Six-Minute Magnetic Resonance Imaging Protocol for Evaluation of Acute Ischemic Stroke

Background and Purpose—

If magnetic resonance imaging (MRI) is to compete with computed tomography for evaluation of patients with acute ischemic stroke, there is a need for further improvements in acquisition speed.

Methods—

Inclusion criteria for this prospective, single institutional study were symptoms of acute ischemic stroke within 24 hours onset, National Institutes of Health Stroke Scale ≥3, and absence of MRI contraindications. A combination of echo-planar imaging (EPI) and a parallel acquisition technique were used on a 3T magnetic resonance (MR) scanner to accelerate the acquisition time. Image analysis was performed independently by 2 neuroradiologists.

Results—

A total of 62 patients met inclusion criteria. A repeat MRI scan was performed in 22 patients resulting in a total of 84 MRIs available for analysis. Diagnostic image quality was achieved in 100% of diffusion-weighted imaging, 100% EPI-fluid attenuation inversion recovery imaging, 98% EPI-gradient recalled echo, 90% neck MR angiography and 96% of brain MR angiography, and 94% of dynamic susceptibility contrast perfusion scans with interobserver agreements ( k ) ranging from 0.64 to 0.84. Fifty-nine patients (95%) had acute infarction. There was good interobserver agreement for EPI-fluid attenuation inversion recovery imaging findings ( k =0.78; 95% confidence interval, 0.66–0.87) and for detection of mismatch classification using dynamic susceptibility contrast-Tmax ( k =0.92; 95% confidence interval, 0.87–0.94). Thirteen acute intracranial hemorrhages were detected on EPI-gradient recalled echo by both observers. A total of 68 and 72 segmental arterial stenoses were detected on contrast-enhanced MR angiography of the neck and brain with k =0.93, 95% confidence interval, 0.84 to 0.96 and 0.87, 95% confidence interval, 0.80 to 0.90, respectively.

Conclusions—

A 6-minute multimodal MR protocol with good diagnostic quality is feasible for the evaluation of patients with acute ischemic stroke and can result in significant reduction in scan time rivaling that of the multimodal computed tomographic protocol.

Combined low-dose contrast-enhanced MR angiography and perfusion for acute ischemic stroke at 3T: A more efficient stroke protocol

BACKGROUND AND PURPOSE

There is need to improve image acquisition speed for MR imaging in evaluation of patients with acute ischemic stroke. The purpose of this study was to evaluate the feasibility of a 3T MR stroke protocol that combines low-dose contrast-enhanced MRA and dynamic susceptibility contrast perfusion, without additional contrast.

METHODS

Thirty patients with acute stroke who underwent 3T MR imaging followed by DSA were retrospectively enrolled. TOF-MRA of the neck and brain and 3D contrast-enhanced MRA of the craniocervical arteries were obtained. A total of 0.1 mmol/kg of gadolinium was used for both contrast-enhanced MRA (0.05 mmol/kg) and dynamic susceptibility contrast perfusion (0.05 mmol/kg) (referred to as half-dose). An age-matched control stroke population underwent TOF-MRA and full-dose (0.1 mmol/kg) dynamic susceptibility contrast perfusion. The cervicocranial arteries were divided into 25 segments. Degree of arterial stenosis on contrast-enhanced MRA and TOF-MRA was compared with DSA. Time-to-maximum maps (>6 seconds) were evaluated for image quality and hypoperfusion. Quantitative analysis of arterial input function curves, SNR, and maximum T2* effects were compared between half- and full-dose groups.

RESULTS

The intermodality agreements (k) for arterial stenosis were 0.89 for DSA/contrast-enhanced MRA and 0.63 for DSA/TOF-MRA. Detection specificity of >50% arterial stenosis was lower for TOF-MRA (89%) versus contrast-enhanced MRA (97%) as the result of overestimation of 10% (39/410) of segments by TOF-MRA. The DWI-perfusion mismatch was identified in both groups with high interobserver agreement (r = 1). There was no significant difference between full width at half maximum of the arterial input function curves (P = .14) or the SNR values (0.6) between the half-dose and full-dose groups.

CONCLUSIONS

In patients with acute stroke, combined low-dose contrast-enhanced MRA and dynamic susceptibility contrast perfusion at 3T is feasible and results in significant scan time and contrast dose reductions.

Abstract 117: A Six Minute MRI Protocol for Evaluation of Acute Ischemic Stroke: Pushing the Boundaries

Purpose: Multimodal cerebrovascular CT and MR can now provide information about tissue viability, site of occlusion, and collateral status in patients with acute ischemic stroke (AIS). If MRI is to compete with CT for evaluation of AIS, there is need for further improvements in acquisition speed. The purpose of this study was to establish the feasibility of a fast MR protocol with a 6 minute acquisition time for evaluation of AIS.

Methods: Patients with suspicion of AIS and absence of MRI contraindications were prospectively enrolled. A combination of echo-planar imaging (EPI) and parallel acquisition technique were used on a 3T MR scanner to accelerate the acquisition time. The imaging protocol included: DWI (1 min), EPI-FLAIR (52 sec), EPI-GRE (50 sec), contrast-enhanced MR angiography (CE-MRA) of the entire supra-aortic arteries (20 sec), and DSC perfusion (2 min). Using a modified 2-phase contrast injection scheme, high spatial resolution CE-MRA of the supra-aortic arteries was performed just before DSC perfusion without the need for additional contrast. Image analysis was performed independently by two neuroradiologists and interobserver agreement was calculated using Kappa test.

Results: A total of 50 patients were included. Diagnostic image quality was achieved in 100% of DWI, 96% EPI-FLAIR, 98% EPI-GRE, 90% neck MRA, 96% of brain MRA, and 94% of DSC perfusion scans. Thirty eight patients (76%) had acute infarction. Using Tmax perfusion maps and applying DEFUSE criteria, 42% of patients had perfusion-diffusion mismatch with interobserver agreement of k=0.90. The mean of the signal-intensity-ratio values of the infarction on EPI-FLAIR was 1.08 for patients presenting < 4.5 hours (n=16) and 1.35 for patients presenting > 4.5 hours (n=22) from the time of imaging. Three patients had evidence of intracranial hemorrhage detected on EPI-GRE and confirmed by non-contrast CT. CE-MRA showed 27 segmental stenoses of the extra-cranial arteries and 24 segmental stenoses of the intracranial arteries with interobserver agreement of k= 0.82 and 0.74 respectively.

Conclusion: Described multimodal MR protocol is feasible for evaluation of patients with AIS and can result in significant reduction in scan time rivaling that of the multimodal CT protocol.

Role of EPI-FLAIR in patients with acute stroke: a comparative analysis with FLAIR

BACKGROUND AND PURPOSE

Further improvement in acquisition speed is needed, if MR imaging is to compete with CT for evaluation of patients with acute ischemic stroke. The purpose of this study was to evaluate the feasibility of implementing an echo-planar fluid-attenuated inversion recovery (EPI-FLAIR) sequence into an acute MR stroke protocol with potential reduction in scan time and to compare the results with conventional FLAIR images.

MATERIALS AND METHODS

Fifty-two patients (28 men and 24 women; age range, 32-96 years) with acute ischemic stroke were prospectively evaluated with an acute stroke MR protocol, which included both conventional FLAIR and EPI-FLAIR imaging with integration of parallel acquisition. The image acquisition time was 52 seconds for EPI-FLAIR and 3 minutes for conventional FLAIR. FLAIR and EPI-FLAIR studies were assessed by 2 observers independently for image quality and conspicuity of hyperintensity in correlation with DWI and were rated as concordant or discordant. Coregistered FLAIR and EPI-FLAIR images were evaluated for signal intensity ratio of the DWI-positive lesion to contralateral normal white matter.

RESULTS

An estimated 96% of all FLAIR and EPI-FLAIR studies were rated of diagnostic image quality by both observers, with interobserver agreements of κ = 0.82 and κ = 0.63 for FLAIR and EPI-FLAIR, respectively. In 36 (95%) of 38 patients with acute infarction, FLAIR and EPI-FLAIR were rated concordant regarding DWI lesion. The mean ± standard deviation of the signal intensity ratio values on EPI-FLAIR and FLAIR for DWI-positive lesions were 1.28 ± 0.16 and 1.25 ± 0.17, respectively (P = .47), and demonstrated significant correlation (r = 0.899, z value = 8.677, P < .0001).

CONCLUSIONS

In patients with acute stroke, EPI-FLAIR is feasible with comparable qualitative and quantitative results to conventional FLAIR and results in reduced acquisition time.

Quantitative analysis of hypoperfusion in acute stroke: arterial spin labeling versus dynamic susceptibility contrast

BACKGROUND AND PURPOSE

This study compares the concordance between arterial spin labeling (ASL) and dynamic susceptibility contrast (DSC) for the identification of regional hypoperfusion and diffusion-perfusion mismatch tissue classification using a quantitative method.

METHODS

The inclusion criteria for this retrospective study were as follows: patients with acute ischemic syndrome with symptom onset <24 hours and acquisition of both ASL and DSC MR perfusion. The volumes of infarction and hypoperfused lesions were calculated on ASL and DSC multi-parametric maps. Patients were classified into reperfused, matched, or mismatch groups using time to maximum >6 sec as the reference. In a subset of patients who were successfully recanalized, the identical analysis was performed and the infarction and hypoperfused lesion volumes were used for paired pre- and posttreatment comparisons.

RESULTS

Forty-one patients met our inclusion criteria. Twenty patients underwent successful endovascular revascularization (TICI>2a), resulting in a total of 61 ASL-DSC data pairs for comparison. The hypoperfusion volume on ASL-cerebral blood flow best approximated the DSC-time to peak volume (r=0.83) in pretreatment group and time to maximum (r=0.46) after recanalization. Both ASL-cerebral blood flow and DSC-TTP overestimated the hypoperfusion volume compared with time to maximum volume in pretreatment (F=27.41, P<0.0001) and recanalized patients (F=8.78, P<0.0001).

CONCLUSIONS

ASL-cerebral blood flow overestimates the DSC time to maximum hypoperfusion volume and mismatch classification in patients with acute ischemic syndrome. Continued overestimation of hypoperfused volume after recanalization suggests flow pattern and velocity changes in addition to arterial transit delay can affects the performance of ASL.

Periprocedural arterial spin labeling and dynamic susceptibility contrast perfusion in detection of cerebral blood flow in patients with acute ischemic syndrome

BACKGROUND AND PURPOSE

To compare the diagnostic performance of arterial spin-labeling (ASL) and dynamic susceptibility contrast (DSC) perfusion in detecting cerebral blood flow (CBF) changes before and after endovascular recanalization in acute ischemic syndrome.

METHODS

The inclusion criteria for this retrospective study were patients with acute ischemic syndrome who underwent endovascular recanalization and acquisition of both ASL and DSC before and after revascularization. ASL-CBF and multiparametric DSC maps were evaluated for image quality, location, and type of perfusion abnormality. Relative CBF (rCBF) was calculated in the infarction core and hypoperfused areas using coregistered ASL and DSC. Core and hypoperfused rCBF were used for paired pretreatment and posttreatment comparisons. Interobserver and intermodality agreement were evaluated by κ test, and t test was calculated for ASL and DSC rCBF values.

RESULTS

Twenty-five patients met our inclusion criteria. Five studies were rated nondiagnostic, resulting in 45 pairs of DSC-ASL available for comparison. ASL and DSC agreed on type and location of the perfusion abnormality in 71% and 80% of cases, respectively. The image quality of ASL was lower than DSC, resulting in interobserver variability for the type (κ=0.45) and location (κ=0.56) of perfusion abnormality. ASL was unable to show any type of perfusion abnormality in 11% of patients. In successfully recanalized patients, hyperperfusion (rCBF >1) was detected in 100% on DSC and 47% on ASL.

CONCLUSIONS

ASL is less sensitive than DSC for detecting rCBF changes in patients with acute ischemic syndrome, particularly with respect to hyperperfusion after successful recanalization.

Abstract TP55: Comparison of Arterial Spin Labeling and Dynamic Susceptibility Contrast Perfusion for Quantitative Evaluation of Mismatch in Successfully Recanalized Acute Stroke Patients

Purpose: Arterial spin labeling (ASL) has gained attention in evaluation of acute stroke as an alternative perfusion method that does not require contrast. We evaluate the agreement of ASL and dynamic susceptibility contrast (DSC) mismatch classification using a quantitative method in successfully recanalized patients.

Methods: This retrospective study was performed using MR examinations acquired between 2010-2012. Inclusion criteria were: patients with acute stroke who underwent successful recanalization and acquisition of both ASL and DSC before and after revascularization. The volumes of DWI and hypoperfused (Tmax > 6 seconds) lesions were calculated on DSC using an automated software. The hypoperfusion volumes on ASL were calculated using a region of interest-based analysis. The ratios of volume of the hypoperfusion region to DWI lesion were calculated and used to classify the patients into 3 categories: 1) mismatch: ratio >2; 2) matched: 0.7 < ratio < 2; and 3) reperfused: ratio < 0.7. Intermodality agreement for mismatch categories was evaluated with Kappa test.

Results: Seventeen patients met the inclusion criteria, resulting in 34 pair of ASL-DSC for comparison. The mean ± SD of the volumes of the DWI lesions was 14.2± 8 ml and 18.2 ± 13 ml before and after revascularization respectively. ASL overestimated the hypoperfusion volume in both pre and post-treatment groups (p<0.01) in comparison to DSC-Tmax lesion volume. In pre-treatment group, ASL-DWI and DSC-DWI mismatch categories agreed in 15 of 17 cases (88%) with high agreement (k=0.82; 95% CI, 0.3 -0.87). In post-treatment group, ASL-DWI and DSC-DWI mismatch categories agreed in 11 of 17 cases (64%) with moderate agreement (k=0.46; 95% CI,0.25-0.82). Out of 6 discrepant cases, three reperfused patients on DSC were categorized matched on ASL and 3 matched cases on DSC were classified as mismatch on ASL.

Conclusion: ASL overestimates the DSC time to maximum lesion volume. There is only moderate agreement between ASL and DSC in mismatch classification of revascularized patients, suggestive of less sensitivity of ASL in detection of reperfusion. Improvement in ASL methods with varying degree post-labeling delay may be needed for evaluation of revascularized patients.

Abstract WP41: Peri-Procedural Arterial Spin Labeling and Dynamic Susceptibility contrast Perfusion in Detection of Cerebral Blood Flow in Patients with Acute Ischemic Syndrome

Purpose: To investigate the potential clinical value and diagnostic performance of arterial spin-labeled (ASL) and dynamic susceptibility contrast (DSC) perfusion in detection of cerebral blood flow (CBF) changes before and after endovascular recanalization in patients with acute ischemic syndrome (AIS).

Methods: This retrospective study was performed using MR examinations between 2010-2012. Inclusion criteria were: patients with AIS who underwent endovascular recanalization and acquisition of both ASL and DSC before and after revascularization. ASL CBF and multiparametric DSC perfusion maps were qualitatively evaluated for image quality, presence of hypo or hyperperfusion and location of perfusion abnormality. Lesion segmentation for infarct core (ADCb >550) and hypoperfused area (TMax > 4 sec) was performed on DSC. rCBF was calculated using a regions-of-interest (ROI) method in the infarction core and hypoperfused areas using coregistered ASL and DSC images. Core and hypoperfused rCBF ROI’s were used for paired pre- and post-treatment intermodality comparisons. Interobserver and intermodality agreement was evaluated by Kappa test. T-test and Spearman correlation coefficients were calculated for ASL and DSC rCBF values.

Results: Twenty-five patients were met our inclusion criteria. Five studies were rated non-diagnostic, resulting in a total of 45 pair of DSC-ASL for comparison. ASL and DSC agreed on type of perfusion abnormality in 32 of 45 cases (71%) and location of the perfusion abnormality in 36 of 45 cases (80%). The image quality of ASL was lower than DSC, resulting in interobserver variability for the type (k =0.45) and location (k=0.56) of perfusion abnormality. ASL was unable to show any type of perfusion abnormality in 11% of patients. In patients with successful recanalization, hyperperfusion (rCBF> 1) was detected in 100% on DSC and 47% on ASL. ASL showed prolonged arterial transit effects in 58% of successfully recanalized patients.

Conclusion: ASL is moderately consistent with DSC for detection of cerebral blood flow changes in patients with AIS. Qualitative and quantitative differences exist between two modalities, in particular in respect to detection of hyperperfusion in successfully recanalized patients.

The healing effect of arnebia euchroma in second degree burn wounds in rat as an animal model

BACKGROUND

Finding more efficient agents with fewer side effects for treatment of burns has always been a concern for researchers. Silver sulfadiazine (SSD), apparently due to its antimicrobial effect, is still one of the most common prescribed agents. Previous studies suggested that Arnebia euchroma (AE) has shown antimicrobial and anti-inflammatory activities. This study investigates the healing effect of AE extract in comparison with SSD in second degree burn wounds.

METHODS

Fort eight female Wistar rats (220±20 g) were divided into four groups. Standard second degree burn wounds were induced on the back of their necks. One group was treated with SSD; two groups were treated with AE cream at concentrations of 10% (AE10) and 20% (AE20) and the control group which received no treatment. The duration of treatment was 28 days.

RESULTS

This study revealed that AE and SSD noticeably improved re-epithelization, fibroblasts proliferation, and collagen bundle synthesis and had a noticeable anti-inflammatory effect compared with the control group.

CONCLUSION

Results of the present study revealed that Arnebia euchroma herbal extract was an effective treatment for second degree burn wounds when compared with SSD.

Bilateral renal lymphangiomatosis: sonographic findings

Renal lymphangiomatosis is an exceedingly rare disorder characterized by developmental malformation of the lymphatic system surrounding the kidneys. We report a case of bilateral renal lymphangiomatosis in a 21-year-old man who underwent abdominal sonographic examination that revealed numerous cystic areas of various sizes around both kidneys with extension along the renal hilum. Subsequent abdominal CT examination demonstrated bilateral, multilocular, fluid-filled cystic masses with thin walls in the perirenal and peripelvic region. MRI of the patient revealed bilaterally enlarged kidneys with multiple hyperintense lesions in both perirenal spaces and the peripelvic area on T2-weighted images. These cystic spaces appeared hypointense on T1-weighted images with no enhancement in postcontrast images. The diagnosis of renal lymphangiomatosis was made based on typical imaging findings.

Diagnostic value of contrast-enhanced fluid-attenuated inversion-recovery and delayed contrast-enhanced brain MRI in multiple sclerosis

RATIONALE AND OBJECTIVES

In brain MRI of multiple sclerosis (MS) patients, enhancement of the lesions is usually evaluated in early contrast-enhanced T1-weighted images (CE-T1WI). The objective of this study is to determine the sensitivity of contrast-enhanced fluid-attenuated-inversion-recovery (CE-FLAIR) and delayed contrast-enhanced MRI in evaluation of MS brain lesions.

MATERIALS AND METHODS

Brain MRI examination including early and delayed CE-T1WI and early and delayed CE-FLAIR images was performed for 46 patients with clinically definite MS disease. Number, size, location, degree, and pattern of enhancement of the enhanced lesions in each sequence were recorded separately.

RESULTS

A total number of 87 enhanced lesions was detected in 30 patients. Early CE-T1WI could detect only 63 lesions (72.4% of total) in 24 patients, while delayed CE-T1WI and early and delayed CE-FLAIR images showed 85 (97.7%), 84 (96.6%), and 81 (93.1%) lesions in 28, 28, and 26 patients, respectively. A greater degree of enhancement and larger lesion size were observed in the additional sequences compared with the early CE-T1WI.

CONCLUSIONS

The sensitivity of early CE-T1WI for the detection of enhanced MS lesions is significantly lower than that for other additional sequences. Delayed CE-FLAIR images could not add significant information to other sequences. Therefore, early CE-FLAIR and delayed CE-T1WI brain MRI can be considered as part of the evaluation of MS patients, especially if, despite clinically suspected active disease, no enhanced lesion is found in the routine CE-T1WI.

Methanol poisoning: acute MR and CT findings in nine patients

INTRODUCTION

Methanol poisoning is an uncommon but potent central nervous system toxin. We describe here the CT and MR findings in nine patients following an outbreak of methanol poisoning.

METHODS

Five patients with a typical clinical presentation and elevated anion and osmolar gaps underwent conventional brain MRI with a 1.5-T Gyroscan Interna scanner. In addition nonenhanced CT was performed in another three patients with more severe toxicity.

RESULTS

Bilateral hemorrhagic or nonhemorrhagic necrosis of the putamina, diffuse white matter necrosis, and subarachnoid hemorrhage were among the radiological findings. Various patterns of enhancement of basal ganglial lesions were found including no enhancement, strong enhancement and rim enhancement.

CONCLUSION

A good knowledge of the radiological findings in methanol poisoning seems to be necessary for radiologists. The present study is unique in that it enables us to include in a single report most of the radiological findings that have been reported previously.