Is improved access to magnetic resonance imaging imperative for optimal ischemic stroke care?

Neuroimaging, including CT and MRI, is integral to ischemic stroke (IS) treatment, management, and prevention. However, the use of MRI for IS patients is limited despite its potential to provide high-quality images that yield definitive information related to the management of IS. MRI is beneficial when the information provided by CT is insufficient for decisions related to the diagnosis, etiology, or treatment of IS. In the emergency setting, MRI can improve the diagnostic accuracy of CT-negative acute ischemic strokes (AIS) and ensure a better selection of patients for reperfusion therapies with thrombolysis and/or thrombectomy. Moreover, MR imaging may help avoid hospital admissions for patients with stroke mimics, facilitate earlier discharge, and reduce overall hospital costs. MRI in the in-patient setting can help determine stroke etiology to aid in stroke prevention management upon discharge. Furthermore, early access to MRI in IS out-patients can aid in diagnosing, risk stratifying, and determining optimal management strategies for patients with a TIA or a minor stroke. Recent technological advances, particularly low-to-mid-field MR scanners, can improve access to MRI. These MR scanners provide faster protocols, cost-effectiveness, smaller footprints, safety, and lower power requirements. In conclusion, MRI use for IS treatment, management, and prevention is imperative and justifiable, and the latest technological advancements in MR scanners hold the potential to enhance access.

Ischemic stroke segmentation in multi-sequence MRI by symmetry determined superpixel based hierarchical clustering

Automated estimation of ischemic stroke evolution across different brain anatomical regions has immense potential to revolutionize stroke treatment. Multi-sequence Magnetic Resonance Imaging (MRI) techniques provide information to characterize abnormal tissues based on their anatomy and physical properties. Asymmetry of the right and left hemispheres of the brain is an important cue for abnormality estimation but using it alone is susceptible to occasional error due to self-asymmetry of the brain. A precise estimate of the symmetry axis is therefore essential for accurate asymmetry identification, which holds the key to the proposed method. The proposed symmetry determined superpixel based hierarchical clustering (SSHC) method initially estimates the lesion from inter-hemispheric asymmetry. This asymmetry further determines the thresholding parameter for hierarchically clustering the superpixels leading to an automated and accurate lesion delineation. A multi-sequence MRI based pipeline also combines the estimations from individual sequences. SSHC is evaluated on different sequences of the Loma Linda University (LLU) dataset with 26 patients and the Ischemic Stroke Lesion Segmentation (ISLES'15) dataset with 28 patients. SSHC eliminates the need for manual determination of threshold for combining the superpixel clusters and is more reliable as it derives the information from the quick estimation of asymmetry. SSHC outperforms the state-of-the-art resulting in a high Dice similarity score of 0.704±0.27 and a recall of 0.85±0.01 which are 6% and 35% respectively higher than the challenge winning method. SSHC thus demonstrates a promising potential in the automated detection of (sub-)acute adult ischemic stroke.

Systematic review with network meta-analysis: Diagnostic values of ultrasonography, computed tomography, and magnetic resonance imaging in patients with ischemic stroke

BACKGROUND AND OBJECTIVE

Ischemic stroke is a foremost cause for disability and death worldwide. This study is conducted in order to compare the diagnostic values between transcranial Doppler ultrasound (ultrasonography), computed tomography (CT), and magnetic resonance imaging (MRI) in patients suffering from ischemic stroke by performing a network meta-analysis.

METHODS

We made use of Cochrane Library, PubMed, and Embase in order to obtain literature and papers. The combination analysis of both direct and indirect evidence in terms of sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy was conducted so as to assess the odds ratios (ORs) and surface under the cumulative ranking curve (SUCRA) values of the seven different imaging methods. These imaging techniques include ultrasonography, computed tomography (traditional CT, computed tomography angiography [CTA], computed tomography perfusion [CTP]), and MRI (traditional MRI, diffusion-weighted imaging [DWI], magnetic resonance angiography), in order to properly diagnose ischemic stroke patients.

RESULTS

Thirteen eligible diagnostic trials were enrolled into this network meta-analysis. The results of the traditional meta-analysis showed that among CT methods, CTP showed higher sensitivity, NPV, and accuracy; among MRI methods, DWI had relatively higher sensitivity, NPV, and accuracy. The results of network meta-analysis showed that DWI had relatively higher sensitivity, NPV, and accuracy when compared with traditional CT, CTA, magnetic resonance angiography and traditional MRI. CTP showed higher SUCRA among CT methods while DWI showed higher SUCRA among MRI methods. A cluster analysis revealed that DWI had the highest diagnostic value in terms of sensitivity, PPV, NPV, and accuracy amongst the aforementioned seven imaging techniques.

CONCLUSION

This network meta-analysis provides supporting evidence to the idea that DWI has a higher diagnostic value regarding ischemic stroke among MRI methods, and CTP has a poor diagnostic value among CT methods, which provide therapeutic considerations for Ischemic stroke intervention.

Role of Diffusion-weighted Imaging in Acute Stroke Management using Low-field Magnetic Resonance Imaging in Resource-limited Settings

A variety of imaging modalities exist for the diagnosis of stroke. Several studies have been carried out to ascertain their contribution to the management of acute stroke and to compare the benefits and limitations of each modality. Diffusion-weighted imaging (DWI) has been described as the optimal imaging technique for diagnosing acute ischemic stroke, yet limited evidence is available on the value of DWI in the management of ischemic stroke with low-field magnetic resonance (MR) systems. Although high-field MR imaging (MRI) is desirable for DWI, low-field scanners provide an acceptable clinical compromise which is of importance to developing countries posed with the challenge of limited availability of high-field units. The purpose of this paper was to systematically review the literature on the usefulness of DWI in acute stroke management with low-field MRI scanners and present the experience in Nigeria.

Metabolic changes in acute cerebral infarction: Findings from proton magnetic resonance spectroscopic imaging

The purpose of this study was to investigate the clinical role of proton magnetic resonance spectroscopy (¹H-MRS) in the diagnosis of acute cerebral infarction. Using databases available at the Fifth Affiliated Hospital of Zhengzhou University (Zhengzhou, China), the medical records of 47 patients with acute cerebral infarction treated between April 2010 and March 2012 were retrospectively reviewed. The patients underwent routine magnetic resonance imaging (MRI), diffusion-weighted imaging (DWI) and multiple-voxel ¹H-MRS examination within 12 h after the onset of stroke. The patients then received normal medical treatment for 2 weeks and underwent follow-up ¹H-MRS examination at 1–2 months after stroke. The concentrations of the main metabolites [N-acetylaspartic acid (NAA), creatine (Cr), choline (Cho) and lactate (Lac)] in the infarct center, the infarction border region and the contralateral brain areas (control) were analyzed. The 47 patients experienced changes in NAA, Cho and Lac levels at different stages after stroke. In the infarction center, the NAA/Cr and NAA/Cho ratios decreased, while the Lac/Cr ratio increased within 12 h compared with those in the contralateral side. Within 6–12 h after stroke, the Lac/Cr ratio increased and the NAA/Cho ratio decreased compared with those <6 h after stroke. During the 1–2 months post-stroke, significant reductions in the NAA/Cr, NAA/Cho, Cho/Cr and Lac/Cr ratios were observed in the infarction center. In the infarction border region, the Lac/Cr ratio increased significantly at 12 h and decreased during the 1–2 months after stroke. The NAA/Cr, NAA/Cho and Cho/Cr ratios were significantly increased in the infarction border regions of patients who received thrombolytic therapy for 1–2 months compared with those in patients who did not undergo thrombolysis. Our results highlight the usefulness of ¹H-MRS-based metabolomics as a feasible and efficient prognostic tool for assessing the treatment effect of acute cerebral infarction.

Automatic MDCT injectors: hygiene and efficiency of disposable, prefilled, and multidosing roller pump systems in clinical routine

OBJECTIVE

This study evaluated three different injection systems with regard to microbiological contamination, time efficiency, and user handling during a clinical routine.

SUBJECTS AND METHODS

A total of 825 patients were included. A double-syringe contrast injector with disposable syringes (system A; n = 150) and one that used prefilled syringes (system B; n = 150) were microbiologically analyzed during single use of the syringes in one patient. Moreover, the contamination of a roller pump injector capable of multidosing several patients from a contrast agent container, without the need for prior filling, was determined after being used for an entire day (system C; n = 35 injections/day for 15 days). The hygienic background was guaranteed by taking imprints of the surfaces of devices and the palms of the hands of members of CT staff before the clinical investigation. The time required for assembly of the injection systems and for filling or refilling of each injector system was measured. The handling of the three systems also was subjectively ranked by the technicians.

RESULTS

Injection systems A, B, and C remained microbiologically sterile and free of contamination throughout their use in clinical routine. The mean (± SD) time for injection system assembly and installation of syringes and filling did not differ significantly between injection systems A and B (system A, 2.5 ± 1.1 minutes; system B, 1.9 ± 1.3 minutes; p = 0.12), whereas the time for assembly of system C was significantly shorter (0.9 ± 0.6 minutes; p < 0.05 vs system A; p < 0.05 vs system B). In the subjective ranking of injector handling, systems B and C were preferred.

CONCLUSION

Double-syringe injectors used with disposable or prefilled contrast agent syringes, as well as roller pump injectors, ensure hygienic conditions in clinical routine. However, time efficiency and handling are aspects that favor prefilled and roller pump systems.