BACKGROUND AND PURPOSE: Assessment of the collateral status has been emphasized for appropriate treatment decisions in patients with acute ischemic stroke. The purpose of this study was to introduce a multiphase MRA collateral imaging method (collateral map) derived from time-resolved dynamic contrast-enhanced MRA and to verify the value of the multiphase MRA collateral map in acute ischemic stroke by comparing it with the multiphase collateral imaging method (MRP collateral map) derived from dynamic susceptibility contrast-enhanced MR perfusion. MATERIALS AND METHODS:From a prospectively maintained registry of acute ischemic stroke, MR imaging data of patients with acute ischemic stroke caused by steno-occlusive lesions of the unilateral ICA and/or the M1 segment of the MCA were analyzed. We generated collateral maps using dynamic signals from dynamic contrast-enhanced MRA and DSC-MRP using a Matlab-based in-house program and graded the collateral scores of the multiphase MRA collateral map and the MRP collateral map independently. Interobserver reliabilities and intermethod agreement between both collateral maps for collateral grading were tested. RESULTS:Seventy-one paired multiphase MRA and MRP collateral maps from 67 patients were analyzed. The interobserver reliabilities for collateral grading using multiphase MRA or MRP collateral maps were excellent (weighted ϭ 0.964 and 0.956, respectively). The agreement between both collateral maps was also excellent (weighted ϭ 0.884; 95% confidence interval, 0.819 -0.949). CONCLUSIONS:We demonstrated that the dynamic signals of dynamic contrast-enhanced MRA could be used to generate multiphase collateral images and showed the possibility of the multiphase MRA collateral map as a useful collateral imaging method in acute ischemic stroke. ABBREVIATIONS:AIS ϭ acute ischemic stroke; DCE-MRA ϭ dynamic contrast-enhanced MRA; DSC-MRP ϭ dynamic susceptibility contrast-enhanced MR perfusion; mMRA ϭ multiphase MRA; MRP ϭ MR perfusion T he cerebral collaterals are alternative vascular channels for maintaining blood perfusion to the ischemic brain distal to an arterial occlusion. The collateral status varies among patients with Indicates open access to non-subscribers at www.ajnr.org http://dx.

I n cerebral ischemia due to large-vessel occlusion, cell viability depends on the collateral perfusion status (1,2). Infarction might be complete in less than 1 hour or may not be complete for hours or days depending on the collateral perfusion status, which varies among patients (3,4). Therefore, recanalization and reperfusion treatment can be futile or even dangerous when performed in the standard optimal time window, but could be useful if performed in a later time window (5)(6)(7)(8). Studies have shown that a large ischemic core combined with poor collaterals is a strong predictor of an unfavorable response to endovascular treatment and poor functional outcomes. Hence, the exclusion of patients with a large ischemic core and poor collateral circulation could prevent administration of futile and dangerous recanalization therapy. Conversely, good collateral circulation can limit ischemic core expansion and prolong the time the penumbral tissue at risk remains salvageable until reperfusion therapy. Some studies have suggested that the time window for endovascular treatment can be successfully extended in patients with good collaterals (9-14). These results demonstrate the importance of accurately estimating the collateral perfusion status to enable patientspecific application of treatment, thereby improving functional outcomes among patients with acute ischemic stroke due to large-vessel occlusion.Recently, researchers have developed dynamic collateral imaging methods such as multiphase CT angiography and collateral flow maps derived from dynamic susceptibility contrast material-enhanced perfusion MRI (15,16). Studies evaluating these collateral imaging approaches have shown that collateral status is a strong predictor of final infarct size and functional outcomes in patients considered eligible for intra-arterial thrombectomy and intravenous thrombolysis (17,18). For intra-arterial thrombectomy, it

To determine the value of susceptibility-weighted imaging (SWI) for collateral estimation and for predicting functional outcomes after acute ischemic stroke. To identify independent predictors of favorable functional outcomes, age, sex, risk factors, baseline National Institutes of Health Stroke Scale (NIHSS) score, baseline diffusion-weighted imaging (DWI) lesion volume, site of steno-occlusion, SWI collateral grade, mode of treatment, and successful reperfusion were evaluated by multiple logistic regression analyses. A total of 152 participants were evaluated. A younger age (adjusted odds ratio (aOR), 0.42; 95% confidence interval (CI) 0.34 to 0.77; P < 0.001), a lower baseline NIHSS score (aOR 0.90; 95% CI 0.82 to 0.98; P = 0.02), a smaller baseline DWI lesion volume (aOR 0.83; 95% CI 0.73 to 0.96; P = 0.01), an intermediate collateral grade (aOR 9.49; 95% CI 1.36 to 66.38; P = 0.02), a good collateral grade (aOR 6.22; 95% CI 1.16 to 33.24; P = 0.03), and successful reperfusion (aOR 5.84; 95% CI 2.08 to 16.42; P = 0.001) were independently associated with a favorable functional outcome. There was a linear association between the SWI collateral grades and functional outcome (P = 0.008). Collateral estimation using the prominent vessel sign on SWI is clinically reliable, as it has prognostic value.

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BackgroundTherapeutic approaches to brain metastases include surgery, whole-brain radiotherapy, stereotactic radiosurgery (SRS), and combination therapy. Recently, postoperative or preoperative SRS draws more attention to reduce postoperative recurrence in brain metastases. The goal of this study is to review surgical outcome of patients who had been treated by SRS, and to discuss the effectiveness of preoperative SRS.MethodsFrom 2009 to 2015, 174 patients were treated by SRS for brain metastases, and among these 50 patients underwent surgery. Eighteen patients underwent surgery after SRS, and 14 had oligometastases. The patients' median age at the time of surgery was 56 years (range, 34–84 years). The median follow-up duration was 16.5 months (range, 4–47 months). Pathological findings were classified as follows; radiation necrosis (Group I, n=3), mixed type (Group II, n=2), and tumor-dominant group (Group III, n=9). We compared surgical outcome in respect of steroid, mannitol dosage, Karnofsky performance scale, and pathological subgroups.ResultsThe median overall survival was 11 months (range, 2–40 months). Six, 12 and 24 months survival rate was 64.3, 42.9, and 28.6%, respectively. Improvement of Karnofsky performance score was achieved in 50% after surgery. The overall survival of Group I (26.6 months) was longer than the other groups (11.5 months). Additionally the patients were able to be weaned from medications, such as steroid administration after surgery was reduced in 10 cases, and mannitol dosage was reduced in 6 cases. Time interval within 3 months between SRS and surgery seemed to be related with better local control.ConclusionSurgical resection after radiologically and symptomatically progressed brain metastases previously treated with SRS seems to be effective in rapid symptom relief and provides an improvement in the quality of life. A short time interval between SRS and surgical resection seems to be associated with good local tumor control.