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  • 1
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    T 2 relaxation time of the normal-appearing white matter is related to the cognitive status in cerebral small vessel disease
    SAGE Publications ; 2021
    In:  Journal of Cerebral Blood Flow & Metabolism Vol. 41, No. 7 ( 2021-07), p. 1767-1777
    Details
    In: Journal of Cerebral Blood Flow & Metabolism, SAGE Publications, Vol. 41, No. 7 ( 2021-07), p. 1767-1777
    Abstract: Previous diffusion tensor imaging (DTI) studies indicate that impaired microstructural integrity of the normal-appearing white matter (NAWM) is related to cognitive impairment in cerebral small vessel disease (SVD). This study aimed to investigate whether quantitative T 2 relaxometry is a suitable imaging biomarker for the assessment of tissue changes related to cognitive abnormalities in patients with SVD. 39 patients and 18 age-matched healthy control subjects underwent 3 T magnetic resonance imaging (MRI) with T2-weighted multiple spin echo sequences for T 2 relaxometry and DTI sequences, as well as comprehensive cognitive assessment. Averaged quantitative T 2 , fractional anisotropy (FA) and mean diffusivity (MD) were determined in the NAWM and related to cognitive parameters controlling for age, normalized brain volume, white matter hyperintensity volume and other conventional SVD markers. In SVD patients, quantitative T 2 values were significantly increased compared to controls (p = 0.002) and significantly negatively correlated with the global cognitive performance (r= –0.410, p = 0.014) and executive function (r= –0.399, p = 0.016). DTI parameters did not correlate with cognitive function. T 2 relaxometry of the NAWM seems to be sensitive to microstructural tissue damage associated with cognitive impairment in SVD and might be a promising imaging biomarker for evaluation of disease progression and possible effects of therapeutic interventions.
    Type of Medium: Online Resource
    ISSN: 0271-678X , 1559-7016
    URL: Article
    DOI: 10.1177/0271678X20972511
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2021
    detail.hit.zdb_id: 2039456-1
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  • 2
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    Quantitative in vivo T2 mapping using fast spin echo techniques – A linear correction procedure
    Elsevier BV ; 2017
    In:  NeuroImage Vol. 157 ( 2017-08), p. 476-485
    Details
    In: NeuroImage, Elsevier BV, Vol. 157 ( 2017-08), p. 476-485
    Type of Medium: Online Resource
    ISSN: 1053-8119
    URL: Article
    DOI: 10.1016/j.neuroimage.2017.06.017
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2017
    detail.hit.zdb_id: 1471418-8
    SSG: 5,2
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  • 3
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    Topographic Mapping of Isolated Thalamic Infarcts Using Vascular and Novel Probabilistic Functional Thalamic Landmarks
    Springer Science and Business Media LLC ; 2023
    In:  Clinical Neuroradiology Vol. 33, No. 2 ( 2023-06), p. 435-444
    Details
    In: Clinical Neuroradiology, Springer Science and Business Media LLC, Vol. 33, No. 2 ( 2023-06), p. 435-444
    Abstract: We aimed to re-evaluate the relationship between thalamic infarct (TI) localization and clinical symptoms using a vascular (VTM) and a novel functional territorial thalamic map (FTM). Methods Magnetic resonance imaging (MRI) and clinical data of 65 patients with isolated TI were evaluated (female n  = 23, male n  = 42, right n  = 23, left n  = 42). A VTM depicted the known seven thalamic vascular territories (VT: inferolateral, anterolateral, inferomedial, posterior, central, anteromedian, posterolateral). An FTM was generated from a probabilistic thalamic nuclei atlas to determine six functionally defined territories (FT: anterior: memory/emotions; ventral: motor/somatosensory/language; medial: behavior/emotions/nociception, oculomotor; intralaminar: arousal/pain; lateral: visuospatial/somatosensory/conceptual and analytic thinking; posterior: audiovisual/somatosensory). Four neuroradiologists independently assigned diffusion-weighted imaging (DWI) lesions to the territories mapped by the VTM and FTM. Findings were correlated with clinical features. Results The most frequent symptom was a hemisensory syndrome (58%), which was not specific for any territory. A co-occurrence of hemisensory syndrome and hemiparesis had positive predictive values (PPV) of 76% and 82% for the involvement of the inferolateral VT and ventral FT, respectively. Thalamic aphasia had a PPV of 63% each for involvement of the anterolateral VT and ventral FT. Neglect was associated with involvement of the inferolateral VT/ventral FT. Interrater reliability for the assignment of DWI lesions to the VTM was fair (κ = 0.36), but good (κ = 0.73) for the FTM. Conclusion The FTM revealed a greater reproducibility for the topographical assignment of TI than the VTM. Sensorimotor hemiparesis and neglect are predictive for a TI in the inferolateral VT/ventral FT. The hemisensory syndrome alone does not allow any topographical assignment.
    Type of Medium: Online Resource
    ISSN: 1869-1439 , 1869-1447
    URL: Article
    DOI: 10.1007/s00062-022-01225-3
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2023
    detail.hit.zdb_id: 2232347-8
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  • 4
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    The pH sensitivity of APT‐CEST using phosphorus spectroscopy as a reference method
    Wiley ; 2019
    In:  NMR in Biomedicine Vol. 32, No. 11 ( 2019-11)
    Details
    In: NMR in Biomedicine, Wiley, Vol. 32, No. 11 ( 2019-11)
    Abstract: The pH value is a potential physiological marker for clinical diagnosis as it is altered in pathologies such as tumors. While intracellular pH can be measured noninvasively via phosphorus spectroscopy ( 31 P MRSI), Amide Proton Transfer‐Chemical Exchange Saturation Transfer (APT‐CEST) MRI has been suggested as an alternative method for pH quantification. To assess the suitability of APT‐CEST contrast for pH quantification, two approaches (magnetization transfer ratio asymmetry [MTR asym ] and Lorentzian difference analysis [LDA] ) for analyzing the Z‐spectrum have been correlated with pH values obtained by 31 P MRSI. Fourteen patients with glioblastoma and 12 healthy controls were included. In contrast to MTR asym , the LDA is modeling the direct water saturation and the semi‐solid magnetization transfer, allowing a separate evaluation of the aliphatic nuclear Overhauser effect and the APT‐CEST. The results of our study show that the pH values obtained by 31 P MRSI correspond well with both methods describing the APT‐CEST contrast. Two‐sample t‐test showed significant differences in MTR asym , LDA and pH obtained by 31 P MRSI for regions of interest in glioblastoma, contralateral control areas and normal appearing white matter ( P   〈  0.001). A slightly improved correlation between the amide signal and pH was found after performing LDA ( r  = 0.78) compared with MTR asym ( r  = 0.70). While both methods can be used to monitor pH changes, the LDA approach appears to be better suited.
    Type of Medium: Online Resource
    ISSN: 0952-3480 , 1099-1492
    URL: Issue
    URL: Article
    DOI: 10.1002/nbm.v32.11
    DOI: 10.1002/nbm.4125
    Language: English
    Publisher: Wiley
    Publication Date: 2019
    detail.hit.zdb_id: 2002003-X
    detail.hit.zdb_id: 1000976-0
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  • 5
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    A fast and novel method for amide proton transfer‐chemical exchange saturation transfer multislice imaging
    Wiley ; 2021
    In:  NMR in Biomedicine Vol. 34, No. 7 ( 2021-07)
    Details
    In: NMR in Biomedicine, Wiley, Vol. 34, No. 7 ( 2021-07)
    Abstract: Amide proton transfer‐chemical exchange saturation transfer (APT‐CEST) imaging provides important information for the diagnosis and monitoring of tumors. For such analysis, complete coverage of the brain is advantageous, especially when registration is performed with other magnetic resonance (MR) modalities, such as MR spectroscopy (MRS). However, the acquisition of Z‐spectra across several slices via multislice imaging may be time‐consuming. Therefore, in this paper, we present a new approach for fast multislice imaging, allowing us to acquire 16 slices per frequency offset within 8 s. The proposed fast CEST‐EPI sequence employs a presaturation module, which drives the magnetization into the steady‐state equilibrium for the first frequency offset. A second module, consisting of a single CEST pulse (for maintaining the steady‐state) followed by an EPI acquisition, passes through a loop to acquire multiple slices and adjacent frequency offsets. Thus, the whole Z‐spectrum can be recorded much faster than the conventional saturation scheme, which employs a presaturation for each single frequency offset. The validation of the CEST sequence parameters was performed by using the conventional saturation scheme. Subsequently, the proposed and a modified version of the conventional CEST sequence were compared in vitro on a phantom with different T1 times and in vivo on a brain tumor patient. No significant differences between both sequences could be found in vitro. The in vivo data yielded almost identical MTR asym contrasts for the white and gray matter as well as for tumor tissue. Our results show that the proposed fast CEST‐EPI sequence allows for rapid data acquisition and provides similar CEST contrasts as the modified conventional scheme while reducing the scanning time by approximately 50%.
    Type of Medium: Online Resource
    ISSN: 0952-3480 , 1099-1492
    URL: Issue
    URL: Article
    DOI: 10.1002/nbm.v34.7
    DOI: 10.1002/nbm.4524
    Language: English
    Publisher: Wiley
    Publication Date: 2021
    detail.hit.zdb_id: 2002003-X
    detail.hit.zdb_id: 1000976-0
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  • 6
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    Image_1.TIF
    Frontiers Media SA ; 2022
    In:  Frontiers in Neurology Vol. 13 ( 2022-8-3)
    Details
    In: Frontiers in Neurology, Frontiers Media SA, Vol. 13 ( 2022-8-3)
    Abstract: Hypertrophic olivary degeneration (HOD) is a pathology of the inferior olivary nucleus (ION) that occurs after injuries to the Guillain-Mollaret triangle (GMT). Lacking a diagnostic gold standard, diagnosis is usually based on T2 or FLAIR imaging and expert rating. To facilitate precise HOD diagnosis in future studies, we assessed the reliability of this rater-based approach and explored alternative, quantitative analysis. Methods Patients who had suffered strokes in the GMT and a matched control group prospectively underwent an MRI examination including T2, FLAIR, and proton density (PD). Diffusion tensor imaging (DTI) was additionally performed in the patient group. The presence of HOD was assessed on FLAIR, T2, and PD separately by 3 blinded reviewers. Employing an easily reproducible segmentation approach, relative differences in intensity, fractional anisotropy (FA), and mean diffusivity (MD) between both IONs were calculated. Results In total, 15 patients were included in this study. The interrater reliability was best for FLAIR, followed by T2 and PD (Fleiss κ = 0.87 / 0.77 / 0.65). The 3 raters diagnosed HOD in 38–46% (FLAIR), 40–47% (T2), and 53–67% (PD) of patients. False-positive findings in the control group were less frequent in T2 than in PD and FLAIR (2.2% / 8.9% / 6.7%). In 53% of patients, the intensity difference between both IONs on PD was significantly increased in comparison with the control group. These patients also showed significantly decreased FA and increased MD. Conclusion While the rater-based approach yielded the best performance on T2 imaging, a quantitative, more sensitive HOD diagnosis based on ION intensities in PD and DTI imaging seems possible.
    Type of Medium: Online Resource
    ISSN: 1664-2295
    URL: Article
    URL: Article
    DOI: 10.3389/fneur.2022.950191
    DOI: 10.3389/fneur.2022.950191.s001
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2022
    detail.hit.zdb_id: 2564214-5
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  • 7
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    Comprehensive 7 T CEST: A clinical MRI protocol covering multiple exchange rate regimes
    Wiley ; 2024
    In:  NMR in Biomedicine
    Details
    In: NMR in Biomedicine, Wiley
    Abstract: Chemical exchange saturation transfer (CEST) is a magnetic resonance (MR) imaging method providing molecular image contrasts based on indirect detection of low concentrated solutes. Previous CEST studies focused predominantly on the imaging of single CEST exchange regimes (e.g., slow, intermediate or fast exchanging groups). In this work, we aim to establish a so‐called comprehensive CEST protocol for 7 T, covering the different exchange regimes by three saturation B1 amplitude regimes: low, intermediate and high. We used the results of previous publications and our own simulations in pulseq‐CEST to produce a 7 T CEST protocol that has sensitivity to these three B1 regimes. With postprocessing optimization (simultaneous mapping of water shift and B1, B0‐fitting, multiple interleaved mode saturation B1 correction, neural network employment (deepCEST) and analytical input feature reduction), we are able to shorten our initially 40 min protocol to 15 min and generate six CEST contrast maps simultaneously. With this protocol, we measured four healthy subjects and one patient with a brain tumor. We established a comprehensive CEST protocol for clinical 7 T MRI, covering three different B1 amplitude regimes. We were able to reduce the acquisition time significantly by more than 50%, while still maintaining decent image quality and contrast in healthy subjects and one patient with a tumor. Our protocol paves the way to perform comprehensive CEST studies in clinical scan times for hypothesis generation regarding molecular properties of certain pathologies, for example, ischemic stroke or high‐grade brain tumours.
    Type of Medium: Online Resource
    ISSN: 0952-3480 , 1099-1492
    URL: Article
    DOI: 10.1002/nbm.5096
    Language: English
    Publisher: Wiley
    Publication Date: 2024
    detail.hit.zdb_id: 2002003-X
    detail.hit.zdb_id: 1000976-0
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  • 8
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    ‘Hippocampal innate inflammatory gliosis only’ in pharmacoresistant temporal lobe epilepsy
    Oxford University Press (OUP) ; 2023
    In:  Brain Vol. 146, No. 2 ( 2023-02-13), p. 549-560
    Details
    In: Brain, Oxford University Press (OUP), Vol. 146, No. 2 ( 2023-02-13), p. 549-560
    Abstract: Drug-resistant mesial-temporal lobe epilepsy is a devastating disease with seizure onset in the hippocampal formation. A fraction of hippocampi samples from epilepsy-surgical procedures reveals a peculiar histological pattern referred to as ‘gliosis only’ with unresolved pathogenesis and enigmatic sequelae. Here, we hypothesize that ‘gliosis only’ represents a particular syndrome defined by distinct clinical and molecular characteristics. We curated an in-depth multiparameter integration of systematic clinical, neuropsychological as well as neuropathological analysis from a consecutive cohort of 627 patients, who underwent hippocampectomy for drug-resistant temporal lobe epilepsy. All patients underwent either classic anterior temporal lobectomy or selective amygdalohippocampectomy. On the basis of their neuropathological exam, patients with hippocampus sclerosis and ‘gliosis only’ were characterized and compared within the whole cohort and within a subset of matched pairs. Integrated transcriptional analysis was performed to address molecular differences between both groups. ‘Gliosis only’ revealed demographics, clinical and neuropsychological outcome fundamentally different from hippocampus sclerosis. ‘Gliosis only’ patients had a significantly later seizure onset (16.3 versus 12.2 years, P = 0.005) and worse neuropsychological outcome after surgery compared to patients with hippocampus sclerosis. Epilepsy was less amendable by surgery in ‘gliosis only’ patients, resulting in a significantly worse rate of seizure freedom after surgery in this subgroup (43% versus 68%, P = 0.0001, odds ratio = 2.8, confidence interval 1.7–4.7). This finding remained significant after multivariate and matched-pairs analysis. The ‘gliosis only’ group demonstrated pronounced astrogliosis and lack of significant neuronal degeneration in contrast to characteristic segmental neuron loss and fibrillary astrogliosis in hippocampus sclerosis. RNA-sequencing of gliosis only patients deciphered a distinct transcriptional programme that resembles an innate inflammatory response of reactive astrocytes. Our data indicate a new temporal lobe epilepsy syndrome for which we suggest the term ‘Innate inflammatory gliosis only’. ‘Innate inflammatory gliosis only’ is characterized by a diffuse gliosis pattern lacking restricted hippocampal focality and is poorly controllable by surgery. Thus, ‘innate inflammatory gliosis only’ patients need to be clearly identified by presurgical examination paradigms of pharmacoresistant temporal lobe epilepsy patients; surgical treatment of this subgroup should be considered with great precaution. ‘Innate inflammatory gliosis only’ requires innovative pharmacotreatment strategies.
    Type of Medium: Online Resource
    ISSN: 0006-8950 , 1460-2156
    URL: Article
    DOI: 10.1093/brain/awac293
    RVK:
    XA 10000
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 1474117-9
    SSG: 12
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  • 9
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    T 1 mapping with the variable flip angle technique: A simple correction for insufficient spoiling of transverse magnetization
    Wiley ; 2018
    In:  Magnetic Resonance in Medicine Vol. 79, No. 6 ( 2018-06), p. 3082-3092
    Details
    In: Magnetic Resonance in Medicine, Wiley, Vol. 79, No. 6 ( 2018-06), p. 3082-3092
    Abstract: The variable flip angle method derives T 1 maps from radiofrequency‐spoiled gradient‐echo data sets, acquired with different flip angles α. Because the method assumes validity of the Ernst equation, insufficient spoiling of transverse magnetization yields errors in T 1 estimation, depending on the chosen radiofrequency‐spoiling phase increment (Δϕ). This paper presents a versatile correction method that uses modified flip angles α' to restore the validity of the Ernst equation. Methods Spoiled gradient‐echo signals were simulated for three commonly used phase increments Δϕ (50°/117°/150°), different values of α, repetition time (TR), T 1 , and a T 2 of 85 ms. For each parameter combination, α′ (for which the Ernst equation yielded the same signal) and a correction factor C Δϕ (α, TR, T 1 ) = α′/α were determined. C Δϕ was found to be independent of T 1 and fitted as polynomial C Δϕ (α, TR), allowing to calculate α′ for any protocol using this Δϕ. The accuracy of the correction method for T 2 values deviating from 85 ms was also determined. The method was tested in vitro and in vivo for variable flip angle scans with different acquisition parameters. Results The technique considerably improved the accuracy of variable flip angle–based T 1 maps in vitro and in vivo. Conclusions The proposed method allows for a simple correction of insufficient spoiling in gradient‐echo data. The required polynomial parameters are supplied for three common Δϕ. Magn Reson Med 79:3082–3092, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
    Type of Medium: Online Resource
    ISSN: 0740-3194 , 1522-2594
    URL: Issue
    URL: Article
    DOI: 10.1002/mrm.v79.6
    DOI: 10.1002/mrm.26979
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 1493786-4
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  • 10
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    Isolated thalamic stroke – analysis of clinical characteristics and asymmetry of lesion distribution in a retrospective cohort study
    Springer Science and Business Media LLC ; 2021
    In:  Neurological Research and Practice Vol. 3, No. 1 ( 2021-12)
    Details
    In: Neurological Research and Practice, Springer Science and Business Media LLC, Vol. 3, No. 1 ( 2021-12)
    Abstract: More patients with left-hemispheric than right-hemispheric strokes are admitted to hospitals. This is due to the easier recognition of cortical symptoms of the dominant-hemisphere. The thalamus constitutes a “micro-model” of the brain cortex with structure-function relationships known to be asymmetric, especially for language, memory, and visuo-spatial neurocognitive functions. The goal of this study was to characterize clinical symptoms and lesion distribution patterns of patients with acute isolated thalamic stroke (ITS) and to evaluate whether left-sided lesions are overrepresented in the hospital. Methods We performed a radiological database search including all brain scans performed in the Center of Neurology and Neurosurgery of the University Hospital Frankfurt between 2010 and 2019. A total of 5733 patients presenting with acute ischemic stroke were screened for ITS. Based on the MRI data, a lesion-overlap map was then generated to visualize the ITS lesion distribution. Results Fifty-eight patients with unilateral ITS were identified. A majority of 38 patients (65.5%) showed left-sided ITS, whereas only 20 patients (34.5%) had right-sided ITS ( p  = 0.012). A particular difference was found for ITS lesions in the anterior thalamus of the anterolateral ( n  = 10) and anteromedian ( n  = 3) vascular territory, which were located in the left thalamus in 85% of patients ( p  = 0.011). No distribution difference was found for ITS lesions in the inferomedial ( n  = 7), central ( n  = 8), inferolateral ( n  = 23) and posterior (n = 7) vascular territories. The neuropsychological symptoms of thalamic aphasia ( n  = 8), neurocognitive impairment ( n  = 6), behavioral changes ( n  = 2), neglect (n = 2) and memory deficits ( n  = 3) were described predominantly in patients with left-sided ITS ( p   〈  0.01). In contrast, other stroke symptoms (e.g., sensorimotor hemi-syndromes) did not reveal a side preponderance. Conclusions The better recognizability of left anterior compared to right anterior thalamic stroke symptoms may have an impact on the frequency in which ITS patients are admitted to the hospital. Clinical characteristics of right anterior thalamic stroke should therefore be further investigated, and diagnostic instruments towards their detection be identified.
    Type of Medium: Online Resource
    ISSN: 2524-3489
    URL: Article
    DOI: 10.1186/s42466-021-00148-7
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2021
    detail.hit.zdb_id: 2947493-0
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