Perfusion CT and angio CT in the assessment of acute stroke

Effectiveness of computed tomography perfusion imaging in stroke management

Objectives

Current guidelines do not support the use of computed tomography perfusion (CTP) in stroke, except when identifying the penumbra during an extended treatment window. Therefore, this study aimed to define the yield of CTP in diagnosing a stroke diagnosis beyond the imaging of the penumbra in the hyperacute phase (0-6 h) and an extended time window (6-24 h).

Materials and methods

All consecutive patients with acute onset of symptoms within a 24-h window underwent CTP imaging. The diagnostic value of CTP was calculated against the clinical and radiological diagnoses of stroke. A positive CTP result was determined by the presence of either a core or penumbra on the RAPID summary. Clinical diagnoses corresponded to discharge diagnoses of stroke. A radiological diagnosis was established if early ischemic changes [Alberta Stroke Program Early CT Score (ASPECTS) <10] were observed on the baseline CT scan, acute infarction was confirmed on follow-up imaging, or symptomatic occlusion was evident on baseline CTA.

Results

Between November 2018 and November 2019, 585 consecutive patients with an acute neurological deficit underwent multimodal CT imaging. A total of 500 patients (85%) were included, where 274 (55%) were within the hyperacute phase, 153 (31%) had a radiological diagnosis of stroke, and 122 (24%) had a clinical diagnosis of stroke. CTP yielded positive results only in patients with a confirmed stroke (positive predictive value and specificity of 100%). When CTP results were negative, 43% of the cases turned out to stroke mimics. Patients with stroke mimics were younger (66 ± 17 vs. 73 ± 13) and had lower scores on the National Institutes of Health Stroke Scale [median 0; interquartile range (IQR) 0-2 vs. median 4; IQR 2-6] compared to patients with CTP-negative strokes.

Conclusion

In our study, CTP consistently indicated brain ischemia; therefore, in stroke management, CTP is most beneficial when it yields a positive result. A positive CTP result should prompt adequate stroke management actions without any delay. Conversely, a negative CTP result necessitates the consideration of both stroke and non-stroke diagnoses.

Quantitative Analysis of Brain CT Perfusion in Healthy Beagle Dogs: A Pilot Study

Brain computed tomography (CT) perfusion is a technique that allows for the fast evaluation of cerebral hemodynamics. However, quantitative studies of brain CT perfusion in veterinary medicine are lacking. The purpose of this study was to investigate the normal range of perfusion determined via CT in brains of healthy dogs and to compare values between white matter and gray matter, differences in aging, and each hemisphere. Nine intact male beagle dogs were prospectively examined using dynamic CT scanning and post-processing for brain perfusion. Regional cerebral blood volume (rCBV), regional cerebral blood flow (rCBF), mean transit time, and time to peak were calculated. Tissue ROIs were drawn in the gray matter and white matter of the frontal, temporal, parietal, and occipital lobes; caudate nucleus; thalamus; piriform lobe; hippocampus; and cerebellum. Significant differences were observed between the white matter regions and gray matter regions for rCBV and rCBF (p < 0.05). However, no significant differences were identified between hemispheres and between young and old groups in brain regions. The findings obtained in this study involving healthy beagle dogs might serve as a reference for regional CT perfusion values in specific brain regions. These results may aid in the characterization of various brain diseases in dogs.

Contrast-Induced Acute Kidney Injury in Radiologic Management of Acute Ischemic Stroke in the Emergency Setting

BACKGROUND AND PURPOSE

The use of invasive cerebral angiography with CTA for active treatment of patients with suspected ischemic strokes has been increasing recently. This study aimed to identify the incidence of postcontrast acute kidney injury using baseline renal function when CTA and cerebral angiography were performed sequentially.

MATERIALS AND METHODS

This retrospective observational study evaluated adults (18 years of age or older) with ischemic stroke who underwent CTA and cerebral angiography sequentially between 2010 and 2018. The incidence of postcontrast acute kidney injury was determined using the baseline estimated glomerular filtration rate. The value of the baseline estimated glomerular filtration rate at which the occurrence of postcontrast acute kidney injury increased was also determined.

RESULTS

Postcontrast acute kidney injury occurred in 57/601 (9.5%) patients. Those with a baseline estimated glomerular filtration rate of <30 mL/min/1.73 m² showed a higher incidence of acute kidney injury. Age, chronic kidney disease, medication (nonsteroidal anti-inflammatory drugs, angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, β blockers, statins, and insulin) use following contrast media exposure, and serum albumin affected the incidence of postcontrast acute kidney injury. The incidence of postcontrast acute kidney injury increased when the baseline estimated glomerular filtration rate was <43 mL/min/1.73 m².

CONCLUSIONS

Patients with low baseline renal function had the highest incidence of postcontrast acute kidney injury after CTA and cerebral angiography, but no fatal adverse effects were documented. Thus, patients suspected of having a stroke should be actively managed with respect to neurovascular function.

Relative Cerebral Blood Transit Time Decline and Neurological Improvement in Patients After Internal Carotid Artery Stenting

In this study we hypothesized that the alleviation of neurological symptoms long after internal carotid artery (ICA) stenting may be related to sustained improvement of cerebral perfusion. Thirty-four subjects (F/M; 15/19) with >70% stenosis of a single internal carotid artery and neurological symptoms, who underwent a carotid artery stenting procedure, were studied. Brain computed tomography perfusion (CTP) imaging was performed before and 3 years after ICA stenting. The following relative variables were compared: cerebral blood flow (rCBF), cerebral blood volume (rCBV), mean transit time (rMTT), time to peak (rTTP), and permeability surface area product (rPS). A survey also was conducted to compare the patients' clinical symptoms. Overall, we found that a trend toward rMTT decline was the only persisting change after ICA stenting. We then stratified the patients into the subgroups of <2%, 2-5%, and > 5% rMTT decline and found that those with a rMTT decline >2% reported a prominent reduction in subjective clinical symptoms such as headache, dizziness, tinnitus, blurred vision, transient blindness, a sense of gravity of the head, and pain in the eyeballs. We conclude that a shortened mean rMTT, likely reflecting improved cerebral microcirculation, underlies the improvement of neurological symptoms in patients with ICA stenosis.

CT cervico-cerebral angiography in acute stroke. Can we justify aortic arch imaging?

OBJECTIVES

Computed tomography cervico-cerebral angiography (CTCCA) plays a pivotal role in the evaluation of acute stroke. Currently no evidence justifies the inclusion of the upper chest in the CTCCA field of view. The aim of this study was to assess the prevalence and clinical significance of vascular findings identified on CTCCA in the head, neck, and upper chest regions in patients presenting with acute stroke symptoms.

METHODS

A retrospective review of radiology images and reports of 900 consecutive patients (425 men, 475 women; mean age 63.2 years, age range 19-99 years) with a suspected acute stroke who underwent CTCCA in the emergency department between January 2011 and July 2016. Clinically significant vascular CTCCA findings were recorded for each patient within the head, neck, and upper chest regions, respectively.

RESULTS

Of the 900 patients, clinically significant vascular CTCCA findings were identified in 404/900 (44.8%) patients. 218/900 (24.2%) were located within the head region; 174/900 (19.3%) within the neck; and 12/900 (2.4%) in the upper chest. Of the 12 vascular findings located within the upper chest, 3/900 (0.33%) were related to a clinically significant posterior circulation infarct.

CONCLUSIONS

Routine inclusion of the upper chest on CTCCA is currently difficult to justify in the evaluation of a suspected acute anterior circulation stroke, contributing significantly to total radiation dose without demonstrating significant extra-cranial vascular findings. Prospective studies adopting narrower fields of view excluding the upper chest are necessary.

Comparative accuracy of CT perfusion in diagnosing acute ischemic stroke: A systematic review of 27 trials

OBJECTIVE

To systematically evaluate and compare the diagnostic accuracy of CT perfusion (CTP), non-enhanced computed tomography (NCCT) and computed tomography angiography (CTA) in detecting acute ischemic stroke.

METHODS

We searched seven databases and screened the reference lists of the included studies. The risk of bias in the study quality was assessed using QUADASII. We produced paired forest plots in RevMan to show the variation of the sensitivity and specificity estimates together with their 95% CI. We used a hierarchical summary ROC model to summarize the sensitivity and specificity of CTP in detecting ischemic stroke.

RESULTS

We identified 27 studies with a total of 2168 patients. The pooled sensitivity of CTP for acute ischemic stroke was 82% (95% CI 75-88%), and the specificity was 96% (95% CI 89-99%). CTP was more sensitive than NCCT and had a similar accuracy with CTA. There were no statistically significant differences in the sensitivity and specificity between patients who underwent CTP within 6 hours of symptom onset and beyond 6 hours after symptom onset. No adverse events were reported in the included studies.

CONCLUSIONS

CTP is more accurate than NCCT and has similar accuracy to CTA in detecting acute ischemic stroke. However, the evidence is not strong. There is potential benefit of using CTP to select stroke patients for treatment, but more high-quality evidence is needed to confirm this result.

Dynamic cerebral autoregulation following acute ischaemic stroke: Comparison of transcranial Doppler and magnetic resonance imaging techniques

Novel MRI-based dynamic cerebral autoregulation (dCA) assessment enables the estimation of both global and spatially discriminated autoregulation index values. Before exploring this technique for the evaluation of focal dCA in acute ischaemic stroke (AIS) patients, it is necessary to compare global dCA estimates made using both TCD and MRI. Both techniques were used to study 11 AIS patients within 48 h of symptom onset, and nine healthy controls. dCA was assessed by the rate of return of CBFV (Rturn) following a sudden drop induced by the thigh cuff manoeuvre. No significant between-hemisphere differences were seen in controls using either the TCD or MRI technique. Inter-hemisphere averaged Rturn values were not different between TCD (1.89 ± 0.67%/s) and MRI (2.07 ± 0.60%/s) either. In patients, there were no differences between the affected and unaffected hemispheres whether assessed by TCD (Rturn 0.67 ± 0.72 vs. 0.98 ± 1.09%/s) or MRI (0.55 ± 1.51 vs. 1.63 ± 0.63%/s). Rturn for both TCD and MRI was impaired in AIS patients compared to controls in both unaffected and affected hemispheres (ANOVA, p = 0.00005). These findings pave the way for wider use of MRI for dCA assessment in health and disease.

Prevalence and clinical significance of extravascular incidental findings in patients undergoing CT cervico-cerebral angiography

INTRODUCTION

CT cervico-cerebral angiography (CTCCA) is now the first line diagnostic imaging modality for the majority of vascular pathologies of the head and neck with diagnostic value comparable to or better than traditional angiographic techniques. The aim of this study was to assess the prevalence, clinical significance and management of extravascular incidental findings detected on CTCCA.

MATERIALS AND METHODS

A retrospective review of the CTCCA reports of 302 consecutive patients from 2009 to 2013 was undertaken. Extravascular incidental findings were classified, according to an adaptation of the CT colonography data and reporting system (CRADS), as EV1-EV4. EV1=no incidental findings, EV2=clinically insignificant incidental finding, EV3=incidental finding of intermediate clinical significance, EV4=highly clinically significant finding. Follow up of the electronic medical records of patients with EV3 or EV4 findings was undertaken to determine subsequent management.

RESULTS

Potentially clinically significant findings were demonstrated in 14.2% of patients with 8.6% of patients having a highly clinically significant finding. 4 incidental findings were confirmed to be malignant lesions and 5 required acute intervention. In addition 19% of patients with highly clinically significant incidental findings did not receive appropriate follow up.

DISCUSSION

This study has demonstrated the presence of clinically important incidental findings in a significant proportion of patients undergoing CTCCA with a significant minority of these patients not receiving follow up. A standardised method of reporting incidental findings, such as that used in this paper, would aid radiologists and referring physicians in recording and communicating these findings.

The combined treatment of stenting and surgery in a giant unruptured aneurysm of the middle cerebral artery

BACKGROUND

This case study reports on a combined therapy of stenting and surgery for a giant unruptured middle cerebral artery (MCA) aneurysm with the aim of preserving the patency of the vessel during surgery.

CASE DESCRIPTION

A 51-year-old male presented with a sudden onset of moderate left hemiparesis and dysarthria. Neuro-radiological evaluations showed a giant right unruptured MCA aneurysm without subarachnoid hemorrhage (SAH). The cerebral angiography confirmed the presence of such an aneurysm producing compression of both M2 branches with consequent slowing of the blood flow. Two weeks later, the patient underwent the positioning of an Enterprise stent and inside this, a flow diverter Silk stent. They were placed across the aneurysm and in one of the two M2 branches with the aim of protecting them during surgical manipulation. The patient went immediately to surgery, where the aneurysm was resected and both M2 branches decompressed.

CONCLUSION

The combined placement of the stents allowed safe and successful surgical dissection of the M2 branches and clipping of the aneurysm without interrupting the blood flow.

Saving the ischemic penumbra: endovascular thrombolysis versus medical treatment

Endovascular thrombolysis may allow rapid arterial recanalization in patients with acute ischemic stroke. We present the first study to our knowledge comparing the ischemic penumbra saved with endovascular versus medical therapy. A retrospective review of 21 patients undergoing endovascular intervention for stroke from 2010 to 2011 was contrasted with 21 consecutive patients treated with antiplatelet agents alone. Immediate computed tomography perfusion (CTP) scan of the head and neck was obtained in all patients. Patients with lacunar and posterior circulation infarcts, and those who were medically unstable for MRI post-operatively were excluded. CTP and MRI underwent volumetric calculation. CTP penumbra was correlated with diffusion restriction volumes on MRI, and an assessment was made on the volume of ischemic burden saved with either endovascular treatment or antiplatelet agents. The median age was 70 years (interquartile range 62-80). Median National Institutes of Health Stroke Scale score was 18 and 14 in the control and endovascular groups, respectively. Intravenous tissue plasminogen activator was administered in 22 of 42 patients (52%). Median penumbra calculated was 32,808 mm(3) in the control group and 46,255 mm(3) in the endovascular group. Median penumbra spared was 9550 mm(3) (4980-18,811) in the control group versus 38,155 mm(3) in the endovascular group (p=0.0001). Endovascular thrombolysis may be more efficient than medical therapy alone in saving ischemic penumbra. Future advances in recanalization techniques will further improve the efficacy of endovascular therapy.

The study of fetal-type posterior cerebral circulation on multislice CT angiography and its influence on cerebral ischemic strokes

PURPOSE

The purpose was to evaluate if patients with partial and full fetal-type posterior cerebral artery (PCA) could be more prone to lead to ischemic strokes on multislice computed tomographic angiography (MSCTA).

METHODS

A total of 202 patients who had undergone MSCTA examinations were divided into three groups: patients with full fetal-type posterior (FTP), patients with partial FTP, and patients without FTP. The odds ratio of having ischemic strokes was calculated.

RESULTS

The odds of having ischemic strokes in patients with full and partial FTP were 1.448 and 3.027, while P values were .391 and .0307, respectively.

CONCLUSION

Patients with a partial fetal-type PCA could be more prone to develop ischemic strokes.

Does modern ischemic stroke therapy in a large community-based dedicated stroke center improve clinical outcomes? A two-year retrospective study

BACKGROUND

To compare modern endovascular therapies in the acute ischemic stroke patients leading to more comprehensive acute stroke algorithm.

METHODS

A 2-year retrospective nonrandomized study on 76 patients who were placed into 5 different treatment groups for acute ischemic stroke. These groups included: group 1 (no treatment) (n = 24), group 2 (intravenous tissue plasminogen activator [tPA] only) (n = 18), group 3 (intra-arterial [IA] tPA) (n = 9), group 4 (Mechanical Embolus Removal in Cerebral Ischemia [MERCI]; retrieval only) (n = 17), and group 5 (combined IA/MERCI) (n = 8). Age range for all groups was 29-92 years. There were 39 women (51.3%) and 37 men (48.7%). The mean age for all patients was 70.1 years. The pre- and post-National Institutes of Health Stroke Scale (NIHSS) values were obtained for each group on arrival and discharge from the hospital. The results of the 4 treatment cohorts were compared with the no treatment group, providing the relative efficacy of these procedures compared with conservative medical therapy alone.

RESULTS

Group 1 presented with an admission NIHSS value of 11.1 and 8.9 on discharge from the hospital. There was a NIHSS reduction of 2.2 without treatment. Group 2 had an admission NIHSS value of 11.8 and a discharge value of 4.7, resulting in an NIHSS reduction of 7.1. Group 3 had an admission NIHSS value of 16.1 and 7.4 at discharge, resulting in an NIHSS reduction of 8.7. Group 4 had an admission NIHSS value of 15.9 and discharge NIHSS value of 3.1, with an NIHSS reduction of 12.8. Group 5 had an admission NIHSS score of 15.7 and 10.6 at discharge, with an NIHSS reduction of 5.1. Four patients expired during their admission, 2 from group 1 (control group) and 2 from group 5 (combined IA/MERCI group). There was a statistically significant difference for the 5 groups at the P < .05 level in change in NIHSS scores: F (4, 24) = 9.10, P = .000.

CONCLUSIONS

Modern endovascular therapies for acute ischemic stroke do improve clinical outcomes when implemented in the setting of a dedicated comprehensive stroke team.

Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association

BACKGROUND AND PURPOSE

The authors present an overview of the current evidence and management recommendations for evaluation and treatment of adults with acute ischemic stroke. The intended audiences are prehospital care providers, physicians, allied health professionals, and hospital administrators responsible for the care of acute ischemic stroke patients within the first 48 hours from stroke onset. These guidelines supersede the prior 2007 guidelines and 2009 updates.

METHODS

Members of the writing committee were appointed by the American Stroke Association Stroke Council's Scientific Statement Oversight Committee, representing various areas of medical expertise. Strict adherence to the American Heart Association conflict of interest policy was maintained throughout the consensus process. Panel members were assigned topics relevant to their areas of expertise, reviewed the stroke literature with emphasis on publications since the prior guidelines, and drafted recommendations in accordance with the American Heart Association Stroke Council's Level of Evidence grading algorithm.

RESULTS

The goal of these guidelines is to limit the morbidity and mortality associated with stroke. The guidelines support the overarching concept of stroke systems of care and detail aspects of stroke care from patient recognition; emergency medical services activation, transport, and triage; through the initial hours in the emergency department and stroke unit. The guideline discusses early stroke evaluation and general medical care, as well as ischemic stroke, specific interventions such as reperfusion strategies, and general physiological optimization for cerebral resuscitation.

CONCLUSIONS

Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke remains urgently needed.

Systematic combined noncontrast CT-CT angiography in the management of unexplained nontraumatic coma

BACKGROUND

Nontraumatic impaired consciousness is a common issue in emergency departments with a serious but widely variable prognosis.

STUDY OBJECTIVES

The aim of this prospective study was to evaluate the ability of systematic combined noncontrast computed tomography (NCCT)/computed tomography angiography (CTA) imaging, firstly to provide a neurologic prognosis and secondly to ensure early detection of basilar artery occlusion (BAO), in unexplained nontraumatic impaired consciousness management.

METHODS

Combined NCCT/CTA imaging was performed on 65 patients with impaired consciousness and no history of trauma prospectively over 14 months in a single center. Images were assessed based on visual and quantitative criteria. Clinical outcome was assessed using the modified Rankin Scale at 3 months. Statistical analysis aimed to identify the prognostic value of combined NCCT/CTA imaging and its ability for early BAO detection.

RESULTS

This study shows that combined NCCT/CTA imaging was a significant predictor of poor neurological outcome, with a positive predictive value of 94.6%. The combination was also crucial for early detection of BAO, given that 42.8% of cases were misdiagnosed with NCCT alone. Basilar artery occlusion represented 10.8% of all unexplained nontraumatic impaired consciousness.

CONCLUSIONS

Systematic combined NCCT/CTA imaging is an efficient tool for predicting poor neurologic prognosis in cases of unexplained nontraumatic impaired consciousness and is also essential for detecting BAO.

Dual-energy CT: vascular applications

OBJECTIVE

Dual-energy CT permits a variety of image reconstructions for the depiction and characterization of vascular disease. Techniques include visualization of low- and high-peak-kilovoltage spectra image datasets and also material-specific reconstructions combining both low- and high-peak-kilovoltage data.

CONCLUSION

This article focuses on four main vascular areas: the aorta, the major visceral, lower limb, and cervical arteries. For each territory, the current status, potential advantages, and limitations of these techniques are described.

Intra-arterial thrombolysis: tissue plasminogen activator and other thrombolytic agents

Recanalization rates with the administration of intravenous tissue plasminogen activator in acute ischemic stroke are low. Adjuvant endovascular techniques that achieve recanalization by direct intra-arterial (IA) delivery of thrombolytics, mechanical clot retrieval, clot aspiration, and stenting may complement intravenous pharmacotherapy. IA thrombolytics can be administered within 6 hours of symptom onset in anterior circulation strokes and within 24 hours in posterior circulation strokes. This review describes the indications, patient selection, and technique for IA administration of thrombolytics.

Usefulness of CT angiography for therapeutic decision making in thrombolyzing intubated patients with suspected basilar artery thrombosis

BACKGROUND AND AIMS

Acute ischemic stroke (AIS) due to basilar artery thrombosis (BAT) causes high mortality and severe disability. Early neurological assessment and timely thrombolysis might improve outcome. BAT is difficult to diagnose due to wide spectrum of presentation and decreased conscious level. Emergency physicians often intubate BAT patients with airway compromise before arrival of stroke neurologist. We evaluated role of computerized tomography (CT) angiography (CTA) of brain and cervical arteries in early diagnosis of acute BAT in intubated patients and facilitating decision for thrombolysis.

METHODS

Consecutive AIS patients presenting between 2007 and 2009 within 6 hours of symptom onset, with sudden deterioration in conscious level and intubation before assessment by neurologist, were included. All patients underwent brain CT and CTA. Outcomes were assessed at 3 months.

RESULTS

Thrombolytic therapy, mainly intravenous tissue plasminogen activator (IV-TPA), was administered to 161 (8.4%) of 1,917 AIS patients during the study period. Acute BAT contributed 10.9% of our cohort. CTA was performed in 152 (94.4%) patients and the rest were excluded due to their impaired renal functions. Five patients (3 males, mean age 72 years) presenting with acute obtundation and airway compromise were intubated, sedated, and paralyzed before assessment by neurologist. CTA showed BAT in all. IV-TPA was initiated at 213 ± 59 minutes in 4 patients while 1 received intraarterial thrombolysis at 13 hours. There was no intracranial hemorrhage. Mean length of hospital stay was 11.8 days. Despite severe stroke at presentation, good functional recovery at 3 months (modified Rankin scale [mRS] 1) occurred in 2 patients; mRS 4 in 1, and 2 died.

CONCLUSION

In patients with BAT, intubated before assessment by neurologist, CTA might help in confirming the diagnosis and facilitating therapeutic decision making for initiating thrombolysis.

[Traumatic dissection of carotid arteries caused by high energy motorcycle accident]

Injuries of internal carotid arteries caused by high energy trauma are rare but often combined with poor outcome. Blunt trauma to the head and neck as well as the use of newer motorcycle helmets together with crash circumstances should promptly lead to a differentiated polytrauma management with expansion of radiologic diagnostics. This could lead to a reduction of overlooked dissections and an increase in promptly and correctly treated injuries.

Singapore ministry of health clinical practice guidelines on stroke and transient ischemic attacks

The primary aim of these guidelines is to assist individual clinicians, hospital departments, and hospital administrators to produce local protocols for the: • assessment, investigation and immediate management of individuals with a transient ischemic attack or acute stroke (other than sub-arachnoid hemorrhage), and • secondary prevention and risk factor management following a transient ischemic attack or acute stroke. The secondary aim of these guidelines is to suggest methods for implementation and clinical audit. The workgroup preparing these guidelines was formed by the Ministry of Health, Singapore. It comprised healthcare workers from relevant specialties, family medicine, nursing, occupational therapy, and a lay patient advocate. The Scottish Intercollegiate Guidelines Network's Clinical Practice Guidelines on the Management of Patients with Stroke were reviewed, updated, and modified to meet local needs. The final guidelines are made up of evidence-based recommendations covering the following areas - assessment, investigation, immediate management, secondary prevention, rehabilitation, and implications for service delivery. The guidelines were sent to professional organizations for comments and endorsements. The final version was circulated to all medical practitioners in Singapore. It is hoped that the guidelines will improve the care of patients with stroke and transient ischemic attack. Clinical quality improvement measures are proposed.

Assessment of collateral flow with multi-phasic CT: correlation with diffusion weighted MRI in MCA occlusion

PURPOSE

To correlate collateral flow on multiphasic contrast enhancement computed tomography (CT) and graded ischemic changes on diffusion weighted MR in patients with acute middle cerebral artery (MCA) infarction.

MATERIALS AND METHODS

A retrospective evaluation of diffusion weighted images (DWIs) and three phasic contrast enhanced CT (CECT) was performed on 11 patients with MCA occlusions. The area of ischemic change on DWIs was graded according to the Alberta Stroke Program Early CT Score (ASPECTS) criteria. To evaluate collateral flow on three phasic CECT, we counted the number of contrast enhancing MCA branches distal to the occlusion site at the sylvian fissure from predetermined axial images. The collateral ratios of counted numbers to those at the normal side were calculated at each phase (CR1, CR2, CR3). We then compared collateral ratios from the three phasic CECT with ASPECTS data from DWIs.

RESULTS

Collateral ratios from the three phasic CECT were determined to be CR1 .48 ± .27, CR2 .73 ± .36 and CR3 .72 ± .30. We discovered a correlation between both the CR2 and ASPECTS (r= .675, P= .023) and the CR3 and ASPECTS (r= .664, P= .026).

CONCLUSION

The number of contrast enhancing branches distal to the MCA occlusion, as counted in the sylvian fissure on later phase images of multiphasic CECT, reflects the status of collateral flow, and correlates with ASPECTS on DWIs.

Optimal brain perfusion CT coverage in patients with acute middle cerebral artery stroke

BACKGROUND AND PURPOSE

PCT has emerged as an alternative to MR imaging for the assessment of patients with suspected acute stroke. However, 1 disadvantage of PCT is its limited anatomic coverage, which may impact the characterization of hemispheric ischemic strokes. The purpose of this study was to determine the optimal brain CT coverage required to accurately estimate the size of the infarct core relative to the MCA territory and the infarct-penumbra mismatch, by using a criterion standard of these parameters measured on PCT with 80-mm z-axis coverage.

MATERIALS AND METHODS

Fifty-one patients with acute ischemic hemispheric stroke underwent PCT scanning (2 boluses, total coverage of 80 mm, 16 x 5 mm sections) within the first 24 hours of symptom onset and a follow-up NCCT of the brain between 3 days and 3 months after the initial stroke CT study. The volumes of PCT infarct and penumbra for each possible extent of z-axis coverage derived from the individual PCT sections were recorded (beginning with 5 mm of z-axis coverage above the orbits and then increasing the coverage in 5-mm increments in the z-axis up to 80 mm above the orbits). The infarct-penumbra mismatch and the size of the infarction relative to the MCA territory were calculated for each extent of z-axis coverage. Using the 80-mm z-axis coverage as the criterion standard, we calculated the accuracy of the values of the relative PCT infarct size and mismatch that were obtained by using more limited z-axis coverage. The impact of different levels of PCT z-axis coverage on the eligibility for reperfusion treatment was assessed.

RESULTS

On the admission PCT, by using 80-mm of z-axis coverage, the mean perfusion infarct core volume was 45.9 +/- 44.0 cm(3) (range, 0-170 cm(3)) and the mean penumbra volume was 64.5 +/- 64.4 cm(3) (range, 0-226 cm(3)). The mean perfusion infarct core/MCA territory ratio was 19.6% +/- 16.2% (range, 0.1%-56%). The penumbra / (infarct + penumbra) ratio was 68.6% +/- 23.6% (range, 16.4%-100%). The final infarct volume on follow-up NCCT was 115.4 +/- 157.3 cm(3) (range, 1.79-647.4 cm(3)). The minimal z-axis PCT coverage required to obtain values similar to those obtained with 80-mm z-axis coverage was 75 mm for a mismatch of 0.5, fifty millimeters for a mismatch of 0.2, and 55 mm for a size of PCT infarct relative to the MCA territory.

CONCLUSIONS

Seventy-five millimeters is the minimal PCT coverage required to use PCT as a tool to select patients with acute stroke for reperfusion therapy by using a mismatch of 0.5. A z-axis coverage of 50 mm was sufficient for a mismatch of 0.2; and 55 mm, for the size of PCT infarct relative to MCA territory (one-third or more).

Developments in neuroimaging for acute ischemic stroke: diagnostic and clinical trial applications

Over the past several years, active investigation into neuroimaging in the setting of acute ischemic stroke has improved our understanding of and ability to visualize the dynamic pathophysiology of acute cerebrovascular disease. Efforts surrounding the application of multimodal CT and MRI have resulted in a growing body of data from systematic evaluations of different parameters, experience in the use of these techniques in guiding clinical decision making, and clinical trials employing neuroimaging for patient selection, for proof of principle, and as a surrogate outcome measure.

CT perfusion identifies increased salvage of tissue in patients receiving intravenous recombinant tissue plasminogen activator within 3 hours of stroke onset

BACKGROUND AND PURPOSE

In spite of the advent of thrombolytic therapy, CT-perfusion imaging is currently not fully used for clinical decision-making and not included in published clinical guidelines for management of ischemic stroke. We investigated whether lesion volumes on cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) maps predict final infarct volume and whether all these parameters are needed for triage to intravenous recombinant tissue plasminogen activator (rtPA). We also investigated the effect of intravenous rtPA on affected brain by measuring salvaged tissue volume in patients receiving intravenous rtPA and in controls.

MATERIALS AND METHODS

Forty-four patients receiving intravenous rtPA and 19 controls underwent CT perfusion (CTP) studies in the emergency department within 3 hours of stroke onset. Lesion volumes were measured on MTT, CBV, and CBF maps by region-of-interest analysis and were compared with follow-up CT volumes by correlation and regression analysis. The volume of salvaged tissue was determined as the difference between the initial MTT and follow-up CT lesion volumes and was compared between intravenous rtPA-treated patients and controls.

RESULTS

No significant difference between the groups was observed in lesion volume assessed from the CTP maps (P > .08). Coefficients of determination for MTT, CBF, and CBV versus follow-up CT lesion volumes were 0.3, 0.3, 0.47, with intravenous rtPA; and 0.53, 0.55, and 0.81 without intravenous rtPA. Regression of MTT on CBF lesion volumes showed codependence (R(2) = 0.98, P < .0001). Mean salvaged tissue volumes with intravenous rtPA were 21.8 +/- 17.1 and 13.2 +/- 13.5 mL in controls; these were significantly different by using nonparametric (P < .03) and Fisher exact tests (P < .04).

CONCLUSIONS

Within 3 hours of stroke onset, CBV lesion volume does not necessarily represent dead tissue. MTT lesion volume alone can be used to identify the upper limit of the size of abnormally perfused brain. More brain is salvaged in patients with intravenous rtPA than in controls.

Value of automatic bone subtraction in cranial CT angiography: comparison of bone-subtracted vs. standard CT angiography in 100 patients

Non-contrast-enhanced cranial computed tomography (NECT) and CT angiography (CTA) are the most frequently used modalities in the triage of patients with acute ischemic and hemorrhagic stroke. CTA bone removal can improve the delineation of vasculature closely adjacent to bony structures, which is sometimes limited in standard CTA. The aim of this study was the evaluation of the clinical benefit of bone subtraction (BS) regarding delineation of cerebral vasculature, reading time and depiction of vascular pathologies compared to standard CTA without BS. A total of 100 patients who underwent NECT and supraaortic CTA on a 64-slice CT system were retrospectively included in the study. Bone removal was performed by subtraction of the NECT data from the CTA data using a dedicated workstation. Standard and BS CTA of each patient was reviewed for delineation of cerebral vasculature (grading scale from 1 = "excellent delineation" to 10 = "hardly any delineation"), reading time and depiction of vascular pathologies (standardized catalog) by two blinded readers. For BS data sets, the quality of BS was rated by a combination of the criteria complete bone removal, depiction of vascular structures and sufficient quality for diagnostic evaluation. The use of BS significantly reduced reading time from 4.60 min to 3.49 min (p<0.001). Performing BS, the quality of vascular delineation of the cerebral arteries, cerebral veins and cavernous segment of the ICA increased significantly as compared to standard CTA (1.70 vs. 2.70; 2.60 vs. 4.12; 2.35 vs. 4.40, all p<0.001). Consensus reading showed 41 pathologies in 35 patients. Diagnosis was missed or wrong overall in 15 cases, with 3 missed aneurysms (CTA: 2 vs. BS: 1), 8 wrong stenotic findings (CTA: 3 vs. BS: 5) and 4 missed partial thromboses (CTA: 2 vs. BS: 2). Performing BS in supraaortic CTA for the evaluation of cerebral vasculature reduces reading time and improves delineation of vessels. Diagnostic accuracy in general is not improved by BS, as the diagnostic accuracy of stenotic vessel alterations is reduced by potential truncation artifacts, but the detection rate of cerebral aneurysms slightly increases.

Increasing contrast agent concentration improves enhancement in first-pass CT perfusion

BACKGROUND AND PURPOSE

Our aim was to evaluate whether increasing iodine concentration, at a constant total iodine dose, resulted in better brain tissue opacification in patients with acute stroke symptoms during their evaluation by first-pass CT perfusion (CTP).

MATERIALS AND METHODS

One hundred two patients presenting to the emergency department within 3 hours of onset of acute stroke symptoms underwent CTP scanning. Three different concentrations of iodinated nonionic contrast material were used (300, 350, or 400 mg/mL). Total iodine dose (15 g) and injection rate (7 mL/s) were kept constant. There were 25, 53, and 19 patients in the different concentration groups, respectively; 5 patients were excluded due to uncorrectable motion artifacts. CTP scanning was performed at the level of the putamen, and data were analyzed by determining peak opacification for normal gray and white matter, arterial input, and venous output. Mean and SD values were calculated, and 3 concentration groups, stratified by region-of-interest location, were compared by using a single-tailed unpaired t test.

RESULTS

Monotonic increasing peak opacification was observed in all region-of-interest locations. Statistically significant differences were observed between the 300 and 350 mg/mL, 300 and 400 mg/mL, as well as the 350 and 400 mg/mL groups (P<.01) in white matter, gray matter, and the arterial input. Statistical significance was seen in the venous output group between the 300 and 400 mg/mL (P<.005) and 350 and 400 mg/mL (P<.007) groups, but not between the 300 and 350 mg/mL (P=.2) groups.

CONCLUSION

Increasing contrast concentration improves peak opacification of tissue, suggesting that CTP evaluation of patients with acute stroke is better performed with the highest available concentration contrast agent.

Guidelines for the Early Management of Adults With Ischemic Stroke

Purpose— Our goal is to provide an overview of the current evidence about components of the evaluation and treatment of adults with acute ischemic stroke. The intended audience is physicians and other emergency healthcare providers who treat patients within the first 48 hours after stroke. In addition, information for healthcare policy makers is included.

Methods— Members of the panel were appointed by the American Heart Association Stroke Council’s Scientific Statement Oversight Committee and represented different areas of expertise. The panel reviewed the relevant literature with an emphasis on reports published since 2003 and used the American Heart Association Stroke Council’s Levels of Evidence grading algorithm to rate the evidence and to make recommendations. After approval of the statement by the panel, it underwent peer review and approval by the American Heart Association Science Advisory and Coordinating Committee. It is intended that this guideline be fully updated in 3 years.

Results— Management of patients with acute ischemic stroke remains multifaceted and includes several aspects of care that have not been tested in clinical trials. This statement includes recommendations for management from the first contact by emergency medical services personnel through initial admission to the hospital. Intravenous administration of recombinant tissue plasminogen activator remains the most beneficial proven intervention for emergency treatment of stroke. Several interventions, including intra-arterial administration of thrombolytic agents and mechanical interventions, show promise. Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke is needed.

Guidelines for the early management of adults with ischemic stroke: a guideline from the American Heart Association/American Stroke Association Stroke Council, Clinical Cardiology Council, Cardiovascular Radiology and Intervention Council, and the Atherosclerotic Peripheral Vascular Disease and Quality of Care Outcomes in Research Interdisciplinary Working Groups: the American Academy of Neurology affirms the value of this guideline as an educational tool for neurologists

PURPOSE

Our goal is to provide an overview of the current evidence about components of the evaluation and treatment of adults with acute ischemic stroke. The intended audience is physicians and other emergency healthcare providers who treat patients within the first 48 hours after stroke. In addition, information for healthcare policy makers is included.

METHODS

Members of the panel were appointed by the American Heart Association Stroke Council's Scientific Statement Oversight Committee and represented different areas of expertise. The panel reviewed the relevant literature with an emphasis on reports published since 2003 and used the American Heart Association Stroke Council's Levels of Evidence grading algorithm to rate the evidence and to make recommendations. After approval of the statement by the panel, it underwent peer review and approval by the American Heart Association Science Advisory and Coordinating Committee. It is intended that this guideline be fully updated in 3 years.

RESULTS

Management of patients with acute ischemic stroke remains multifaceted and includes several aspects of care that have not been tested in clinical trials. This statement includes recommendations for management from the first contact by emergency medical services personnel through initial admission to the hospital. Intravenous administration of recombinant tissue plasminogen activator remains the most beneficial proven intervention for emergency treatment of stroke. Several interventions, including intra-arterial administration of thrombolytic agents and mechanical interventions, show promise. Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke is needed.

Image quality in CT perfusion imaging of the brain

The purpose of this study was to evaluate the impact of various iodine contrast concentrations on image quality in computed tomography (CT) perfusion studies. Twenty-one patients with suspicion of cerebral ischemia underwent perfusion CT using two different iodine contrast concentrations: 11 patients received iomeprol 300 (iodine concentration: 300 mg/ml ) while ten received the same volume of iomeprol 400 (iodine concentration: 400 mg/ml). Scan parameters were kept constant for both groups. Maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and time to peak (TTP) were calculated from two adjacent slices. Quantitative comparisons were based on measurements of the maximum enhancement [Hounsfield units (HU)] and signal-to-noise index (SNI) on CBF, CBV, and TTP images. Determinations of grey-to-white-matter delineation for each iodine concentration were performed by two blinded readers. Only data from the non-ischemic hemispheres were considered. Both maximum enhancement and SNI values were higher after iomeprol 400, resulting in significantly better image quality in areas of low perfusion. No noteworthy differences were found for normal values of CBF, CBV, and TTP. Qualitative assessment of grey/white matter contrast on CBF and CBV maps revealed better performance for iomeprol 400. For brain perfusion studies, highly concentrated contrast media such as iomeprol 400 is superior to iomeprol 300.

Imaging of the brain and cerebral vasculature in patients with suspected stroke: advantages and disadvantages of CT and MRI

Although neuroimaging remains the foundation for the diagnosis of cerebrovascular disease, ongoing technologic advances have now opened up new frontiers for stroke evaluation and treatment. Neuroimaging studies can provide crucial information regarding tissue injury (size, location, and degree of reversibility of ischemic injury as well as presence of hemorrhage), vessel status (site and severity of stenoses and occlusions), and cerebral perfusion (size, location, and severity of hypoperfusion). This information can be combined to identify patients with salvageable penumbral tissue who may benefit most from acute therapies. The multimodal combinations of advanced imaging techniques, particularly in the realm of CT and MRI, have emerged as the most promising noninvasive approaches to acute stroke evaluation.

Visual evaluation of perfusion computed tomography in acute stroke accurately estimates infarct volume and tissue viability

OBJECTIVE

To establish the validity of visual interpretation of immediately processed perfusion computed tomography (CT) maps in acute stroke for prediction of final infarction.

METHODS

Perfusion CT studies acquired prospectively were reprocessed within six hours of stroke onset using standard CT console software. Four contiguous 5 mm thick images were obtained and maps of time to peak (TTP) and cerebral blood volume (CBV) generated. Volumes of lesions identified only by visual inspection were measured from manually drawn regions of interest. Volumes of tissue with prolonged TTP or reduced CBV were compared with independently calculated volume of infarction on non-contrast CT (NCCT) at 24-48 hours, and with clinical severity using the NIHSS score. Arterial patency at 24-48 h was included in analyses.

RESULTS

Studies were analysed from 17 patients 150 minutes (median) after stroke onset. Volume of tissue with prolonged TTP correlated with initial NIHSS (r = 0.62, p = 0.009), and with NCCT final infarct volume when arterial occlusion persisted (r = 0.953, p = 0.012). Volume of tissue with reduced CBV correlated with final infarct volume if recanalisation occurred (r = 0.835, p = 0.001). Recanalisation was associated with lower 24 h NIHSS score (6 (IQR, 5 to 9.5) v 19 (18 to 26), p = 0.027), and in 10 patients given rtPA for MCA M1 occlusion, with lower infarct volume (73 v 431 ml, p = 0.002).

CONCLUSIONS

Visual evaluation of TTP and CBV maps generated by standard perfusion CT software correlated with 24-48 hour CT infarct volumes. Comparison of TTP and CBV maps yields information on tissue viability. Perfusion CT represents a practical technique to aid acute clinical decision making. Recanalisation was a crucial determinant of clinical and radiological outcome.

Clinical evaluation of bone-subtraction CT angiography (BSCTA) in head and neck imaging

Fifty-one patients were examined with bone subtraction CT angiography (BSCTA). Data were acquired on 4-and 64-slice spiral CT systems. The post-processing method is based on fully automatic registration of non-enhanced and contrast-enhanced CT data and subsequent selective bone removal. Vascular structures and brain tissue are retained with the original CTA noise level. Image quality and delineation of the pathologic process were assessed and artifacts introduced by the bone removal process recorded. The bone subtraction algorithm worked successfully in all examinations. The processing time was 6 min on average. Image quality was rated excellent in 20 (39%), good in 26 (51%) and acceptable in 5 (10%) patients. Ophthalmic arteries were visible in 12 (24%) patients bilaterally, in 13 (25%) patients unilaterally and in 26 (51%) patients at least at the origin. BSCTA improved visualization of the infraclinoid ICA and the vertebral arteries. The depiction of stenosis of the extracranial ICA and supraclinoid aneurysms was not significantly improved. In patients with suspicion of sinus thrombosis, BSCTA and conventional CTA yielded similar results. To conclude, BSCTA improves the visualization of vessels with close contact to bone and can improve the diagnostic accuracy and therapy planning of infraclinoid aneurysms.

Neuroimaging of ischemia and infarction

Since the introduction of thrombolytic therapy as the foundation of acute stroke treatment, neuroimaging has rapidly advanced to empower therapeutic decision making. Diffusion-weighted imaging is the most sensitive and accurate method for stroke detection, and, allied with perfusion-weighted imaging, provides information on the functional status of the ischemic brain. It can also help to identify a response to thrombolytic and neuroprotective therapies. Additionally, multimodal magnetic resonance imaging, including magnetic resonance angiography, offers information on stroke mechanism and pathophysiology that can guide long-term medical management. Multimodal computed tomography is a comprehensive, cost-effective, and safe stroke imaging modality that can be easily implemented in the emergency ward and that offers fast and reliable information with respect to the arterial and functional status of the ischemic brain. Accessibility, contraindications, cost, speed, and individual patient-determined features influence which is the best imaging modality to guide acute stroke management.

Evaluation of hyperacute stroke using perfusion computed tomography

Evaluation of the cerebral circulation dynamics in patients with stroke soon after onset is extremely important for planning the optimum treatment. Perfusion computed tomography (CT) was evaluated in 118 patients with stroke within 10 hours of onset in whom initial CT showed no ischemic change. The mean transit time (MTT), cerebral blood flow (CBF), and cerebral blood volume (CBV) perfusion CT maps were visually evaluated in three slices covering the body of the lateral ventricle, the basal ganglia, and the pons, and the ratios of the values in regions of interest (ROIs) in the ischemic lesion and the symmetrical location in the opposite hemisphere were calculated (ROI ratio of regional (r) MTT, rCBF, and rCBV). The location of occlusion was confirmed by angiography performed on the same day in 106 cases and the location of infarction by later magnetic resonance (MR) imaging. MTT maps correctly identified 44 of 46 cases of ischemia in the carotid system, 20 of 29 cases of ischemia in the vertebrobasilar system, and 11 of 35 cases of ischemia in perforator regions. Eight cases could not be identified by perfusion CT, angiography, or MR imaging. The ROI ratios at the upper boundary of infarction (n = 18) were: rCBF 0.574 +/- 0.220 (mean +/- SD) and rCBV 0.972 +/- 0.276, and at the lower boundary of non-infarction (n = 24) were: rCBF 0.504 +/- 0.247 and rCBV 0.815 +/- 0.169; showing a statistical significance of p = 0.348 for CBF and p = 0.026 for CBV (unpaired t-test). The perfusion CT MTT maps correlated well with the angiographical findings for the carotid system, but poorly for the vertebrobasilar system and the perforator regions. A rCBF ratio of 0.5 and rCBV ratio of 0.9 were established for the boundaries of ischemia.