[The multicenter study on the registration and follow-up of low anticoagulation therapy for the heart valve operation in China]

OBJECTIVE

To investigate the optimal anticoagulation methods and monitoring strategy for Chinese patients undergoing heart valve replacement, which is potentially quite different from western populations.

METHODS

In this multicenter prospective cohort study, the anticoagulation and monitoring strategy data was acquired from 25 773 in-hospital patients in 35 medical centers and 20 519 patients in outpatient clinic in 11 medical centers from January 1st, 2011 to December 31th, 2015.

RESULTS

As for in-hospital patients, mean age of study population was (48.6±11.2) years old; main etiology of valve pathology was rheumatic (87.5%) origin among study cohort; 94.8% of study population received mechanical valve implantation; international normalized ratio (INR) monitoring (in all the study centers) and low-intensity anticoagulation strategy (31 hospitals chose target INR range of 1.5-2.5, and actual values of INR among 89.2% of 100 069 in-hospital monitoring samples were 1.5-2.5), with mean actual INR values of 1.84±0.53, and warfarin dosage of (2.82±0.93) mg/d were widely adopted among the study centers; strategies of in-hospital warfarin administration were similar in all the study centers; complication rates of low-intensity anticoagulation strategy were low in severe hemorrhage (0.02%), thrombosis (0.05%), and thromboembolism (0.05%) events, without anticoagulation-related death.As for 18 974 outpatient clinic patients, the follow-up rate was 92.47%, with a total of 30 012 patient-years (Pty). Anticoagulation-related morbidity and mortality rates were 0.67% and 0.15% Pty; major hemorrhage morbidity and mortality rates were 0.25% and 0.13% Pty; thromboembolism morbidity and mortality rates were 0.45% and 0.03% Pty.The mean dosage of warfarin daily dosage was (2.85±1.23) mg/d and INR value was 1.82±0.57.No significant regional difference in the intensity of anticoagulation therapy was noted during the study.

CONCLUSIONS

INR can be used as a normalized indicator for intensity of anticoagulation therapy in China.The optimal anticoagulation intensity with INR range from 1.5 to 2.5 is safe and effective for Chinese patients with heart valve replacement, and there is no significant regional difference in the intensity of anticoagulation therapy.

Abstract WMP97: Regional Cerebral Oxygen Extraction is Elevated in Tissue at High Risk of Stroke in Pediatric Sickle Cell Disease

Introduction: Children with sickle cell disease (SCD) are at high risk of stroke. Hemispheric oxygen extraction fraction (OEF) is a predictor of stroke in adults with carotid occlusion, but OEF has not been evaluated as a predictor of stroke in children with SCD.

Hypothesis: OEF is elevated in SCD children compared to controls within a region at high risk of stroke as defined by an infarct heat-map created from a separate retrospective SCD cohort.

Methods: A prospective MRI study enrolled 37 children aged 5-21: 17 with SCD and no stroke, 12 with SCD and silent infarcts (median infarct volume=0.3ml), and 8 sibling controls. None were on transfusions or had overt stroke history. Voxel-wise OEF was measured using an asymmetric spin echo sequence. In a separate retrospective cohort of 67 SCD children with overt and silent stroke, infarct regions on FLAIR were manually outlined and coregistered to an average T1 map to create an infarct heat-map (Fig A) which was used to define a “high risk” ROI (defined by >3% infarct density). This ROI was aligned to individual OEF maps from the prospective cohort (Fig B, average OEF map). OEF within the “high risk” ROI was compared between SCD children and controls; and between SCD children with and without infarction using Mann Whitney U tests.

Results: The infarct heat-map from the retrospective cohort (Fig A) and the average OEF map from the prospective SCD cohort (Fig B) demonstrate striking co-localization of infarct density and elevated OEF. Within the “high risk” ROI, OEF was higher in SCD children compared to controls (39% [36, 46] vs. 23% [22, 27], p<0.0001 (Fig C). OEF within this “high risk” ROI did not differ between SCD children with and without infarcts (40% [38, 47] vs. 38% [35, 46], p=0.6).

Conclusion: OEF in SCD children is elevated in the internal borderzone, a region with high stroke risk in SCD. Regional OEF may be a marker of cerebral metabolic stress that could be exploited to stratify stroke risk in this vulnerable population.

Abstract 35: Transfusion Relieves Cerebral Metabolic Stress in Children with Sickle Cell Disease

Introduction: Transfusions (Tx) are the mainstay of stroke prevention in children with sickle cell disease (SCD), but the pathophysiology conferring this neuroprotection is not well understood.

Hypothesis: Tx relieves cerebral metabolic stress by improving arterial oxygen content, thereby lowering chronically-elevated cerebral blood flow (CBF) and oxygen extraction fraction (OEF) in children with SCD at risk for stroke.

Methods: Children with SCD on chronic Tx therapy underwent two brain MRIs with measurement of CBF via pseudocontinuuous arterial spin labeling and OEF via asymmetric spin echo sequence within 24 hours of exchange Tx. To determine how Tx may reduce regions of elevated OEF, we set absolute OEF thresholds (45, 47.5, 50%) and compared tissue volumes above each threshold pre- and post-Tx using nonparametric paired statistics.

Results: Twelve children with SCD (6-21 yrs) underwent MRIs. Tx raised Hb and lowered CBF and OEF (Figure), suggesting that elevated CBF and OEF may be markers of metabolic stress relieved by Tx. While CBF correlates with age in healthy children, pre-Tx CBF correlation with age was lost (τ= -0.42, p=0.07), but regained post-Tx (τ= -0.76, p=0.001). Also, absolute change in OEF diminished with increasing age (τ=. -0.75, p=0.003). Regions with very high OEF were found in the periventricular white matter, a common area of infarcts in SCD (Figure, average OEF maps pre- and post-Tx). Tx reduced the volume of these brain regions defined by all three OEF thresholds (Table), suggesting that Tx reduces brain regions at high risk for stroke.

Conclusion: Tx in SCD children improves arterial oxygen content by increasing Hb, allowing CBF and OEF to fall, thus relieving metabolic stress globally and regionally. The absolute change in OEF correlates with age, suggesting that the efficacy of Tx may be age-dependent.

Abstract T P297: Arterial Spin Labeled MRI Quantifies Cerebral Blood Flow Changes with Blood Pressure from Acute to Subacute Stroke

Background: Hemodynamic interventions, such as blood pressure (BP) manipulation, are often utilized to optimize perfusion of the ischemic territory. Scant data support theoretical effects of permissive hypertension or BP reduction, yet arterial-spin labeled (ASL) MRI may chronicle quantitative cerebral blood flow (CBF) changes. We used serial ASL to measure CBF changes associated with hemodynamic interventions, based on arterial occlusion site and collaterals.

Methods: Serial ASL acquired in 148 consecutive cases of acute ischemic stroke at a single center during a 3-year period. A pseudo-continuous ASL pulse sequence with background suppressed 3D GRASE (gradient and spin echo) readout with 4 post-labeling delays was used, with normalization of quantitative CBF on a standard neurovascular template. CBF values and relative changes were measured in the affected hemisphere and in discrete regions of infarct core and collateral territories.

Results: 148 cases (median age 68 years (IQR 62-82), 73 women) were studied. Overall, CBF (ml/100g/min) was related to age (r=-0.40, p<0.001) but not gender (male: 39±9.7, female: 40.6±8.2; r=.05, p=NS). Serial studies were obtained in 126 cases, including 2 studies in 91, 3 in 32, and 4 in 3. Median time to 1 st , 2 nd , 3 rd , and 4 th ASL study was 11.3, 39.7, 140.7, and 121.3 hrs and median CBF at these timepoints was 39.9 (IQR 28-48); 42.2 (IQR 29-52); 47.1 (IQR 36-56); and 35.6 (IQR 34-41). Average changes in CBF from study 1 to 2, 2 to 3, 3 to 4 were +2.2; +3.4; -14.8. Average CBF ratio between leptomeningeal and perforating MCA regions was 1.1. The correlation of initial delta CBF (study 1 to 2) with initial delta BP (1 to 2) was r=-0.1, p=NS. Average delta CBF/delta mmHg SBP was 0.25. At studies 1 and 2, lower BP was related to higher CBF (r=-0.148, p=0.102). Overall, delta BP was not linked with CBF (r=0.002, p=NS) or delta CBF (r=-0.108, p=NS). For those with low initial CBF (<40), positive delta BP was strongly associated with lower CBF at study 2 (r=-0.552, p=0.006).

Conclusions: Blood pressure modification, permissive or interventional, may differentially affect CBF in the ischemic core and collateral regions. ASL provides a novel method for non-invasive mapping of serial changes in absolute CBF quantification in the ICU and beyond.

Mutational analysis of podocyte genes in children with sporadic steroid-resistant nephrotic syndrome

Recent studies have demonstrated that mutations in 4 podocyte genes, NPHS1, NPHS2, CD2AP, and WT1, are associated with the pathogenesis of steroid-resistant nephrotic syndrome (SRNS). Systematic investigation of all 4 genes for sporadic SRNS in China has not been performed. We examined 10 Chinese children with sporadic SRNS who showed no response to immunosuppressive agents and 20 SRNS controls who exhibited a response to prolonged steroid or immunosuppressive treatment and achieved complete remission. We analyzed mutations in the 4 podocyte genes, NPHS1, NPHS2, CD2AP, and WT1. Mutational analysis was performed using polymerase chain reaction and direct sequencing. Of the 10 SRNS children who showed no response to immunosuppressive agents, the compound heterozygous NPHS1 mutations 2677A>G (T893A) and *142T>C were identified in 1 patient, while a heterozygous mutation in WT1, 1180C>T (R394W), was found in another patient. Of the 20 SRNS children showing complete remission who responded to prolonged steroid therapy or immunosuppressive agents, 4 heterozygous NPHS1 mutations, 928G>A, IVS8+30C>T, IVS21+14G>A, and IVS25-23C>T, were identified in 4 patients and a heterozygous CD2AP mutation, IVS7-135G>A, was identified in 1 patient. Our results indicate the necessity of genetic examination for mutations in podocyte genes in Chinese SRNS children who show no response to immunosuppressive agents.

Highly efficient beamline and spectrometer for inelastic soft X-ray scattering at high resolution

The design, construction and commissioning of a beamline and spectrometer for inelastic soft X-ray scattering at high resolution in a highly efficient system are presented. Based on the energy-compensation principle of grating dispersion, the design of the monochromator-spectrometer system greatly enhances the efficiency of measurement of inelastic soft X-rays scattering. Comprising two bendable gratings, the set-up effectively diminishes the defocus and coma aberrations. At commissioning, this system showed results of spin-flip, d-d and charge-transfer excitations of NiO. These results are consistent with published results but exhibit improved spectral resolution and increased efficiency of measurement. The best energy resolution of the set-up in terms of full width at half-maximum is 108 meV at an incident photon energy tuned about the Ni L3-edge.

Voxelwise spectral diffusional connectivity and its applications to Alzheimer's disease and intelligence prediction

Human brain connectivity can be studied using graph theory. Many connectivity studies parcellate the brain into regions and count fibres extracted between them. The resulting network analyses require validation of the tractography, as well as region and parameter selection. Here we investigate whole brain connectivity from a different perspective. We propose a mathematical formulation based on studying the eigenvalues of the Laplacian matrix of the diffusion tensor field at the voxel level. This voxelwise matrix has over a million parameters, but we derive the Kirchhoff complexity and eigen-spectrum through elegant mathematical theorems, without heavy computation. We use these novel measures to accurately estimate the voxelwise connectivity in multiple biomedical applications such as Alzheimer's disease and intelligence prediction.

Abstract T P29: Arterial-Spin Labeled MRI After Endovascular Stroke Therapy: Validation of a Novel Scale to Quantify the Degree and Heterogeneity of Reperfusion

Background: The degree of reperfusion in acute stroke is a key predictor of clinical outcome, yet validation of a noninvasive imaging technique such as arterial spin-labeled MRI (ASL) that can quantify both hypo- and hyperperfusion is needed.

Methods: Consecutive series of endovascular therapy for acute stroke and ASL-MRI within 36 hours after treatment start during a 3-year period were analyzed. Reperfusion on DSA was scored with TICI and mTICI (2b definitions of 2/3 and ½, respectively). ASL cerebral blood flow was graded with a scale analogous to mTICI (0=none, 1=< ½, 2=>½, 3=complete) separately for hypo- and hyperperfusion based on occlusion site, yet blinded to TICI/mTICI results.

Results: 64 patients (mean age 67.7 ± 13.9 years; 53% women; median baseline NIHSS 15 (2-38)) had ASL acquired within 36 hours (median 7.07 hours (2.69-33.08)) from start of IV thrombolysis or thrombectomy over a 3-year period. 31/64 (48%) patients received IV tPA before endovascular therapy. DSA revealed 32 M1, 18 ICA, 10 M2, and 4 basilar occlusions. After endovascular treatment, TICI0/mTICI0 (6%), TICI1/mTICI1 (2%), TICI2a/mTICI2a (30%), TICI2a/mTICI2b (22%), TICI2b/mTICI2b (39%) and TICI3/mTICI3 (2%) results were noted. ASL revealed hypoperfusion (0 (19%); 1 (59%); 2 (14%); 3 (8%)) and hyperperfusion (0 (69%); 1 (27%); 3 (5%)). 7 combined patterns of hypo- and hyperperfusion were noted on ASL, all unrelated to baseline clinical variables. ASL mTICI hypoperfusion strongly correlated with DSA mTICI (R=-0.77, p<0.001) and TICI (R=-0.71, p<0.001). ASL hyperperfusion was noted only with TICI2a/mTICI2a (9%), TICI2a/mTICI2b (14%), TICI2b/mTICI2b (9%) and was more common with increased time from DSA to ASL (p=0.017).

Conclusions: ASL hypoperfusion within 36 hours of acute stroke therapy strongly correlates with reperfusion scores on DSA, providing a novel means to accurately quantify degree of reperfusion. ASL hyperperfusion, concomitant with hypoperfusion, affects a substantial number of cases, predominantly affecting the TICI2a/mTICI2b reperfusion category on DSA.

Association study of vascular endothelial growth factor gene polymorphisms with ectopic pregnancy in Chinese women

OBJECTIVE

The purpose of this study is to evaluate potential associations between vascular endothelial growth factor (VEGF) gene polymorphisms and ectopic pregnancy (EP) in Chinese women.

MATERIALS AND METHODS

This was a case-control study wherein 192 women with a history of EP were compared to 210 post-menopausal controls with two pregnancies and no EP for the genotyping of VEGF polymorphisms. Genotyping of the VEGF gene polymorphisms at -460C/T, -1 154G/A, -2578C/A and +936C/T were performed by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS

No significant differences were found in genotype and allele distributions of the -460C/T, +936C/T polymorphisms between cases and controls. Compared with the -1154G/G genotype, the -1154(A/A+G/A) genotype could significantly reduce the risk of developing EP. For the -2578C/A polymorphism, the A/A+C/A geno- type could significantly decrease the risk of developing EP, compared with the C/C genotype. The haplotype analysis suggested that the TAA (VEGF -460/-1154/-2578) and CAA haplotypes could significantly decrease the risk of developing EP compared with the haplotype of TGC.

CONCLUSION

The -1154A or -2578A alleles of VEGF gene could significantly decrease the risk of EP and might be po- tentially protective factors for EP development in Chinese women.

Measurement of cerebral white matter perfusion using pseudocontinuous arterial spin labeling 3T magnetic resonance imaging--an experimental and theoretical investigation of feasibility

PURPOSE

This study was aimed to experimentally and numerically investigate the feasibility of measuring cerebral white matter perfusion using pseudocontinuous arterial spin labeling (PCASL) 3T magnetic resonance imaging (MRI) at a relatively fine resolution to mitigate partial volume effect from gray matter.

MATERIALS AND METHODS

The Institutional Research Ethics Committee approved this study. On a clinical 3T MR system, ten healthy volunteers (5 females, 5 males, age = 28 ± 3 years) were scanned after providing written informed consent. PCASL imaging was performed with varied combinations of labeling duration (τ = 1000, 1500, 2000, and 2500 ms) and post-labeling delay (PLD = 1000, 1400, 1800, and 2200 ms), at a spatial resolution (1.56 x 1.56 x 5 mm(3)) finer than commonly used (3.5 x 3.5 mm(2), 5-8 mm in thickness). Computer simulations were performed to calculate the achievable perfusion-weighted signal-to-noise ratio at varied τ, PLD, and transit delay.

RESULTS

Based on experimental and numerical data, the optimal τ and PLD were found to be 2000 ms and 1500-1800 ms, respectively, yielding adequate SNR (~2) to support perfusion measurement in the majority (~60%) of white matter. The measurement variability was about 9% in a one-week interval. The measured white matter perfusion and perfusion ratio of gray matter to white matter were 15.8-27.5 ml/100ml/min and 1.8-4.0, respectively, depending on spatial resolution as well as the amount of deep white matter included.

CONCLUSION

PCASL 3T MRI is able to measure perfusion in the majority of cerebral white matter at an adequate signal-to-noise ratio by using appropriate tagging duration and post-labeling delay. Although pixel-wise comparison may not be possible, region-of-interest based flow quantification is feasible.

GABA estimation in the brains of children on the autism spectrum: measurement precision and regional cortical variation

(1)H magnetic resonance spectroscopy ((1)H MRS) and spectral editing methods, such as MEGA-PRESS, allow researchers to investigate metabolite and neurotransmitter concentrations in-vivo. Here we address the utilization of (1)H MRS for the investigation of GABA concentrations in the ASD brain, in three locations; motor, visual and auditory areas. An initial repeatability study (5 subjects, 5 repeated measures separated by ~5days on average) indicated no significant effect of reference metabolite choice on GABA quantitation (p>0.6). Coefficients of variation for GABA+/NAA, GABA+/Cr and GABA+/Glx were all of the order of 9-11%. Based on these findings, we investigated creatine-normalized GABA+ ratios (GABA+/Cr) in a group of (N=17) children with autism spectrum disorder (ASD) and (N=17) typically developing children (TD) for Motor, Auditory and Visual regions of interest (ROIs). Linear regression analysis of gray matter (GM) volume changes (known to occur with development) revealed a significant decrease of GM volume with Age for Motor (F(1,30)=17.92; p<0.001) and Visual F(1,16)=14.41; p<0.005 but not the Auditory ROI (p=0.55). Inspection of GABA+/Cr changes with Age revealed a marginally significant change for the Motor ROI only (F(1,30)=4.11; p=0.054). Subsequent analyses were thus conducted for each ROI separately using Age and GM volume as covariates. No group differences in GABA+/Cr were observed for the Visual ROI between TD vs. ASD children. However, the Motor and Auditory ROI showed significantly reduced GABA+/Cr in ASD (Motor p<0.05; Auditory p<0.01). The mean deficiency in GABA+/Cr from the Motor ROI was approximately 11% and Auditory ROI was approximately 22%. Our novel findings support the model of regional differences in GABA+/Cr in the ASD brain, primarily in Auditory and to a lesser extent Motor but not Visual areas.

Abstract WP41: Peri-Procedural Arterial Spin Labeling and Dynamic Susceptibility contrast Perfusion in Detection of Cerebral Blood Flow in Patients with Acute Ischemic Syndrome

Purpose: To investigate the potential clinical value and diagnostic performance of arterial spin-labeled (ASL) and dynamic susceptibility contrast (DSC) perfusion in detection of cerebral blood flow (CBF) changes before and after endovascular recanalization in patients with acute ischemic syndrome (AIS).

Methods: This retrospective study was performed using MR examinations between 2010-2012. Inclusion criteria were: patients with AIS who underwent endovascular recanalization and acquisition of both ASL and DSC before and after revascularization. ASL CBF and multiparametric DSC perfusion maps were qualitatively evaluated for image quality, presence of hypo or hyperperfusion and location of perfusion abnormality. Lesion segmentation for infarct core (ADCb >550) and hypoperfused area (TMax > 4 sec) was performed on DSC. rCBF was calculated using a regions-of-interest (ROI) method in the infarction core and hypoperfused areas using coregistered ASL and DSC images. Core and hypoperfused rCBF ROI’s were used for paired pre- and post-treatment intermodality comparisons. Interobserver and intermodality agreement was evaluated by Kappa test. T-test and Spearman correlation coefficients were calculated for ASL and DSC rCBF values.

Results: Twenty-five patients were met our inclusion criteria. Five studies were rated non-diagnostic, resulting in a total of 45 pair of DSC-ASL for comparison. ASL and DSC agreed on type of perfusion abnormality in 32 of 45 cases (71%) and location of the perfusion abnormality in 36 of 45 cases (80%). The image quality of ASL was lower than DSC, resulting in interobserver variability for the type (k =0.45) and location (k=0.56) of perfusion abnormality. ASL was unable to show any type of perfusion abnormality in 11% of patients. In patients with successful recanalization, hyperperfusion (rCBF> 1) was detected in 100% on DSC and 47% on ASL. ASL showed prolonged arterial transit effects in 58% of successfully recanalized patients.

Conclusion: ASL is moderately consistent with DSC for detection of cerebral blood flow changes in patients with AIS. Qualitative and quantitative differences exist between two modalities, in particular in respect to detection of hyperperfusion in successfully recanalized patients.

Abstract TP41: Arterial Spin-Labeled Perfusion MRI with Multi-Delay: Expanding Beyond CBF in Acute Ischemic Stroke

Background: Arterial spin-labeled (ASL) perfusion MRI can measure cerebral blood flow (CBF), yet the prolonged delays of collateral perfusion in acute ischemic stroke may impose limitations. Multiparametric maps of perfusion, including transit times and cerebral blood volume (CBV), may reveal important hemodynamic features before CBF collapse. We implemented a novel multi-delay ASL sequence to investigate multiparametric perfusion changes in acute stroke.

Methods: Consecutive acute ischemic stroke patients admitted during an 8-month period were evaluated with pseudo-continuous ASL on Siemens 1.5 T and 3 T scanners within 12 hours of symptom onset. ASL was acquired using a 4-delay pCASL protocol with background suppressed 3D GRASE (postlabeling delay (PLD)=1.5/2/2.5/3s, FOV=22cm, matrix=64x64, 16x8mm slices, rate-2 GRAPPA, TE=22ms, 8 pairs of tag and control for each delay, total scan time 4min). After motion correction, arterial transit time (ATT), CBF, and arterial CBV (aCBV) maps were generated from the 4 PLDs.

Results: A total of 161 ASL multi-delay perfusion MRI studies were performed in 130 acute ischemic stroke patients (mean age was 71±18 years and 56% were female). Repeated multi-delay ASL or serial studies were acquired in 19 cases, including 11 cases with 2 MRIs, 7 with 3, and 1 with 6 MRIs, depicting multiparametric blood flow changes after treatment. Correlation of multi-delay ASL (4 PLDs) and DSC MRI CBF asymmetry measures in MCA stroke patients (when available) was r=0.785 (p<0.001) and r=0.683 (p=0.003) for CBV measures with limited correlation for ATT.

Conclusions: Multidelay ASL with 4 PLDs is feasible in the setting of acute stroke, providing multiparametric perfusion measures (CBF, CBV, ATT) of blood flow changes with treatment.

Abstract 1905: Arterial Spin-Labeled MRI of Leptomeningeal Collateral Perfusion in Acute Ischemic Stroke

Background: Leptomeningeal collaterals and associated cortical perfusion downstream from a proximal arterial occlusion or stenosis are potent predictors of outcome in acute stroke. Arterial spin-labeled (ASL) MRI may depict delayed arterial transit effects (DATE) of these collaterals and cerebral blood flow (CBF), utilizing noninvasive techniques without the use of contrast. We conducted a prospective validation study of ASL DATE and CBF as biomarkers of leptomeningeal collateral perfusion compared to digital subtraction angiography (DSA) and dynamic susceptibility contrast (DSC) perfusion MRI in acute ischemic stroke.

Methods: Consecutive anterior circulation acute ischemic stroke patients admitted during a 1-year period were evaluated with pseudo-continuous ASL, DSA and DSC perfusion MRI within 12 hours of symptom onset. ASL DATE extent was scored using a 3-point scale and angiographic collaterals on the DSA graded using the ASITN/SIR collateral score. ASL CBF and DSC CBF maps were co-registered to derive comparative ROI statistics on perfusion in the symptomatic territory. ASL CBF lesions < 15 mL/100 g/min were used to measure DSC CBF values within coregistered ROIs.

Results: Among 39 patients meeting entry criteria, mean age was 66±19 years and 51% were male. All 39 patients were imaged with ASL and DSA, with DSC perfusion MRI in a subset of 27. Sites of vascular occlusion or stenosis were: terminal ICA - 10, M1 MCA - 20, M2 MCA - 5 and more distal MCA - 4. ASL DATE scores ranged from 0-2, with a median of 1. DSA collateral grade ranged from 0-4, with a median of 2. Overall, there was strong correlation (r=0.702, p<0.001) between the ASL and DSA measures of leptomeningeal collateral supply. In the downstream territory from these leptomeningeal collaterals, ASL CBF and DSC CBF maps both revealed hypoperfusion in regions that closely matched. Only limited correlation, however, was noted between exact ASL CBF and DSC CBF values within the co-registered ROIs.

Conclusions: ASL MRI provides an accurate, noninvasive measure of leptomeningeal collateral perfusion in acute ischemic stroke due to anterior circulation stenosis or occlusion. ASL CBF measures of collateral perfusion likely are arterially weighted, like DSA collateral grades, and unlike conventional DSC perfusion MRI CBF values.

Abstract 1910: Hyperperfusion in Acute Ischemic Stroke: Serial Arterial Spin-Labeled MRI of Reperfusion and Hemorrhagic Transformation

Background: Arterial spin-labeled (ASL) MRI facilitates repeated noninvasive evaluation of cerebral blood flow without the use of contrast. Hyperperfusion may be readily detected with ASL and serial imaging may therefore chronicle the dynamics of territorial perfusion from acute to chronic phases after stroke. We characterized hyperperfusion on ASL in a prospective series of acute ischemic stroke patients, describing the clinical correlates, time course and association with reperfusion hemorrhage.

Methods: A consecutive series of acute ischemic stroke patients admitted during a 1-year period were evaluated with pseudo-continuous ASL with background suppressed 3D GRASE (delay=2s, matrix=64x64; 26 slices, resolution 3.4x3.4x5mm, scan time 4min). Post-processed ASL CBF maps were visually inspected for detection of hyperperfusion. DSA measures of collaterals and reperfusion were scored when available and hemorrhagic transformation (HT) was graded on GRE in all 198 cases. Univariate and multivariate statistical analyses delineated clinical correlates, timing and other imaging features of hyperperfusion.

Results: Among 198 patients, mean age was 69.4±15.7 years and 48.5% were women. Among 77 with serial ASL MRI, interval from initial to follow-up MRI was median 25.0 (IQR 10.3-53.9) hours. Hyperperfusion was detected in 15/198 (7.6%) patients at baseline and 30/77 (39.0%) at follow-up. Trajectories included 7/77 (9.1%) with hyperperfusion at both baseline and follow-up and 38/77 (49.4%) showing hyperperfusion at any timepoint during admission. Hyperperfusion correlated with achievement of reperfusion among patients undergoing endovascular therapy (OR 6.5, 95% CI 1.82-23.25, p=0.018) and history of atrial fibrillation (OR 4.4, 95% CI 1.9-10.6, p<0.001). Analysis of the 42 cases with DSA revealed that hyperperfusion was most common in patients with poor collateral grade followed by more complete TICI reperfusion scores. Overall, HT affected 57/198 (28.8%), including 35/198 (17.7%) HI1, 11/198 (5.6%) HI2, 8/198 (4.1%) PH1 and 3/198 (1.5%) PH2. Multivariate analyses revealed that hyperperfusion at any timepoint was a potent predictor of HT (OR 52.6, 95%CI 12.4-222.6, p<0.001).

Conclusions: Hyperperfusion in acute ischemic stroke is frequently demonstrated by ASL MRI, providing novel insight on the dynamics of reperfusion and HT. Hyperperfusion increases the risk of HT 50-fold, likely due to autoregulatory loss. Poor collaterals and sudden reperfusion in vulnerable cases such as those with atrial fibrillation may herald hyperperfusion and HT.

Baseline CBF, and BOLD, CBF, and CMRO2 fMRI of visual and vibrotactile stimulations in baboons

Neurovascular coupling associated with visual and vibrotactile stimulations in baboons anesthetized sequentially with isoflurane and ketamine was evaluated using multimodal functional magnetic resonance imaging (fMRI) on a clinical 3-Tesla scanner. Basal cerebral blood flow (CBF), and combined blood-oxygenation-level-dependent (BOLD) and CBF fMRI of visual and somatosensory stimulations were measured using pseudo-continuous arterial spin labeling. Changes in stimulus-evoked cerebral metabolic rate of oxygen (CMRO(2)) were estimated using calibrated fMRI. Arterial transit time for vessel, gray matter (GM), and white matter (WM) were 250, 570, and 823 ms, respectively. Gray matter and WM CBF, respectively, were 107.8±7.9 and 47.8±3.8 mL per 100 g per minute under isoflurane, and 108.8±10.3 and 48.7±4.2 mL per 100 g per minute under ketamine (mean±s.e.m., N=8 sessions, five baboons). The GM/WM CBF ratio was not statistically different between the two anesthetics, averaging 2.3±0.1. Hypercapnia evoked global BOLD and CBF increases. Blood-oxygenation-level-dependent, CBF, and CMRO(2) signal changes by visual and vibrotactile stimulations were 0.19% to 0.22%, 18% to 23%, and 4.9% to 6.7%, respectively. The CBF/CMRO(2) ratio was 2.9 to 4.7. Basal CBF and fMRI responses were not statistically different between the two anesthetics. This study establishes a multimodal fMRI protocol to probe clinically relevant functional, physiological and metabolic information in large nonhuman primates.

Relating MEG measured motor cortical oscillations to resting γ-aminobutyric acid (GABA) concentration

The human motor cortex exhibits characteristic beta (15-30 Hz) and gamma oscillations (60-90 Hz), typically observed in the context of transient finger movement tasks. The functional significance of these oscillations, such as post-movement beta rebound (PMBR) and movement-related gamma synchrony (MRGS) remains unclear. Considerable animal and human non-invasive studies, however, suggest that the networks supporting these motor cortex oscillations depend critically on the inhibitory neurotransmitter γ-Aminobutyric acid (GABA). Despite such speculation, a direct relation between MEG measured motor cortex oscillatory power and frequency with resting GABA concentrations has not been demonstrated. In the present study, motor cortical responses were measured from 9 healthy adults while they performed a cued button-press task using their right index finger. In each participant, PMBR and MRGS measures were obtained from time-frequency plots obtained from primary motor (MI) sources, localized using beamformer differential source localization. For each participant, complimentary magnetic resonance spectroscopy (MRS) GABA measures aligned to the motor hand knob of the left central sulcus were also obtained. GABA concentration was estimated as the ratio of the motor cortex GABA integral to a cortical reference NAA resonance at 2 ppm. A significant linear relation was observed between MI GABA concentration and MRGS frequency (R(2)=0.46, p<0.05), with no association observed between GABA concentration and MRGS power. Conversely, a significant linear relation was observed between MI GABA concentration and PMBR power (R(2)=0.34, p<0.05), with no relation observed for GABA concentration and PMBR frequency. Finally, a significant negative linear relation between the participant's age and MI gamma frequency was observed, such that older participants had a lower gamma frequency (R(2)=0.40, p<0.05). Present findings support a role for GABA in the generation and modulation of endogenous motor cortex rhythmic beta and gamma activity.

Computed tomography-guided aspiration versus key-hole craniotomy for spontaneous putaminal haemorrhage: a prospective comparison of minimally invasive procedures

OBJECTIVES

To compare the effectiveness of two minimally invasive procedures, namely computed tomography-guided aspiration and the key-hole approach, in the neurosurgical management for spontaneous putaminal haemorrhage, and to explore the indications for the two approaches.

DESIGN

A multicentre, single-blinded controlled trial.

SETTING

Hospitals taking part in this trial and the sources for patients were from China. Among others, the hospitals involved in the interventions included: the Beijing Tiantan Hospital (of the Capital University of Medical Sciences), the General Hospital of People's Liberation Army, the Peking Union Hospital, and the Shanghai Huashan Hospital (of the Fudan University medical school).

PATIENTS

From September 2001 to November 2003, data were available for analysis from a total of 841 patients with spontaneous putaminal haemorrhage from 135 hospitals all over China (except Tibet, Hong Kong, Taiwan, and Macao). All follow-up data were for at least 3 months.

MAIN OUTCOME MEASURES

Mortality, Glasgow Coma Scale score, postoperative complications, Kanofsky Performance Scale score, and Barthel Index.

RESULTS

There were 563 patients who underwent computed tomography-guided aspiration, and 165 were treated by the key-hole approach. Respective mortality rates 1 month after the operation were 17.9% and 18.3%; at 3 months they were 19.4% and 19.4%. In those undergoing computed tomography-guided aspiration, mortality rates at 3 months after the operation were 28.2% in patients with Glasgow Coma Scale scores of 8 or below, as opposed to 8.2% in those with higher scores. This amounted to a 3.4-fold difference. In those treated by the key-hole approach, the corresponding rates were 30.2% and 7.6%, which amounted to a 4-fold difference. The corresponding mortality at 3 months in patients with complications was 3.9 times as great as in those without complications. In those with haematoma volumes of 70 mL or greater, it was 2.7 times as much as in those in whom the volumes below 30 mL. The postoperative complication rate of computed tomography-guided aspiration (23.7%) did not differ significantly from that in those having the key-hole approach (25.7%) [P=0.420].

CONCLUSIONS

Computed tomography-guided aspiration is not superior to the key-hole approach for treating spontaneous putaminal haemorrhage in terms of favourable outcomes, mortality, and morbidity. However, it could be the first-choice approach for those with bleeds of 50 mL or less, while the key-hole approach may be more suitable for those with larger haematomas.

Mesenchymal Stem Cells Genetically Modified with the Angiopoietin-1 Gene Enhanced Arteriogenesis in a Porcine Model of Chronic Myocardial Ischaemia

The direct injection by thoracoscope of mesenchymal stem cells (MSCs) that had been genetically modified to express angiopoietin-1 was investigated in a porcine model to determine their effect on arteriogenesis and the effectiveness of this technique. Chronic myocardial ischaemia was established using a thoracoscope to insert an ameroid constrictor around the left circumflex coronary artery. Six weeks after establishing the ischaemia, 20 pigs were randomly divided into three groups to receive injections by thoracoscope of either genetically-modified MSCs, unmodified MSCs or phosphate-buffered saline into the ischaemic border area. The injections were repeated 1 month later. The genetically modified MSCs were found to restore blood flow significantly more than the other observed treatments and immunohistochemical evaluation of arteriogenesis supported this finding. In conclusion, the injection of MSCs that had been genetically modified to express angiopoietin-1 improved arteriogenesis and increased collateral blood flow in the myocardial ischaemic area. Thoracoscope delivery of the injection was safe and minimally invasive.

Natural history of Canavan disease revealed by proton magnetic resonance spectroscopy (1H-MRS) and diffusion-weighted MRI

Canavan disease is a childhood leukodystrophy caused by mutations in the gene for human aspartoacylase ( ASPA), which leads to an abnormal accumulation of the substrate molecule N-acetyl-aspartate (NAA) in the brain. This study was designed to model the natural history of Canavan disease using MRI and proton magnetic resonance spectroscopy ( (1)H-MRS). NAA and various indices of brain structure (morphology, quantitative T1, fractional anisotropy, apparent diffusion coefficient) were measured in white and gray matter regions during the progression of Canavan disease. A mixed-effects statistical model was used to fit all outcome measures. Longitudinal data from 28 Canavan patients were directly compared in each brain region with reference data obtained from normal, age-matched pediatric subjects. The resultant model can be used to non-invasively monitor the natural history of Canavan disease or related leukodystrophies in future studies involving drug, gene therapy, or stem cell treatments.

Mild-onset presentation of Canavan's disease associated with novel G212A point mutation in aspartoacylase gene

We describe two sisters with a mild-onset variant of Canavan's disease who presented at age 50 and 19 months with developmental delay but without macrocephaly, hypotonia, spasticity, or seizures. Remarkably, both patients had age-appropriate head control, gross motor development, and muscle tone. There were very mild deficits in fine motor skills, coordination, and gait. Both sisters had a history of strabismus, but otherwise vision was normal. The older child showed evidence of mild cognitive and social impairment, whereas language and behavior were normal for age in the infant. Both patients were found to be compound heterozygotes for C914A (A305E) and G212A (R71H) mutations in ASPA. Like all other known ASPA mutations, this previously unknown G212A mutation appears to have low absolute enzyme activity. Nevertheless, it is associated in these patients with an extremely benign phenotype that is highly atypical of Canavan's disease. Biochemical and clinical data were evaluated using a generalized linear mixed model generated from 25 other subjects with Canavan's disease. There were statistically significant differences in brain chemistry and clinical evaluations, supporting a distinct variant of Canavan's disease. Future studies of ASPA enzyme structure and gene regulation in these subjects could lead to a better understanding of Canavan's pathophysiology and improvements in ASPA gene therapy.

The optical properties of ZnO hexagonal prisms grown from poly (vinylpyrrolidone)-assisted electrochemical assembly onto Si (111) substrate

ZnO hexagonal prisms have been grown from poly (vinylpyrrolidone)-assisted electrochemical assembly onto p-type Si (111) substrate. These ZnO prisms arrays are highly (0002) orientated. The (0001) end facets and {1010} side facets of the hexagonal prisms are well defined. The photoluminescence (PL) spectrum of these ZnO prisms shows an intense ultraviolet near band-gap emission with a full width at half maximum of 86 meV at room temperature. The low-temperature PL spectrum is split into well-resolved free and bound exciton emission lines. The temperature dependence of the exciton emission intensities shows a nonmonotonic decaying behavior, which can be explained by the existence of interfacial states.