Diffusion-weighted Imaging Reversal Research Articles

Abstract TP8: Apparent Diffusion Coefficientvalue Could Be The New Perspective To Ascertain Effectiveness Of Mechanical Thrombectomy In Large Ischemic Regions

Introduction: Recently, we reported that apparent diffusion coefficient (ADC) values are independently associated with diffusion-weighted imaging (DWI) reversal, and DWI lesions with mean ADC ≥ 520 х 10 -6 mm 2 /s are salvageable by mechanical thrombectomy. These areas regain neurological function. This study aimed to determine the effectiveness of mechanical thrombectomy in especially large ischemic regions with mean ADC ≥ 520 х 10 -6 mm 2 /s. Materials and Methods: We conducted a retrospective cohort study including patients with acute ischemic stroke who underwent endovascular mechanical thrombectomy with successful recanalization between April 2017 and March 2021. DWI reversal was assessed through follow-up magnetic resonance imaging 24 h after treatment. Cases with Alberta stroke program early CT score (ASPECTS)-DWI values 3-5 were enrolled in this study. They were classified as DWI lesions with mean ADC ≥ 520 х 10 -6 mm 2 /s and mean ADC < 520 х 10 -6 mm 2 /s. The primary outcome was modified Rankin scale (mRS) score 0-3 (on a scale of 0-6) at 3 months. Results: In total, ASPECTS-DWI values 3-5 were confirmed in 20 patients. Six patients had DWI lesions with mean ADC ≥ 520 х 10 -6 mm 2 /s, and the remaining 14 patients had DWI lesions with mean ADC < 520 х 10 -6 mm 2 /s. DWI reversals were significantly larger in cases with mean ADC ≥ 520 х 10 -6 mm 2 /s than in those with mean ADC < 520 х 10 -6 mm 2 /s (p=.049). The mRS scores at 3 months in cases with mean ADC ≥ 520 х 10 -6 mm 2 /s and ADC < 520 х 10 -6 mm 2 /s were 3 (0.75-3.75) and 5 (4-6), respectively. mRS score was significantly improved in cases with mean ADC ≥ 520 х 10 -6 mm 2 /s than in cases with mean ADC < 520 х 10 -6 mm 2 /s (p=.011). Conclusions: In large ischemic regions (ASPECTS-DWI: 3-5), DWI lesions with mean ADC ≥ 520 х 10 -6 mm 2 /s are associated with preferable outcomes. The ADC value is easily assessed and a useful tool to predict viable lesions. Therefore, the ADC value could be a new perspective to ascertain the effectiveness of mechanical thrombectomy in large ischemic regions. ABBREVIATIONS: ASPECTS = Alberta stroke program early CT score; ADC = apparent diffusion coefficient; DWI = diffusion-weighted imaging; mRS = modified Rankin scale

Clinical Impact and Predictors of Diffusion Weighted Imaging(DWI) Reversal in Stroke Patients with Diffusion Weighted Imaging Alberta Stroke Program Early CT Score0-5 Treated by Thrombectomy : Diffusion Weighted Imaging Reversal in Large Volume Stroke.

To determine whether reversal of DWI lesions (DWIr) on the DWI-ASPECTS (diffusion weighted imaging Alberta Stroke Program CT Score) template should serve as apredictor of 90-day clinical outcome in acute ischemic stroke (AIS) patients with pretreatment diffusion-weighted imaging (DWI)-ASPECTS0-5 treated with thrombectomy, and to determine its predictors in current practice. We analyzed data of all consecutive patients included in the prospective multicenter national Endovascular Treatment in Ischemic Stroke Registry between 1 January 2015 and 31 December 2020 with apremorbid mRS ≤ 2, who presented with apretreatment DWI-ASPECTS 0-5score, underwent thrombectomy and had an available 24 h post-interventional MRI follow-up. Multivariable analyses were performed to evaluate the clinical impact of DWIr on early neurological improvement (ENI), 3‑month modified Rankin scale (mRS) score distribution (shift analysis) and to define independent predictors of DWIr. Early neurological improvement was detected in 82/211 (41.7%) of patients while 3‑month functional independence was achieved by75 (35.5%) patients. The DWI reversal (39/211, 18.9%) resulted an independent predictor of both ENI (aOR3.6, 95% CI 1.2-7.7; p0.018) and 3‑month clinical outcome (aOR for mRS shift:2.2, 95% CI 1-4.6; p0.030). Only successful recanalization (mTICI2c-3) independently predicted DWIr in the studied population (aOR3.3, 95% CI 1.3-7.9; p0.009). The DWI reversal occurs in anon-negligible proportion of DWI-ASPECTS0-5 patients subjected to thrombectomy and significantly influences clinical outcome. The mTICI2c-3 recanalization emerged as an independent DWIr predictor.

Does Diffusion Lesion Volume Above 70 mL Preclude Favorable Outcome Despite Post-Thrombolysis Recanalization?

Whether to withhold recanalization treatment when the diffusion-weighted imaging (DWI) lesion exceeds a given volume is unsettled. Our aim was to assess the impact of recanalization on outcome in patients with baseline DWI lesion ≥70 mL (DWI≥70 mL) treated ≤4.5 hours from onset. We hypothesized that recanalization is beneficial in a sizeable fraction of these patients and that this is associated with a larger DWI lesion reversal. We analyzed 267 consecutive patients treated with intravenous recombinant tissue-type plasminogen activator for middle cerebral artery territory stroke in whom an occlusion was present on magnetic resonance angiography and 24-hour recanalization and 90-day clinical outcome could be assessed. After stratification relative to the 70-mL DWI lesion cut point, we calculated the odds ratio for recanalization of the primary arterial occlusive lesion (AOL score ≥2) to predict favorable outcome (modified Rankin scale score ≤2). DWI lesion reversal was compared between recanalizers with DWI≥70 mL with favorable and unfavorable outcomes. Median (interquartile range) DWI lesion volume was 22 mL (10-60), and median onset time to imaging was 116 minutes (86-151). Twelve (22%) of the 54 patients with DWI≥70 mL experienced favorable outcome, of which 9 had recanalized. In patients with DWI≥70 mL, recanalization was significantly associated with favorable outcome after adjustment for age and National Institutes of Health Stroke Scale (odds ratio =4.72 [1.09-20.32]; P=0.0375). Among recanalizers with DWI≥70 mL, absolute and relative DWI reversal volumes were larger in those with favorable as compared with unfavorable outcome (18.8 mL [12.2-47.6] versus 8.5 mL [4.3-31.1]; P=0.17; and 19.6% [10.9-62.8] versus 8.7% [3.9-16.5], respectively; P=0.049). Patients with DWI lesion volume ≥70 mL can benefit from recanalization after intravenous recombinant tissue-type plasminogen activator. This may partly reflect a larger amount of DWI lesion reversal.

MRI Assessment of Ischemic Lesion Evolution within White and Gray Matter

Background: In acute ischemic stroke (AIS), gray matter (GM) and white matter (WM) have different vulnerabilities to ischemia. Thus, we compared the evolution of ischemic lesions within WM and GM using MRI. Methods: From a European multicenter prospective database (I-KNOW), available T1-weighted images were identified for 50 patients presenting with an anterior AIS and a perfusion weighted imaging (PWI)/diffusion weighted imaging (DWI) mismatch ratio of 1.2 or more. Six lesion compartments were outlined: initial DWI (b = 1,000 s/mm²) lesion, initial PWI-DWI mismatch (T_max >4 s and DWI-negative), final infarct mapped on 1-month fluid-attenuated inversion recovery (FLAIR) imaging, lesion growth between acute DWI and 1-month FLAIR, DWI lesion reversal at 1 month and salvaged mismatch. The WM and GM were segmented on T1-weighted images, and all images were co-registered within subjects to the baseline MRI. WM and GM proportions were calculated for each compartment. Results: Fifty patients were eligible for the study. Median delay between symptom onset and baseline MRI was 140 min. The percentage of WM was significantly greater in the following compartments: initial mismatch (52.5 vs. 47.5%, p = 0.003), final infarct (56.7 vs. 43.3%, p < 0.001) and lesion growth (58.9 vs. 41.2%, p < 0.001). No significant difference was found between GM and WM percentages within the initial DWI lesion, DWI reversal and salvaged mismatch compartments. Conclusions: Ischemic lesions may extend preferentially within the WM. Specific therapeutic strategies targeting WM ischemic processes may deserve further investigation.

Dynamic Evolution of Diffusion-Weighted Imaging Lesions in Patients With Minor Ischemic Stroke.

Diffusion-weighted imaging (DWI) lesion volume on magnetic resonance imaging is increasingly being used as a surrogate outcome measure in clinical trials. We aimed to characterize the evolution of DWI lesion volumes within 30 days of symptom onset after minor stroke. Minor stroke patients with DWI lesions on magnetic resonance imaging within 48 hours of symptom onset were prospectively followed with magnetic resonance imaging brain scan at 7 and 30 days. Change in the lesion volume was defined as the difference between day 30 Fluid-Attenuated Inversion Recovery and baseline DWI lesion volumes. Three patterns of infarct evolution were observed: reduction (72 [63%]), no change (26 [23%]), and growth (16 [14%]). Patients with infarct reduction at 30 days had larger baseline DWI lesion volumes (2.5 [0.9-8.5] mL) than those with stable infarcts (0.5 [0.3-0.9] mL; P=0.01). Complete DWI reversal at day 30, was seen in only 6 (5.3%) patients. The most common pattern of infarct evolution in patients with minor stroke is a reduction in volume, but complete resolution is uncommon.

Predictors of Infarct Growth after Endovascular Therapy for Acute Ischemic Stroke

Intra-arterial (IA) thrombectomy for acute ischemic stroke has an excellent recanalization rate but variable outcomes. The core infarct also grows at a variable rate despite recanalization. We aim to study the factors that are associated with infarct growth after IA therapy. We reviewed the hyperacute ischemic stroke imaging database at Cleveland Clinic for those undergoing endovascular thrombectomy of anterior circulation from 2009 to 2012. Patients with both pretreatment and follow-up magnetic resonance imaging were included. Seventy-six patients were stratified into quartiles by infarct volume growth from initial to follow-up diffusion-weighted imaging (DWI) measure by a region of interest demarcation. The median infarct growth of each quartile was .6 cm(3) (no-growth group), 13.8, 37, and 160.2 cm(3) (large-growth group). Pretreatment stroke severity was comparable among groups. Compared with the no-growth group, the large-growth group had larger initial infarct defined by computed tomography (CT) Alberta Stroke Program Early CT score (median 10 versus 8, P = .032) and DWI volume (mean 13.8 versus 29.2 cm(3), P = .034), lack of full collateral vessels on CT angiography (36.8% versus 0%, P = .003), and a lower recanalization rate (thrombolysis in cerebral infarction ≥2b, P = .044). The increase in infarct growth is associated with decrease in favorable outcomes defined by a modified Rankin Scale score of 0-2 at 30 days: 57.9%, 42.1%, 21.1%, and 5.3%, respectively (P < .001). DWI reversal was observed in 11 of 76 patients, translating to 82% favorable outcome. Infarct evolution after endovascular thrombectomy is associated with an outcome. DWI reversal or no growth translated to a favorable outcome. Small initial ischemic core, good collateral support, and better recanalization grades predict the smaller infarct growth and favorable outcome after endovascular thrombectomy.

Stroke : Highlights of Selected Articles

<i>Stroke</i> : Highlights of Selected Articles

Early Diffusion-Weighted Imaging Reversal After Endovascular Reperfusion Is Typically Transient in Patients Imaged 3 to 6 Hours After Onset

The aim of this study was to assess the frequency and extent of early diffusion-weighted imaging (DWI) lesion reversal after endovascular therapy and to determine whether early reversal is sustained or transient. MRI with DWI perfusion imaging was performed before (DWI 1) and within 12 hours after (DWI 2) endovascular treatment; follow-up MRI was obtained on day 5. Both DWIs were coregistered to follow-up MRI. Early DWI reversal was defined as the volume of the DWI 1 lesion that was not superimposed on the DWI 2 lesion. Permanent reversal was the volume of the DWI 1 lesion not superimposed on the day 5 infarct volume. Associations between early DWI reversal and clinical outcomes in patients with and without reperfusion were assessed. A total of 110 patients had technically adequate DWI before endovascular therapy (performed median [interquartile range], 4.5 [2.8-6.2] hours after onset); 60 were eligible for this study. Thirty-two percent had early DWI reversal >10 mL; 17% had sustained reversal. The median volume of permanent reversal at 5 days was 3 mL (interquartile range, 1.7-7.0). Only 2 patients (3%) had a final infarct volume that was smaller than their baseline DWI lesion. Early DWI reversal was not an independent predictor of clinical outcome and was not associated with early reperfusion. Early DWI reversal occurred in about one third of patients after endovascular therapy; however, reversal was often transient and was not associated with a significant volume of tissue salvage or favorable clinical outcome.

Diffusion Lesion Reversal After Thrombolysis

In acute stroke, diffusion-weighted imaging (DWI) lesions are commonly considered markers of irreversible ischemia yet can occasionally reverse. However, the extent and clinical correlates of DWI reversal in thrombolyzed patients remain unclear. We assessed the extent of reversible acute DWI lesions (RADs) and their relationships with clinical outcome in patients thrombolyzed≤4.5 hours from onset. Data were retrospectively analyzed. RAD was defined as an acute DWI lesion not part of a 24-hour DWI lesion as determined voxelwise. Associations with an early neurological improvement (early neurological improvement=ΔNational Institutes of Health Stroke Scale≥8 or National Institutes of Health Stroke Scale≤2 at 24 hours) or an excellent outcome (modified Rankin Scale≤1) were assessed in multivariate analyses. One hundred seventy-six patients were included. The median (interquartile range) time to treatment from onset was 150 minutes (120-194). Eighty-nine patients (50%) exhibited visually-detectable RAD irrespective of its extent. Over the whole population, the median percentage and volume of RAD were 11% (4-36) and 2.4 mL (0.5-8). Subtracting RAD from initial DWI altered perfusion-weighted imaging-DWI classification in 5 of 100 patients (shift from "no mismatch" to "mismatch" profile in all). Percent RAD was significantly greater in patients treated≤3 hours (P=0.049), without proximal occlusion (P=0.003), and in 24-hour recanalizers (P<0.001). Early neurological improvement was independently associated with percent RAD. This association increased with percent RAD split in quartiles in a "dose-dependent" manner (P for trend=0.01). Excellent outcome was independently associated with percent RAD (P for trend<0.001). DWI reversal was often sizeable in patients treated≤4.5 hours. It was strongly associated with, albeit not necessarily causal for, early neurological improvement.

Abstract 2674: DWI Reversal is associated with Small Infarct Volume and Early Reperfusion in Patients with TIA and Minor Stroke. Data from VISION and CATCH study groups

Introduction: One-third of patients with TIA and minor ischemic stroke (MIS) have evidence of ischemic penumbra, defined as hypoperfused regions that have not been irreversibly damaged. Diffusion weighted Imaging (DWI) lesions are thought to represent irreversibly damaged tissue. DWI reversal therefore has implications in accurate estimation of penumbra. We aimed to determine the rate of DWI reversal in this population. Methods: Patients with TIA/MIS (NIH Stroke Scale ≤ 3) were prospectively enrolled and imaged within 24 hours of symptom onset as part of two prospective imaging cohorts. Patients were included if their baseline modified Rankin scale (mRS) score was ≤1. All patients were followed clinically for 3 months and had a repeat MRI either at day 30 or 90. Baseline diffusion and perfusion lesions and follow-up FLAIR final infarct volumes were measured. Results: 418 patients were included; 55.5% had DWI lesions and 37% had PWI (Tmax+2s delay) deficits at baseline. A total of 337 (81%) patients had follow-up imaging. DWI reversal occurred in 22/192 (11.5%) of patients who had a diffusion lesion at baseline. The median time from symptom onset to follow-up imaging was not significantly different between those with or without DWI reversal (78.6 days, IQR=33.3 vs. 79.7 days, IQR= 59.4, p=0.65). The median DWI lesion volume was significantly smaller in those with reversal (0.27ml, IQR=0.75 ml) compared to those who did not reverse (1.45 ml, IQR=3.8 ml, p&lt;0.001). Patients with concurrent perfusion deficits (Tmax+2s) were significantly less likely to have DWI reversal (6%) compared to those without evidence of tissue hypoperfusion (20%; p=0.003). DWI reversal occurred in 4% of patients with penumbral patterns ((Tmax+2s)-DWI) and 18% of those without penumbra (p=0.003).Severity of hypoperfusion defined as greater prolongation of Tmax (+2,+4, +6, +8s) did not affect the likelihood of DWI reversal (linear trend p=0.147). No patient with DWI reversal had a mRS of ≥2 at 90 day, compared to 19% of those with evidence of infarction on follow-up imaging (p= 0.02). Conclusion: DWI reversal is common in patients with TIA/MIS and is more likely to occur in those with smaller baseline lesions without concurrent tissue hypoperfusion. DWI reversal therefore should not have a significant effect on the accuracy of penumbra definition. These data suggest early reperfusion is correlated with DWI reversal and better clinical outcome as measured by mRS.

Geography, Structure, and Evolution of Diffusion and Perfusion Lesions in Diffusion and Perfusion Imaging Evaluation For Understanding Stroke Evolution (DEFUSE)

The classical representation of acute ischemic lesions on MRI is a central diffusion-weighted imaging (DWI) lesion embedded in a perfusion-weighted imaging (PWI) lesion. We investigated spatial relationships between final infarcts and early DWI/PWI lesions before and after intravenous thrombolysis in the Diffusion and perfusion imaging Evaluation For Understanding Stroke Evolution (DEFUSE) study. Baseline and follow-up DWI and PWI lesions and 30-day fluid-attenuated inversion recovery scans of 32 patients were coregistered. Lesion geography was defined by the proportion of the DWI lesion superimposed by a Tmax (time when the residue function reaches its maximum) >4 seconds PWI lesion; Type 1: >50% overlap and Type 2: < or = 50% overlap. Three-dimensional structure was dichotomized into a single lesion (one DWI and one PWI lesion) versus multiple lesions. Lesion reversal was defined by the percentage of the baseline DWI or PWI lesion not superimposed by the early follow-up DWI or PWI lesion. Final infarct prediction was estimated by the proportion of the final infarct superimposed on the union of the DWI and PWI lesions. Single lesion structure with Type 1 geography was present in only 9 patients (28%) at baseline and 4 (12%) on early follow-up. In these patients, PWI and DWI lesions were more likely to correspond with the final infarcts. DWI reversal was greater among patients with Type 2 geography at baseline. Patients with multiple lesions and Type 2 geography at early follow-up were more likely to have early reperfusion. Before thrombolytic therapy in the 3- to 6-hour time window, Type 2 geography is predominant and is associated with DWI reversal. After thrombolysis, both Type 2 geography and multiple lesion structure are associated with reperfusion.

Apparent Diffusion Coefficient Thresholds Do Not Predict the Response to Acute Stroke Thrombolysis

Apparent diffusion coefficient (ADC) thresholds for tissue infarction have been identified in acute stroke. IV tissue plasminogen activator (tPA) is associated with tissue salvage. We hypothesized that tPA would lower the ADC threshold for infarction. ADC and mean transit time (MTT) maps were generated for 26 patients imaged within 6 hours of stroke onset (12 tPA and 14 conservatively managed controls). MTT maps and day-90 T2-weighted images were coregistered to ADC maps. Relative ADC (rADC) values were calculated for initial diffusion-weighted imaging (DWI) lesions, infarct growth regions (final infarct volume-the acute DWI lesion volume), and hypoperfused salvaged regions (HS; MTT map abnormality-the final infarct volume). When relevant, the DWI lesion was subdivided into DWI reversal and DWI infarct regions. Mean DWI lesion rADC was 0.79 in tPA and 0.74 in untreated patients (P=0.097). Mean rADC in HS and infarct growth regions were similar in tPA patients (0.950 and 0.946) and untreated patients (0.957, P=0.76; 0.970, P=0.08, respectively). The rADC in HS tissue was directly correlated with the time to treatment with tPA (r=0.685; P=0.029). DWI reversal was seen in 67% of tPA-treated patients and in 36% of those conservatively managed (Fisher exact test; P=0.238). In the 13 patients with DWI reversal, the mean rADC in these regions (0.81+/-0.07) was significantly higher than in the acute DWI region that infarcted (0.74+/-0.07; P=0.02), although no absolute thresholds could be identified. The peri-DWI lesion region contains tissue with intermediate ADC values. The fate of this tissue is variable and cannot be predicted based on the ADC alone. DWI expansion occurs in bioenergetically normal tissue, and this is attenuated by tPA in a time-dependent fashion.