The authors found the preoperative 3D model to be in high concordance with intraoperative conditions; the resulting intraoperative "déjà-vu" feeling enhanced surgical confidence. In all procedures planned with the Dextroscope, the chosen surgical strategy proved to be the correct choice. Three-dimensional virtual reality models of a patient allow quick and easy understanding of complex intracranial lesions.

Purpose: To determine if the diffusion tensor imaging (DTI) parameters fractional anisotropy (FA) and mean diffusivity (MD) can differentiate between accompanying edema and tumor cell infiltration of white matter (WM) beyond the tumor edge as defined from conventional MRI in low-and high-grade gliomas. Materials and Methods:We examined 12 patients with high-grade gliomas/glioblastomas and eight patients with low-grade gliomas and compared them to 10 patients with meningiomas, in which no tumor infiltration is expected. The tumor was defined as the enhancing area in glioblastomas and meningiomas and as the area of increased T2-signal in low-grade gliomas. FA and MD were measured in the center of the tumor and in the adjacent WM. The contralateral WM and internal capsule were used as an internal standard. Results:Comparing the WM areas of increased T2-signal adjacent to meningiomas and glioblastomas, we saw a trend (without significance) towards a reduction of FA, but not of MD, in glioblastomas. We found no changes of FA and MD in the WM adjacent to low-grade gliomas (without T2-signal increase) compared to the WM of the contralateral hemisphere. In meningiomas and high-grade gliomas/ glioblastomas, a narrow rim of significantly (P Ͻ 0.01) increased FA and decreased MD values around the enhancing tumor area was seen, whereas in low-grade gliomas, such a rim could not be defined. There was no contribution of FA or MD to grading of gliomas. Conclusion:In glioblastomas, a reduction of FA in the edematous area surrounding the tumor may indicate tumor cell infiltration, but a reliable differentiation between infiltration and vasogenic edema is not yet possible on the basis of DTI. The additional finding of a narrow rim of increased FA and decreased MD at the edge of glioblastomas (as well as in meningiomas) may be caused by compressed WM fibers and/or increased vascularity, but does not contribute to exclude peripheral cellular infiltration.

Purpose: To differentiate fibroblastic meningiomas, usually considered to be of a hard consistency, from other benign subtypes using diffusion tensor imaging (DTI). Materials and Methods:From DTI data sets of 30 patients with benign meningiomas, we calculated diffusion tensors and mean diffusivity (MD) and fractional anisotropy (FA) maps as well as barycentric maps representing the geometrical shape of the tensors. The findings were compared to postoperative histology. The study was approved by the local ethics committee, and informed consent was given by the patients.Results: According to one-way analysis of variance (ANOVA), FA was the best parameter to differentiate between the subtypes (F ϭ 32.2; p Ͻ 0.0001). Regarding tensor shape, endothelial meningiomas were represented by spherical tensors (80%) corresponding to isotropic diffusion, whereas the fibroblastic meningiomas showed a high percentage (43%) of nonspherical tensors, indicating planar or longitudinal diffusion. The difference was highly significant (F ϭ 28.4; p Ͻ 0.0001) and may be due to the fascicular arrangement of long spindle-shaped tumor cells and the high content of intra-and interfascicular fibers as shown in the histology. In addition, a capsule-like rim of the in-plane diffusion surrounded most meningiomas irrespective of their histological type. Conclusion:If these results correlate to the intraoperative findings of meningioma consistency, DTI-based measurement of FA and analysis of the shape of the diffusion tensor is a promising method to differentiate between fibroblastic and other subtypes of benign meningiomas in order to get information about their "hard" or "soft" consistency prior to removal.

Fiber tracking allows the in vivo reconstruction of human brain white matter fiber trajectories based on magnetic resonance diffusion tensor imaging (MR-DTI), but its application in the clinical routine is still in its infancy. In this study, we present a new software for fiber tracking, developed on top of a general-purpose DICOM (digital imaging and communications in medicine) framework, which can be easily integrated into existing picture archiving and communication system (PACS) of radiological institutions. Images combining anatomical information and the localization of different fiber tract trajectories can be encoded and exported in DICOM and Analyze formats, which are valuable resources in the clinical applications of this method. Fiber tracking was implemented based on existing line propagation algorithms, but it includes a heuristic for fiber crossings in the case of disk-shaped diffusion tensors. We successfully performed fiber tracking on MR-DTI data sets from 26 patients with different types of brain lesions affecting the corticospinal tracts. In all cases, the trajectories of the central spinal tract (pyramidal tract) were reconstructed and could be applied at the planning phase of the surgery as well as in intraoperative neuronavigation.

Background Endovascular treatment of acute cerebral large vessel occlusions and concomitant atherosclerotic lesions of the ipsilateral internal carotid artery (ICA) are a matter of debate. This article reports a multi-center experience using the retriever wire supported carotid artery revascularization (ReWiSed CARe) technique allowing simultaneous treatment of both lesions. Methods The study retrospectively analyzed 23 patients with acute tandem occlusions (TO) who underwent ReWiSed CARe at 3 German centers. Clinical, including demographics and National Institutes of Health Stroke Scale (NIHSS) and procedural, including angiographic evaluation of recanalization, data were evaluated. Favorable clinical outcome was defined as modified Rankin Scale (mRS) score Ä2 at 90 days. ResultsThe median age was 70 years (interquartile range [IQR] 65-80 years) and 70% were male. The median baseline NIHSS was 15 . Out of 23 patients, 22 (96%) had an intracranial occlusion of the anterior circulation. Successful stent retriever deployment with subsequent carotid artery treatment was feasible in all cases without displacement of the stent retriever during the procedure. Overall, successful reperfusion (modified Thrombolysis in Cerebral Infarction [mTICI] ≥2b) was achieved in 22/23 (96%) patients with 10/23 (44%) individuals completely reperfused (mTICI 3). The median groin puncture to stent retriever deployment was 29 min and groin puncture to final revascularization was 63 min . The median NIHSS at discharge was 5 (IQR 3-12) with favorable clinical outcome at 90 days in 11 out of 20 patients (55%). Conclusion Endovascular treatment using ReWiSed CARe is safe, fast and efficient in TO patients with underlying atherosclerotic lesion of the extracranial ICA.Volker Maus and Daniel Behme contributed equally to the manuscript.

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ZusammenfassungZiel: Durch Integration des Fiber Tracking in die intraoperative Neuronavigation sollten die Lage der kortikospinalen Bahnen bei der Operation von Hirntumoren dargestellt und gleichzeitig die Lokalisation der Trajektorien mit einer unabhängigen Methode auf Ortsgenauigkeit überprüft werden. Patienten und Methodik: Dazu wurden bei 21 Patienten MR-Untersuchungen mit Diffusion Tensor Imaging (DTI) durchgeführt, die Tensorenfelder berechnet und die Bahnenverläufe mittels eines modifizierten "Line-Propagation"-Algorithmus bestimmt. Der Algorithmus kann die Richtung der Haupteigenvektoren auch über Faserkreuzungen hinweg verfolgen. Das "Tracking" im peritumoralen Ödem ist durch die dort herabgesetzte fraktionale Anisotropie (FA) erschwert, so dass in diesen Fällen eine Modifizierung der Stopp-Kriterien des Algorithmus erforderlich war. Nach Koregistrierung der berechneten Trajektorien mit hochaufgelösten dreidimensionalen (3-D) Datensätzen und Umwandlung in das DICOM-Format wurden die Daten in ein neurochirurgisches Navigationssystem eingespeist. Ergebnisse: In allen 21 Fällen konnten die kortikospinalen Bahnen dargestellt werden. Dies wurde von den Neurochirurgen als sehr hilfreich empfunden, um eine Schädigung der Bahnen zu vermeiden. Während der Tumorentfernung wurde die Position der Bahnen bei 13 Patienten mittels elektrophysiologischer kortikaler und in 10 Fällen mit subkortikaler Stimulation überprüft und mit der Position der Trajektorien im Navigationssystem verglichen. In allen 13 Fällen war die kortikale Stimulation erfolgreich und bestätigte die Position des Gyrus praecentralis, aus dem die Trajektorien entsprangen. Eine positive Antwort auf die subkortikale Stimulation in der Wand der Tumorhöhle wurde dagegen nur in fünf von zehn Fällen erreicht, bei denen der Abstand zwischen Stimulationsort und Position der virtuellen Bahnen ≤ 1 cm war. In allen Fällen mit negativem Ergebnis war der Abstand größer. Schlussfolgerung: Wenn sich die Zuverlässigkeit des beschriebenen Fiber Tracking bei weiteren Untersuchungen bestä-tigt, sollte die Methode als wichtige Komponente in die Neuronavigationssysteme aufgenommen werden.

ZusammenfassungHintergrund und Ziel: Das Ziel dieser Studie war die Klärung der Frage, ob sich bei Patienten mit einer leichten kognitiven Beeinträchtigung im Sinne eines amnestischen "mild cognitive impairment" (MCI) sog. ultrastrukturelle Veränderungen mit Hilfe der Diffusions-Tensor-Bildgebung (DTI) nachweisen lassen. MCI stellt einen häufigen Übergang vom normalen Nachlassen der geistigen Leistungsfähigkeit im Alter zur Alzheimer-Demenz dar. Das posteriore Cingulum ist als Teil des sog. Papez-Kreises ein wichtiges neuronales Substrat der episodischen Gedächtnisleistung, die bei MCI typischerweise gestört ist. Pathologische Verminderungen des Glukosemetabolismus im Bereich des posterioren Cingulum konnten mittels Positronenemissionstomographie (FDG-PET) als Frühindikator einer Alzheimer-Erkrankung bei Patienten mit MCI nachgewiesen werden. Patienten und Methodik: Bei 17 Patienten mit MCI, 25 Patienten mit klinisch manifester Alzheimer-Demenz und 21 altersentsprechenden gesunden Probanden wurden neuropsychologische Untersuchungen und Messungen der beiden mittels DTI ermittelten Parameter mittlere Diffusivität (MD) und fraktionelle Anisotropie (FA) im posterioren Cingulum durchgeführt. Die Platzierung der dazu erforderlichen "regions of interest" erfolgte mit Hilfe von farbkodierten Karten der Marklagerbahnen, die aus den Tensoren berechnet wurden. Ergebnisse: Die Messung ergab bei den Patienten eine signifikante Steigerung der MD und eine Abnahme der FA im hinteren Anteil des Cingulum. Die pathologischen Veränderungen der Diffusionscharakteristika (MD und FA) korrelierten außer-dem mit den kognitiven Leistungen der psychologischen Tests. Schlussfolgerung: Diese Befunde stellen möglicherweise einen frühen MR-Indikator für die Entwicklung einer Alzheimer-Demenz dar. Schlüsselwörter: DTI · Leichte kognitive Beeinträchtigung · Cingulum Klin Neuroradiol 2005;15:117-22Abstract Background and Purpose: The aim of this study was the detection of diffusion tensor imaging-(DTI-)derived parameters mean diffusivity (MD) and fractional anisotropy (FA) in the posterior part of the cingulate fascicle in patients with mild cognitive impairment (MCI) which is commonly regarded as an early stage of Alzheimer's disease (AD). The posterior cingulate is an important part of the Papez circuit which subsumes necessary neural substrates of episodic memory. Decreases of posterior cingulate glucose metabolism corresponding to impaired memory performance could be demonstrated to indicate AD in MCI patients.