Imaging Units (imaging + unit)

Distribution by Scientific Domains

Selected Abstracts

Pacemaker Reed Switch Behavior in 0.5, 1.5, and 3.0 Tesla Magnetic Resonance Imaging Units: Are Reed Switches Always Closed in Strong Magnetic Fields?

LUECHINGER, R., et al.: Pacemaker Reed Switch Behavior in 0.5, 1.5, and 3.0 Tesla Magnetic Resonance Imaging Units: Are Reed Switches Always Closed in Strong Magnetic Fields? MRI is established as an important diagnostic tool in medicine. However, the presence of a cardiac pacemaker is usually regarded as a contraindication for MRI due to safety reasons. The aim of this study was to investigate the state of a pacemaker reed switch in different orientations and positions in the main magnetic field of 0.5-, 1.5-, and 3.0-T MRI scanners. Reed switches used in current pacemakers and ICDs were tested in 0.5-, 1.5-, and 3.0-T MRI scanners. The closure of isolated reed switches was evaluated for different orientations and positions relative to the main magnetic field. The field strengths to close and open the reed switch and the orientation dependency of the closed state inside the main magnetic field were investigated. The measurements were repeated using two intact pacemakers to evaluate the potential influence of the other magnetic components, like the battery. If the reed switches were oriented parallel to the magnetic fields, they closed at 1.0 0.2 mT and opened at 0.7 0.2 mT. Two different reed switch behaviors were observed at different magnetic field strengths. In low magnetic fields (< 50 mT), the reed switches were closed. However, in high magnetic fields (> 200 mT), the reed switches opened in 50% of all tested orientations. No difference between the three scanners could be demonstrated. The reed switches showed the same behavior whether they were isolated or an integral part of the pacemakers. The reed switch in a pacemaker or an ICD does not necessarily remain closed in strong magnetic fields at 0.5, 1.5, or 3.0 T and the state of the reed switch may not be predictable with certainty in clinical situations. [source]

Phototunable Microlens Array Based on Polymer Dispersed Liquid Crystals

Gui-Rong Xiong
Abstract A microfluidic system is designed to fabricate polymer dispersed liquid crystal microspheres, whose shape, surface smoothness, and size are controlled. A microlens array (MLA) is constructed by the assembly of the monodispersed microspheres. In the MLA, each microsphere acts as a separate imaging unit. As the liquid crystal (LC) used is a mixed liquid crystal that contain photoresponsive 4-butyl-4-methoxyazobenzene, the imaging capability and light transportation of the MLA can be reversibly controlled by light irradiation. [source]

Have newer cardiovascular drugs reduced hospitalization?

Evidence from longitudinal country-level data on 20 OECD countries
Abstract This study examines the effect of changes in the vintage distribution of cardiovascular system drugs on hospitalization and mortality due to cardiovascular disease using longitudinal country-level data. The vintage of a drug is the first year in which it was marketed anywhere in the world. We use annual data on the utilization of over 1100 cardiovascular drugs (active ingredients) in 20 OECD countries during the period 1995,2003. Countries with larger increases in the share of cardiovascular drug doses that contained post-1995 ingredients had smaller increases in the cardiovascular disease hospital discharge rate, controlling for the quantity of cardiovascular medications consumed per person, the use of other medical innovations (computed tomography scanners and magnetic resonance imaging units), potential risk factors (average consumption of calories, tobacco, and alcohol), and demographic variables (population size and age structure, income, and educational attainment). The estimates also indicate that the use of newer cardiovascular drugs has reduced the average length of stay and the age-adjusted cardiovascular mortality rate, but not the number of potential years of life lost due to cardiovascular disease before age 70 per 100,000 population. The estimates indicate that if drug vintage had not increased during 1995,2004, hospitalization and mortality would have been higher in 2004. We estimate that per capita expenditure on cardiovascular hospital stays would have been 70% ($89) higher in 2004 had drug vintage not increased during 1995,2004. Per capita expenditure on cardiovascular drugs would have been lower in 2004 had drug vintage not increased during 1995,2004. However, our estimate of the increase in expenditure on cardiovascular hospital stays is about 3.7 times as large as our estimate of the reduction in per capita expenditure for cardiovascular drugs that would have occurred ($24). Copyright 2008 John Wiley & Sons, Ltd. [source]