SMAP L-Band Microwave Radiometer: Instrument Design and First Year on Orbit.

The Soil Moisture Active-Passive (SMAP) L-band microwave radiometer is a conical scanning instrument designed to measure soil moisture with 4% volumetric accuracy at 40-km spatial resolution. SMAP is NASA's first Earth Systematic Mission developed in response to its first Earth science decadal survey. Here, the design is reviewed and the results of its first year on orbit are presented.

An RF dosimeter for independent SAR measurement in MRI scanners.

Purpose: The monitoring and management of radio frequency (RF) exposure is critical for ensuring magnetic resonance imaging (MRI) safety. Commercial MRI scanners can overestimate specific absorption rates (SAR) and improperly restrict clinical MRI scans or the application of new MRI sequences, while underestimation of SAR can lead to tissue heating and thermal injury. Accurate scanner-independent RF dosimetry is essential for measuring actual exposure when SAR is critical for ensuring regulatory compliance and MRI safety, for establishing RF exposure while evaluating interventional leads and devices, and for routine MRI quality assessment by medical physicists.

MRI pyschophysics: an experimental framework relating image quality to diagnostic performance metrics.

Purpose: To determine the minimal image quality needed to preserve diagnostic performance relative to arthroscopy in the knee.

Materials And Methods: Synthetic noise was added to images from clinical MRI scans (three-dimensional SPACE pulse sequence; Siemens) from five patients who had undergone knee MRI with arthroscopic follow-up, resulting in 25 simulated sets of images with standardized signal-to-noise ratios (SNRs) of 1, 2, 5, 10, or 20. All cases were scored by four musculoskeletal radiologists progressing from low to high SNR and grading all cartilage surfaces, major ligaments and menisci on a 5-point scale.

A multichannel, real-time MRI RF power monitor for independent SAR determination.

Purpose: Accurate measurements of the RF power delivered during clinical MRI are essential for safety and regulatory compliance, avoiding inappropriate restrictions on clinical MRI sequences, and for testing the MRI safety of peripheral and interventional devices at known RF exposure levels. The goal is to make independent RF power measurements to test the accuracy of scanner-reported specific absorption rate (SAR) over the extraordinary range of operating conditions routinely encountered in MRI.

Methods: A six channel, high dynamic range, real-time power profiling system was designed and built for monitoring power delivery during MRI up to 440 MHz.

MRI acoustic noise can harm experimental and companion animals.

Purpose: To assess possible damage to the hearing of experimental and companion animal subjects of magnetic resonance imaging (MRI) scans.

Materials And Methods: Using animal hearing threshold data and sound level measurements from typical MRI pulse sequences, we estimated "equivalent loudness" experienced by several experimental and companion animals commonly subjects of MRI scans. We compared the equivalent loudness and exam duration to safe noise standards set by the National Institute for Occupational Safety and Health (NIOSH).

Measuring T₂ and T₁, and imaging T₂ without spin echoes.

During adiabatic excitation, the nuclear magnetization in the transverse plane is subject to T(2) (spin-spin) relaxation, depending on the pulse length τ. Here, this property is exploited in a method of measuring T(2) using the ratio of NMR signals acquired with short and long-duration self-refocusing adiabatic pulses, without spin-echoes. This Dual-τ method is implemented with B(1)-insensitive rotation (BIR-4) pulses.

Designing passive MRI-safe implantable conducting leads with electrodes.

Purpose: The presence of implanted electronic devices with conducting leads and electrodes are contraindicated for magnetic resonance imaging (MRI), denying many patients its potential benefits. The prime concern is MRI's radio frequency (RF) fields, which can cause elevated local specific absorption rates (SARs) and potential heat injury. The purpose of this article is to develop and compare a range of passive implantable "MRI-safe" lead designs.

Noise figure limits for circular loop MR coils.

Circular loops are the most common MR detectors. Loop arrays offer improved signal-to-noise ratios (SNRs) and spatial resolution, and enable parallel imaging. As loop size decreases, loop noise increases relative to sample noise, ultimately dominating the SNR.

MRI dynamic range and its compatibility with signal transmission media.

As the number of MRI phased array coil elements grows, interactions among cables connecting them to the system receiver become increasingly problematic. Fiber optic or wireless links would reduce electromagnetic interference, but their dynamic range (DR) is generally less than that of coaxial cables. Raw MRI signals, however, have a large DR because of the high signal amplitude near the center of k-space.

SmartPhantom--an fMRI simulator.

Many informatics tools have emerged to process the voluminous and complex data generated by functional magnetic resonance imaging (fMRI). The interpretation of fMRI exams is largely determined by these tools. However, their performance is hard to evaluate because there is no independent means of calibration.

Active-passive gradient shielding for MRI acoustic noise reduction.

An important source of MRI acoustic noise-magnet cryostat warm-bore vibrations caused by eddy-current-induced forces-can be mitigated by a passive metal shield mounted on the outside of a vibration-isolated, vacuum-enclosed shielded gradient set. Finite-element (FE) calculations for a z-gradient indicate that a 2-mm-thick Cu layer wrapped on the gradient assembly can decrease mechanical power deposition in the warm bore and reduce warm-bore acoustic noise production by about 25 dB. Eliminating the conducting warm bore and other magnet parts as significant acoustic noise sources could lead to the development of truly quiet, fully functioning MRI systems with noise levels below 70 dB.

A culture of threat: right-wing extremism and negative identity formation in German youth.

The specific case of Eastern Germany is illustrative of a more general framework for how identity formation, family processes, and humiliation, alienation, and deprivation are linked to local conditions or situational contexts.

Making MRI quieter.

We have mitigated acoustic noise in a 1.5 T cylindrical MRI scanner equipped with epoxy-potted, shielded gradients. It has been widely assumed that MRI acoustic noise comes overwhelmingly from vibrations of the gradient assembly.

Full house or Pandora's box? The treatment of variability in post-Piagetian research.

This commentary focuses on the conceptual implications of analyses of individual differences in francophone post-Piagetian research. These analyses are viewed as preoccupied by the "American question" of measurement and method, instead of attempting a theoretical account of the issues raised by intraindividual and interindividual variability in development.

Reasoning about responsibilities and obligations in close relationships: a comparison across two cultures.

The study compares sociomoral reasoning of children and adolescents in Iceland, longitudinally assessed at ages 7, 9, 12, and 15 years (N = 97), and in China, cross-sectionally assessed at corresponding ages (N = 350). Participants reasoned about choices, motives, and moral justifications of a protagonist in a sociomoral dilemma. The dilemma allows persons to focus on different concerns (e.

Childhood personality influences on social-cognitive development: a longitudinal study.

The relation of childhood personality to the development of friendship understanding and moral judgment in adolescence was considered in a longitudinal study. Personality at age 7, assessed with the California Child Q-Set, was characterized in terms of ego-resiliency and ego-control. IQ and social class were also measured.

The relation of childhood personality types to adolescent behavior and development: a longitudinal study of Icelandic children.

The relation of childhood personality types, or configurations of personality traits, to adolescent development was examined. Three personality types were identified in an inverse factor analysis of California Child Q-Sort data on 128 Icelandic 7-year-olds: resilient, overcontrolled, and undercontrolled. Growth curve analyses demonstrated that in comparison to children of the other 2 types, children of the resilient personality type had higher levels of academic achievement and lower levels of concentration problems throughout adolescence; resilient children also developed sophisticated friendship reasoning and an internal locus of control more quickly.

Characterization and prediction of gradient acoustic noise in MR imagers.

Gradient acoustic noise has been measured and characterized for an epoxy-potted, shielded gradient assembly in a 1.5 T MRI system. Noise levels vary by 10 dB or more as a function of longitudinal position in the scanner and reflect the pattern of forces applied to the gradient assembly.