Tomoelastography of the prostate using multifrequency MR elastography and externally placed pressurized‐air drivers

Dittmann, Florian; Reiter, Rolf; Guo, Jing; Haas, Matthias; Asbach, Patrick; Fischer, Thomas; Braun, Jürgen; Sack, Ingolf

doi:10.1002/mrm.26769

Cited by 35 publications

(31 citation statements)

References 19 publications

(41 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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 actuator was supplied by a low‐current transistor–transistor logic function generator (CGC Instruments, Chemnitz, Germany). The function generator was synchronized to the scanner clock based on a 10‐MHz pulsed signal (to avoid any latency of the wave relative to the scanner after minutes of continuous vibrations) and controlled by “smart triggers” (to initiate the vibration and to allow automatic selection of vibration frequency, number of cycles, and signal amplitudes by the imaging protocol) . The vibrations were transferred into the head cradle of the animal holder through a carbon fiber rod.…”

Section: Methodsmentioning

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%

“…18 This strategy, introduced in the literature as "tomoelastography," has been demonstrated to be a noiserobust 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. [19][20][21] However, tomoelastography of the human brain is degraded by an abundance of solid-fluid (slip) interfaces that disturb directional filters because of marked changes of local wavenumbers. 2 The murine cortex differs from the human cortex in that it is less folded and has fewer sulci, potentially reducing artifacts related to slip boundaries.…”

mentioning

confidence: 99%

See 3 more Smart Citations

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

Bertalan

Guo

Tzschätzsch

et al. 2018

Magnetic Resonance in Med

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

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

Bertalan

Guo

Tzschätzsch

et al. 2018

Magnetic Resonance in Med

Self Cite

View full text Add to dashboard Cite

show abstract

“…The manually measured wave lengths were [38,32,27,22] mm in the liver and [59, 51, 45, 42] mm in the filling material for actuation frequencies of [50, 60, 70, 80] Hz. The manually measured wave lengths were [38,32,27,22] mm in the liver and [59, 51, 45, 42] mm in the filling material for actuation frequencies of [50, 60, 70, 80] Hz.…”

Section: Image Evaluationmentioning

confidence: 99%

Coupled actuators with a mechanically synchronized phase during MR elastography: A phantom feasibility study

Neumann

Lehnart

Vetter

et al. 2018

Concepts Magn Reson

View full text Add to dashboard Cite

Introduction: Magnetic resonance elastography (MRE) is an MR imaging method for the quantification of spatial stiffness of soft tissues using mechanically induced dynamic shear waves. In some applications, the penetration of shear waves can be limited through attenuation and shadowing of the waves. In order to increase the actuator performance, we present a dual driver approach to compensate for shear wave attenuation and to achieve better coverage over the entire region of interest. Materials and Methods: (a) We designed pneumatic turbines that created a sinusoidal centrifugal force due to an eccentric weight. Two turbines were connected in-phase with each eccentric weight having the same angular position relative to its pivot point. (b) We developed a tissue elasticity mimicking abdominal phantom. (c) The phantom served as a test object to investigate the feasibility to generate shear waves at two surface origins with the dual actuator system and to compare it against a single actuation setup. Results and Discussion: A stable phase relationship of the shear waves generated by the turbines was achieved as the positions of the eccentric weights were mechanically fixed. The abdominal phantom yielded sufficient MR signal. Liver and rib cage were clearly visible in MR imaging. The shear waves generated by the dual turbine propagated through the region of interest. Our turbine design is reproducible through 3D printing and can be integrated into existing clinical equipment for 1.5 T and 3 T scanners. K E Y W O R D Santhropomorphic phantom, dual actuator, magnetic resonance elastography, magnetic resonance imaging, shear wave actuation

show abstract

Prostate cancer assessment using MR elastography of fresh prostatectomy specimens at 9.4 T

Reiter

Majumdar

Kearney

et al. 2019

Magnetic Resonance in Med

Self Cite

View full text Add to dashboard Cite

Purpose Despite its success in the assessment of prostate cancer (PCa), in vivo multiparametric MRI has limitations such as interobserver variability and low specificity. Several MRI methods, among them MR elastography, are currently being discussed as candidates for supplementing conventional multiparametric MRI. This study aims to investigate the detection of PCa in fresh ex vivo human prostatectomy specimens using MR elastography. Methods Fourteen fresh prostate specimens from men with clinically significant PCa without formalin fixation or prior radiation therapy were examined by MR elastography at 500 Hz immediately after radical prostatectomy in a 9.4T preclinical scanner. Specimens were divided into 12 segments for both calculation of storage modulus (G′ in kilopascals) and pathology (Gleason score) as reference standard. Sensitivity, specificity, and area under the receiver operating characteristic curve were calculated to assess PCa detection. Results The mean G′ and SD were as follows: all segments, 8.74 ± 5.26 kPa; healthy segments, 5.44 ± 4.40 kPa; and cancerous segments, 10.84 ± 4.65 kPa. The difference between healthy and cancerous segments was significant with P ≤ .001. Diagnostic performance assessed with the Youden index was as follows: sensitivity, 69%; specificity, 79%; area under the curve, 0.81; and cutoff, 10.67 kPa. Conclusion Our results suggest that prostate MR elastography has the potential to improve diagnostic performance of multiparametric MRI, especially regarding its 2 major limitations: interobserver variability and low specificity. Particularly the high value for specificity in PCa detection is a stimulating result and encourages further investigation of this method.

show abstract

Tomoelastography of the prostate using multifrequency MR elastography and externally placed pressurized‐air drivers

Cited by 35 publications

References 19 publications

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

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

Coupled actuators with a mechanically synchronized phase during MR elastography: A phantom feasibility study

Prostate cancer assessment using MR elastography of fresh prostatectomy specimens at 9.4 T

Contact Info

Product

Resources

About