Sagittal thin-section fast FLAIR is superior to conventional axial proton-density- and T2-weighted SE pulse sequences for detection of MS plaques in the brain.
The purpose of this study was to assess gradient magnetic-field-induced acoustic noise levels associated with the use of echo planar imaging (EPI) and three-dimensional fast spin echo (3D-FSE) pulse sequences. Acoustic noise measurements were obtained from two different high field-strength MR systems (1.5 T, Siemens and General Electric Co.) under ambient noise conditions and the use of EPI and 3D-FSE pulse sequences. Parameters were selected to produce "worst case" acoustic noise levels. Acoustic noise recordings were made at the entrance, the center, and at the exit of the magnet bores with a specially designed microphone that was unperturbed by electromagnetic fields. The highest ambient noise levels (A-weighted scale) were 67 dB (Siemens: the same values were recorded at the center and at the exit) and 78 dB (General Electric Co.; recorded at the exit). The highest acoustic noise levels recorded during activation of the gradient magnetic fields were 114 dB (Siemens) and 115 dB (General Electric Co.) and those occurred at the centers of the MR systems with the use of the EPI technique. Gradient magnetic fields associated with the use of EPI and 3D-FSE techniques produced acoustic noise levels that were within permissible levels recommended by federal guidelines.
Subcallosal striations are thought to represent perivenular demyelination, that is, the same process that later produces the "ovoid" lesions visible on routine MR images. Subcallosal striations are not seen on routine axial MR images and can be seen only on 2-mm sagittal FLAIR images.
Infection of nonhuman primates (NHPs) with monkeypox virus (MPXV) is currently being developed as an animal model of variola infection in humans. We used positron emission tomography and computed tomography (PET/CT) to identify inflammatory patterns as predictors for the outcome of MPXV disease in NHPs. Two NHPs were sublethally inoculated by the intravenous (IV) or intrabronchial (IB) routes and imaged sequentially using fluorine-18 fluorodeoxyglucose ( 18 FDG) uptake as a nonspecific marker of inflammation/immune activation. Inflammation was observed in the lungs of IB-infected NHPs, and bilobular involvement was associated with morbidity. Lymphadenopathy and immune activation in the axillary lymph nodes were evident in IV-and IB-infected NHPs. Interestingly, the surviving NHPs had significant 18 FDG uptake in the axillary lymph nodes at the time of MPXV challenge with no clinical signs of illness, suggesting an association between preexisting immune activation and survival. Molecular imaging identified patterns of inflammation/immune activation that may allow risk assessment of monkeypox disease.Monkeypox virus (MPXV) is an emerging zoonotic pathogen that results in up to 10% mortality in humans [1]. Due to the similarity of orthopoxviruses, live vaccines used in smallpox eradication programs induced cross-protective immunity against MPXV infections. Successful eradication of smallpox rendered vaccinations unnecessary but has resulted in an increasingly unvaccinated population susceptible to MPXV infection. In addition, the increased efficiency of human-to-human transmission of MPXV, the bioterrorism threat of smallpox and MPXV, and the increase in the observed number of animal hosts position MPXV as a potential large-scale public health threat [2][3][4]. Knowledge of clinical manifestations and temporal progression of monkeypox disease is limited to data collected from rare outbreaks in remote regions of the Congo Basin and West Africa. However, a recent monkeypox outbreak in the United States led to a more complete clinical characterization with detailed analysis of the risk factors of MPXV transmission [5][6][7]. To date, clinical observations show that monkeypox infection resembles variola infection, with fever and malaise followed by a peripherally distributed vesiculopustular rash [8][9][10]. However, pronounced lymphadenopathy develops in the majority of MPXV patients, distinguishing it from variola virus infection [11]. To gain better understanding of monkeypox disease and counteract the threat of human orthopoxvirus infection, animal models using nonhuman primates (NHPs) are being developed using different routes of MPXV infection. Intravenous (IV) inoculation of MPXV in NHPs results in an accelerated (shortened prodromal phase) fulminant disease course with severe lesions. Intratracheal, intranasal, and intrabronchial (IB) administration of MPXV mimics more closely the aerosol transmission route of MPXV in humans and better reflects the temporal progression of human disease [12][13][14].
Functional MRI in awake-behaving primates is an emerging tool for bridging the gap between human fMRI and neurophysiology information from nonhuman primates. We report the use of magnetite dextran nanoparticles (Feridex) as a blood-pool agent to enhance fMRI contrast-to-noise (CNR) in primate FMRI. The intravascular half-life of the magnetite dextran was long compared to lanthanide chelates (T(1/2) = 198 min) with shortened T(2) relaxation observed in blood and cerebral cortex. Greater than 3-fold enhancement in the percentage MR signal change was observed using nanoparticles (13%) compared with conventional BOLD fMRI (4%). The calculated regional cerebral blood volume in macaque primary visual cortex increased 32% with photic stimulation. The increased CNR allows greater flexibility in the design of awake-behaving primate fMRI studies with the potential for improvements in resolution and significantly shortened imaging times.
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