Biomedical subjects

M Tittgemeyer

Publications and source records attributed to M Tittgemeyer.

4 recordsLinked to original sources

PubMed2006

Connectivity-Based Parcellation of Broca's Area.

It is generally agreed that the cerebral cortex can be segregated into structurally and functionally distinct areas. Anatomical subdivision of Broca's area has been achieved using different microanatomical criteria, such as cytoarchitecture and distribution of neuroreceptors. However, brain function also strongly depends upon anatomical connectivity, which therefore forms a sensible criterion for the functio-anatomical segregation of cortical areas. Diffusion-weighted magnetic resonance (MR) imaging offers the opportunity to apply this criterion in the individual living subject. Probabilistic tractographic methods provide excellent means to extract the connectivity signatures from diffusion-weighting MR data sets. The correlations among these signatures may then be used by an automatic clustering method to identify cortical regions with mutually distinct and internally coherent connectivity. We made use of this principle to parcellate Broca's area. As it turned out, 3 subregions are discernible that were identified as putative Brodmann area (BA) 44, BA45, and the deep frontal operculum. These results are discussed in the light of previous evidence from other methods in both human and nonhuman primates. We conclude that plausible results can be achieved by the proposed technique, which cannot be obtained by any other method in vivo. For the first time, there is a possibility to investigate the anatomical subdivision of Broca's area noninvasively in the individual living human subject.

Adult↗

PubMed2006

Assessment of ventricular reconfiguration after third ventriculostomy: what does shape analysis provide in addition to volumetry?

PURPOSE: From neuroradiologic experience, it is evident that the adaptation of the ventricular system secondary to pathologic processes or surgery is not uniform. To describe changes entirely, one must consider, in particular, information about volume and shape. In this study, we address specifically the information encoded in the change of shape. To exemplify the technique, we used time-series MR imaging examinations of patients with surgically treated chronic or acute occlusive hydrocephalus. METHODS: Preoperative and postoperative MR imaging at different time-steps was performed in 2 patients with occlusive hydrocephalus with a different time course of ventricular enlargement. The third and lateral ventricles were segmented with an automated classification scheme. Ventricular surfaces were binarized, mapped to a spheric coordinate system, and modeled by harmonic-basis functions. This approach allows simplification of the complex shape by stepwise filtering of the details that form the surface. The ventricles can be directly compared on the level of the simplified shape. RESULTS: Although the relative volumetric change was comparable between patients, analysis of shape revealed notable regional differences in the pattern of adaptation. Comparing subacute and chronic hydrocephalus, the analysis reflected fundamental differences in the pattern of ventricular enlargement. CONCLUSION: In addition to the mere volumetric description, this approach identifies regions that re-adjust differently to the altered pressure. The pattern of re-adaptation depends on the time course and history of the hydrocephalus. Furthermore, the different patterns of ventricular adaptation in patients with chronic or subacute hydrocephalus suggest a contiguity with properties of the surrounding parenchymal tissue.

Adult↗

PubMed2005

The first evaluation of brain shift during functional neurosurgery by deformation field analysis.

Stereotactic surgery is based on a high degree of accuracy in defining and localising intracranial targets and placing surgical tools. Brain shift can influence its accuracy significantly. Deep brain stimulation of the subthalamic nucleus can markedly change the quality of life of patients with advanced Parkinson's disease, but the outcome depends on the quality of electrode placement. A patient is reported in whom the placement of the second electrode was not successful. Deformation field analysis of pre- and postoperative three dimensional magnetic resonance images showed an intraoperative brain movement of 2 mm in the region of the subthalamic nucleus (the target point). Electrode repositioning resulted in efficient stimulation effects. This case report shows the need to reduce risk factors for intraoperative brain movement and demonstrates the ability of deformation field analysis to quantify this complication.

Aged↗

PubMed2004

[Mrt-based morphometry. A current assessment].

Morphometry offers new approaches for in vivo characterization of many neurologic and psychiatric pathologies. A survey of recent publications only hints at the attractiveness of magnetic resonance-based morphometry: published findings are heterogeneous, partly contradictory, and not always plausible in terms of known neuropathologic correlates. Hence, the sensitivity of the applied methods should be questioned. Three parameters affect the variance in morphometric findings: (1) knowledge about normal morphologic variability, (2) confounding physiologic parameters, and (3) methodologic misuse. Sound knowledge about the morphologic variability of the normal brain is vital for the assessment of volumetric findings. Large morphologic variability may also interfere with the precision of morphometric methods. The multitude of possible confounding physiologic parameters raises the necessity of precise subject control. Magnetic resonance scanning artefacts require rigid protocols, and application of the rather complex and sensitive methods demands profound insight into the techniques.

Anthropometry↗