ED MRI: Safety, Consent, and Regulatory Considerations

MRI is a vital examination in the emergency department, especially in patients with stroke, spinal cord compression, cardiovascular emergencies, appendicitis, and trauma. It is important to consider its underlying safety hazards because of its strong magnetic and radio frequency fields. Multiple resources are available to guide radiology departments on the safe functioning of an MRI site. Four-zone site layout, MR compatibility labeling, MR personnel training, detailed screening process, access control, and appropriate implementation of safety policies and procedures are all necessary to maintain a safe and hazard-free MR environment.

Clinical Imaging of the Penumbra in Ischemic Stroke: From the Concept to the Era of Mechanical Thrombectomy

The ischemic penumbra is defined as the severely hypoperfused, functionally impaired, at-risk but not yet infarcted tissue that will be progressively recruited into the infarct core. Early reperfusion aims to save the ischemic penumbra by preventing infarct core expansion and is the mainstay of acute ischemic stroke therapy. Intravenous thrombolysis and mechanical thrombectomy for selected patients with large vessel occlusion has been shown to improve functional outcome. Given the varying speed of infarct core progression among individuals, a therapeutic window tailored to each patient has recently been proposed. Recent studies have demonstrated that reperfusion therapies are beneficial in patients with a persistent ischemic penumbra, beyond conventional time windows. As a result, mapping the penumbra has become crucial in emergency settings for guiding personalized therapy. The penumbra was first characterized as an area with a reduced cerebral blood flow, increased oxygen extraction fraction and preserved cerebral metabolic rate of oxygen using positron emission tomography (PET) with radiolabeled O₂. Because this imaging method is not feasible in an acute clinical setting, the magnetic resonance imaging (MRI) mismatch between perfusion-weighted imaging and diffusion-weighted imaging, as well as computed tomography perfusion have been proposed as surrogate markers to identify the penumbra in acute ischemic stroke patients. Transversal studies comparing PET and MRI or using longitudinal assessment of a limited sample of patients have been used to define perfusion thresholds. However, in the era of mechanical thrombectomy, these thresholds are debatable. Using various MRI methods, the original penumbra definition has recently gained a significant interest. The aim of this review is to provide an overview of the evolution of the ischemic penumbra imaging methods, including their respective strengths and limitations, as well as to map the current intellectual structure of the field using bibliometric analysis and explore future directions.

Comparison of magnetic resonance imaging versus computed tomography-based thrombolysis treatment in patients with acute ischemic stroke

PURPOSE

To evaluate the efficacy and safety of magnetic resonance imaging (MRI)-based comparing with computed tomography (CT)-based selection for intravenous thrombolysis in patients with acute ischemic stroke (AIS).

METHODS

Totally 462 consecutive AIS patients treated with intravenous thrombolysis within a 4.5 h window from Jan. 2016 to Dec. 2019 were enrolled. The primary endpoint was the good functional outcome defined by a modified Rankin Scale (mRS) of 0-2 at 3 months. Secondary outcomes include the excellent functional outcome defined by a mRS of 0-1 at 3 months, occurrences of symptomatic intracranial hemorrhage (SICH), 7-day mortality, and 3-month mortality.

RESULTS

Overall 172 patients received MRI and 290 received CT before they were treated with thrombolysis. The difference in the good or excellent functional outcome was not statistically significant between MRI and CT groups (both P > 0.05). The incidences of 7-day mortality (3.5% vs. 8.6%, P < 0.01), 30-day mortality (12.8% vs. 21.0%, P = 0.03), and SICH (12.2% vs. 20.3%, P < 0.01) were obviously lower for MRI-based regimen compared with CT-based regimen. Multivariate logistic regression indicated that MRI-based regimen was significantly associated with a lower risk of 7-day mortality (OR = 0.72, 95% CI: 0.53-0.91; P < 0.01), 30-day mortality (OR = 0.58, 95% CI: 0.47-0.73; P < 0.01), and SICH (OR = 0.44, 95% CI: 0.20-0.65; P < 0.01) after controlling for potential confounding factors.

CONCLUSION

Despite MRI-based thrombolysis was not demonstrated to be associated with the good functional outcome, it significantly reduced risks of mortality and SICH in patients with AIS compared with CT-based thrombolysis.

Patients With Acute Ischemic Stroke Who Receive Brain Magnetic Resonance Imaging Demonstrate Favorable In-Hospital Outcomes

Background

Use of inpatient brain magnetic resonance imaging (MRI) in patients with acute ischemic stroke is highly institution dependent and has been associated with increased length and cost of hospital stay. We examined whether inpatient brain MRI in patients with acute ischemic stroke is associated with improved clinical outcomes to justify its resource requirements.

Methods and Results

The National Inpatient Sample database was queried retrospectively to find 94 003 patients who were admitted for acute ischemic stroke and then received inpatient brain MRI between 2012 and 2014. Multivariable regression analysis was performed with respect to a control group to assess for differences in the rates of inpatient mortality and complications, as well as the length and cost of hospital stay based on brain MRI use. Inpatient brain MRI was independently associated with lower rates of inpatient mortality (1.67% versus 3.09%; adjusted odds ratio [OR], 0.60; 95% CI, 0.53–0.68; P<0.001), gastrostomy (2.28% versus 2.89%; adjusted OR, 0.82; 95% CI, 0.73–0.93; P<0.001), and mechanical ventilation (1.97% versus 2.82%; adjusted OR, 0.68; 95% CI, 0.60–0.77; P<0.001). Brain MRI was independently associated with ≈0.32 days (8%) and $1131 (11%) increase in the total length (P<0.001) and cost (P<0.001) of hospital stay, respectively.

Conclusions

Inpatient brain MRI in patients with acute ischemic stroke is associated with substantial decrease in the rates of inpatient mortality and complications, at the expense of marginally increased length and cost of hospitalization.

Phased changes in strategies can reduce delay of intravenous thrombolysis administration to 15 min

OBJECTIVES

The present study aimed to determine whether phased changes in strategies including the Helsinki model affect the delay of intravenous thrombolysis (IVT) using tissue plasminogen activator (tPA) to treat acute ischemic stroke.

METHOD

We retrospectively studied 516 consecutive patients treated with IVT in our department between October 2005 and December 2018. We implemented a system of hospital pre-notification in 2005, when IVT was initially implemented at our center. We then improved the IVT strategy by simplifying brain imaging (July 2011), premixing tPA (April 2014), locating a blood cell counter in the emergency room (June 2015), manually administering a tPA bolus before preparing a continuous infusion (January 2016), awarding a prize to members of the acute stroke team (November 2016), and completing registration before arrival and sending patients directly to computed tomography (February 2017). We analyzed the effects of these strategic changes on annual median door-to-needle times (DTN).

RESULTS

The DTN was annually reduced, from a median of 90 [interquartile range, 55-98] minutes in 2006 to 15 [12-24.25] minutes in 2017. By 2017, 94% of patients were treated within 60 min of arrival. Multivariate logistic regression analysis revealed that initial NIHSS score ≤ 4 (OR 2.67, 95% CI 1.3-5.7) and anticoagulation before onset (OR 6.00, 95% CI 2.47-14.58) were independently associated with 20 min or more of DTN in 186 patients treated from 2016 to 2018.

CONCLUSIONS

Phased strategic change to reduce the delay in delivering IVT reduced median DTN to 15 min at a single Japanese stroke center.

Hyperintense Vessels, Collateralization, and Functional Outcome in Patients With Stroke Receiving Endovascular Treatment

Background and Purpose—

Fluid-attenuated inversion recovery hyperintense vessels (FHV) are frequently observed on magnetic resonance imaging in acute stroke patients with proximal vessel occlusion. Whether FHV can serve as a surrogate for the collateral status and predict functional outcome of patients is still a matter of debate.

Methods—

Acute ischemic stroke patients with M1-middle cerebral artery occlusion who received magnetic resonance imaging before endovascular treatment in 3 hospitals in Germany between January 2007 and June 2016 were eligible. Quantification of FHV was performed using an FHV–Alberta Stroke Program Early CT Score (ASPECTS) rating system. Functional outcome was evaluated with the modified Rankin Scale 3 months after stroke. Collateral status of patients was graded on baseline angiography using the American Society of Interventional and Therapeutic Neuroradiology grading system. Odds for good outcome (modified Rankin Scale score, 0–2) were determined using logistic regression analyses.

Results—

Overall, 116 patients were analyzed (median age, 74; interquartile range [IQR], 64–79; median National Institutes of Health Stroke Scale, 14; IQR, 10–19). The median FHV-ASPECTS was 2 (IQR, 1–3). Good collateral status (American Society of Interventional and Therapeutic Neuroradiology grade 3–4) on angiography was more frequently observed in patients with FHV-ASPECTS ≤2 (83% versus 57%; P =0.025). Patients with an FHV-ASPECTS ≤2 had a better functional outcome after 3 months (median modified Rankin Scale score, 2; IQR, 0–5), compared with patients with an FHV-ASPECTS >2 (median modified Rankin Scale score, 4; IQR, 3–6; P =0.015). In multiple regression analyses, FHV-ASPECTS ≤2 was independently associated with good functional outcome (adjusted odds ratio, 5.3; 95% confidence interval, 1.5–18.2).

Conclusions—

Low FHV-ASPECTS is associated with both better collateral status and better 3-month functional outcome in acute stroke patients with M1 vessel occlusion.

A systemized stroke code significantly reduced time intervals for using intravenous tissue plasminogen activator under magnetic resonance imaging screening

BACKGROUND

A stroke code can shorten time intervals until intravenous tissue plasminogen activator (IV t-PA) treatment in acute ischemic stroke (AIS). Recently, several reports demonstrated that magnetic resonance imaging (MRI)-based thrombolysis had reduced complications and improved outcomes in AIS despite longer processing compared with computed tomography (CT)-based thrombolysis.

METHODS

In January 2009, we implemented CODE RED, a computerized stroke code, at our hospital with the aim of achieving rapid stroke assessment and treatment. We included patients with thrombolysis from January 2007 to December 2008 (prestroke code period) and from January 2009 to May 2013 (poststroke code period). The IV t-PA time intervals and 90-day modified Rankin Scale (mRS) scores were collected.

RESULTS

During the observation period, 252 patients used IV t-PA under the CODE RED (MRI based: 208; CT based: 44). The remaining 71 patients (MRI based: 53; CT based: 18) received it before the implementation of our stroke code. After implementation of CODE RED, door-to-image time, door-to-needle time, and the onset-to-needle time were significantly reduced by 11, 18, and 22 minutes in MRI-based thrombolysis. Particularly, the proportion of favorable outcome (mRS score 0-2) was significantly increased (from 41.5% to 60.1%, P = .02) in poststroke than in prestroke code period in MRI-based thrombolysis. However, in ordinal regression, the presence of stroke code showed just a trend for favorable outcome (odds ratio, .99-2.87; P = .059) at 90 days of using IV t-PA after correction of age, sex, and National Institutes of Health Stroke Scale.

CONCLUSIONS

In this study, we demonstrated that a systemized stroke code shortened time intervals for using IV t-PA under MRI screening. Also, our results showed a possibility that a systemized stroke code might enhance the efficacy of MRI-based thrombolysis. In the future, we need to carry out a more detailed prospective study about this notion.

Number of Cerebral Microbleeds and Risk of Intracerebral Hemorrhage After Intravenous Thrombolysis

Background and Purpose—

Cerebral microbleeds (CMBs) are found in a substantial proportion of patients with ischemic stroke eligible for treatment with intravenous thrombolysis. Until now, there is limited data on the impact of multiple CMBs on occurrence of intracerebral hemorrhage (ICH) after intravenous thrombolysis.

Methods—

Between 2008 and 2013, all patients receiving MRI-based intravenous thrombolysis were identified within our prospective thrombolysis register. Number of CMBs was rated on pretreatment T2*-weighted MRI by a rater blinded to clinical data and follow-up. Outcomes of interest were occurrence of symptomatic ICH (sICH) and parenchymal hemorrhage (PH).

Results—

Among 326 included patients, 52 patients had a single CMB (16.0%), 19 had 2 to 4 CMBs (5.8%), and 10 had ≥5 CMBs (3.1%). Frequency of sICH/PH was 1.2%/5.7% in patients without CMBs, 3.8%/3.8% in patients with a single CMB, 10.5%/21.1% in patients with 2 to 4 CMBs, and 30.0%/30.0% in patients with ≥5 CMBs, respectively (each P for trend <0.01). The unadjusted odds ratio per additional CMB for sICH was 1.19 (95% confidence interval, 1.07–1.33; P <0.01) and for PH was 1.13 (95% confidence interval, 1.03–1.24; P =0.01). Compared with patients without CMBs, both patients with 2 to 4 CMBs ( P =0.02/ P =0.02) and patients with ≥5 CMBs ( P <0.01/ P <0.01) had significantly increased odds ratios for sICH and PH, whereas in patients with a single CMB, odds ratios were not significantly increased ( P =0.21/ P =0.59). The association of CMB burden with sICH/PH remained significant after adjustment for possible confounders (age, age-related white matter changes score, atrial fibrillation, onset-to-treatment time, prior statin use, and systolic blood pressure on admission).

Conclusions—

Our findings indicate a higher risk of sICH and PH after intravenous thrombolysis when multiple CMBs are present, with a graded relationship to increasing baseline CMB number.

Safety of Thrombolysis in Patients With Acute Ischemic Stroke and Cerebral Cavernous Malformations

Background and Purpose—

Data on safety of intravenous thrombolysis with recombinant tissue-type plasminogen activator for acute ischemic stroke in patients with coexisting cerebral cavernous malformations (CCMs) are scarce. We assessed the risk of thrombolysis-associated hemorrhage in these patients.

Methods—

We searched our tertiary care hospital thrombolysis register for patients with CCM confirmed by MRI (3 T, Siemens, TimTrio) before thrombolysis for acute ischemic stroke. CCMs were graded into subtypes according to the Zabramski classification on the basis of their MRI appearance. The primary end point was symptomatic intracerebral hemorrhage according to European Cooperative Acute Stroke Study III (ECASS III) criteria. The secondary end point was any parenchymal hemorrhage.

Results—

In a total of 350 patients (median age, 76 years; interquartile range, 68–84; median National Institutes of Health Stroke Scale score, 8; interquartile range, 5–14; 51.4% women), CCMs were found in 9 patients (2.6%). Seven patients had a single CCM, and 2 patients had multiple CCMs with a total number of 12 CCMs in all patients. The subtype of CCMs was type III in 9 cases and type I in 3 cases. Symptomatic intracerebral hemorrhage occurred in 1 of 9 patients with CCM versus 11 of 341 patients without CCM ( P =0.27). Parenchymal hemorrhage occurred in 2 of 9 patients with CCM versus 27 of 341 patients ( P =0.17) without CCM.

Conclusions—

Given the limitations of our study (mainly low number of patients with CCM), the risk of thrombolysis-associated hemorrhage in patients with CCM remains uncertain. Although our data do not suggest an increased hazard from thrombolysis in patients with CCM, larger studies are necessary to determine definitively the influence of CCMs on parenchymal hemorrhage and symptomatic intracerebral hemorrhage.

MRI before intraarterial therapy in ischemic stroke: feasibility, impact, and safety

Intraarterial therapy (IAT) in acute ischemic stroke is effective for opening occlusions of major extracranial or intracranial vessels. Clinical efficacy data are lacking pointing to a need for proper patient selection. We examined feasibility, clinical impact, and safety profile of magnetic resonance imaging (MRI) for patient selection before IAT. In this single-center study, we collected epidemiologic, imaging, and outcome data on all intraarterial-treated patients presenting with anterior circulation occlusions at our center from 2004 to 2011. Magnetic resonance imaging was the first imaging choice. Computer tomography (CT) was performed in the presence of a contraindication. We treated 138 patients. Mean age was 64 years and median National Institutes of Health Stroke Scale (NIHSS) was 17. Major reperfusion (thrombolysis in cerebral infarction (TICI) 2b+3) was achieved in 52% and good outcome defined as modified Rankin Scale (mRS) score 0 to 2 at 90 days was achieved in 41%. Mortality at 90 days was 10%. There was only one symptomatic hemorrhage. Recanalization, age, and stroke severity were associated with outcome. Preprocedure MRI was obtained in 83%. Good outcome was significantly associated with smaller diffusion-weighted imaging (DWI) lesion size at presentation and not with the size of the perfusion lesion. It is feasible to triage patients for IAT using MRI with acceptable rates of poor outcome and symptomatic hemorrhage.

Magnetic resonance imaging and computed tomography utilization trends in an academic ED

OBJECTIVE

The objective of this study is to examine the annual utilization trends of emergency department (ED)-ordered magnetic resonance imaging (MRI) and computed tomography (CT) at an urban academic hospital from 2007 to 2011. We hypothesized that MRI and CT use would increase annually over the study period.

METHODS

This was a retrospective observational study of ED encounters between January 1, 2007, and December 31, 2011. All patients seen by a provider were identified, and demographics were abstracted. Type of CT and/or MRI examination, clinical indication, and final disposition were collected. Records of patients with an ED-ordered MRI were also examined for presence of a CT within ±3 days of their encounter date. Unadjusted linear regression was used to assess for differences among years for both CT and MRI. Secondary outcomes were descriptively summarized.

RESULTS

A total of 7089 MRI (20 per 1000) and 85,673 CT (243 per 1000) examinations were ordered over a 60-month period. Computed tomography use decreased significantly (P=.021). Magnetic resonance imaging use significantly increased (2.2 per 1000 ED visits each year, P=.005). Magnetic resonance imaging of the head was ordered most frequently (10.7 per 1000). The overwhelming majority of MRI images were completed for acute neurologic/behavioral problem. Of patients with an MRI completed, 89.4% had a CT completed within 3 calendar days with most of the CT examinations (81%) completed during the encounter.

CONCLUSION

There was a steady increase in MRI testing in our academic ED, with most MRIs ordered for acute neurologic or behavioral changes. There was a corresponding decreasing trend for CT scans.