scholarly journals Advances in Spiral fMRI: A High-resolution Study with Single-shot Acquisition

2019 ◽  
Author(s):  
Lars Kasper ◽  
Maria Engel ◽  
Jakob Heinzle ◽  
Matthias Mueller-Schrader ◽  
Nadine N. Graedel ◽  
...  
Keyword(s):  
Image Reconstruction ◽  
Static Field ◽  
7 Tesla ◽  
List Type ◽  
Single Shot ◽  
Planar Imaging ◽  
Spatiotemporal Resolution ◽  
Signal Model ◽  
Spiral Imaging ◽  
Spiral Readout

AbstractSpiral fMRI has been put forward as a viable alternative to rectilinear echo-planar imaging, in particular due to its enhanced average k-space speed and thus high acquisition efficiency. This renders spirals attractive for contemporary fMRI applications that require high spatiotemporal resolution, such as laminar or columnar fMRI. However, in practice, spiral fMRI is typically hampered by its reduced robustness and ensuing blurring artifacts, which arise from imperfections in both static and dynamic magnetic fields.Recently, these limitations have been overcome by the concerted application of an expanded signal model that accounts for such field imperfections, and its inversion by iterative image reconstruction. In the challenging ultra-high field environment of 7 Tesla, where field inhomogeneity effects are aggravated, both multi-shot and single-shot 2D spiral imaging at sub-millimeter resolution was demonstrated with high depiction quality and anatomical congruency.In this work, we further these advances towards a time series application of spiral readouts, namely, single-shot spiral BOLD fMRI at 0.8 mm in-plane resolution. We demonstrate that spiral fMRI at 7 T is not only feasible, but delivers both competitive image quality and BOLD sensitivity, with a spatial specificity of the activation maps that is not compromised by artifactual blurring. Furthermore, we show the versatility of the approach with a combined in/out spiral readout at a more typical resolution (1.5 mm), where the high acquisition efficiency allows to acquire two images per shot for improved sensitivity by echo combination.HighlightsThis work reports the first fMRI study at 7T with spiral readout gradient waveforms.We achieve spiral fMRI with sub-millimeter resolution (0.8 mm, in-plane FOV 230 mm), acquired in a single shot.Spiral images exhibit intrinsic geometric congruency to anatomical scans, and spatially highly specific activation patterns.Image reconstruction rests on a signal model expanded by measured trajectories and static field maps, inverted by cg-SENSE.We assess generalizability of the approach for spiral in/out readouts, providing two images per shot (1.5 mm resolution).

scholarly journals SCALE-PWI: A Pulse Sequence for Absolute Quantitative Cerebral Perfusion Imaging

2010 ◽  
Vol 31 (5) ◽  
pp. 1272-1282 ◽  
Author(s):  
Jessy Mouannes Srour ◽  
Wanyong Shin ◽  
Saurabh Shah ◽  
Anindya Sen ◽  
Timothy J Carroll
Keyword(s):  
Image Reconstruction ◽  
Cerebral Perfusion ◽  
Cerebral Blood Volume ◽  
Pulse Sequence ◽  
Patient Specific ◽  
Dynamic Susceptibility ◽  
Single Shot ◽  
Planar Imaging ◽  
Perfusion Image ◽  
Scan Time

The Bookend technique is a magnetic resonance imaging (MRI) dynamic susceptibility contrast method that provides reliable quantitative measurement of cerebral blood flow (CBF) and cerebral blood volume (CBV). The quantification is patient specific, is derived from a steady-state measurement of CBV, and is obtained from T1 changes in the white matter and the blood pool after contrast agent injection. In the current implementation, the Bookend technique consists of three scanning steps requiring a cumulative scan time of 3minutes 47seconds, a well-trained technologist, and extra time for offline image reconstruction. We present an automation and acceleration of the multiscan Bookend protocol through a self-calibrating pulse sequence, namely Self-Calibrated Epi Perfusion-Weighted Imaging (SCALE-PWI). The SCALE-PWI is a single-shot echo-planar imaging pulse sequence with three modules and a total scan time of under 2minutes. It provides the possibility of performing online, quantitative perfusion image reconstruction, which reduces the latency to obtain quantitative maps. A validation study in healthy volunteers ( N = 19) showed excellent agreement between SCALE-PWI and the conventional Bookend protocol ( P > 0.05 with Student's t-test, r = 0.95/slope = 0.98 for quantitative CBF, and r = 0.91/slope = 0.94 for quantitative CBV). A single MRI pulse sequence for absolute quantification of cerebral perfusion has been developed.

scholarly journals A single-shot measurement of time-dependent diffusion over sub-millisecond timescales using static field gradient NMR

2021 ◽  
Vol 154 (11) ◽  
pp. 111105
Author(s):  
Teddy X. Cai ◽  
Nathan H. Williamson ◽  
Velencia J. Witherspoon ◽  
Rea Ravin ◽  
Peter J. Basser
Keyword(s):  
Field Gradient ◽  
Static Field ◽  
Time Dependent ◽  
Single Shot

scholarly journals Improved image reconstruction for partial fourier gradient-echo echo-planar imaging (EPI)

2008 ◽  
Vol 59 (4) ◽  
pp. 916-924 ◽  
Author(s):  
Nan-kuei Chen ◽  
Koichi Oshio ◽  
Lawrence P. Panych
Keyword(s):  
Image Reconstruction ◽  
Echo Planar Imaging ◽  
Gradient Echo ◽  
Planar Imaging ◽  
Echo Planar

scholarly journals Embolic Complications of Endovascular Surgery for Cerebrovascular Diseases Evaluation with Diffusion-Weighted MR Imaging

2000 ◽  
Vol 6 (1_suppl) ◽  
pp. 223-226 ◽  
Author(s):  
H. Sakai ◽  
N. Sakai ◽  
I. Nakahara ◽  
T. Shimozuru ◽  
T. Higashi ◽  
...  
Keyword(s):  
Mr Imaging ◽  
B Value ◽  
Cerebrovascular Diseases ◽  
Endovascular Surgery ◽  
Single Shot ◽  
Planar Imaging ◽  
Diffusion Weighted ◽  
Screening Study ◽  
Cerebral Ischemic ◽  
Echo Planar

The purpose of this study was to evaluate asymptomatic embolisms during cerebral endovascular surgery for cerebrovascular diseases with diffusion-weighted magnetic resonance imaging (DWI) which allowed sensitive and early detection of cerebral ischemic lesions. 71 patients who underwent a total of 74 cerebral endovascular procedures were subjected to DWI screening study. MR imaging was performed on a 1.5T system by using single-shot SE echo-planar imaging (EPI) with b value of 1100 seconds per mm2 in pre- and post-treatment periods (between day 2 and 5 after procedures). In 38 (51.3%) of 74 procedures, new high intensity lesions, as recent infarctions related to procedures, were detected on post-procedural DWI. In 18 Of the patients (47.4%), symptomatic infarctions occurred and resulted in TIAs (n = 4), RINDs (n = 8), minor strokes (n = 6) and no major strokes and no death. 20 (52.6%) of the recent infarctions detected by DWI were asymptomatic lesions. Most of the asymptomatic ischemic lesions were likely to be distributed in watershed border areas. On the other hand, symptomatic lesions tended to be distributed in cortical and/or perforator regions and to be multiple. Thus, DWI is a useful method that can detect neurologically silent and asymptomatic ischemic lesions. It can be used to help to evaluate the safety and efficacy of neurovascular intervention.

Single-shot speckle correlation fluorescence microscopy in thick scattering tissue with image reconstruction priors

2018 ◽  
Vol 11 (3) ◽  
pp. e201700224 ◽  
Author(s):  
Julie Chang ◽  
Gordon Wetzstein
Keyword(s):  
Image Reconstruction ◽  
Fluorescence Microscopy ◽  
Single Shot ◽  
Speckle Correlation

Quantitative susceptibility mapping using single-shot echo-planar imaging

2014 ◽  
Vol 73 (5) ◽  
pp. 1932-1938 ◽  
Author(s):  
Hongfu Sun ◽  
Alan H. Wilman
Keyword(s):  
Echo Planar Imaging ◽  
Susceptibility Mapping ◽  
Single Shot ◽  
Planar Imaging ◽  
Quantitative Susceptibility Mapping ◽  
Echo Planar

scholarly journals Training neural networks to recognize speech increased their correspondence to the human auditory pathway but did not yield a shared hierarchy of acoustic features

2021 ◽  
Author(s):  
Jessica A.F. Thompson ◽  
Yoshua Bengio ◽  
Elia Formisano ◽  
Marc Schönwiesner
Keyword(s):  
Neural Networks ◽  
Recognition Task ◽  
Single Layer ◽  
Auditory Pathway ◽  
7 Tesla ◽  
List Type ◽  
Acoustic Features ◽  
Visual Areas ◽  
Cortical Regions ◽  
Fully Connected

AbstractThe correspondence between the activity of artificial neurons in convolutional neural networks (CNNs) trained to recognize objects in images and neural activity collected throughout the primate visual system has been well documented. Shallower layers of CNNs are typically more similar to early visual areas and deeper layers tend to be more similar to later visual areas, providing evidence for a shared representational hierarchy. This phenomenon has not been thoroughly studied in the auditory domain. Here, we compared the representations of CNNs trained to recognize speech (triphone recognition) to 7-Tesla fMRI activity collected throughout the human auditory pathway, including subcortical and cortical regions, while participants listened to speech. We found no evidence for a shared representational hierarchy of acoustic speech features. Instead, all auditory regions of interest were most similar to a single layer of the CNNs: the first fully-connected layer. This layer sits at the boundary between the relatively task-general intermediate layers and the highly task-specific final layers. This suggests that alternative architectural designs and/or training objectives may be needed to achieve fine-grained layer-wise correspondence with the human auditory pathway.HighlightsTrained CNNs more similar to auditory fMRI activity than untrainedNo evidence of a shared representational hierarchy for acoustic featuresAll ROIs were most similar to the first fully-connected layerCNN performance on speech recognition task positively associated with fmri similarity

scholarly journals Microscale dynamics of electrophysiological markers of epilepsy

2020 ◽  
Author(s):  
Jimmy C. Yang ◽  
Angelique C. Paulk ◽  
Sang Heon Lee ◽  
Mehran Ganji ◽  
Daniel J. Soper ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
High Frequency ◽  
Time Windows ◽  
List Type ◽  
Spatiotemporal Resolution ◽  
Similar Time ◽  
Human Epilepsy ◽  
High Frequency Oscillations ◽  
Peak Tracking ◽  
Interictal Discharges

AbstractObjectiveInterictal discharges (IIDs) and high frequency oscillations (HFOs) are neurophysiologic biomarkers of epilepsy. In this study, we use custom poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) microelectrodes to better understand their microscale dynamics.MethodsElectrodes with spatial resolution down to 50µm were used to record intraoperatively in 30 subjects. For IIDs, putative spatiotemporal paths were generated by peak-tracking, followed by clustering. For HFOs, repeating patterns were elucidated by clustering similar time windows. Fast events, consistent with multi-unit activity (MUA), were covaried with either IIDs or HFOs.ResultsIIDs seen across the entire array were detected in 93% of subjects. Local IIDs, observed across <50% of the array, were seen in 53% of subjects. IIDs appeared to travel across the array in specific paths, and HFOs appeared in similar repeated spatial patterns. Finally, microseizure events were identified spanning 50-100µm. HFOs covaried with MUA, but not with IIDs.ConclusionsOverall, these data suggest micro-domains of irritable cortex that form part of an underlying pathologic architecture that contributes to the seizure network.SignificanceMicroelectrodes in cases of human epilepsy can reveal dynamics that are not seen by conventional electrocorticography and point to new possibilities for their use in the diagnosis and treatment of epilepsy.HighlightsPEDOT:PSS microelectrodes with at least 50µm spatial resolution uniquely reveal spatiotemporal patterns of markers of epilepsyHigh spatiotemporal resolution allows interictal discharges to be tracked and reveal cortical domains involved in microseizuresHigh frequency oscillations detected by microelectrodes demonstrate localized clustering on the cortical surface

scholarly journals Magnetic Resonance Fingerprinting with Combined Gradient- and Spin-echo Echo-planar Imaging: Simultaneous Estimation of T1, T2 and T2* with integrated-B1 Correction

2019 ◽  
Author(s):  
Mahdi Khajehim ◽  
Thomas Christen ◽  
J. Jean Chen
Keyword(s):  
Magnetic Resonance ◽  
Spin Echo ◽  
Echo Planar Imaging ◽  
Simultaneous Estimation ◽  
Single Shot ◽  
Planar Imaging ◽  
Reconstruction Process ◽  
Data Segment ◽  
T1 And T2 ◽  
Echo Planar

AbstractPurposeTo introduce a novel magnetic-resonance fingerprinting (MRF) framework with single-shot echo-planar imaging (EPI) readout to simultaneously estimate tissue T2, T1 and T2*, and integrate B1 correction.MethodsSpin-echo EPI is combined with gradient-echo EPI to achieve T2 estimation as well as T1 and T2* quantification. In the dictionary matching step, the GE-EPI data segment provides estimates of tissue T1 and T2* with additional B1 information, which are then incorporated into the T2-matching step that uses the SE-EPI data segment. In this way, biases in T2 and T2* estimates do not affect each other.ResultsAn excellent correspondence was found between our T1, T2, and T2* estimates and results obtained from standard approaches in both phantom and human scans. In the phantom scan, a linear relationship with R2>0.96 was found for all parameter estimates. The maximum error in the T2 estimate was found to be below 6%. In the in-vivo scan, similar contrast was noted between MRF and standard approaches, and values found in a small region of interest (ROI) located in the grey matter (GM) were in line with previous measurements (T2MRF=88±7ms vs T2Ref=89±11ms, T1MRF=1153±154ms vs T1Ref=1122±52ms, T2*MRF=56±4ms vs T2*Ref=53±3ms).ConclusionAdding a spin echo data segment to EPI based MRF allows accurate and robust measurements of T2, T1 and T2* relaxation times. This MRF framework is easier to implement than spiral-based MRF. It doesn’t suffer from undersampling artifacts and seems to require a smaller dictionary size that can fasten the reconstruction process.

scholarly journals Single-shot Coherent Raman Multiplex Planar Imaging

CLEO: 2014 ◽  
2014 ◽  
Author(s):  
Alexis Bohlin ◽  
Christopher Kliewer
Keyword(s):  
Single Shot ◽  
Planar Imaging ◽  
Coherent Raman
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