Alterations of the proton‐T<sub>2</sub> time in relaxed skeletal muscle induced by passive extremity flexions

Rump, Jens; Braun, Jürgen; Papazoglou, Sebastian; Taupitz, Matthias; Sack, Ingolf

doi:10.1002/jmri.20534

Cited by 7 publications

(9 citation statements)

References 35 publications

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“…The subjects were instructed to lie passively ( i.e ., not contract the muscles) during the procedure. In each leg orientation, the foot angle was 90 ° to avoid T 2 changes related to sarcomere overlap (29). In each position, the subjects were studied with and without proximal arterial occlusion.…”

Section: Methodsmentioning

confidence: 99%

Absence of a significant extravascular contribution to the skeletal muscle BOLD effect at 3 T

Sánchez

Copenhaver

Elder

et al. 2010

Magnetic Resonance in Med

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Blood oxygenation level dependent (BOLD) contrast in skeletal may reflect the contributions of both intravascular and extravascular relaxation effects. The purpose of this study was to determine the significance of the extravascular BOLD effect in skeletal muscle at 3 T. In experiments, R 2 * was measured before and during arterial occlusion under the following conditions: (1) the leg extended and rotated (to vary the capillary orientation with respect to the amplitude of static field) and (2) with the blood's signal nulled using a multiecho vascular space occupancy experiment. In the leg rotation protocol, 3 min of arterial occlusion decreased oxyhemoglobin saturation from 67% to 45% and increased R 2 * from 34.2 to 36.6 sec 21 , but there was no difference in the R 2 * response to occlusion between the extended and rotated positions. Numerical simulations of intra-and extravascular BOLD effects corresponding to these conditions predicted that the intravascular BOLD contribution to the R 2 * change was always > 50 times larger than the extravascular BOLD contribution. Blood signal nulling eliminated the change in R 2 * caused by arterial occlusion. These data indicate that under these experimental conditions, the contribution of the extravascular BOLD effect to skeletal muscle R 2 * was too small to be practically important. Magn Reson Med 64:527-535, 2010. V C 2010 WileyLiss, Inc.Key words: mfMRI; extravascular BOLD effect; oxygenation; vessel orientation; VASO Variations in the rates of permanent and effective transverse relaxation (R 2 and R 2 *, respectively) or in T 2 -weighted signal may be used to evaluate the hemodynamic, metabolic, and structural changes associated with muscle contractions (1), an approach known as muscle functional MRI (2). During and following muscle contractions, changes in muscle R 2 and R 2 * result from increases in intracellular water content, secondary to metabolite accumulation (3,4); variations in intracellular pH (4-6); and changes in the concentrations of paramagnetic molecules such as deoxyhemoglobin, as reflected in the blood oxygenation level dependent (BOLD) effect (7,8). The magnitude of each of these changes and thus the variations in R 2 and R 2 * depend on the exercise and intensity (9), the muscle fiber type composition (3), and whole-body aerobic capacity (10). Since these factors affect R 2 and R 2 * to different degrees, quantifying the independent contributions of and interactions among these factors is important to interpret physiologic and pathologic variations in muscle R 2 and R 2 *.Regarding the source of oxygen-level dependent contrast in skeletal muscle, it is noteworthy that skeletal muscle cells themselves contain several potential magnetic field perturbers that may also contribute to susceptibility-related signal decay in skeletal muscle. However, both theoretical calculations and experimental observations suggest that a true BOLD effect, and not a muscle oxygenation level dependent effect, occurs in skeletal muscle (8). The presence of a muscle BOLD ...

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Section: Methodsmentioning

confidence: 99%

Absence of a significant extravascular contribution to the skeletal muscle BOLD effect at 3 T

Sánchez

Copenhaver

Elder

et al. 2010

Magnetic Resonance in Med

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“…Rump et al (27) measured changes in T2 relaxation time because of passive muscle shortening in the upper arm due to elbow flexion/ extension (908). He observed an increase in the proton-T2 time that was correlated with a passive contraction of the muscle.…”

Section: Discussionmentioning

confidence: 99%

Diffusion tensor imaging of the human calf muscle: distinct changes in fractional anisotropy and mean diffusion due to passive muscle shortening and stretching

Schwenzer¹,

Steidle²,

Martirosian³

et al. 2009

NMR in Biomedicine

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aThe influence of passive shortening and stretching of the calf muscles on diffusion characteristics was investigated. The diffusion tensor was measured in transverse slices through the lower leg of eight healthy volunteers (29 W 7 years) on a 3 T whole-body MR unit in three different positions of the foot (40-plantarflexion, neutral ankle position (0-), and S10-dorsiflexion in the ankle). Maps of the mean diffusivity, the three eigenvalues of the tensor and fractional anisotropy (FA) were calculated. Results revealed a distinct dependence of the mean diffusivity and FA on the foot position and the related shortening and stretching of the muscle groups. The tibialis anterior muscle showed a significant increase of 19% in FA with increasing dorsiflexion, while the FA of the antagonists significantly decreased ($20%). Regarding the mean diffusivity of the diffusion tensor, the muscle groups showed an opposed response to muscle elongation and shortening. Regarding the eigenvalues of the diffusion tensor, l 2 and l 3 showed significant changes in relation to muscle length. In contrast, no change in l 1 could be found. This work reveals significant changes in diffusional characteristics induced by passive muscle shortening and stretching.

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“…[18]. The solution in real space is finally obtained by inverse Fourier transform in three dimensions: [ 19] This solution corresponds to a transient excitation at the origin of the coordinate system at time t ϭ 0. The response to a harmonic steady-state excitation can now be obtained by convoluting Eq.…”

Section: Appendix Bmentioning

confidence: 99%

“…The response to a harmonic steady-state excitation can now be obtained by convoluting Eq. [19] with a harmonic source.…”

Section: Appendix Bmentioning

confidence: 99%

“…Extensive research in the field of muscle activity measurements by MRI underscore the important role of muscle MR in neurophysiologic research, diagnosis, and therapy (15)(16)(17)(18)(19). Muscle MRE (11,20 -24) is developing into a straightforward technique for detecting several diseases that affect muscle elasticity, such as hypogonadism (25) and obstructive pulmonary disease (26).…”

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confidence: 99%

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Shear wave group velocity inversion in MR elastography of human skeletal muscle

Papazoglou

Rump

Braun

et al. 2006

Magnetic Resonance in Med

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107

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In vivo quantification of the anisotropic shear elasticity of soft tissue is an appealing objective of elastography techniques because elastic anisotropy can potentially provide specific information about structural alterations in diseased tissue. Here a method is introduced and applied to MR elastography (MRE) of skeletal muscle. With this method one can elucidate anisotropy by means of two shear moduli (one parallel and one perpendicular to the muscle fiber direction). The technique is based on group velocity inversion applied to bulk shear waves, which is achieved by an automatic analysis of wave-phase gradients on a spatiotemporal scale. The shear moduli are then accessed by analyzing the directional dependence of the shear wave speed using analytic expressions of group velocities in k-space, which are numerically mapped to real space. The method is demonstrated by MRE experiments on the biceps muscle of five volunteers, resulting in 5.5 ؎ 0.9 kPa and 29.3 ؎ 6.2 kPa (P < 0.05) for the medians of the perpendicular and parallel shear moduli, respectively. The proposed technique combines fast steadystate free precession (SSFP) MRE experiments and fully automated processing of anisotropic wave data, and is thus an interesting MRI modality for aiding clinical diagnosis. Magn Reson Med 56:489 -497, 2006.

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Alterations of the proton‐T₂ time in relaxed skeletal muscle induced by passive extremity flexions

Cited by 7 publications

References 35 publications

Absence of a significant extravascular contribution to the skeletal muscle BOLD effect at 3 T

Absence of a significant extravascular contribution to the skeletal muscle BOLD effect at 3 T

Diffusion tensor imaging of the human calf muscle: distinct changes in fractional anisotropy and mean diffusion due to passive muscle shortening and stretching

Shear wave group velocity inversion in MR elastography of human skeletal muscle

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Alterations of the proton‐T2 time in relaxed skeletal muscle induced by passive extremity flexions

Cited by 7 publications

References 35 publications

Absence of a significant extravascular contribution to the skeletal muscle BOLD effect at 3 T

Absence of a significant extravascular contribution to the skeletal muscle BOLD effect at 3 T

Diffusion tensor imaging of the human calf muscle: distinct changes in fractional anisotropy and mean diffusion due to passive muscle shortening and stretching

Shear wave group velocity inversion in MR elastography of human skeletal muscle

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Product

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Alterations of the proton‐T₂ time in relaxed skeletal muscle induced by passive extremity flexions