多模式CT在评估急性缺血性卒中脑侧支循环中的应用

多模式计算机断层扫描（computed tomography,CT）包括CT平扫（non-contrast CT,NCCT）、 CT灌注成像（CT perfusion,CTP）、CT血管成像（CT angiography,CTA）,可以对急性缺血性卒中后侧支 循环进行全面评估,评估脑灌注状态,了解脑侧支循环建立或开放情况,判断临床预后,在急性缺血 性卒中的诊疗过程中发挥重要的作用。本文就多模式CT在缺血性卒中中的应用进行综述,以期使患 者获益更多。     

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.     

Hemodynamic assessment of acute stroke using dynamic single-slice computed tomographic perfusion imaging

BACKGROUND: Stroke management would benefit from a broadly available imaging tool that detects perfusion deficits in patients with acute stroke. OBJECTIVE: To determine the role of dynamic, single-slice computed tomographic (CT) perfusion imaging (CTP) in the assessment of acute middle cerebral artery stroke. DESIGN AND PATIENTS: Imaging with CTP and CT within the first 6 hours of symptom onset and before the start of treatment in a consecutive clinical series of 22 patients (mean age, 68.3 years; 14 women; studied within 143 +/- 96 minutes of stroke onset). SETTING: A stroke unit in a university hospital. MAIN OUTCOME MEASURES: Area of the perfusion deficit (nAP(0)) from time-to-peak maps, hemispheric lesion area from follow-up CT (HLA(F)), final infarct volume, and stroke recovery (National Institutes of Health Stroke Scale scores). RESULTS: Eighteen patients had perfusion deficits in the middle cerebral artery territory and corresponding hypoattenuation in follow-up CT. Three patients with normal CTP findings showed lacunar infarctions or normal findings on follow-up CT. In 1 patient, CTP did not reveal a territorial deficit above the imaging slice. The overall sensitivity and specificity of CTP for the detection of perfusion deficits in patients with proven territorial infarction (n = 18) on follow-up CT were 95% and 100%, respectively. The nAP(0) was significantly correlated with the National Institutes of Health Stroke Scale score at admission (P<.003) and the HLA(F) (P<.001). Different stroke patterns were identified in patients with follow-up CTP (n = 10): (1) initial perfusion deficit and partial nutritional reperfusion (nAP(0)>HLA(F); n = 6), (2) initial perfusion deficit and nonnutritional reperfusion (nAP( 0)>/=HLA(F); n = 2), and (3) initial perfusion deficit without reperfusion (nAP(0)>/=HLA(F); n = 2). CONCLUSIONS: Computed tomographic perfusion imaging detects major perfusion deficits in the middle cerebral artery territory. Because CTP is broadly available, it may play a role in acute stroke management. Arch Neurol. 2000;57:1161-1166     

Imaging of brain ischemia

The extent of the penumbra and the core of an acute ischemic stroke influence, at the given time, the impact of the recanalization of the occluded vessel on the outcome. Research studies have demonstrated that quantitative MR diffusion imaging and, to a lesser extent, CT perfusion (CTP) could provide an acceptable estimation of the size of the core, while perfusion imaging thresholds could outline critically hypoperfused regions. Several software programs now automatically process reliable quantitative diffusion-weighted imaging (DWI) and perfusion maps in real time, making them available for clinical routine. Studies investigating whether acute MRI profile could select patient for acute recanalization after the 4.5 h time window approved for rtPA administration are ongoing. Transient ischemic attack (TIA) is a major risk factor for stroke but its clinical diagnosis is difficult. MRI can confirm the ischemic nature of transient neurological symptoms among 50% of the patients and the presence of an acute diffusion lesion is an independent risk factor for acute stroke. Multimodal imaging of ischemic stroke and TIA provides a tissue-based characterization of the ischemic lesion that is dramatically influencing the diagnosis and the management of the patients.     

Unenhanced CT and acute stroke physiology

Unenhanced CT remains the most widely used imaging technique and is the standard of care for acute stroke evaluation. Early ischemic signs (EIS) within the first 3 to 6 hours of symptom onset (eg, parenchymal hypodensity, sulcal effacement, and dense vessel) have been advocated as a triage tool for thrombolytic therapy. Recent studies have challenged the relevance of these EIS within 3 hours of stroke onset, with advanced MR and CT methods increasingly competing with unenhanced CT as the primary imaging modality for acute ischemia. Nonetheless, the insights regarding acute stroke physiology provided by studying the CT evolution of early ischemic signs continue to be valuable for the informed interpretation of all stroke images. It is these insights that comprise the topic of this article.     

CT perfusion imaging in acute stroke

Computed tomographic perfusion (CTP) imaging is an advanced modality that provides important information about capillary-level hemodynamics of the brain parenchyma. CTP can aid in diagnosis, management, and prognosis of acute stroke patients by clarifying acute cerebral physiology and hemodynamic status, including distinguishing severely hypoperfused but potentially salvageable tissue from both tissue likely to be irreversibly infarcted ("core") and hypoperfused but metabolically stable tissue ("benign oligemia"). A qualitative estimate of the presence and degree of ischemia is typically required for guiding clinical management. Radiation dose issues with CTP imaging, a topic of much current concern, are also addressed in this review.     

Imaging of cerebral perfusion in acute stroke

Rapid imaging of cerebral perfusion in acute stroke is needed for timely triage of patients for thrombolytic therapy. Accurate quantitative perfusion imaging is required for proper assessment of penumbral brain parenchyma truly at risk for extension of infarction from the irreversible core infarction. CT and MRI techniques offer rapidity and availability for acute stroke imaging, including that of cerebral perfusion. CT perfusion techniques are readily available, but suffer from limited brain coverage of present multislice scanners. MRI offers whole brain coverage, but suffers from less availability and higher cost than CT. Presently, development is directed towards increasing the quantitative accuracy of cerebral perfusion imaging and validation of surrogate parameters, such as time to peak (TTP). In the future, the need for rapid and frequent assessment of cerebral perfusion and its metabolic correlates, with minimal or no radiation, will probably be met by MRI.     

Ischemic lesion typing on computed tomography perfusion and computed tomography angiography in hyperacute ischemic stroke: a preliminary study

The ability to rapidly and accurately evaluate the location and extent of hyperacute brain ischemia is of major clinical importance. Herein, we aimed to develop imaging criteria to classify the ischemic lesion by computed tomography (CT) perfusion (CTP) and CT angiography (CTA) in hyperacute ischemic stroke patient. Non-contrast-enhanced CT, CTP and CTA were performed in patients with symptoms of hyperacute stroke lasting <8 hours. According to the volume of infarct core, ischemic penumbra and vessel status, three ischemic lesion types were defined. Twenty-six patients were included in our study. Among them, ten patients were classified into severe group, 15 patients were classified into mild group and one patient was classified into reversible group. In acute stroke patients, the ischemic lesion typing may assist in individualizing therapeutic decisions for patients by possibly extending the window for giving thrombolytics beyond the current 3 hour limit.     

探讨急性缺血性卒中患者“一站式CT”检查的辐射安全问题

目的 评价急性缺血性卒中患者“一站式CT”检查的辐射剂量。方法 34例急性缺血性卒中患者（发病时间在3～9 h）进行了“一站式CT”检查。“一站式CT”检查包括CT平扫（un-enhanced CT head，NECT）、CT灌注（CT perfusion，CTP）及CT血管成像（CT angiography，CTA），记录扫描时机器显示的容积CT剂量指数（volume CT dose index，CTDIvol）及剂量长度乘积（dose-length product，DLP），DLP乘以头部的有效剂量系数得到有效剂量。结果 入组患者“一站式C T”检查的平均C T D I v o l为8 4 5.9 6±2 3.7 8 m G y，平均D L P为2748.92±129.25 mGy，总有效剂量范围5.96～7.81 mSv，平均为6.32±0.03 mSv，其中NECT有效剂量为2.14±0.27 mSv，CTP有效剂量为3.51 mSv，CTA有效剂量为0.67±0.07 mSv。2例患者CT平扫时出现移动伪影，补扫后导致此2例患者有效剂量较其他患者略高，分别为7.81 mSv、6.71 mSv。结论 急性脑缺血性卒中患者“一站式CT”检查参数设置符合美国食品及药物管理局推荐标准，安全、合理，并且能够指导急性缺血性卒中患者进行溶栓治疗。     

超薄多层螺旋CT与脑灌注成像在颅脑损伤早期诊断中的对比研究

目的探讨超薄多层螺旋CT和脑灌注成像在急性颅脑外伤(TBI)早期诊断中的临床应用价值。方法收集2010年12月~2012年10月我院收治的200例急性颅脑外伤患者检查资料,均于伤后6 h内行超薄多层螺旋CT(MSCT)和CT脑灌注成像(CTP)检查,全部病例于伤后2~3 d动态复查MSCT明确诊断,将数据进行回顾性分析,采用卡方检验评价。结果在MSCT与CTP这两种检测方法中,CTP在脑挫裂伤、硬膜下血肿和脑内血肿的诊断中优于超薄MSCT(P0.05),并且病灶周围低灌注区域大于超薄MSCT。结论 CTP对于急性颅脑外伤早期和微小损伤的诊断优于超薄MSCT,同时可以反映脑组织的灌注情况,具有可靠的临床价值。     

Xenon CT cerebral blood flow in acute stroke

Acute stroke therapy is evolving rapidly as research moves toward extending the time window for treatment so that more patients can benefit. As physiology-based imaging increasingly is used in patient selection, it is becoming evident that rigid time windows are not applicable to individual patients. Xenon CT has an important role in acute stroke therapeutic intervention as a quantitative, reproducible, rapid, and safe modality, which can provide valuable physiologic data that can optimize patient triage and aid in management.     

The evolving role of advanced MR imaging as a management tool for adult ischemic stroke: a Western-European perspective

New and more advanced diagnostic imaging techniques for acute stroke triage have the potential to not only improve the quality of care but also reduce health care costs. Although sufficiently large and methodologically sound studies with regard to cost effectiveness of MR imaging are lacking, the overall impression is that MR imaging has revolutionized not only the diagnosis but also the open and investigational management of neurologically ill patients.     

CT perfusion-guided versus time-guided mechanical recanalization in acute ischemic stroke patients

Objective

Perfusion studies are increasingly used to triage acute stroke patients for endovascular recanalization therapies. We compare the safety and efficacy of CT perfusion (CTP)-guided to time-guided mechanical recanalization in acute ischemic stroke (AIS) patients.

Methods

A review was conducted on 132 patients, 94 undergoing CTP-guided and 38 undergoing time-guided (maximum 8 h from symptom onset) mechanical recanalization at our institution.

Results

The rate of partial-to-complete recanalization did not differ between the CTP and the non-CTP group (78.7% vs. 81.6%, respectively, p = 0.71). ICH occurred respectively in 18.1% in the CTP group versus 31.6% in the non-CTP group (p = 0.06). The overall in-hospital mortality rate was significantly lower in the CTP group (15.9% vs. 36.8%, p = 0.04). In multivariable analysis, CTP-guided patient selection was an independent negative predictor of in-hospital mortality (OR = 3.2; p = 0.01). CTP-guided patient selection, however, was not a predictor of favorable outcome (Modified Rankin Scale 0–2 or 0–3).

Conclusions

CTP-based patient selection was associated with lower ICH and mortality rates. Favorable outcomes, however, did not differ between the 2 groups. These results may suggest a possible benefit in terms of in-hospital mortality with CTP-guided triage of AIS patients for endovascular treatment.     

Feasibility of deconvolution-based multiphase CT angiography perfusion maps in acute ischemic stroke: Simulation and concordance with CT perfusion

ObjectivesIntegration of CT perfusion (CTP) with requisite non-contrast CT and CT angiography (CTA) stroke imaging may allow efficient stroke lesion volume measurement. Using surrogate images from CTP, we simulated the feasibility of using multiphase CTA (mCTA) to generate perfusion maps and assess target mismatch profiles.Materials and methodsPatients with acute ischemic stroke who received admission CTP were included in this study. Four CTP images (surrogate mCTA, one pre-contrast and three post-contrast, starting at the arterial peak then at 8 s intervals) were selected according to the CTP arterial time-density curve to simulate non-contrast CT and mCTA images. Cerebral blood flow (CBF) and Tmax maps were calculated using the same model-based deconvolution algorithm for the standard CTP and surrogate mCTA studies. Infarct and penumbra were delineated with CBF < 20% and Tmax > 6 s threshold, respectively. Classification accuracy of surrogate mCTA target mismatch (infarct <70 ml; penumbra ≥15 ml; mismatch ratio ≥1.8) with respect to standard CTP was assessed. Agreement between infarct and penumbra volumes from standard CTP and surrogate mCTA maps were evaluated by Bland-Altman analysis.ResultsOf 34 included patients, 28 had target mismatch and 6 did not by standard CTP. Accuracy of classifying target mismatch profiles with surrogate mCTA was 79% with respect to that from standard CTP. Mean  ±  standard deviation of differences (standard CTP minus surrogate mCTA) of infarct and penumbra volumes were 9.8 ± 14.8 ml and 20.1 ± 45.4 ml, respectively.ConclusionsSurrogate mCTA ischemic lesion volumes agreed with those from standard CTP and may be an efficient alternative when CTP is not practical.     

Penumbra,the basis of neuroimaging in acute stroke treatment: Current evidence

In modern medicine brain imaging is an essential prerequisite not only to acute stroke triage but also to determining the specific therapy indicated. This article reviews the need for imaging the brain in acute stroke, penumbral pathophysiology, penumbral imaging techniques, as well as current status of various imaging modalities that are being employed to select patients for specific therapeutic approaches.     

Xenon-enhanced computed tomography cerebral blood flow measurements in acute cerebral ischemia: Review of 56 cases

Objective: Ischemic stroke must be diagnosed promptly if patients are to be treated with thrombolytic therapy. The diagnosis of acute cerebral ischemia, however, is usually based on clinical and computed tomography (CT) scan findings. CT scans are often normal in the first few hours after stroke. The purpose of this study was to determine whether Xenon-enhanced CT (XeCT) cerebral blood flow (CBF) studies could increase the sensitivity of stroke detection in the acute stage. Methods: CBF studies performed within 8 hours of symptom onset were evaluated in 56 patients who presented with hemispheric stroke symptoms. Mean CBF in the symptomatic vascular territory was calculated and compared with the corresponding contralateral area. CBF values below 18 mL/100g/min on 2 adjacent regions of interest were considered ischemic lesions. CT scans and angiograms were compared with the XeCt findings. Neurological condition on admission and discharge was evaluated by using National Institutes of Health Stroke Scale (NIHSS) scores. Results: The mean NIHSS score on admission was 12+/-5. Early CT scans were abnormal in 28 (50%) patients. There were 9 (16%) patients who had normal XeCT scans because of spontaneous reperfusion of the ischemic area. XeCT studies showed an ischemic lesion in 47 (84%) patients. In these patients, the mean CBF in the affected vascular territory was 16+/-8 mL/100g/min compared with 35+/-13 mL/100g/min in the contralateral specular territory (P<0.001). There were no false positive or negative XeCT studies, and the location of the perfusion defect corresponded with the CT and/or angiographic findings in all cases. Eight patients died (14%), and the 48 survivors (86%) had a mean NIHSS score of 9+/-6 on discharge. Conclusions: CBF measurements were correlated with the CT and angiographic results and greatly assisted in the diagnosis of acute ischemic stroke. XeCT studies used for estimating the location and extent of cerebral ischemia may be important in the triage of patients for acute stroke therapy.     

Diagnosis of lacunar infarcts within 6 hours of onset by clinical and CT criteria versus MRI.

BACKGROUND: The diagnosis of small deep infarcts (SDIs) based on clinical and noncontrast CT findings is often employed to triage stroke patients for emergent endovascular interventions. Few studies have evaluated the accuracy of <6 hours presentation with lacunar clinical syndromes in predicting the presence of a SDI and the absence of large vessel occlusion. METHODS: Consecutive patients were identified with symptoms suggestive of acute stroke, diffusion-weighted magnetic resonance imaging (DW-MRI) and CT performed within 6 hours of onset, and absence of hemorrhage on imaging. Patients were given a diagnosis of SDI if they met the defined clinical and CT criteria. Diagnoses of large vessel occlusion absent (LVOA) and final diagnoses of SDI versus non-SDI incorporated hyperacute multimodal MRI data. RESULTS: Of 64 patients, 15 were diagnosed as SDI at <6 hours based on clinical/CT criteria. Fourteen of 15 patients (93%) had a final diagnosis of LVOA. Ten of 15 (67%) had a final MR-DWI-confirmed diagnosis of SDI. Clinical/CT diagnosis of SDI showed sensitivity of 44%, specificity 97%, positive predictive value (PPV) 93%, and negative predictive value (NPV) of 61% in predicting LVOA and sensitivity 83%, specificity 90%, PPV 67%, and NPV 96% compared to the final diagnosis of SDI. Most patients incorrectly diagnosed with SDIs harbored small cortical branch infarcts. CONCLUSIONS: Diagnoses of SDI <6 hours from symptom onset based on a classic lacunar syndrome and CT criteria show only modest predictive value in predicting the presence of a small-vessel territory infarct but perform fairly well in identifying patients without large-vessel occlusions amenable to endovascular therapy.     

Brain Imaging Using Mobile CT: Current Status and Future Prospects

Computed tomography (CT) is an invaluable tool in the diagnosis of many clinical conditions. Several advancements in biomedical engineering have achieved increase in speed, improvements in low‐contrast detectability and image quality, and lower radiation. Portable or mobile CT constituted one such important advancement. It is especially useful in evaluating critically ill, intensive care unit patients by scanning them at bedside. A paradigm shift in utilization of mobile CT was its installation in ambulances for the management of acute stroke. Given the time sensitive nature of acute ischemic stroke, Mobile stroke units (MSU) were developed in Germany consisting of an ambulance equipped with a CT scanner, point of care laboratory system, along with teleradiological support. In a radical reconfiguration of stroke care, the MSU would bring the CT scanner to the stroke patient, without waiting for the patient at the emergency room. Two separate MSU projects in Saarland and Berlin demonstrated the safety and feasibility of this concept for prehospital stroke care, showing increased rate of intravenous thrombolysis and significant reduction in time to treatment compared to conventional care. MSU also improved the triage of patients to appropriate and specialized hospitals. Although multiple issues remain yet unanswered with the MSU concept including clinical outcome and cost‐effectiveness, the MSU venture is visionary and enables delivery of life‐saving and enhancing treatment for ischemic and hemorrhagic stroke. In this review, we discuss the development of mobile CT and its applications, with specific focus on its use in MSUs along with our institution's MSU experience.     

Single-Centre Experience with Patients Selection for Mechanical Thrombectomy Based on Automated Computed Tomography Perfusion Analysis–A Comparison with Computed TomographyCT Perfusion Thrombectomy Trials

Background: In randomized clinical trials, mechanical thrombectomy (MT) was proved to be a highly effective treatment of acute ischemic stroke which improved clinical outcomes. Some of the trials used automated computed tomography perfusion (CTP) analysis for selection of participants. We present a single-center experience with CTP selection and comparison with CTP trials. Methods: Data of consecutive MT patients (from January 2016 to December 2017) were retrospectively reviewed. All patients with multiphase CT angiography confirmed the presence of anterior circulation large vessel occlusion/s in the intracranial internal carotid artery and/or middle cerebral artery (M1 or M2) and with admission brain CTP analyzed by RAPID software were included into the analysis. Results: Sixty-two patients fulfilled the inclusion criteria (mean age was 70.1 ± 13.6 years, females 48.5%). At baseline, National Institutes of Health Stroke Scale score was 16 (IQR?=?13-20), Alberta Stroke Program Early CT Score (ASPECTS) was 8 (IQR?=?7-9), CTP core volume was 20 mL (IQR?=?2-36), and CTP penumbra volume was 145.5 mL (IQR?=?107-184). Time from stroke onset to imaging was 1 hour 32 minutes, time from stroke onset to reperfusion was 3 hours 50 minutes, and median time from CT to reperfusion was 1 hour 56 minutes. Modified thrombolysis in cerebral infarction 2b/3 was achieved in 42 patients (67.7%). Twenty-three patients (37%) had modified Rankin scale 0-2 at 90 days. Conclusions: Our analysis of CTP-selected patients for MT supports clinical applicability of automated CTP analysis into everyday clinical practice.