T1ρ MRI contrast in the human brain: Modulation of the longitudinal rotating frame relaxation shutter-speed during an adiabatic RF pulse

Michaeli, Shalom; Sorce, Dennis J.; Springer, Charles S.; Uğurbil, Kâmil; Garwood, Michael

doi:10.1016/j.jmr.2006.04.002

Cited by 84 publications

(139 citation statements)

References 35 publications

(65 reference statements)

Supporting

Mentioning

133

Contrasting

Order By: Relevance

“…Because a given bandwidth can be excited in many different ways, HSn pulses offer a flexible tool for interrogating spin systems. For example, in a manner similar to that recently demonstrated using AFP pulses [18,19], it may be possible to alter image contrast by collecting images with different pulse parameters.…”

Section: Discussionmentioning

confidence: 99%

“…The entire excitation spectrum is weighted by the envelope function, . The Nyquist condition for a discretized excitation determines that the sidebands are not aliased when (18) This in turn determines the minimum number of pulse elements needed to satisfy the Nyquist condition, N Nyquist , which depends on R according to: (19) If the number of pulse elements satisfies the Nyquist condition, then the baseband (-b w / 2≤ν≤b w /2) can be described by (20) To reduce the attenuation by sinc (νΔt the length of Δt can be decreased (i.e. the pulse can be oversampled).…”

Section: Generating Shaped Pulsesmentioning

confidence: 99%

“…For the same pulse length and duty cycle, the gapped pulse shows better behavior (flatter excitation profile) up to the maximum usable R value, which is R = N seg (Eq. [19]). For this reason, only gapped pulses are considered here.…”

Section: Time Shared Acquisition In Gapped Hsn Pulsesmentioning

confidence: 99%

See 2 more Smart Citations

Gapped pulses for frequency-swept MRI

Idiyatullin

Corum

Moeller

et al. 2008

Journal of Magnetic Resonance

Self Cite

View full text Add to dashboard Cite

A recently introduced method called SWIFT (SWeep Imaging with Fourier Transform) is a fundamentally different approach to MRI which is particularly well suited to imaging objects with extremely fast spin-spin relaxation rates. The method exploits a frequency-swept excitation pulse and virtually simultaneous signal acquisition in a time-shared mode. Correlation of the spin system response with the excitation pulse function is used to extract the signals of interest. With SWIFT, image quality is highly dependent on producing uniform and broadband spin excitation. These requirements are satisfied by using frequency-modulated pulses belonging to the hyperbolic secant family (HSn pulses). This article describes the experimental steps needed to properly implement HSn pulses in SWIFT. In addition, properties of HSn pulses in the rapid passage, linear region are investigated, followed by an analysis of the pulses after inserting the "gaps" needed for time-shared excitation and acquisition. Finally, compact expressions are presented to estimate the amplitude and flip angle of the HSn pulses, as well as the relative energy deposited by the SWIFT sequence.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Generating Shaped Pulsesmentioning

confidence: 99%

See 1 more Smart Citation

Gapped pulses for frequency-swept MRI

Idiyatullin

Corum

Moeller

et al. 2008

Journal of Magnetic Resonance

Self Cite

View full text Add to dashboard Cite

show abstract

“…Subsequently, adiabatic T1ρ relaxation time[23, 25] of the specimens was measured in a single axial slice covering the operated area as determined from 3-D gradient recalled echo images. The relaxation time was measured using a magnetization preparation block consisting of 0, 4, 8, 12 and 16 adiabatic full passage pulses from the hyperbolic secant family[18] of 6 ms duration at peak power γB 1,max = 2.5 kHz coupled to a fast spin echo readout sequence[23, 25]. Slice thickness was 1 mm with imaging matrix of 256 x 256; echo train length was 8; echo spacing was set to minimum (~5 ms) and a repetition time of 5 s was used.…”

Section: Methodsmentioning

confidence: 99%

Surgical induction, histological evaluation, and MRI identification of cartilage necrosis in the distal femur in goats to model early lesions of osteochondrosis

Tóth

Nissi

Wang

et al. 2015

Osteoarthritis and Cartilage

View full text Add to dashboard Cite

Objective Identify and interrupt the vascular supply to portions of the distal femoral articularepiphyseal cartilage complex (AECC) in goat kids to induce cartilage necrosis, characteristic of early lesions of osteochondrosis; then utilize MRI to identify necrotic areas of cartilage. Design Distal femora were perfused and cleared in goat kids of various ages to visualize the vascular supply to the distal femoral AECC. Vessels located on the axial aspect of the medial femoral condyle and on the abaxial side of the lateral trochlear ridge were transected in eight 4-day-old goats to induce cartilage necrosis. Goats were euthanized 1, 2, 3, 4, 5, 6, 9, and 10 weeks post operatively and operated stifles were harvested. Adiabatic T1ρ relaxation time maps of the harvested distal femora were generated using a 9.4T MR scanner, after which samples were evaluated histologically. Results Interruption of the vascular supply to the medial femoral condyle caused lesions of cartilage necrosis in 6/8 goat kids that were demonstrated histologically. Adiabatic T1ρ relaxation time mapping identified these areas of cartilage necrosis in 5/6 cases. No significant findings were detected after transection of perichondrial vessels supplying the lateral trochlear ridge. Conclusions Cartilage necrosis, characteristic of early osteochondrosis, can be induced by interrupting the vascular supply to the distal femoral AECC in goat kids. The ability of high field MRI to identify these areas of cartilage necrosis in the AECC using the adiabatic T1ρ sequence suggests that this technique may be useful in the future for the early diagnosis of osteochondrosis.

show abstract

“…In the presence of radiofrequency irradiation, relaxation of magnetization aligned with the effective magnetic field is characterized by the time constant T 1rho , whereas relaxation of magnetization perpendicular to the effective magnetic field is characterized by T 2rho . It has been shown that T 1rho is sensitive to dipolar interactions of brain water in different environments, i.e., between water attached to macromolecules and bulk water, 40 whereas T 2rho is sensitive to water chemical exchange. 41 Since the radiofrequency irradiation can be manipulated, T 1rho and T 2rho can be used to selectively tune the image contrast over a certain range to different molecular mechanisms.…”

Section: Rotating Frame Imagingmentioning

confidence: 99%

Potential role of high‐field MRI for studies in Parkinson's disease

Schuff

2009

Movement Disorders

View full text Add to dashboard Cite

Recent advancements in high field magnetic resonance imaging (MRI) technology (3 T and higher), providing increased signal sensitivity and images with more prominent contrasts intrinsic to the brain, offer new opportunities for assessing brain alterations in Parkinson's disease (PD). In this article, the principle benefits of high field MRI for PD research are described and new findings at high magnetic fields are reviewed. Several high field MRI methodologies, including structural MRI, imaging of brain iron, diffusion tensor imaging, arterial spin labeling perfusion imaging, rotating frame imaging, and magnetic resonance spectroscopy, are critically reviewed for their potential roles in studies of PD.

show abstract

T1ρ MRI contrast in the human brain: Modulation of the longitudinal rotating frame relaxation shutter-speed during an adiabatic RF pulse

Cited by 84 publications

References 35 publications

Gapped pulses for frequency-swept MRI

Gapped pulses for frequency-swept MRI

Surgical induction, histological evaluation, and MRI identification of cartilage necrosis in the distal femur in goats to model early lesions of osteochondrosis

Potential role of high‐field MRI for studies in Parkinson's disease

Contact Info

Product

Resources

About