Dynamic computed tomography (CT)-based brain perfusion imaging is a non-invasive technique that can provide quantitative measurements of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). However, due to high radiation dose, dynamic CT scan with a low tube voltage and current protocol is commonly used. Because of this reason, the increased noise degrades the quality and reliability of perfusion maps. In this study, we aim to propose and investigate the feasibility of utilizing a convolutional neural network and a bi-directional long short-term memory model with an attention mechanism to self-supervisedly yield the impulse residue function (IRF) from dynamic CT images. Then, the predicted IRF can be used to compute the perfusion parameters. We evaluated the performance of the proposed method using both simulated and real brain perfusion data and compared the results with those obtained from two existing methods: singular value decomposition and tensor total-variation. The simulation results showed that the overall performance of parameter estimation obtained from the proposed method was superior to that obtained from the other two methods. The experimental results showed that the perfusion maps calculated from the three studied methods were visually similar, but small and significant differences in perfusion parameters between the proposed method and the other two methods were found. We also observed that there were several low-CBF and low-CBV lesions (i.e., suspected infarct core) found by all comparing methods, but only the proposed method revealed longer MTT. The proposed method has the potential to self-supervisedly yield reliable perfusion maps from dynamic CT images.

We aimed to explore potential cytokines involved in the malignant middle cerebral artery infarction (MMI) and elucidate their underlying regulatory mechanisms.

We first developed a cytokine profile by Quantibody^® Human Cytokine Antibody Array7000 using serum samples from eight patients with MMI and eight patients with non-acute cerebral infarction (NACI). The differentially expressed cytokines were then identified in patients with MMI using two-tailed Student's t-test and Fisher's Exact Test compared with patients with NACI. Gene Ontology and pathway enrichment analyses were performed using DAVID. Protein-protein interaction (PPI) network was constructed based on STRING database.

A total of 10 differentially expressed cytokines were identified from 320 unique inflammatory cytokines in serums. Among them, four cytokines, like NCAM1 (neural cell adhesion molecule 1), IGFBP-6 (insulin-like growth factor binding protein 6), LYVE1 (lymphatic vessel endothelial hyaluronan receptor 1), and LCN2 (Lipocalin2), were up-regulated, while another six cytokines, such as TGFB1 (transforming growth factor, beta 1, also known as LAP), EGF (epidermal growth factor), PDGFA (platelet-derived growth factor alpha polypeptide), MMP-10 (matrix metallopeptidase 10), IL-27 (interleukin 27), and CCL2 (chemokine (C-C motif) receptor 2), were down-regulated. Moreover, cytokine-cytokine receptor interaction pathway was significantly enriched.

Our findings indicate that 10 differentially expressed cytokines, such as NCAM1, LCN2, IGFBP-6, LYVE1, MMP-10, IL-27, PDGFA, EGF, CCL2, and TGFB1 may participate in the development of MMI. Moreover, cytokine-cytokine receptor interaction pathway may be an important mechanism involved in this disease. These differentially expressed cytokines may serve as diagnostic biomarkers or drug targets for MMI.

The standardized diagnostic criteria for computed tomographic angiography (CTA) in diagnosis of brain death (BD) are not yet established. The aim of the study was to compare the sensitivity and interobserver agreement of the three previously used scales of CTA for the diagnosis of BD.

Eighty-two clinically brain-dead patients underwent CTA with a delay of 40 s after contrast injection. Catheter angiography was used as the reference standard. CTA results were assessed by two radiologists, and the diagnosis of BD was established according to 10-, 7-, and 4-point scales.

Catheter angiography confirmed the diagnosis of BD in all cases. Opacification of certain cerebral vessels as indicator of BD was highly sensitive: cortical segments of the middle cerebral artery (96.3 %), the internal cerebral vein (98.8 %), and the great cerebral vein (98.8 %). Other vessels were less sensitive: the pericallosal artery (74.4 %), cortical segments of the posterior cerebral artery (79.3 %), and the basilar artery (82.9 %). The sensitivities of the 10-, 7-, and 4-point scales were 67.1, 74.4, and 96.3 %, respectively (p<0.001). Percentage interobserver agreement in diagnosis of BD reached 93 % for the 10-point scale, 89 % for the 7-point scale, and 95 % for the 4-point scale (p=0.37).

In the application of CTA to the diagnosis of BD, reducing the assessment of vascular opacification scale from a 10- to a 4-point scale significantly increases the sensitivity and maintains high interobserver reliability.

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.

PCT postprocessing commonly uses either the MS or a variant of the DC approach for modeling of voxel-based time-attenuation curves. There is an ongoing discussion about the respective merits and limitations of both methods, frequently on the basis of theoretic reasoning or simulated data. We performed a qualitative and quantitative comparison of DC and MS by using identical source datasets and preprocessing parameters.

From the PCT data of 50 patients with acute ischemic stroke, color maps of CBF, CBV, and various temporal parameters were calculated with software implementing both DC and MS algorithms. Color maps were qualitatively categorized. Quantitative region-of-interest-based measurements were made in nonischemic GM and WM, suspected penumbra, and suspected infarction core. Qualitative results, quantitative results, and PCT lesion sizes from DC and MS were statistically compared.

CBF and CBV color maps based on DC and MS were of comparably high quality. Quantitative CBF and CBV values calculated by DC and MS were within the same range in nonischemic regions. In suspected penumbra regions, average CBF(DC) was lower than CBF(MS). In suspected infarction core regions, average CBV(DC) was similar to CBV(MS). Using adapted tissue-at-risk/nonviable-tissue thresholds, we found excellent correlation of DC and MS lesion sizes.

DC and MS yielded comparable qualitative and quantitative results. Lesion sizes indicated by DC and MS showed excellent agreement when using adapted thresholds. In all cases, the same therapy decision would have been made.

As a growing number of therapeutic treatment options for acute stroke are being introduced, multimodal acute neuroimaging is assuming a growing role in the initial evaluation and management of patients. Multimodal neuroimaging, using either a CT or MRI approach, can identify the type, location, and severity of the lesion (ischemia or hemorrhage); the status of the cerebral vasculature; the status of cerebral perfusion; and the existence and extent of the ischemic penumbra. Both acute and long-term treatment decisions for stroke patients can then be optimally guided by this information.

CTP has a growing role in evaluating stroke. It can be performed immediately following NCCT and has advantages of accessibility and speed. Differentiation of salvageable ischemic penumbra from unsalvageable core infarct may help identify patients most likely to benefit from thrombectomy or thrombolysis. Still, CTP interpretation can be complex. We review normal and ischemic perfusion patterns followed by an illustrative series of technical/diagnostic challenges of CTP interpretation in the setting of acute stroke syndromes.

The purpose of this study was to evaluate cerebral blood flow, cerebral blood volume, mean transit time, time to peak, and delay in a selected sample of patients with visually normal or increased cerebral blood volume to facilitate detection of a postischemic CT perfusion hyperperfusion-reperfusion phenomenon that may mask subacute and acute infarcts.

Ten patients were included who had visually normal or elevated cerebral blood volume in infarcts larger than 1.5 cm confirmed on diffusion-weighted MR images within 48 hours of perfusion CT. The cases were selected from 371 perfusion CT studies of stroke patients (99 associated with positive diffusion-weighted imaging findings) reviewed over 2.5 years on a 64-MDCT scanner. The perfusion CT images were fused to the diffusion-weighted images for measurement of cerebral blood volume, cerebral blood flow, mean transit time, time to peak, and delay in each infarct versus the contralateral hemisphere. Two neuroradiologists reviewed the images in consensus.

The mean time between symptom onset and perfusion CT was 3.9 days. Infarcts were in the middle cerebral artery (n = 7) and posterior cerebral artery (n = 3) distributions. Significant differences versus the contralateral finding were found in cerebral blood volume (p = 0.016; mean increase, 30.0%), mean transit time (p = 0.007; mean increase, 38.1%), time to peak (p = 0.005; mean increase, 17.7%), and delay (p = 0.030; mean increase, 124.9%). The difference in cerebral blood flow (p = 0.785; mean increase, 1.8%) was not statistically significant. Infarcts became enhanced on the dynamic perfusion CT images of eight of 10 patients and on the contrast-enhanced T1-weighted MR images of six of nine patients.

Visual inspection of cerebral blood volume and cerebral blood flow maps alone is insufficient in the evaluation of infarcts. Mean transit time, time to peak, and delay maps also should be reviewed with dynamic source images to prevent misinterpretation of findings as false-negative. This phenomenon is unlikely to occur hyperacutely (< 8 hours after onset).

Modern computed tomographic scanners and examination protocols often require high injection rates of iodinated contrast media (CM). The purpose of this study was to investigate the maximum injection pressures (MIPs) with different CM at different temperatures in the most common intravenous cannula (IVC) sizes.

Three IVC sizes, 22, 20, and 18 gauge, were evaluated. All examinations were performed with a pressure-limited (300 psi) power injector. The MIPs of three different CM (Solutrast 300, Imeron 350, and Imeron 400) were measured at room temperature (20 degrees C) and at 37 degrees C using increasing flow rates (1-9 mL/s). The intactness of the IVCs was checked after injection.

Heating the CM led to reductions in injection pressures (P < .001). Using constant flow rates, the difference in MIP between 20-gauge and 22-gauge IVCs was higher than that between 20-gauge and 18-gauge IVCs. By heating the CM, the manufacturer's suggested operating pressure limit was exceeded at higher flow rates, such as with an 18-gauge cannula at 8 mL/s instead of 6 mL/s using warmed iomeprol 400. Even with pressures of up to 159.7 psi, none of the IVCs ruptured.

Heating of CM effectively reduces MIPs using power injection in common IVCs. Although the manufacturer's suggested MIP was exceeded at higher flow rates, safe CM injection seems to be possible even in small cannulas using power injection. The compilation of the obtained data is meant to serve as guidance for future decisions on parameters of the power injection of iodinated CM.

A multimodal CT protocol provides a comprehensive noninvasive survey of acute stroke patients with accurate demonstration of the site of arterial occlusion and its hemodynamic tissue status. It combines widespread availability with the ability to provide functional characterization of cerebral ischemia, and could potentially allow more accurate selection of candidates for acute stroke reperfusion therapy. This article discusses the individual components of multimodal CT and addresses the potential role of a combined multimodal CT stroke protocol in acute stroke therapy.