Prediction of infarct growth and neurologic deterioration in patients with positive perfusion-diffusion mismatch

Background

To assess the value of baseline clinical severity and perfusion–diffusion mismatch as predictors for further infarct growth and clinical outcome.

Methods

Patients with acute ischemic stroke and initial perfusion–diffusion mismatch within 72 h were enrolled. Baseline perfusion defects on time-to-peak (TTP) and cerebral blood volume (CBV) maps were measured. Infarct volume and stroke severity were assessed by diffusion-weighted image (DWI) and NIHSS, and were repeatedly assessed 7 days later. The predictive value of baseline NIHSS and perfusion defects on further infarct growth and neurologic deterioration was determined.

Results

Fifty-two patients (mean age 68.3 ± 12.8 years, 42% women) were enrolled. CBV defects were significantly associated with infarct growth (CBV, p = 0.02). Initial stroke severity, but not TTP and CBV mismatch (p = 0.65 and 0.76, respectively), significantly inversely correlated with neurologic deterioration (p = 0.001).

Conclusions

In patients with mismatch, those with severe symptoms initially are more likely to have infarct growth, while those with minor symptoms tend to suffer from larger extent of neurologic deterioration within 1 week. CBV is associated with further infarct growth but not clinical deterioration.     

The role of ASPECTs in patient selection for endovascular therapy – CTA source images versus noncontrast CT

The Alberta Stroke Program Early Computed Tomography Score (ASPECTs) on noncontrast CT (NCCT) is widely used for the decision of endovascular therapy (ET) in randomized controlled trials. CT angiography source images (CTA-SI) is another method to evaluate ischemic brain damage. We aimed to evaluate the association between pretreatment ASPECTs on CTA-SI and post-treatment clinical and radiological outcomes in acute stroke patients treated with ET. The association between both scores along with final infarct and outcome were analyzed. A total of 90 patients with successful recanalization were included in the study. The mean age was 59 ± 11.8. According to the results, CTA-SI ASPECTs was better correlated with final infarct than NCCT ASPECTs (p < 0.001). In univariate analyzes, factors associated with good outcome were age, baseline NIHSS score, and presence of diabetes mellitus (p = 0.001, p = 0.002, p = 0.034, respectively). On the other hand, when an analysis differentiating patients by age was performed, 40 patients below 60 years of age had significantly better outcomes despite having higher baseline NIHSS scores (p = 0.002). Finally, in multivariate analyzes, only age and baseline NIHSS score were found to be independent predictors of good outcome (p = 0.003 for both). In conclusion, CTA-SI ASPECTs in patient selection for ET seems to be more useful than NCCT ASPECTs. However, both scoring modalities were not found to be independent predictors of good outcome. Outcomes are changeable for the younger population who could continue their lives with mild or no deficits despite having a relatively low initial ASPECTs.     

Perfusion computed tomography: prediction of final infarct extent and stroke outcome

The Alberta Stroke Program Early Computed Tomography Score (ASPECTS) has not been previously applied to perfusion CT (CTP). Five raters assigned ASPECTS to baseline noncontrast CT (NCCT), CT angiography source images (CTA-SI), CTP source images (CTP-SI), and CTP maps of cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) from 37 consecutive patients with less than 6-hour anterior circulation ischemic stroke. Major reperfusion was identified on follow-up imaging. Mean baseline ASPECTS was compared with follow-up imaging ASPECTS. Rates of favorable outcome were compared for dichotomized baseline ASPECTS. In patients with major reperfusion, mean CBV and CTP-SI ASPECTS closely predicted final infarct ASPECTS. In patients without major reperfusion, mean CBF and MTT ASPECTS best predicted final infarct ASPECTS. There were significant increases in rates of favorable outcome for CTP-SI and CBV ASPECTS of greater than 6, versus less than or equal to 6, but not for other baseline CT modalities. ASPECTS applied to CTP is more accurate at identifying the extent of reversible and irreversible ischemia and at predicting final clinical outcome than NCCTor CTA-SI.     

Window narrowing: a new method for standardized assessment of the tissue at risk-maximum of infarction in CT based brain perfusion maps

BACKGROUND: Mapping of brain perfusion using bolus tracking methods is increasingly used to assess the amount and severity of cerebral ischemia in acute stroke. Using relative perfusion maps, however, it is difficult to identify the tissue at risk-maximum (TARM) of infarction with sufficient reliability and reproducibility. METHODS: We analysed 76 perfusion computed tomography (PCT) derived maps of cerebral blood flow (CBF), cerebral blood volume (CBV) and time-to-peak (TTP) in 40 acute stroke patients using multidetector row technology and standard software (Somatom VolumeZoom, Siemens, Germany). 'Window narrowing' of the color maps was performed until color homogenisation of the contralateral unaffected hemisphere was reached. Tissue still depictable on the affected hemisphere after sufficient window narrowing was defined as the TARM. We analysed presence and size of the TARM on PCT maps, its relative perfusion values by comparison with contralateral, mirrored tissue, and its correlation with occurrence and final size of cerebral infarction on follow-up imaging. RESULTS: An ischemic area was visible in 64, 58.9 and 72.6% on the conventional CBF, CBV and TTP maps, respectively. After window narrowing, a TARM was present in 56.8, 54.1 and 63.0% of slices comprising 11.9, 11.6 and 21.1% of the ipsilateral hemisphere (CBF, CBV and TTP), respectively. The relative perfusion values were 38.7 (CBF) and 43.0% (CBV) for the entire ischemic area and 11.3 (CBF) and 13.3% (CBV) for the TARM. Definite cerebral infarction was visible on 68.1% of the target slices comprising 23.7 +/- 22.9% of the ipsilateral hemisphere. The size of the TARM correlated slightly better with the final infarction size (r=0.74-0.82) than the entire ischemic area (r=0.61-0.79). With respect to the occurrence of cerebral infarction, the presence of a TARM on CBF maps showed the best positive (97.9%) and negative (72.7%) predictability. DISCUSSION: On PCT maps, window narrowing provides a standardized display of the TARM in peracute stroke. The severely reduced values of relative CBF and CBV suggest the TARM to indicate tissue most prone to infarction.     

Prediction of infarct volume and neurologic outcome by using automated multiparametric perfusion-weighted magnetic resonance imaging in a primate model of permanent middle cerebral artery occlusion

By optimizing thresholds, we identified the perfusion-weighted magnetic resonance imaging (PWI) parameters that accurately predict final infarct volume and neurologic outcome in a primate model of permanent middle cerebral artery (MCA) occlusion. Ten cynomolgus monkeys underwent PWI and diffusion-weighted imaging (DWI) at 3 and 47 hours, respectively, after right MCA occlusion using platinum coils, and were killed at 48 hours. Volumes of the hypoperfused areas on PWI were automatically measured using different thresholds and 11 parametric maps to determine the optimum threshold (at which least difference was found between the average volumes on PWI and those determined using specimens or DWI). In the case of arrival time (AT), cerebral blood volume (CBV), time to peak (TTP), time to maximum (T_max), and cerebral blood flow (CBF) determined using deconvolution techniques, the volume of the hypoperfused area significantly correlated with the infarct volumes and the neurologic deficit scores with small variations, whereas in the case of mean transit time and nondeconvolution CBF, relatively poor correlations with large variations were seen. At optimum threshold, AT, CBV, TTP, T_max, and deconvolution CBF can accurately predict the final infarct volume and neurologic outcome in monkeys with permanent MCA occlusion.     

VCTDSA联合CT灌注成像对急性缺血性脑卒中影像诊断价值

目的探讨容积CT数字减影血管造影VCTDSA联合CT灌注成像在急性缺血性脑卒中的诊断价值。方法对30例临床诊断为急性缺血性脑卒中的患者于发病后24h内行VCTDSA联合CT灌注成像,观察CT平扫表现及灌注图像、VCTDSA重建图像结果。测定相应区域脑血流量(CBF),脑血容量(CBV),平均通过时间(MTT)和达峰时间(TTP)。结果 25例急性缺血性脑卒中患者头部CT平扫未发现与临床症状相对应的脑缺血区,CT灌注图上可发现与临床症状相对应的脑缺血区。CT灌注成像表现为CBF下降、CBV下降、MTT延长、TTP延长或无TTP出现。VCTDSA可见23例患者相应责任血管的不同程度的狭窄,其余7例患者未检出相应责任血管狭窄。结论 CT灌注成像在急性缺血性脑卒中的早期诊断中有很重要的价值。VCTDSA能发现缺血病变的原因,为临床进一步治疗提供确切依据。     

Combined diffusion and perfusion MRI with correlation to single-photon emission CT in acute ischemic stroke. Ischemic penumbra predicts infarct growth.

BACKGROUND AND PURPOSE: More effective imaging methods are needed to overcome the limitations of CT in the investigation of treatments for acute ischemic stroke. Diffusion-weighted MRI (DWI) is sensitive in detecting infarcted brain tissue, whereas perfusion-weighted MRI (PWI) can detect brain perfusion in the same imaging session. Combining these methods may help in identifying the ischemic penumbra, which is an important concept in the hemodynamics of acute stroke. The purpose of this study was to determine whether combined DWI and PWI in acute (<24 hours) ischemic stroke can predict infarct growth and final size. METHODS: Forty-six patients with acute ischemic stroke underwent DWI and PWI on days 1, 2, and 8. No patient received thrombolysis. Twenty-three patients underwent single-photon emission CT in the acute phase. Lesion volumes were measured from DWI, SPECT, and maps of relative cerebral blood flow calculated from PWI. RESULTS: The mean volume of infarcted tissue detected by DWI increased from 46.1 to 75.6 cm(3) between days 1 and 2 (P<0.001; n=46) and to 78.5 cm(3) after 1 week (P<0.001; n=42). The perfusion-diffusion mismatch correlated with infarct growth (r=0. 699, P<0.001). The volume of hypoperfusion on the initial PWI correlated with final infarct size (r=0.827, P<0.001). The hypoperfusion volumes detected by PWI and SPECT correlated significantly (r=0.824, P<0.001). CONCLUSIONS: Combined DWI and PWI can predict infarct enlargement in acute stroke. PWI can detect hypoperfused brain tissue in good agreement with SPECT in acute stroke.     

Imaging viable brain tissue with CT scan during acute stroke

Viability of the cerebral parenchyma is dependent on cerebral blood flow (CBF). The assessment of cerebral perfusion in patients with acute stroke, in a clinically relevant time frame, could be of utmost importance for patient selection before thrombolytic therapy. In individual patients, quantitative mapping of CBF to indicate the severity and potential reversibility of neuronal damage can be used to predict which brain tissue will be salvaged with reperfusion or die without it (penumbra), as well as which brain tissue is already infarcted. Recent investigations of perfusion CT have shown major advances in the assessment of acute stroke patients. Perfusion CT offers a number of practical advantages over other cerebral perfusion imaging methods as it can be performed immediately after unenhanced CT, and used, in general, to exclude cerebral haemorrhage. It is fast (typical procedure time <5 min) and does not require specialized computer hardware. The accuracy of cerebral perfusion maps has been demonstrated for normal and decreased CBF value by comparison with xenon CT used as a gold standard. Perfusion CT infarct and penumbra maps provide a potential recuperation ratio (PRR) (or Lausanne Stroke Index), defined as PRR = penumbra/ (penumbra + infarct). This index is correlated with the improvement of the National Institutes of Health Stroke Scale (NIHSS) in case of arterial recanalization. Also, the size of the ischaemic area (infarct + penumbra) is correlated with the NIHSS score on hospital admission. Further studies may demonstrate the use of perfusion CT for the assessment of penumbra dynamics in function-specific brain areas. Perfusion CT is now ready to be used in clinical trials as a decision-making tool to tailor more precisely the thrombolytic therapy to the individual patient.     

Prognostic accuracy of cerebral blood flow measurement by perfusion computed tomography, at the time of emergency room admission, in acute stroke patients

The purpose of this study was to determine the prognostic accuracy of perfusion computed tomography (CT), performed at the time of emergency room admission, in acute stroke patients. Accuracy was determined by comparison of perfusion CT with delayed magnetic resonance (MR) and by monitoring the evolution of each patient's clinical condition. Twenty-two acute stroke patients underwent perfusion CT covering four contiguous 10mm slices on admission, as well as delayed MR, performed after a median interval of 3 days after emergency room admission. Eight were treated with thrombolytic agents. Infarct size on the admission perfusion CT was compared with that on the delayed diffusion-weighted (DWI)-MR, chosen as the gold standard. Delayed magnetic resonance angiography and perfusion-weighted MR were used to detect recanalization. A potential recuperation ratio, defined as PRR = penumbra size/(penumbra size + infarct size) on the admission perfusion CT, was compared with the evolution in each patient's clinical condition, defined by the National Institutes of Health Stroke Scale (NIHSS). In the 8 cases with arterial recanalization, the size of the cerebral infarct on the delayed DWI-MR was larger than or equal to that of the infarct on the admission perfusion CT, but smaller than or equal to that of the ischemic lesion on the admission perfusion CT; and the observed improvement in the NIHSS correlated with the PRR (correlation coefficient = 0.833). In the 14 cases with persistent arterial occlusion, infarct size on the delayed DWI-MR correlated with ischemic lesion size on the admission perfusion CT (r = 0.958). In all 22 patients, the admission NIHSS correlated with the size of the ischemic area on the admission perfusion CT (r = 0.627). Based on these findings, we conclude that perfusion CT allows the accurate prediction of the final infarct size and the evaluation of clinical prognosis for acute stroke patients at the time of emergency evaluation. It may also provide information about the extent of the penumbra. Perfusion CT could therefore be a valuable tool in the early management of acute stroke patients.     

Influence of pretreatment MRI parameters on clinical outcome, recanalization and infarct size in 49 stroke patients treated by intravenous tissue plasminogen activator

We hypothesized that pretreatment magnetic resonance imaging (MRI) parameters might predict clinical outcome, recanalization and final infarct size in acute ischemic stroke patients treated by intravenous recombinant tissue plasminogen activator (rt-PA). MRI was performed prior to thrombolysis and at day 1 with the following sequences: magnetic resonance angiography (MRA), T2*-gradient echo (GE) imaging, diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI). Final infarct size was assessed at day 60 by T2-weighted imaging (T2-WI). The National Institutes of Health Stroke Scale (NIHSS) score was assessed prior to rt-PA therapy and the modified Rankin Scale (m-RS) score was assessed at day 60. A poor outcome was defined as a day 60 m-RS score >2. Univariate and multivariate logistic regression analyses were used to identify the predictors of clinical outcome, recanalization and infarct size. Forty-nine patients fulfilled the inclusion criteria. Baseline NIHSS score was the best independent indicator of clinical outcome (p=0.002). A worse clinical outcome was observed in patients with tandem internal carotid artery (ICA)+middle cerebral artery (MCA) occlusion versus other sites of arterial occlusion (p=0.009), and in patients with larger pretreatment PWI (p=0.001) and DWI (p=0.01) lesion volumes. Two factors predict a low rate of recanalization: a proximal site of arterial occlusion (p=0.02) and a delayed time to peak (TTP) on pretreatment PWI (p=0.05). The final infarct size was correlated with pretreatment DWI lesion volume (p=0.025). Recanalization was associated with a lower final infarct size (p=0.003). In conclusion, a severe baseline NIHSS score, a critical level of pretreatment DWI/PWI parameters and a proximal site of occlusion are predictive of a worse outcome after IV rt-PA for acute ischemic stroke.     

建立急性缺血性卒中的临床/多模式CT预后评分系统

目的 建立一个简便、有效的临床/多模式CT评分系统,用以指导急性缺血性卒中患者的临床治疗和评估90 d后临床功能恢复情况。方法 选择49例急性缺血性卒中（发病时间＜9 h）的患者行“多模式CT”扫描,包括平扫CT（non-contrast enhanced computed tomography,NCCT）、CT灌注成像（computed tomography perfusion,CTP）和CT血管成像（computed tomography angiography,CTA）;评价患者基线NCCT、动脉期CTP原始图（arterial phase CTP source images,ACTP-SI）、静脉期CTP原始图（venous phase CTP source images,VCTP-SI）、CTA卒中溶栓分级（thrombolysis in cerebral ischemia scale,TICI）、Alberta卒中项目早期CT评分（Alberta Stroke Program Early CT Score Study,ASPECTS）及基线美国国立卫生研究院卒中量表（National Institute of Health Stroke Scale,NIHSS）评分,并应用受试者工作特征曲线（receiver-operating characteristics,ROC）分析,判断90 d临床功能恢复良好［采用改良的Rankin量表（modified Rankin Scale,mRS）<2作为评判标准］的临床和CT参数阈值;按照获得的阈值进行评分,将多模式CT各参数的阈值评分整合在一起获得多模式CT评分系统,将基线NIHSS阈值评分加入多模式CT评分系统中获得临床/多模式CT评分。最后应用ROC曲线分析比较各评分模式预测临床功能恢复的效能。结果 判断90 d临床功能恢复良好的阈值：临床/多模式CT评分>1,多模式CT评分>1,基线NCCT ASPECTS>9,动脉期CTP原始图ASPECTS>6.5,静脉期CTP原始图ASPECTS>8.5,CTA TICI>1及基线NIHSS≥7;临床/多模式CT评分ROC曲线下面积最大（0.87,95%可信区间0.75～0.95),其预测急性缺血性卒中患者90 d临床功能恢复的效能最高,接下来依次是多模式CT评分、ACTP-SI、VCTP-SI、NIHSS、NCCT及CTA,除临床/多模式CT评分与ACTP-SI（P=0.226）及NIHSS阈值评分（P=0.174）的差异显著性外,其余各参数阈值评分与临床/多模式CT评分的差异均有显著性（P＜0.05）。结论 应用临床/多模式CT评分系统比多模式CT及NIHSS各参数单独预测90 d急性缺血性卒中患者的临床功能恢复的效能均高,临床/多模式CT评分系统是预测患者预后的有效评分方法。     

Infarct volume on apparent diffusion coefficient maps correlates with length of stay and outcome after middle cerebral artery stroke

BACKGROUND: Diffusion-weighted MRI (DWI) can depict acute ischemia based on decreased apparent diffusion coefficient (ADC) values. ADC maps, unlike DWI (which have contributions from T2 properties), solely reflect diffusion properties. Recent studies indicate that severity of neurological deficit corresponds with degree of ADC alteration. PURPOSE: To determine whether infarct volume on ADC maps correlates with length of hospitalization and clinical outcome in patients with acute ischemic middle cerebral artery (MCA) stroke. STUDY POPULATION: Forty-five consecutive patients with acute (3 SDs below the average ADC value of a contralateral control region. Infarct volume was correlated with length of hospitalization and 6-month outcome assessed with Glasgow Outcome Scale (GOS), Modified Rankin Score (mRS), Barthel Index (BI) and a dichotomized outcome status with favorable outcome defined as GOS 1, mRS or=95. RESULTS: Infarct volume on ADC maps ranged from 0.2 to 187 cm(3) and was significantly correlated with length of hospitalization (p < 0.001, r = 0.67). Furthermore, ADC infarct volume was significantly correlated with GOS (r = 0.73), mRS (r = 0.68), BI (r = 0.67) and outcome status (r = 0.65) (each p < 0.001). Multiple logistic regression revealed a statistically significant correlation between ADC infarct volume and outcome status (p < 0.05), but none for Canadian Neurological Scale score, age and gender (p >0.05 each). CONCLUSION: Infarct volume measured by using a quantitative definition for infarcted tissue on ADC maps correlated significantly with length of hospitalization (as a possible surrogate marker for short-term outcome) and functional outcome after 6 months. ADC infarct volume may provide prognostic information for patients with acute ischemic MCA stroke.     

Perfusion Imaging Collateral Scores Predict Infarct Growth in Non-Reperfused DEFUSE 3 Patients

ObjectiveThis study evaluated the associations of perfusion imaging collateral profiles with radiographic and clinical outcome in late presenting, non-reperfused patients in the DEFUSE 3 clinical trial.MethodsNon-reperfused patients in both treatment arms were included. Baseline ischemic core, Tmax >6s, and Tmax >10s perfusion volumes were calculated with RAPID software; infarct volumes obtained 24 hours after randomization were manually determined from DWI or CT. Substantial infarct growth was defined as a >25mL increase between baseline and 24-hour follow-up. Hypoperfusion Intensity Ratio (HIR) was defined as the proportion of the Tmax >6s lesion with Tmax >10s delay; CBV index was calculated by RAPID from mean CBV values within the Tmax >6s lesion compared to regions of normal CBV.ResultsEighty-four patients were included. ROC analysis showed HIR ≥0.34 (AUC=0.68) and CBV index ≤0.74 (AUC=0.72) optimally predicted substantial infarct growth in follow-up. Median growth was 23.4 versus 73.2mL with HIR threshold of 0.34 (p=0.005), and 24.3 versus 58.7mL with CBV index threshold of 0.74 (p=0.004). If baseline HIR and CBV index were both favorable, median growth was 21.7mL, 40.9mL if one was favorable, and 108.2mL if both were unfavorable (p<0.001). Baseline perfusion profile was not associated with 90-day functional outcome.ConclusionsPerfusion collateral scores forecast infarct growth in late presenting, non-reperfused ischemic stroke patients. These parameters may be useful for guiding transfer decisions, such as need for repeat imaging upon thrombectomy center arrival, and may help identify slow progressing patients more likely to have persistent salvageable ischemic tissue beyond 24 hours.     

急性脑梗死的320排动态容积CT脑灌注成像研究

目的研究320排动态容积CT全脑灌注成像(CTP)在脑梗死患者中的价值。方法对2014-01—2016-01驻马店市中心医院收治的33例脑梗死患者采取CT全脑灌注成像检查,测量梗死核心区、缺血半暗带(IP)与健侧镜像区的脑血流量(CBF)、脑血容量(CBV)、达峰时间(TTP)及平均通过时间(MTT)值,计算梗死核心区及IP的相对脑血流量(rCBF)、相对脑血容量(rCBV)、相对达峰时间(rTTP)、相对平均通过时间(rMTT),并进行对比分析。结果 33例患者中,头颅平扫发现9例早期脑梗死征象,其余24例未发现异常。33例患者行CTP成像均发现异常灌注区,其中25例存在IP;与健侧镜像区对比,CBV无显著差异(P0.05),而TTP、MTT值明显延长,CBF显著降低,差异有统计学意义(P0.05);与梗死核心区对比,CBF、CBV升高,TTP缩短,MTT延长,差异均有统计学意义(P0.05)。IP区与梗死核心区rCBF、rCBV、rTTP、rMTT对比,差异有统计学意义(P0.05)。10例超急性期(发病6h以内)、15例急性期(发病6~72h)中11例、8例亚急性期(发病72h~14d)中4例存在IP。缺血半暗带分期:Ⅰ2期6例,Ⅱ1期12例,Ⅱ2期7例。结论 320排动态容积CT全脑灌注成像可通过注射一次对比剂获得常规CT、CTP、CTA数据,对脑梗死患者的病变部位、范围及有无IP等提供明确的影像学依据,且可对IP进行分期,为临床实现对患者的个体化治疗提供了可能,且显著降低了患者所受的辐射剂量,安全性高。     

Differential patterns of evolution in acute middle cerebral artery infarction with perfusion-diffusion mismatch: atherosclerotic vs. cardioembolic occlusion

BACKGROUND: An acute perfusion-diffusion mismatch is known to be the strongest predictor of infarct growth. However, the differential patterns of clinical and radiological evolution according to stroke mechanism are unknown. METHODS: The study retrospectively reviewed consecutive patients who had 1) acute middle cerebral artery (MCA) territory infarction, 2) diffusion- and perfusion-weighted imaging (DWI and PWI) and MR angiography within 24 h of onset, and follow-up DWI 5 days later, 3) stenosis (>/=50%) or occlusion of MCA on baseline imaging, 4) a baseline PWI-DWI mismatch >20%, and 5) either atherosclerotic MCA disease (MCAD) or cardioembolism (CE). National Institutes of Health Stroke Scale (NIHSS) scores and infarct volume at baseline and 5 days were obtained. RESULTS: Of 90 patients, 52 had MCAD and 38 had CE. At baseline, CE group had more severe stroke (median NIHSS, 9 vs. 5; p=0.001) and larger infarct volume (median 8.32 cc vs. 3.0 cc; p=0.034) than MCAD group. During the 1-week period, CE group had larger infarct volume growth (median 12.85 cc vs. 3.02 cc; p=0.004) than MCAD group, although clinical improvement based on NIHSS (baseline minus 5-day) tended to be higher for CE than MCAD group (median 3 vs. 1; p=0.08). The correlation between infarct volume and NIHSS score was stronger in CE (r=0.841) compared to MCAD (r=0.582) group at 5-day. CONCLUSIONS: Substantial differences in the clinico-radiological evolution of acute ischemic stroke exist according to stroke mechanism. These data emphasize the importance of the stroke mechanism in the design of MRI-based acute stroke trials.     

Clinical value of computed tomography perfusion source images in acute stroke

Abstract

Computed tomography perfusion (CTP) map can sensitively and accurately distinguish between infarct core and ischemic penumbra. However, CTP mapping software might not generate a perfusion map because of head movement; thus, analysing CTP source images (CTP-SI) is necessary in this situation to provide information for stroke diagnosis and therapy. In our work, 'one-stop shop' computed tomography (CT) examination including non-contrast-enhanced CT (NCCT), CTP, CT angiography (CTA) were performed in 24 patients with symptoms of acute stroke less than 9 hours. We divided patients into two groups (with and without delayed perfusion on CTP-SI), and compared the Alberta Stroke Program Early CT Score (ASPECTS) on CTP-SI and CTA-SI with follow-up imaging. Using follow-up imaging ASPECTS as the final infarct size, our results suggests that the ASPECTS of both CTP-SI and CTA-SI effectively predict final infarct core in the group without delayed perfusion, whereas CTP-SI has a potential advantage over CTA-SI in being able to predict final infarct core in the group with delayed perfusion. In conclusion, CTP-SI provides useful complementary information when CTP map software could not generate perfusion maps.     

Comparison of diffusion-weighted MRI and CT in acute stroke

OBJECTIVE: To compare diffusion-weighted MRI (DWI) and CT with respect to accuracy of localizing acute cerebral infarction; sensitivity, specificity, and interrater reliability for identifying more than one-third middle cerebral artery (MCA) territory involvement; and correlation of acute lesion volume with final infarct volume. METHOD: Nineteen consecutive stroke patients underwent CT and DWI within 7 hours of stroke onset and a follow-up DWI examination 36 hours after symptom onset, which served as the "gold standard" for lesion location and extent of MCA involvement. Each scan was evaluated for acute ischemic lesions by two experienced observers. After 30 days, T2-weighted MRI was obtained for assessment of the final infarct volume. RESULTS: The acute CT and DWI scans were obtained on average 2.6 and 5.1 hours after symptom onset. On DWI the acute lesion was identified correctly in all instances and on CT it was identified correctly in 42 to 63% of patients. Sensitivity for detection of more than 33% MCA involvement was better for DWI (57 to 86%) than for CT (14 to 43%), whereas specificity was excellent for both. Interrater reliability was moderately good for both (kappa, 0.6 for DWI; 0.5 for CT). A positive correlation (r = 0.79; p = 0.001) existed between lesion volume on acute DWI and final infarct volume, whereas no correlation was found between CT volume and final infarct volume. CONCLUSION: When compared with CT, DWI was more accurate for identifying acute infarction and more sensitive for detection of more than 33% MCA involvement. In addition, lesion volume on acute DWI, but not on acute CT, correlated strongly with final infarct volume. Additional studies are required to demonstrate whether these advantages of DWI are clinically relevant in the management of patients with acute stroke.     

Early magnetic resonance imaging prediction of arterial recanalization and late infarct volume in acute carotid artery stroke.

In patients with acute ischemic stroke, early recanalization may save tissue at risk for ischemic infarction, thus resulting in smaller infarcts and better clinical outcome. The hypothesis that clinical and diffusion- and perfusion-weighted imaging (DWI, PWI) parameters may have a predictive value for early recanalization and final infarct size was assessed. Twenty-nine patients were prospectively enrolled and underwent sequential magnetic resonance imaging (1) within 6 hours from hemispheric stroke onset, before thrombolytic therapy; (2) at day 1; and (3) at day 60. Late infarct volume was assessed by T2 -weighted imaging. At each time, clinical status was assessed by the National Institutes of Health Stroke Scale (NIHSS). Twenty-eight patients had arterial occlusion at day 0 magnetic resonance angiography (MRA). They were classified into two groups according to day 1 MRA: recanalization (n = 18) versus persistent occlusion (n = 10). Any significant differences between these groups were assessed regarding (1) PWI and DWI abnormality volumes, (2) relative and absolute time-to-peak (TTP) and apparent diffusion coefficient within the lesion on DWI; and (3) day 60 lesion volume on T2 -weighted imaging. Univariate and multivariate logistic regression analysis showed that the most powerful predictive factors for recanalization were lower baseline NIHSS score and lower baseline absolute TTP within the lesion on DWI. The best predictors of late infarct size were day 0 lesion volume on DWI and day 1 recanalization. Early PWI and DWI studies and day 1 MRA provide relevant predictive information on stroke outcome.     

Hyperdense middle cerebral artery sign: can it be used to select intra-arterial versus intravenous thrombolysis in acute ischemic stroke?

BACKGROUND: Stroke patients with a hyperdense middle cerebral artery sign (HMCAS) may respond less favorably to intravenous (IV) thrombolysis. OBJECTIVE: To compare outcomes of patients with and without early CT findings treated with IV versus intra-arterial (IA) recombinant tissue plasminogen activator (rtPA). METHODS: Initial and 24-hour CT scans of the head were evaluated in 83 consecutive stroke patients (66 on IV rtPA, 17 on IA rtPA). Time permitting, a CT angiogram was performed immediately after the initial CT scan to ascertain major cerebral artery occlusion. Demographics and etiological stroke subtype, times to thrombolysis and CT scan, baseline (prethrombolysis) and 24-hour National Institutes of Health stroke scale (NIHSS) score, discharge NIHSS score and 90-day modified Rankin scale (mRS) were recorded. The initial CT of these patients was examined for early signs of stroke. The 24-hour scan was reviewed for the presence of infarct, hemorrhage and persistence of HCMAS. RESULTS: A favorable outcome, indicated by a significant improvement in the discharge NIHSS score, was noted with IA rtPA, irrespective of the presence (p = 0.001) or absence (p = 0.01) of HCMAS. A less favorable outcome in discharge NIHSS score was noted with IV rtPA in patients with HCMAS (p = not significant) than those without the sign (p < 0.001). A similar proportion of patients with HCMAS exhibited a neurological improvement at 24 h as those without the sign in the IA rtPA group (p = 0.9). However, a smaller proportion of patients with HCMAS exhibited a neurological improvement at 24 h than those without the sign in the IV rtPA group (p = 0.005). The results were similar using 90-day mRS 相似文献   

建立基于临床和磁共振表观弥散系数的急性前循环缺血性卒中预后评估系统

目的 探讨影响急性缺血性卒中预后的因素,建立一种基于临床和多模式磁共振成像（magneticresonance imaging,MRI）的急性前循环缺血性卒中预后评估系统。方法 选择发病9小时内完成多模式MRI的前循环急性缺血性卒中患者40例。按照改良的Ranking量表（modified Ranking Scale,mRS）分为预后良好组（0～1分）和预后不良组（2～6分）。评价两组年龄、基线美国国立卫生研究院卒中量表评分（national institutes of health stroke scale,NIHSS）、基线弥散加权像（diffusion-weighted imaging,DWI）体积、基线灌注加权像（perfusion-weighted imaging,PWI）体积以及由基于表观弥散系数（apparent diffusion coefficient,ADC）的图像分析方法获得的预测梗死核心体积、预测可挽救脑组织体积等临床/影像信息对预后的影响;采用多因素分析筛查出单因素分析中具有统计学意义的变量作为预后评估系统的组成部分,应用受试者工作特征曲线（receiver operatorcharacteristic curve,ROC）分析获得各变量的阈值评分,整合后获得临床/ADC评分,应用ROC曲线下面积（area under curve,AUC）分析各评分模式判断预后的效能。结果 预后良好组与预后不良组在年龄、基线NIHSS、预测梗死核心体积、预测可挽救脑组织体积、预测最终梗死体积、实际最终梗死体积和基线DWI异常区域体积的差异均具有统计学意义。多因素分析显示年龄、预测梗死核心体积、预测最终梗死体积和基线NI HSS能作为判断预后的风险因素,构成临床/ADC预后评分系统的四个因素。应用ROC分析获得以上四个变量判断预后不良的阈值分别为＞58岁、＞5.84 ml 、＞10.6 ml 和＞12分。该评分系统的AUC最大（AUC=0.878,P＜0.01）,其判断急性缺血性卒中患者90 d预后的效能最高,其次是实际最终梗死体积（AUC=0.802,P =0.001）、预测最终梗死体积（AUC=0.797,P =0.001）、预测梗死核心体积（AUC=0.739,P =0.01）、基线NIHSS（AUC=0.759,P =0.005）、预测可挽救脑组织体积（AUC=0.719,P =0.018）和基线DWI异常区域体积（AUC=0.693,P =0.037）。其中,临床/ADC预后评分系统与预测梗死核心体积、预测可挽救脑组织体积、基线DWI异常区域体积AUC之间的差异具有统计学意义（P分别为0.043,0.035和0.01）。结论 临床/ADC预后评分系统比基线NIHSS评分和各影像参数判断90 d急性缺血性卒中患者预后的效能高;制定急性缺血性卒中患者治疗方案时,应结合患者临床和影像信息综合考虑。