Perfusion CT to quantify the cerebral vasospasm following subarachnoid hemorrhage

Feasibility of FDCT Early Brain Parenchymal Blood Volume Maps in Predicting Short-Term Prognosis in Patients With Aneurysmal Subarachnoid Hemorrhage

Purpose

Aneurysmal subarachnoid hemorrhage (SAH) is accompanied by cerebral perfusion changes. We aimed to measure the parenchymal blood volume (PBV) maps acquired by C-arm flat-panel detector CT (FDCT) to assess the cerebral blood volume at an early stage in aneurysmal SAH and to explore the correlation with the outcomes at discharge.

Methods

Data of 66 patients with aneurysmal SAH who underwent FDCT PBV examination were retrospectively analyzed. The PBV of regions of interest, including the cortices of the bilateral frontal lobe, the parietal lobe, the occipital lobe, and the cerebral hemisphere, as well as the basal ganglia, were measured and quantitatively analyzed. The clinical and imaging data of the patients were also collected, and logistic regression analysis was performed to explore the correlation between the perfusion parameters and outcomes at discharge.

Results

The favorable and poor outcomes at discharge were found in 37 (56.06%) and 29 (43.94%) patients, respectively. The whole-brain PBV was significantly correlated with the Hunt-Hess grades (p < 0.005) and the WFNSS grades (p < 0.005). The whole-brain PBV of the poor prognosis was significantly higher than that of the favorable prognosis (35.17 ± 7.66 vs. 29.78 ± 5.54, p < 0.005). The logistic regression analysis showed that the PBV of the parietal lobe at the bleeding side (OR = 1.10, 95%CI: 1.00-1.20, p = 0.04) was an independent risk factor predicting the short-term prognosis.

Conclusions

Parenchymal blood volume (PBV) maps could reflect the cerebral blood volume throughout the brain to characterize its perfusion status at an early stage in aneurysmal SAH. It enables a one-stop imaging evaluation and treatment in the same angio-suite and may serve as a reliable technique in clinical assessment of aneurysmal SAH.

The Utility of Quantitative EEG in Detecting Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage

SUMMARY

In this review, we discuss the utility of quantitative EEG parameters for the detection of delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage in the context of the complex pathophysiology of DCI and the limitations of current diagnostic methods. Because of the multifactorial pathophysiology of DCI, methodologies solely assessing blood vessel narrowing (vasospasm) are insufficient to detect all DCI. Quantitative EEG has facilitated the exploration of EEG as a diagnostic modality of DCI. Multiple quantitative EEG parameters such as alpha power, relative alpha variability, and alpha/delta ratio show reliable detection of DCI in multiple studies. Recent studies on epileptiform abnormalities suggest that their potential for the detection of DCI. Quantitative EEG is a promising, continuous, noninvasive, monitoring modality of DCI implementable in daily practice. Future work should validate these parameters in larger populations, facilitated by the development of automated detection algorithms and multimodal data integration.

Computed tomography perfusion as a predictor of delayed cerebral ischemia and functional outcome in spontaneous subarachnoid hemorrhage: A single center experience

BACKGROUND

Computed tomography (CT) perfusion has been studied as a tool to predict delayed cerebral ischemia (DCI) and clinical outcome in spontaneous subarachnoid hemorrhage (SAH). The purpose of the study was to determine whether quantitative CT perfusion performed within 72 hours after admission can predict the occurrence of DCI and clinical outcome as measured with a modified Rankin scale (mRS) at 3 months after ictus.

METHODS

Cerebral perfusion was assessed in a prospective cohort of patients with acute SAH. CT perfusion parameters at <72 h post SAH were quantitatively measured in the main vascular territories and represented as whole-brain means. Spearman rank correlation coefficient and generalized additive regression models for binary outcome were used.

RESULTS

A total of 66 patients underwent CT perfusion at <72 h. Poor clinical grade on admission was correlated with worse cerebral perfusion in all parameters. Multivariable analysis yielded an association of time to peak (TTP; odds ratio (OR) = 0.89; 95% confidence interval (CI): 0.77, 1.02; p = 0.083) with the occurrence of DCI. We also found an association of TTP values with poor outcome, with an 8% increase in the odds of mRS > 3 for each one second increase in TTP at admission (OR = 1.08; 95% CI: 1.00, 1.17; p = 0.061).

CONCLUSIONS

We identified an association of early TTP changes with DCI and poor clinical outcome. However, there were no associations with cerebral blood flow or mean transit time and DCI/clinical outcome. CT perfusion still remains to be validated as a tool in predicting outcome in SAH.

Imaging predictors of outcome in acute spontaneous subarachnoid hemorrhage: a review of the literature

Spontaneous subarachnoid hemorrhage (SAH) accounts for about 5% of strokes, but has a very high morbidity and mortality. Many survivors are left with important cognitive impairment and are severely incapacitated. Prediction of complications such as vasospasm and delayed cerebral ischemia, and of clinical outcome after SAH, is challenging. Imaging studies are essential in the initial evaluation of SAH patients and are increasingly relevant in assessing for complications and prognosis. In this article, we reviewed the role of imaging studies in evaluating early brain injury and predicting complications as well as clinical and neuropsychological prognosis after acute SAH.

Diagnosing Vasospasm After Subarachnoid Hemorrhage: CTA and CTP

Cerebral vasospasm is a potentially devastating complication in patients with aneurysmal subarachnoid hemorrhage. The purpose of this article is to review the use of computed tomogram (CT) angiography and CT perfusion in the diagnosis of cerebral vasospasm after aneurysmal subarachnoid hemorrhage and also assess their use in guiding treatment decisions. Both techniques are widely used for other indications but their use in cerebral vasospasm has not been well defined. Computed tomogram angiography can directly visualize arterial narrowing and CT perfusion is able to evaluate differences in perfusion parameters after aneurysmal subarachnoid hemorrhage with high sensitivity and specificity. CT perfusion is better at predicting which patients require endovascular treatment.

Early Cerebral Circulation Disturbance in Patients Suffering from Severe Traumatic Brain Injury (TBI): A Xenon CT and Perfusion CT Study

Traumatic brain injury (TBI) is widely known to cause dynamic changes in cerebral blood flow (CBF). Ischemia is a common and deleterious secondary injury following TBI. Detecting early ischemia in TBI patients is important to prevent further advancement and deterioration of the brain tissue. The purpose of this study was to clarify the cerebral circulatory disturbance during the early phase and whether it can be used to predict patient outcome. A total of 90 patients with TBI underwent a xenon-computed tomography (Xe-CT) and subsequently perfusion CT to evaluate the cerebral circulation on days 1–3. We measured CBF using Xe-CT and mean transit time (MTT: the width between two inflection points [maximum upward slope and maximum downward slope from inflow to outflow of the contrast agent]) using perfusion CT and calculated the cerebral blood volume (CBV) using the AZ-7000W98 computer system. The relationships of the hemodynamic parameters CBF, MTT, and CBV to the Glasgow Coma Scale (GCS) score and the Glasgow Outcome Scale (GOS) score were examined. There were no significant differences in CBF, MTT, and CBV among GCS3–4, GCS5–6, and GCS7–8 groups. The patients with a favorable outcome (GR and MD) had significantly higher CBF and lower MTT than those with an unfavorable one (SD, VS, or D). The discriminant analysis of these parameters could predict patient outcome with a probability of 70.6%. During the early phase, CBF reduction and MTT prolongation might influence the clinical outcome of TBI. These parameters are helpful for evaluating the severity of cerebral circulatory disturbance and predicting the outcome of TBI patients.

Volume perfusion CT imaging of cerebral vasospasm: diagnostic performance of different perfusion maps

INTRODUCTION

In this study, we aimed to evaluate the diagnostic performance of different volume perfusion CT (VPCT) maps regarding the detection of cerebral vasospasm compared to angiographic findings.

METHODS

Forty-one datasets of 26 patients (57.5 ± 10.8 years, 18 F) with subarachnoid hemorrhage and suspected cerebral vasospasm, who underwent VPCT and angiography within 6 h, were included. Two neuroradiologists independently evaluated the presence and severity of vasospasm on perfusion maps on a 3-point Likert scale (0-no vasospasm, 1-vasospasm affecting <50 %, 2-vasospasm affecting >50 % of vascular territory). A third neuroradiologist independently assessed angiography for the presence and severity of vasospasm on a 3-point Likert scale (0-no vasospasm, 1-vasospasm affecting < 50 %, 2-vasospasm affecting > 50 % of vessel diameter). Perfusion maps of cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and time to drain (TTD) were evaluated regarding diagnostic accuracy for cerebral vasospasm with angiography as reference standard. Correlation analysis of vasospasm severity on perfusion maps and angiographic images was performed. Furthermore, inter-reader agreement was assessed regarding findings on perfusion maps.

RESULTS

Diagnostic accuracy for TTD and MTT was significantly higher than for all other perfusion maps (TTD, AUC = 0.832; MTT, AUC = 0.791; p < 0.001). TTD revealed higher sensitivity than MTT (p = 0.007). The severity of vasospasm on TTD maps showed significantly higher correlation levels with angiography than all other perfusion maps (p ≤ 0.048). Inter-reader agreement was (almost) perfect for all perfusion maps (kappa ≥ 0.927).

CONCLUSION

The results of this study indicate that TTD maps have the highest sensitivity for the detection of cerebral vasospasm and highest correlation with angiography regarding the severity of vasospasm.

Whole-brain CT perfusion combined with CT angiography for ischemic complications following microsurgical clipping and endovascular coiling of ruptured intracranial aneurysms

Ischemic complications associated with microsurgical clipping and endovascular coiling affects the outcome of patients with intracranial aneurysms. We prospectively evaluated 58 intracranial aneurysm patients who had neurological deterioration or presented with poor grade (Hunt-Hess grades III and IV), aneurysm size >13 mm and multiple aneurysms after clipping or coiling. Thirty patients had ischemic complications (52%) as demonstrated by whole-brain CT perfusion (WB-CTP) combined with CT angiography (CTA). Half of these 30 patients had treatment-associated reduction in the diameter of the parent vessels (n=6), ligation of the parent vessels or perforating arteries (n=2), and unexplained or indistinguishable vascular injury (n=7); seven of these 15 (73%) patients suffered infarction. The remaining 15 patients had disease-associated cerebral ischemia caused by generalized vasospasm (n=6) and focal vessel vasospasm (n=9); six of these 15 (40%) patients developed infarction. Three hemodynamic patterns of ischemic complications were found on WB-CTP, of which increased time to peak, time to delay and mean transit time associated with decreased cerebral blood flow and cerebral blood volume were the main predictors of irreversible ischemic lesions. In conclusion, WB-CTP combined with CTA can accurately determine the cause of neurological deterioration and classify ischemic complications. This combined approach may be helpful in assessing hemodynamic patterns and monitoring operative outcomes.

Complications and follow up of subarachnoid hemorrhages

Complications of subarachnoid hemorrhage are the major life threatening and functional components of the follow up of a ruptured aneurysm. Knowing how to identify these is a key challenge. They vary in type throughout the postoperative follow up period. The aim of this article is firstly to list the main complications of the acute phase (rebleeding, acute hydrocephalus, acute ischemic injury and non-neurological complications), the subacute phase (vasospasm) and the chronic phase of subarachnoid hemorrhages: (chronic hydrocephalus and cognitive disorders) and to describe their major clinical and radiological features. Secondly, we describe the long-term follow up strategy for patients who have suffered a subarachnoid hemorrhage and have been treated endovascularly or by surgery. This follow up involves a combination of clinical consultations, cerebral MRI and at least one review angiogram.

Institution of sustained endovascular treatment prior to clinical deterioration in patients with severe angiographic vasospasm: A retrospective observational study of clinico-radiological outcomes

Severe angiographic vasospasm (aVSP) is a risk factor for infarction following subarachnoid haemorrhage and infarction is strongly associated with poor outcome. We present the clinico-radiological results of cohort with severe aVSP who underwent a program of angiographic surveillance and sustained endovascular treatment using multiple verapamil infusions and/or transluminal balloon angioplasty (TBA).

METHODS

This was a dual-centre retrospective observational study. Angiographic screening for vasospasm was undertaken at days 5-7 post-ictus. Treatment was instituted principally on the basis of radiographic findings. The rate of infarction was evaluated on follow-up CT. Clinical outcome was assessed using the modified Rankin Scale (mRS).

RESULTS

Fifty-seven WFNS grades 1-5 patients were studied. The mean number of procedures/patient was 6, range 2-13. Mean verapamil dose administered to the ICA was 14 mg and VA was 12 mg. Thirty-one patients underwent TBA (52.6%). The rate of proximal vessel infarction was 3/45 (6.7%) for patients presenting <72 hours. Rates of favourable outcome (mRS 0-2) were 16/19 (84.2%) for WFNS grades 1-2, 12/19 (63.2%) for grades 3-4 and 5/19 (26.3%) for grade 5 patients. Delayed presentation >72 hours was the only factor on multivariate analysis to significantly predict aVSP-infarction [OR19.3 (3.2-116.6) P=0.0012]. Large aVSP-infarction [OR19.0 (1.7-216.4) 0.0179] and poor WFNS grade [OR 6.6 (1.3-33.9) P = 0.0233] were significant predictors of poor outcome on multivariate analysis.

CONCLUSION

This approach may result in low rates of aVSP-infarction and encouraging rates of favourable outcome when compared to literature benchmarks. Delayed presentation, however, predicts infarction and large infarct and poor initial grade significantly influence functional outcome.

Long-term impact of perfusion CT data after subarachnoid hemorrhage

INTRODUCTION

Dynamic perfusion computed tomography (PCT) has been established as a diagnostic instrument for the detection of vasospasm after subarachnoid hemorrhage (SAH). The purpose of this study was to assess the prognostic impact of PCT parameters after SAH on the long-term outcome of patients.

METHODS

Three hundred twelve patients were retrospectively interrogated with a questionnaire 23.06 ± 14.33 months after spontaneous subarachnoid hemorrhage. The modified Rankin scale (mRS) was determined, respectively. Scheduled PCT data sets from the first days after ictus were available for all patients.

RESULTS

The maximum mean transit time over several examinations per hemisphere (MTTPEAK) values were significantly correlated (p ≤ 0.001, r = 0.422) with the clinical long-term outcome (mRS). Corresponding to our linear regression analysis, MTTPEAK is the second most important regressor (behind clinical severity of the initial hemorrhage) for the prediction of long-term mRS. An MTTPEAK threshold of 3.98 s (identified by receiver operating characteristic analysis, area under the curve = 0.75) predicted an unfavorable long-term outcome (mRS ≥ 2) with a sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of 67.3, 74.3, 84.5, 52.1, and 69.6 %, respectively.

CONCLUSION

The presented data corroborate the relevance of PCT data for the clinical long-term outcome of SAH patients. By identification of patients who are at risk for a bad outcome and may need escalation of therapy, risk-benefit analysis is supported.

Early cerebral circulatory disturbance in patients suffering subarachnoid hemorrhage prior to the delayed cerebral vasospasm stage: xenon computed tomography and perfusion computed tomography study

Subarachnoid hemorrhage (SAH) causes dynamic changes in cerebral blood flow (CBF), and results in delayed ischemia due to vasospasm, and early perfusion deficits before delayed cerebral vasospasm (CVS). The present study examined the severity of cerebral circulatory disturbance during the early phase before delayed CVS and whether it can be used to predict patient outcome. A total of 94 patients with SAH underwent simultaneous xenon computed tomography (CT) and perfusion CT to evaluate cerebral circulation on Days 1-3. Cerebral blood flow (CBF) was measured using xenon CT and the mean transit time (MTT) using perfusion CT and calculated cerebral blood volume (CBV). Outcome was evaluated with the Glasgow Outcome Scale (good recovery [GR], moderate disability [MD], severe disability [SD], vegetative state [VS], or death [D]). Hunt and Hess (HH) grade II patients displayed significantly higher CBF and lower MTT than HH grade IV and V patients. HH grade III patients displayed significantly higher CBF and lower MTT than HH grade IV and V patients. Patients with favorable outcome (GR or MD) had significantly higher CBF and lower MTT than those with unfavorable outcome (SD, VS, or D). Discriminant analysis of these parameters could predict patient outcome with a probability of 74.5%. Higher HH grade on admission was associated with decreased CBF and CBV and prolonged MTT. CBF reduction and MTT prolongation before the onset of delayed CVS might influence the clinical outcome of SAH. These parameters are helpful for evaluating the severity of SAH and predicting the outcomes of SAH patients.

Perfusion imaging in brain disease

Perfusion CT or MRI have been extensively developed over the last years and are accessible on most imaging machines. Perfusion CT has taken a major place in the assessment of a stroke. Its role has to be specified for the diagnosis and treatment of the vasospasm, complicating a subarachnoid hemorrhage. Perfusion MRI should be included in the assessment of any brain tumor, both at the time of the diagnosis as well as in the post-treatment monitoring. It is included in the multimodal approach required for the optimum treatment of this disease. The applications in epilepsy and the neurodegenerative diseases are in the evaluation process.

A phantom approach to interscanner comparability of computed tomographic brain perfusion parameters

OBJECTIVE

This study aimed to create a phantom, which allows reproducible computed tomography perfusion experiments, and to identify the influence of contrast bolus configuration, scan parameters, and scanner hardware on the calculation of perfusion parameters.

METHODS

A discoid perfusion phantom with centrifugally directed flow was constructed. Brain parenchyma was simulated by inert polyoxymethylene spheres. Repeated measurements were performed with variations of the above-mentioned factors, and their effects on perfusion results were analyzed.

RESULTS

Calculated flow values measured during experiments were reproducible and showed good correlation with the true flow (R = 0.995, P < 0.01). Tube voltage, injection rate of the contrast agent, the mathematical perfusion algorithm, and the hardware of the scanner hardware had a reproducible influence on calculated perfusion results.

CONCLUSIONS

In the long term, perfusion phantoms might be helpful in identifying hardware-specific and protocol-related factors of different computed tomography scanners to improve comparability of different scanners and scanning protocols.

An Approach for Incorporating Context in Building Probabilistic Predictive Models

With the increasing amount of information collected through clinical practice and scientific experimentation, a growing challenge is how to utilize available resources to construct predictive models to facilitate clinical decision making. Clinicians often have questions related to the treatment and outcome of a medical problem for individual patients; however, few tools exist that leverage the large collection of patient data and scientific knowledge to answer these questions. Without appropriate context, existing data that have been collected for a specific task may not be suitable for creating new models that answer different questions. This paper presents an approach that leverages available structured or unstructured data to build a probabilistic predictive model that assists physicians with answering clinical questions on individual patients. Various challenges related to transforming available data to an end-user application are addressed: problem decomposition, variable selection, context representation, automated extraction of information from unstructured data sources, model generation, and development of an intuitive application to query the model and present the results. We describe our efforts towards building a model that predicts the risk of vasospasm in aneurysm patients.

Acute perfusion changes after spontaneous SAH: a perfusion CT study

BACKGROUND

Perfusion computed tomography (CT) is a rapid technique that allows the measurement of acute disturbances in local and global cerebral blood flow in patients suffering stroke and spontaneous subarachnoid haemorrhage (SAH). The purpose of this study was to establish the relationship between different measures of brain perfusion made on dynamic-contrast CT reconstructions performed as soon as SAH has been diagnosed and the severity of the bleeding determined by the clinical grade, the extent of the bleeding and the outcome of the patients.

METHODS

After the diagnosis of SAH by conventional CT, a perfusion CT was performed before CT angiography. All imaging studies were performed on a six-slice spiral CT scanner. All images were analysed using perfusion software developed by Philips, which produces perfusion CT quantitative data based on temporal changes in signal intensity during the first pass of a bolus of an iodinated contrast agent. Measurements of mean transient time (MTT), time to peak (TTP), cerebral blood volume (CBV) and cerebral blood flow (CBF) in volumes of interest corresponding to territories perfused by the major cerebral arteries were performed. Different data regarding severity of the bleeding-such as level of consciousness, amount of bleeding in conventional CT-were collected. All poor-grade patients received a ventriculostomy catheter so that ICP recordings were obtained. Also, the occurrence of delayed cerebral ischaemia (DCI) was recorded. Outcome was assessed by the Glasgow Outcome Scale 6 months after the bleeding. For statistical analysis, non-parametric correlations between variables were performed.

FINDINGS

Thirty-nine patients have been included in the study since January 2007. In SAH patients there are increasing perfusion abnormalities as the severity of the bleeding increases. The most affected perfusion parameters are TTP and MTT, as they significantly increase with the clinical severity of the bleeding and the total volume of bleeding (P < 0.01, Spearman's Rho). When average MTT time is increased over 5.9 s there is a 20-fold (95% CI = 2.1-182) risk of poor outcome. All patients presenting this MTT time suffered from DCI. This value has a positive predictive value of 100% for DCI and 90% for a poor outcome.

CONCLUSIONS

SAH causes cerebral blood flow abnormalities even in the acute phase of the illness, consisting mainly of an increase in circulation times (TTP and MTT), which are correlated with the severity of the bleeding.

Safety and feasibility in highly concentrated contrast material power injections for CT-perfusion studies of the brain using central venous catheters

INTRODUCTION

CT perfusion studies play an important role in the early detection as well as in therapy monitoring of vasospasm after subarachnoid hemorrhage. High-flow injections via central venous catheters are not recommended but may sometimes be the only possibility to obtain high-quality images.

MATERIALS AND METHODS

We retrospectively analyzed our data for CT perfusions performed with power injection of contrast material with an iodine concentration of 400mg/ml via the distal 16G lumen of the Arrow three and five lumen central venous catheter with preset flow rates of 5ml/s.

RESULTS

104 examinations with central venous catheters were evaluated (67 with five lumen and 37 with three lumen). No complications were observed. Mean flow rates were 4.4±0.5ml/s using the three lumen catheter and 4.6±0.6ml/s using the five lumen catheter respectively. The mean injection pressure measured by the power injector was 200.7±17.5psi for the three lumen central venous catheter and 194.5±6.5psi for the five lumen catheter, respectively.

CONCLUSION

Following a strict safety protocol there were no complications associated with power injections of contrast material containing 400mg iodine/ml with preset flow rates up to 5ml/s via the distal 16G lumen of the Arrow multi-lumen central venous catheter. However, since power-injections are off-label use with Arrow central venous catheters, this procedure cannot be recommended until potential safety hazards have been ruled out by the manufacturer.