Details
| Original language | English |
|---|---|
| Article number | 104079 |
| Journal | Journal of applied geophysics |
| Volume | 179 |
| Publication status | Published - Aug 2020 |
| Externally published | Yes |
Abstract
Magnetic Resonance Sounding (MRS) can image the spatial distribution of hydrologically relevant parameters in in the subsurface. However, the application of MRS is often limited by its low signal-to-noise ratio. The use of adiabatic excitation pulses show promising features to overcome this limitation. In this work, we study practical considerations when applying adiabatic pulses for MRS, i.e. calculation of the sensitivity kernel for varying pulse shapes and vertical resolution. The pulse shape is crucial for the performance of adiabatic pulses. We investigate the shapes of adiabatic pulses recorded during a MRS and observe small systematic deviations from the theoretical predicted pulse shape and variations between different pulse strengths. We show that the overall impact on the obtained sounding curve and inversion result was small. This enables to limit the time consuming modelling of the spin dynamic to one representative pulse shape, which significantly speeds up the calculation of the sensitivity kernel, necessary for the interpretation of MRS. Additionally, we show that on-resonance excitation generally outperforms adiabatic excitation concerning vertical resolution and depth of investigation (both up to a factor of two). This is true for a wide range of noise conditions. For a very shallow depth interval compared to the loop size, however, adiabatic excitation features improved imaging capabilities.
Keywords
- Adiabatic pulse, Magnetic Resonance Sounding, Nuclear magnetic resonance, Pulse shape, Spatial resolution
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geophysics
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In: Journal of applied geophysics, Vol. 179, 104079, 08.2020.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Application of adiabatic pulses for magnetic Resonance Sounding – Pulse shapes and resolution
AU - Dlugosch, Raphael
AU - Müller-Petke, Mike
N1 - Funding information: We like to thank Vista Clara Inc. to enable adiabatic excitation for scientific users of the GMR, Thomas Hiller (Leibniz Institute for Applied Geophysics) for providing the benchmark data set to validate our spin modelling and the two anonymous reviewers for their valuable comments.
PY - 2020/8
Y1 - 2020/8
N2 - Magnetic Resonance Sounding (MRS) can image the spatial distribution of hydrologically relevant parameters in in the subsurface. However, the application of MRS is often limited by its low signal-to-noise ratio. The use of adiabatic excitation pulses show promising features to overcome this limitation. In this work, we study practical considerations when applying adiabatic pulses for MRS, i.e. calculation of the sensitivity kernel for varying pulse shapes and vertical resolution. The pulse shape is crucial for the performance of adiabatic pulses. We investigate the shapes of adiabatic pulses recorded during a MRS and observe small systematic deviations from the theoretical predicted pulse shape and variations between different pulse strengths. We show that the overall impact on the obtained sounding curve and inversion result was small. This enables to limit the time consuming modelling of the spin dynamic to one representative pulse shape, which significantly speeds up the calculation of the sensitivity kernel, necessary for the interpretation of MRS. Additionally, we show that on-resonance excitation generally outperforms adiabatic excitation concerning vertical resolution and depth of investigation (both up to a factor of two). This is true for a wide range of noise conditions. For a very shallow depth interval compared to the loop size, however, adiabatic excitation features improved imaging capabilities.
AB - Magnetic Resonance Sounding (MRS) can image the spatial distribution of hydrologically relevant parameters in in the subsurface. However, the application of MRS is often limited by its low signal-to-noise ratio. The use of adiabatic excitation pulses show promising features to overcome this limitation. In this work, we study practical considerations when applying adiabatic pulses for MRS, i.e. calculation of the sensitivity kernel for varying pulse shapes and vertical resolution. The pulse shape is crucial for the performance of adiabatic pulses. We investigate the shapes of adiabatic pulses recorded during a MRS and observe small systematic deviations from the theoretical predicted pulse shape and variations between different pulse strengths. We show that the overall impact on the obtained sounding curve and inversion result was small. This enables to limit the time consuming modelling of the spin dynamic to one representative pulse shape, which significantly speeds up the calculation of the sensitivity kernel, necessary for the interpretation of MRS. Additionally, we show that on-resonance excitation generally outperforms adiabatic excitation concerning vertical resolution and depth of investigation (both up to a factor of two). This is true for a wide range of noise conditions. For a very shallow depth interval compared to the loop size, however, adiabatic excitation features improved imaging capabilities.
KW - Adiabatic pulse
KW - Magnetic Resonance Sounding
KW - Nuclear magnetic resonance
KW - Pulse shape
KW - Spatial resolution
UR - http://www.scopus.com/inward/record.url?scp=85086067984&partnerID=8YFLogxK
U2 - 10.1016/j.jappgeo.2020.104079
DO - 10.1016/j.jappgeo.2020.104079
M3 - Article
AN - SCOPUS:85086067984
VL - 179
JO - Journal of applied geophysics
JF - Journal of applied geophysics
SN - 0926-9851
M1 - 104079
ER -