Flat-panel Detector Perfusion Imaging and Conventional Multidetector Perfusion Imaging in Patients with Acute Ischemic Stroke : A Comparative Study

PURPOSE

Flat-panel detector computed tomography (FDCT) is increasingly used in (neuro)interventional angiography suites. This study aimed to compare FDCT perfusion (FDCTP) with conventional multidetector computed tomography perfusion (MDCTP) in patients with acute ischemic stroke.

METHODS

In this study, 19 patients with large vessel occlusion in the anterior circulation who had undergone mechanical thrombectomy, baseline MDCTP and pre-interventional FDCTP were included. Hypoperfused tissue volumes were manually segmented on time to maximum (Tmax) and time to peak (TTP) maps based on the maximum visible extent. Absolute and relative thresholds were applied to the maximum visible extent on Tmax and relative cerebral blood flow (rCBF) maps to delineate penumbra volumes and volumes with a high likelihood of irreversible infarcted tissue ("core"). Standard comparative metrics were used to evaluate the performance of FDCTP.

RESULTS

Strong correlations and robust agreement were found between manually segmented volumes on MDCTP and FDCTP Tmax maps (r = 0.85, 95% CI 0.65-0.94, p < 0.001; ICC = 0.85, 95% CI 0.69-0.94) and TTP maps (r = 0.91, 95% CI 0.78-0.97, p < 0.001; ICC = 0.90, 95% CI 0.78-0.96); however, direct quantitative comparisons using thresholding showed lower correlations and weaker agreement (MDCTP versus FDCTP Tmax 6 s: r = 0.35, 95% CI -0.13-0.69, p = 0.15; ICC = 0.32, 95% CI 0.07-0.75). Normalization techniques improved results for Tmax maps (r = 0.78, 95% CI 0.50-0.91, p < 0.001; ICC = 0.77, 95% CI 0.55-0.91). Bland-Altman analyses indicated a slight systematic underestimation of FDCTP Tmax maximum visible extent volumes and slight overestimation of FDCTP TTP maximum visible extent volumes compared to MDCTP.

CONCLUSION

FDCTP and MDCTP provide qualitatively comparable volumetric results on Tmax and TTP maps; however, direct quantitative measurements of infarct core and hypoperfused tissue volumes showed lower correlations and agreement.

Influence of the integrity of circle of Willis on asymptomatic or mild patients with first diagnosed chronic internal carotid artery occlusion

BACKGROUND

In order to identify individuals with chronic internal carotid artery occlusion (CICAO), it is essential to understand the integrity of the circle of Willis (CoW). This understanding is important as it may determine the potential benefits of active medical and endovascular treatments.

PURPOSE

The objective of this study is to assess whether diminished integrity of the CoW can serve as a useful marker for identifying individuals with more severe impairment in cerebral blood perfusion and a higher incidence of cerebral infarction among asymptomatic or mildly affected patients with CICAO.

MATERIALS AND METHODS

We conducted a retrospective review of asymptomatic or mildly affected patients with newly diagnosed CICAO who did not receive reperfusion therapies. The categorization of patients into good or poor integrity groups was based on the assessment of CoW integrity using CTA. We evaluated the volume and value of prolonged time to peak (TTP) in both groups, as well as the occurrence of new cerebral infarctions. Our analysis involved multivariate regression and receiver operating characteristic (ROC) analysis.

RESULTS

Hemodynamic abnormalities characterized by prolonged TTP were observed in the affected side's blood supply region in all 38 patients. There was a notable difference in the volume and value of prolonged TTP between the two groups (P < 0.001). Correlation analyses based on CTP and CTA parameters revealed a negative relationship between CoW scores and both the abnormal volume (r = -0.624, P = 0.000) and value (r = -0.589, P = 0.000) of prolonged TTP. Upon multivariable adjustment, the independent predictors for new cerebral infarction and higher volume of prolonged TTP were solely the CoW status, with respective estimates of (b = 6.05; 95% confidence interval [CI]: 1.619, 22.619; P = 0.007) and (b = 35.486; 95% CI: 4.697, 268.088; P = 0.001).

CONCLUSION

Assessing the integrity of the CoW is crucial in evaluating abnormal perfusion in asymptomatic or mildly affected individuals who are newly diagnosed with CICAO and have not undergone reperfusion therapy.

Evaluation of Myocardial Microcirculation in Rats under a High-Altitude Hypoxic Environment by Computed Tomography Myocardial Perfusion Imaging

This study aims to examine the changes in myocardial microcirculation in rats in a high-altitude hypoxic environment via computed tomography (CT) myocardial perfusion imaging technology. Rats in two groups were raised in different environments from 4 weeks of age for a period of 24 weeks. At 28 weeks of age, both groups underwent CT myocardial perfusion scanning, and the following myocardial perfusion parameters were measured: time to peak (TTP), mean transit time (MTT), blood flow (BF), and blood volume (BV). Following the scan, the rats were sacrificed, the cardiac index and right ventricular hypertrophy index were obtained, and hematoxylin-eosin (HE) staining was utilized to observe the pathological changes in the myocardium. In the group of rats that are subject to a high-altitude hypoxic environment for 24 weeks (the high-altitude group), the TTP and MTT values were increased (P < 0.05), the BF and BV values were lower (P < 0.05), the right heart mass was higher (P < 0.05) than that in the low-altitude group. As shown by the pathological results of HE staining, the gap between cardiomyocytes in the high-altitude group was widened, the arrangement of cardiomyocytes was irregular, and the cells were filled with a few fat vacuoles. The myocardial microcirculation is altered in a high-altitude hypoxic environment. In particular, the myocardium is in a state of inadequate perfusion, the BF in the myocardium slows down, and the right heart displays compensatory hypertrophy.

Independent Significance of Visual Assessment of Perfusion CT Maps in Anterior Circulation Stroke Patients Treated with Mechanical Thrombectomy

BACKGROUND

In the absence of an automated software analysis, the role of computed tomography perfusion (CTP) in a real time clinical practice is not well established. We evaluated the clinical significance of a widely accessible and simple visual grading scale of CTP in the anterior circulation of acute ischemic stroke (AIS) patients treated with mechanical thrombectomy (MT).

METHODS

The single center consecutive CT investigations of AIS patients treated with MT in the anterior circulation have been evaluated retrospectively. ASPECT score and collateral circulation evaluation based on the Maas score were determined. Time to peak parametric maps, derived from CTP, were graded into four categories, from least to most favorable. The primary endpoint was functional outcome evaluated as modified Rankin Scale (mRS) ≤ 2 at 90 days after MT.

RESULTS

We included 318 patients in the analysis; 142 (45%) patients had mRS ≤ 2 after 90 days, mortality rate was 24%. Higher CTP and Maas score were significantly correlated with better clinical outcome (Pearson χ² 25.0 and 37.7, respectively; p < 0.01). Collateral circulation and CTP grades were strongly interrelated (Pearson χ² 78.6; p < 0.01). The CTP grade demonstrated statistically significant independent correlation with the clinical outcome irrespective of the collateral circulation grade, ASPECT score and age (OR 2.5; p = 0.011). The correlation was more pronounced in patients with normal collateral circulation (OR 3.27; p = 0.029).

CONCLUSION

We demonstrated that both visually graded CTP and collateral circulation grade strongly correlated with the clinical outcome of MT in the anterior circulation of AIS patients. Importantly, CTP correlated with the clinical outcome independent of the collateral circulation.

Responses to oral glucose challenge differ by physical activity volume and intensity: A pilot study

BACKGROUND

One-hour postprandial hyperglycemia is associated with increased risk of type 2 diabetes and cardiovascular disease. Physical activity (PA) has short-term beneficial effects on post-meal glucose response. This study compared the oral glucose tolerance test results of 3 groups of people with habitually different levels of PA.

METHODS

Thirty-one adults without diabetes (age 25.9 ± 6.6 years; body mass index 23.8 ± 3.8 kg/m²; mean ± SD) were recruited and divided into 3 groups based on self-reported PA volume and intensity: low activity < 30 min/day of moderate-intensity activity (n = 11), moderately active ≥ 30 min/day of moderate-intensity PA (n = 10), and very active ≥ 60 min/day of PA at high intensity (n = 10). Participants completed an oral glucose tolerance test (50 g glucose) with capillary blood samples obtained at baseline, 15 min, 30 min, 45 min, 60 min, 90 min, and 120 min post-ingestion.

RESULTS

There were no significant differences between groups for age or body fat percentage or glycated hemoglobin (p > 0.05). The groups were significantly different in terms of baseline glucose level (p = 0.003) and, marginally, for gender (p = 0.053) and BMI (p = 0.050). There was a statistically significant effect of PA on the 1-h postprandial glucose results (p = 0.029), with differences between very active and low activity groups (p = 0.008) but not between the moderately active and low activity groups (p = 0.360), even when baseline glucose level and gender differences were accounted for. For incremental area under the curve there was no significant effect of activity group once gender and body fat percentage had been accounted for (p = 0.401). Those in the low activity group took 15 min longer to reach peak glucose level than those in the very active group (p = 0.012).

CONCLUSION

The results suggest that high levels of PA have a beneficial effect on postprandial blood glucose profiles when compared to low and moderate levels of activity.

Correlation between perfusion state and angiogenesis indexes in gastric cancer

BACKGROUND

Accurate evaluation of microcirculation perfusion in tumor tissue is of great significance for clinical treatment and prognosis evaluation. Contrast-enhanced ultrasonography (CEUS) is a highly sensitive means of monitoring microcirculation perfusion, which can objectively reflect the microcirculation perfusion state of tumor tissue and provide reliable hemodynamic information for clinical diagnosis and treatment.

AIM

To evaluate the perfusion status of gastric cancer (GC) by CEUS, and to explore the correlation between the perfusion status and the indexes of angiogenesis.

METHODS

Sixty-six patients with GC were selected as study subjects (GC group). All patients were examined by CEUS 3 d before operation. The enhanced intensity (EI) and time to peak (TTP) of GC and tumor-adjacent normal tissues were measured by time-intensity curve analysis. The levels of vascular endothelial growth factor (VEGF) and angiopoietin-2 (Ang-2) were measured by enzyme-linked immunosorbent assay (ELISA), and the microvessel density (MVD) was measured after operation. Seventy-two healthy volunteers were selected as a control group for comparative analysis.

RESULTS

The EI and MVD were significantly higher and the TTP was significantly shorter in GC tissue than in normal tissue (P < 0.05). VEGF and Ang-2 levels were significantly higher in the GC group than in the control group (P < 0.05). EI had a positive correlation with VEGF, Ang-2, and MVD (r = 0.85, 0.81, and 0.88, respectively; P < 0.05), and TTP had a negative correlation with VEGF, Ang-2, and MVD (r = -0.72, -0.73, and -0.86, respectively; P < 0.05).

CONCLUSION

CEUS can dynamically evaluate the perfusion status of GC, and CEUS blood flow parameters have a good correlation with VEGF, Ang-2, and MVD. CEUS can provide a noninvasive imaging method for clinical evaluation of the angiogenesis status of GC.

Contrast-to-Noise Ratio Optimization in Coronary Computed Tomography Angiography: Validation in a Swine Model

RATIONALE AND OBJECTIVES

The accuracy of coronary computed tomography (CT) angiography depends upon the degree of coronary enhancement as compared to the background noise. Unfortunately, coronary contrast-to-noise ratio (CNR) optimization is difficult on a patient-specific basis. Hence, the objective of this study was to validate a new combined diluted test bolus and CT angiography protocol for improved coronary enhancement and CNR.

MATERIALS AND METHODS

The combined diluted test bolus and CT angiography protocol was validated in six swine (28.9 ± 2.7 kg). Specifically, the aortic and coronary enhancement and CNR of a standard CT angiography protocol, and a new combined diluted test bolus and CT angiography protocol were compared to a reference retrospective CT angiography protocol. Comparisons for all data were made using box plots, t tests, regression, Bland-Altman, root-mean-square error and deviation, as well as Lin's concordance correlation.

RESULTS

The combined diluted test bolus and CT angiography protocol was found to improve aortic and coronary enhancement by 26% and 13%, respectively, as compared to the standard CT angiography protocol. More importantly, the combined protocol was found to improve aortic and coronary CNR by 29% and 20%, respectively, as compared to the standard protocol.

CONCLUSION

A new combined diluted test bolus and CT angiography protocol was shown to improve coronary enhancement and CNR as compared to an existing standard CT angiography protocol.

Potential Effect of Prolonged Sevoflurane Anesthesia on the Kinetics of [11C]Raclopride in Non-human Primates

Purpose

Positron emission tomography (PET) in non-human primates (NHP) is commonly performed under anesthesia, with sevoflurane being a widely used inhaled anesthetic. PET measurement in NHP can be repeated, and a difference in radioligand kinetics has previously been observed between the first and second PET measurement on the same day using sevoflurane anesthesia. In this study, we evaluated the effect of prolonged sevoflurane anesthesia on kinetics and binding potential (BP_ND) of [¹¹C]raclopride in NHP.

Procedures

Three cynomolgus monkeys underwent two to three PET measurements with [¹¹C]raclopride under continuous sevoflurane anesthesia on the same day. The concentration of sevoflurane was adjusted according to the general conditions and safety parameters of the NHP. Time to peak (TTP) radioactivity in the striatum was estimated from time-activity curves (TACs). The BP_ND in the striatum was calculated by the simplified reference tissue model using the cerebellum as reference region.

Results

In each NHP, the TTP became shorter in the later PET measurements than in the first one. Across all measurements (n = 8), concentration of sevoflurane correlated with TTP (Spearman’s ρ = − 0.79, p = 0.03), but not with BP_ND (ρ = − 0.25, p = 0.55).

Conclusions

These data suggest that sevoflurane affects the shape of TACs but has no evident effect on BP_ND in consecutive PET measurements.

On the Significance of Systolic Flow Waveform on Aortic Valve Energy Loss

This study aims to quantitatively and qualitatively assess energy dissipation in the aortic valve as a function of systolic aortic flow waveform representing pathologies where flow time-to-peak is delayed. A bioprosthetic valve was tested in the aortic position of a left-heart simulator under physiological pressure and flow conditions. The flow loop piston pump was programmed to generate three different flow waveforms each with a different peak time annotated as early peak (EP) with a rapid acceleration, mid peak (MP) and late peak (LP) with a rapid deceleration. Energy dissipation was calculated from flow and pressure measurements while sinus vorticity dynamics were evaluated using time-resolved planar particle image velocimetry. Average pressure gradients during systole are found 30.2 ± 0.19, 30.7 ± 0.25 and 32.9 ± 0.29 mmHg and average dissipation over systole is found 0.95 ± 0.026, 1.05 ± 0.034 and 1.25 ± 0.043 W for EP, MP and LP respectively. As systole's acceleration phase is slower, sinus vortices are more likely to form, necessitating more energy exchange from shear layers inducing more viscous dissipation. EP found in healthy individuals is superior in terms of reducing energy dissipation and increasing aortic valve efficiency. In the context of possible left ventricular dysfunction and aortic stenosis, this means that delayed time-to-peak in the aortic flow waveform seen is not compensatory.

Early Hemodynamic Changes Based on Initial Color-Coding Angiography as a Predictor for Developing Subsequent Symptomatic Vasospasm After Aneurysmal Subarachnoid Hemorrhage

INTRODUCTION

Prediction of vasospasm after aneurysmal subarachnoid hemorrhage (aSAH) remains imperfect and currently relies on clinical and radiographic characteristics. Whether early hemodynamic changes may refine risk stratification for delayed vasospasm (DV) after aSAH was analyzed.

METHODS

Patients with aSAH (n = 53) and a control group with unruptured intracranial aneurysms (UIA) (n = 12) with initial color-coding angiography at admission were included in this study (n = 65). Clinical and radiologic data were collected, and uni- and multivariate analysis was used to correlate the occurrence of DV (manifesting clinically or detected with transcranial Doppler or angiography) with hemodynamic features of the initial angiography including Tmax and mean transit times (MTTs).

RESULTS

In the aSAH patient cohort, 37 of 53 patients with aSAH (70%) developed DV. After we controlled for the effects of age, Hunt and Hess grade, and modified Fisher grade, patients with DV had a shorter mean region of interest peak time (Tmax) of the anterior cerebral artery A2 segment (P = 0.036) and the middle cerebral artery M1 (P = 0.045) and M3 (P = 0.013) segments. Mean MTTs between internal carotid artery to middle cerebral artery M3 segment (P = 0.026) was also significantly shorter in patients with DV when compared with controls.

CONCLUSIONS

Tmax and MTT on angiography within 48 hours of aneurysm rupture before treatment provide an early quantitative assessment in patients with aSAH and in this small study were predictive for the development of subsequent symptomatic DV. Early identification of patients with aSAH at greatest risk of DV may ameliorate clinical outcome through timely, selective implementation of aggressive prophylactic therapy to prevent the effects of DV.

Efficacy of Perfusion Computed Tomography (PCT) in Differentiating High-Grade Gliomas from Low Grade Gliomas, Lymphomas, Metastases and Abscess

INTRODUCTION

Tumoural angioneogenesis and its quantification are important in predicting the tumour grade and in the management with respect to the treatment available and to assess the response to treatment and the prognosis. It also plays major role in the growth and spread of tumours. Hence, a need arises for non-invasive in vivo methods to assess tumour angioneogenesis and tumour grade at the time of presentation and for monitoring the response during treatment and follow up. In this regard Perfusion Computed Tomography (PCT) can be easily added into routine CT studies to obtain such information on lesion physiology along with its morphology.

AIM

Prospective evaluation of the efficacy of PCT in differentiating high grade gliomas from low grade glioma lymphomas, metastases and abscess.

MATERIALS AND METHODS

Perfusion CT was performed in 68 patients (17 high-grade gliomas, 10 low-grade gliomas, 7 lymphomas, 27 metastases and 7 abscess). Perfusion parameters which include Cerebral Blood Volume (CBV), Cerebral Blood Flow (CBF), Mean Transit Time (MTT) and Time To Peak (TTP) were derived both from the lesion and the normal parenchyma and were Normalized (n) by obtaining the ratio. Statistical analysis for high grade versus low-grade gliomas, high grade gliomas versus lymphomas, metastases and abscess was performed.

RESULTS

Difference in the mean nCBV and nCBF in high grade gliomas were statistically significant from low grade gliomas with cut off of > 3.07 for nCBV and > 2.08 for nCBF yielding good sensitivity and specificity. Difference in the mean nCBV and nMTT in the lymphomas were statistically significant from high grade gliomas (p<0.05) with cut off of <3.40 for nCBV and >1.83 for nMTT yielding good sensitivity and specificity. Difference in the mean nCBV and nMTT in the metastases were statistically significant from high grade gliomas (p<0.05) with cut off of >4.95 for nCBV and >1.88 for nMTT yielding a fair sensitivity and specificity. No statistical significant difference seen among the parameters in differentiating high grade gliomas and abscess.

CONCLUSION

Cerebral PCT greatly adds to the diagnostic accuracy when the diagnosis of a common intra-axial lesion based on morphological characters becomes uncertain.

Mismatch of delayed perfusion volume between TTP and Tmax map of perfusion MRI

OBJECTIVE

To look for another set of parameters to predict the change in infarct size in acute stroke patients with a perfusion-weighted imaging (PWI)-diffusion-weighted imaging (DWI) mismatch.

MATERIALS AND METHODS

We reviewed 54 patients who had PWI-DWI mismatch and vascular occlusion on initial MRI and no recanalization of occluded vessel.

RESULTS

Time-to-peak and time-to-max (TTP-Tmax) perfusion mismatch volume was independently significant as a correlate of infarct volume change (P=.004).

CONCLUSIONS

The finding of a large TTP-Tmax perfusion delay mismatch volume in patients with acute stroke who have a PWI-DWI mismatch on an initial MRI may predict that the infarct volume will not increase despite persistent vascular occlusion.

Influence of repetitive contrast agent injections on functional and molecular ultrasound measurements

Quantitative contrast-enhanced ultrasound plays an important role in tumor characterization and treatment assessment. Besides established functional ultrasound techniques, ultrasound molecular imaging using microbubbles targeted to disease-associated markers is increasingly being applied in pre-clinical studies. Often, repeated injections of non-targeted or targeted microbubbles during the same imaging session are administered. However, the influence of repeated injections on the accuracy of the quantitative data is unclear. Therefore, in tumor-bearing mice, we investigated the influence of multiple injections of non-targeted microbubbles (SonoVue) on time to peak and peak enhancement in liver and tumor tissue and of vascular endothelial growth factor receptor 2 (VEGFR2)-targeted contrast agents (MicroMarker) on specific tumor accumulation. We found significantly decreasing values for time to peak and a tendency for increased values for peak enhancement after multiple injections. Repeated injections of VEGFR2-targeted microbubbles led to significantly increased tumor accumulation, which may result from the exposure of additional binding sites at endothelial surfaces caused by mechanical forces from destroyed microbubbles.

Hypercoagulation following brain death cannot be reversed by the neutralization of systemic tissue factor

BACKGROUND

Cerebral injury and brain death is associated with apparent hypercoagulation and poor organ outcome. This experimental study challenges the hypotheses that i) brain death causes hypercoagulation and microvascular thrombosis and that ii) neutralizing systemic tissue factor (TF) by in vitro addition of a TF inhibitor (recombinant active site-inhibited factor VIIa (ASIS)) can reverse the hypercoagulable profile.

METHODS

Using a validated pig model of intracranial hemorrhage and brain death, 20 pigs were randomized to either control or brain death. The primary endpoints were coagulation parameters measured with whole blood thromboelastometry (ROTEM), thrombin generation and a porcine TF-sensitive plasma clotting time assay. In vitro spiking experiments with ASIS were performed in parallel with the latter two assessments. The kidneys were examined histologically for microvascular thromboses.

RESULTS

Brain death induced hypercoagulation, as demonstrated with ROTEM, thrombin generation, and reduced TF-sensitive plasma clotting time. In vitro inhibition of TF with ASIS did not reverse the hypercoagulation. No microvascular thromboses were found in the kidneys.

CONCLUSION

Brain death causes hypercoagulation; however, inhibition of TF does not reverse the coagulopathy. Thus, TF release does not seem to be the primary cause of this hypercoagulation. Minor changes in the levels of protein C suggest that the protein C pathway may be linked to the observed coagulopathy.

Initial 'TTP Map-Defect' of Computed Tomography Perfusion as a Predictor of Hemorrhagic Transformation of Acute Ischemic Stroke

Background

Hemorrhagic transformation (HT) following acute ischemic stroke is a major problem, especially for the indication of reperfusion therapy including intravenous administration of recombinant tissue plasminogen activator (IV rt-PA). The specific predictive factors of HT have not yet been established. The present study evaluated the findings of computed tomography perfusion (CTP) images as predictors of subsequent HT to identify patients with low HT risk for reperfusion therapy such as IV rt-PA.

Methods

We retrospectively reviewed 68 consecutive stroke patients (41 males; mean age 72.9 years) with steno-occlusive lesions in the major trunk, including 10 patients who underwent IV rt-PA. Each HT was detected on a follow-up T2*-weighted magnetic resonance image until 2 weeks after stroke onset and categorized into four groups [hemorrhagic infarction (HI) type 1 and 2, and parenchymal hematoma (PH) type 1 and 2] according to the European Cooperative Acute Stroke Study (ECASS) classification. We assessed clinical features and radiological findings between the HT and non-HT groups or the PH2 and non-PH2 groups. The efficacy of initial time to peak (TTP) mapping of CTP for predicting HT or PH2 was evaluated.

Results

Thirty-four patients (50%) developed subsequent HT: 18 (52.9%) had HI and 16 (47.1%) had PH, including 9 PH2 patients (13.2%). IV rt-PA was not significantly associated with HT or PH2 occurrence. Forty of the 68 patients (59%) revealed defect areas on the initial TTP mapping (TTP map-defect), and 34 of these 40 patients (85%) developed secondary HT and 9 patients (22.5%) developed PH2. Initial ‘TTP map-defect’ was significantly associated with the occurrence of HT (p < 0.0001) and PH2 (p = 0.0070). Thirty of the 34 patients (88.2%) in the HT group experienced delayed recanalization of the occluded vessels, in contrast to only 8 of the 34 patients (23.6%) in the non-HT group. All patients of the PH2 group showed recanalization (p = 0.0042). In 40 ‘TTP map-defect’-positive patients, delayed recanalization was associated with the occurrence of HT (p < 0.0001) and PH2 (p = 0.0491). All 28 patients without ‘TTP map-defect’ did not develop HT, including 8 patients (28.6%) with delayed recanalization.

Conclusions

Initial ‘TTP map-defect’ of CTP could accurately predict HT risk including PH2 risk and identify low-risk patients even in the delayed period.