects suffering from hypertension is observed (adjusted odds ratio [adjOR]=3.82; 95%CI=[1.42-10.24]). An association between antidepressant consumption and responsibility appeared (adjOR=3.61; 95%CI=[1.30-10.03]). CONCLUSION: Medical factors associated with responsibility were arterial hypertension and antidepressant consumption. Other medical conditions do not seem to play a preponderant role comparing to individual behaviours.     

Radiation-epidemiological studies of thyroid cancer incidence in Russia after the Chernobyl accident (estimation of radiation risks, 1991-2008 follow-up period)

This study presents an analysis of the thyroid cancer incidence in the population of the most contaminated territories of Bryansk, Kaluga, Oryol and Tula oblasts affected by the Chernobyl accident. The follow-up period is 1991-2008, and the cohort size is 309 130 people. For that period 978 thyroid cancer cases were detected. The excess relative risk per 1 Gy (ERR/Gy) is found to be statistically significant for children and adolescents (0-17 y of age) at the time of the Chernobyl accident (ERR/Gy=3.22; 95 % confidence interval (1.56; 5.81). In boys, the ERR/Gy was higher than in girls -6.54 and 2.24, respectively. A statistically significant decrease in ERR/Gy with time since exposure, by a factor of 0.37 per 10 y, was observed for the whole cohort and for boys separately, but not for girls. No radiation risks of a thyroid cancer among people of 18 y of age at exposure and older were found.     

Alcohol, psychoactive drugs and fatal road traffic accidents in Norway: a case-control study

A case–control study was conducted on 204 drivers fatally injured in road traffic accidents in south-eastern Norway during the period 2003–2008. Cases from single vehicle accidents (N = 68) were assessed separately. As controls, 10 540 drivers selected in a roadside survey in the same geographical area during 2005–2006 were used. Blood samples were collected from the cases and oral fluid (saliva) samples from the controls. Samples were analysed for alcohol, amphetamines, cannabis, cocaine, opioid analgesics, hypnotics, sedatives and a muscle relaxant; altogether 22 psychoactive substances. Equivalent cutoff concentrations for blood and oral fluid were used. The risk for fatal injury in a road traffic accident was estimated using logistic regression adjusting for gender, age, season of the year, and time of the week. The odds for involvement in fatal road traffic accidents for different substances or combination of substances were in increasing order: single drug < multiple drugs < alcohol only < alcohol + drugs. For single substance use: medicinal drug or THC < amphetamine/methamphetamine < alcohol. For most substances, higher ORs were found when studying drivers involved in single vehicle accidents than for those involved in multiple vehicle accidents, but confidence intervals were wider.     

Antilock brakes and the risk of driver injury in a crash: a case-control study

While antilock brakes can improve steering and reduce stopping distance in some test situations, there is little evidence that they reduce the risk of crash-related injury. We sought to estimate the association between presence of antilock brakes and the risk of driver injury. We conducted a case-control study using claims data from the Insurance Corporation of British Columbia, Canada, for passenger vehicles insured during July 1, 2003, to June 30, 2004. Cases were 5000 vehicles with a driver crash injury during the study period. Controls were 49,994 vehicles insured at the mid-point of the study interval. The adjusted risk ratio for a crash with driver injury in a vehicle with antilock brakes was 1.06 (95% confidence interval, 0.95-1.17), compared with a vehicle without antilock brakes. If this estimated association is causal, antilock brakes do not prevent crash-related driver injuries.     

Uncertainties in internal doses calculated for Mayak workers--a study of 63 cases

This study makes use of 63 cases of Mayak workers exposed to Pu-239 with autopsy data and some late-time urine bioassay data. In addition, air-concentration data--used to construct monthly average values--are available for each case, which provide the time dependence and potential magnitudes of normal inhalation intakes for each case. The purpose of the study is to develop and test Bayesian methods of dose calculation for the Mayak workers. The first part of the study was to quantitatively characterise the uncertainties of the bioassay data. Then, starting with three different published biokinetic models, the data are fit by varying intake and model perturbation parameters, e.g., parameters influencing the lung, thoracic lymph nodes, liver and bone retention. Statistical self-consistency arguments are used to check the measurement uncertainty parameters within the Poisson-lognormal model. The second part of the study is to set up and test Bayesian dose calculations, which use the point determinations of biokinetic parameters from the study cases within a discrete, empirical Bayes approximation. The main conclusion of the study is that these methods are now ready to be applied to the entire Mayak worker population.     

Impact of free light chain hemodialysis in myeloma cast nephropathy: a case-control study

New very high permeability dialysis membranes have been developed to enable the clearance of free light chains in myeloma cast nephropathy. These new dialysis techniques, in combination with chemotherapy, should allow improved prognosis in patients with myeloma cast nephropathy. We report a prospective observational study comparing patients who underwent hemodialysis in our center in 2009 for cast nephropathy revealing multiple myeloma vs. patients treated for the same condition during the same period in other centers in our region. The main difference in the management protocols was the use of high cutoff (HCO) membranes in our center. We described the clinical features, the management protocols, and the outcomes as of June 1, 2010. In 2009, five patients were treated for myeloma cast nephropathy with HCO hemodialysis in our center. At 386 ± 100 days follow‐up, one patient died, while three of the five patients recovered their renal function, allowing cessation of hemodialysis. During the same period, five patients were treated for myeloma cast nephropathy in other centers in our region. At 398 ± 131 days follow‐up, four patients died, and none of the patients recovered renal function, allowing cessation of hemodialysis. In our study, light chain clearance allowed recovery of renal function and cessation of hemodialysis in three of five patients with acute kidney injury secondary to myeloma cast nephropathy. A randomized trial comparing this technique with conventional hemodialysis techniques should be conducted to raise the level of proof for this therapeutic option. The overall prognosis, including quality of life and cost‐effectiveness, of HCO hemodialysis should also be examined.     

Data analysis from a multi-centre, comparative study of angiographic examinations leading to practical guidelines for the optimisation of patient doses

In this study, patient doses were analysed against exposure parameters and procedure protocol. Patient doses were measured in seven hospitals for a standard diagnostic vascular examination. Image quality was assessed using the contrast-detail phantom from Nijmegen (CD-DISC 2.0). A link between dose and image quality was investigated. Image quality strongly depends on the preset dose level. The higher the dose level, the better the image quality, but also the higher the patient dose. However, no clear correlation was found between total dose-area product (DAP) or effective dose and image quality. A large range in patient dose was found: DAP (22-130 Gy cm2) and effective dose (3.9-16.8 mSv). A difference in number of frames was also found in the different centres, owing to different frame rates (3-2-1 frames per second) and use of oblique projections. Differences in doses and exposure settings offer the possibility of optimising patient doses in angiography and interventional radiology.     

Plasmon spectroscopy and imaging of individual gold nanodecahedra: a combined optical microscopy, cathodoluminescence, and electron energy-loss spectroscopy study

Imaging localized plasmon modes in noble-metal nanoparticles is of fundamental importance for applications such as ultrasensitive molecular detection. Here, we demonstrate the combined use of optical dark-field microscopy (DFM), cathodoluminescence (CL), and electron energy-loss spectroscopy (EELS) to study localized surface plasmons on individual gold nanodecahedra. By exciting surface plasmons with either external light or an electron beam, we experimentally resolve a prominent dipole-active plasmon band in the far-field radiation acquired via DFM and CL, whereas EELS reveals an additional plasmon mode associated with a weak dipole moment. We present measured spectra and intensity maps of plasmon modes in individual nanodecahedra in excellent agreement with boundary-element method simulations, including the effect of the substrate. A simple tight-binding model is formulated to successfully explain the rich plasmon structure in these particles encompasing bright and dark modes, which we predict to be fully observable in less lossy silver decahedra. Our work provides useful insight into the complex nature of plasmon resonances in nanoparticles with pentagonal symmetry.     

Bioaccumulation of Tc,Pu, and Np on Bottom Sediments in Two Types of Freshwater Lakes of the Moscow Oblast

A laboratory study is made of Tc, Np, and Pu accumulation by natural and sterilized silts collected from two typical eutrophic and dystrophic lakes of the Moscow oblast. After a short inductive period (1-3 days), the rate of Tc uptake by the eutrophic lake silt is about twice that by the dystrophic lake silt (at a dry solid to liquid phase ratio of 0.033 g ml^{- 1}). The rate is only slightly temperature-dependent, being practically constant (at a level of about 3% per day) under certain conditions. The distribution coefficients after a month of contact were found to be 1700±50 and 56±5 ml g^{- 1} for the eutrophic and dystrophic lake silts, respectively. Sulfate and nitrate have an inhibiting effect on the Tc uptake. Efficient desorption of Tc from bottom sediments can be realized only in the presence of an oxidant (H₂O₂), suggesting the reductive mechanism of Tc sorption on silts, complicated by either complexation with microorganism cell components or by intracellular deposition.     

ERIDAS, a computer program for rapid calculation of internal doses from measurements of people in an emergency

In an emergency involving the deliberate or accidental release of radioactive materials, there could potentially be a large number of people who require monitoring for internal contamination. Doses from these measurements will need to be calculated as quickly as possible. Emergency Response Internal Dose Assessment Software (ERIDAS) has been designed for this purpose.     

Two-Stage Plans for Estimating the Inverse of a Monotone Function

This study investigates two-stage plans based on nonparametric procedures for estimating an inverse regression function at a given point. Specifically, isotonic regression is used at stage one to obtain an initial estimate followed by another round of isotonic regression in the vicinity of this estimate at stage two. It is shown that such two-stage plans accelerate the convergence rate of one-stage procedures and are superior to existing two-stage procedures that use local parametric approximations at stage two when the available budget is moderate and/or the regression function is “ill-behaved.” Both Wald- and likelihood ratio-type confidence intervals for the threshold value of interest are investigated and the latter are recommended in applications due to their simplicity and robustness. The developed plans are illustrated through a comprehensive simulation study and an application to car fuel efficiency data.     

Analysis of bibliometric indicators for individual scholars in a large data set

Citation numbers and other quantities derived from bibliographic databases are becoming standard tools for the assessment of productivity and impact of research activities. Though widely used, still their statistical properties have not been well established so far. This is especially true in the case of bibliometric indicators aimed at the evaluation of individual scholars, because large-scale data sets are typically difficult to be retrieved. Here, we take advantage of a recently introduced large bibliographic data set, Google Scholar Citations, which collects the entire publication record of individual scholars. We analyze the scientific profile of more than 30,000 researchers, and study the relation between the h-index, the number of publications and the number of citations of individual scientists. While the number of publications of a scientist has a rather weak relation with his/her h-index, we find that the h-index of a scientist is strongly correlated with the number of citations that she/he has received so that the number of citations can be effectively be used as a proxy of the h-index. Allowing for the h-index to depend on both the number of citations and the number of publications, we find only a minor improvement.     

Comparison of different dosimetric methods for red marrow absorbed dose calculation in thyroid cancer therapy

Several dosimetric methods have been proposed for estimating red marrow absorbed dose (RMAD) when radionuclide therapy is planned for differentiated thyroid cancer, although to date, there is no consensus as to whether dose calculation should be based on blood-activity concentration or not. Our purpose was to compare RMADs derived from methods that require collecting patients' blood samples versus those involving OLINDA/EXM software, thereby precluding this invasive procedure. This is a retrospective study that included 34 patients under treatment for metastatic thyroid disease. A deviation of <10 % between RMADs was found, when comparing the doses from the most usual invasive dosimetric methods and those from OLINDA/EXM. No statistical difference between the methods was discovered, whereby the need for invasive procedures when calculating the dose is questioned. The use of OLINDA/EXM in clinical routine could possibly diminish data collection, thus giving rise to a simultaneous reduction in time and clinical costs, besides avoiding any kind of discomfort on the part of the patients involved.     

A comparative study of phase II robust multivariate control charts for individual observations

Use of Hotelling's T² charts with high breakdown robust estimates to monitor multivariate individual observations are the recent trend in the control chart methodology. Vargas (J. Qual. Tech. 2003; 35: 367‐376) introduced Hotelling's T² charts based on the minimum volume ellipsoid (MVE) and the minimum covariance determinant (MCD) estimates to identify outliers in Phase I data. Studies carried out by Jensen et al. (Qual. Rel. Eng. Int. 2007; 23: 615‐629) indicated that the performance of these charts heavily depends on the sample size, amount of outliers and the dimensionality of the Phase I data. Chenouri et al. (J. Qual. Tech. 2009; 41: 259‐271) recently proposed robust Hotelling's T² control charts for monitoring Phase II data based on the reweighted MCD (RMCD) estimates of the mean vector and covariance matrix from Phase I. They showed that Phase II RMCD charts have better performance compared with Phase II standard Hotelling's T² charts based on outlier free Phase I data, where the outlier free Phase I data were obtained by applying MCD and MVE T² charts to historical data. Reweighted MVE (RMVE) and S‐estimators are two competitors of the RMCD estimators and it is a natural question whether the performance of Phase II Hotelling's T² charts with RMCD and RMVE estimates exhibits similar pattern observed by Jensen et al. (Qual. Rel. Eng. Int. 2007; 23: 615‐629) in the case of MCD and MVE‐based Phase I Hotelling's T² charts. In this paper, we conduct a comparative study to assess the performance of Hotelling's T² charts with RMCD, RMVE and S‐estimators using large number of Monte Carlo simulations by considering different data scenarios. Our results are generally in favor of the RMCD‐based charts irrespective of sample size, outliers and dimensionality of Phase I data. Copyright © 2010 John Wiley & Sons, Ltd.     

Scattered doses to different parts of cancer patients during radiotherapy treatment in Nigeria

The doses over various parts of the body of 7 patients with cancers of the pharynx, breast and cervix during radiotherapy treatment with a megavoltage 60Co therapy machine were measured using LiF TL dosemeters. The doses on the surface of the patients outside the primary beam were found to vary with a maximum of 366 mGy at the abdomen of a cervix cancer patient to a minimum value of 1.1 mGy at the left arm and left leg of a pharynx cancer patient. The observed variations in the doses were attributed to the difference in patients' tumour location, exposure and anatomy. In the treatment of pregnant women and women of childbearing age, the results presented will be a good starting point for estimation of fetus doses and doses to organs outside the planning region.     

Effects of secondary amyloidosis on arteriovenous hemodialysis fistula outcomes and intradialytic hypotension: a case-control study

Amyloid fibrils can affect vascular structure through deposition and by causing nitric oxide depletion and increase of asymmetric dimethyl arginine. Patients with amyloidosis are prone to development of hypotension. Hypotension may also affect the maturation of arteriovenous fistula (AVF) and may set the stage for formation of thrombosis and fistula failure. Thus, we aimed to evaluate effects of secondary amyloidosis on AVF outcomes and intradialytic hypotension. This is a case‐control study which included 20 hemodialysis patients with amyloidosis and 20 hemodialysis patients without amyloidosis as control group. All patients underwent Doppler ultrasound of AVF. A thorough fistula history and baseline laboratory values along with episodes of intradialytic hypotension and blood pressure measurements were recorded. There was no difference between the groups regarding age, gender, body mass index, presence of comorbidities, hypertension, and drug use. Systolic and diastolic blood pressures were similar (119 ± 28/75 ± 17 and 120 ± 14/75 ± 10 mmHg for patients with and without amyloidosis, respectively). Intradialytic hypotension episodes were also similar. Patients with amyloidosis had significantly lower serum albumin and higher C‐reactive protein values compared to control hemodialysis patients. AVF sites and total number of created fistulas were similar in both groups. Flow rates of current functional AVFs were not different between the groups (1084 ± 875 and 845 ± 466 mL/minute for patients with and without amyloidosis, respectively, p:0.67). Patency duration of first AVF was not different between the groups. Clinical fistula outcomes and rate of intradialytic hypotension episodes were not significantly different between patients with and without secondary systemic amyloidosis.