Diagnostic accuracy of whole-brain CT perfusion in the detection of acute infratentorial infarctions

Effectiveness of CT perfusion in posterior circulation stroke: evaluation of perfusion abnormalities and associated clinical signs

PURPOSE

Acute posterior circulation stroke (PCS) is characterized by often non-specific clinical signs, with neuroimaging playing a pivotal role in assessment in the emergency setting. The aim of this study was to investigate the effectiveness of CT Perfusion (CTP) maps in detecting acute PCS and to identify clinical factors associated with perfusion abnormalities.

METHODS

We retrospectively analyzed clinical and radiological data of consecutive patients with acute PCS admitted to our Stroke Unit that underwent CTP. Follow-up NECT or MRI was performed to confirm the diagnosis of PCS. The effectiveness of CTP to identify PCS was evaluated as the ratio of the CTP in which perfusion abnormalities, compatible with an ischemic event, were present in at least one CTP map among MTT, CBF, TTP, and CBV. Multivariate logistic regression analysis was conducted to identify clinical factors associated with perfusion abnormalities.

RESULTS

CTP showed alterations in 69 of 107 PCS (64.5%) included in final analysis and MTT proved to be the most sensitive. Multivariate analysis showed that atrial fibrillation (OR = 8.571, CI 95% 2.224-33.037, p = 0.002), dyslipidemia (OR = 0.285, CI 95% 0.100-0.814, p = 0.019), visual field deficits (OR = 3.372, CI 95% 1.020-11.150, p = 0.046), and higher neurological deficit (NIHSS > 5) (OR = 4.054, CI 95% 1.147-14.331, p = 0.030) were significantly associated with perfusion abnormalities on CTP.

CONCLUSION

CT perfusion can be a valuable resource for detecting acute PCS showing a moderately high positivity rate, higher than that of NECT alone or CTA. These findings contribute to the growing body of evidence supporting the use of perfusion imaging in acute posterior circulation stroke.

CT Perfusion in Lacunar Stroke: A Systematic Review

BACKGROUND

The main theory underlying the use of perfusion imaging in acute ischemic stroke is the presence of a hypoperfused volume of the brain downstream of an occluded artery. Indeed, the main purpose of perfusion imaging is to select patients for endovascular treatment. Computed Tomography Perfusion (CTP) is the more used technique because of its wide availability but lacunar infarcts are theoretically outside the purpose of CTP, and limited data are available about CTP performance in acute stroke patients with lacunar stroke.

METHODS

We performed a systematic review searching in PubMed and EMBASE for CTP and lacunar stroke with a final selection of 14 papers, which were examined for data extraction and, in particular, CTP technical issues and sensitivity, specificity, PPV, and NPV values.

RESULTS

A global cohort of 583 patients with lacunar stroke was identified, with a mean age ranging from 59.8 to 72 years and a female percentage ranging from 32 to 53.1%.CTP was performed with different technologies (16 to 320 rows), different post-processing software, and different maps. Sensitivity ranges from 0 to 62.5%, and specificity from 20 to 100%.

CONCLUSIONS

CTP does not allow to reasonable exclude lacunar infarct if no perfusion deficit is found, but the pathophysiology of lacunar infarct is more complex than previously thought.

Diagnostic value of whole-brain computed tomographic perfusion imaging for suspected large artery occlusion stroke patients in emergency department

PURPOSE

To evaluate the diagnostic value of whole-brain computed tomographic perfusion (WB-CTP) in emergency department for suspected large artery occlusion stroke.

METHODS

Suspected large artery occlusion (LAO) stroke patients had initial WB-CTP in the neurological emergency department from August 2016 to August 2018 were retrospectively reviewed for analysis. The sensitivity and specificity of non-contrast computed tomographic scan (NCCT) or WB-CTP for diagnosis of cerebral infarction was compared between the anterior circulation and posterior circulation. The imaging characteristics of WB-CTP in patients with stroke-mimics were described.

RESULTS

Among the 300 included patients, 259 patients (86.3%) were finally diagnosed as cerebral infarction, 16 (5.3%) were transient ischemic attack, 10 (3.3%) were epileptic seizure and 3 (1%) were cerebral venous sinus thrombosis (CVST). For patients with final diagnosis of cerebral infarction, WB-CTP found abnormality in 206 cases (79.5%). NCCT had poor sensitivity (4.6%) but high specificity (100%) for cerebral infarction. The CTP imaging had a sensitivity of 81.2% in anterior circulation and 59.6% in posterior circulation stroke, both with good specificity (57.1% and 92.6%, respectively). 60% (6/10) of epileptic patients showed abnormal perfusion in CTP maps, which was inconsistent with cerebral arterial supply territories. Hypoperfusion manifestations were discovered in areas adjacent to occlusion sinus of all 3 CVST cases.

CONCLUSION

This retrospective study indicates WB-CTP can be useful in identifying acute ischemic stroke in emergency department, especially for patients with acute LAO stroke. Moreover, WB-CTP may have a value in differentiating stroke mimics such as epilepsy and CVST.

Mechanical thrombectomy for acute posterior cerebral artery stroke; Feasibility and predictors of outcome

PURPOSE

The territorial involvement and the clinical benefit of endovascular therapy (EVT) of the posterior cerebral artery (PCA) occlusion may vary between patients. The purpose of this study was to investigate the feasibility of mechanical thrombectomy (MT) in isolated posterior cerebral artery occlusions (IPCAOs) and the prognostic factors of EVT.

METHODS

Forty-eight patients with acute PCA occlusion who underwent EVT between Mar 2008 and Apr 2021 from 2 tertiary centers were retrospectively analyzed. Clinical characteristics, imaging and perfusion abnormalities, and angiographic and clinical outcomes were analyzed. Ischemic changes were assessed with the posterior circulation Acute Stroke Prognosis Early Computed Tomography Score (pc-ASPECTS). Perfusion abnormalities were assessed using automated software for Tmax volume measurement and identification of Tmax involved in PCA eloquent areas.

RESULTS

The IPCAO sites were P1 (n = 17) and P2 (n = 31). Overall successful recanalization (mTICI 2b/3) was achieved in 68.8% (33/48) and excellent outcome (90-day mRS 0-1) in 52.1% (25/48) of the patients. Excellent/non-excellent outcome was associated with male sex (p = 0.036), admission NIHSS (p = 0.002), pc-ASPECTS (p = 0.035), Tmax > 6 s involvement of the midbrain-thalamus (p = 0.008), first-line stent-retriever thrombectomy (p = 0.036), complete recanalization (p = 0.009), and modified first pass effect (FPE, p = 0.047). Tmax>6 s involvement of the midbrain-thalamus was an independent predictor for non-excellent outcome on multivariable analysis.

CONCLUSION

Acute stroke from IPCAO may be successfully treated with EVT. Tmax > 6 s involvement of the midbrain-thalamus on perfusion imaging may be a predictor for clinical outcome.

Detection of impending perfusion deficits by intraoperative computed tomography (iCT) in aneurysm surgery of the anterior circulation

Background

The aim of our study was to evaluate the additional benefit of intraoperative computed tomography (iCT), intraoperative computed tomography angiography (iCTA), and intraoperative computed tomography perfusion (iCTP) in the intraoperative detection of impending ischemia to established methods (indocyanine green videoangiography (ICGVA), microDoppler, intraoperative neuromonitoring (IONM)) for initiating timely therapeutic measures.

Methods

Patients with primary aneurysms of the anterior circulation between October 2016 and December 2019 were included. Data of iCT modalities compared to other techniques (ICGVA, microDoppler, IONM) was recorded with emphasis on resulting operative conclusions leading to inspection of clip position, repositioning, or immediate initiation of conservative treatment strategies. Additional variables analyzed included patient demographics, aneurysm-specific characteristics, and clinical outcome.

Results

Of 194 consecutive patients, 93 patients with 100 aneurysms received iCT imaging. While IONM and ICGVA were normal, an altered vessel patency in iCTA was detected in 5 (5.4%) and a mismatch in iCTP in 7 patients (7.5%). Repositioning was considered appropriate in 2 patients (2.2%), where immediate improvement in iCTP could be documented. In a further 5 cases (5.4%), intensified conservative therapy was immediately initiated treating the reduced CBP as clip repositioning was not considered causal. In terms of clinical outcome at last FU, mRS0 was achieved in 85 (91.4%) and mRS1-2 in 7 (7.5%) and remained mRS4 in one patient with SAH (1.1%).

Conclusions

Especially iCTP can reveal signs of impending ischemia in selected cases and enable the surgeon to promptly initiate therapeutic measures such as clip repositioning or intraoperative onset of maximum conservative treatment, while established tools might fail to detect those intraoperative pathologic changes.

PET Detection of Cerebral Necrosis Using an Infarct-Avid Agent 2-Deoxy-2-[18F]Fluoro-D-Glucaric Acid (FGA) in a Mouse Model of the Brain Stroke

PURPOSE

Ischemic stroke is a leading cause of disability worldwide. The volume of necrotic core in affected tissue plays a major role in selecting stroke patients for thrombolytic therapy or endovascular thrombectomy. In this study, we investigated a recently reported positron emission tomography (PET) agent 2-deoxy-2-[¹⁸F]fluoro-D-glucaric acid (FGA) to determine necrotic core in a model of transient middle cerebral artery occlusion (t-MCAO) in mice.

PROCEDURES

The radiopharmaceutical, FGA, was synthesized by controlled, rapid, and quantitative oxidation of clinical doses of 2-deoxy-2-[¹⁸F]fluoro-D-glucose (FDG) in a one-step reaction using a premade kit. Brain stroke was induced in the left cerebral hemisphere of CD-1 mice by occluding the middle cerebral artery for 1 h, and then allowing reperfusion by removing the occlusion. One day post-ictus, perfusion single-photon emission tomography (SPECT) was performed with ^99mTc-lableled hexamethylpropyleneamine oxime (HMPAO), followed by PET acquisition with FGA. Plasma and brain tissue homogenates were assayed for markers of inflammation and neurotrophins.

RESULTS

The kit-based synthesis was able to convert up to 2.2 GBq of FDG into FGA within 5 min. PET images showed 375 % more accumulation of FGA in the ipsilateral hemisphere than in the contralateral hemisphere. SPECT images showed that the ipsilateral HMPAO accumulation was reduced to 55 % of normal levels; there was a significant negative correlation between the ipsilateral accumulation of FGA and HMAPO (p < 0.05). FGA accumulation in stroke also correlated with IL-6 levels in the ipsilateral hemisphere. There was no change in IL-6 or TNFα in the plasma of stroke mice.

CONCLUSIONS

Accumulation of FGA correlated well with the perfusion defect and inflammatory injury. As a PET agent, FGA has potential to image infarcted core in the brain stroke injury with high sensitivity, resolution, and specificity.

Diagnostic and prognostic computed tomography imaging markers in basilar artery occlusion (Review)

Acute ischemic stroke treatment has been revolutionized by the addition of mechanical and aspiration thrombectomy. Randomized controlled trials have proven beyond doubt, the substantial clinical impact of endovascular interventions in anterior circulation territory strokes. Unfortunately, patients with vertebrobasilar ischemic stroke could not be included in these early trials due to inherent clinical, radiological, and prognostic particularities of posterior circulation ischemia; thus, indications for the treatment of posterior fossa strokes and basilar artery occlusion (BAO) are mainly based on retrospective studies and registries. BAO carries high morbidity and mortality, despite the new improvements in endovascular therapy. Identifying patients who will likely benefit from invasive treatment and have a good clinical outcome resides in discovering clinical, biological, or imaging markers, that have prognostic implications. Such imaging markers have been described, especially in the last decade. Hyperdense Basilar Artery Sign (HDBA), Posterior Circulations-Alberta Stroke Program Early CT Score (pc-ASPECTS), Pons-Midbrain Index (PMI), Posterior Circulation Collateral Score (pc-CS), Posterior Circulation CT Angiography Score (pc-CTA), and Basilar Artery on CT Prognostic Score (BATMAN), are computed tomography (CT) markers with properties that can aid the diagnosis of BAO and can independently predict clinical outcome. This paper aims to present a comprehensive review of these imaging signs to have a thorough understanding of their diagnostic and prognostic attributes.

Diagnostic and prognostic utility of computed tomography perfusion imaging in posterior circulation acute ischemic stroke: A systematic review and meta-analysis

BACKGROUND

Computed tomography perfusion (CTP) imaging could be useful in the diagnosis of posterior circulation stroke (PCS) and in identifying patients who are likely to experience favorable outcomes following reperfusion therapy. The current study sought to investigate the diagnostic and prognostic capability of CTP in acute ischemic PCS by performing a systematic review and meta-analysis.

METHODS

Medline/PubMed and the Cochrane Library were searched using the terms: "posterior circulation", "CT perfusion", "acute stroke", and "reperfusion therapy". The following studies were included: (1) patients aged 18 years or above; (2) patients diagnosed with PCS; and (3) studies with good methodological design. Pooled sensitivity (SENS), specificity (SPEC), and area under the curve (AUC), computed using the summary receiver operating characteristic (SROC) curves, were used to determine diagnostic/prognostic capability.

RESULTS

Out of 14 studies included, a meta-analysis investigating diagnostic accuracy of CTP was performed on nine studies. Meta-analysis demonstrated comparable diagnostic accuracy of CTP to non-contrast computed tomography (NCCT) (AUC_CTP : 0.90 [95% CI 0.87-0.92] vs. AUC_NCCT : 0.96 [95% CI 0.94-0.97]); however, with higher pooled sensitivity (SENS_CTP : 72% [95% CI 57%-83%] vs. SENS_NCCT : 25% [95% CI 17%-35%]) and lower specificity (SPEC_CTP : 90% [95% CI 83%-94%] vs. SPEC_NCCT : 96% [95% CI 95%-98%]) than NCCT. Meta-analysis to determine prognostic capability of CTP could not be performed.

CONCLUSIONS

CTP has limited diagnostic utility in acute ischemic PCS, albeit with superior diagnostic sensitivity and inferior diagnostic specificity to NCCT. Further prospective trials are required to validate the prognostic capability of CTP-derived parameters in PCS.

Computed Tomography Perfusion Deficit Volumes Predict Functional Outcome in Patients With Basilar Artery Occlusion

[Figure: see text].

Qualitative versus automatic evaluation of CT perfusion parameters in acute posterior circulation ischaemic stroke

Purpose

To compare the diagnostic accuracy (ACC) in the detection of acute posterior circulation strokes between qualitative evaluation of software-generated colour maps and automatic assessment of CT perfusion (CTP) parameters.

Methods

Were retrospectively collected 50 patients suspected of acute posterior circulation stroke who underwent to CTP (GE “Lightspeed”, 64 slices) within 24 h after symptom onset between January 2016 and December 2018. The Posterior circulation-Acute Stroke Prognosis Early CT Score (pc-ASPECTS) was used for quantifying the extent of ischaemic areas on non-contrast (NC)CT and colour-coded maps generated by CTP4 (GE) and RAPID (iSchemia View) software. Final pc-ASPECTS was calculated on follow-up NCCT and/or MRI (Philips Intera 3.0 T or Philips Achieva Ingenia 1.5 T). RAPID software also elaborated automatic quantitative mismatch maps.

Results

By qualitative evaluation of colour-coded maps, MTT-CTP4D and Tmax-RAPID showed the highest sensitivity (SE) (88.6% and 90.9%, respectively) and ACC (84% and 88%, respectively) compared with the other perfusion parameters (CBV, CBF). Baseline NCCT and CBF provided by RAPID quantitative perfusion mismatch maps had the lowest SE (29.6% and 6.8%, respectively) and ACC (38% and 18%, respectively). CBF and Tmax assessment provided by quantitative RAPID perfusion mismatch maps showed significant lower SE and ACC than qualitative evaluation. No significant differences were found between the pc-ASPECTSs assessed on colour-coded MTT and Tmax maps neither between the scores assessed on colour-coded CBV-CTP4D and CBF-RAPID maps.

Conclusion

Qualitative analysis of colour-coded maps resulted more sensitive and accurate in the detection of ischaemic changes than automatic quantitative analysis.

A Primer on Computed Tomography Perfusion Imaging for the Emergency Physician

BACKGROUND

Brain noncontrast computed tomography (CT), CT angiography, and magnetic resonance imaging have been used clinically for decades, and emergency physicians have a good understanding of their indications, the meaning of their results, and some facility with the interpretation of CT. However, brain CT perfusion (CTP) is relatively new and emergency physicians are less familiar with its basic concepts, indications, and role in managing patients with neurological emergencies.

OBJECTIVE

We will review the parameters of clinical interest on a CTP report, and how to incorporate them into clinical decision-making.

DISCUSSION

Endovascular therapies paired with CTP have opened up a new frontier in stroke management for severely debilitated stroke patients. It is important for emergency physicians to have an understanding of CTP and how to use it clinically.

CONCLUSION

Taking care of patients with large-vessel occlusions is multidisciplinary, and emergency physicians need to understand CTP imaging and its clinical utility.

Incremental Value of Computed Tomography Perfusion for Final Infarct Prediction in Acute Ischemic Cerebellar Stroke

Background

The diagnosis of ischemic cerebellar stroke is challenging because of nonspecific symptoms and very limited accuracy of commonly applied computed tomography (CT) imaging. Advances in CT perfusion imaging provide increasing value in the detection of posterior circulation stroke, but the prognostic value remains unclear. We aimed to identify imaging parameters that predict morphologic outcome in cerebellar stroke patients using advanced CT including whole‐brain CT perfusion (WB‐CTP).

Methods and Results

We selected all subjects with cerebellar WB‐CTP perfusion deficits and follow‐up‐confirmed cerebellar infarction from a consecutive cohort with suspected stroke who underwent WB‐CTP. Posterior‐circulation‐Acute‐Stroke‐Prognosis‐Early‐CT‐Score (pc‐ASPECTS) was determined on noncontrast CT, CT angiography source images, and on parametric WB‐CTP maps. Cerebellar perfusion deficit volumes on all maps and the final infarction volume on follow‐up imaging were quantified. Uni‐ and multivariate regression analyses were performed. Sixty patients fulfilled the inclusion criteria. pc‐ASPECTS on CT angiography source images (ß, −9.239; 95% CI, −14.220 to −4.259; P<0.001) and cerebral blood flow deficit volume (ß, 0.886; 95% CI, 0.684 to 1.089; P<0.001) were significantly associated with final infarction volume in univariate linear regression analysis. The association of cerebral blood flow deficit volume (ß, 0.830; 95% CI, 0.605–1.055; P<0.001) was confirmed in a multivariate linear regression model adjusted for age, sex, pc‐ASPECTS on noncontrast CT, and CT angiography source images and the National Institutes of Health Stroke Scale score on admission. No other clinical or imaging parameters were associated with cerebellar stroke final infarction volume (P>0.05).

Conclusions

In contrast to noncontrast CT and CT angiography, WB‐CTP imaging contains prognostic information for morphologic outcome in patients with acute cerebellar stroke.

Cerebral blood volume lesion extent predicts functional outcome in patients with vertebral and basilar artery occlusion

Background

CT perfusion may improve diagnostic accuracy in posterior circulation stroke. The posterior circulation Acute Stroke Prognosis Early CT score (pc-ASPECTS) on Computed Tomography Angiography source images (CTA-SI) predicts functional outcome in patients with basilar artery occlusion.

Aims

We assessed the prognostic value of pc-ASPECTS on CT perfusion in patients with vertebral and basilar artery occlusion (VBAO) in comparison with CTA-SI.

Methods

Whole-brain CT perfusion from consecutive stroke patients with VBAO at four stroke centers was retrospectively analyzed. pc-ASPECTS – a 10-point score assessing hypoattenuation on CTA-SI – was calculated from CT perfusion parameters as focally reduced cerebral blood flow or cerebral blood volume, focally increased time to peak of the deconvolved tissue residue function (Tmax) or mean transit time. Two investigators independently reviewed the images. Reliability was assessed with intraclass correlation coefficient. Good outcome was defined as modified Rankin scale ≤3 at three months.

Results

We included 60 patients with VBAO. After assessment of four CT perfusion maps simultaneously, area-under-ROC curve (AROC) was 0.83 (95%CI 0.72–0.93) for cerebral blood volume, 0.76 (95%CI 0.64–0.89) for cerebral blood flow, 0.77 (95%CI 0.64–0.89) for Tmax, 0.70 (95%CI 0.56–0.84) for mean transit time versus area-under-ROC curve 0.64 (95%CI 0.50–0.79) for CTA-SI. Cerebral blood volume had greater accuracy compared with CTA-SI for poor outcome (p = 0.04). In logistic regression analysis, cerebral blood volume pc-ASPECTS≤8 was independently associated with poor outcome (OR 9.3 95%CI 2.2–41; p = 0.003, adjusted for age and clinical severity). Inter-rater agreement was substantial for cerebral blood volume pc-ASPECTS (intraclass correlation coefficient 0.82 95%CI 0.71–0.90 versus 0.67 for CTA-SI 95%CI 0.43–0.81).

Conclusions

Cerebral blood volume pc-ASPECTS may identify VBAO patients at higher risk of disability.