Building and Exploitation of Learning Curves to Train Radiographer Students in X-Ray CT Image Postprocessing

IntroductionThis study aims to construct learning curves related to the realization of standardized postprocessing by radiographer students and to discuss their exploitation and interest.Materials and MethodsThis study was carried out in 21 French students in their 3rd year of training. Two postprocessing protocols in CT (#1 traumatic shoulder; #2 petrous bone) were repeated 15 times by each student. Each achievement was timed to obtain overall learning curves. The realization accuracy was also assessed for each student at each repetition.ResultsThe learning rates for the two protocols are 63% and 56%, respectively. The number of repetitions to reach the reference time for each protocol is 11 and 12, respectively. In both protocols, the standard deviations are significantly reduced and stabilized during repetitions. The mean accuracy progresses more quickly in protocol #1.DiscussionThe measured learning rates reflect a rapid learning process for each protocol. The analysis of the standard deviations shows that students have reached a homogeneous level. The average times and accuracies measured during the last repetitions show that the group has reached a high level of performance. Building learning curves helps students measure their progress and motivates them.ConclusionObtaining learning curves allows trainers/supervisors to qualify the learning difficulty of a task while motivating students/radiographers. The use of learning curves is inline with the competency-based training paradigm.     

Estimating Potency for the E max-Model Without Attaining Maximal Effects

The most widely applied model relating drug concentrations to effects is the E_max model. In practice, concentration–effect relationships often deviate from a simple linear relationship but without reaching a clear maximum because a further increase in concentration might be associated with unacceptable or distorting side effects. The parameters for the E_max model can only be estimated with reasonable precision if the curve shows sign of reaching a maximum, otherwise both EC₅₀ and E_max estimates may be extremely imprecise. This paper provides a solution by introducing a new parameter (S₀ ) equal to E_max/EC₅₀ that can be used to characterize potency adequately even if there are no signs of a clear maximum. Simulations are presented to investigate the nature of the new parameter and published examples are used as illustration.     

Reassessment of the accuracy of traditional sperm characteristics and adenosine triphosphate (ATP) in estimating the fertilizing potential of human semen in vivo

Receiver operating characteristic curves and accuracy parameters were computed for traditional sperm characteristics (concentration, motility, morphology) and the number of peroxidase negative cells, and the concentration of adenosine triphosphate (ATP) in semen from populations of fertile and infertile men, and men who achieved a pregnancy after varicocele treatment. The percentage and concentration per millilitre of spermatozoa with rapid linear progressive motility, and the ATP concentration, provided the best discrimination between fertile and treated fertile from infertile men. The misclassification rate was higher for sperm morphology, total progressive motility and viability, whereas sperm concentration and the total sperm count per ejaculate had the worst discriminating power. The number of peroxidase negative cells per 100 spermatozoa was highly specific in identifying men who achieved pregnancy after varicocele treatment. The lower limit of normality of sperm characteristics was remarkably different between fertile men and men achieving pregnancy after treatment or during infertility work-up.     

Chronic modifications of lung and heart development in glucocorticoid-treated newborn rats exposed to hyperoxia or room air

We assessed the mechanics and morphology of the lung in 165 rats treated neonatally with either room air (RA), O₂, RA + steroids, or O₂, + steroids. Newborn Sprague-Dawley male rats were randomly assigned to these groups. O₂,-exposure (0.96-1.0 FiO₂ lasted 5 days, and dexamethasone treatment consisted of eight daily S.C. injections of drug or buffer in successive doses of 0.5,0.4.0.3,0.2,0.1, 0.1. 0.1. and 0.1 mg/kg. At 58 days, right ventricular systolic pressure (RVP) was measured. At 60 days, all rats were sacrificed for obtaining lung weight and DNA, saline pressure-volume (P-V) curves, and morphometry. We weighed right ventricles (RV) and left ventricles + septa (LV). Hyperoxia alone did not, but steroid decreased survival rate to 79.4% (95.3% in RA rats, P < 0.02). Only 21 of 40 (52%) O₂ + steroids rats survived, less than in both RA groups (P < 0.001). RV weight, RVP and muscularization of alveolar duct arteries were significantly increased in O₂ vs. RA rats. In RA + steroids rats, weight of the LV was decreased but RV, RVP, and lung vasculature were not affected. These effects were additive in the O₂ + steroid group. Wet lung weights and DNA were increased for RA + steroid rats over all others. O₂ and steroids shifted the P-V curve to the left and O₂+ steroids still further. Maximal lung volume increased significantly with RA + steroids and still further in O₂ + steroids but not in O₂ alone. O₂ and steroids significantly increased the mean linear intercept and O₂ + steroids even more so. In O₂- and steroid-treated rats, the parenchymal air space increased. In conclusion, both neonatal hyperoxia and steroid administration caused aberrations in the growth of lung and connective tissue. The effects of the two were additive. The vascular system, maximal lung volume, and DNA responded differently, presumably by different modes of action. Pediatr Pulmonol. 1993; 16:81–88. © 1993 Wiley-Liss, Inc.     

孔边裂纹J积分失效评定曲线

计算了单边椭圆缺口试件（ＳＥＮＣＰ）高应变区裂纹的Ｊ积分失效评定曲线（ＦＡＣ），考察了影响ＦＡＣ的几种因素。结果表明：在外加载荷与塑性屈服载荷之比（Ｌｒ）１．０时，用Ｒ６通用失效评定曲线进行结构高应变区裂纹断裂评定与疲劳剩余寿命估算是安全的。     

Removing the effect of SVD algorithmic artifacts present in quantitative MR perfusion studies.

Quantitative cerebral blood flow (CBF) values can be obtained from dynamic susceptibility contrast (DSC) MR perfusion studies using the standard singular value decomposition (sSVD) deconvolution algorithm. Reports in the literature from simulation and in vivo studies suggest that CBF estimates obtained using sSVD deconvolution depend on the arterial-tissue delay (ATD). By contrast, Fourier transform (FT) deconvolution produces CBF estimates that are independent of ATD. The diagnostic reliability of quantitative CBF measurements to define areas of normal tissue flow and tissue at risk is brought into doubt by such gross sensitivity to the specifics of the deconvolution approach. This variation of CBF values with ATD is shown to be an artifact associated with the current implementation of the sSVD deconvolution algorithm. A reformulated version of the SVD deconvolution algorithm (rSVD) is presented and compared to the standard SVD algorithm through simulation and patient case studies.     

Danish version of the Oswestry disability index for patients with low back pain. Part 2: Sensitivity, specificity and clinically significant improvement in two low back pain populations

In studies evaluating the efficacy of clinical interventions, it is of paramount importance that the functional outcome measures are responsive to clinically relevant change. Knowledge thereof is in fact essential for the choice of instrument in clinical trials and for clinical decision-making. This article endeavours to investigate the sensitivity, specificity and clinically significant improvement (responsiveness) of the Danish version of the Oswestry disability index (ODI) in two back pain populations. Two hundred and thirty three patients with low back pain (LBP) and/or leg pain completed a questionnaire booklet at baseline and 8 weeks follow-up. Half of the patients were seen in the primary (PrS) and half in the secondary sectors (SeS) of the Danish Health Care System. The booklet contained the Danish version of the ODI, along with the Roland Morris Questionnaire, the LBP Rating Scale, the SF36 (physical function and bodily pain scales) and a global pain rating. At follow-up, a 7-point transition question (TQ) of patient perceived change and a numeric rating scale relating to the importance of the change were included. Responsiveness was operationalised using three strategies: change scores, standardised response means (SRM) and receiver operating characteristic (ROC) analyses. All methods revealed acceptable responsiveness of the ODI in the two patient populations which was comparable to the external instruments. SRM of the ODI change scores at 2 months follow-up was 1.0 for PrS patients and 0.3 for SeS (raw and percentage). A minimum clinically important change (MCID) from baseline score was established at 9 points (71%) for PrS patients and 8 points (27%) for SeS patients using ROC analyses. This was dependable on the baseline entry score with the MCID increasing with 5 points for every 10 points increase in the baseline score. We conclude that the Danish version of the ODI has comparable responsiveness to other commonly used functional status measures and is appropriate for use in low back pain patients receiving conservative care in both the primary and secondary sector.     

人体肠道生物力学特性的研究

为探讨人体肠道的生物力学特性，采用电子拉伸机对人体肠道进行一维拉伸试验。结果表明，人体肠道应力-应变关系为指数函数关系。人体肠道各段的指数系数a值接近，但材料常数C有一定的差异，说明肠道各段应力-应变趋势是一致的。在一定应力下，肠道各段轴向与环向的相对伸长率是不同的，表明人体肠道具有各向异性的特性。在一定应变下，肠道各段的增量弹性模量不同，结肠增量弹性模量相对较小，因而更容易发生变形。本研究为肠道内窥镜机器人的研制提供了理论基础。     

The Compliance Curve for the Flow Limiting Segments of the Airway

Maximum effort flow-static recoil curves were obtained in 5 healthy subjects breathing air, He/O₂, and SF₆/O₂ mixtures. In 4 of them maximum effort flows corresponded to really maximal flows and their curves were transformed into compliance curves for the flow limiting segments of the airway and analyzed from the point of view of a previously presented lung model (Pedersen and Nielsen 1976). The results showed, that viscosity dependent pressure losses from the alveoli to the flow limiting segments were minimal for air and SF₆/O₂, but not for He/O₂. When viscosity dependent pressure losses could be neglected, then expiration of gases of different densities gave almost identical compliance curves for the flow limiting segments. This supported the applicability of the model. The calculated compliance curves for the flow limiting segments were compared with data from the literature, and the findings indicated that flow limitation during expirations with just maximal flows throughout began in the extrapulmonary airways and moved upstream during the expiration.