Diffusion and perfusion MR imaging in acute ischemic stroke: a comparison to SPECT

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.

Comparative study of MR mTI-ASL and DSC-PWI in evaluating cerebral hemodynamics of patients with Moyamoya disease

The aim of this study was to explore the correlation between multi-inversion time arterial spin labeling (mTI-ASL) and dynamic susceptibility contrast-enhanced perfusion weighted imaging (DSC-PWI) in assessment of hemodynamics of patients with Moyamoya disease (MMD).In this study, 24 MMD patients and 21 healthy subjects were enrolled between June 2017 and December 2017. The images of mTI-ASL and DSC-PWI in the week before revascularization surgery were retrospectively analyzed. The parameters of cerebral blood flow (CBF), time to peak (TTP), and bolus arrival time (BAT) were measured in regions of interest (ROIs) of lateral middle cerebral artery (MCA) territories, basal ganglia (BG), and cerebellum, and relative perfusion parameters (rCBF-ASL, rBAT-ASL, rCBF-DSC, and rTTP-DSC) were calculated by dividing by cerebellum value. One-way analysis of variance and Student-Newman-Keuls tests were performed to compare rCBF-ASL and rCBF-DSC in the MMD group and the control group. Unpaired t test was used to compare rBAT-ASL and rTTP-DSC in the MMD group and the control group. And we assessed the correlation between rCBF-ASL and rCBF-DSC and between rBAT-ASL and rTTP-DSC using Pearson correlation analysis.All the relative parameters were significantly different between the MMD group and the control group (all P<.05). Meanwhile, there was significant difference between rCBF-ASL and rCBF-DSC (P<.05), and there was strong correlation between rCBF-ASL and rCBF-DSC (r = 0.839, P<.001), and moderate correlation between rBAT-ASL and rTTP-DSC (r = 0.519, P<.001).Both mTI-ASL and DSC-PWI could be used to assess perfusion state in MMD patients before revascularization surgery effectively. As a noninvasive imaging technique, mTI-ASL could provide perfusion parameters without contrast medium injection, and the results were quite correlative with DSC-PWI.

Evidence-based guideline: The role of diffusion and perfusion MRI for the diagnosis of acute ischemic stroke: report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology

OBJECTIVE

To assess the evidence for the use of diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI) in the diagnosis of patients with acute ischemic stroke.

METHODS

We systematically analyzed the literature from 1966 to January 2008 to address the diagnostic and prognostic value of DWI and PWI.

RESULTS AND RECOMMENDATIONS

DWI is established as useful and should be considered more useful than noncontrast CT for the diagnosis of acute ischemic stroke within 12 hours of symptom onset. DWI should be performed for the most accurate diagnosis of acute ischemic stroke (Level A); however, the sensitivity of DWI for the diagnosis of ischemic stroke in a general sample of patients with possible acute stroke is not perfect. The diagnostic accuracy of DWI in evaluating cerebral hemorrhage is outside the scope of this guideline. On the basis of Class II and III evidence, baseline DWI volumes probably predict baseline stroke severity in anterior territory stroke (Level B) but possibly do not in vertebrobasilar artery territory stroke (Level C). Baseline DWI lesion volumes probably predict (final) infarct volumes (Level B) and possibly predict early and late clinical outcome measures (Level C). Baseline PWI volumes predict to a lesser degree the baseline stroke severity compared with DWI (Level C). There is insufficient evidence to support or refute the value of PWI in diagnosing acute ischemic stroke (Level U).

Correlation of magnetic resonance imaging findings with hexamethylpropyleneamine oxime brain single photon emission computed tomography in ischemic stroke patients in the subacute stage

PURPOSE

To evaluate the correlation between magnetic resonance imaging (MRI) findings and 99mTc-hexamethylpropyleneamine oxime (HMPAO) brain single photon emission computed tomography (SPECT) during the subacute stage in ischemic stroke patients.

MATERIAL AND METHODS

The T1 and T2-weighted images and brain SPECT findings of 84 patients (mean age 60.69 +/- 12.47 years) with subacute cerebral ischemia during the period 1998-2004 were reviewed. All HMPAO SPECT and MRI studies were performed between 3 and 7 days (mean time delay 4.76 +/- 1.29 days) after the onset of stroke symptoms.

RESULTS

An ischemic lesion was seen both in T1 and T2-weighted images with perfusion defects above 60% (severe defect) according to count/pixel data of the lesion in HMPAO SPECT studies in 30 (90.9%) of 33 patients. Otherwise, the ischemic lesion was seen only on T2-weighted images with perfusion defects between 30% and 60% (moderate defect) in HMPAO SPECT studies in 25 (89.3%) of 28 patients. In 20 (87%) of 23 patients who had perfusion defects below 30% (mild defect) on HMPAO SPECT, only non-specific findings such as cerebral atrophy and/or periventricular ischemic-gliotic lesions could be seen in MRI. The difference between these ratios was statistically significant (P < 0.01).

CONCLUSION

Brain 99mTc-HMPAO SPECT findings indicate good correlation with MRI findings. When the ischemic lesions could be seen in both T1 and T2-weighted images, the patients frequently had severe perfusion defects. When only seen in T2-weighted images, the perfusion defect was moderate. When only non-specific findings were revealed by MRI, only mild perfusion defects were found by SPECT.

Dynamic susceptibility contrast perfusion imaging of cerebral ischemia in nonhuman primates: Comparison of Gd-DTPA and NMS60

PURPOSE

To study a new gadolinium (Gd) contrast agent-NMS60-for MR perfusion-weighted imaging (PWI) of brain tissue.

MATERIALS AND METHODS

NMS60 is a Gd3+ trimer with a molecular weight of 2158 Daltons, and a T2 relaxivity almost three times higher than that of Gd-DTPA. Middle cerebral artery (MCA) occlusion was induced in nine nonhuman primates. The animals were scanned acutely and for up to six follow-up time points. PWI peak, and time-to-peak maps were generated, and perfusion deficit volumes were measured from these maps. The values of peak, time-to-peak, and perfusion deficit volume were compared between NMS60 and GD-DTPA.

RESULTS

These results demonstrate that there was no significant difference in our calculated perfusion parameters between the two contrast agents.

CONCLUSION

The two agents were found to be equally effective for PWI for acute and chronic stroke in primates. Along with its previously demonstrated advantage for T1-enhanced imaging, the current results show that NMS60 is a viable contrast agent for use in stroke patients.

Cerebral perfusion imaging using contrast-enhanced MRI

New developments in fast magnetic resonance imaging (MRI) have enabled imaging of cerebral haemodynamics. This article describes the theory behind perfusion imaging and provides an overview of the most commonly used MRI technique. Limitations of this technique are described, and the potential clinical applications are discussed, with particular attention to the role of perfusion imaging in the context of stroke and brain tumour.

Neuroimaging, the ischaemic penumbra, and selection of patients for acute stroke therapy

Advances in neuroimaging have been central to the expansion of knowledge in the neurosciences over the past 20 years. One of the most important roles of brain imaging is in the selection of patients for acute stroke therapy. Currently, computed tomography (CT) is commonly used to select patients who have had strokes for thrombolytic therapy on the basis of the absence of haemorrhage and, more controversially, the presence of early CT changes of ischaemia. Since patients with ischaemic penumbra are more likely than those without to respond to therapy, identification of patients with this feature will become increasingly important. Although several imaging modalities can identify the penumbra, the most practical is magnetic resonance imaging (MRI) showing perfusion-weighted and diffusion-weighted imaging mismatch. Although uncertainties in image interpretation remain, surrogate MRI outcome measures are becoming an important component of translational research. Future developments in imaging technologies may provide other opportunities for surrogate outcome studies.