BACKGROUND AND PURPOSE: Spiral MR imaging has several advantages compared with Cartesian MR imaging that can be leveraged for added clinical value. A multicenter multireader study was designed to compare spiral with standard-of-care Cartesian postcontrast structural brain MR imaging on the basis of relative performance in 10 metrics of image quality, artifact prevalence, and diagnostic benefit. MATERIALS AND METHODS: Seven clinical sites acquired 88 total subjects. For each subject, sites acquired 2 postcontrast MR imaging scans: a spiral 2D T1 spin-echo, and 1 of 4 routine Cartesian 2D T1 spin-echo/TSE scans (fully sampled spin-echo at 3T, 1.5T, partial Fourier, TSE). The spiral acquisition matched the Cartesian scan for scan time, geometry, and contrast. Nine neuroradiologists independently reviewed each subject, with the matching pair of spiral and Cartesian scans compared side-by-side, and scored on 10 image-quality metrics (5-point Likert scale) focused on intracranial assessment. The Wilcoxon signed rank test evaluated relative performance of spiral versus Cartesian, while the Kruskal-Wallis test assessed interprotocol differences. RESULTS: Spiral was superior to Cartesian in 7 of 10 metrics (flow artifact mitigation, SNR, GM/WM contrast, image sharpness, lesion conspicuity, preference for diagnosing abnormal enhancement, and overall intracranial image quality), comparable in 1 of 10 metrics (motion artifacts), and inferior in 2 of 10 metrics (susceptibility artifacts, overall extracranial image quality) related to magnetic susceptibility (P , .05). Interprotocol comparison confirmed relatively higher SNR and GM/WM contrast for partial Fourier and TSE protocol groups, respectively (P , .05). CONCLUSIONS: Spiral 2D T1 spin-echo for routine structural brain MR imaging is feasible in the clinic with conventional scanners and was preferred by neuroradiologists for overall postcontrast intracranial evaluation. ABBREVIATIONS: Cart 4 Cartesian; IQ 4 image quality; NA 4 not applicable; SE 4 spin-echo; TSE 4 turbo spin-echo S tructural T1-weighted sequences are a fundamental component of routine postcontrast brain MR imaging examinations. These contrast-enhanced images are used for the diagnostic detection and evaluation of abnormal enhancement, including tumors, infections, and inflammatory diseases. Cartesian 2D T1 spin-echo (SE) is widely used as the standard-of-care, though it is relatively slow due to its single phase-encode per shot k-space coverage, and is not compatible with parallel imaging due to strong free-induction decay artifacts from the refocusing radiofrequency pulse. Two routine speed-up options include Cartesian 2D T1-SE with partial-Fourier k-space coverage, but at the cost of reduced SNR; alternatively, Cartesian 2D T1 turbo spin-echo

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A detailed investigation using interplanetary magnetic field measurements and particle data from ground‐based neutron monitors, lunar sensors, and satellite‐borne detectors has been made of the marked increase in cosmic ray intensity early on August 5, 1972. This enhancement was observed over the wide energy range 0.5 MeV to ∼1 GeV and occurred during the recovery from the greatest recorded Forbush decrease. The increase at ∼0300 UT on August 5 was in approximate coincidence with a decrease from ∼40 to ∼10 γ in the interplanetary field intensity and a change in the field direction from approximately radially outward to approximately radially inward. Sharp decreases in all particle fluxes occurred at about 0500 UT coincident with the increase in interplanetary magnetic field intensity from ∼20 to ∼40 γ and a change in the field direction to radially outward. A detailed analysis of the neutron monitor data shows that the enhanced (∼1 GeV) particle fluxes were not of solar origin. It is suggested that the enhancement occurs in a low‐intensity interplanetary magnetic field bounded by tangential discontinuities, which connects to different particle sources both near the sun and in the outer solar system. The width of the regime was ∼3 × 106 km and resembled a magnetic well convected past the magnetosphere. The similarities in the structure of the event as observed by different detectors, the changes in the helium to proton ratios, the time delay of ∼9 min between observations at Explorer 41 and those at the moon, and a north‐south asymmetry in the enhancement observed by the neutron monitors are all explained in terms of this model.