Mismatch Regions Research Articles

Abstract LB067: A confident and operator-independent deep segmentation model to measure residual tumor volume in the follow-up MRIs for glioblastoma

Abstract Introduction: Magnetic resonance imaging (MRI) is the most common tool to examine glioblastoma. Preoperative MRI can be used to initial diagnosis, and surgery planning, while follow-up MRIs can be used to evaluate treatment responses, identify recurrency, and detect side effects. The follow-up MRIs are usually taken after the first-line therapy, such as maximal safe resection. In the past, radiologists manually segment the tumor regions from normal brain tissue on follow-up MRIs, which is time-consuming, error-prone, and challenging. Several deep-learning (DL) models have been developed utilizing preoperative images, but their performance has yet to be evaluated on follow-up MRIs. In this research, we built the largest follow-up MRI cohort (311 patients) to assess these DL models and their generalizability and performance on independent preoperative and follow-up images. We also made the first follow-up-based deep learning models for this specific task. Methods: All evaluation deep learning models (10 models) were trained by the Brain Tumor Segmentation challenge 2020 (BraTS’20) and evaluated by fifty pairs of preoperative and follow-up scans from our institution. The segmentation form our institution is evaluated by board certified radiologist. MRIs in the BraTS’20 dataset were all preoperative scans. After the evaluation, we randomly assigned 264 patients’ scans from our institution to the training dataset and 47 patients’ scans to the testing dataset. We compared three types of models in our follow-up deep learning model, including 1) UNet-3D, 2) UNet-3D+transfer-learning, and 3) UNet-3D+transfer-learning+baysian-learning. The benchmark for all models was the Dice similarity coefficient (DSC). DSC can measure the spatial overlap between model prediction and ground truth. The value of DSC is between zero to one. Zero means no overlap and one indicates complete overlap. Results: Our study demonstrates that the BraTS'20 trained models' performance decreased by 13.05% in independent preoperative MRI scans and 19.04% in follow-up MRI scans. The most significant mismatch regions were FLAIR hyperintense regions (3.68% drop in independent preoperative scans and 10.61% drop in independent follow-up scans) and Non-enhancing core (5.20% drop in independent preoperative scans and 11.99% drop in independent follow-up scans). Our best model can achieve the best DSC among three tumor regions compared to all evaluation models (FLAIR hyperintense regions: DSC 0.77 V.S. DSC 0.58; Enhancing tumor region: DSC 0.87 V.S. DSC 0.68; Non-enhancing tumor region: DSC 0.92 V.S. DSC 0.55). Conclusion: Maximal safe resection induced brain structure change, decreasing the performance of the preoperative-based DL model. Implementing a follow-up MRI-based segmentation model is essential to make accurate and generalizable results to address structural changes after maximal safe resection. Our follow-up DL model demonstrates the DSC score can be recovered. We commit to further developing the tool to assist radiologists in handling follow-up MRIs for glioblastoma patients. Citation Format: Kang Lin Hsieh, Tanjida Kabir, Luis Nunez-Rubiano, Yu-Chun Hsu, Yu Cai, Juan Rodriguez Quintero, Octavio Arevalo, Kangyi Zhao, Jackie Zhang, Jiguang Zhu Zhu, Roy Riascos, Xioaqian Jiang, Shayan Shams. A confident and operator-independent deep segmentation model to measure residual tumor volume in the follow-up MRIs for glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr LB067.

Tissue perfusion of the kurtosis/diffusion mismatch differs from the central core and peripheral regions in acute cerebral infarction patients.

Despite its wide adoption in stroke imaging, the diffusion-weighted imaging (DWI) lesion is heterogeneous. The emerging diffusion kurtosis imaging (DKI) has been postulated to resolve the graded DWI lesion. To determine the perfusion characteristics of the central infarction core, kurtosis/diffusion mismatch, and peripheral regions. Patients with acute ischemic stroke underwent DWI, DKI, and perfusion-weighted imaging (PWI) scans. The patients were divided into mean kurtosis (MK)/mean diffusivity (MD) match and mismatch groups. Perfusion parameters were measured in the MK/MD lesion and peripheral areas in the MK/MD match group. We also analyzed perfusion status in the MK/MD lesion mismatch area for the mismatch group. A total of 40 eligible patients (24 MK/MD match and 16 MK/MD mismatch) were enrolled in the final data analysis. The MTT and TTP progressively decreased, while the cerebral blood flow (CBF) and cerebral blood volume (CBV) increased from the central to peripheral areas. In addition, CBF in the MK/MD mismatch region was significantly higher than that in the central region (P < 0.05), but similar to the peripheral region. Furthermore, CBV in the MK/MD mismatch region did not differ significantly from that of the central region, but both were significantly lower than that of the peripheral area (P < 0.05). The MK/MD mismatch region had blood flow similar to the peripheral region but with a reduced blood volume, indicating that it was less ischemic from the infarction core, albeit insufficient collateral circulation.

Measuring spatial accessibility to refuge green space after earthquakes: A case study of Nanjing, China.

The construction of refuge spaces in rapidly urbanizing historic cities is a challenging task owing to their complex urban form, unique urban fabric, and historic preservation requirements. Refuge green space (RGS) is a green space that can serve as an emergency shelter in cities, providing a flexible means to increase the emergency shelter capacity for rapidly urbanized historic cities. After major earthquakes, spatial accessibility to GRSs is a critical planning strategy for disaster prevention and emergency response in historic cities. To match the RGS planning with the emergency service demand, we must examine the spatial disparity in access to existing RGSs. In this study, the urban area of Nanjing was selected as the target region to analyze the spatial disparity in access to RGSs using the Gaussian two-step floating catchment area method at four evacuation times (10, 20, 30, and 60 min). The results showed that the spatial accessibility exhibited clustering characteristics, where high-accessibility spaces were mainly distributed in the northern and southern regions of Nanjing. The increase in the evacuation time improved accessibility to RGSs, but the existing RGSs still could not sufficiently satisfy the emergency shelter needs of citizens. Based on the bivariate local Moran’s I analysis of the RGS accessibility and population density, the spatial mismatch regions were dominant in the center of the urban area. These findings not only are expected to assist emergency planners by improving their strategic plans for emergency shelter investment in Nanjing and their ability to respond to catastrophic earthquakes, but also provide a strong reference for the construction of a safe environment in other rapidly developing historic cities that face earthquake threats.

Reconfigurable-Based Fault-Tolerant Control for Continuous-Time Markov Jump Piecewise-Affine Systems with Allowable Switching Paths

In this paper, the reconfigurable control design problem is studied for a class of continuous-time Markov jump piecewise-affine (PWA) systems with sensor and actuator faults. A reconfiguration block is designed to recover mean-square input-to-state stability (ISS) of the faulty closed-loop system under virtual sensor and virtual actuator. Then, a novel algorithm for computing all the allowable switching paths (ASPs) is developed to overcome the issues of redundant empty paths and mismatch regions, and a S-procedure with the ellipsoidal outer approximation estimation is employed to cope with the affine term. Furthermore, a nonlinear approximation is introduced using the PWA technique to approximate the faulty Markov jump nonlinear systems. Finally, one example is illustrated to demonstrate the effectiveness and advantages of the designed reconfigurable control strategy with an ASPs algorithm.

Capping Protein Regulator and Myosin 1 Linker 3 (CARMIL3) as a Molecular Signature of Ischemic Neurons in the DWI-T2 Mismatch Areas After Stroke.

Ischemic stroke with a mismatch between diffusion-weighted imaging (DWI) and fluid-attenuated inversion recovery (FLAIR) or T2-weighted images indicates onset within 4.5 h, but the pathological substrates in the DWI-T2 mismatch and T2(+) areas remain elusive. In this study, proteomics was used to explore (1) the protein expression profiles in the T2(+), mismatch, and contralateral areas, and (2) the protein with the highest expression in the T2(+) area in the brains of male Sprague-Dawley rats within 4.5 h after middle cerebral artery occlusion (MCAO). The expression of the candidate protein was further validated in (1) rat brain subjected to MCAO, (2) rat primary cortical neuronal culture with oxygen-glucose deprivation (OGD), and (3) infarcted human brain tissues. This study showed that apoptosis was observed in the T2(+) and mismatch regions and necroptosis in the T2(+) region of rat brains after MCAO. We identified capping protein regulator and myosin 1 linker 3 (CARMIL3) as the candidate molecule in the T2(+) and mismatch areas, exclusively in neurons, predominantly in the cytoplasm, and most abundant in the mismatch area. The CARMIL3(+) neurons and neurites in the mismatch and T2(+) areas were larger than those in the control area, and associated with (1) increased expression of sulfonylurea receptor 1 (SUR1), indicating edema, (2) accumulation of p62, indicating impaired autophagy, and (3) increase in 8-hydroxy-2′-deoxyguanosine (8-OHdG), indicating oxidative stress. The increased expression of CARMIL3 was validated in a cell model of cortical neurons after OGD and in infarcted human brain tissues. In conclusion, this study shows that the mismatch and T2(+) areas within 4.5 h after ischemia are characterized by upregulated expression of CARMIL3 in neurons, particularly the mismatch area, which is associated with neuronal edema, impaired autophagy, and oxidative stress, indicating that CARMIL3 serves as a molecular signature of brain ischemia.

Quantitative Multicomponent T2 Relaxation Showed Greater Sensitivity Than Flair Imaging to Detect Subtle Alterations at the Periphery of Lower Grade Gliomas.

PurposeTo demonstrate that quantitative multicomponent T2 relaxation can be more sensitive than conventional FLAIR imaging for detecting cerebral tissue abnormalities.MethodsSix patients affected by lower-grade non-enhancing gliomas underwent T2 relaxation and FLAIR imaging before a radiation treatment by proton therapy (PT) and were examined at follow-up. The T2 decay signal obtained by a thirty-two-echo sequence was decomposed into three main components, attributing to each component a different T2 range: water trapped in the lipid bilayer membrane of myelin, intra/extracellular water and cerebrospinal fluid. The T2 quantitative map of the intra/extracellular water was compared with FLAIR images.ResultsBefore PT, in five patients a mismatch was observed between the intra/extracellular water T2 map and FLAIR images, with peri-tumoral areas of high T2 that typically extended outside the area of abnormal FLAIR hyper-intensity. Such mismatch regions evolved into two different types of patterns. The first type, observed in three patients, was a reduced extension of the abnormal regions on T2 map with respect to FLAIR images (T2 decrease pattern). The second type, observed in two patients, was the appearance of new areas of abnormal hyper-intensity on FLAIR images matching the anomalous T2 map extension (FLAIR increase pattern), that was considered as asymptomatic radiation induced damage.ConclusionOur preliminarily results suggest that quantitative T2 mapping of the intra/extracellular water component was more sensitive than conventional FLAIR imaging to subtle cerebral tissue abnormalities, deserving to be further investigated in future clinical studies.

A new perspective to map the supply and demand of artificial night light based on Loujia1-01 and urban big data

The notable increase in artificial night light (ANL) induced by the rapid urbanization process has been widely studied, but a deep understanding of the supply and demand status of ANL is still lacking. This paper attempts to map the supply and demand of ANL from the human perspective by using advanced Loujia1-01 nighttime imagery and social media derived population density (PD) data, which provides a new tool for light regulation in urban management. The bivariate clustering based k-means algorithm and template matching technique are integrated to delineate mismatch regions at the block scale to further analyze the underlying reason for unbalanced status. The results showed that the high supply but low demand (HSLD) ANL status was the leading component in the mismatch regions, occupying more than 650,000 ha and mainly occurring in the city center. The HSLD proportion was considerable in terms of public services (44%), commercial (40%), industrial (39%), transportation (56%), and green space areas (53%). Moreover, the HSLD area notably increased 946 ha over time from 18:00 to 22:00. The measurements for validation obtained by field investigation showed highly linear relationship with ANL (R2 = 0.75) and PD (R2 = 0.62), and the mapping results were consistent with the actual conditions. This study reveals the highly unbalanced ANL status, and appeals to planners for the establishment of optimal lighting regulations to alleviate disruptive effects.

The chromosomal basis of species initiation: Prdm9 as an anti-speciation gene

Mechanisms initiating a branching process that can lead to new species are broadly classified as chromosomal and genic. Chromosomal mechanisms were supported by breeding studies involving exchanges of individual chromosomes between mouse subspecies. There were also studies of the rapidly mutating mouse PR/SET-domain 9 (prdm9) gene, which encodes PRDM9, a protein targeting DNA recombination hotspots. When PRDM9 is bound symmetrically with equal strength, the meiotic repair of mutations in one parental strand, based on information on the allelic strand (conversion), would seem to be unbiased in discriminating between strands. So mismatches detected between pairing paternal and maternal DNA strands (heteroduplexes) would undergo unbiased conversions (to homoduplexes). This would leave uncertainty on whether a mutation had been corrected or compounded. However, a hypothetical tagging of mismatch regions, so that both strands are epigenetically marked as uncertain, would make it possible over numerous generations for mutations to be corrected (biased conversions) whenever asymmetry is detected. Thus variation would decrease and members of a species would remain within its bounds. Intriguingly, new experimental studies show that, when chromosomally interpreted, PRDM9 also works through asymmetrical epigenetic labelling to confine members to species bounds. To the extent that the experimentally observed and hypothetical anti-speciation asymmetries can be related, chromosomal mechanisms are further supported.

Impaired myocardial microcirculation in the flow-glucose metabolism mismatch regions in revascularized acute myocardial infarction

BackgroundIn successfully revascularized acute myocardial infarction (AMI), microvascular function in a myocardial flow-glucose metabolism mismatch pattern has not been reported. We aimed to elucidate myocardial flow reserve (MFR) and myocardial viability in mismatch segments. Methods18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and adenosine stress 13N-ammonia PET were performed in eighteen AMI patients to evaluate myocardial glucose metabolism, myocardial blood flow (MBF), and MFR. Infarct segments were classified into 3 groups: normal (preserved resting MBF), mismatch (preserved FDG uptake but reduced resting MBF), and match (reduced FDG uptake and resting MBF). Regional wall motion score (WMS) was assessed immediately after reperfusion and recovery periods. ResultsMFR in the mismatch group was significantly lower than that in non-infarct-related segments (1.655 ± 0.516 vs 2.282 ± 0.629, P < .01) and similar to that in the match group (1.635 ± 0.528, P = .999). WMS in the mismatch group was significantly improved (3.07 ± 0.48 vs 2.07 ± 1.14, P = .003); however, in recovery periods, WMS in the mismatch group was significantly higher than that in the normal group (1.05 ± 1.04, P < .01). ConclusionsIn successfully revascularized AMI, microvascular function is impaired despite preserved myocardial glucose metabolism in mismatch segments.

Abstract WP35: Penumbra Saved in Acute Stroke Patients Treated with IV Thrombolysis Predicts Minimal Infarct Growth Independent of Onset to Treatment

Purpose and Hypothesis: The ability to measure the immediate tissue effects in patients treated with thrombolysis ultra-early relative to their known onset has increased. We hypothesized that shorter onset to treatment times (OTT) would lead to more penumbra saved, calculated using multimodal MRI. Methods: Patients were included in this study if they met the following criteria: (1) were admitted between January 2010 and June 1, 2014 at one of two regional stroke centers, (2) had known last seen normal, acute MRI and IV tPA start times, (3) received an admit diagnosis of ischemic stroke, and (4) were treated with standard IV tPA. Penumbral volumes were calculated using the baseline MRI-defined mismatch regions minus the infarcted regions defined by the co-registered DWI at 24 hours. Patients were categorized to the “early” IV tPA cohort if their OTT was ≤ 120 minutes. Infarct growth was quantitatively defined as lesion volume increase &gt; 5 mL from baseline DWI to 5-day FLAIR. Favorable clinical outcome was defined as discharge or later mRS &lt; 2. Results: Sixty-three patients, 23 early- and 40 late-treated, were included in the study with mean age 75 (±15) years, 48% female, median [IQR]: admit NIHSS 10 [5-19], OTT 139 [109-185] minutes, baseline DWI volume 11.2mL [3.5-39.6], baseline MTT volume 120.9mL [37.8-220.7], and baseline mismatch volume 119.3mL [34.6-200.7]. Aside from time-based variables, only the amount of penumbra infarcted at 24 hours (p=0.015) was significantly different between the early- (9mL [1.7-19.7] and late-treated (2.4mL [0.7-7]) cohorts. The patients with favorable outcome were younger (p=0.012) with less severe admit NIHSS (p=0.026), smaller baseline DWI volume (p=0.017), smaller 24 hour DWI volume (p=0.041), and greater percentage of penumbra saved at 24 hours (p=0.010) but no difference in OTT (p=0.267). Using binomial logistic regression, percentage of penumbra saved at 24 hours (95%CI:0.000-0.011, p=0.010) was the only independent predictor of no infarct growth. Conclusions: This study establishes that significantly larger penumbral tissue saved at 24 hours, not early OTT, is predictive of both favorable clinical outcome and no infarct growth.

Effect of Lattice Mismatch on HgCdTe LPE Film Surface Morphology

A new type of crystal defect, which we call a rough structure, is reported in this work. The rough structure appears in large lattice mismatch regions whereas a normal surface appears in the regions where there is a small lattice mismatch on the same substrate. Experiments proved that under normal liquid-phase epitaxy growth conditions, the appearance of a rough structure is related to the lattice mismatch between the substrate and the film. Statistical data indicated that for Hg1−xCdxTe films with different Cd compositions x, a rough structure appeared on the film surface when the lattice mismatch was outside the range of 0.02–0.11%. The rough structure may result from the misfit dislocations resulting from strain relaxation. When there was a small surface crystal orientation deviation from (111), dense growth ripples appeared instead of the rough structure. A super-flat surface sometimes appeared inside the rough structure regions.

Arabidopsis ENDO2: Its Catalytic Role and Requirement of N-Glycosylation for Function

The Arabidopsis thaliana At1g68290 gene encoding an endonuclease was isolated and designated ENDO2, which was cloned into a binary vector to overexpress ENDO2 with a C-terminal 6 × His-tag in A. thaliana. Our Arabidopsis transgenic lines harboring 35SP::ENDO2 produced stable active enzyme with high yield. The protein was affinity purified from transgenic plants, and its identity was confirmed by liquid chromatography-mass spectrometry and automatic Edman degradation. ENDO2 enzyme digests RNA, ssDNA, and dsDNA, with a substrate preference for ssDNA and RNA. The activity toward ssDNA (361.7 U/mg) is greater than its dsDNase activity (14.1 U/mg) at neutral pH. ENDO2 effectively cleaves mismatch regions in heteroduplex DNA containing single base pair mismatches or insertion/deletion bases and can be applied to high-throughput detection of single base mutation. Our data also validated that the removal of sugar groups from ENDO2 strongly affects its enzymatic stability and activity.

Torque measurements reveal sequence-specific cooperative transitions in supercoiled DNA

B-DNA becomes unstable under superhelical stress and is able to adopt a wide range of alternative conformations including strand-separated DNA and Z-DNA. Localized sequence-dependent structural transitions are important for the regulation of biological processes such as DNA replication and transcription. To directly probe the effect of sequence on structural transitions driven by torque, we have measured the torsional response of a panel of DNA sequences using single molecule assays that employ nanosphere rotational probes to achieve high torque resolution. The responses of Z-forming d(pGpC)(n) sequences match our predictions based on a theoretical treatment of cooperative transitions in helical polymers. "Bubble" templates containing 50-100 bp mismatch regions show cooperative structural transitions similar to B-DNA, although less torque is required to disrupt strand-strand interactions. Our mechanical measurements, including direct characterization of the torsional rigidity of strand-separated DNA, establish a framework for quantitative predictions of the complex torsional response of arbitrary sequences in their biological context.

Pseudocontinuous arterial spin labeling quantifies relative cerebral blood flow in acute stroke.

The aim of this study was to test whether arterial spin labeling (ASL) can detect significant differences in relative cerebral blood flow (rCBF) in the core, mismatch, and reverse-mismatch regions, and whether rCBF values measured by ASL in those areas differ from values obtained using dynamic susceptibility contrast (DSC) MRI. Acute stroke patients were imaged with diffusion-weighted imaging (DWI) and perfusion-weighted imaging (ASL and DSC) MRI. An expert reader segmented the ischemic lesion on DWI and the DSC time-to-peak (TTP) maps. Three regions were defined: core (DWI+, TTP+), mismatch (DWI-, TTP+), and reverse-mismatch (DWI+, TTP-). For both ASL and DSC, rCBF maps were created with commercially available software, and the ratio was calculated as the mean signal intensity measured on the side of the lesion to that of the homologous region in the contralateral hemisphere. Values obtained from core, mismatch, and reverse-mismatch were used for paired comparison. Twenty-eight patients were included in the study. The mean age was 65.6 (16.9) years, with a median baseline National Institutes of Health Stroke Scale score of 10 (interquartile range, 4-17). Median time from last known normal to MRI was 5.7 hours (interquartile range, 2.9-22.6). Mean rCBF ratios were significantly higher in the mismatch 0.53 (0.23) versus the core 0.39 (0.33) and reverse-mismatch 0.68 (0.49) versus the core 0.38 (0.35). Differences in rCBF measured with DSC and ASL were not significant. ASL allows for the measurement of rCBF in the core and mismatch regions. Values in the mismatch were significantly higher than in the core, suggesting there is potential salvageable tissue.

Citicoline (Ceraxon) in acute stroke: assessment of clinical efficacy and effects on cerebral perfusion

Novel neuroimaging techniques provide quantitative assessment of cerebral perfusion in acute stroke and reveal the heterogeneity of ischemic zone. Neuroprotective agents play major role in the treatment of acute stroke as they are intended to restore functioning of potentially viable tissue. This prospective open-label study included 50 patients (mean age 60.9 years) with acute hemispheric stroke within the first 24 hours of symptoms onset. Patients were divided into 2 arms (25 patients in each arm) to receive standard of care (control arm) or standard of care plus citicoline (Ceraxon) 1 g b.i.d. as I.V. injection for 10 days. Clinical symptoms were assessed with NIHSS; neuroimaging included DWI to confirm ischemic lesion and perfusion CT to assess cerebral perfusion. Patients in both arms demonstrated significant clinical improvement on Day 10 with no significant difference between treatment arms (mean NIHSS score was 9.4 in control arm and 8.4 in Ceraxon arm, p=0.87). Perfusion CT on admission showed perfusion deficit in all patients. Mismatch regions on perfusion CT compared to DWI indicating potentially viable tissue (“penumbra”) were found in 75% of patients in control arm and in 69% of patients in Ceraxon arm. No difference between perfusion parameters in the “core” vs. “penumbra” on initial imaging was shown. On Day 10 there were no changes of cerebral perfusion values in the “core” regions, while in “penumbra” in Ceraxon arm CBF increased significantly CBF (p=0.013) with no significant differences vs. intact hemisphere, that is consistent with cerebral perfusion improvement. Thus, treatment with Ceraxon in the first 10 days of acute stroke may result in improvement of cerebral perfusion in the potentially viable tissue.

Relationship between sodium intensity and perfusion deficits in acute ischemic stroke

To assess the relationship between sodium signal intensity changes and oligemia, measured with perfusion-weighted imaging (PWI), in ischemic stroke patients. Nine ischemic stroke patients (55 ± 13 years), four with follow-up scans, underwent sodium and proton imaging 4-32 hours after symptom onset. Relative sodium intensity was calculated as the ratio of signal intensities in core (identified as hypertintense lesions on diffusion-weighted imaging [DWI]) or putative penumbra (PWI-DWI mismatch) to contralateral homologous regions. Sodium intensity increases in the core were not correlated with the severity of hypoperfusion, measured with either cerebral blood flow (rho = 0.157; P = 0.61) or cerebral blood volume (rho = -0.234; P = 0.44). In contrast, relative sodium intensity was not elevated (4-7 hours 0.96 ± 0.07; 17-32 hours 1.00 ± 0.07) in PWI-DWI mismatch regions. Sodium signal intensity cannot be predicted by the degree of hypoperfusion acutely. Sodium intensity also remains unchanged in PWI-DWI mismatch tissue, indicating preservation of ionic homeostasis. Sodium magnetic resonance imaging (MRI), in conjunction with PWI and DWI, may permit identification of patients with viable tissue, despite an unknown symptom onset time.

Characteristics of Patients with Target Magnetic Resonance Mismatch Profile: Data from Two Geographically and Racially Distinct Populations

Background: Recently, the Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution (DEFUSE) and the Echoplanar Imaging Thrombolytic Evaluation Trial (EPITHET) trialists suggested that diffusion-perfusion magnetic resonance imaging (MRI) can classify patients into 4 subgroups likely to differentially experience benefit or harm from reperfusion therapies. However, there is a lack of data comparing MR mismatch profiles between different race-ethnic groups. In addition, clinical factors affecting MR mismatch profiles are not well described. Methods: We analyzed clinical and pretreatment MRI data of patients from 2 geographically and ethnically distinct study populations (Seoul, South Korea, and Los Angeles, Calif., USA) who are eligible for recanalization therapy. Diffusion-perfusion mismatch regions were classified among the 4 DEFUSE MR profiles: target mismatch, no mismatch, small lesion and malignant. Results: A total of 147 South Korean and 162 Southern Californian subjects (64.2% Whites) were included. Pretreatment MRIs revealed that the MR mismatch profiles were different in the 2 study populations (p < 0.001). Target mismatch was more prevalent in Southern Californian subjects (67.9%) compared with South Korean subjects (58.5%), whereas the small lesion pattern was more prevalent in the latter (9.9 vs. 23.1%). After adjusting for covariables, 3 features independently decreased the likelihood of presence of target mismatch: history of diabetes (OR 0.369, 95% CI 0.196–0.694), small versus large arterial occlusion (OR 0.052, 95% CI 0.01–0.255) and largest size (highest tertile) of diffusion-weighted imaging (DWI) lesion volume (OR 0.516, 95% CI 0.266–0.999). The one feature independently increasing target mismatch likelihood was intermediate size (middle tertile) DWI volume (OR 2.977, 95% CI 1.431–6.195). Conclusions: Target mismatch profiles are present in 55–70% of patients. Target mismatch is less common in patients with diabetes, small vessel occlusion, Asian ethnicity and extensive DWI lesions, and more common in patients with DWI lesions of intermediate size.

Impact of collateral flow on tissue fate in acute ischaemic stroke

Background:Collaterals may sustain penumbra prior to recanalisation yet the influence of baseline collateral flow on infarct growth following endovascular therapy remains unknown.Methods:Consecutive patients underwent serial diffusion and perfusion MRI before...

Complete chaotic synchronization characteristics of the linear-polarization mode of vertical-cavity surface-emitting semiconductor lasers with isotropic optical feedback

Based on the SFM model [M. San Miguel, Q. Feng, J.V. Moloney, Phys. Rev. A. 52 (1995) 1728.], complete chaotic synchronization characteristics of linear-polarization (LP) Mode of the vertical-cavity surface-emitting semiconductor lasers (VCSELs) with isotropic optical feedback are numerically investigated. When the propagation time τc of light from the transmitter to the receiver equals to the external cavity round-trip time τ, and the central frequency of the T_VCSEL matches that of the R_VCSEL, in large scale region of the feedback coefficient and the injection current where the x-polarization mode as well as the y-polarization mode obtains high synchronization quality at the same time. However, in the central frequency mismatch regions where the x- and y-polarization mode can obtain inferior synchronization quality at same time. But for τc≠τ, each LP mode of the mixed polarization modes achieved inferior synchronization quality at the same time. Besides, with big enough injection current, the output of the system with the same central frequency in two lasers is entirely governed by the y-polarization mode when the feedback coefficient and Δτ(=τc−τ) fixed at a certain value. So the system can realize steadily good synchronization of the completely dominant y-polarization mode. But the synchronization quality of the completely dominated y-polarization mode can be deteriorated by increasing absolute frequency detuning value. Besides, in positive frequency mismatch regions where the influence of the same frequency detuning value on the synchronization quality of the entirely governed y-polarization mode becomes smaller than in negative frequency detuning regions. At last, when τ is given and the central frequency of the T_VCSEL matches that of the R_VCSEL, the influence of the τc is not a simple time-shift in the time-evolution of the receiver VCSEL, which has serious influence on the complete synchronization quality of each LP mode.

Dynamics of volume transmission in the brain. Focus on catecholamine and opioid peptide communication and the role of uncoupling protein 2

This review focuses on transmitter-receptor mismatches in the brain, which is one of the hallmarks of the Volume Transmission (VT) concept, and how this phenomenon may be related to local temperature gradients created by brain uncoupling protein 2 (UCP2), which uncouples oxidative phosphorylation from ATP synthesis, hereby generating heat. Recent studies on transmitter-receptor mismatches have revealed dopamine and opioid peptide receptor mismatches in the intercalated islands of the amygdala, which are GABAergic cell clusters regulating amygdaloid output. Such mismatches have also been found in regions belonging to the extended amygdala and the nucleus accumbens shell. Now substantial UCP2 immunoreactivity has been found within the above transmitter-receptor mismatch regions, suggesting that UCP2 may enhance diffusion and convection of DA and opioid peptides in such regions by generation of local temperature gradients, thereby contributing to a dynamic regulation of VT.