Imaging of the orbit plays an important role in the workup of orbital emergencies. Orbital imaging is particularly useful in the emergency department, where clinical history and physical examination may be limited or delayed until the exclusion or treatment of more life-threatening conditions. Cross-sectional orbital imaging with multidetector computed tomography (CT) and magnetic resonance (MR) imaging is commonly performed in addition to ultrasonography. In an emergent setting, CT is the preferred modality when evaluating for intraorbital foreign bodies, fractures, or calcifications within a mass lesion. MR imaging is typically the modality of choice for orbital pathologic conditions, owing to its superior ability to delineate the orbital soft tissues and visual pathways. CT and MR imaging together may supplement clinical evaluation by helping establish an accurate diagnosis, providing an objective assessment of disease extent and progression, and assisting in pretreatment planning. Orbital emergencies have a spectrum of cross-sectional imaging findings in four major categories: infection, trauma, vascular disease, and inflammation. Use of a systematic approach to these entities will assist the radiologist with identifying immediate threats to vision and thereby facilitate prompt clinical management. Familiarity with the clinical presentations also improves the radiologist's diagnostic confidence and role in guiding patient care. This article reviews imaging protocols, relevant orbital anatomy, the role of CT and MR imaging, and key imaging findings of orbital emergencies that the radiologist must know. RSNA, 2017.

Purpose:To investigate the sustained-attention and memory-enhancing neural correlates of the oral administration of methylene blue in the healthy human brain. Materials and Methods:The institutional review board approved this prospective, HIPAA-compliant, randomized, double-blinded, placebocontrolled clinical trial, and all patients provided informed consent. Twenty-six subjects (age range, 22-62 years) were enrolled. Functional magnetic resonance (MR) imaging was performed with a psychomotor vigilance task (sustained attention) and delayed match-to-sample tasks (short-term memory) before and 1 hour after administration of low-dose methylene blue or a placebo. Cerebrovascular reactivity effects were also measured with the carbon dioxide challenge, in which a 2 3 2 repeatedmeasures analysis of variance was performed with a drug (methylene blue vs placebo) and time (before vs after administration of the drug) as factors to assess drug 3 time between group interactions. Multiple comparison correction was applied, with cluster-corrected P , .05 indicating a significant difference. Results:Administration of methylene blue increased response in the bilateral insular cortex during a psychomotor vigilance task (Z = 2.9-3.4, P = .01-.008) and functional MR imaging response during a short-term memory task involving the prefrontal, parietal, and occipital cortex (Z = 2.9-4.2, P = .03-.0003). Methylene blue was also associated with a 7% increase in correct responses during memory retrieval (P = .01). Conclusion:Low-dose methylene blue can increase functional MR imaging activity during sustained attention and short-term memory tasks and enhance memory retrieval.q RSNA, 2016

A 26-year-old female presented with vision loss accompanied by migraine-like headaches. A contrast-enhanced magnetic resonance imaging of the brain was performed which revealed findings suggestive of stroke-like migraine attacks after radiation therapy (SMART) syndrome. SMART syndrome is a delayed complication of brain radiation characterized by neurologic symptoms including migraine-like headaches, seizures, and hemispheric impairment. The purpose of this article is to make the readers aware of this rare complication of brain irradiation. Appropriate diagnosis of SMART syndrome is essential to avoid invasive tests.

Methylene blue USP (MB) is a FDA-grandfathered drug used in clinics to treat methemoglobinemia, carbon monoxide poisoning and cyanide poisoning that has been shown to increase fMRI evoked blood oxygenation level dependent (BOLD) response in rodents. Low dose MB also has memory enhancing effect in rodents and humans. However, the neural correlates of the effects of MB in the human brain are unknown. We tested the hypothesis that a single low oral dose of MB modulates the functional connectivity of neural networks in healthy adults. Task-based and task-free fMRI were performed before and one hour after MB or placebo administration utilizing a randomized, double-blinded, placebo-controlled design. MB administration was associated with a reduction in cerebral blood flow in a task-related network during a visuomotor task, and with stronger resting-state functional connectivity in multiple regions linking perception and memory functions. These findings demonstrate for the first time that low-dose MB can modulate task-related and resting-state neural networks in the human brain. These neuroimaging findings support further investigations in healthy and disease populations.

We discuss two cases of subacute hepatic artery compromise with collateral artery vessel formation that were prospectively diagnosed in July 2007 by sonography and confirmed by angiography. We refer to this phenomenon as "collateral transformation of the hepatic artery."