title: High-resolution mechanical imaging of the kidney.
abstract: The objective of this study was to test the feasibility and reproducibility of in vivo high-resolution mechanical imaging of the asymptomatic human kidney. Hereby nine volunteers were examined at three different physiological states of urinary bladder filling (a normal state, urinary urgency, and immediately after urinary relief). Mechanical imaging was performed of the in vivo kidney using three-dimensional multifrequency magnetic resonance elastography combined with multifrequency dual elastovisco inversion. Other than in classical elastography, where the storage and loss shear moduli are evaluated, we analyzed the magnitude |G(⁎)| and the phase angle φ of the complex shear modulus reconstructed by simultaneous inversion of full wave field data corresponding to 7 harmonic drive frequencies from 30 to 60Hz and a resolution of 2.5mm cubic voxel size. Mechanical parameter maps were derived with a spatial resolution superior to that in previous work. The group-averaged values of |G(⁎)| were 2.67±0.52kPa in the renal medulla, 1.64±0.17kPa in the cortex, and 1.17±0.21kPa in the hilus. The phase angle φ (in radians) was 0.89±0.12 in the medulla, 0.83±0.09 in the cortex, and 0.72±0.06 in the hilus. All regional differences were significant (P<0.001), while no significant variation was found in relation to different stages of bladder filling. In summary our study provides first high-resolution maps of viscoelastic parameters of the three anatomical regions of the kidney. |G(⁎)| and φ provide novel information on the viscoelastic properties of the kidney, which is potentially useful for the detection of renal lesions or fibrosis.
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Campus Charité Mitte, Berlin, Germany.
authors.forename: Kaspar-Josche
authors.initials: KJ
authors.lastname: Streitberger
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Campus Charité Mitte, Berlin, Germany.
authors.forename: Jing
authors.initials: J
authors.lastname: Guo
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Campus Charité Mitte, Berlin, Germany.
authors.forename: Heiko
authors.initials: H
authors.lastname: Tzschätzsch
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Campus Charité Mitte, Berlin, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Hirsch
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Campus Charité Mitte, Berlin, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Fischer
authors.affiliation: Institute of Medical Informatics, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Braun
authors.affiliation: Department of Radiology, Charité - Universitätsmedizin Berlin, Campus Charité Mitte, Berlin, Germany. Electronic address: ingolf.sack@charite.de.
authors.forename: Ingolf
authors.initials: I
authors.lastname: Sack
mesh_terms: D000328:Adult; D054459:Elasticity Imaging Techniques / Q000295:instrumentation / Q000379:methods* / Q000592:standards*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000295:instrumentation / Q000379:methods / Q000592:standards; D007668:Kidney / Q000033:anatomy & histology* / Q000502:physiology*; D007672:Kidney Cortex / Q000033:anatomy & histology / Q000502:physiology; D007679:Kidney Medulla / Q000033:anatomy & histology / Q000502:physiology; D007682:Kidney Pelvis / Q000033:anatomy & histology / Q000502:physiology; D008297:Male; D012016:Reference Values; D015203:Reproducibility of Results; D033081:Shear Strength / Q000502:physiology; D001743:Urinary Bladder / Q000033:anatomy & histology / Q000502:physiology; D014554:Urination / Q000502:physiology; D014732:Vibration; D055815:Young Adult
keywords: 3D multifrequency MRE; Kidney; Multifrequency inversion; Pressure; Shear modulus; Time harmonic elastography; Viscoelasticity