Multiphase MR Angiography Collateral Map: Functional Outcome after Acute Anterior Circulation Ischemic Stroke

Abstract

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

Collateral estimation by susceptibility-weighted imaging and prediction of functional outcomes after acute anterior circulation ischemic stroke

“…‡ The data are the medians, with interquartile ranges in parentheses. § The collateral grades of the MRA collateral map were the collateral grades estimated by the MR acute ischemic collateral (MAC) score of the multiphase MRA collateral map derived from dynamic contrast-enhanced MRA 24 , 25 . ǁ A favorable functional outcome was defined as a modified Rankin scale (mRS) score of less than or equal to 2, and an unfavorable functional outcome was defined as an mRS score of greater than 2 at day 90.…”

“…This secondary analysis used published data obtained from a prospective observational study in patients with acute ischemic stroke due to occlusion or stenosis of the unilateral internal carotid artery (ICA) and/or M1 segment of the middle cerebral artery (MCA) who were evaluated within 8 h of symptom onset. The details of the study population and imaging methods have been described previously 24 , 25 . Participants were evaluated for demographic data, medical history, vascular risk factors, routine blood tests, brain imaging, and cardiological tests.…”

“…The acquisition parameters were the same as those used in a previous study 24 . An experienced neuroradiologist (J.W.C with 14 years of experience), who was blinded to all clinical and other imaging data, measured the infarct volume (in milliliters) by using Medical Image Processing, Analysis, and Visualization (MIPAV, version 7.1.1; National Institutes of Health, Bethesda, MD) 25 . By using source data from dynamic contrast-enhanced MR angiography, 3-dimensional rotational arteriography was performed to determine the arterial status, and a multiphase MR angiography collateral map was reconstructed to evaluate the collateral-perfusion status.…”

“…Based on previous studies 30 , 31 , 33 , 35 , a collateral grading system was defined according to the scores of the prominent cortical and/or medullary veins as follows: good, intermediate, poor, and very poor (Table 1 ). The collateral-perfusion grading system of the multiphase MR angiography collateral map was defined by using the MR acute ischemic stroke collateral (MAC) scores as follows: 5, excellent; 4, good; 3, intermediate to good; 2, intermediate to poor; 1, poor; and 0, very poor 24 , 25 . We compared the collateral grades determined by SWI with the MAC scores of the multiphase MR angiography collateral map.…”

“…Collateral estimation is being considered increasingly important to precisely select eligible patients for IVT and IAT. Recently, useful collateral imaging methods using contrast material have been introduced, and they have shown prognostic value in acute cerebral ischemia due to large-vessel occlusion 22 – 25 . However, a noncontrast imaging method for collateral estimation is necessary with consideration of contrast-induced complications which can lead to irreversible kidney damage and an increased risk of morbidity and mortality, especially for patients with chronic kidney disease, which is a major risk factor for postcontrast acute kidney injury 26 – 28 .…”