Oxygen Level-dependent Imaging Research Articles

Development of computational models for microtesla-level magnetic brain scanning: a novel avenue for device development

BackgroundDetection of locally increased blood concentration and perfusion is critical for assessment of functional cortical activity as well as diagnosis of conditions such as intracerebral hemorrhage (ICH). Current paradigms for assessment of regional blood concentration in the brain rely on computed tomography (CT), magnetic resonance imaging (MRI), and perfusion blood oxygen level dependent functional magnetic resonance imaging (BOLD-fMRI).ResultsIn this study, we developed computational models to test the feasibility of novel magnetic sensors capable of detecting hemodynamic changes within the brain on a microtesla-level. We show that low-field magnetic sensors can accurately detect changes in magnetic flux density and eddy current damping signals resulting from increases in local blood concentration. These models predicted that blood volume changes as small as 1.26 mL may be resolved by the sensors, implying potential use for diagnosis of ICH and assessment of regional blood flow as a proxy for cerebral metabolism and neuronal activity. We then translated findings from our computational model to demonstrate feasibility of accurate detection of modeled ICH in a simulated human cadaver setting.ConclusionsOverall, microtesla-level magnetic scanning is feasible, safe, and has distinct advantages compared to current standards of care. Computational modeling may facilitate rapid prototype development and testing of novel medical devices with minimal risk to human participants prior to device construction and clinical trials.

Progress in research of blood oxygen level dependent functional magnetic resonance imaging in cirrhotic patients with minimal hepatic encephalopathy

Progress in research of blood oxygen level dependent functional magnetic resonance imaging in cirrhotic patients with minimal hepatic encephalopathy

Abstract P584: Sleep in Pediatric Stroke Study (SleePSS): Neuroimaging and Neurocognitive Correlates of Sleep Health in Pediatric Stroke

Introduction: Pediatric arterial ischemic stroke (AIS) is a serious cause of lifelong neurological and cognitive disabilities. Although they are at increased risk of obstructive sleep apnea (OSA), children with AIS may have abnormal sleep indices even in the absence of OSA diagnosis. This can adversely affect their blood vessels health (impaired cerebrovascular reactivity, CVR) and can lead to neurocognitive impairments. Therefore, we aimed to investigate the association of cerebral blood vessels health with polysomnographic measures and cognitive function in children with AIS. Hypothesis: Quantitative measure of negative CVR, i.e. fractional negativity (fneg) and negative CVR correlate significantly with abnormal overnight oxygen and carbon dioxide levels in children with AIS, even in the absence of OSA. Methods: We conducted a single-centre cross-sectional study in children with AIS aged between 8 and 18 years old and who were not at risk of OSA (i.e., pediatric sleep questionnaire score<0.33). All children were evaluated using: (1) Non-invasive Blood Oxygen Level Dependent magnetic resonance imaging to study CVR. (2) An overnight polysomnography (3) Comprehensive evaluation of intellectual abilities, attention and executive function. Results: Ten children with AIS (40% males; median age: 14.3 years) were included after a median of 8.8 years following stroke onset. None of the children was diagnosed with OSA. We found significant correlations between fneg and minimum oxygen saturation during REM sleep (r=0.81, r=0.68 and r=0.76 in grey matter, white matter and whole brain, respectively; p<0.05). The whole brain mean negative CVR correlated significantly with the visual spatial, fluid reasoning, and emotion regulation indices (r=-0.82, -0.8, and 0.75, respectively, p<0.05). Mean negative CVR in white matter correlated significantly with the indices of executive function (emotion regulation, cognitive regulation and global executive composite scores, r=0.72-0.76, p<0.05). Conclusion: Impaired CVR in children with AIS correlates with abnormal sleep indices even in the absence of OSA diagnosis. This can potentially result in cognitive difficulties, the majority of which remain not fully explained by stroke-related factors.

2378Blunted stress myocardial oxygenation and not myocardial perfusion reserve is associated with arrhythmic risk in hypertrophic cardiomyopathy

Abstract Background In hypertrophic cardiomyopathy (HCM), myocardial ischaemia is believed to play a role in fatal life-threatening ventricular arrhythmias and caused by microvascular dysfunction manifesting as impaired myocardial perfusion. However, previous studies suggest that myocardial oxygenation during vasodilator stress may also be blunted when perfusion is normal, due to increased metabolic demands conferred by energy-costly sarcomeric mutations, left ventricular hypertrophy and outflow obstruction. Whether or not impaired myocardial perfusion reserve or blunted stress oxygenation on cardiac magnetic resonance (CMR) predict the risk of ventricular arrhythmia in HCM is unknown. Purpose We sought to investigate if impaired myocardial perfusion reserve or stress oxygenation is associated with an increased risk of ventricular arrhythmia in HCM. Methods 103 genotyped HCM patients (mean age 47±15 years) and 32 age- and sex-matched healthy controls underwent adenosine stress blood oxygen level dependent (BOLD) imaging, first pass perfusion and late gadolinium imaging (LGE) on CMR to assess stress oxygenation (BOLD ΔSI), myocardial perfusion reserve index (MPRI), and fibrosis respectively. All HCM patients were monitored for ventricular tachycardia (≥3 beats, ≥120 beats per minute) on a 24-hour Holter. Results As expected, MPRI was significantly reduced in HCM (1.5±0.4 vs 2.0±0.3, p<0.0001) compared to controls. Stress oxygenation response was blunted in HCM versus controls (9.1±4.1% vs 17.0±1.6%, p<0.0001, Figure 1B). Twenty-six (25%) patients developed ventricular tachycardia on Holter monitoring. On univariate analysis, only stress oxygenation and not MPRI associated with ventricular tachycardia. The prevalence of ventricular tachycardia in HCM increased with decreasing quartiles of stress oxygenation (Figure 1D). HCM patients in the lowest quartile of oxygenation (BOLD ΔSI <6.5%) were at a three-fold risk of ventricular tachycardia (OR 3.04, 95% confidence interval 1.02–9.05, p=0.04) on multivariable analysis (after adjusting for sudden cardiac death risk factors and LGE mass) compared to other patients. Sarcomeric mutation status was an independent determinant of stress oxygenation on multivariable analysis. Stress oxygenation was impaired in phenotype-negative sarcomeric mutation carriers (Sarc+P-, n=16) despite normal perfusion (Figure 1C, E). Sarcomeric HCM (Sarc+HCM) had more severe impairment in stress oxygenation than genotype negative HCM (G-HCM) and controls (Figure 1E). Figure 1 Conclusion In HCM, blunted stress-induced oxygenation is associated with an increased risk of ventricular arrhythmia and may represent a novel biomarker of arrhythmic risk. Sarcomeric mutation status is an important determinant of stress oxygenation response. Acknowledgement/Funding National Institute for Health Research Oxford Biomedical Centre and British Heart Foundation.

Phase 1, Brain Circuitry Using Blood Oxygen Level Dependent (BOLD) Functional Magnetic Resonance Imaging (fMRI) and Arterial Spin Labeling (ASL) in Healthy Participants

Phase 1, Brain Circuitry Using Blood Oxygen Level Dependent (BOLD) Functional Magnetic Resonance Imaging (fMRI) and Arterial Spin Labeling (ASL) in Healthy Participants

Fundamentals of Preoperative Task Functional Brain Mapping.

Blood oxygenation level-dependent (BOLD) imaging is gaining traction in the clinical realm as a measure for quantifying changes in regional blood flow in response to external stimuli. Through the evoked signal changes that are a consequence of hemoglobin's intrinsic paramagnetic properties, this technique allows for the statistical mapping of brain regions associated with a given task, which has broad applications in preneurosurgical planning for tumor resection. From an acquisition perspective, collection of BOLD data most commonly requires the use of echo planar imaging readout schemes. These sequences are currently widely available on most clinical scanners and at various field strengths. However, while the BOLD acquisition protocol is relatively straightforward, additional hardware and rigorous image processing are needed to correlate the time-dependent signal changes associated with a specific and well defined task. This manuscript will provide the necessary information to detail the physiologic underpinning of acquiring BOLD sensitized images and the important technical aspects of processing the data for use in a surgical environment.

Study on resting-state cerebral functional magnetic resonance imaging and ambulatory urodynamics monitoring in children with primary monosympt-omatic nocturnal enuresis

Objective To investigate the significance of blood oxygenation level dependent functional magnetic resonance imaging (BOLD-fMRI) and ambulatory urodynamics monitoring (AUM) to find the cause of primary monosymptomatic nocturnal enuresis (PMNE) in children. Methods Thirty-seven children with PMNE (20 males and 17 females) were selected, with a mean age of (11.3±4.1) years old.A clinical management tool, 3-day urination record, daytime BOLD-fMRI scan, conventional urodynamics (CUD) and AUM were performed respectively.Thirty-seven gender-age matched children(19 males, 18 females) who would receive surgery treatment because of upper urinary tract disease and were confirmed to have no lower urinary tract dysfunction by CUD were enrolled as controls, with a mean age of (11.1±2.9) years old, and 13 cases underwent BOLD-fMRI scanning. Results It was found that the ALFF value of the left middle frontal gyrus of PMNE was decreased and the ReHo value of the left superior occipital gyrus was increased compared with the control group by the resting BOLD-fMRI.The maximum voiding volume of PNME children was (303.11±87.48) mL, the total urine volume at night was (568.65±208.48) mL, and the nighttime bladder volume was (217.43±81.53) mL.The incidence of maximum voiding volume reduction, nocturnal polyuria and decreased nocturnal bladder volume were 24.32% and 56.76%, and 64.86%, respectively.However, AUM results showed that maximum detrusor pressure in the PMNE group was (39.22±7.78) cmH2O(1 cmH2O=0.098 kPa), which was statistically significantly higher than that in CUD (32.22±9.00) cmH2O, and the difference was statistically significant (P 0.05). Conclusions The abnormal functions of the left middle frontal gyrus and left superior occipital gyrus, nighttime DO and the decrease of bladder capacity at night are considered to be key causes of enuresis in children with PMNE.AUM and resting state BOLD-fMRI evaluations are helpful in differentiating the pathogenesis of PMNE. Key words: Enuresis; Ambulatory urodynamics monitoring; Functional magnetic resonance imaging; Resting state

The research progress of three kinds of brain imaging techniques in cognitive dysfunction

Background Magnetic resonance imaging (MRI) is a common imaging methods, along with the development of science and technology, a functional magnetic resonance imaging (fMRI), can reflect the level of neural activity of the brain, location of brain regions that perform special function, determination of cerebral metabolism, nerve fiber tracer. Objective Advantages of brain imaging technology and the current application situation are summarized in this paper. Content This article reviews the fMRI containing blood oxygen level dependent (BOLD) and diffusion tensor imaging (DTI), magnetic resonance spectral imaging (MRS), the three technologies in cognitive dysfunction related research. Trend This review covers research advances that exploring the changes of functional areas in patients, providing an objective and intuitive imaging basis for early prevention and diagnosis. Key words: Cognitive dysfunction; Functional magnetic resonance imaging; Blood oxygen level dependent; Diffusion tensor imaging; Magnetic resonance spectroscopic imaging

The value of blood oxygen level dependent (BOLD) imaging in evaluating post-operative renal function outcomes after laparoscopic partial nephrectomy.

To assess the ability of renal blood oxygen level dependent (BOLD) MRI metrics to predict post-operative renal function. We studied 152 patients who underwent laparoscopic partial nephrectomy (LPN) and renal MRI examination including BOLD. Short-term and long-term renal function was evaluated using the glomerular filtration rate (GFR) derived from renal scintigraphy. Renal function decline was assessed as the absolute decline (AD), percentage decline (PD) and optimal renal function preservation (OP). T2* values were analysed in the renal cortex and medulla ipsilateral and contralateral to the tumour. Clinical characteristics and imaging metrics were evaluated using univariate and multivariate linear regression analyses. Risk factors obtained using BOLD metrics (determined by multivariate regression) were then combined and compared with RENAL scores to predict OP. Increasing warm ischaemia time (WIT), resected and ischaemic volume (RAIV), larger tumour size, higher RENAL score and lower preoperative GFR were short-term risk factors for AD, while increasing WIT and lower preoperative GFR were significant for long-term outcomes. Increasing WIT, RAIV, lower T2* value in the cortex and higher T2* value in the medulla on the ipsilateral side were short-term risk factors for PD, while all of the above factors (except WIT and RAIV) were significant for long-term outcomes. The performance of the combination of T2* values in the cortex and medulla on the ipsilateral side to tumour in predicting OP was better than RENAL score (AUC 0.762 vs 0.634, p = 0.013). Renal BOLD-MRI metrics could provide useful information to the clinician in predicting post-operative renal function outcomes. • Renal fMRI metrics may be useful for prediction of renal functional outcomes and merit further study. • Renal fMRI metrics may reflect degree of baseline disease and ability to tolerate warm ischaemia. • Combination of T2* values was better than RENAL score for predicting OP.

Effect of Repeated Injection of Iodixanol on Renal Function in Healthy Wistar Rats Using Functional MRI.

Purpose To determine the optimal time interval of repeated intravenous injections of iodixanol in rat model and to identify the injury location and causes of renal damage in vivo. Materials and Methods Rats were randomly divided into Control group, Group 1 with one iodixanol injection, and Group 2 with two iodixanol injections. Group 2 was subdivided into 3 cohorts according to the interval between the first and second iodixanol injections as 1, 3, and 5 days, respectively. Blood oxygen level-dependent (BOLD) imaging and diffusion weighted imaging (DWI) were performed at 1 hour, 1 day, 3 days, 5 days, and 10 days after the application of solutions. Results Compared with Group 1 (7.2%), Group 2 produced a remarkable R2⁎ increment at the inner stripe of the renal outer medulla by 15.37% (P = 0.012), 14.83% (P = 0.046), and 13.53% (P > 0.05), respectively, at 1 hour after repeated injection of iodixanol. The severity of BOLD MRI to detect renal hypoxia was consistent with the expression of HIF-1α and R2⁎ was well correlated with HIF-1α expression (r = 0.704). The acute tubular injury was associated with urinary NGAL and increased significantly at 1 day. Conclusions Repetitive injection of iodixanol within a short time window can induce acute kidney injury, the impact of which on renal damage in rats disappears gradually 3–5 days after the injections.

A preliminary fMRI study of acupuncture with healthy volunteers

Objective To observe the cortical functioning of healthy volunteers during acupuncture as a way of exploring acupuncture′s neural mechanisms. Methods Twenty healthy volunteers received acupuncture applied to the left hegu and waiguan acupoints while their cortical activity was examined using blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI). Brain activation, especially of the regions related to motor function, were observed and analyzed. Results Acupuncture applied to the left hegu and waiguan acupoints was observed to significantly activate the left middle frontal gyrus and the inferior frontal gyrus, with many activated regions in the left insula and a few in the left cerebellum, the left precentral gyrus, the left postcentral gyrus, the left inferior parietal lobule, the left medial frontal gyrus, the left precuneus, the left anterior cingulate gyrus and the left claustrum. The right side of the brain was excited mainly in the right middle frontal gyrus and the right medial frontal gyrus. The right inferior parietal lobule and the right precentral gyrus were also activated to some extent. There was slight activation of the right middle temporal gyrus, the right superior temporal gyrus, the right insula, the right inferior frontal gyrus and the right postcentral gyrus. The negatively activated regions were mainly located on both sides of the limbic lobe, including the hippocampus, the parahippocampal gyrus and the cingulate gyrus. The left superior temporal gyrus, the left middle temporal gyrus and the right middle frontal gyrus also had small negative activation zones. Conclusions In brain regions associated with motor function, in addition to partial activation of the contralateral primary sensorimotor area, acupuncture at these two points clearly generates bilateral activation of secondary motor areas with some activation in the ipsilateral cerebellum. This may serve as a neuropathological basis for acupuncture treatment of motor dysfunction. BOLD-fMRI imaging displays the neural effects of acupuncture in an intuitive way. It can be a useful technique for further study of the neural effects of acupuncture on pathological conditions. Key words: Acupuncture; Hegu; Waiguan; Functional magnetic resonance imaging

Scalp cluster acupuncture combined with constraint-induced movement therapy improves functional recovery after ischemic stroke

Objective To compare the effect of clustered acupuncture of the scalp combined with constraint-induced movement therapy (CIMT) with that of conventional acupuncture of the body points plus conventional rehabilitation intervention after cerebral infarction using blood oxygenation level dependent functional magnetic resonance imaging (BOLD-fMRI). Methods Thirty acute cerebral infarction patients with hemiplegia were equally divided into two groups at random. The test group received the clustered acupuncture of the scalp combined with CIMT, while the control group received the body point acupuncture plus conventional rehabilitation intervention. Before and after two weeks of treatment, blood oxygenation level-dependent functional magnetic resonance imaging at 3.0 T was performed during a passive digital opposition movement. The volume and intensity of the activated areas were compared. Fugl-Meyer assessment (FMA) was carried out as well. Results The most pronounced activation appeared in the contralateral somatosensory motor cortex for both groups. There was no significant difference in average FMA scores between the two groups before the treatment, but after the treatment the averages were significantly different. An increase in activated volume and intensity in the contralateral SMC was observed in both groups after the treatment, but the test group showed a much larger change in both activated volume and intensity. Conclusion The clustered acupuncture of the scalp combined with CIMT can achieve a more significant improvement in functional recovery after acute cerebral infarction than conventional acupuncture of the body points plus conventional rehabilitation intervention. Such combined therapy is worthy of application in clinical practice. Key words: Scalp; Acupuncture; Constraint-induced movement therapy; Functional MRI; Cerebral infarction

Clinical application of intraoperative MRI navigation in microsurgical resection of cerebral arteriovenous malformations located near the main functional areas

Objective To evaluate the efficacy and safety of intraoperative MRI navigation in the microsurgical treatment of arteriovenous malformations (AVM) located near the main functional areas of brain. Methods A total of 53 patients with AVM in the adjacent functional areas were treated by microsurgical operation with intraoperative MRI navigation and electrophysiological monitoring. Blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) and diffusion tensor imaging (DTI) examinations were performed before and during operation. We fused BOLD-fMRI and DTI images to form three-dimensional images containing lesions, important functional areas and pyramidal tract so as to study the relationship between them and their changes before and after operation. Results The diameter of malformations in 53 patients was 2-7 cm, on average of (3.41 ± 0.85) cm. There were 6 patients involved in sensory areas, 7 patients in motor areas, 10 patients in pyramidal tract, 14 patients in language areas, 2 patients in visual cortex, 9 patients in optic radiation, 2 patients in basal ganglia and 3 patients in brain stem. Gross total resection was achieved in 49 patients while full functionality was retained. The other 4 patients with intraoperative MRI navigation were found that malformations and functional areas were closely related, so the lesions were partially resected. There were 8 patients with new-onset postoperative neurological dysfunction, among whom one case was found bilateral visual field defects, 3 patients' muscle tone was lower than before, one case of facial paralysis, 2 cases of aphasia, one with decreased muscle tone and motor aphasia. Follow-up period varied from 3 to 60 months [median 19.37 (6.00, 30.00) months], and 2 cases died (one died of respiratory failure after one year, and the other was agnogenic). Glasgow Outcome Scale (GOS) score was 5 in 45 cases (84.91%), 4 in 3 cases (5.66%), 3 in 2 cases (3.77%), 2 in one case (1.89%) and one in 2 cases (3.77%). Conclusions With the application of intraoperative MRI navigation and electrophysiological monitoring, it may be appropriate to expand the surgical indications of AVM located near the main functional areas of brain. DOI: 10.3969/j.issn.1672-6731.2016.12.006

WE-FG-BRA-03: Oxygen Interplay in Hypofractionated Radiotherapy: A Hidden Opportunity

Purpose: Local oxygen during a radiotherapy fraction has been shown to change over a full range of the oxygen enhancement ratio (OER) during the same time scale as the treatment fraction. Interplay with local oxygen is then likely a concern, especially for hypofractionation. Our experiments that show a strong role for metabolic dynamics suggesting one could manipulate this interplay for more efficacious treatments. Methods: Two published experiments are presented with the same human head and neck cancer cell line (UM-SCC-22B). One is a cell-specific in vitro prompt response to a 10 Gy dose of orthovotage radiation using fluorescence lifetime imaging (FLIM), benchmarked with a Seahorse assay. The other in vivo study uses autocorrelation analysis with blood oxygen level dependent magnetic resonance imaging (MRI-BOLD) on xenografts. In vivo results are verified with diffuse optics using spectra fitting and photoacoustic measurements. All these measurements are at high time resolution: sampling is one per minute. Results: Interplay happens when the radiosensitivity modulates at the same time scale as the radiation. These results show dynamics at these time scales. 1. The dominant time scale of the acute hypoxia in cell line xenografts is shown to be on the order of minutes to tens of minutes: similar to a metabolic oscillation known as the ‘glycolytic oscillator.’ 2. The radiation dose itself alters metabolism within minutes to tens of minutes also. Conclusion: These results vary with cell type. There is a possibility that special timing and dose levels could be used for radiation. Gating could be used for maximal oxygen during treatment. There is an analogy to the interplay discussions with tumor motion, except that an oxygen interplay could more likely be patient-specific at a more fundamental level.

Hyperoxia and Functional MRI.

Oxygen plays a fundamental role in functional magnetic resonance imaging (FMRI). Blood oxygenation level-dependent (BOLD) imaging is the foundation stone of all FMRI and is still the essential workhorse of the vast majority of FMRI procedures. Hemoglobin may provide the magnetic properties that allow the technique to work, but it is oxygen that allows the contrast to effectively be switched on or off, and it is oxygen that we are interested in tracking in order to observe the oxygen metabolism changes. In general the changes in venous oxygen saturation are observed in order to infer changes in the correlated mechanisms, which can include changes in cerebral blood flow, metabolism, and the fraction of inspired oxygen. By independently manipulating the fraction of inspired oxygen it is possible to alter the amount of dissolved oxygen in the plasma, the venous saturation, or even the blood flow. The effects that these changes have on the observed MRI signal can be either a help or a hindrance depending on how well the changes induced are understood. The administration of supplemental inspired oxygen is in a unique position to provide a flexible, noninvasive, inexpensive, patient-friendly addition to the MRI toolkit to enable investigations to look beyond statistics and regions of interest, and actually produce calibrated, targeted measurements of blood flow, metabolism or pathology.

Resting-state functional magnetic resonance imaging study of the pathogenesis of hemifacial spasm

Objective To explore the changes of brain function activity under the resting state in patients with hemifacial spasm (HFS). Methods Thirty patients with HFS (HFS group) and 33 healthy controls (HC group) admitted to the Department of Neurosurgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine performed blood oxygen level-dependent functional magnetic resonance imaging (BOLD-fMRI) examination from July 2013 to December 2013. The regional homogeneity (ReHo) method was used to analyze the differences of spontaneous brain activity between the two groups. Results There were no significant differences in age, gender and years of education between the 2 groups. They had comparability. Compared with the HC group, the brain regions of the HFS group included the increased ReHo values of pons, posterior lobe of cerebellum and precentral motor area (adjusted AlphaSim, P<0.01). The largest difference voxel was in the precentral motor area, followed by posterior lobe of cerebellum, and the smallest difference voxel was pons, but the increased ReHo value of the latter was most significant (t=3.83); the ReHo values of the supplementary motor area, superior temporal gyrus, precuneus, middle frontal gyrus, and cingulate gyrus of the HFS group decreased (adjusted AlphaSim, P<0.01). The largest difference voxel and ReHo value was cingulate gyrus. (t=-3.69). Conclusion Under the resting state, brains involve in the activation of the cortices of facial muscle movement and the excitability of gray matter nuclei increase in patients with HFS, and the cortices involving in the inhibition of facial muscle movement have function weakening, these changes may involve in the pathological progress of HFS. Key words: Hemifacial spasm; Magnetic resonance imaging; Resting-state; Regional homogeneity

Noninvasive evaluation of renal oxygenation in primary nephrotic syndrome with blood oxygen level dependent magnetic resonance imaging: Initial experience

To use blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) to evaluate renal oxygenation in patients with primary nephrotic syndrome (PNS), and test the hypothesis that renal tissue oxygenation correlates with renal function, tubulointerstitial alterations and treatment response. Patients with untreated first-onset PNS and healthy control subjects underwent BOLD MRI. Blood and urine samples were obtained on the day of MRI, and patients underwent renal biopsy the day after MRI. Renal tubulointerstitial damage scores (TIDS) were determined using Katafuchi criteria. All patients received corticosteroids within 7 days after MRI and were followed up for 12 months. Medullary R2* values were significantly lower in patients with PNS (n = 20) than controls (n = 18). Medullary R2* values were negatively correlated with estimated glomerular filtration rates and positively correlated with TIDS in patients with PNS. There were no significant differences in medullary or cortical R2* values when patients were classified according to treatment response. The medullary oxygen concentration was higher in patients with PNS than in control subjects. BOLD MRI was a useful noninvasive method for the evaluation of renal function and tubulointerstitial impairment.

Preclinical alterations in cardiac energetics amongst sarcomere mutation carriers in hypertrophic cardiomyopathy

Background Hypertrophic cardiomyopathy (HCM) is characterised by reduced myocardial tissue oxygenation (assessed using blood oxygen level dependent (BOLD) CMR imaging) during stress, as well as reduced myocardial perfusion reserve (MPRI) due to coronary microvascular dysfunction. In HCM gene carriers without the HCM phenotype, it has been suggested that only oxygenation is impaired. [1] It remains unclear whether this relates to early cardiac remodelling/ diastolic dysfunction, or whether oxygen consumption is intrinsically altered with sarcomere mutations. We sought to assess the BOLD signal change during vasodilator stress in a homogenous group of MYPBC3 positive HCM patients (some with clinical HCM, and some with no phenotypic features of HCM), and normal controls.

Abstract W P29: Tissue Plasminogen Activator Mediated Reperfusion, and Subsequent Improvement in Resting State Connectivity Correlates with Functional Outcome in Acute Ischemic Stroke Patients

Background: Intravenous Tissue Plasminogen Activator (TPA) is the only FDA approved medical therapy for acute ischemic stroke (AIS). Prior study suggests that early recanalization is associated with better stroke outcome. Our aim was to correlate task-negative and task-positive (TN/TP) resting state network activity with tissue perfusion and functional outcome, in stroke patients who received TPA. Method: AIS patients were consented and underwent NIH stroke scale (NIHSS) assessment and magnetic resonance imaging (MRI) scans during TPA infusion (baseline) and six hours post stroke. The MRI sequences include contrast-enhanced perfusion weighted image (PWI) and resting state Blood Oxygen Level-Dependent or BOLD (RSB) images acquired using a Siemens Treo 3T MRI scanner. Additionally, the RSB scan and the NIHSS were obtained at a 30-day follow up visit. Results: Fourteen patients (mean age ± SD=63 ±14, 50% male, 50% white, 43% black and 7% others) who qualified for TPA completed the study at baseline and 6 hours post stroke. Of these, 6 patients had valid follow up data at 30 days. Three patients without cerebral ischemia were excluded. A paired samples t-test comparing baseline and 6h post stroke showed a significantly improved TP network t(10)= -4.24 p&lt; 0.05. The resting network connectivity improved from 6 hours post stroke to 30-days follow up, t(5)= -5.35 p&lt; 0.01. Similarly, NIHSS, at 6h post stroke t(10)= 3.62 p&lt; 0.01 and at 30-days follow up t(5)= -3.4 p&lt; 0.01 were significantly better than the NIHSS at baseline. The 6-hours post-stroke perfusion correlated with the resting network connectivity in both the damaged (r=-0.56 p= 0.07) and intact hemispheres (r= -0.57 p= 0.06). Differences in functional connectivity and NIHSS scores from baseline to 6 h were positively correlated (r= 0.56 p=0.07). Conclusion: In this pilot study we found that TPA led to changes in MRI based resting state networks and associated functional outcome. Correlations were found between perfusion, functional connectivity and NIHSS. This suggests that the improvement of resting state network means improved efficiency of brain activity indicated by functional outcome and may be a potential predictive MRI biomarker for TPA response. A larger study is needed to verify this finding.

Blood oxygen level and the pathogenic mechanism of expressive aphasia after stroke

Objective To evaluate the activation patterns in the cortexes of expressive aphasics after stroke so as to explore the pathogenic mechanism of expressive aphasia.Methods Blood oxygen level dependent functional magnetic resonance imaging (BOLD-fMRI) was the method of choice.It was administered to 9 subjects with expressive aphasia at 1 to 3 months post-stroke onset and to 10 healthy controls.Active areas in the patients' brains were observed using a block-designed picture-naming task,and language function was tested with the China Rehabilitation Research Center's aphasia examination (CRRCAE).The control group received BOLD-fMRI only.SPM8 software was used to process the fMRI data.Results Differences were observed in the mapping of activated areas between the two groups,but many activated areas showed no difference.Significant differences in activation were observed in areas associated with vision,language and cognition,including the bilateral inferior frontal gyrus,the bilateral superior temporal gyrus,the bilateral insula,the bilateral basal ganglia,the left superior frontal gyrus,the left middle frontal gyrus,the left precentral gyrus,the left thalamus,and the left middle temporal gyrus.All the patients had activated cortex regions associated with visual processing in the left and/or right hemisphere,such as the middle frontal gyrus,the middle temporal gyrus,the lingual gyrus and the fusiform gyrus.The activation volumes in the left hemisphere were significantly smaller than those in normal adults.Regions related to language such as the left inferior frontal gyrus (Broca's area),the left middle frontal gyrus,and the right inferior frontal gyrus (the mirror region of Broca's area) were activated in some of them.While the activation frequency,activated volume and activation intensity generally were all less in the patients than in the controls,the activation intensity in the right superior temporal gyrus,the bilateral superior parietal lobule and the left inferior temporal gyrus were stronger.Conclusions Language production may be associated with multiple,interconnected regions.The right hemisphere participates in natural language processing.Aphasia damages both linguistic and cognitive areas,reducing activation in Broca's aphasia.Activation areas in the left hemisphere and the right inferior frontal gyrus decrease significantly,while some regions in the right hemisphere are relatively more activated.The right inferior frontal gyrus may play a different role in language recovery at different periods of aphasia after stroke. Key words: Expressive aphasia; Functional magnetic resonance imaging; Brain activation; Language mechanisms