Cardiac single-photon emission tomography with a 90 degrees dual-head system

Dual-head single-photon emission tomography (SPET) systems which permit a 90 degrees orientation of the heads provide a twofold increase in sensitivity for 180 degrees SPET compared with single-head systems. Since such systems have additional mechanical and electrical alignment and stability requirements, clinical equivalency for myocardial perfusion SPET must be demonstrated. Accordingly, we studied 26 subjects who underwent exercise thallium scintigraphy consecutively with both single-head and dual-head systems. Image acquisition was similar, except that the dual-head study took one-half the time. Image reconstruction was identical. Images were interpreted in a blinded fashion, and rated for technical quality. All 26 studies were equivalently interpreted for the presence or absence of perfusion defects. Fourteen of the studies were judged to be technically equivalent; seven were judged to be slightly better with the single-head system; three were judged to be slightly better with the dual-head system; and two were judged to be definitely better with the dual-head system. We conclude that dual-head 90 degrees systems provide equivalent clinical performance in half the acquisition time.     

Monte Carlo calculation of point-spread functions of Comptonscatter cameras

A technique has been devised for independently determining the energy and spatial resolution components of the point-spread functions of electronically collimated (Compton scatter) imaging devices using a Monte Carlo method. Monte Carlo runs are performed for the device being examined, and detailed records of exact energy loss and spatial coordinates of each interaction for each particle in the simulation are made. Taking resolution parameters from the known performance of the detectors, measured data is simulated by sampling from Gaussian distributions (for both energy and position) about the exact interaction energy and position in both detectors, for each Monte Carlo history. By back-projecting cones on an event-by-event basis and calculating the closest approach of the cone to the known source point using the simulated measurement data for one of the energy and position variables and the exact interaction data for the rest of the variables, the effect of the variable in question on the point spread can be isolated. In this paper the authors present the calculations of the contribution to the point-spread function of the energy and spatial resolution in each detector for various source positions for a representative Compton camera configuration     

Comorbidity and course of psychiatric disorders in a community sample of former prisoners of war

OBJECTIVE: The authors assessed DSM-III-R disorders among American former prisoners of war. Comorbidity, time of onset, and the relationship of trauma severity to complicated versus uncomplicated posttraumatic stress disorder (PTSD) were examined. METHOD: A community sample (N=262) of men exposed to combat and imprisonment was assessed by clinicians using the Structured Clinical Interview for DSM-III-R. RESULTS: The rates of comorbidity among the men with PTSD were lower than rates from community samples assessed by lay interviewers. Over one-third of the cases of lifetime PTSD were uncomplicated by another axis I disorder; over one-half of the cases of current PTSD were uncomplicated. PTSD almost always emerged soon after exposure to trauma. Lifetime PTSD was associated with increased risk of lifetime panic disorder, major depression, alcohol abuse/dependence, and social phobia. Current PTSD was associated with increased risk of current panic disorder, dysthymia, social phobia, major depression, and generalized anxiety disorder. Relative to PTSD, the onset of the comorbid disorders was as follows: major depression, predominantly secondary; alcohol abuse/dependence and agoraphobia, predominantly concurrent (same year); social phobia, equal proportions primary and concurrent; and panic disorder, equal proportions concurrent and secondary. Trauma exposure was comparable in the subjects with complicated and uncomplicated PTSD. CONCLUSIONS: The types of comorbid diagnoses and their patterns of onset were comparable to the diagnoses and patterns observed in other community samples. The findings support the validity of the PTSD construct; PTSD can be distinguished from comorbid disorders. Uncomplicated PTSD may be more common than previous studies suggest, particularly in clinician-assessed subjects exposed to severe trauma.     

Stability of mechanical exhaust systems

The mechanical exhaust system, where outdoor air is supplied through infiltration and devices in the building shell, is a common ventilation technique in multi-family buildings in Europe. The objective of this paper is to determine how well the system meets indoor air quality standards and regulations and how sensitive it is to disturbances, such as window opening, temperature differences and resident behavior, and how different building construction parameters affect the airflow. A simple model of a multi-family building has been simulated with a multi-zone infiltration program. It was found that the system almost never fulfills the regulations and that the actions of one resident can often affect the airflow in other apartments. The use of standards and regulations defining indoor air quality and energy efficiency will be ineffective for these systems because they are not stable, that is, sensitive to disturbances such as weather changes and resident behavior.     

Synthesis and Screening of t-Bu-CyMe4-BTBP,and Comparison with CyMe4-BTBP

The effect of adding a t-butyl group to the core molecule of CyMe₄-BTBP, with the aim of improving solubility in organic diluents, has been studied with regard to the extraction of Am(III) and Eu(III) from HNO₃. Synthesis of t-Bu-CyMe₄-BTBP is described in detail. Metal nitrates are extracted from nitric acid in the form of 1:2 complexes, M(NO₃)₃(BTBP)₂. Whether in 1-octanol, kerosene, or cyclohexanone diluents, t-Bu-CyMe₄-BTBP extracts with larger distribution ratios but with slower kinetics than CyMe₄-BTBP. The general trends previously observed for CyMe₄-BTBP regarding the diluent and modifier influence were also found for t-Bu-CyMe₄-BTBP.     

Evaluation of a pressure pulse in a fractured‐rock aquifer to reduce uncertainty of hydraulic conductivity measurements,Rio Grande Rift,New Mexico,United States

Fractured‐rock aquifers are inherently difficult for determining flow dynamics because of variability in fracture orientation and extension. A confined, fractured‐rock aquifer in a semi‐arid mountainous area of the Rio Grande Rift Zone was analysed for its response to recharge events that produced a pressure pulse within its potentiometric surface. The pulse was evaluated at the well scale and subaquifer level to evaluate flowpaths, travel times and dispersion and compare the bulk‐scale aquifer response to possible velocities from slug test hydraulic conductivity measurements. Travel time and dispersion from the pulse proved comparable to probable travel times based on hydraulic conductivity measurements. Evaluation of the pressure pulse and the hydraulic conductivity measurements allowed for a holistic interpretation of the fractured‐rock aquifer through analysis of two distinct data sets that provided corroborative evidence of flow dynamics and fracture connectivity. This holistic approach reduced uncertainty regarding the individual hydraulic conductivity values.     

Posttraumatic stress disorder in a community group of former prisoners of war: a normative response to severe trauma

OBJECTIVE: The goal of this study was to assess and describe the long-term impact of traumatic prisoner of war (POW) experiences within the context of posttraumatic psychopathology. Specifically, the authors attempted to investigate the relative degree of normative response represented by posttraumatic stress disorder (PTSD) in comparison to other DSM axis I disorders often found to be present, either alone or concomitant with other disorders, in survivors of trauma. METHOD: A community group of 262 U.S. World War II and Korean War former POWs was recruited. These men had been exposed to the multiple traumas of combat, capture, and imprisonment, yet few had ever sought mental health treatment. They were assessed for psychopathology with diagnostic interviews and psychodiagnostic testing. Regression analyses were used to assess the contributions of age at capture, war trauma, and postwar social support to PTSD and the other diagnosed disorders. RESULTS: More than half of the men (53%) met criteria for lifetime PTSD, and 29% met criteria for current PTSD. The most severely traumatized group (POWs held by the Japanese) had PTSD lifetime rates of 84% and current rates of 59%. Fifty-five percent of those with current PTSD were free from the other current axis I disorders (uncomplicated PTSD). In addition, 34% of those with lifetime PTSD had PTSD as their only lifetime axis I diagnosis. Regression analyses indicated that age at capture, severity of exposure to trauma, and postmilitary social support were moderately predictive of PTSD and only weakly predictive of other disorders. CONCLUSIONS: These findings indicate that PTSD is a persistent, normative, and primary consequence of exposure to severe trauma.     

A Mixture of Endocrine Disrupting Chemicals Associated with Lower Birth Weight in Children Induces Adipogenesis and DNA Methylation Changes in Human Mesenchymal Stem Cells

Endocrine Disrupting Chemicals (EDCs) are man-made compounds that alter functions of the endocrine system. Environmental mixtures of EDCs might have adverse effects on human health, even though their individual concentrations are below regulatory levels of concerns. However, studies identifying and experimentally testing adverse effects of real-life mixtures are scarce. In this study, we aimed at evaluating an epidemiologically identified EDC mixture in an experimental setting to delineate its cellular and epigenetic effects. The mixture was established using data from the Swedish Environmental Longitudinal Mother and child Asthma and allergy (SELMA) study where it was associated with lower birth weight, an early marker for prenatal metabolic programming. This mixture was then tested for its ability to change metabolic programming of human mesenchymal stem cells. In these cells, we assessed if the mixture induced adipogenesis and genome-wide DNA methylation changes. The mixture increased lipid droplet accumulation already at concentrations corresponding to levels measured in the pregnant women of the SELMA study. Furthermore, we identified differentially methylated regions in genes important for adipogenesis and thermogenesis. This study shows that a mixture reflecting human real-life exposure can induce molecular and cellular changes during development that could underlie adverse outcomes.