Role of diffusion and perfusion MRI in selecting patients for reperfusion therapies

Diagnostic accuracy of flat-panel computed tomography in assessing cerebral perfusion in comparison with perfusion computed tomography and perfusion magnetic resonance: a systematic review

Purpose

Flat-panel computed tomography (FP-CT) is increasingly available in angiographic rooms and hybrid OR’s. Considering its easy access, cerebral imaging using FP-CT is an appealing modality for intra-procedural applications. The purpose of this systematic review is to assess the diagnostic accuracy of FP-CT compared with perfusion computed tomography (CTP) and perfusion magnetic resonance (MRP) in cerebral perfusion imaging.

Methods

We performed a systematic literature search in the Cochrane Library, MEDLINE, Embase, and Web of Science up to June 2019 for studies directly comparing FP-CT with either CTP or MRP in vivo. Methodological quality was assessed using the QUADAS-2 tool. Data on diagnostic accuracy was extracted and pooled if possible.

Results

We found 11 studies comparing FP-CT with CTP and 5 studies comparing FP-CT with MRP. Most articles were pilot or feasibility studies, focusing on scanning and contrast protocols. All patients studied showed signs of cerebrovascular disease. Half of the studies were animal trials. Quality assessment showed unclear to high risks of bias and low concerns regarding applicability. Five studies reported on diagnostic accuracy; FP-CT shows good sensitivity (range 0.84–1.00) and moderate specificity (range 0.63–0.88) in detecting cerebral blood volume (CBV) lesions.

Conclusions

Even though FP-CT provides similar CBV values and reconstructed blood volume maps as CTP in cerebrovascular disease, additional studies are required in order to reliably compare its diagnostic accuracy with cerebral perfusion imaging.

Electronic supplementary material

The online version of this article (10.1007/s00234-019-02285-y) contains supplementary material, which is available to authorized users.

INCA (Peru) Study: Impact of Non-Invasive Cardiac Magnetic Resonance Assessment in the Developing World

Background Advanced cardiac imaging permits optimal targeting of cardiac treatment but needs to be faster, cheaper, and easier for global delivery. We aimed to pilot rapid cardiac magnetic resonance ( CMR ) with contrast in a developing nation, embedding it within clinical care along with training and mentoring. Methods and Results A cross-sectional study of CMR delivery and clinical impact assessment performed 2016-2017 in an upper middle-income country. An International partnership (clinicians in Peru and collaborators from the United Kingdom, United States, Brazil, and Colombia) developed and tested a 15-minute CMR protocol in the United Kingdom, for cardiac volumes, function and scar, and delivered it with reporting combined with training, education and mentoring in 2 centers in the capital city, Lima, Peru, 100 patients referred by local doctors from 6 centers. Management changes related to the CMR were reviewed at 12 months. One-hundred scans were conducted in 98 patients with no complications. Final diagnoses were cardiomyopathy (hypertrophic, 26%; dilated, 22%; ischemic, 15%) and 12 other pathologies including tumors, congenital heart disease, iron overload, amyloidosis, genetic syndromes, vasculitis, thrombi, and valve disease. Scan cost was $150 USD, and the average scan duration was 18±7 minutes. Findings impacted management in 56% of patients, including previously unsuspected diagnoses in 19% and therapeutic management changes in 37%. Conclusions Advanced cardiac diagnostics, here CMR with contrast, is possible using existing infrastructure in the developing world in 18 minutes for $150, resulting in important changes in patient care.

Dynamic Angiography and Perfusion Imaging Using Flat Detector CT in the Angiography Suite: A Pilot Study in Patients with Acute Middle Cerebral Artery Occlusions

BACKGROUND AND PURPOSE

Perfusion and angiographic imaging using intravenous contrast application to evaluate stroke patients is now technically feasible by flat detector CT performed by the angiographic system. The aim of this pilot study was to show the feasibility and qualitative comparability of a novel flat detector CT dynamic perfusion and angiographic imaging protocol in comparison with a multimodal stroke MR imaging protocol.

MATERIALS AND METHODS

In 12 patients with acute stroke, MR imaging and the novel flat detector CT protocol were performed before endovascular treatment. Perfusion parameter maps (MTT, TTP, CBV, CBF) and MIP/volume-rendering technique images obtained by using both modalities (MR imaging and flat detector CT) were compared.

RESULTS

Comparison of MIP/volume-rendering technique images demonstrated equivalent visibility of the occlusion site. Qualitative comparison of perfusion parameter maps by using ASPECTS revealed high Pearson correlation coefficients for parameters CBF, MTT, and TTP (0.95-0.98), while for CBV, the coefficient was lower (0.49).

CONCLUSIONS

We have shown the feasibility of a novel dynamic flat detector CT perfusion and angiographic protocol for the diagnosis and triage of patients with acute ischemic stroke. In a qualitative comparison, the parameter maps and MIP/volume-rendering technique images compared well with MR imaging. In our opinion, this flat detector CT application may substitute for multisection CT imaging in selected patients with acute stroke so that in the future, patients with acute stroke may be directly referred to the angiography suite, thereby avoiding transportation and saving time.

Intravenous fibrinolysis eligibility: a survey of stroke clinicians' practice patterns and review of the literature

BACKGROUND

The indications and contraindications for intravenous (IV) recombinant tissue plasminogen activator (rtPA) use in ischemic stroke can be confusing to the practicing neurologist. Here we seek to describe practice patterns regarding decision-making among US stroke clinicians.

METHODS

Stroke clinicians (attending and fellow) from the 8 National Institutes of Health SPOTRIAS (Specialized Programs of Translational Research in Acute Stroke) centers were asked to complete a survey ahead of the 2012 SPOTRIAS Investigators' meeting.

RESULTS

A total of 51 surveys were collected (71% response rate). Most of the responders were attending physicians (68%). Only 18% of clinicians reported strictly adhering to current American Heart Association guidelines for treatment within 3 hours from symptom onset; this increased to 51% for the European Cooperative Acute Stroke Study (ECASS) III criteria in the 3 to 4.5 hours time frame. All clinicians treat eligible patients in the 3 to 4.5 hours time frame. The great majority will recommend rtPA in the following scenarios: (1) elderly individuals irrespective of age (97%); (2) severe stroke irrespective of National Institutes of Health Stroke Scale (NIHSS) (95%); or (3) suspected stroke with seizures at symptom onset (91%). None recommended rtPA in the setting of an international normalized ratio >1.7. Most clinicians defined mild strokes as an exclusion based on the perceived disability of the deficit (80%) rather than on a specific NIHSS threshold.

CONCLUSIONS

Most surveyed stroke clinicians seem to find that the current IV rtPA eligibility criteria for the 3-hour time frame too restrictive. All would recommend rtPA to eligible patients in the 3 to 4.5 hours time frame despite the absence of an U.S. Food and Drug Administration (FDA)-approved indication.

Early diffusion-weighted imaging and perfusion-weighted imaging lesion volumes forecast final infarct size in DEFUSE 2

BACKGROUND AND PURPOSE

It is hypothesized that early diffusion-weighted imaging (DWI) lesions accurately estimate the size of the irreversibly injured core and thresholded perfusion-weighted imaging (PWI) lesions (time to maximum of tissue residue function [Tmax] >6 seconds) approximate the volume of critically hypoperfused tissue. With incomplete reperfusion, the union of baseline DWI and posttreatment PWI is hypothesized to predict infarct volume.

METHODS

This is a substudy of Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution Study 2 (DEFUSE 2); all patients with technically adequate MRI scans at 3 time points were included. Baseline DWI and early follow-up PWI lesion volumes were determined by the RAPID software program. Final infarct volumes were assessed with 5-day fluid-attenuated inversion recovery and were corrected for edema. Reperfusion was defined on the basis of the reduction in PWI lesion volume between baseline and early follow-up MRI. DWI and PWI volumes were correlated with final infarct volumes.

RESULTS

Seventy-three patients were eligible. Twenty-six patients with >90% reperfusion show a high correlation between early DWI volume and final infarct volume (r=0.95; P<0.001). Nine patients with <10% reperfusion have a high correlation between baseline PWI (Tmax >6 seconds) volume and final infarct volume (r=0.86; P=0.002). Using all 73 patients, the union of baseline DWI and early follow-up PWI is highly correlated with final infarct volume (r=0.94; P<0.001). The median absolute difference between observed and predicted final volumes is 15 mL (interquartile range, 5.5-30.2).

CONCLUSIONS

Baseline DWI and early follow-up PWI (Tmax >6 seconds) volumes provide a reasonable approximation of final infarct volume after endovascular therapy.

Advanced techniques using contrast media in neuroimaging

This article presents an overview of advanced magnetic resonance (MR) imaging techniques using contrast media in neuroimaging, focusing on T2*-weighted dynamic susceptibility contrast MR imaging and T1-weighted dynamic contrast-enhanced MR imaging. Image acquisition and data processing methods and their clinical application in brain tumors, stroke, dementia, and multiple sclerosis are discussed.

Validation of the Totaled Health Risks in Vascular Events (THRIVE) Score for Outcome Prediction in Endovascular Stroke Treatment

Background

We recently developed the Totaled Health Risks In Vascular Events (THRIVE) score to predict outcomes after endovascular stroke treatment. The THRIVE score, which incorporates age, National Institutes of Health Stroke Scale score, and three medical comorbidities (hypertension, diabetes mellitus, and atrial fibrillation), was developed using data from the Mechanical Embolus Removal in Cerebral Ischemia (MERCI) and Multi MERCI trials.

Aims

We set out to perform external validation of the THRIVE score using data from the largest registry of endovascular stroke treatment performed to date, the Merci Registry.

Methods

We compared the performance of the THRIVE score in two different data sets: the development cohort (the MERCI and Multi MERCI trials, n = 305) and a validation cohort (the Merci Registry, a prospective multicenter registry of patients undergoing endovascular stroke treatment, n = 1000). We examined the predictive utility of the THRIVE score across the range of clinical outcomes and used receiver–operator characteristics curve analysis to compare score performance in the two data sets.

Results

The THRIVE score predicted good outcome, death, and the full range of the modified Rankin Scale in a similar fashion between the MERCI trials and the Merci Registry. Receiver–operator characteristics curve comparisons showed no statistically significant difference in the performance of the THRIVE score between the two data sets: for good outcome, the receiver–operator characteristics area under the curve was 0.293 for the MERCI trials and 0.266 for the Merci Registry ( P = 0.47) and for death, the receiver–operator characteristics area under the curve was 0.692 for the MERCI trials and 0.717 for the Merci Registry ( P = 0.48). The THRIVE score and vessel recanalization were also found to be independent and unrelated predictors of clinical outcome.

Conclusions

The THRIVE score reliably predicts outcomes after endovascular stroke treatment and may be useful as a clinical prognostic tool and to perform severity adjustments in stroke clinical research.