Cost-Effectiveness of CT, CTA, MRI, and Specialized MRI for Evaluation of Patients Presenting to the Emergency Department With Dizziness

Detectability of acute ischemic stroke with thin (3 mm) axial versus thin (3 mm) coronal diffusion-weighted imaging in patients presenting to the emergency department with acute dizziness

BACKGROUND AND PURPOSE

Ischemic strokes can cause vertigo, particularly when involving the posterior circulation of the brain. Prior research has suggested that thin-section (3 mm) axial or coronal DWI may improve the detection of ischemic stroke compared to thick (5 mm) DWI. However, relative sensitivity of differing thin DWI sequences is unknown. In this retrospective cohort study, we compare the sensitivity of thin coronal DWI and thin axial DWI in detection of brain ischemia.

MATERIALS AND METHODS

Retrospective study at a single institution (2/18/2020-8/31/2023) of patients who presented to the emergency department with vertigo/dizziness and underwent an abbreviated MRI protocol (3 mm axial DWI, 3 mm coronal DWI, axial FLAIR, and axial SWI). For each case with an ischemic lesion, the visibility of infarct on thin axial and coronal DWIs was rated; location and size were also recorded. Visibility on either sequence was considered the reference standard. Sensitivity was compared with McNemar's test.

RESULTS

615 abbreviated MRI examinations were performed; 24/615 (3.9%) had an ischemic lesion (15 cerebral, 7 brainstem, 13 cerebellar). 24 of these MRI examinations with ischemic lesions were performed using 3 mm axial MRI and on 3T MRI. All lesions (24/24) were visible on thin axial DWI (100% sensitivity, 95% CI: 0.95-1.00). Fewer lesions (20/24) were seen on thin coronal DWI (83% sensitivity, 95% CI: 0.72-0.91). The difference in sensitivity was statistically significant (p = 0.0374). Lesions not visible on coronal DWI were 2-8 mm in size, the largest in the middle cerebellar peduncle.

CONCLUSIONS

Thin coronal DWI may not improve additional diagnostic utility beyond thin axial DWI for the detection of ischemia in patients with dizziness. When designing protocols tailored for stroke detection (particularly in the posterior circulation), replacing conventional (5 mm) DWI with thin (3 mm) axial DWI may be preferable to adding a thin coronal sequence.

A 3-Minute Ultrafast MRI and MRA Protocol for Screening of Acute Ischemic Stroke

OBJECTIVE

To evaluate the diagnostic performance of a 3-min ultrafast brain MRI and MRA protocol for screening of acute ischemic stroke.

METHODS

This study involved 67 adult patients who underwent ultrafast and reference MRI and MRA scans from September 2023 to June 2024 for stroke evaluation. Two readers independently assessed the ultrafast and reference MRI and MRA images in a masked and randomized manner for acute and chronic infarct and hemorrhage as well as large-vessel occlusion and severe stenosis. A 3-point Likert scale was used to evaluate diagnostic quality of the ultrafast sequences and Cohen's κ was used to assess interrater agreement.

RESULTS

The ultrafast MRI and MRA protocol showed high diagnostic quality, with 98% of sequences rated as diagnostic. Raters showed perfect agreement in identifying acute infarcts, aneurysms, and vascular occlusions using both ultrafast and reference protocols and near-perfect agreement (>95%) for detecting acute hemorrhage and severe stenosis. For chronic conditions such as chronic infarction and chronic hemorrhage, there was substantial agreement with κ values ranging from 0.73 to 0.76.

DISCUSSION

The screening ultrafast MRI and MRA protocol can effectively identify acute ischemic stroke and intracranial large-vessel occlusion with high diagnostic accuracy while significantly reducing acquisition time, making it suitable for initial stroke triage. Evaluation for chronic pathologies on the ultrafast protocol is inferior compared with standard MRI and MRA imaging.

NeuroMix with MRA: A Fast MR Protocol to Reduce Head and Neck CTA for Patients with Acute Neurologic Presentations

BACKGROUND AND PURPOSE

Overuse of CT-based cerebrovascular imaging in the emergency department and inpatient settings, notably CTA of the head and neck for minor and nonfocal neurologic presentations, stresses imaging services and exposes patients to radiation and contrast. Furthermore, such CT-based imaging is often insufficient for definitive diagnosis, necessitating additional MR imaging. Recent advances in fast MRI may allow timely assessment and a reduced need for head and neck CTA in select populations.

MATERIALS AND METHODS

We identified inpatients or patients in the emergency department who underwent CTAHN (including noncontrast and postcontrast head CT, with or without CTP imaging) followed within 24 hours by a 3T MRI study that included a 2.5-minute unenhanced multicontrast sequence (NeuroMix) and a 5-minute intracranial time of flight MRA) during a 9-month period (April to December 2022). Cases were classified by 4 radiologists in consensus as to whether NeuroMix and NeuroMix + MRA detected equivalent findings, detected unique findings, or missed findings relative to CTAHN.

RESULTS

One hundred seventy-four cases (mean age, 67 [SD, 16] years; 56% female) met the inclusion criteria. NeuroMix alone and NeuroMix + MRA protocols were determined to be equivalent or better compared with CTAHN in 71% and 95% of patients, respectively. NeuroMix always provided equivalent or better assessment of the brain parenchyma, with unique findings on NeuroMix and NeuroMix + MRA in 35% and 36% of cases, respectively, most commonly acute infarction or multiple microhemorrhages. In 8/174 cases (5%), CTAHN identified vascular abnormalities not seen on the NeuroMix + MRA protocol due to the wider coverage of the cervical arteries by CTAHN.

CONCLUSIONS

A fast MR imaging protocol consisting of NeuroMix + MRA provided equivalent or better information compared with CTAHN in 95% of cases in our population of patients with an acute neurologic presentation. The findings provide a deeper understanding of the benefits and challenges of a fast unenhanced MR-first approach with NeuroMix + MRA, which could be used to design prospective trials in select patient groups, with the potential to reduce radiation dose, mitigate adverse contrast-related patient and environmental effects, and lessen the burden on radiologists and health care systems.

Abbreviated MRI in the evaluation of dizziness: report turnaround times and impact on length of stay compared to CT, CTA, and conventional MRI

PURPOSE

Neuroimaging is often used in the emergency department (ED) to evaluate for posterior circulation strokes in patients with dizziness, commonly with CT/CTA due to speed and availability. Although MRI offers more sensitive evaluation, it is less commonly used, in part due to slower turnaround times. We assess the potential for abbreviated MRI to improve reporting times and impact on length of stay (LOS) compared to conventional MRI (as well as CT/CTA) in the evaluation of acute dizziness.

MATERIALS AND METHODS

We performed a retrospective analysis of length of stay via LASSO regression for patients presenting to the ED with dizziness and discharged directly from the ED over 4 years (1/1/2018-12/31/2021), controlling for numerous patient-level and logistical factors. We additionally assessed turnaround time between order and final report for various imaging modalities.

RESULTS

14,204 patients were included in our analysis. Turnaround time for abbreviated MRI was significantly lower than for conventional MRI (4.40 h vs. 6.14 h, p < 0.001) with decreased impact on LOS (0.58 h vs. 2.02 h). Abbreviated MRI studies had longer turnaround time (4.40 h vs. 1.41 h, p < 0.001) and was associated with greater impact on ED LOS than non-contrast CT head (0.58 h vs. 0.00 h), however there was no significant difference in turnaround time compared to CTA head and neck (4.40 h vs. 3.86 h, p = 0.06) with similar effect on LOS (0.58 h vs. 0.53 h). Ordering both CTA and conventional MRI was associated with a greater-than-linear increase in LOS (additional 0.37 h); the same trend was not seen combining CTA and abbreviated MRI (additional 0.00 h).

CONCLUSIONS

In the acute settings where MRI is available, abbreviated MRI protocols may improve turnaround times and LOS compared to conventional MRI protocols. Since recent guidelines recommend MRI over CT in the evaluation of dizziness, implementation of abbreviated MRI protocols has the potential to facilitate rapid access to preferred imaging, while minimizing impact on ED workflows.

Imaging Outcomes of Emergency MR Imaging in Dizziness and Vertigo: A Retrospective Cohort Study

BACKGROUND AND PURPOSE

Patients exhibiting acute dizziness or vertigo often represent a diagnostic challenge, and many undergo neuroimaging for stroke detection. We aimed to demonstrate the imaging outcomes of first-line emergency MR imaging among patients with acute dizziness or vertigo and to determine the clinical risk factors for stroke and other acute pathology.

MATERIALS AND METHODS

This retrospective study included consecutive patients with acute dizziness or vertigo referred for emergency MR imaging in a tertiary hospital during 5 years. We recorded and analyzed patient characteristics, relevant clinical information, and imaging outcomes. Risk score models were derived to predict which patients were more likely to present with positive MR imaging findings.

RESULTS

A total of 1169 patients were included. Acute stroke was found in 17%; other clinically significant pathology, in 8% of patients. In 75% of the patients, emergency MR imaging showed no significant abnormalities. Risk factors for acute stroke included older age, male sex, and a prevalence of cardiovascular risk factors and neurologic signs. Isolated dizziness had no discriminative power on imaging outcomes, and 14% of these patients showed acute stroke. Risk scores had only moderate performance in predicting acute ischemic stroke (receiver operating characteristic area under curve = 0.75) or any significant pathology (receiver operating characteristic area under curve = 0.70).

CONCLUSIONS

Acute dizziness and vertigo remain challenging even when emergency MR imaging is readily available. One in 4 patients had acute pathology on MR imaging. Predictors for acute pathology (older age, male sex, cardiovascular risk factors, and neurologic signs) may aid in patient selection for MR imaging, optimizing the yield and clinical impact of emergency neuroimaging. Low diagnostic yields of CT and internal acoustic canal MR imaging may offer an opportunity to reduce health care expenditures in the future.