TY  - JOUR
AB  - OBJECTIVE: Reliable image quality assessment is crucial for evaluating new motion correction methods for magnetic resonance imaging. We compare the performance of common reference-based and reference-free image quality metrics on unique datasets with real motion artifacts, and analyze the metrics' robustness to typical pre-processing techniques. MATERIALS AND METHODS: We compared five reference-based and five reference-free metrics on brain data acquired with and without intentional motion (2D and 3D sequences). The metrics were recalculated seven times with varying pre-processing steps. Spearman correlation coefficients were computed to assess the relationship between image quality metrics and radiological evaluation. RESULTS: All reference-based metrics showed strong correlation with observer assessments. Among reference-free metrics, Average Edge Strength offers the most promising results, as it consistently displayed stronger correlations across all sequences compared to the other reference-free metrics. The strongest correlation was achieved with percentile normalization and restricting the metric values to the skull-stripped brain region. In contrast, correlations were weaker when not applying any brain mask and using min-max or no normalization. DISCUSSION: Reference-based metrics reliably correlate with radiological evaluation across different sequences and datasets. Pre-processing significantly influences correlation values. Future research should focus on refining pre-processing techniques and exploring approaches for automated image quality evaluation.
AU  - Marchetto, E.*
AU  - Eichhorn, H.
AU  - Gallichan, D.*
AU  - Schnabel, J.A.
AU  - Ganz, M.*
C1  - 74890
C2  - 57693
CY  - One New York Plaza, Suite 4600, New York, Ny, United States
TI  - Agreement of image quality metrics with radiological evaluation in the presence of motion artifacts.
JO  - Magn. Reson. Mater. Phys. Biol. Med.
PB  - Springer
PY  - 2025
SN  - 0968-5243
ER  - 

TY  - JOUR
AB  - OBJECTIVE: To prepare and analyze soy-lecithin-agar gels for non-toxic relaxometry phantoms with tissue-like relaxation times at 3T. METHODS: Phantoms mimicking the relaxation times of various tissues (gray and white matter, kidney cortex and medulla, spleen, muscle, liver) were built and tested with a clinical 3T whole-body MR scanner. Simple equations were derived to calculate the appropriate concentrations of soy lecithin and agar in aqueous solutions to achieve the desired relaxation times. Phantoms were tested for correspondence between measurements and calculated T1 and T2 values, reproducibility, spatial homogeneity, and temporal stability. T1 and T2 mapping techniques and a 3D T1-weighted sequence with high spatial resolution were applied. RESULTS: Except for the liver relaxation phantom, all phantoms were successfully and reproducibly produced. Good agreement was found between the targeted and measured relaxation times. The percentage deviations from the targeted relaxation times were less than 3% for T1 and less than 6.5% for T2. In addition, the phantoms were homogeneous and had little to no air bubbles. However, the phantoms were unstable over time: after a storage period of 4 weeks, mold growth and also changes in relaxation times were detected in almost all phantoms. CONCLUSION: Soy-lecithin-agar gels are a non-toxic material for the construction of relaxometry phantoms with tissue-like relaxation times. They are easy to prepare, inexpensive and allow independent adjustment of T1 and T2. However, there is still work to be done to improve the long-term stability of the phantoms.
AU  - Fritz, V.
AU  - Eisele, S.*
AU  - Martirosian, P.*
AU  - Machann, J.
AU  - Schick, F.*
C1  - 70646
C2  - 55795
CY  - One New York Plaza, Suite 4600, New York, Ny, United States
TI  - A straightforward procedure to build a non-toxic relaxometry phantom with desired T1 and T2 times at 3T.
JO  - Magn. Reson. Mater. Phys. Biol. Med.
PB  - Springer
PY  - 2024
SN  - 0968-5243
ER  - 

TY  - JOUR
AB  - Objective: To provide a basis for the selection of suitable emulsifiers in oil-in-water emulsions used as tissue analogs for MRI experiments. Three different emulsifiers were investigated with regard to their ability to stabilize tissue-like oil-in-water emulsions. Furthermore, MR signal properties of the emulsifiers themselves and influences on relaxation times and ADC values of the aqueous phase were investigated. Materials and methods: Polysorbate 60, sodium dodecyl sulfate (SDS) and soy lecithin were used as emulsifiers. MR characteristics of emulsifiers were assessed in aqueous solutions and their function as a stabilizer was examined in oil-in-water emulsions of varying fat content (10, 20, 30, 40, 50%). Stability and homogeneity of the oil-in-water emulsions were evaluated with a delay of 3 h and 9 h after preparation using T1 mapping and visual control. Signal properties of the emulsifiers were investigated by 1H-MRS in aqueous emulsifier solutions. Relaxometry and diffusion weighted MRI (DWI) were performed to investigate the effect of various emulsifier concentrations on relaxation times (T1 and T2) and ADC values of aqueous solutions. Results: Emulsions stabilized by polysorbate 60 or soy lecithin were stable and homogeneous across all tested fat fractions. In contrast, emulsions with SDS showed a significantly lower stability and homogeneity. Recorded T1 maps revealed marked creaming of oil droplets in almost all of the emulsions with SDS. The spectral analysis showed several additional signals for polysorbate and SDS. However, lecithin remained invisible in 1H-MRS. Relaxometry and DWI revealed different influences of the emulsifiers on water: Polysorbate and SDS showed only minor effects on relaxation times and ADC values of aqueous solutions, whereas lecithin showed a strong decrease in both relaxation times (r1,lecithin = 0.11 wt.%−1 s−1, r2,lecithin = 0.57 wt.%−1 s−1) and ADC value (Δ(ADC)lecithin = − 0.18 × 10–3 mm2/s⋅wt.%) with increasing concentration. Conclusion: Lecithin is suggested as the preferred emulsifier of oil-in-water emulsions in MRI as it shows a high stabilizing ability and remains invisible in MRI experiments. In addition, lecithin is suitable as an alternative means of adjusting relaxation times and ADC values of water.
AU  - Fritz, V.*
AU  - Martirosian, P.*
AU  - Machann, J.
AU  - Daniels, R.*
AU  - Schick, F.
C1  - 63381
C2  - 51512
CY  - One New York Plaza, Suite 4600, New York, Ny, United States
TI  - A comparison of emulsifiers for the formation of oil-in-water emulsions: Stability of the emulsions within 9 h after production and MR signal properties.
JO  - Magn. Reson. Mater. Phys. Biol. Med.
PB  - Springer
PY  - 2021
SN  - 0968-5243
ER  - 

TY  - JOUR
AB  - To evaluate and compare conventional T1-weighted 2D turbo spin echo (TSE), T1-weighted 3D volumetric interpolated breath-hold examination (VIBE), and two-point 3D Dixon-VIBE sequences for automatic segmentation of visceral adipose tissue (VAT) volume at 3 Tesla by measuring and compensating for errors arising from intensity nonuniformity (INU) and partial volume effects (PVE). The body trunks of 28 volunteers with body mass index values ranging from 18 to 41.2 kg/m(2) (30.02 +/- 6.63 kg/m(2)) were scanned at 3 Tesla using three imaging techniques. Automatic methods were applied to reduce INU and PVE and to segment VAT. The automatically segmented VAT volumes obtained from all acquisitions were then statistically and objectively evaluated against the manually segmented (reference) VAT volumes. Comparing the reference volumes with the VAT volumes automatically segmented over the uncorrected images showed that INU led to an average relative volume difference of -59.22 +/- 11.59, 2.21 +/- 47.04, and -43.05 +/- 5.01 % for the TSE, VIBE, and Dixon images, respectively, while PVE led to average differences of -34.85 +/- 19.85, -15.13 +/- 11.04, and -33.79 +/- 20.38 %. After signal correction, differences of -2.72 +/- 6.60, 34.02 +/- 36.99, and -2.23 +/- 7.58 % were obtained between the reference and the automatically segmented volumes. A paired-sample two-tailed t test revealed no significant difference between the reference and automatically segmented VAT volumes of the corrected TSE (p = 0.614) and Dixon (p = 0.969) images, but showed a significant VAT overestimation using the corrected VIBE images. Under similar imaging conditions and spatial resolution, automatically segmented VAT volumes obtained from the corrected TSE and Dixon images agreed with each other and with the reference volumes. These results demonstrate the efficacy of the signal correction methods and the similar accuracy of TSE and Dixon imaging for automatic volumetry of VAT at 3 Tesla.
AU  - Fallah, F.*
AU  - Machann, J.
AU  - Martirosian, P.*
AU  - Bamberg, F.*
AU  - Schick, F.*
AU  - Yang, B.*
C1  - 51031
C2  - 42909
CY  - New York
SP  - 139-151
TI  - Comparison of T1-weighted 2D TSE, 3D SPGR, and two-point 3D Dixon MRI for automated segmentation of visceral adipose tissue at 3 Tesla.
JO  - Magn. Reson. Mater. Phys. Biol. Med.
VL  - 30
IS  - 2
PB  - Springer
PY  - 2017
SN  - 0968-5243
ER  - 

TY  - JOUR
AU  - Hahn, K.R.
AU  - Sandan, K.*
AU  - Rodenacker, K.
AU  - Prigarin, S.M.
C1  - 5727
C2  - 28353
TI  - Novel algorithms to measure complexity in the human brain and to detect statistically significant complexity differences.
JO  - Magn. Reson. Mater. Phys. Biol. Med.
VL  - 19
PY  - 2006
SN  - 0968-5243
ER  -