TY  - JOUR
AB  - PURPOSE: T 2 ∗   $$ {\mathrm{T}}_2^{\ast } $$  quantification from gradient echo magnetic resonance imaging is particularly affected by subject motion due to its high sensitivity to magnetic field inhomogeneities, which are influenced by motion and might cause signal loss. Thus, motion correction is crucial to obtain high-quality    T 2 ∗   $$ {\mathrm{T}}_2^{\ast } $$  maps. METHODS: We extend PHIMO, our previously introduced learning-based physics-informed motion correction method for low-resolution    T 2 ∗   $$ {\mathrm{T}}_2^{\ast } $$  mapping. Our extended version, PHIMO+, utilizes acquisition knowledge to enhance the reconstruction performance for challenging motion patterns and increase PHIMO's robustness to varying strengths of magnetic field inhomogeneities across the brain. We perform comprehensive evaluations regarding motion detection accuracy and image quality for data with simulated and real motion. RESULTS: PHIMO+ outperforms the learning-based baseline methods both qualitatively and quantitatively with respect to line detection and image quality. Moreover, PHIMO+ performs on par with a conventional state-of-the-art motion correction method for    T 2 ∗   $$ {\mathrm{T}}_2^{\ast } $$  quantification from gradient echo MRI, which relies on redundant data acquisition. CONCLUSION: PHIMO+'s competitive motion correction performance, combined with a reduction in acquisition time by over 40% compared to the state-of-the-art method, makes it a promising solution for motion-robust    T 2 ∗   $$ {\mathrm{T}}_2^{\ast } $$  quantification in research settings and clinical routine.
AU  - Eichhorn, H.
AU  - Spieker, V.
AU  - Hammernik, K.*
AU  - Saks, E.*
AU  - Felsner, L.*
AU  - Weiss, K.*
AU  - Preibisch, C.*
AU  - Schnabel, J.A.
C1  - 75387
C2  - 58363
CY  - 111 River St, Hoboken 07030-5774, Nj Usa
SP  - 346-362
TI  - Motion-robust T∗2 quantification from low-resolution gradient echo brain MRI with physics-informed deep learning.
JO  - Magn. Reson. Med.
VL  - 95
IS  - 1
PB  - Wiley
PY  - 2026
SN  - 0740-3194
ER  - 

TY  - JOUR
AB  - PURPOSE: To develop a    B 0   $$ {B}_0 $$  self-navigation approach to estimate respiratory motion for motion-corrected liver    T 1   $$ {T}_1 $$  mapping using a Look-Locker acquisition with radial stack-of-stars trajectory. METHODS: The proposed method derives 1D field-map profiles from the oversampled k-space center to estimate a normalized breathing curve and the    B 0   $$ {B}_0 $$  variation amplitude for each slice and coil.    B 0   $$ {B}_0 $$  drift and contrast variations, inherent to the Look-Locker acquisition, were modeled and corrected by fitting and demodulating drift and offset terms. The breathing curve was employed to bin data into motion states for motion-resolved reconstruction, followed by water-specific    T 1   $$ {T}_1 $$  mapping. Simulations with an anatomical body model and in vivo experiments with a Look-Locker multi-echo gradient echo sequence were performed to validate the technique. The estimated normalized breathing curve was compared with magnitude- and phase-based self-navigation approaches using principal component analysis. RESULTS: The proposed    B 0   $$ {B}_0 $$  self-navigation reliably estimated the normalized breathing curve and the    B 0   $$ {B}_0 $$  variation amplitude in simulations and in vivo.    B 0   $$ {B}_0 $$  variation amplitudes increased with greater tissue displacement, with median values across slices and coils ranging from 4 to 15 Hz at 3 T in volunteers. Motion-resolved reconstruction using the estimated breathing curve reduced motion artifacts and improved image and    T 1   $$ {T}_1 $$  mapping quality compared to motion-averaged reconstruction. CONCLUSION: B 0   $$ {B}_0 $$  self-navigation allows estimation of respiratory motion in acquisitions with varying contrast and quantifies the    B 0   $$ {B}_0 $$  variation amplitude, providing a possible surrogate signal for tissue displacement and enabling self-gated liver    T 1   $$ {T}_1 $$  mapping using a Look-Locker approach.
AU  - Stelter, J.*
AU  - Weiss, K.*
AU  - Spieker, V.
AU  - Schnabel, J.A.
AU  - Braren, R.F.*
AU  - Karampinos, D.C.*
C1  - 74774
C2  - 57556
CY  - 111 River St, Hoboken 07030-5774, Nj Usa
TI  - B0 navigator enables respiratory motion navigation in radial stack-of-stars liver Look-Locker T1 mapping.
JO  - Magn. Reson. Med.
PB  - Wiley
PY  - 2025
SN  - 0740-3194
ER  - 

TY  - JOUR
AB  - PURPOSE: Free water in cortical bone is either contained in nearly cylindrical structures (mainly Haversian canals oriented parallel to the bone axis) or in more spherically shaped pores (lacunae). Those cavities have been reported to crucially influence bone quality and mechanical stability. Susceptibility differences between bone and water can lead to water frequency shifts dependent on the geometric characteristics. The purpose of this study is to calculate and measure the frequency distribution of the water signal in MRI in dependence of the microscopic bone geometry. METHODS: Finite element modeling and analytical approaches were performed to characterize the free water components of bone. The previously introduced UTE-FID technique providing spatially resolved FID-spectra was used to measure the frequency distribution pixel-wise for different orientations of the bone axis. RESULTS: The frequency difference between free water in spherical pores and in canals parallel to B0 amounts up to approximately 100 Hz at 3T. Simulated resonance frequencies showed good agreement with the findings in UTE-FID spectra. The intensity ratio of the two signal components (parallel canals and spherical pores) was found to vary between periosteal and endosteal regions. CONCLUSION: Spatially resolved UTE-FID examinations allow the determination of the frequency distribution of signals from free water in cortical bone. This frequency distribution indicates the composition of the signal contributions from nearly spherical cavities and cylindrical canals which allows for further characterization of bone structure and status.
AU  - Fischer, A.
AU  - Martirosian, P.*
AU  - Machann, J.
AU  - Fränkle, B.*
AU  - Schick, F.*
C1  - 69909
C2  - 55319
CY  - 111 River St, Hoboken 07030-5774, Nj Usa
TI  - Frequency shifts of free water signals from compact bone: Simulations and measurements using a UTE-FID sequence.
JO  - Magn. Reson. Med.
PB  - Wiley
PY  - 2024
SN  - 0740-3194
ER  - 

TY  - JOUR
AB  - PURPOSE: To test soy lecithin as a substance added to water for the construction of MRI phantoms with tissue-like diffusion coefficients. The performance of soy lecithin was assessed for the useable range of adjustable ADC values, the degree of non-Gaussian diffusion, simultaneous effects on relaxation times, and spectral signal properties. METHODS: Aqueous soy lecithin solutions of different concentrations (0%, 0.5%, 1%, 2%, 3% …, 10%) and soy lecithin-agar gels were prepared and examined on a 3 Tesla clinical scanner at 18.5° ± 0.5°C. Echoplanar sequences (b values: 0-1000/3000 s/mm2 ) were applied for ADC measurements. Quantitative relaxometry and MRS were performed for assessment of T1 , T2 , and detectable spectral components. RESULTS: The presence of soy lecithin significantly restricts the diffusion of water molecules and mimics the nearly Gaussian nature of diffusion observed in tissue (for b values <1000 s/mm2 ). ADC values ranged from 2.02 × 10-3  mm2 /s to 0.48 × 10-3  mm2 /s and cover the entire physiological range reported on biological tissue. Measured T1 /T2 values of pure lecithin solutions varied from 2685/2013 to 668/133 ms with increasing concentration. No characteristic signals of soy lecithin were observed in the MR spectrum. The addition of agar to the soy lecithin solutions allowed T2 values to be well adjusted to typical values found in parenchymal tissue without affecting the soy lecithin-controlled ADC value. CONCLUSION: Soy lecithin is a promising substance for the construction of diffusion phantoms with tissue-like ADC values. It provides several advantages over previously proposed substances, in particular a wide range of adjustable ADC values, the lack of additional 1 H-signals, and the possibility to adjust ADC and T2 values (by adding agar) almost independently of each other.
AU  - Fritz, V.*
AU  - Martirosian, P.*
AU  - Machann, J.
AU  - Thorwarth, D.*
AU  - Schick, F.*
C1  - 66840
C2  - 53312
TI  - Soy lecithin: A beneficial substance for adjusting the ADC in aqueous solutions to the values of biological tissues.
JO  - Magn. Reson. Med.
PY  - 2022
SN  - 0740-3194
ER  - 

TY  - JOUR
AB  - More than 100 attendees from Australia, Austria, Belgium, Canada, China, Germany, Hong Kong, Indonesia, Japan, Malaysia, the Netherlands, the Philippines, Republic of Korea, Singapore, Sweden, Switzerland, the United Kingdom, and the United States convened in Singapore for the 2019 ISMRM-sponsored workshop on MRI of Obesity and Metabolic Disorders. The scientific program brought together a multidisciplinary group of researchers, trainees, and clinicians and included sessions in diabetes and insulin resistance; an update on recent advances in water–fat MRI acquisition and reconstruction methods; with applications in skeletal muscle, bone marrow, and adipose tissue quantification; a summary of recent findings in brown adipose tissue; new developments in imaging fat in the fetus, placenta, and neonates; the utility of liver elastography in obesity studies; and the emerging role of radiomics in population-based “big data” studies. The workshop featured keynote presentations on nutrition, epidemiology, genetics, and exercise physiology. Forty-four proffered scientific abstracts were also presented, covering the topics of brown adipose tissue, quantitative liver analysis from multiparametric data, disease prevalence and population health, technical and methodological developments in data acquisition and reconstruction, newfound applications of machine learning and neural networks, standardization of proton density fat fraction measurements, and X-nuclei applications. The purpose of this article is to summarize the scientific highlights from the workshop and identify future directions of work.
AU  - Hu, H.H.*
AU  - Branca, R.T.*
AU  - Hernando, D.*
AU  - Karampinos, D.C.*
AU  - Machann, J.
AU  - McKenzie, C.A.*
AU  - Wu, H.H.*
AU  - Yokoo, T.*
AU  - Velan, S.S.*
C1  - 57508
C2  - 47838
CY  - 111 River St, Hoboken 07030-5774, Nj Usa
SP  - 1565-1576
TI  - Magnetic resonance imaging of obesity and metabolic disorders: Summary from the 2019 ISMRM Workshop.
JO  - Magn. Reson. Med.
VL  - 83
IS  - 5
PB  - Wiley
PY  - 2020
SN  - 0740-3194
ER  - 

TY  - JOUR
AB  - PurposeAssessment of temporal and spatial relations between spontaneous mechanical activities in musculature (SMAM) at rest as revealed by diffusion-weighted imaging (DWI) and electrical muscular activities in surface EMG (sEMG). Potential influences of static and radiofrequency magnetic fields on muscular activity on sEMG measurements at rest were examined systematically. MethodsSeries of diffusion-weighted stimulated echo planar imaging were recorded with concurrent sEMG measurements. Electrical activities in sEMG were analyzed by non-parametric Friedman and two-sample Kolmogorov-Smirnov test. Direct correlation of both modalities was investigated by temporal mapping of electrical activity in sEMG to DWI repetition interval. ResultsElectrical activities in sEMG and number of visible SMAMs in DWI showed a strong correlation (=0.9718). High accordance between sEMG activities and visible SMAMs in DWI in a near-surface region around sEMG electrodes was achieved. Characteristics of sEMG activities were almost similar under varying magnetic field conditions. ConclusionVisible SMAMs in DWI have shown a close and direct relation to concurrent signals recorded by sEMG. MR-related magnetic fields had no significant effects on findings in sEMG. Hence, appearance of SMAMs in DWI should not be considered as imaging artifact or as effects originating from the special conditions of MR examinations. Spatial and temporal distributions of SMAMs indicate characteristics of spontaneous (microscopic) mechanical muscular action at rest. Therefore, DWI techniques should be considered as non-invasive tools for studying physiology and pathophysiology of spontaneous activities in resting muscle. Magn Reson Med 79:2784-2794, 2018.
AU  - Schwartz, M.*
AU  - Steidle, G.*
AU  - Martirosian, P.*
AU  - Ramos-Murguialday, A.*
AU  - Preissl, H.
AU  - Stemmer, A.*
AU  - Yang, B.*
AU  - Schick, F.*
C1  - 53196
C2  - 44388
CY  - Hoboken
SP  - 2784-2794
TI  - Spontaneous mechanical and electrical activities of human calf musculature at rest assessed by repetitive single-shot diffusion-weighted MRI and simultaneous surface electromyography.
JO  - Magn. Reson. Med.
VL  - 79
IS  - 5
PB  - Wiley
PY  - 2018
SN  - 0740-3194
ER  - 

TY  - JOUR
AB  - Purpose: Lipid signals measured by H-1 MR spectroscopy cannot be adequately quantified by common fitting routines like VARPRO or AMARES, if lipid spectra are distorted by irregular spatial and temporal inhomogeneities of the static magnetic field during readout. A fully automatic reference deconvolution algorithm is presented that eliminates these distortions before application of fitting routines. Methods: The measured signal of the dominant methyl resonance is isolated with aid of a spectral estimator (estimation of parameters via rotational invariance techniques) and used as reference signal for estimation of distortions. A Wiener filter is applied to deconvolve those distortions in the lipid spectrum. Performance of the algorithm is assessed for different bandwidths and shapes of distortions, using artificially distorted as well as measured data. Results: Application of the fully automatic reference deconvolution algorithm on simulated spectra yields a distinct increase in quantification accuracy. Deconvolved in vivo spectra of subcutaneous fat indicate reduced spectral overlap after application of the proposed strategy. Conclusion: The proposed method is helpful for in vivo magnetic resonance spectroscopy of adipose tissue to correct for effects of field inhomogeneities within the voxel and for inevitable eddy current effects. Quantification accuracy is improved by eliminating distortions before application of fitting routines.
AU  - Mauch, L.*
AU  - Steidle, G.*
AU  - Machann, J.
AU  - Yang, B.*
AU  - Schick, F.*
C1  - 48447
C2  - 41183
CY  - Hoboken
SP  - 1391-1401
TI  - A fully automatic reference deconvolution strategy to increase the accuracy of in vivo lipid signal quantification.
JO  - Magn. Reson. Med.
VL  - 75
IS  - 4
PB  - Wiley-blackwell
PY  - 2016
SN  - 0740-3194
ER  - 

TY  - JOUR
AU  - Heim, S.*
AU  - Hahn, K.R.
AU  - Sämann, P.G.*
AU  - Fahrmeir, L.*
AU  - Auer, D.P.*
C1  - 1367
C2  - 21941
SP  - 582-589
TI  - Assessing DTI data quality using bootstrap analysis.
JO  - Magn. Reson. Med.
VL  - 52
PY  - 2004
SN  - 0740-3194
ER  - 

TY  - JOUR
AB  - The purpose of this study was to develop an MR-based technique for quantitative analysis of joint surface size, surface curvature, and joint incongruity and to assess its reproducibility under in vivo imaging conditions. The surface areas were determined after 3D reconstruction of the joint by triangulation and the incongruity by Gaussian curvature analysis. The precision was tested by analyzing four replicated MRI datasets of human knees in 14 individuals. The algorithms were shown to produce accurate data in geometric test objects. The interscan precision was <4% (CV%) for surface area, 2.9-5.7 m(-1) (SD) for the mean principal curvature, and 4.1-7.4 m(-1) for congruence indices. Incongruity was highest in the femoropatellar joint (79.7 m(-1)) and lowest in the medial femorotibial joint (28.6 m(-1)). This technique will permit identification of the specific role of surface size, curvature, and incongruity as potential risk factors for osteoarthritis.
AU  - Hohe, J.
AU  - Ateshian, G.*
AU  - Reiser, M.*
AU  - Englmeier, K.-H.
AU  - Eckstein, F.*
C1  - 10010
C2  - 20133
SP  - 554-561
TI  - Surface Size, Curvature Analysis and Assessment of Knee Joint Incongruity with MRI in vivo.
JO  - Magn. Reson. Med.
VL  - 47
PB  - Wiley
PY  - 2002
SN  - 0740-3194
ER  - 

TY  - JOUR
AB  - The purpose of this study was to characterize T-1, particularly in the hyperthermia temperature range (ca. 37-44degreesC), in order to control regional hyperthermia with MR monitoring using 0.2 Tesla, and to improve T-1 mapping. A single-slice and a new multislice T One by Multiple Read-Out Pulses" (TOMROP) pulse sequence were used for fast ill mapping in a clinical MRI hyperthermia hybrid system. Temporal stability, temperature sensitivity, and reversibility of T-1 were investigated in a polyamidacryl gel phantom and in samples of muscle and adipose tissues from turkey and pig, and verified in patients. In the gel phantom a high linear correlation between T-1 and temperature (R-2 = 0.97) was observed. In muscle and adipose tissue, T-1 and temperature had a linear relationship below a breakpoint of 43degreesC. Above this breakpoint muscle tissue showed irreversible tissue changes; these effects were not visible in adipose tissue. The ex vivo results were confirmed in vivo under clinical conditions. T-1, mapping allows the characterization of hyperthermia-related tissue response in healthy tissue. T-1, in combination with fast mapping, is suitable for controlling regional hyperthermia at 0.2 T within the hybrid system."
AU  - Peller, M.*
AU  - Reinl, H.M.
AU  - Weigel, A.*
AU  - Meininger, M.*
AU  - Issels, R.D.
AU  - Reiser, M.*
C1  - 10011
C2  - 20248
SP  - 1194-1201
TI  - T1 Relaxation Time at 0.2 Tesla for Monitoring Regional Hyperthermia : Feasibility Study in Muscle and Adipose Tissue.
JO  - Magn. Reson. Med.
VL  - 47
PB  - Wiley
PY  - 2002
SN  - 0740-3194
ER  - 

TY  - JOUR
AU  - Stammberger, T.
AU  - Hohe, J.
AU  - Englmeier, K.-H.
AU  - Reiser, M.*
AU  - Eckstein, F.
C1  - 21876
C2  - 20107
SP  - 592-601
TI  - Elastic Registration of 3D Cartilage Surfaces from MR Image Data for Detection Local Changes in Cartilage Thickness.
JO  - Magn. Reson. Med.
VL  - 44
PY  - 2000
SN  - 0740-3194
ER  - 

TY  - JOUR
AU  - Stammberger, T.
AU  - Eckstein, F.*
AU  - Englmeier, K.-H.
AU  - Reiser, M.*
C1  - 21207
C2  - 19306
SP  - 529-536
TI  - Determination of 3D cartilage thickness data from MR imaging: Computational method and reproducibility in the living.
JO  - Magn. Reson. Med.
VL  - 41
PY  - 1999
SN  - 0740-3194
ER  -