A Positron Emission Tomograph based on LSO-APD modules with a sampling ADC read-out system for a students’ advanced laboratory course

A one-day laboratory course on positron emission tomography (PET) for the education of physics students and PhD students in medical physics has been set up. In the course, the physical background and the principles of a PET scanner are introduced. Course attendees set the system in operation, calibrate it using a ²²Na point source and reconstruct different source geometries filled with ¹⁸F. The PET scanner features an individual channel read-out of 96 lutetium oxyorthosilicate (LSO) scintillator crystals coupled to avalanche photodiodes (APD). The analog data of each APD are digitized by fast sampling analog to digital converters (SADC) and processed within field programmable gate arrays (FPGA) to extract amplitudes and time stamps. All SADCs are continuously sampling with a precise rate of 80 MHz, which is synchronous for the whole system. The data is transmitted via USB to a Linux PC, where further processing and the image reconstruction are performed. The course attendees get an insight into detector techniques, modern read-out electronics, data acquisition and PET image reconstruction. In addition, a short introduction to some common software applications used in particle and high energy physics is part of the course.     

Quality assurance of sphincterotomy: A prospective single-centre survey

Quality assurance becomes an increasingly important part of clinical medicine and of the field of endoscopy. Endoscopic sphincterotomy is associated with a fairly high complication rate. We aimed to assess our quality of sphincterotomy for benchmarking by using a prospective electronic database registry, and to identify potential risk factors for post-interventional complications. Over 2 years, 471 sphincterotomies were performed in a single tertiary referral centre. Patient- and procedure-related variables were prospectively recorded with the support of a multi-centre international sphincterotomy registry. Multivariate analysis was performed. The overall post-interventional complication rate was 9.3%. Pancreatitis happened in 5.5%, bleeding in 2.1%, perforation in 1.3%, and cholangitis in 0.4%. In the multivariate analysis following variables remained highly significant and predictive for complications: ‘papilla only in lateral view’ (p=0.001), antiplatelet therapy (p=0.024), and opacification with contrast up to the pancreatic tail (p=0.001). The primary success rate of sphincterotomy was 95.1%. The rate of post-interventional pancreatitis did not differ significantly regardless of the presence of prophylactic pancreatic stent (p=0.56). The outcome of sphincterotomy in our centre matches with literature data. The extent of pancreatic duct opacification has an influence on the pancreatitis rate. Prevention of pancreatitis by inserting pancreatic stents is not confirmed.     

Numerical ability predicts mortgage default

Unprecedented levels of US subprime mortgage defaults precipitated a severe global financial crisis in late 2008, plunging much of the industrialized world into a deep recession. However, the fundamental reasons for why US mortgages defaulted at such spectacular rates remain largely unknown. This paper presents empirical evidence showing that the ability to perform basic mathematical calculations is negatively associated with the propensity to default on one’s mortgage. We measure several aspects of financial literacy and cognitive ability in a survey of subprime mortgage borrowers who took out loans in 2006 and 2007, and match them to objective, detailed administrative data on mortgage characteristics and payment histories. The relationship between numerical ability and mortgage default is robust to controlling for a broad set of sociodemographic variables, and is not driven by other aspects of cognitive ability. We find no support for the hypothesis that numerical ability impacts mortgage outcomes through the choice of the mortgage contract. Rather, our results suggest that individuals with limited numerical ability default on their mortgage due to behavior unrelated to the initial choice of their mortgage.     

Oral Zinc Supplementation for the Treatment of Acute Diarrhea in Children: A Systematic Review and Meta-Analysis

Evidence supporting the impact of therapeutic zinc supplementation on the duration and severity of diarrhea among children under five is largely derived from studies conducted in South Asia. China experiences a substantial portion of the global burden of diarrhea, but the impact of zinc treatment among children under five has not been well documented by previously published systematic reviews on the topic. We therefore conducted a systematic literature review, which included an exhaustive search of the Chinese literature, in an effort to update previously published estimates of the effect of therapeutic zinc. We conducted systematic literature searches in various databases, including the China National Knowledge Infrastructure (CNKI), and abstracted relevant data from studies meeting our inclusion and exclusion criteria. We used STATA 12.0 to pool select outcomes and to generate estimates of percentage difference and relative risk comparing outcomes between zinc and control groups. We identified 89 Chinese and 15 non-Chinese studies for the review, including studies in 10 countries from all WHO geographic regions, and analyzed a total of 18,822 diarrhea cases (9469 zinc and 9353 control). None of the included Chinese studies had previously been included in published pooled effect estimates. Chinese and non-Chinese studies reported the effect of therapeutic zinc supplementation on decreased episode duration, stool output, stool frequency, hospitalization duration and proportion of episodes lasting beyond three and seven days. Pooling Chinese and non-Chinese studies yielded an overall 26% (95% CI: 20%−32%) reduction in the estimated relative risk of diarrhea lasting beyond three days among zinc-treated children. Studies conducted in and outside China report reductions in morbidity as a result of oral therapeutic zinc supplementation for acute diarrhea among children under five years of age. The WHO recommendation for zinc treatment of diarrhea episodes should be supported in all low- and middle-income countries.     

Differentiating normal hyaline cartilage from post-surgical repair tissue using fast gradient echo imaging in delayed gadolinium-enhanced MRI (dGEMRIC) at 3 Tesla

The purpose was to evaluate the relative glycosaminoglycan (GAG) content of repair tissue in patients after microfracturing (MFX) and matrix-associated autologous chondrocyte transplantation (MACT) of the knee joint with a dGEMRIC technique based on a newly developed short 3D-GRE sequence with two flip angle excitation pulses. Twenty patients treated with MFX or MACT (ten in each group) were enrolled. For comparability, patients from each group were matched by age (MFX: 37.1 ± 16.3 years; MACT: 37.4 ± 8.2 years) and postoperative interval (MFX: 33.0 ± 17.3 months; MACT: 32.0 ± 17.2 months). The Δ relaxation rate (ΔR1) for repair tissue and normal hyaline cartilage and the relative ΔR1 were calculated, and mean values were compared between both groups using an analysis of variance. The mean ΔR1 for MFX was 1.07 ± 0.34 versus 0.32 ± 0.20 at the intact control site, and for MACT, 1.90 ± 0.49 compared to 0.87 ± 0.44, which resulted in a relative ΔR1 of 3.39 for MFX and 2.18 for MACT. The difference between the cartilage repair groups was statistically significant. The new dGEMRIC technique based on dual flip angle excitation pulses showed higher GAG content in patients after MACT compared to MFX at the same postoperative interval and allowed reducing the data acquisition time to 4 min.     

Is the center of mass (COM) a reliable parameter for the localization of brain function in fMRI?

The center of mass (COM) in functional MRI studies is defined as the center of a cerebral activation cluster. Although the COM is a well-accepted parameter for exactly localizing brain function, the reliability of COMs has not received much attention until now. Our goal was to investigate COM reliability as a function of the thresholding technique, the threshold level, and the type of COM calculation. Therefore 15 subjects were examined repeatedly using simple hand and tongue movement paradigms. Postprocessing was performed with uncorrected, corrected, and proportional thresholding as well as different threshold levels. Geometric and T-weighted COMs of left-hemispheric primary hand and tongue motor clusters were calculated. The COM variation was evaluated within and between repeated sessions depending on the different postprocessing setups. Mean COM variations over three repeated sessions varied between 1.6 mm and 9.8 mm for the hand paradigm and between 7.0 mm and 14.4 mm for the tongue task. Stringent thresholding techniques and high threshold levels were required to assess reliable results, whereas the kind of COM calculation was of lesser relevance. Thus, COM reliability cannot be presupposed; it depends strongly on the individual postprocessing techniques. This should be considered when using COMs for localizing brain function.