Spatial location and strength of BOLD activation in high-spatial-resolution fMRI of the motor cortex: a comparison of spin echo and gradient echo fMRI at 7 T

2011 ◽  
Vol 25 (5) ◽  
pp. 717-725 ◽  
Author(s):  
J. Harmer ◽  
R. M. Sanchez-Panchuelo ◽  
R. Bowtell ◽  
S. T. Francis
Keyword(s):  
Motor Cortex ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Spin Echo ◽  
Spatial Location ◽  
Gradient Echo

Increased-Contrast, High-Spatial-Resolution, Diffusion-weighted, Spin-Echo, Echo-planar Imaging

Radiology ◽  
1999 ◽  
Vol 210 (1) ◽  
pp. 253-259 ◽  
Author(s):  
Michael R. Thompson ◽  
Ramesh Venkatesan ◽  
Karthik Kuppusamy ◽  
Azim Celik ◽  
Weili Lin ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Spin Echo ◽  
Echo Planar Imaging ◽  
Planar Imaging ◽  
Diffusion Weighted ◽  
Echo Planar

High spatial resolution BOLD fMRI using simultaneous multislice excitation with echo-shifting gradient echo at 7 Tesla

2020 ◽  
Vol 66 ◽  
pp. 86-92 ◽  
Author(s):  
Shi Su ◽  
Na Lu ◽  
Lin Jia ◽  
Xiaojing Long ◽  
Chunxiang Jiang ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Gradient Echo ◽  
Bold Fmri ◽  
Simultaneous Multislice

scholarly journals A more accurate account of the effect of k-space sampling and signal decay on the effective spatial resolution in functional MRI

2016 ◽  
Author(s):  
Denis Chaimow ◽  
Amir Shmuel
Keyword(s):  
High Resolution ◽  
Functional Mri ◽  
Spatial Resolution ◽  
Spin Echo ◽  
7 Tesla ◽  
Gradient Echo ◽  
Magnitude Image ◽  
Signal Decay ◽  
The Absolute ◽  
High Pass

AbstractThe effects of k-space sampling and signal decay on the effective spatial resolution of MRI and functional MRI (fMRI) are commonly assessed by means of the magnitude point-spread function (PSF), defined as the absolute values (magnitudes) of the complex MR imaging PSF. It is commonly assumed that this magnitude PSF signifies blurring, which can be quantified by its full-width at half-maximum (FWHM). Here we show that the magnitude PSF fails to accurately represent the true effects of k-space sampling and signal decay.Firstly, a substantial part of the width of the magnitude PSF is due to MRI sampling per se. This part is independent of any signal decay and its effect depends on the spatial frequency composition of the imaged object. Therefore, it cannot always be expected to introduce blurring. Secondly, MRI reconstruction is typically followed by taking the absolute values (magnitude image) of the reconstructed complex image. This introduces a non-linear stage into the process of image formation. The complex imaging PSF does not fully describe this process, since it does not reflect the stage of taking the magnitude image. Its corresponding magnitude PSF fails to correctly describe this process, since convolving the original pattern with the magnitude PSF is different from the true process of taking the absolute following a convolution with the complex imaging PSF. Lastly, signal decay can have not only a blurring, but also a high-pass filtering effect. This cannot be reflected by the strictly positive width of the magnitude PSF.As an alternative, we propose to first approximate the MRI process linearly. We then model the linear approximation by decomposing it into a signal decay-independent MR sampling part and an approximation of the signal decay effect. We approximate the latter as a convolution with a Gaussian PSF or, if the effect is that of high-pass filtering, as reversing the effect of a convolution with a Gaussian PSF. We show that for typical high-resolution fMRI at 7 Tesla, signal decay in Spin-Echo has a moderate blurring effect (FWHM = 0.89 voxels, corresponds to 0.44 mm for 0.5 mm wide voxels). In contrast, Gradient-Echo acts as a moderate high-pass filter that can be interpreted as reversing a Gaussian blurring with FWHM = 0.59 voxels (0.30 mm for 0.5 mm wide voxels). Our improved approximations and findings hold not only for Gradient-Echo and Spin-Echo fMRI but also for GRASE and VASO fMRI. Our findings support the correct planning, interpretation, and modeling of high-resolution fMRI.

scholarly journals Quantifying the spatial resolution of the gradient echo and spin echo BOLD response at 3 Tesla

2005 ◽  
Vol 54 (6) ◽  
pp. 1465-1472 ◽  
Author(s):  
Laura M. Parkes ◽  
Jens V. Schwarzbach ◽  
Annemieke A. Bouts ◽  
Roel h R. Deckers ◽  
Pim Pullens ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Spin Echo ◽  
3 Tesla ◽  
Bold Response ◽  
Gradient Echo

Imaging Brain Metabolism in the Newborn

2018 ◽  
Vol 33 (13) ◽  
pp. 851-860 ◽  
Author(s):  
Harry T. Chugani
Keyword(s):  
Basal Ganglia ◽  
Motor Cortex ◽  
Brain Stem ◽  
Spatial Resolution ◽  
Neonatal Intensive Care ◽  
Glucose Utilization ◽  
High Spatial Resolution ◽  
Sensitive Period ◽  
Temporal Region ◽  
Positron Emission

In this review, we discuss molecular brain imaging studies using positron emission tomography (PET) with 2-deoxy-2(18F)fluoro-d-glucose (FDG) in human newborns and infants, and illustrate how this technology can be applied to probe the neuropathophysiology of neonatal neurologic disorders. PET studies have been difficult to perform in sick babies because of patient transportation issues and suboptimal spatial resolution. With approval from the FDA and the institutional review board, we modified and installed the Focus 220 animal microPET scanner (Concorde Microsystems, Knoxville, TN) directly in our neonatal intensive care unit in Children’s Hospital of Michigan and verified the high spatial resolution (<2 mm full-width-at-half-maximum) of this microPET. The neonatal pattern of glucose metabolism is very consistent, with the highest degree of activity in primary sensory and motor cortex, medial temporal region, thalamus, brain stem, and cerebellar vermis. Prior studies have shown that increases of glucose utilization are seen by 2 to 3 months in the parietal, temporal, cingulate, and primary visual cortex; basal ganglia; and cerebellar hemispheres. Between 6 and 8 months, lateral and inferior frontal cortex becomes more functionally active and, eventually, between 8 and 12 months, the dorsal and medial frontal regions also show a maturational increase. These findings are consistent with the physical, behavioral, and cognitive maturation of the infant. At birth, metabolic rates of glucose utilization in cortex are about 30% lower than in adults but rapidly rise such that, by 3 years, the cerebral cortical rates exceed adult rates by more than 2-fold. At around puberty, the rates for cerebral cortex begin to decline and gradually reach adult values by 16-18 years. These nonlinear changes of glucose utilization indirectly reflect programed periods of synaptic proliferation and pruning in the brain. Positron emission tomographic (PET) imaging of GABAA receptors (using 11C-flumazenil) in newborns also show a pattern very different from adults, with high binding in amygdala-hippocampus, sensory-motor cortex, thalamus, brain stem, and basal ganglia, in that order. We speculate that the early development of amygdala/hippocampus prepares the baby for bonding, attachment, and memory, and the deprivation of such experiences during a sensitive period results in malfunction of these networks and psychopathology, as has been shown in studies on severely socioemotionally deprived children. Recently developed hybrid PET/magnetic resonance (MR) scanners allow the simultaneous acquisition of PET and MR data sets with advanced applications. These devices are particularly advantageous for scanning babies and infants because of the high spatial resolution, automated coregistration of anatomical and functional images and, in the case of need for sedation, maximal data acquired in 1 session.

scholarly journals “Tumoral Pseudoblush” Identified within Gliomas at High-Spatial-Resolution Ultrahigh-Field-Strength Gradient-Echo MR Imaging Corresponds to Microvascularity at Stereotactic Biopsy

Radiology ◽  
2012 ◽  
Vol 264 (1) ◽  
pp. 210-217 ◽  
Author(s):  
Gregory A. Christoforidis ◽  
Ming Yang ◽  
Amir Abduljalil ◽  
Abhik R. Chaudhury ◽  
Herbert B. Newton ◽  
...  
Keyword(s):  
Mr Imaging ◽  
Field Strength ◽  
Spatial Resolution ◽  
Stereotactic Biopsy ◽  
High Spatial Resolution ◽  
Gradient Echo ◽  
Ultrahigh Field ◽  
Strength Gradient

High spatial resolution AEM observations of yttrium segregation in chromia scales grown on Co-45%Cr

1986 ◽  
Vol 44 ◽  
pp. 518-519
Author(s):  
K. Przybylski ◽  
A. J. Garratt-Reed ◽  
G. J. Yurek
Keyword(s):  
Spatial Resolution ◽  
Outer Surface ◽  
Maximum Concentration ◽  
High Spatial Resolution ◽  
Reactive Elements ◽  
Chromia Scales

The addition of so-called “reactive” elements such as yttrium to alloys is known to enhance the protective nature of Cr2O3 or Al2O3 scales. However, the mechanism by which this enhancement is achieved remains unclear. An A.E.M. study has been performed of scales grown at 1000°C for 25 hr. in pure O2 on Co-45%Cr implanted at 70 keV with 2x1016 atoms/cm2 of yttrium. In the unoxidized alloys it was calculated that the maximum concentration of Y was 13.9 wt% at a depth of about 17 nm. SIMS results showed that in the scale the yttrium remained near the outer surface.

Integration of Core-Edge Spectroscopy Methods for the Study of Polymers

1996 ◽  
Vol 54 ◽  
pp. 154-155
Author(s):  
E. G. Rightor
Keyword(s):  
Excited State ◽  
Polymer Blends ◽  
Gas Phase ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Electronic States ◽  
Core Electron ◽  
Bulk Solids ◽  
Development Application

Core edge spectroscopy methods are versatile tools for investigating a wide variety of materials. They can be used to probe the electronic states of materials in bulk solids, on surfaces, or in the gas phase. This family of methods involves promoting an inner shell (core) electron to an excited state and recording either the primary excitation or secondary decay of the excited state. The techniques are complimentary and have different strengths and limitations for studying challenging aspects of materials. The need to identify components in polymers or polymer blends at high spatial resolution has driven development, application, and integration of results from several of these methods.

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