In vivo observation of quadrupolar splitting in ³⁹K magnetic resonance spectroscopy of human muscle tissue

Abstract

The purpose of this work was to explore the origin of oscillations of the T(*)2 decay curve of (39)K observed in studies of (39)K magnetic resonance imaging of the human thigh. In addition to their magnetic dipole moment, spin-3/2 nuclei possess an electric quadrupole moment. Its interaction with non-vanishing electrical field gradients leads to oscillations in the free induction decay and to splitting of the resonance. All measurements were performed on a 7T whole-body MRI scanner (MAGNETOM 7T, Siemens AG, Erlangen, Germany) with customer-built coils. According to the theory of quadrupolar splitting, a model with three Lorentzian-shaped peaks is appropriate for (39)K NMR spectra of the thigh and calf. The frequency shifts of the satellites depend on the angle between the calf and the static magnetic field. When the leg is oriented parallel to the static magnetic field, the satellites are shifted by about 200 Hz. In the thigh, rank-2 double quantum coherences arising from anisotropic quadrupolar interaction are observed by double-quantum filtration with magic-angle excitation. In addition to the spectra, an image of the thigh with a nominal resolution of (16 × 16 × 32) mm(3) was acquired with this filtering technique in 1:17 h. From the line width of the resonances, (39)K transverse relaxation time constants T(*)2, fast = (0.51 ± 0.01) ms and T(*)2, slow = (6.21 ± 0.05) ms for the head were determined. In the thigh, the left and right satellite, both corresponding to the short component of the transverse relaxation time constant, take the following values: T(*)2, fast = (1.56 ± 0.03) ms and T(*)2, fast = (1.42 ± 0.03) ms. The centre line, which corresponds to the slow component, is T(*)2, slow = (9.67 ± 0.04) ms. The acquisition time of the spectra was approximately 10 min. Our results agree well with a non-vanishing electrical field gradient interacting with (39)K nuclei in the intracellular space of muscle tissue.

Radiofrequency excitation–related 23Na MRI signal loss in skeletal muscle, cartilage, and skin

“…It should be noted that other biologically relevant spin‐3/2 nuclei such as 39 K and 35 Cl may also exhibit rapid biexponential signal decay and residual quadrupole splitting. For example, T 2fast * = 0.51 ms and T 2slow * = 6.21 ms have been measured from spectroscopic studies of the human head at 7 T for 39 K . This signal decay is similar to that measured for 23 Na in skin (Figure ), and as a result, excitation‐related signal loss is expected to follow a similar trend to that of 23 Na in skin (Figure ).…”

“…This signal decay is similar to that measured for 23 Na in skin (Figure ), and as a result, excitation‐related signal loss is expected to follow a similar trend to that of 23 Na in skin (Figure ). Residual quadrupole splitting of approximately 200 Hz was measured from 39 K spectral measurements in skeletal muscle . This is smaller than that measured from 23 Na in cartilage, and will be less impactful.…”

X‐nuclei imaging: Current state, technical challenges, and future directions

“…). The feasibility has been demonstrated by . Furthermore, the ratio of 23 Na DQ to SQ signal in muscle was proposed to be a measure for Na + retention .…”

Double quantum filtered 23Na MRI with magic angle excitation of human skeletal muscle in the presence of B0 and B1 inhomogeneities

“…Reddy et al concluded from DQF‐MA 23 Na spectroscopy in vivo that sodium nuclei are partly located within anisotropic structures in human articular cartilage and brain as well as skeletal muscle . Moreover, Rösler et al have recently published spectra and DQF‐MA 39 K images of human thigh muscle tissue . Sodium DQF‐MA imaging has only been performed for human brain .…”