Mohr, Alexander

[["dc.bibliographiccitation.firstpage","1905"],["dc.bibliographiccitation.issue","11"],["dc.bibliographiccitation.journal","Human Brain Mapping"],["dc.bibliographiccitation.lastpage","1915"],["dc.bibliographiccitation.volume","32"],["dc.contributor.author","Focke, Niels K."],["dc.contributor.author","Helms, Gunther"],["dc.contributor.author","Scheewe, Sebstian"],["dc.contributor.author","Pantel, Pia M."],["dc.contributor.author","Bachmann, Cornelius G."],["dc.contributor.author","Dechent, Peter"],["dc.contributor.author","Ebentheuer, Jens"],["dc.contributor.author","Mohr, Alexander"],["dc.contributor.author","Paulus, Walter J."],["dc.contributor.author","Trenkwalder, Claudia"],["dc.date.accessioned","2018-11-07T08:50:18Z"],["dc.date.available","2018-11-07T08:50:18Z"],["dc.date.issued","2011"],["dc.description.abstract","Voxel-based morphometry (VBM) shows a differentiated pattern in patients with atypical Parkinson syndrome but so far has had little impact in individual cases. It is desirable to translate VBM findings into clinical practice and individual classification. To this end, we examined whether a support vector machine (SVM) can provide useful accuracies for the differential diagnosis. We acquired a volumetric 3D T1-weighted MRI of 21 patients with idiopathic Parkinson syndrome (IPS), 11 multiple systems atrophy (MSA-P) and 10 progressive supranuclear palsy (PSP), and 22 healthy controls. Images were segmented, normalized, and compared at group level with SPM8 in a classical VBM design. Next, a SVM analysis was performed on an individual basis with leave-one-out cross-validation. VBM showed a strong white matter loss in the mesencephalon of patients with PSP, a putaminal grey matter loss in MSA, and a cerebellar grey matter loss in patients with PSP compared with IPS. The SVM allowed for an individual classification in PSP versus IPS with up to 96.8% accuracy with 90% sensitivity and 100% specificity. In MSA versus IPS, an accuracy of 71.9% was achieved; sensitivity, however, was low with 36.4%. Patients with IPS could not be differentiated from controls. In summary, a voxel-based SVM analysis allows for a reliable classification of individual cases in PSP that can be directly clinically useful. For patients with MSA and IPS, further developments like quantitative MRI are needed. Hum Brain Mapp 32:1905-1915, 2011. (C) 2011 Wiley Periodicals, Inc."],["dc.identifier.doi","10.1002/hbm.21161"],["dc.identifier.isi","000296850700012"],["dc.identifier.pmid","21246668"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/21663"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Wiley-blackwell"],["dc.relation.issn","1065-9471"],["dc.title","Individual Voxel-Based Subtype Prediction can Differentiate Progressive Supranuclear Palsy from Idiopathic Parkinson Syndrome and Healthy Controls"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","226"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","Folia Neuropathologica"],["dc.bibliographiccitation.lastpage","233"],["dc.bibliographiccitation.volume","52"],["dc.contributor.author","Kallenberg, Kai"],["dc.contributor.author","Goldmann, Torben"],["dc.contributor.author","Menke, Jan"],["dc.contributor.author","Strik, Herwig"],["dc.contributor.author","Bock, Hans-Christoph"],["dc.contributor.author","Mohr, Alexander"],["dc.contributor.author","Buhk, Jan-Hendrik"],["dc.contributor.author","Frahm, Jens"],["dc.contributor.author","Dechent, Peter"],["dc.contributor.author","Knauth, Michael"],["dc.date.accessioned","2018-11-07T09:45:46Z"],["dc.date.available","2018-11-07T09:45:46Z"],["dc.date.issued","2014"],["dc.description.abstract","Introduction: Malignant brain tumors tend to migration and invasion of surrounding brain tissue. Histopathological studies reported malignant cells in macroscopically unsuspicious parenchyma (normal appearing white matter - NAWM) remote from the tumor localization. In early stages, diffuse interneural infiltration with changes of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) is hypothesized. Material and methods: Patients' ADC and FA values from NAWM of the hemisphere contralateral to a malignant glioma were compared to age- and sex-matched normal controls. Results: Apparent diffusion coefficient levels of the entire contra lateral hemisphere revealed a significant increase and a decrease of FA levels. An even more pronounced ADC increase was found in a region mirroring the glioma location. Conclusions: In patients with previously untreated anaplastic astrocytoma or glioblastoma, an increase of the ADC and a reduction of FA were found in the brain parenchyma of the hemisphere contralateral to the tumor localization. In the absence of visible MRI abnormalities, this may be an early indicator of microstructural changes of the NAWM attributed to malignant brain tumor."],["dc.description.sponsorship","Volkswagen Stiftung [ZN1635, ZN 2193]"],["dc.identifier.doi","10.5114/fn.2014.45563"],["dc.identifier.isi","000342712000002"],["dc.identifier.pmid","25310733"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/34702"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.relation.issn","1509-572X"],["dc.relation.issn","1641-4640"],["dc.title","Abnormalities in the normal appearing white matter of the cerebral hemisphere contralateral to a malignant brain tumor detected by diffusion tensor imaging"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","1164"],["dc.bibliographiccitation.issue","3"],["dc.bibliographiccitation.journal","NeuroImage"],["dc.bibliographiccitation.lastpage","1170"],["dc.bibliographiccitation.volume","56"],["dc.contributor.author","Focke, Niels K."],["dc.contributor.author","Helms, G."],["dc.contributor.author","Kaspar, S."],["dc.contributor.author","Diederich, Christine"],["dc.contributor.author","Toth, V."],["dc.contributor.author","Dechent, Peter"],["dc.contributor.author","Mohr, A."],["dc.contributor.author","Paulus, Walter J."],["dc.date.accessioned","2018-11-07T08:55:43Z"],["dc.date.available","2018-11-07T08:55:43Z"],["dc.date.issued","2011"],["dc.description.abstract","Voxel-based morphometry (VBM) is a widely applied method in computational neurosciences but it is currently recommended to compare only data collected at a single MRI scanner. Multi-site VBM would be a desirable approach to increase group size and, thus, statistical power. We aimed to assess if multi-site VBM is feasible on similar hardware and compare the magnitude of inter- and intra-scanner differences. 18 healthy subjects were scanned in two identical 3 T MRI scanners using different head coil designs, twice in scanner A and once in scanner B. 3D T1-weighted images were processed with SPM8 and FSL4.1 and compared as paired t-test (scan versus re-scan) on a voxel basis by means of a general linear model (GLM). Additionally, coefficient-of-difference (coeffD) maps were calculated for respective pairs of gray matter segmentations. We found considerable inter-scanner differences clearly exceeding a commonly used GLM significance threshold of p<0.05 (FWE corrected). The spatial pattern of detected differences was dependent on whether SPM8 or FSL4.1 was used. The inclusion of global correcting factors either aggravated (SPM8) or reduced the GLM detected differences ( FSL4.1). The coeffD analysis revealed markedly higher variability within the FSL4.1 stream both for the inter- and the intra-scanner comparison. A lowered bias cutoff (30 mm FWHM) in SPM8 improved the comparability for cortical areas. lima-scanner scan/re-scan differences were generally weaker and did not exceed a p<0.05 (FWE corrected) threshold in the GEM analysis. At 3 T profound inter-scanner differences are to be expected that could severely confound an unbalanced VBM analysis. These are like related to the receive bias of the radio-frequency hardware. (C) 2011 Elsevier Inc. All rights reserved."],["dc.description.sponsorship","University Medical Center Gottingen(\"Ruckkehrer-Startforderung\")"],["dc.identifier.doi","10.1016/j.neuroimage.2011.02.029"],["dc.identifier.isi","000290649300031"],["dc.identifier.pmid","21324367"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/22970"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Academic Press Inc Elsevier Science"],["dc.relation.issn","1053-8119"],["dc.title","Multi-site voxel-based morphometry - Not quite there yet"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","855"],["dc.bibliographiccitation.issue","10"],["dc.bibliographiccitation.journal","Neuroradiology"],["dc.bibliographiccitation.lastpage","861"],["dc.bibliographiccitation.volume","50"],["dc.contributor.author","Buhk, Jan-Hendrik"],["dc.contributor.author","Kallenberg, Kai"],["dc.contributor.author","Mohr, Alexander"],["dc.contributor.author","Dechent, Peter"],["dc.contributor.author","Knauth, Michael"],["dc.date.accessioned","2018-11-07T11:10:45Z"],["dc.date.available","2018-11-07T11:10:45Z"],["dc.date.issued","2008"],["dc.description.abstract","Introduction Long-term follow-up after coil embolization of intracranial aneurysms is mandatory to monitor coil compacting and aneurysm recurrence. Most centers perform one digital subtraction angiography (DSA) on follow-up continuing with time-of-flight magnetic resonance angiography (TOF-MRA). This study explores the diagnostic value of TOF-MRA at 1.5 T versus 3 T compared to DSA. Materials and methods In 18 patients with 20 aneurysms treated with coil embolization, TOF-MRA at 1.5 and 3 T were performed the day before follow-up DSA, the latter serving as reference. Optimized diagnostic protocols were applied (1.5 T: 0.78 x 0.55 x 0.8 mm, voxel size; acquisition time (TA), 6.37 min; 3 T: 0.56 x 0.45 x 0.65 mm, voxel size; TA, 3.12 min). Three independent neuroradiologists experienced in neuroendovascular therapy rated the occlusion rate (\"complete occlusion\" vs. \"residual neck\" vs. \"residual aneurysm\") and compared the two methods subjectively. Weighted kappa statistics were calculated to assess the level of interobserver agreement. Results Compared to DSA, TOF-MRA was more sensitive in detecting neck remnants, with a slight advantage at 3 T. Regarding artifact load, there are advantages at 1.5 T. Ratings of the occlusion rate correlated highly between all observers (r > 0.85, p < 0.001, respectively). Interobserver agreement was high in all cases (kappa(w) approximate to 0.8, respectively). Conclusion TOF-MRA is a reliable tool for follow-up imaging of cerebral aneurysms after endovascular treatment. Our study shows no advantage of TOF-MRA at 3 T over 1.5 T, when comparable measurement protocols are applied. TOF-MRA at 1.5 T therefore provides appropriate information regarding a therapeutic decision."],["dc.identifier.doi","10.1007/s00234-008-0413-7"],["dc.identifier.isi","000259576300005"],["dc.identifier.pmid","18523761"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?goescholar/3105"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/53277"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Springer"],["dc.relation.issn","0028-3940"],["dc.rights","Goescholar"],["dc.rights.uri","https://goescholar.uni-goettingen.de/licenses"],["dc.title","No advantage of time-of-flight magnetic resonance angiography at 3 Tesla compared to 1.5 Tesla in the follow-up after endovascular treatment of cerebral aneurysms"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","430"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","European Radiology"],["dc.bibliographiccitation.lastpage","436"],["dc.bibliographiccitation.volume","19"],["dc.contributor.author","Buhk, Jan-Hendrik"],["dc.contributor.author","Kallenberg, Kai"],["dc.contributor.author","Mohr, Alexander"],["dc.contributor.author","Dechent, Peter"],["dc.contributor.author","Knauth, Michael"],["dc.date.accessioned","2018-11-07T08:33:01Z"],["dc.date.available","2018-11-07T08:33:01Z"],["dc.date.issued","2009"],["dc.description.abstract","Following coil embolization of intracranial aneurysms, many centers perform at least one digital subtraction angiography (DSA) continuing with time-of-flight magnetic resonance angiography (TOF-MRA). Angiographic computed tomography (ACT) provides high-resolution data from a rotational acquisition of a c-arm-mounted flat panel detector. This study evaluates possible advantages of applying ACT in aneurysm follow-up. In 22 patients DSA examinations with a rotational acquisition were performed. Rotational data were processed into an isotropic high-resolution volume. TOF-MRA was performed the day before DSA. Three experienced neuroradiologists performed a rating of the occlusion rate and a subjective method comparison. Weighted kappa statistics were calculated to assess the level of interobserver agreement. Compared to DSA, the diagnostic value of ACT as well as of TOF-MRA was rated to be inferior, although the sensitivity of detecting residual necks was higher with both techniques. Compared to TOF-MRA, ACT achieves favorable ratings only in aneurysms after stent-remodeling. Interobserver agreement was high for all techniques. Ratings of the occlusion rate correlated highly between all observers (r > 0.85, p < 0.001, respectively). In selected patients ACT can add valuable diagnostic information to DSA. TOF-MRA remains a highly sensitive method for aneurysm follow-up."],["dc.identifier.doi","10.1007/s00330-008-1171-y"],["dc.identifier.isi","000262579000020"],["dc.identifier.pmid","18810455"],["dc.identifier.purl","https://resolver.sub.uni-goettingen.de/purl?goescholar/3502"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/17474"],["dc.notes.intern","Merged from goescholar"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Springer"],["dc.relation.issn","0938-7994"],["dc.rights","Goescholar"],["dc.rights.uri","https://goescholar.uni-goettingen.de/licenses"],["dc.title","Evaluation of angiographic computed tomography in the follow-up after endovascular treatment of cerebral aneurysms-a comparative study with DSA and TOF-MRA"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dc.type.version","published_version"],["dspace.entity.type","Publication"]]