scholarly journals Reducing SAR in 7T brain fMRI by circumventing fat suppression while removing the lipid signal through a parallel acquisition approach

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Amir Seginer ◽  
Edna Furman-Haran ◽  
Ilan Goldberg ◽  
Rita Schmidt
Keyword(s):  
Fat Suppression ◽  
Planar Imaging ◽  
Brain Images ◽  
Water Separation ◽  
Parallel Acquisition ◽  
Functional Studies ◽  
Spatial Shift ◽  
Lipid Signal ◽  
Repetition Time ◽  
Slice Method

AbstractUltra-high-field functional magnetic resonance imaging (fMRI) offers a way to new insights while increasing the spatial and temporal resolution. However, a crucial concern in 7T human MRI is the increase in power deposition, supervised through the specific absorption rate (SAR). The SAR limitation can restrict the brain coverage or the minimal repetition time of fMRI experiments. In the majority of today’s studies fMRI relies on the well-known gradient-echo echo-planar imaging (GRE-EPI) sequence, which offers ultrafast acquisition. Commonly, the GRE-EPI sequence comprises two pulses: fat suppression and excitation. This work provides the means for a significant reduction in the SAR by circumventing the fat-suppression pulse. Without this fat-suppression, however, lipid signal can result in artifacts due to the chemical shift between the lipid and water signals. Our approach exploits a reconstruction similar to the simultaneous-multi-slice method to separate the lipid and water images, thus avoiding undesired lipid artifacts in brain images. The lipid-water separation is based on the known spatial shift of the lipid signal, which can be detected by the multi-channel coils sensitivity profiles. Our study shows robust human imaging, offering greater flexibility to reduce the SAR, shorten the repetition time or increase the volume coverage with substantial benefit for brain functional studies.

scholarly journals Reducing SAR in 7T brain fMRI by circumventing fat suppression while removing the lipid signal through a parallel acquisition approach

2020 ◽  
Author(s):  
Amir Seginer ◽  
Edna Furman-Haran ◽  
Ilan Goldberg ◽  
Rita Schmidt
Keyword(s):  
Fat Suppression ◽  
Planar Imaging ◽  
Brain Images ◽  
Water Separation ◽  
Parallel Acquisition ◽  
Functional Studies ◽  
Spatial Shift ◽  
Lipid Signal ◽  
Repetition Time ◽  
Echo Planar

AbstractUltra-high-field functional magnetic resonance imaging (fMRI) offers the way to new insights while increasing the spatial and temporal resolution. However, a crucial concern in 7T human MRI is the increase in power deposition, supervised through the specific absorption rate (SAR). The SAR limitation can restrict the brain coverage or the minimal repetition time of fMRI experiments. fMRI is based on the well-known gradient-echo echo-planar imaging (GRE-EPI) sequence, which offers ultrafast acquisition. Commonly, the GRE-EPI sequence comprises two pulses: fat suppression and excitation. This work provides the means for a significant reduction in the SAR by circumventing the fat-suppression pulse. Without this fat-suppression, however, lipid signal can result in artifacts due to the chemical shift between the lipid and water signals. Our approach exploits a reconstruction similar to the simultaneous-multi-slice (SMS) method to separate the lipid and water images, thus avoiding undesired lipid artifacts in brain images. The lipid-water separation is based on the known spatial shift of the lipid signal, which can be detected by the multi-channel coils sensitivity profiles. Our study shows robust human imaging, offering greater flexibility to reduce the SAR, shorten the repetition time or increase the volume coverage with substantial benefit for brain functional studies.

scholarly journals Improved fat suppression using multipeak reconstruction for IDEAL chemical shift fat-water separation: Application with fast spin echo imaging

2009 ◽  
Vol 29 (2) ◽  
pp. 436-442 ◽  
Author(s):  
Richard Kijowski ◽  
Michael A. Woods ◽  
Kenneth S. Lee ◽  
Kuya Takimi ◽  
Huanzhou Yu ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Spin Echo ◽  
Fat Suppression ◽  
Fast Spin Echo ◽  
Water Separation ◽  
Fast Spin

scholarly journals Improved temporal resolution for functional studies with reduced number of segments with three-dimensional echo planar imaging

2013 ◽  
Vol 72 (3) ◽  
pp. 786-792 ◽  
Author(s):  
Mayur Narsude ◽  
Wietske van der Zwaag ◽  
Tobias Kober ◽  
Rolf Gruetter ◽  
José P. Marques
Keyword(s):  
Temporal Resolution ◽  
Three Dimensional ◽  
Echo Planar Imaging ◽  
Planar Imaging ◽  
Functional Studies ◽  
Echo Planar ◽  
Number Of Segments

scholarly journals Robust fat suppression at 3T in high-resolution diffusion-weighted single-shot echo-planar imaging of human brain

2011 ◽  
Vol 66 (6) ◽  
pp. 1658-1665 ◽  
Author(s):  
Joelle E. Sarlls ◽  
Carlo Pierpaoli ◽  
S. Lalith Talagala ◽  
Wen-Ming Luh
Keyword(s):  
High Resolution ◽  
Human Brain ◽  
Echo Planar Imaging ◽  
Fat Suppression ◽  
Single Shot ◽  
Planar Imaging ◽  
Diffusion Weighted ◽  
Echo Planar

scholarly journals Stability of MRI radiomic features according to various imaging parameters in fast scanned T2-FLAIR for acute ischemic stroke patients

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Leehi Joo ◽  
Seung Chai Jung ◽  
Hyunna Lee ◽  
Seo Young Park ◽  
Minjae Kim ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Acute Ischemic Stroke ◽  
Correlation Coefficients ◽  
Region Of Interest ◽  
Planar Imaging ◽  
Concordance Correlation ◽  
Repetition Time ◽  
Group A ◽  
Train Length ◽  
Echo Planar

AbstractFrom May 2015 to June 2016, data on 296 patients undergoing 1.5-Tesla MRI for symptoms of acute ischemic stroke were retrospectively collected. Conventional, echo-planar imaging (EPI) and echo train length (ETL)-T2-FLAIR were simultaneously obtained in 118 patients (first group), and conventional, ETL-, and repetition time (TR)-T2-FLAIR were simultaneously obtained in 178 patients (second group). A total of 595 radiomics features were extracted from one region-of-interest (ROI) reflecting the acute and chronic ischemic hyperintensity, and concordance correlation coefficients (CCC) of the radiomics features were calculated between the fast scanned and conventional T2-FLAIR for paired patients (1st group and 2nd group). Stabilities of the radiomics features were compared with the proportions of features with a CCC higher than 0.85, which were considered to be stable in the fast scanned T2-FLAIR. EPI-T2-FLAIR showed higher proportions of stable features than ETL-T2-FLAIR, and TR-T2-FLAIR also showed higher proportions of stable features than ETL-T2-FLAIR, both in acute and chronic ischemic hyperintensities of whole- and intersection masks (p < .002). Radiomics features in fast scanned T2-FLAIR showed variable stabilities according to the sequences compared with conventional T2-FLAIR. Therefore, radiomics features may be used cautiously in applications for feature analysis as their stability and robustness can be variable.

Abstract 117: A Six Minute MRI Protocol for Evaluation of Acute Ischemic Stroke: Pushing the Boundaries

Stroke ◽  
2014 ◽  
Vol 45 (suppl_1) ◽  
Author(s):  
Kambiz Nael ◽  
Rihan Khan ◽  
Gagandeep Choudhary ◽  
Arash Meshksar ◽  
Travis Dumont ◽  
...  
Keyword(s):  
Ischemic Stroke ◽  
Acute Ischemic Stroke ◽  
Interobserver Agreement ◽  
Acquisition Time ◽  
Diagnostic Image Quality ◽  
Planar Imaging ◽  
Imaging Protocol ◽  
Parallel Acquisition ◽  
Kappa Test ◽  
Scan Time

Purpose: Multimodal cerebrovascular CT and MR can now provide information about tissue viability, site of occlusion, and collateral status in patients with acute ischemic stroke (AIS). If MRI is to compete with CT for evaluation of AIS, there is need for further improvements in acquisition speed. The purpose of this study was to establish the feasibility of a fast MR protocol with a 6 minute acquisition time for evaluation of AIS. Methods: Patients with suspicion of AIS and absence of MRI contraindications were prospectively enrolled. A combination of echo-planar imaging (EPI) and parallel acquisition technique were used on a 3T MR scanner to accelerate the acquisition time. The imaging protocol included: DWI (1 min), EPI-FLAIR (52 sec), EPI-GRE (50 sec), contrast-enhanced MR angiography (CE-MRA) of the entire supra-aortic arteries (20 sec), and DSC perfusion (2 min). Using a modified 2-phase contrast injection scheme, high spatial resolution CE-MRA of the supra-aortic arteries was performed just before DSC perfusion without the need for additional contrast. Image analysis was performed independently by two neuroradiologists and interobserver agreement was calculated using Kappa test. Results: A total of 50 patients were included. Diagnostic image quality was achieved in 100% of DWI, 96% EPI-FLAIR, 98% EPI-GRE, 90% neck MRA, 96% of brain MRA, and 94% of DSC perfusion scans. Thirty eight patients (76%) had acute infarction. Using Tmax perfusion maps and applying DEFUSE criteria, 42% of patients had perfusion-diffusion mismatch with interobserver agreement of k=0.90. The mean of the signal-intensity-ratio values of the infarction on EPI-FLAIR was 1.08 for patients presenting < 4.5 hours (n=16) and 1.35 for patients presenting > 4.5 hours (n=22) from the time of imaging. Three patients had evidence of intracranial hemorrhage detected on EPI-GRE and confirmed by non-contrast CT. CE-MRA showed 27 segmental stenoses of the extra-cranial arteries and 24 segmental stenoses of the intracranial arteries with interobserver agreement of k= 0.82 and 0.74 respectively. Conclusion: Described multimodal MR protocol is feasible for evaluation of patients with AIS and can result in significant reduction in scan time rivaling that of the multimodal CT protocol.

Time-Resolved fMRI of Activation Patterns in M1 and SMA During Complex Voluntary Movement

2001 ◽  
Vol 85 (5) ◽  
pp. 1858-1863 ◽  
Author(s):  
Florian Weilke ◽  
Sabine Spiegel ◽  
Henning Boecker ◽  
Helga Gräfin von Einsiedel ◽  
Bastian Conrad ◽  
...  
Keyword(s):  
Time Course ◽  
Primary Motor Cortex ◽  
Planar Imaging ◽  
Hemodynamic Response Function ◽  
Time Resolved ◽  
Activation Patterns ◽  
Signal Change ◽  
Repetition Time ◽  
Report Data ◽  
Echo Planar

The aim of this study was to use time-resolved functional magnetic resonance imaging (fMRI) to investigate temporal differences in the activation of the supplementary motor area (SMA) and the primary motor cortex (M1). We report data from eight human volunteers who underwent fMRI examinations in a 1.5T Philips Gyroscan ACS-NT MRI scanner. While wearing a contact glove, subjects executed a complex automated sequence of finger movements either spontaneously or in response to external auditory cues. Based on the result of a functional scout scan, a single slice that included the M1 and the SMA was selected for image acquisition (echo planar imaging, repetition time 100 ms, echo time 50 ms, 64 × 64 matrix, 1,000 images). Data were analyzed with a shifting cross-correlation approach using the STIMULATE program and in-house programs written in Interactive Data Language (IDL™). Time-course data were generated for regions of interest in the M1 as well as in the rostral and caudal SMA. Mean time between onset of the finger movement sequence and half-maximum of the signal change in M1 was 3.6 s for the externally cued execution (SD 0.5) and 3.5 s for the spontaneous execution (SD 0.6). Activation in the rostral section of the SMA occurred 0.7 s earlier than it did in the M1 during the externally cued execution and 2.0 s earlier during the spontaneous execution, a difference significant at the P < 0.01 level. Our results indicate that rostral SMA activation precedes M1 activation by varying time intervals in the sub-second range that are determined by the mode of movement initialization. By applying a paradigm that exerts a differential influence on temporal activation, we could ensure that the observed timing differences were not the result of differences in hemodynamic response function.

Sign in / Sign up

Export Citation Format

Share Document