Tomoelastography of the native kidney: Regional variation and physiological effects on in vivo renal stiffness

Garcia, Stephan Rodrigo Marticorena; Großmann, Markus; Lang, S.; Tzschätzsch, Heiko; Dittmann, Florian; Hamm, Bernd; Braun, Jürgen; Guo, Jing; Sack, Ingolf

doi:10.1002/mrm.26892

Cited by 32 publications

(37 citation statements)

References 47 publications

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“…Very few studies have investigated the effect of water intake upon the stiffness of various anatomical regions within the kidney. Marticorena Garcia et al demonstrated an increase in cortex stiffness and decreased medulla stiffness with a water intake of 1 L. The results for cortex are consistent with the current study, in which significant increased stiffness was observed. However, a different observation was found for medulla, whereas we observed an increase in medulla stiffness.…”

Section: Discussionsupporting

confidence: 92%

“…Additionally, the stiffness values reported are influenced by the spatial resolution and the ROIs drawn. Also, Marticorena Garcia et al were not clear regarding the time delay before the scan after drinking water. These are a few differences which might have caused the discrepancies in the results reported between the current study and the one conducted by Marticorena Garcia et al…”

Section: Discussionmentioning

confidence: 98%

“…However, a different observation was found for medulla, whereas we observed an increase in medulla stiffness. Imaging protocol followed in the study by Marticorena Garcia et al imposed a restriction upon water and food consumption for 2 hours before the scan, whereas our study protocol did not impose any dietary or hydration restrictions prior to scanning subjects. Also, Marticorena Garcia et al used tomoelastography and a k‐MDEV reconstruction data‐processing algorithm, compared with the use of a single frequency (60 Hz) and 3D LFE used in our study, which explains the variations in estimation of regional stiffness values due to the effect of water intake.…”

Section: Discussionmentioning

confidence: 99%

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Magnetic resonance elastography‐derived stiffness of the kidneys and its correlation with water perfusion

et al. 2019

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Stiffness plays an important role in diagnosing renal fibrosis. However, kidney stiffness is altered by perfusion changes in many kidney diseases. Therefore, the aim of the current study is to determine the correlation of kidney stiffness with water intake. We hypothesize that kidney stiffness will increase with 1 L of water intake due to increased water perfusion to the kidneys. Additionally, stiffness of the kidneys will correlate with apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values before and after water intake. A 3 T MRI scanner was used to perform magnetic resonance elastography and diffusion tensor imaging of the kidneys on 24 healthy subjects (age range: 22‐66 years) before and after water intake of 1 L. A 3D T1‐weighted bladder scan was also performed to measure bladder volume before and after water intake. A paired t‐test was performed to evaluate the effect of water intake on the stiffness of kidneys, in addition to bladder volume. A Spearman correlation test was performed to determine the association between stiffness, bladder volume, ADC and FA values of both kidneys before and after water intake. The results show a significant increase in stiffness in different regions of the kidney (ie, percentage increase ranged from 3.6% to 7.5%) and bladder volume after water intake (all P < 0.05). A moderate significant negative correlation was observed between change in kidney stiffness and bladder volume (concordance correlation coefficient = ‐0.468, P < 0.05). No significant correlation was observed between stiffness and ADC or FA values before and after water intake in both kidneys (P > 0.05). Water intake caused a significant increase in the stiffness of the kidneys. The negative correlation between the change in kidney stiffness and bladder volume, before and after water intake, indicates higher perfusion pressure in the kidneys, leading to increased stiffness.

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Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

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Magnetic resonance elastography‐derived stiffness of the kidneys and its correlation with water perfusion

et al. 2019

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“…Values of k ‐MDEV and AHI are based on the assumption of local homogeneity, which is better fulfilled in large and macroscopically homogenous abdominal organs than the mouse brain . Nevertheless, k ‐MDEV has also been demonstrated to be successful in heterogeneous and smaller tissues such as the kidneys, pancreas, and prostate . Heterogeneous inversion methods are being developed and might replace k ‐MDEV in future studies of the mouse brain .…”

Section: Discussionmentioning

confidence: 99%

“…The wave numbers retrieved from multifrequency wave fields can be combined and inverted to compute compound maps of wave speed . This strategy, introduced in the literature as “tomoelastography,” has been demonstrated to be a noise‐robust method for full‐FOV MRE in abdominal and pelvic organs, providing high detail resolution and consistent values with respect to physiological and pathological alterations of mechanical tissue properties in vivo …”

Section: Introductionmentioning

confidence: 99%

Fast tomoelastography of the mouse brain by multifrequency single‐shot MR elastography

Bertalan

Guo

Tzschätzsch

et al. 2018

Magnetic Resonance in Med

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Purpose To introduce in vivo multifrequency single‐shot magnetic resonance elastography for full‐FOV stiffness mapping of the mouse brain and to compare in vivo stiffness of neural tissues with different white‐to‐gray matter ratios. Methods Viscous phantoms and 10 C57BL‐6 mice were investigated by 7T small‐animal MRI using a single‐shot spin‐echo planar imaging magnetic resonance elastography sequence with motion‐encoding gradients positioned before the refocusing pulse. Wave images were acquired over 10 minutes for 6 mechanical vibration frequencies between 900 and 1400 Hz. Stiffness maps of shear wave speed (SWS) were computed using tomoelastography data processing and compared with algebraic Helmholtz inversion (AHI) for signal‐to‐noise ratio (SNR) analysis. Different brain regions were analyzed including cerebral cortex, corpus callosum, hippocampus, and diencephalon. Results In phantoms, algebraic Helmholtz inversion–based SWS was systematically biased by noise and discretization, whereas tomoelastography‐derived SWS was consistent over the full SNR range analyzed. Mean in vivo SWS of the whole brain was 3.76 ± 0.33 m/s with significant regional variation (hippocampus = 4.91 ± 0.49 m/s, diencephalon = 4.78 ± 0.78 m/s, cerebral cortex = 3.53 ± 0.29 m/s, and corpus callosum = 2.89 ± 0.17 m/s). Conclusion Tomoelastography retrieves mouse brain stiffness within shorter scan times and with greater detail resolution than classical algebraic Helmholtz inversion–based magnetic resonance elastography. The range of SWS values obtained here indicates that mouse white matter is softer than gray matter at the frequencies investigated.

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Design, Construction, and Implementation of a Magnetic Resonance Elastography Actuator for Research Purposes

et al. 2022

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Magnetic resonance elastography (MRE) is a technique for determining the mechanical response of soft materials using applied harmonic deformation of the material and a motion‐sensitive magnetic resonance imaging sequence. This technique can elucidate significant information about the health and development of human tissue such as liver and brain, and has been used on phantom models (e.g., agar, silicone) to determine their suitability for use as a mechanical surrogate for human tissues in experimental models. The applied harmonic deformation used in MRE is generated by an actuator, transmitted in bursts of a specified duration, and synchronized with the magnetic resonance signal excitation. These actuators are most often a pneumatic design (common for human tissues or phantoms) or a piezoelectric design (common for small animal tissues or phantoms). Here, we describe how to design and assemble both a pneumatic and a piezoelectric MRE actuator for research purposes. For each of these actuator types, we discuss displacement requirements, end‐effector options and challenges, electronics and electronic‐driving requirements and considerations, and full MRE implementation. We also discuss how to choose the actuator type, size, and power based on the intended material and use. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Design, construction, and implementation of a convertible pneumatic MRE actuator for use with tissues and phantom models Basic Protocol 2: Design, construction, and implementation of a piezoelectric MRE actuator for localized excitation in phantom models

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Tomoelastography of the native kidney: Regional variation and physiological effects on in vivo renal stiffness

Cited by 32 publications

References 47 publications

Magnetic resonance elastography‐derived stiffness of the kidneys and its correlation with water perfusion

Magnetic resonance elastography‐derived stiffness of the kidneys and its correlation with water perfusion

Fast tomoelastography of the mouse brain by multifrequency single‐shot MR elastography

Design, Construction, and Implementation of a Magnetic Resonance Elastography Actuator for Research Purposes

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