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Bram Stieltjes

Publications and source records attributed to Bram Stieltjes.

7 recordsLinked to original sources
PubMed2006

Functional magnetic resonance imaging for defining the biological target volume.

Morphology as demonstrated by CT is the basis for radiotherapy planning. Intensity-modulated and adaptive radiotherapy techniques would greatly benefit from additional functional information allowing for definition of the biological target volume. MRI techniques include several which can characterize and quantify different tissue properties and their tumour-related changes. Results of perfusion MRI represent microvascular density and permeability; MR spectroscopy depicts particular metabolites; diffusion weighted imaging shows tissue at risk and tumour cellularity; while dynamic 3D acquisition (4D MRI) shows organ motion and the mobility of tumours within them.

Axons↗
PubMed2006

Diffusion tensor imaging in primary brain tumors: reproducible quantitative analysis of corpus callosum infiltration and contralateral involvement using a probabilistic mixture model.

Diffusion tensor imaging (DTI) has been advocated as a promising tool for delineation of the extent of tumor infiltration by primary brain tumors. First reports show conflicting results mainly due to difficulties in reproducible determination of DTI-derived parameters. A novel method based on probabilistic voxel classification for a user-independent analysis of DTI-derived parameters is presented and tested in healthy controls and patients with primary brain tumors. The proposed quantification method proved to be highly reproducible both in healthy controls and patients. Fiber integrity in the corpus callosum (CC) was measured using this quantification method, and the profiles of fractional anisotropy (FA) provided additional information of the possible extent of infiltration of primary brain tumors when compared to conventional imaging. This yielded additional information on the nature of ambiguous contralateral lesions in patients with primary brain tumors. The results show that DTI-derived parameters can be determined reproducibly and may have a strong impact on evaluation of contralateral extent of primary brain tumors.

Adult↗
PubMed2006

Manganese-enhanced magnetic resonance imaging for in vivo assessment of damage and functional improvement following spinal cord injury in mice.

In past decades, much effort has been invested in developing therapies for spinal injuries. Lack of standardization of clinical read-out measures, however, makes direct comparison of experimental therapies difficult. Damage and therapeutic effects in vivo are routinely evaluated using rather subjective behavioral tests. Here we show that manganese-enhanced magnetic resonance imaging (MEMRI) can be used to examine the extent of damage following spinal cord injury (SCI) in mice in vivo. Injection of MnCl2 solution into the cerebrospinal fluid leads to manganese uptake into the spinal cord. Furthermore, after injury MEMRI-derived quantitative measures correlate closely with clinical locomotor scores. Improved locomotion due to treating the detrimental effects of SCI with an established therapy (neutralization of CD95Ligand) is reflected in an increase of manganese uptake into the injured spinal cord. Therefore, we demonstrate that MEMRI is a sensitive and objective tool for in vivo visualization and quantification of damage and functional improvement after SCI. Thus, MEMRI can serve as a reproducible surrogate measure of the clinical status of the spinal cord in mice, potentially becoming a standard approach for evaluating experimental therapies.

Algorithms↗
PubMed2004

Neutralization of CD95 ligand promotes regeneration and functional recovery after spinal cord injury.

The clinical outcome of spinal cord injury (SCI) depends in part on the extent of secondary damage, to which apoptosis contributes. The CD95 and tumor necrosis factor (TNF) ligand/receptor systems play an essential role in various apoptotic mechanisms. To determine the involvement of these ligands in SCI-induced damage, we neutralized the activity of CD95 ligand (CD95L) and/or TNF in spinal cord-injured mice. Therapeutic neutralization of CD95L, but not of TNF, significantly decreased apoptotic cell death after SCI. Mice treated with CD95L-specific antibodies were capable of initiating active hind-limb movements several weeks after injury. The improvement in locomotor performance was mirrored by an increase in regenerating fibers and upregulation of growth-associated protein-43 (GAP-43). Thus, neutralization of CD95L promoted axonal regeneration and functional improvement in injured adult animals. This therapeutic strategy may constitute a potent future treatment for human spinal injury.

Animals↗
PubMed2002

Brain white matter anatomy of tumor patients evaluated with diffusion tensor imaging.

We applied multislice, whole-brain diffusion tensor imaging (DTI) to two patients with anaplastic astrocytoma. Data were analyzed using DTI-based, color-coded images and a 3-D tract reconstruction technique for the study of altered white matter anatomy. Each tumor was near two major white matter tracts, namely, the superior longitudinal fasciculus and the corona radiata. Those tracts were identified using the color-coded maps, and spatial relationships with the tumors were characterized. In one patient the tumor displaced adjacent white matter tracts, whereas in the other it infiltrated the superior longitudinal fasciclus without displacement of white matter. DTI provides new information regarding the detailed relationship between tumor growth and nearby white matter tracts, which may be useful for preoperative planning.

Adult↗
PubMed2002

Imaging cortical association tracts in the human brain using diffusion-tensor-based axonal tracking.

Diffusion-tensor fiber tracking was used to identify the cores of several long-association fibers, including the anterior (ATR) and posterior (PTR) thalamic radiations, and the uncinate (UNC), superior longitudinal (SLF), inferior longitudinal (ILF), and inferior fronto-occipital (IFO) fasciculi. Tracking results were compared to existing anatomical knowledge, and showed good qualitative agreement. Guidelines were developed to reproducibly track these fibers in vivo. The interindividual variability of these reconstructions was assessed in a common spatial reference frame (Talairach space) using probabilistic mapping. As a first illustration of this technical capability, a reduction in brain connectivity in a patient with a childhood neurodegenerative disease (X-linked adrenoleukodystrophy) was demonstrated.

Adrenoleukodystrophy↗