Spin‐echo and gradient‐echo epi of human brain activation using bold contrast: A comparative study at 1.5 T

Pa, Bandettini; Ec, Wong; Jeśmanowicz, A; Hinks, R. Scott; Js, Hyde

doi:10.1002/nbm.1940070104

Cited by 304 publications

(232 citation statements)

References 28 publications

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“…Designing appropriate interleaved SLEPI-EPI experiments may differentiate the relative contributions to the BOLD effect from blood flow and saturation changes in the arterial, capillary, and venous pools. As development of this pulse sequence continues, it will be of interest to compare the SLEPI sequence to a spin-echo-based EPI sequence (19), in order to compare artifact reduction and contrast in different tissues in the brain.…”

Section: Discussionmentioning

confidence: 99%

A pulse sequence for rapid in vivo spin‐locked MRI

Borthakur

Hulvershorn

Gualtieri

et al. 2006

Magnetic Resonance Imaging

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Purpose: To develop a novel pulse sequence called spinlocked echo planar imaging (EPI), or (SLEPI), to perform rapid T 1 -weighted MRI. Materials and Methods:SLEPI images were used to calculate T 1 maps in two healthy volunteers imaged on a 1.5-T Sonata Siemens MRI scanner. The head and extremity coils were used for imaging the brain and blood in the popliteal artery, respectively.Results: SLEPI-measured T 1 was 83 msec and 103 msec in white (WM) and gray matter (GM), respectively, 584 msec in cerebrospinal fluid (CSF), and was similar to values obtained with the less time-efficient sequence based on a turbo spin-echo readout. T 1 was 183 msec in arterial blood at a spin-lock (SL) amplitude of 500 Hz. Conclusion:We demonstrate the feasibility of the SLEPI pulse sequence to perform rapid T 1 MRI. The sequence produced images of higher quality than a gradient-echo EPI sequence for the same contrast evolution times. We also discuss applications and limitations of the pulse sequence. T 1⌹ OR "SPIN-LOCKED" MRI produces contrast unlike conventional T 1 -or T 2 -weighted images. Spin-locking is achieved by the application of a low power on-resonance radiofrequency (RF) pulse to the magnetization in the transverse plane. The resulting MR signal decays with a time constant T 1 and is dominated by processes that occur with a correlation time, c , that is related to the amplitude of the spin-lock (SL) pulse (␥B 1 /2 ), which typically ranges from zero to a few kilohertz. T 1 is commonly referred to as the longitudinal relaxation time constant in the rotating frame. In biological tissues, T 1 increases with higher B 1 and approaches T 2 , the spin-spin relaxation time constant, as the amplitude of the SL pulse is reduced to zero. The sensitivity of T 1 to low-frequency interactions facilitates the study of biological tissues in a manner that is unattainable by conventional T 1 -and T 2 -based MR methods. Consequently, T 1 MRI has been used to investigate a variety of tissues such as breast, brain, and cartilage (1-3).Recently, T 1 imaging has been employed to measure blood flow and oxygen metabolism and the effect of tracers such as H 2 17 O (4,5). These studies were performed using standard spin-echo, turbo (fast) spinecho, or gradient-echo-based pulse sequences. There is substantial evidence demonstrating that the T 1 relaxation time parameter is sensitive to the early detection of cerebral ischemia (6 -8). Kettunen et al (9) revealed a linear dependence of T 1 as a function of oxygen saturation in experiments performed in vitro. Dynamic studies such as these and others that involve imaging of flowing spins such as that of blood would benefit from a fast T 1 imaging technique that is able to acquire images in the order of tens of milliseconds.A method of rapid image acquisition is the echo planar imaging (EPI) technique (10,11). In its conventional form, the EPI pulse sequence consists of an excitation pulse that is followed by a train of gradientechoes within a single pulse repetition time (TR), and is capable of generat...

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Section: Discussionmentioning

confidence: 99%

A pulse sequence for rapid in vivo spin‐locked MRI

Borthakur

Hulvershorn

Gualtieri

et al. 2006

Magnetic Resonance Imaging

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“…The use of SE-EPI requires a TE which is roughly equal to the T 2 of the tissue being examined (Bandettini et al, 1994), whereas for GE-EPI the optimum TE is T* 2 . This reduces the number of slices per unit time that can be acquired: for our system and the imaging parameters used in this study the reduction is from 14 to 10 slices per second.…”

Section: Discussionmentioning

confidence: 99%

“…The quality of functional contrast obtained with T 2 -weighted imaging differs from that of T* 2 -weighted images in that all contributions from static dephasing are eliminated. This considerably reduces the magnitude of the signal change that can be obtained, and for this reason T 2 -weighted BOLD imaging has to date found limited use, being confined to functional studies of the primary cortices (Bandettini et al, 1994;Constable et al, 1994;Thulborn et al, 1997;Jones et al, 1998;Jones, 1999;Oja et al, 1999;Lee et al, 1999;Lowe et al, 2000) or to signal changes resulting from physiological stress (Prinster et al, 1997;van Zijl et al, 1998;Kavec et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

An Investigation of the Value of Spin-Echo-Based fMRI Using a Stroop Color–Word Matching Task and EPI at 3 T

et al. 2002

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This study examines the value of spin-echo-based fMRI for cognitive studies at the main magnetic field strength of 3 T using a spin-echo EPI (SE-EPI) sequence and a Stroop color-word matching task. SE-EPI has the potential advantage over conventional gradient-echo EPI (GE-EPI) that signal losses caused by dephasing through the slice are not present, and hence although image distortion will be the same as for an equivalent GE-EPI sequence, signal voids will be eliminated. The functional contrast in SE-EPI will be lower than for GE-EPI, as static dephasing effects do not contribute. As an auxiliary experiment interleaved diffusion-weighted and non-diffusion-weighted SE-EPI was performed in the visual cortex to further elucidate the mechanims of functional contrast. In the Stroop experiment activation was detected in all areas previously found using GE-EPI. Additional frontopolar and ventral frontomedian activations were also found, which could not be detected using GE-EPI. The experiments from visual cortex indicated that at 3 T the BOLD signal change has contributions from the extravascular space and larger blood vessels in roughly equal amounts. In comparison with GE-EPI the absence of static dephasing effects would seem to result in a superior intrinsic spatial resolution. In conclusion the sensitivity of SE-EPI at 3 T is sufficient to make it the method of choice for fMR studies that require a high degree of spatial localization or where the requirement is to detect activation in regions affected by strong susceptibility gradients. © 2002 Elsevier Science (USA)

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“…At 3 T, the GRE-BOLD response is known to correspond to a mixture of signals arising from both the capillary parenchyma in the gray matter as well as larger vessels and sinuses outside the brain (Bandettini et al, 1994;Boxerman et al, 1995;Menon et al, 1995;Ogawa et al, 1998). Human experiments offer various appraisals of whether GRE-BOLD measures local signals.…”

Section: Introductionmentioning

confidence: 99%

Laminar profiles of functional activity in the human brain

Ress¹,

Glover²,

Liu³

et al. 2007

NeuroImage

127

109

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Functional magnetic resonance imaging (fMRI) data were obtained in human visual cortex using sub-millimeter voxels at a field strength of 3 T. Reliable functional signals were largely confined to the gray matter and these responses measure the retinotopic organization of visual cortex. Functional signals were further characterized with respect to their laminar position within the cortical gray matter. The laminar response profiles during our visuospatial attention task, normalized for cortical thickness, had a stereotypical shape, with a peak in the superficial gray matter and declining in the deeper layers. The thickness of the sheet producing functional signals was in excellent agreement with the estimated structural thickness of the gray matter throughout early visual cortex (error <0.5 mm). Thickness measurements were highly repeatable from session-to-session (error <0.4 mm). Hence, it is feasible and useful to use high-resolution fMRI to measure laminar activity profiles. The ability to distinguish signals arising in different lamina has significant potential scientific and clinical applications.

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Spin‐echo and gradient‐echo epi of human brain activation using bold contrast: A comparative study at 1.5 T

Cited by 304 publications

References 28 publications

A pulse sequence for rapid in vivo spin‐locked MRI

A pulse sequence for rapid in vivo spin‐locked MRI

An Investigation of the Value of Spin-Echo-Based fMRI Using a Stroop Color–Word Matching Task and EPI at 3 T

Laminar profiles of functional activity in the human brain

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