Assessment of statistical iterative reconstructions to optimize CT examination protocols for children and young adults

La tomodensitométrie (CT) est une technique d'imagerie dont l'intérêt n'a cessé de croître depuis son apparition dans le début des années 70. Dans le domaine médical, son utilisation est incontournable à tel point que ce système d'imagerie pourrait être amené à devenir victime de son succès si son impact au niveau de l'exposition de la population ne fait pas l'objet d'une attention particulière. Bien évidemment, l'augmentation du nombre d'examens CT a permis d'améliorer la prise en charge des patients ou a rendu certaines procédures moins invasives. Toutefois, pour assurer que le compromis risque - bénéfice soit toujours en faveur du patient, il est nécessaire d'éviter de délivrer des doses non utiles au diagnostic.¦Si cette action est importante chez l'adulte elle doit être une priorité lorsque les examens se font chez l'enfant, en particulier lorsque l'on suit des pathologies qui nécessitent plusieurs examens CT au cours de la vie du patient. En effet, les enfants et jeunes adultes sont plus radiosensibles. De plus, leur espérance de vie étant supérieure à celle de l'adulte, ils présentent un risque accru de développer un cancer radio-induit dont la phase de latence peut être supérieure à vingt ans. Partant du principe que chaque examen radiologique est justifié, il devient dès lors nécessaire d'optimiser les protocoles d'acquisitions pour s'assurer que le patient ne soit pas irradié inutilement. L'avancée technologique au niveau du CT est très rapide et depuis 2009, de nouvelles techniques de reconstructions d'images, dites itératives, ont été introduites afin de réduire la dose et améliorer la qualité d'image.¦Le présent travail a pour objectif de déterminer le potentiel des reconstructions itératives statistiques pour réduire au minimum les doses délivrées lors d'examens CT chez l'enfant et le jeune adulte tout en conservant une qualité d'image permettant le diagnostic, ceci afin de proposer des protocoles optimisés.¦L'optimisation d'un protocole d'examen CT nécessite de pouvoir évaluer la dose délivrée et la qualité d'image utile au diagnostic. Alors que la dose est estimée au moyen d'indices CT (CTDIV0| et DLP), ce travail a la particularité d'utiliser deux approches radicalement différentes pour évaluer la qualité d'image. La première approche dite « physique », se base sur le calcul de métriques physiques (SD, MTF, NPS, etc.) mesurées dans des conditions bien définies, le plus souvent sur fantômes. Bien que cette démarche soit limitée car elle n'intègre pas la perception des radiologues, elle permet de caractériser de manière rapide et simple certaines propriétés d'une image. La seconde approche, dite « clinique », est basée sur l'évaluation de structures anatomiques (critères diagnostiques) présentes sur les images de patients. Des radiologues, impliqués dans l'étape d'évaluation, doivent qualifier la qualité des structures d'un point de vue diagnostique en utilisant une échelle de notation simple. Cette approche, lourde à mettre en place, a l'avantage d'être proche du travail du radiologue et peut être considérée comme méthode de référence.¦Parmi les principaux résultats de ce travail, il a été montré que les algorithmes itératifs statistiques étudiés en clinique (ASIR?, VEO?) ont un important potentiel pour réduire la dose au CT (jusqu'à-90%). Cependant, par leur fonctionnement, ils modifient l'apparence de l'image en entraînant un changement de texture qui pourrait affecter la qualité du diagnostic. En comparant les résultats fournis par les approches « clinique » et « physique », il a été montré que ce changement de texture se traduit par une modification du spectre fréquentiel du bruit dont l'analyse permet d'anticiper ou d'éviter une perte diagnostique. Ce travail montre également que l'intégration de ces nouvelles techniques de reconstruction en clinique ne peut se faire de manière simple sur la base de protocoles utilisant des reconstructions classiques. Les conclusions de ce travail ainsi que les outils développés pourront également guider de futures études dans le domaine de la qualité d'image, comme par exemple, l'analyse de textures ou la modélisation d'observateurs pour le CT.¦-¦Computed tomography (CT) is an imaging technique in which interest has been growing since it first began to be used in the early 1970s. In the clinical environment, this imaging system has emerged as the gold standard modality because of its high sensitivity in producing accurate diagnostic images. However, even if a direct benefit to patient healthcare is attributed to CT, the dramatic increase of the number of CT examinations performed has raised concerns about the potential negative effects of ionizing radiation on the population. To insure a benefit - risk that works in favor of a patient, it is important to balance image quality and dose in order to avoid unnecessary patient exposure.¦If this balance is important for adults, it should be an absolute priority for children undergoing CT examinations, especially for patients suffering from diseases requiring several follow-up examinations over the patient's lifetime. Indeed, children and young adults are more sensitive to ionizing radiation and have an extended life span in comparison to adults. For this population, the risk of developing cancer, whose latency period exceeds 20 years, is significantly higher than for adults. Assuming that each patient examination is justified, it then becomes a priority to optimize CT acquisition protocols in order to minimize the delivered dose to the patient. Over the past few years, CT advances have been developing at a rapid pace. Since 2009, new iterative image reconstruction techniques, called statistical iterative reconstructions, have been introduced in order to decrease patient exposure and improve image quality.¦The goal of the present work was to determine the potential of statistical iterative reconstructions to reduce dose as much as possible without compromising image quality and maintain diagnosis of children and young adult examinations.¦The optimization step requires the evaluation of the delivered dose and image quality useful to perform diagnosis. While the dose is estimated using CT indices (CTDIV0| and DLP), the particularity of this research was to use two radically different approaches to evaluate image quality. The first approach, called the "physical approach", computed physical metrics (SD, MTF, NPS, etc.) measured on phantoms in well-known conditions. Although this technique has some limitations because it does not take radiologist perspective into account, it enables the physical characterization of image properties in a simple and timely way. The second approach, called the "clinical approach", was based on the evaluation of anatomical structures (diagnostic criteria) present on patient images. Radiologists, involved in the assessment step, were asked to score image quality of structures for diagnostic purposes using a simple rating scale. This approach is relatively complicated to implement and also time-consuming. Nevertheless, it has the advantage of being very close to the practice of radiologists and is considered as a reference method.¦Primarily, this work revealed that the statistical iterative reconstructions studied in clinic (ASIR? and VECO have a strong potential to reduce CT dose (up to -90%). However, by their mechanisms, they lead to a modification of the image appearance with a change in image texture which may then effect the quality of the diagnosis. By comparing the results of the "clinical" and "physical" approach, it was showed that a change in texture is related to a modification of the noise spectrum bandwidth. The NPS analysis makes possible to anticipate or avoid a decrease in image quality. This project demonstrated that integrating these new statistical iterative reconstruction techniques can be complex and cannot be made on the basis of protocols using conventional reconstructions. The conclusions of this work and the image quality tools developed will be able to guide future studies in the field of image quality as texture analysis or model observers dedicated to CT.

Personality and repeated suicide attempts in dependent adolescents and young adults.

This study compared personality characteristics of subjects with dependence disorders who had previously made a suicide attempt. The population, recruited in France, Belgium, and Switzerland, was composed of 570 subjects (225 females, 345 males, mean age = 27.3, SD = 8.5). The subjects' psychological dimensions were investigated by means of several self-report questionnaires including: BDI-13 (Beck), Sensation-Seeking Scale (Zuckerman), Toronto Alexithymia Scale (Taylor), Interpersonal Dependency Inventory (Hirschfeld), MMPI-2, and some additional scales. For most dimensions, repeat attempters, both past and recent, but more specifically the recent repeaters, had a more severe psychological profile compared to the other suicide attempters.

Non-medical prescription drug and illicit street drug use among young Swiss men and associated mental health issues.

Non-medical use of prescription drugs (NMUPD) is increasing among the general population, particularly among teenagers and young adults. Although prescription drugs are considered safer than illicit street drugs, NMUPD can lead to detrimental consequences. The aim of the present study was to investigate the relationship between drug use (NMUPD on the one side, illicit street drugs on the other side) with mental health issues and then compare these associations. A representative sample of 5719 young Swiss men aged around 20 years filled in a questionnaire as part of the ongoing baseline Cohort Study on Substance Use Risk Factors (C-SURF). Drug use (16 illicit street drugs and 5 NMUPDs, including sleeping pills, sedatives, pain killers, antidepressants, stimulants) and mental health issues (depression, SF12) were assessed. Simple and multiple linear regressions were employed. In simple regressions, all illicit and prescription drugs were associated with poorer mental health. In multiple regressions, most of the NMUPDs, except for stimulants, were significantly associated with poorer mental health and with depression. On the contrary, the only associations that remained significant between illicit street drugs and mental health involved cannabis. NMUPD is of growing concern not only because of its increasing occurrence, but also because of its association with depression and mental health problems, which is stronger than the association observed between these problems and illicit street drug use, excepted for cannabis. Therefore, NMUPD must be considered in screening for substance use prevention purposes.

Unstable shoes increase energy expenditure of obese patients.

BACKGROUND: Ergonomic unstable shoes, which are widely available to the general population, could increase daily non-exercise activity thermogenesis as the result of increased muscular involvement. We compared the energy expenditure of obese patients during standing and walking with conventional flat-bottomed shoes versus unstable shoes. METHODS: Twenty-nine obese patients were asked to stand quietly and to walk at their preferred walking speed while wearing unstable or conventional shoes. The main outcome measures were metabolic rate of standing and gross and net energy cost of walking, as assessed with indirect calorimetry. RESULTS: Metabolic rate of standing was higher while wearing unstable shoes compared with conventional shoes (1.11 ± 0.20 W/kg(-1) vs 1.06 ± 0.23 W/kg(-1), P=.0098). Gross and net energy cost of walking were higher while wearing unstable shoes compared with conventional shoes (gross: 4.20 ± 0.42 J/kg(-1)/m(-1)vs 4.01 ± 0.39 J/kg(-1)/m(-1), P=.0035; net: 3.37 ± 0.41 J/kg(-1)/m(-1) vs 3.21 ± 0.37 J/kg(-1)/m(-1); P=.032). CONCLUSION: In obese patients, it is possible to increase energy expenditure of standing and walking by means of ergonomic unstable footwear. Long-term use of unstable shoes may eventually prevent a positive energy balance.

Development of a cost-effective method for platelet-rich plasma (PRP) preparation for topical wound healing.

Platelet-rich plasma (PRP) is a volume of plasma fraction of autologous blood having platelet concentrations above baseline whole-blood values due to processing and concentration. PRP is used in various surgical fields to enhance soft-tissue and bone healing by delivering supra-physiological concentrations of autologous platelets at the site of tissue damage. These preparations may provide a good cellular source of various growth factors and cytokines, and modulate tissue response to injury. Common clinically available materials for blood preparations combined with a two-step centrifugation protocol at 280g each, to ensure cellular component integrity, provided platelet preparations which were concentrated 2-3 fold over total blood values. Costs were shown to be lower than those of other methods which require specific equipment and high-cost disposables, while safety and traceability can be increased. PRP can be used for the treatment of wounds of all types including burns and also of split-thickness skin graft donor sites, which are frequently used in burn management. The procedure can be standardized and is easy to adapt in clinical settings with minimal infrastructure, thus enabling large numbers of patients to benefit from a form of cellular therapy.

Influence of initial foot dorsal flexion on vertical jump and running performance.

Several studies (on an inclined platform or with special shoes) have reported improved jump performance when the ankle was in a dorsiflexion (DF) position. The present study aims to test whether shoes inducing moderate DF modify vertical jump performance and energy cost. Twenty-one young, healthy female subjects (30 +/- 6 yr, 58 +/- 6 kg, O2max 45 +/- 3 mLxkg-1xmin-1, mean +/- SD) participated in the study. Jump performance was tested with subjects either wearing 4 degrees DF or standard (S) shoes. The jump tests (performed on a force platform) consisted of squat jump (SJ), countermovement jump (CMJ), and continuous jumps (CJ) during 15 seconds. Measured parameters were jump height, speed at take off, and maximal and average power. Oxygen uptake was measured on a treadmill while subjects ran at 95% of the anaerobic threshold during a 7-minute steady-state period. As compared with S shoes, DF shoes significantly improved the height of SJ (31 +/- 4 cm vs. 34 +/- 4 cm, p = 0.0001), CMJ (32 +/- 4 cm vs. 34 +/- 4 cm, p = 0.0004), and CJ (17.5 +/- 4.2 cm vs. 22.0 +/- 6.0 cm, p = 0.0001). Speed at take off was also significantly higher. Mean power significantly increased in SJ and CJ but not in CMJ. Oxygen uptake was not different between conditions (p = 0.40). Dorsiflexion shoes induce a significant increase in jump performance. These results are in accordance with the concept that a DF of the ankle may induce an increase of the length and strength of the triceps surae (higher torque). However, wearing DF shoes did not require more energy during running. Dorsiflexion shoes could be used to increase jump performance in several sports such as volleyball in which jump height is essential.

Approche multidisciptinaire des coûts humains des lombalgies [Human cost of low back pain: a multi-disciplinary approach]

The valuation of human costs is a necessity, but this task poses many problems of method. A team made of a philosopher, a psychologist and a physician has been working with economist researchers in order to look into the meaning that the preferences announced at the time of the inquiries on human costs by QALY methods could assume. These methods are often used to obtain a valuation of the impact of a health attack on people's quality of life. The methods--in the frame of the argument assumed by the economic theory on well-being--hypothesize that people's choices depend mainly on cognitive work. The qualitative interviews show that the psychological construction process for the announced preferences largely overlap this frame. In this paper the authors hastily tackle the factors which have an effect on the preferences. They conclude that the QALY methods don't seem to be able to assess the quality of life nori to valuate the damage that the quality of life could include.

The selective migration of young graduates : which of them return to their rural home region and which do not?

This paper addresses the migration behaviours of young university graduates from a rural region in Switzerland. Based on a questionnaire survey, it compares graduates' current place of residence (i.e. whether or not they returned to their home region) with characteristics related to their socio-familial, migration and professional trajectories. The propensity to return varies not only according to labour market variables (employment opportunities), but also to other factors, some of which have even more influence than job opportunities. The graduates' life course position (kind of household), their partners' characteristics (level of education and home region) and their family background (socio-economic status and history of migration) all play a central role. On the whole, results show that migration appears as a selective and complex process embedded in the life course of graduates.

Ad libitum intake of a high-carbohydrate or high-fat diet in young men: effects on nutrient balances.

The effect of diet composition [high-carbohydrate, low-fat (HC) and high-fat, low-carbohydrate (HF) diets] on macronutrient intakes and nutrient balances was investigated in young men of normal body weight. Eleven subjects were studied on two occasions for 48 h in a whole-body indirect calorimeter in a crossover design. Subjects selected their meals from a list containing a large variety of common food, which had a food quotient > 0.85 for the HC diet and < 0.85 for the HF diet. The average ad libitum intake was 14.41 +/- 0.85 MJ/d (67%, 18%, and 15% of energy as carbohydrate, fat, and protein, respectively) with the HC diet and 18.25 +/- 0.90 MJ/d (26%, 61%, and 13% of energy as carbohydrate, fat, and protein, respectively) with the HF diet. Total energy expenditure was not significantly influenced by diet composition: 10.46 +/- 0.27 and 10.97 +/- 0.22 MJ/d for the HC and HF diets, respectively. During the 2 test days, cumulative carbohydrate storage was 418 +/- 72 and 205 +/- 47 g, and fat balance was 29 +/- 17 and 291 +/- 29 g with the HC and HF diets, respectively. Only the HF diet induced a significantly positive fat balance. These results emphasize the important role of the dietary fat content in body fat storage.

Right coronary MR angiography at 7 T: a direct quantitative and qualitative comparison with 3 T in young healthy volunteers.

PURPOSE: To objectively compare quantitative parameters related to image quality attained at coronary magnetic resonance (MR) angiography of the right coronary artery (RCA) performed at 7 T and 3 T. MATERIALS AND METHODS: Institutional review board approval was obtained, and volunteers provided signed informed consent. Ten healthy adult volunteers (mean age ± standard deviation, 25 years ± 4; seven men, three women) underwent navigator-gated three-dimensional MR angiography of the RCA at 7 T and 3 T. For 7 T, a custom-built quadrature radiofrequency transmit-receive surface coil was used. At 3 T, a commercial body radiofrequency transmit coil and a cardiac coil array for signal reception were used. Segmented k-space gradient-echo imaging with spectrally selective adiabatic fat suppression was performed, and imaging parameters were similar at both field strengths. Contrast-to-noise ratio between blood and epicardial fat; signal-to-noise ratio of the blood pool; RCA vessel sharpness, diameter, and length; and navigator efficiency were quantified at both field strengths and compared by using a Mann-Whitney U test. RESULTS: The contrast-to-noise ratio between blood and epicardial fat was significantly improved at 7 T when compared with that at 3 T (87 ± 34 versus 52 ± 13; P = .01). Signal-to-noise ratio of the blood pool was increased at 7 T (109 ± 47 versus 67 ± 19; P = .02). Vessel sharpness obtained at 7 T was also higher (58% ± 9 versus 50% ± 5; P = .04). At the same time, RCA vessel diameter and length and navigator efficiency showed no significant field strength-dependent difference. CONCLUSION: In our quantitative and qualitative study comparing in vivo human imaging of the RCA at 7 T and 3 T in young healthy volunteers, parameters related to image quality attained at 7 T equal or surpass those from 3 T.

Association of smoking and nicotine dependence with pre-diabetes in young and healthy adults.

INTRODUCTION: Several studies have shown an increased risk of type 2 diabetes among smokers. Therefore, the aim of this analysis was to assess the relationship between smoking, cumulative smoking exposure and nicotine dependence with pre-diabetes. METHODS: We performed a cross-sectional analysis of healthy adults aged 25-41 in the Principality of Liechtenstein. Individuals with known diabetes, Body Mass Index (BMI) >35 kg/m² and prevalent cardiovascular disease were excluded. Smoking behaviour was assessed by self-report. Pre-diabetes was defined as glycosylated haemoglobin between 5.7% and 6.4%. Multivariable logistic regression models were done. RESULTS: Of the 2142 participants (median age 37 years), 499 (23.3%) had pre-diabetes. There were 1,168 (55%) never smokers, 503 (23%) past smokers and 471 (22%) current smokers, with a prevalence of pre-diabetes of 21.2%, 20.9% and 31.2%, respectively (p <0.0001). In multivariable regression models, current smokers had an odds ratio (OR) of pre-diabetes of 1.82 (95% confidential interval (CI) 1.39; 2.38, p <0.0001). Individuals with a smoking exposure of <5, 5-10 and >10 pack-years had an OR (95% CI) for pre-diabetes of 1.34 (0.90; 2.00), 1.80 (1.07; 3.01) and 2.51 (1.80; 3.59) (p linear trend <0.0001) compared with never smokers. A Fagerström score of 2, 3-5 and >5 among current smokers was associated with an OR (95% CI) for pre-diabetes of 1.27 (0.89; 1.82), 2.15 (1.48; 3.13) and 3.35 (1.73; 6.48) (p linear trend <0.0001). DISCUSSION: Smoking is strongly associated with pre-diabetes in young adults with a low burden of smoking exposure. Nicotine dependence could be a potential mechanism of this relationship.

Statins for cardiovascular prevention according to different strategies: a cost analysis.

Background: Several studies have shown that treatment with HMG-CoA reductase inhibitors (statins) can reduce coronary heart disease (CHD) rates. However, the cost effectiveness of statin treatment in the primary prevention of CHD has not been fully established. Objective: To estimate the costs of CHD prevention using statins in Switzerland according to different guidelines, over a 10-year period. Methods: The overall 10-year costs, costs of one CHD death averted, and of 1 year without CHD were computed for the European Society of Cardiology (ESC), the International Atherosclerosis Society (IAS), and the US Adult Treatment Panel III (ATP-III) guidelines. Sensitivity analysis was performed by varying number of CHD events prevented and costs of treatment. Results: Using an inflation rate of medical costs of 3%, a single yearly consultation, a single total cholesterol measurement per year, and a generic statin, the overall 10-year costs of the ESC, IAS, and ATP-III strategies were 2.2, 3.4, and 4.1 billion Swiss francs (SwF [SwF1 = $US0.97]). In this scenario, the average cost for 1 year of life gained was SwF352, SwF421, and SwF485 thousand, respectively, and it was always higher in women than in men. In men, the average cost for 1 year of life without CHD was SwF30.7, SwF42.5, and SwF51.9 thousand for the ESC, IAS, and ATP-III strategies, respectively, and decreased with age. Statin drug costs represented between 45% and 68% of the overall preventive cost. Changing the cost of statins, inflation rates, or number of fatal and non-fatal cases of CHD averted showed ESC guidelines to be the most cost effective. Conclusion: The cost of CHD prevention using statins depends on the guidelines used. The ESC guidelines appear to yield the lowest costs per year of life gained free of CHD.