Beyond ASPECTS: A Practical Guide to CT Perfusion Interpretation.

Functional computed tomography in oncology and cardiovascular imaging: A key player in the era of precision medicine and radiogenomics

Optimal Imaging at the Primary Stroke Center.

Computed Tomography Perfusion Imaging in Acute Ischemic Stroke: Accurate Interpretation Matters.

Should Primary Stroke Centers Perform Advanced Imaging?

Should Tenecteplase be Given in Clinical Practice for Acute Ischemic Stroke Thrombolysis?

Left ventricular assist devices (LVAD) are widely applied for patients with severe heart failure as a bridge to heart transplantation as well as destination therapy. Patients with implanted LVAD have an increased risk of cerebral thrombosis and computed tomographic perfusion (CTP) has the potential to be performed for early diagnosis and treatment of acute ischemic stroke (AIS), including interventional thrombectomy. Here, we report our series of CTP examination in patients having suspected AIS after LVAD implantation. We retrospectively investigated 33 contrast-enhanced CTPs from January 2017 to December 2018 which were performed in 12 cases of patients because of possible neurological findings leading to suspected AIS during LVAD circulatory support who did not have definite ischemic findings nor intracerebral hemorrhage on non-contrast computed tomography. AIS with perfusion disturbance area was diagnosed in 11 (33.3%) out of a total of 33 CTPs in 4 (33.3%) out of 12 patients. Endovascular thrombectomy(EVT) was successfully performed in this research study four times for three patients. CTP was able to detect and determine the indication for EVT without serious complications. CTP could potentially be the first-choice assessment for early diagnosis of AIS with recoverable ischemic penumbra in patients with LVAD implantation.

We investigated the utility of computed tomographic (CT) perfusion (CTP) with 64-row multi-detector row CT (MDCT) to diagnose acute infarction and ischemic penumbra. We reviewed 58 clinical cases with acute ischemic stroke with CTP, compared the size of the area with long mean transit time (MTT) to that with abnormal intensity in magnetic resonance (MR) diffusion-weighted imaging (DWI) to diagnose penumbra, and compared the size of the area with reduced cerebral blood volume (CBV) in CTP to that in MR DWI to evaluate sensitivity for infarction. The total sensitivity of MTT to acute ischemic lesions was 81% (47/58). Sensitivity of MTT to segmental lesions was 100% (42/42) and for spot and focal lesions, 31% (5/16). In 13 patients, penumbra was diagnosed as lesions mismatched between MTT in CTP and MR DWI. When we regarded a lesion with decreased CBV as infarction, the sensitivity of CBV to segmental lesions was 85% (11/13), and the sensitivity to small infarction was 14% (4/28). Use of 64-row MDCT improves coverage and radiation exposure in head CTP. The combination of plain CT, CT angiography, and CTP with MDCT can demonstrate all segmental ischemic lesions and most large segmental infarctions, and their combined application is useful in considering indication and contraindication for thrombolysis. The problem of low sensitivity for small lesions remains, and MR DWI may be required to assess small infarctions when findings from combined plain CT, CT angiography, and CTP are negative in patients with suspected acute brain stroke.

BackgroundIntravenous thrombolysis with recombinant tissue plasminogen activator (rt-PA) improves outcome after an ischaemic stroke but increases the risk of intracranial haemorrhage. Restricting rt-PA to patients with salvageable tissue, or arterial occlusion, might reduce risk, increase benefit and enable treatment at late time windows.ObjectivesTo determine if computed tomography (CT) or magnetic resonance (MR) perfusion or angiography (CTP/CTA; MRP/MRA) imaging provide important information to guide the use of rt-PA up to 6 hours after a stroke.DesignProspective, multicentre, randomised, open, blinded, end-point trial of rt-PA.SettingForty-eight centres (eight countries) performed CTP/CTA; 37 centres (11 countries) performed MRP/MRA.ParticipantsPatients aged over 18 years in whom brain scanning excluded intracranial haemorrhage, with known time of stroke onset and no clear indication for or contraindication to rt-PA, in whom treatment can start within 6 hours of a stroke.Interventionsrt-PA (0.9 mg/kg, maximum dose 90 mg) intravenously (10% bolus, the rest infused over 1 hour) compared with best medical care.Main outcome measuresPrimary – alive and independent (Oxford Handicap Score 0–2) at 6 months; secondary – symptomatic and fatal intracranial haemorrhage, early and late death. All imaging assessed centrally, blind to other data. Perfusion lesion sizes [cerebral blood volume (CBV); cerebral blood flow; mean transit time (MTT); time to maximum flow], angiographic occlusion, associations with plain scan findings, clinical baseline and outcomes, and the interaction with rt-PA were assessed with dichotomous and ordinal analyses.ResultsBaseline characteristics of patients in the Third International Stroke Trial (IST-3) with perfusion and angiography imaging did not differ from those without (95% did not meet the prevailing licence criteria for rt-PA): 151 patients had perfusion imaging and 423 had angiography (141 and 307 obtained at randomisation respectively). Most randomisation imaging was with CT (n = 125/141, 89% perfusion;n = 277/307, 90% angiography) with little MR (n = 16/141, 11% perfusion;n = 39/307, 10% angiography). The median patient age was 81 (interquartile range 71–86) years; perfusion imaging or angiography imaging was performed at median of 3.9 hours after stroke. Perfusion lesion size differed significantly between parameters (MTT lesions largest, CBV lesions smallest;p < 0.0000; 46% had mismatch). Patients scanned earlier, who were older, or with more severe stroke, had larger perfusion lesions. Larger perfusion lesions were associated with poor outcome. Neither perfusion lesion size nor mismatch modified rt-PA effect on haemorrhage or 6-month outcome. Randomisation CTA (n = 253) showed arterial stenosis/occlusion in 42% (95% confidence interval 34% to 47%). Abnormal plain CT and plain CT + CTA were equally associated with worse baseline stroke severity, imaging and functional outcomes. rt-PA accelerated dissolution of arterial thrombus and reduced thrombus extension, but rt-PA effects did not differ between patients with angiographic occlusion compared with those without.ConclusionLarger perfusion lesions and arterial occlusion are associated with severe stroke and worse outcomes. However, patients with perfusion lesions, mismatch or angiographic occlusion had similar benefit and no worse hazard from rt-PA compared with those without. Visual assessment is an effective classification method. Perfusion or angiography imaging may improve diagnostic confidence in acute stroke but this does not improve prediction of prognosis or identify patients who respond differently to rt-PA. Although this trial is larger than others, the conclusion regarding perfusion imaging is limited by the sample size.Trial registrationCurrent Controlled Trials ISRCTN25765518.FundingThis project was funded by the NIHR Efficacy and Mechanism Evaluation programme and the Medical Research Council, and will be published in full inEfficacy and Mechanism Evaluation; Vol. 1, No. 1. See the NIHR Journals Library website for further project information.

The aim of this systematic review and meta-analysis is to determine the diagnostic accuracy of computed tomography brain perfusion in the prediction of haemorrhagic transformation and patient outcome in acute ischaemic stroke. Electronic databases and grey literature published over the last 10 years related to healthcare and radiology were searched using the key terms: 'computed tomography perfusion', 'haemorrhagic transformation', 'acute ischaemic stroke', 'functional outcome' and their synonyms using both UK and American spellings. Inclusion criteria were: sample size at least 30 patients, original research, evaluate ability of computed tomography perfusion to predict haemorrhagic transformation, reports diagnostic accuracy or provide relevant data for a 2 × 2 contingency table, use follow-up non-contrast computed tomography (NCCT) or magnetic resonance imaging as reference standard. Twelve studies were included in the review; studies cover a total of 808 patients. Haemorrhagic transformation occurred in 30.2% of patients. Pooled sensitivity and specificity were 85.9% (95% CI; 65-97%), 73.9% (95% CI; 45-92%) and accuracy of 79.1% (95% CI; 57-98%). Pooled NPV was 92.9% with a high false positive rate (19.8%), which could be explained in terms of outcome classification, acquisition artefact and computed tomography perfusion processing algorithms. This review evaluated the importance of using pre-defined threshold measurement for optimal prediction of HT, the relevance of patient pre-treatment clinical parameters to HT occurrence, the CTP parameters and the measurements that are independent predictors of HT, the significance of rtPA rather as an exacerbator of HT and the impact of both minor and major HT/PH on patient 20 functional outcome. Computed tomography perfusion has a high sensitivity and moderately high specificity for prediction of haemorrhagic transformation in acute ischaemic stroke. Pre-treatment clinical decision making requires consideration of clinical factors in addition to imaging findings. This systematic review and meta-analysis highlights that pre-treatment computed tomography perfusion adds to clinical confidence by predicting potential for haemorrhage, both in thrombolysed and un-thrombolysed patients, and also influences decisions about alternative treatments for acute ischaemic stroke patients.

It is critical to identify the stroke onset time of patients with acute ischemic stroke (AIS) for the treatment of endovascular thrombectomy (EVT). However, it is challenging to accurately ascertain this time for patients with wake-up stroke (WUS). The current study aimed to construct a deep learning approach based on computed tomography perfusion (CTP) or perfusion weighted imaging (PWI) to identify a 6-h window for patients with AIS for the treatment of EVT. We collected data from 377 patients with AIS, who were examined by CTP or PWI before making a treatment decision. Cerebral blood flow (CBF), time to maximum peak (Tmax), and a region of interest (ROI) mask were preprocessed from the CTP and PWI. We constructed the classifier based on a convolutional neural network (CNN), which was trained by CBF, Tmax, and ROI masks to identify patients with AIS within a 6-h window for the treatment of EVT. We compared the classification performance among a CNN, support vector machine (SVM), and random forest (RF) when trained by five different types of ROI masks. To assess the adaptability of the classifier of CNN for CTP and PWI, which were processed respectively from CTP and PWI groups. Our results showed that the CNN classifier had a higher performance with an area under the curve (AUC) of 0.935, which was significantly higher than that of support vector machine (SVM) and random forest (RF) (p = 0.001 and p = 0.001, respectively). For the CNN classifier trained by different ROI masks, the best performance was trained by CBF, Tmax, and ROI masks of Tmax > 6 s. No significant difference was detected in the classification performance of the CNN between CTP and PWI (0.902 vs. 0.928; p = 0.557). The CNN classifier trained by CBF, Tmax, and ROI masks of Tmax > 6 s had good performance in identifying patients with AIS within a 6-h window for the treatment of EVT. The current study indicates that the CNN model has potential to be used to accurately estimate the stroke onset time of patients with WUS.

Introduction of helical computed tomography (CT) scanning has enabled rapid imaging of the vascular status by means of CT angiography and perfusion CT. By virtue of recent multi-detector technology, helical CT has the ability to perform both CT angiography and multi-section perfusion CT simultaneously. This study investigated the clinical feasibility of simultaneous assessment of perfusion CT and CT angiography in patients with acute ischemic stroke. Perfusion CT and CT angiography were performed simultaneously in a series of consecutive 31 acute ischemic stroke patients. The time required for the entire processing was about 15 minutes. Contrast agent was used in a total dose of 100 ml (35 ml for perfusion CT and 65 ml for CT angiography). Simultaneous perfusion CT scans and CT angiographies were of diagnostic quality for 29 patients (94%). In large territorial infarct patients, perfusion CT could predict all perfusion deficits of the final lesions (10 out of 10 lesions) and CT angiography could detect 9 of 10 occlusions of major cerebral arteries (90%). In patients with small lacunar or subcortical infarcts, perfusion CT could predict 9 out of 19 lesions (47.4%), and false-negative were encountered in small lesions (three patients) or in inadequate coverage of data acquisition (seven patients). Acute stage thrombolytic intervention could be carried out based on the findings, and the success of thrombolytic therapy could be demonstrated by follow-up study. Simultaneous perfusion CT and CT angiography is the very useful tool for the rapid and adequate diagnosis of almost all of the large territorial infarcts and some of non-territorial lacunar infarcts. It is an easy-to-perform and safe imaging technique to assess acute ischemic stroke.

Introduction: Recent randomized clinical trials have demonstrated benefit for treatment with endovascular stroke therapy (EST) and thrombolysis (IV-tPA) in late presenting acute ischemic stroke (AIS) patients using CT perfusion (CTP). The real-world utilization and availability of this advanced imaging modality is unknown. Methods: We identified all inpatient hospitalizations with a primary diagnosis of AIS using ICD-9/10 codes in Texas Medicare claims (2014-2017) and 5% national Medicare sample (2014-2017) and evaluated imaging utilization given at the Emergency Department (ED) prior to admission. Imaging and treatments were identified using CPT and procedure codes. Primary endpoint was ED-based imaging utilization. EST and CTP-capable hospitals were defined as those performing at least one EST or CTP within that calendar year. Results: In the Texas cohort, among 50,797 admissions for AIS, 54% were female, median age was 77 [IQR 69-84], and 78% were white. 2% received EST and 9% received IV-tPA. 76% of AIS patients and 80% of those with EST received ED-based neuro-imaging at the treating hospital (Fig. 1). 58% of all AIS patients were evaluated in EST-capable hospitals. 75% of all AIS patients, 54 % of those with EST, and 70% of those with IV-tPA were evaluated at non-CTP-capable hospitals. 9% of IV-tPA and 17% of EST-treated patients underwent CTP; rates of MRI were greater (Fig. 1). These findings were maintained in the nationwide sample. Among 37,507 admissions for AIS, CTA was performed in 17%, MRI in 30%, and CTP in 3%. Among the 3% of AIS patients treated with EST, CTA was performed in 65%, MRI in 66%, and CTP in 14%. Conclusion: In this population-based cohort, three out of four AIS admissions and half of EST procedures were at non-CTP performing hospitals. The limited availability and utilization of CTP suggest that an alternative imaging paradigm (e.g. MRI) may be beneficial in delayed time-window EST and thrombolysis.

Perfusion CT may improve the diagnostic performance of noncontrast CT in acute ischemic stroke. We assessed predictors of focal hypoperfusion in acute ischemic stroke and perfusion CT performance in predicting infarction on follow-up imaging. Patients from the Acute STroke Registry and Analysis of Lausanne data base with acute ischemic stroke and perfusion CT were included. Clinical and radiologic data were collected. We identified predictors of focal hypoperfusion using multivariate analyses. From the 2216 patients with perfusion CT, 38.2% had an acute ischemic lesion on NCCT and 73.3% had focal hypoperfusion on perfusion CT. After we analyzed 104 covariates, high-admission NIHSS, visual field defect, aphasia, hemineglect, sensory deficits, and impaired consciousness were positively associated with focal hypoperfusion. Negative associations were pure posterior circulation, lacunar strokes, and anticoagulation. After integrating radiologic variables into the multivariate analyses, we found that visual field defect, sensory deficits, hemineglect, early ischemic changes on NCCT, anterior circulation, cardioembolic etiology, and arterial occlusion were positively associated with focal hypoperfusion, whereas increasing onset-to-CT delay, chronic vascular lesions, and lacunar etiology showed negative association. Sensitivity, specificity, and positive and negative predictive values of focal hypoperfusion on perfusion CT for infarct detection on follow-up MR imaging were 66.5%, 79.4%, 96.2%, and 22.8%, respectively, with an overall accuracy of 76.8%. Compared with NCCT, perfusion CT doubles the sensitivity in detecting acute ischemic stroke. Focal hypoperfusion is independently predicted by stroke severity, cortical clinical deficits, nonlacunar supratentorial strokes, and shorter onset-to-imaging delays. A high proportion of patients with focal hypoperfusion developed infarction on subsequent imaging, as did some patients without focal hypoperfusion, indicating the complementarity of perfusion CT and MR imaging in acute ischemic stroke.

Introduction Accurate and early determination of ischemic penumbra versus infarcted core is crucial in selecting patients who are likely to benefit from thrombectomy in acute ischemic stroke (AIS). CT perfusion (CTP) measures regional cerebral blood flow, blood volume, and transit time, and its secondarily derived estimates of core versus penumbra have been used to help select patients in numerous recent randomized trials of thrombectomy for AIS with great success. However, CTP may overestimate core infarct in early time periods, and some have advocated only using ‘clinical mismatch’ and CT (to rule out an already-established large core infarct) when deciding whether to proceed with thrombectomy. The purpose of this study was to evaluate clinical decision making for thrombectomy based on CT versus CTP by multiple observers; to assess how CTP affected clinical decision making and to investigate the inter-rater agreement in imaging interpretation. Materials and methods Imaging sets including non-contrast CT (NCCT) and CTP [RAPID (iSchemaView Inc, Menlo Park, CA)] from patients admitted with the diagnosis of large vessel occlusion (MCA and ICA) stroke at a single institution were retrospectively reviewed from 12/15/2016 to 9/15/2017 by five neurovascular interventionists independently. In order to isolate the contribution of imaging to decision-making, all observers were blinded to the demographics and clinical symptoms of patients and were told that imaging were performed between 0 to 6 hours after the stroke. Each interventionist was asked whether they would intervene in AIS first based upon NCCT, and then after viewing CTP images for the same patient. Inter-rater agreement was calculated using Fleiss’ kappa statistic for multiple observers. Results Datasets of thirty eight consecutive patients (female/male: 14/24; mean age ±SD: 63.24±17.42; side of stroke left/right: 21/17; Thrombectomy no/yes: 19/19) were reviewed. Inter-rater agreement was moderate (κ=0.43) for thrombectomy based on NCCT. Our interventionists had fair agreement (κ=0.33) for thrombectomy based on CTP and had poor agreement (κ=0.17) on change of decision by assessing CTP after NCCT. On average, CTP lead to change of decision for thrombectomy in 13.16% (25) of the cases (table 1 demonstrates values for each interventionist). Conclusion Our study demonstrates heterogeneity in decision-making when only using neuroimaging to determine whether to proceed with thrombectomy within the 0–6 hour time-window. This was true whether CT or CTP was the final imaging modality. Overall, in 13.16% of cases CTP caused the change of decision for thrombectomy. Further work is needed to determine if similar heterogeneity exists within the 6–24 hour time window and/or at other institutions. Disclosures P. Nazari: None. P. Golnari: None. S. Ansari: None. M. Hurley: None. A. Shaibani: None. M. Potts: None. B. Jahromi: None.

The role of CT perfusion (CTP) in the management of patients with acute ischemic stroke (AIS) remains a matter of debate. The primary aim of this study was to evaluate the correlation between the areas of infarction and penumbra on CTP scans and functional outcome in patients with AIS. This was a retrospective review of 100 consecutively treated patients with acute anterior circulation ischemic stroke who underwent CT angiography (CTA) and CTP at admission between February 2011 and October 2014. On CTP, the volume of ischemic core and penumbra was measured using the Alberta Stroke Program Early CT Score (ASPECTS). CTA findings were also noted, including the site of occlusion and regional leptomeningeal collateral (rLMC) score. Functional outcome was defined by modified Rankin Scale (mRS) score obtained at discharge. Associations of CTP and CTA parameters with mRS scores at discharge were assessed using multivariable proportional odds logistic regression models. The median age was 67 years (range 19-95 years), and the median NIH Stroke Scale score was 16 (range 2-35). In a multivariable analysis adjusting for potential confounding variables, having an infarct on CTP scans in the following regions was associated with a worse mRS score at discharge: insula ribbon (p = 0.043), perisylvian fissure (p < 0.001), motor strip (p = 0.007), M2 (p < 0.001), and M5 (p = 0.023). A worse mRS score at discharge was more common in patients with a greater volume of infarct core (p = 0.024) and less common in patients with a greater rLMC score (p = 0.004). The results of this study provide evidence that several CTP parameters are independent predictors of functional outcome in patients with AIS and have potential to identify those patients most likely to benefit from reperfusion therapy in the treatment of AIS.