TY  - JOUR
AB  - PURPOSE: To develop and validate a data acquisition scheme combined with a motion-resolved reconstruction and dictionary-matching-based parameter estimation to enable free-breathing isotropic resolution self-navigated whole-liver simultaneous water-specific   T 1  $$ {\mathrm{T}}_1 $$  (   wT 1  $$ {\mathrm{wT}}_1 $$  ) and   T 2  $$ {\mathrm{T}}_2 $$  (   wT 2  $$ {\mathrm{wT}}_2 $$  ) mapping for the characterization of diffuse and oncological liver diseases. METHODS: The proposed data acquisition consists of a magnetization preparation pulse and a two-echo gradient echo readout with a radial stack-of-stars trajectory, repeated with different preparations to achieve different   T 1  $$ {\mathrm{T}}_1 $$  and   T 2  $$ {\mathrm{T}}_2 $$  contrasts in a fixed acquisition time of 6 min. Regularized reconstruction was performed using self-navigation to account for motion during the free-breathing acquisition, followed by water-fat separation. Bloch simulations of the sequence were applied to optimize the sequence timing for    B 1   $$ {B}_1 $$  insensitivity at 3 T, to correct for relaxation-induced blurring, and to map   T 1  $$ {\mathrm{T}}_1 $$  and   T 2  $$ {\mathrm{T}}_2 $$  using a dictionary. The proposed method was validated on a water-fat phantom with varying relaxation properties and in 10 volunteers against imaging and spectroscopy reference values. The performance and robustness of the proposed method were evaluated in five patients with abdominal pathologies. RESULTS: Simulations demonstrate good    B 1   $$ {B}_1 $$  insensitivity of the proposed method in measuring   T 1  $$ {\mathrm{T}}_1 $$  and   T 2  $$ {\mathrm{T}}_2 $$  values. The proposed method produces co-registered   wT 1  $$ {\mathrm{wT}}_1 $$  and   wT 2  $$ {\mathrm{wT}}_2 $$  maps with a good agreement with reference methods (phantom:   wT 1 = 1 . 02  wT 1,ref - 8 . 93  ms , R 2 = 0 . 991 $$ {\mathrm{wT}}_1=1.02\kern0.1em {\mathrm{wT}}_{1,\mathrm{ref}}-8.93\kern0.1em \mathrm{ms},{R}^2=0.991 $$  ;   wT 2 = 1 . 03  wT 2,ref + 0 . 73  ms , R 2 = 0 . 995 $$ {\mathrm{wT}}_2=1.03\kern0.1em {\mathrm{wT}}_{2,\mathrm{ref}}+0.73\kern0.1em \mathrm{ms},{R}^2=0.995 $$  ). The proposed   wT 1  $$ {\mathrm{wT}}_1 $$  and   wT 2  $$ {\mathrm{wT}}_2 $$  mapping exhibits good repeatability and can be robustly performed in patients with pathologies. CONCLUSIONS: The proposed method allows whole-liver   wT 1  $$ {\mathrm{wT}}_1 $$  and   wT 2  $$ {\mathrm{wT}}_2 $$  quantification with high accuracy at isotropic resolution in a fixed acquisition time during free-breathing.
AU  - Stelter, J.*
AU  - Weiss, K.*
AU  - Steinhelfer, L.*
AU  - Spieker, V.
AU  - Huaroc Moquillaza, E.*
AU  - Zhang, W.*
AU  - Makowski, M.R.*
AU  - Schnabel, J.A.
AU  - Kainz, B.*
AU  - Braren, R.F.*
AU  - Karampinos, D.C.*
C1  - 71424
C2  - 56168
CY  - 111 River St, Hoboken 07030-5774, Nj Usa
TI  - Simultaneous whole-liver water T1 and T2 mapping withisotropic resolution during free-breathing.
JO  - NMR Biomed.
PB  - Wiley
PY  - 2024
SN  - 0952-3480
ER  - 

TY  - JOUR
AB  - 1H-MR spectroscopy of skeletal muscle provides insight into metabolism that is not available noninvasively by other methods. The recommendations given in this article are intended to guide those who have basic experience in general MRS to the special application of 1H-MRS in skeletal muscle. The highly organized structure of skeletal muscle leads to effects that change spectral features far beyond simple peak heights, depending on the type and orientation of the muscle. Specific recommendations are given for the acquisition of three particular metabolites (intramyocellular lipids, carnosine and acetylcarnitine) and for preconditioning of experiments and instructions to study volunteers.
AU  - Krššák, M.*
AU  - Lindeboom, L.*
AU  - Schrauwen-Hinderling, V.*
AU  - Szczepaniak, L.S.*
AU  - Derave, W.*
AU  - Lundbom, J.*
AU  - Befroy, D.*
AU  - Schick, F.*
AU  - Machann, J.
AU  - Kreis, R.*
AU  - Boesch, C.*
C1  - 58795
C2  - 48331
TI  - Proton magnetic resonance spectroscopy in skeletal muscle: Experts' consensus recommendations.
JO  - NMR Biomed.
PY  - 2021
SN  - 0952-3480
ER  - 

TY  - JOUR
AB  - The standard procedure for blood glucose measurements is enzymatic testing. This method is cheap, but requires small samples of open blood with direct contact to the test medium. In principle, NMR provides non-contact analysis of body fluids, but high-field spectrometers are expensive and cannot be easily utilized under clinical conditions. Low-field NMR systems with permanent magnets are becoming increasingly smaller and more affordable. The studies presented here aim at exploring the capabilities of low-field NMR for measuring glucose concentrations in whole blood. For this purpose, a modern 1 T benchtop NMR spectrometer was used. Challenges arise from broad spectral lines, the glucose peak locations close to the water signal, low SNR and the interference with signals from other blood components. Whole blood as a sample comprises even more boundary conditions: crucial for reliable results are avoiding the separation of plasma and cells by gravitation and reliable reference values. First, the accuracy of glucose levels measured by NMR was tested using aqueous glucose solutions and commercially available bovine plasma. Then, 117 blood samples from oral glucose tolerance testing were measured with minimal preparation by simple pulse-acquire NMR experiments. The analysis itself is the key to achieve high precision, so several approaches were investigated: peak integration, orthogonal projection to latent structure analysis and support vector machine regression. Correlations between results from the NMR spectra and the routine laboratory automated analyzer revealed an RMSE of 7.90 mg/dL for the best model. 91.5% of the model output lies within the limits of the German Medical Association guidelines, which require the glucose measurement to be within 11% of the reference method. It is concluded that spectral quantification of glucose in whole blood samples by high-quality NMR spectrometers operating at 1 T is feasible with sufficient accuracy.
AU  - Stolz, M.*
AU  - Schlawne, C.*
AU  - Hoffmann, J.*
AU  - Hartmann, V.
AU  - Marini, I.*
AU  - Fritsche, A.
AU  - Peter, A.
AU  - Bakchoul, T.*
AU  - Schick, F.
C1  - 59587
C2  - 48858
CY  - 111 River St, Hoboken 07030-5774, Nj Usa
TI  - Feasibility of precise and reliable glucose quantification in human whole blood samples by 1 tesla benchtop NMR.
JO  - NMR Biomed.
PB  - Wiley
PY  - 2020
SN  - 0952-3480
ER  - 

TY  - JOUR
AB  - It is generally accepted that the amount and distribution of adipose tissue (AT) in the human body play an important role in the pathogenesis of metabolic diseases. In addition, metabolic effects of released saturated fatty acids (FAs) in blood are known to be more critical than those of unsaturated FAs. However, little is known about the variability in unsaturation of FAs in various AT compartments. The aim of this prospective study was the assessment of mono- and polyunsaturated FAs in various AT compartments by localized H-1-MRS in order to obtain insight into the intra- and interindividual variability. Associations of FA unsaturation with intrahepatic lipids (IHLs), insulin sensitivity and related AT volumes were analyzed. Fifty healthy Caucasians (36 male, 14 female) participated in this study. Spectroscopic examinations were performed in subcutaneous adipose tissue in the neck (SCAT(neck)), abdominal deep subcutaneous adipose tissue (DSCAT), abdominal superficial subcutaneous adipose tissue (SSCAT), visceral adipose tissue (VAT), tibial bone marrow (BM) and subcutaneous adipose tissue of the lower leg (SCAT(calf)) at 3T. Unsaturated index (UI) was calculated by the ratio of olefinic and methyl resonances, polyunsaturated index (PUI) by the ratio of diallylic and methyl resonances. Volumes of AT compartments (by T-1-weighted MRI) and IHL (single-voxel STEAM) were assessed at 1.5T, insulin sensitivity by an oral glucose tolerance test. UI was highest for SCAT(calf) (0.622) and lowest for BM (0.527). Highest PUI was observed for SSCAT (0.108), lowest for BM (0.093). Significant intraindividual differences between UIsbut not PUIsare present for most compartments. There is a non-significant trend for higher UI in males but otherwise no correlation to anthropometric data (age, BMI). A significant negative correlation between UI and AT volume was observed for VAT but for none of the other compartments. Neither UIs nor PUIs show a relation with IHL; insulin sensitivity is significantly correlated to UI in BM (p<0.01). Unsaturation indices in several distinct AT compartments are location dependent. Our cohort showed only moderate gender-related differences, with a trend towards less unsaturated FAs (mainly PUI) in females. In BM, insulin resistant subjects are characterized by a higher UI compared with the insulin sensitive ones. Further studies in larger cohorts are necessary to gain further insight into unsaturation of AT.
AU  - Machann, J.
AU  - Stefan, N.
AU  - Wagner, R.
AU  - Bongers, M.N.*
AU  - Schleicher, E.
AU  - Fritsche, A.
AU  - Häring, H.-U.
AU  - Nikolaou, K.*
AU  - Schick, F.*
C1  - 51770
C2  - 43382
CY  - Hoboken
TI  - Intra- and interindividual variability of fatty acid unsaturation in six different human adipose tissue compartments assessed by 1H-MRS in vivo at 3 T.
JO  - NMR Biomed.
VL  - 30
IS  - 9
PB  - Wiley
PY  - 2017
SN  - 0952-3480
ER  - 

TY  - JOUR
AB  - In the past, spin-echo (SE) echo planar imaging(EPI)-based diffusion tensor imaging (DTI) has been widely used to study the fiber structure of skeletal muscles in vivo. However, this sequence has several shortcomings when measuring restricted diffusion in small animals, such as its sensitivity to susceptibility-related distortions and a relatively short applicable diffusion time. To address these limitations, in the current work, a stimulated echo acquisition mode (STEAM) MRI technique, in combination with fast low-angle shot (FLASH) readout (turbo-STEAM MRI), was implemented and adjusted for DTI in skeletal muscles. Signal preparation using stimulated echoes enables longer effective diffusion times, and thus the detection of restricted diffusion within muscular tissue with intracellular distances up to 100 µm. Furthermore, it has a reduced penalty for fast T2 muscle signal decay, but at the expense of 50% signal loss compared with a SE preparation. Turbo-STEAM MRI facilitates high-resolution DTI of skeletal muscle without introducing susceptibility-related distortions. To demonstrate its applicability, we carried out rabbit in vivo measurements on a human whole-body 3 T scanner. DTI parameters of the shank muscles were extracted, including the apparent diffusion coefficient, fractional anisotropy, eigenvalues and eigenvectors. Eigenvectors were used to calculate maps of structural parameters, such as the planar index and the polar coordinates θ and ϕ of the largest eigenvector. These parameters were compared between three muscles. θ and ϕ showed clear differences between the three muscles, reflecting different pennation angles of the underlying fiber structures. Fiber tractography was performed to visualize and analyze the architecture of skeletal pennate muscles. Optimization of tracking parameters and utilization of T2 -weighted images for improved muscle boundary detection enabled the determination of additional parameters, such as the mean fiber length. The presented results support the applicability of turbo-STEAM MRI as a promising method for quantitative DTI analysis and fiber tractography in skeletal muscles.
AU  - Hiepe, P.*
AU  - Herrmann, K.H.*
AU  - Güllmar, D.*
AU  - Ros, C.*
AU  - Siebert, T.*
AU  - Blickhan, R.*
AU  - Hahn, K.
AU  - Reichenbach, J.R.*
C1  - 28114
C2  - 32947
SP  - 146-157
TI  - Fast low-angle shot diffusion tensor imaging with stimulated echo encoding in the muscle of rabbit shank.
JO  - NMR Biomed.
VL  - 27
IS  - 2
PB  - Wiley-Blackwell
PY  - 2014
SN  - 0952-3480
ER  - 

TY  - JOUR
AB  - Visceral adipose tissue (VAT) is thought to play an important role in the pathogenesis of obesity and insulin resistance. However, little is known about the composition of VAT with regard to the amount of mono- (MUFAs) and polyunsaturated fatty acids (PUFAs) in triglycerides. Volume-selective MRS was performed in addition to MRI for the quantification of VAT. Analysis comprised proton signals from the vinyl-H group (H-C = C-H), including protons from MUFA + PUFA, and diallylic-H, i.e. methylene-interrupted PUFAs. The methyl (-CH(3) ) resonance, which is the only peak with a defined number of protons/triglyceride (n = 9), served as reference. Twenty male subjects participated in this prospective study and underwent MRS of VAT on a 3-T whole-body unit. Spectra were recorded by a single-voxel stimulated echo acquisition mode (STEAM) technique (TE/TM/TR = 20/10/4000 ms; volume of interest between 20 × 25 × 20 and 30 × 30 × 20 mm³; 48-80 acquisitions depending on the size of the volume of interest; bandwidth, 1200 Hz). Post-processing was performed by a Java-based magnetic resonance user interface (jMRUI; AMARES). The volume of VAT was quantified in a separate session on a 1.5-T imager a few days prior to the MRS session by T(1) -weighted imaging. The relative amount of VAT was calculated as a percentage of body weight (%VAT). Ratios of vinyl-H to -CH(3) and diallylic-H to -CH(3) were calculated. All spectra recorded from VAT were of high quality, enabling reliable quantification of the mentioned resonances. %VAT and vinyl-H/CH(3) varied over a broad range (2.8-8.3% and 0.45-0.64, respectively). A strong negative correlation between %VAT and vinyl-H/CH(3) was found (r = -0.92), whereas diallylic-H/CH(3) alone was clearly less well correlated with %VAT (r = -0.21). The composition of VAT shows strong interindividual variations. The greater the total amount of VAT, the less unsaturated the fatty acids. This is a preliminary result in mainly obese male subjects, and it remains to be determined whether this correlation holds for other cohorts of different age, gender and body mass index. Furthermore, changes in VAT composition during weight loss or different forms of diet have yet to be examined.
AU  - Machann, J.
AU  - Stefan, N.
AU  - Schabel, C.*
AU  - Schleicher, E.D.
AU  - Fritsche, A.
AU  - Würslin, C.*
AU  - Häring, H.-U.
AU  - Claussen, C.D.*
AU  - Schick, F.*
C1  - 11141
C2  - 30516
SP  - 232-236
TI  - Fraction of unsaturated fatty acids in Visceral Adipose Tissue (VAT) is lower in subjects with high total VAT volume - a combined 1H MRS and volumetric MRI study in male subjects.
JO  - NMR Biomed.
VL  - 26
IS  - 2
PB  - Wiley-Blackwell
PY  - 2013
SN  - 0952-3480
ER  - 

TY  - JOUR
AB  - Changes in breathing change the concentration of oxygen and carbon dioxide in arterial blood resulting in changes in cerebral blood flow (CBF). This mechanism can be described by the cerebral vascular response (CVR), which has been shown to be altered in different physiological and pathophysiological states. CBF maps of grey matter (GM) were determined with a pulsed arterial spin labelling technique at 3 T in a group of 19 subjects under baseline conditions, hypoxia, and hypercapnia. Experimental conditions allowed a change in either arterial oxygen (hypoxia) or carbon dioxide (hypercapnia) concentration compared with the baseline, leaving the other variable constant, in order to separate the effects of these two variables. From these results, maps were calculated showing the regional distribution of the CVR to hypoxia and hypercapnia in GM. Maps of CVR to hypoxia showed very high intra-subject variations, with some GM regions exhibiting a positive response and others a negative response. Per 10% decrease in arterial oxygen saturation, there was a statistically significant 7.0 +/- 2.9% (mean +/- SEM) increase in GM-CBF for the group. However, 70% of subjects showed an overall positive CVR (positive responders), and the remaining 30% an overall negative CVR (negative responders). Maps of CVR to hypercapnia showed less intra-subject variation. Per 1 mm Hg increase in partial pressure of end-tidal carbon dioxide, there was a statistically significant 5.8 +/- 0.9% increase in GM-CBF, all subjects showing an overall positive CVR. As the brain is particularly vulnerable to hypoxia, a condition associated with cardiorespiratory diseases, CVR maps may help in the clinic to identify the areas most prone to damage because of a reduced CVR.
AU  - Nöth, U.
AU  - Kotajima, F.*
AU  - Deichmann, R.*
AU  - Turner, R.*
AU  - Corfield, D.R.*
C1  - 3661
C2  - 25303
SP  - 464-472
TI  - Mapping of the cerebral vascular response to hypoxia and hypercapnia using quantitative perfusion MRI at 3 T.
JO  - NMR Biomed.
VL  - 21
IS  - 5
PB  - Wiley-Blackwell
PY  - 2008
SN  - 0952-3480
ER  -