For decades, imaging has been a critical component of the diagnostic evaluation and management of patients suspected of acute ischemic stroke (AIS). With each new advance in the treatment of AIS, the role of imaging has expanded in scope, sophistication, and importance in selecting patients who stand to benefit from potential therapies. Although the field of stroke imaging has been evolving for many years, there have been several major recent changes. Most notably, in late 2017, the window for treatment expanded to 24 h from onset of stroke symptoms in selected patients. Furthermore, for those patients in expanded time windows, guidelines issued in early 2018 now recommend the use of "advanced" imaging techniques in the acute setting, including CT perfusion and MRI, to guide therapeutic decision-making. With these and other changes, the emergency radiologist must be prepared to handle a growing volume and complexity of AIS imaging. This article reviews the various imaging modalities and techniques employed in the imaging of AIS patients, with an emphasis on recommendations from recent randomized controlled trials and national consensus guidelines.

Epipericardial fat necrosis (EPFN) is a rare cause for acute chest. We describe the case of a previously healthy 25-year-old man who presented with sudden onset of left-sided chest pain. Laboratory values showed only mildly elevated d-dimer and electrocardiogram was normal. However, subsequent CT angiogram of the chest revealed fat necrosis in the epipericardial fat, characteristic for EPFN, for which the patient was treated with nonsteroidal anti-inflammatory drug. This case highlights the importance of radiologists to consider the prospect of EPFN in the differential diagnosis of acute chest pain as correct diagnosis allows for conservative management and avoidance of more aggressive techniques in symptomatic patients.

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of aneurysms compared to normal arteries is difficult because of risks associated with tissue collection. Endovascular biopsy is a low-risk alternative method for collecting endothelial cells from aneurysms and comparing them to the same patient's non-aneurysmal endothelial cells. Methods A patient with a large, fusiform, partially thrombosed vertebrobasilar artery aneurysm was recruited for research study after institutional review board approval. We used simple endovascular techniques to collect cells from the patient's vertebrobasilar artery aneurysm and their femoral artery during flow-diverting stent placement. The biopsied cells underwent fluorescence-activated cell sorting (FACS) to isolate viable endotheilal cells. Then, RNA was extracted and cDNA libraries generated using the Smart-seq2 protocol on the Fluidigm C1 platform, followed by sequencing using a Illumina HiSeq2500. Gene expression levels were calculated and filtered as read per kilobase per million mapped reads (RPKM). Principal component analysis, differential gene expression analysis, gene ontology and biological pathway analysis was performed to identify candidate genes and expression pathways related to disease pathogenesis and potential medical therapy. Results Flow-diverting stents were placed in the ipsilateral vertebral artery, and the contralateral vertebral artery was occluded using coils. The vertebrobasilar aneurysm continued to grow and the patient suffered worsening mass effect on the brainstem before entering hospice care. Gene expression analysis identified significant differences in human leukocyte antigen gene complex series (HLAs) and interferon signaling exonuclease genes, implicating a strong role for the immune system in the progression of this patient's aneurysms. In parallel, the patient underwent occipital artery to anterior inferior cerebellar artery (AICA) bypass to treat a separate AICA aneurysm. Histologic evaluation of a resected occipital artery segment demonstrated necrotizing transmural vasculitis compatible with polyarteritis nodosa. Conclusion Endovascular biopsy can be performed to obtain aneurysmal tissue with low risk. Analysis of the collected endothelial cells may yield insight into disease pathogenesis and therapeutic alternatives.