Imaging in the acute setting of suspected stroke is an important topic to all emergency physicians, neurologists, neurosurgeons and neuroradiologist. When it comes to imaging, the American College of Radiology (ACR) continually updates its guidelines for imaging pathways through the ACR Appropriateness Criteria.1,2 This article is a general review of the imaging modalities currently used to assess and help guide the treatment of strokes.

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Imaging in Acute Stroke

Purpose: To retrospectively assess the usefulness of apparent diffusion coefficients (ADCs) for characterizing renal masses (ie, viable solid tumors, necrotic or cystic tumor areas, and benign cysts). Materials and Methods: The institutional review board waived the requirement for informed consent for this retrospective HIPAA-compliant study. The data of 25 consecutive patients (15 men, 10 women; age range, 39–75 years) who underwent renal magnetic resonance (MR) imaging, including diffusion-weighted imaging, before nephrectomy were included. Renal MR examinations were performed by using transverse T1-weighted dual-echo in-phase and out-of-phase sequences and transverse and coronal T2-weighted single-shot fast spin-echo sequences. Three-dimensional fat-saturated T1-weighted dynamic gadopentetate dimeglumine–enhanced sequences also were performed. Precontrast single-shot spin-echo echo-planar diffusion-weighted images were obtained with b values of 0, 500, and 1000 sec/mm2 at 1.5 T. Regions of interest wer...

Renal Masses: Characterization with Diffusion-weighted MR Imaging—A Preliminary Experience

Clinical radiology and postmortem imaging (Virtopsy) are not the same: Specific and unspecific postmortem signs.

Objective: Cerebral perfusion imaging with computed tomography (CT) or magnetic resonance (MR) is widely available. The optimum perfusion values to identify tissue at risk of infarction in acute stroke are unclear. We systematically reviewed CT and MR perfusion imaging in acute ischemic stroke. Methods: We searched for papers on MR or CT perfusion performed <24 hours after stroke that assessed perfusion thresholds, mean perfusion lesion values, or lesion volumes. We extracted definitions and perfusion values. We compared definitions and evaluated perfusion thresholds for ‘‘nonviable’’/’’at risk’’ and ‘‘at risk’’/’’not at risk tissue’’ thresholds. Results: Among 7,152 papers, 69 met inclusion criteria for analysis of definitions (49 MR and 20 CT), 21 MR (n ¼ 551), and 10 CT (n ¼ 266) papers, median sample size 22, provided thresholds. We found multiple definitions for tissue states, eg, tissue at risk, 18; nonviable tissue, 12; 16, no definition. Perfusion parameters varied widely; eg, 9 different MR, 6 different CT parameters for the ‘‘at risk’’/’’not at risk threshold.’’ Median threshold values varied up to 4-fold, eg, for the ‘‘at risk’’/’’not at risk threshold,’’ median cerebral blood flow ranged from 18 to 37ml/100g/min; mean transit time from 1.8 to 8.3 seconds relative to the contralateral side. The influence of reperfusion and duration of ischemia could not be assessed. Interpretation: CT and MR perfusion imaging viability thresholds in stroke are derived from small numbers of patients, variable perfusion analysis methods and definitions of tissue states. Greater consistency of methods would help determine reliable perfusion viability values for wider clinical use of perfusion imaging. ANN NEUROL 2011;70:384–401

Computed tomography and magnetic resonance perfusion imaging in ischemic stroke: definitions and thresholds.

Diffusion tensor imaging of deep gray matter brain structures: Effects of age and iron concentration

Stroke is a leading cause of mortality and morbidity in the developed world. The goals of an imaging evaluation for acute stroke are to establish a diagnosis as early as possible and to obtain accurate information about the intracranial vasculature and brain perfusion for guidance in selecting the appropriate therapy. A comprehensive evaluation may be performed with a combination of computed tomography (CT) or magnetic resonance (MR) imaging techniques. Unenhanced CT can be performed quickly, can help identify early signs of stroke, and can help rule out hemorrhage. CT angiography and CT perfusion imaging, respectively, can depict intravascular thrombi and salvageable tissue indicated by a penumbra. These examinations are easy to perform on most helical CT scanners and are increasingly used in stroke imaging protocols to decide whether intervention is necessary. While acute infarcts may be seen early on conventional MR images, diffusion-weighted MR imaging is more sensitive for detection of hyperacute ischemia. Gradient-echo MR sequences can be helpful for detecting a hemorrhage. The status of neck and intracranial vessels can be evaluated with MR angiography, and a mismatch between findings on diffusion and perfusion MR images may be used to predict the presence of a penumbra. The information obtained by combining various imaging techniques may help differentiate patients who do not need intravenous or intraarterial therapy from those who do, and may alter clinical outcomes.

State-of-the-Art Imaging of Acute Stroke

Stroke is a leading cause of mortality and morbidity in the developed world. The goals of an imaging evaluation for acute stroke are to establish a diagnosis as early as possible and to obtain accurate information about the intracranial vasculature and brain perfusion for guidance in selecting the appropriate therapy. A comprehensive evaluation may be performed with a combination of computed tomography (CT) or magnetic resonance (MR) imaging techniques. Unenhanced CT can be performed quickly, can help identify early signs of stroke, and can help rule out hemorrhage. CT angiography and CT perfusion imaging, respectively, can depict intravascular thrombi and salvageable tissue indicated by a penumbra. These examinations are easy to perform on most helical CT scanners and are increasingly used in stroke imaging protocols to decide whether intervention is necessary. While acute infarcts may be seen early on conventional MR images, diffusion-weighted MR imaging is more sensitive for detection of hyperacute ischemia. Gradient-echo MR sequences can be helpful for detecting a hemorrhage. The status of neck and intracranial vessels can be evaluated with MR angiography, and a mismatch between findings on diffusion and perfusion MR images may be used to predict the presence of a penumbra. The information obtained by combining various imaging techniques may help differentiate patients who do not need intravenous or intraarterial therapy from those who do, and may alter clinical outcomes. RSNA, 2006

https://pubs.rsna.org/doi/pdf/10.1148/rg.26si065501

State-of-the-Art Imag- ing of Acute Stroke 1

Objectives: This study aimed to describe the incidence and features of asymptomatic COVID-19 infections among HCWs at a tertiary hospital in Oman. Methods: This cross-sectional study was conducted between August 2020 and February 2021 among HCWs with no history of COVID-19 infection using an online questionnaire to collect sociodemographic and clinical data. COVID-19 infection was diagnosed using nasopharyngeal/throat swabs, which were tested for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Analyses were performed using Chi-squared test, Fisher’s exact test, or univariate ordinary least squares regression, as appropriate. Results: A total of 583 HCWs participated in the study. Most were female (56.6%) and the mean age was 35 ± 8 years . Only 9.6% (95% confidence interval [CI]: 7.3–12.3%) of the HCWs were at high exposure risk as they were directly involved in the care of COVID-19-infected patients. Overall, 4.1% (95% CI: 2.7–6.1%) of the HCWs screened positive for SARS-CoV-2; of these, five (20.8%) developed symptoms within two weeks. The frequency of SARS-CoV-2 positivity among HCWs working in high, intermediate, low, and miscellaneous risk areas was 1.8% (95% CI: <0.1–9.6%), 2.6% (95% CI: <0.1–6.5%), 5.3% (95% CI: 0.3–9.3%), and 4.8% (95% CI: <0.1–69.3%), respectively. Working in high-risk areas was associated with increased compliance with various infection control strategies (P <0.001). Conclusion: There was a greater frequency of SARS-CoV-2 positivity among HCWs working in lower-risk areas, whereas HCWs who worked in high-risk areas were significantly more likely to report increased compliance with infection control strategies. 
Keywords: SARS-CoV-2; COVID-19 Nucleic Acid Testing; Asymptomatic Infections; Health Personnel; Occupational Exposure; Infection Control; Real-Time Polymerase Chain Reaction; Oman.

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Identification of Asymptomatic Severe Acute Respiratory Syndrome Coronavirus 2 Infections among Healthcare Workers at Sultan Qaboos University Hospital, Oman

Faisal Al Azri

Papers

State-of-the-Art Imaging of Acute Stroke

State-of-the-Art Imag- ing of Acute Stroke 1

Identification of Asymptomatic Severe Acute Respiratory Syndrome Coronavirus 2 Infections among Healthcare Workers at Sultan Qaboos University Hospital, Oman