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  • 1
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 11, No. 1 ( 2021-04-01)
    Abstract: The extrinsic foot muscles are essentially for controlling the movement path but our knowledge of their behavior during prolonged running is still very limited. Therefore, this study analyzed the time-course of muscle activation using T2 mapping during 75 min of running. In this prospective study, 19 recreational active runners completed 75 min of treadmill running at a constant speed. Interleaved T2 mapping sequences were acquired and segmented at timepoints 0, 2.5, 5, 10, 15, 45, and 75 min. ANOVA for repeated measurements followed by a Tukey post hoc test and Pearson correlation between running speed and initial signal increase at 2.5 min were calculated. All muscles showed a significant signal increase between baseline and 2.5 min (e.g. medial gastrocnemius: + 15.48%; p   〈  0.01). This was followed by a plateau phase till 15 min for all but the extensor digitorum longus muscle and a significant decrease at 45 or 75 min for all muscles (all p   〈  0.05). Correlation between running speed and signal increase was negative for all muscles and significant for both gastrocnemii (e.g. medial: r =  − 0.57, p  = 0.0104) and soleus (r =  − 0.47, p  = 0.0412). The decrease of relaxation times times in the later running phases was less pronounced for faster runners (≥ 10 km/h). T2 relaxation times do not only decrease after cessation of exercise but already during prolonged running. The lesser initial increase and later decrease in faster runners may indicate training induced changes.
    Type of Medium: Online Resource
    ISSN: 2045-2322
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 2615211-3
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  • 2
    In: European Journal of Radiology, Elsevier BV, Vol. 107 ( 2018-10), p. 76-83
    Type of Medium: Online Resource
    ISSN: 0720-048X
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2018
    detail.hit.zdb_id: 2005350-2
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  • 3
    Online Resource
    Online Resource
    Georg Thieme Verlag KG ; 2018
    In:  RöFo - Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren Vol. 190, No. 07 ( 2018-07), p. 601-609
    In: RöFo - Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren, Georg Thieme Verlag KG, Vol. 190, No. 07 ( 2018-07), p. 601-609
    Abstract: Purpose Contrast-enhanced T1-weighted MR imaging of the liver is typically acquired using breath-hold techniques to reduce motion artifacts and to allow for optimal diagnostic image quality. Insufficient breath-holds during MR data collection can cause severe reduction of image quality up to the point of being non-diagnostic. The aim of this study was to evaluate the subjective and objective clinical image quality of a novel free-breathing radial k-space sampling MR technique. Materials and Methods Consent for this study was given by the local IRB committee. 86 patients who underwent both breath-hold (BH) and free-breathing (FB) late-phase contrast T1w-FS-FFE liver MRI using conventional BH Cartesian (Cartesian-eTHRIVE) and FB “pseudo golden angle” radial k-space sampling (Radial-eTHRIVE) were included in this retrospective analysis. Subjective analysis comprised 5-point Likert scale ratings (1 = very good; 5 = non-diagnostic) for “artifact impact”, “anatomic sharpness”, “vessel sharpness”, “contrast impression”, and “overall diagnostic quality”. Relative signal intensities in different ROIs were compared between Cartesian-eTHRIVE and Radial-eTHRIVE. For statistical differences paired Wilcoxon test and paired t-test have been performed (p  〈  0.05). Results The MR scan time was significantly longer for FB Radial-eTHRIVE (2 min, 54 s) compared to BH Cartesian-eTHRIVE (0 min 15 s). Cartesian-eTHRIVE demonstrated a superior subjective contrast impression and objective measurements revealed an increased lesion-to-liver-contrast for hypointense liver lesions (Hypo-LTLC: 0.33 ± 0.19 vs. 0.20 ± 0.11; p = 0.000), while no difference was observed for hyperintense liver lesions (Hyper-LTLC). Subjective evaluation showed superior anatomic sharpness ratings by both readers for Radial-eTHRIVE. Most importantly, in a subgroup analysis of patients who were unable to perform adequate breath-holds, free-breathing Radial-eTHRIVE still demonstrated good subjective image quality. Conclusion Free-breathing, radial k-space sampling T1w MRI of the liver delivers high diagnostic image quality, especially in patients who are unable to adequately perform breath-hold maneuvers. Thus, Radial-eTHRIVE can be an important clinical alternative in patients with impaired respiration status. Key points  Citation Format
    Type of Medium: Online Resource
    ISSN: 1438-9029 , 1438-9010
    RVK:
    Language: English
    Publisher: Georg Thieme Verlag KG
    Publication Date: 2018
    detail.hit.zdb_id: 2031079-1
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  • 4
    In: European Radiology, Springer Science and Business Media LLC, Vol. 32, No. 1 ( 2022-01), p. 331-345
    Abstract: We examined the effects of aging and of gadolinium-based contrast agent (GBCA) exposure on MRI measurements in brain nuclei of healthy women. Methods This prospective, IRB-approved single-center case-control study enrolled 100 healthy participants of our high-risk screening center for hereditary breast cancer, who had received at least six doses of macrocyclic GBCA (exposed group) or were newly entering the program (GBCA-naïve group). The cutoff “at least six doses” was chosen to be able to include a sufficient number of highly exposed participants. All participants underwent unenhanced 3.0-T brain MRI including quantitative T1, T2, and R2* mapping and T1- and T2-weighted imaging. The relaxation times/signal intensities were derived from region of interest measurements in the brain nuclei performed by a radiologist and a neuroradiologist, both board certified. Statistical analysis was based on descriptive evaluations and uni-/multivariable analyses. Results The participants (exposed group: 49, control group: 51) were aged 42 ± 9 years. In a multivariable model, age had a clear impact on R2* ( p 〈 0.001–0.012), T2 ( p = 0.003–0.048), and T1 relaxation times/signal intensities ( p 〈 0.004–0.046) for the majority of deep brain nuclei, mostly affecting the substantia nigra, globus pallidus (GP), nucleus ruber, thalamus, and dentate nucleus (DN). The effect of prior GBCA administration on T1 relaxation times was statistically significant for the DN, GP, and pons ( p = 0.019–0.037). Conclusions In a homogeneous group of young to middle-aged healthy females aging had an effect on T2 and R2* relaxation times and former GBCA applications influenced the measured T1 relaxation times. Key Points The quantitative T1, T2, and R2* relaxation times measured in women at high risk of developing breast cancer showed characteristic bandwidth for all brain nuclei examined at 3.0-T MRI. The effect of participant age had a comparatively strong impact on R2*, T2, and T1 relaxation times for the majority of brain nuclei examined. The effect of prior GBCA administrations on T1 relaxation times rates was comparatively less pronounced, yielding statistically significant results for the dentate nucleus, globus pallidus, and pons. Summary statement Healthy women with and without previous GBCA-enhanced breast MRI exhibited age-related T2* and T2 relaxation alterations at 3.0 T-brain MRI. T1 relaxation alterations due to prior GBCA administration were comparatively less pronounced.
    Type of Medium: Online Resource
    ISSN: 0938-7994 , 1432-1084
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 1472718-3
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  • 5
    In: Magnetic Resonance in Medicine, Wiley, Vol. 82, No. 2 ( 2019-08), p. 647-657
    Abstract: Respiration induces temporal variations of the main magnetic field B 0 along the spinal cord. These variations are typically not compensated for in velocity quantifications using phase‐contrast MRI. The goal of this study was to analyze errors caused by respiration‐induced B 0 variations in real‐time phase‐contrast echo planar imaging (PCEPI) of cervical cerebrospinal fluid (CSF) velocity measurements and to evaluate this effect for various sequence parameters using numerical simulations. Methods Real‐time B 0 measurements with double gradient echo sequence and PCEPI measurements were acquired in the cervical CSF of 10 healthy subjects. Dynamic phase offsets attributed to respiration‐induced B 0 variations were analyzed by quantifying amplitudes and comparing the temporal behavior with respiratory signals. In experiments and simulations, the influence of the echo time (TE) and the delay between PCEPI images (Δ t ) with respect to respiration on the dynamic phase offsets were investigated. Results A good agreement was found between phase offsets extracted from both acquisition types. Furthermore, respiratory signals qualitatively matched the temporal behavior of the measured phase offsets showing a dependency on subject‐dependent local B 0 distribution and respiration physiology. Simulations revealed residual background phases in PCEPI velocity quantification varying with TE and Δ t . Conclusion Respiration‐induced B 0 variations result in dynamic background phases in real‐time PCEPI velocity quantifications of the CSF in the cervical spine. The current work underlines that these background phases need to be corrected to avoid confounding effects.
    Type of Medium: Online Resource
    ISSN: 0740-3194 , 1522-2594
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 1493786-4
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  • 6
    In: Magnetic Resonance Imaging, Elsevier BV, Vol. 53 ( 2018-11), p. 52-62
    Type of Medium: Online Resource
    ISSN: 0730-725X
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2018
    detail.hit.zdb_id: 1500646-3
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  • 7
    Online Resource
    Online Resource
    Springer Science and Business Media LLC ; 2020
    In:  Fluids and Barriers of the CNS Vol. 17, No. 1 ( 2020-12)
    In: Fluids and Barriers of the CNS, Springer Science and Business Media LLC, Vol. 17, No. 1 ( 2020-12)
    Abstract: 4D flow magnetic resonance imaging (MRI) of CSF can make an important contribution to the understanding of hydrodynamic changes in various neurological diseases but remains limited in clinical application due to long acquisition times. The aim of this study was to evaluate the accuracy of compressed SENSE accelerated MRI measurements of the spinal CSF flow. Methods In 20 healthy subjects 4D flow MRI of the CSF in the cervical spine was acquired using compressed sensitivity encoding [CSE, a combination of compressed sensing and parallel imaging (SENSE) provided by the manufacturer] with acceleration factors between 4 and 10. A conventional scan using SENSE was used as reference. Extracted parameters were peak velocity, absolute net flow, forward flow and backward flow. Bland–Altman analysis was performed to determine the scan-rescan reproducibility and the agreement between SENSE and compressed SENSE. Additionally, a time accumulated flow error was calculated. In one additional subject flow of the spinal canal at the level of the entire spinal cord was assessed. Results Averaged acquisition times were 10:21 min (SENSE), 9:31 min (CSE4), 6:25 min (CSE6), 4:53 min (CSE8) and 3:51 min (CSE10). Acquisition of the CSF flow surrounding the entire spinal cord took 14:40 min. Bland–Altman analysis showed good agreement for peak velocity, but slight overestimations for absolute net flow, forward flow and backward flow ( 〈  1 ml/min) in CSE4–8. Results of the accumulated flow error were similar for CSE4 to CSE8. Conclusion A quantitative analysis of acceleration factors CSE4–10 showed that CSE with an acceleration factor up to 6 is feasible. This allows a scan time reduction of 40% and enables the acquisition and analysis of the CSF flow dynamics surrounding the entire spinal cord within a clinically acceptable scan time.
    Type of Medium: Online Resource
    ISSN: 2045-8118
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2020
    detail.hit.zdb_id: 2595406-4
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  • 8
    In: Journal of Cardiovascular Magnetic Resonance, Elsevier BV, Vol. 22, No. 1 ( 2020-01), p. 8-
    Type of Medium: Online Resource
    ISSN: 1097-6647
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2020
    detail.hit.zdb_id: 2578881-4
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  • 9
    In: Journal of Cardiovascular Magnetic Resonance, Elsevier BV, Vol. 21, No. 1 ( 2019-01), p. 65-
    Type of Medium: Online Resource
    ISSN: 1097-6647
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2019
    detail.hit.zdb_id: 2578881-4
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  • 10
    In: Clinical Neuroradiology, Springer Science and Business Media LLC, Vol. 31, No. 3 ( 2021-09), p. 815-826
    Abstract: To evaluate a novel flow-independent 3D isotropic REACT sequence compared with CE-MRA for the imaging of extracranial arteries in acute ischemic stroke (AIS). Methods This was a retrospective study of 35 patients who underwent a stroke protocol at 3 T including REACT (fixed scan time: 2:46 min) and CE-MRA of the extracranial arteries. Three radiologists evaluated scans regarding vessel delineation, signal, and contrast and assessed overall image noise and artifacts using 5-point scales (5: excellent delineation/no artifacts). Apparent signal- and contrast-to-noise ratios (aSNR/aCNR) were measured for the common carotid artery (CCA), internal carotid artery (ICA, C1 segment), and vertebral artery (V2 segment). Two radiologists graded the degree of proximal ICA stenosis. Results Compared to REACT, CE-MRA showed better delineation for the CCA and ICA (C1 and C2 segments) (median 5, range 2–5 vs. 4, range 3–5; P   〈  0.05). For the ICA (C1 and C2 segments), REACT provided a higher signal (5, range 3–5; P   〈  0.05/4.5, range 3–5; P   〉  0.05 vs. 4, range 2–5) and contrast (5, range 3–5 vs. 4, range 2–5; P   〉  0.05) than CE-MRA. The remaining segments of the blood-supplying vessels showed equal medians. There was no significant difference regarding artifacts, whereas REACT provided significantly lower image noise (4, range 3–5 vs. 4 range 2–5; P   〈  0.05) with a higher aSNR ( P   〈  0.05) and aCNR ( P   〈  0.05) for all vessels combined. For clinically relevant (≥50%) ICA stenosis, REACT achieved a detection sensitivity of 93.75% and a specificity of 100%. Conclusion Given its fast acquisition, comparable image quality to CE-MRA and high sensitivity and specificity for the detection of ICA stenosis, REACT was proven to be a clinically applicable method to assess extracranial arteries in AIS.
    Type of Medium: Online Resource
    ISSN: 1869-1439 , 1869-1447
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 2232347-8
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