Biomedical subjects

Thomas Benner

Publications and source records attributed to Thomas Benner.

22 records · Page 2Linked to original sources

PubMed2003

Tracer arrival timing-insensitive technique for estimating flow in MR perfusion-weighted imaging using singular value decomposition with a block-circulant deconvolution matrix.

Relative cerebral blood flow (CBF) and tissue mean transit time (MTT) estimates from bolus-tracking MR perfusion-weighted imaging (PWI) have been shown to be sensitive to delay and dispersion when using singular value decomposition (SVD) with a single measured arterial input function. This study proposes a technique that is made time-shift insensitive by the use of a block-circulant matrix for deconvolution with (oSVD) and without (cSVD) minimization of oscillation of the derived residue function. The performances of these methods are compared with standard SVD (sSVD) in both numerical simulations and in clinically acquired data. An additional index of disturbed hemodynamics (oDelay) is proposed that represents the tracer arrival time difference between the AIF and tissue signal. Results show that PWI estimates from sSVD are weighted by tracer arrival time differences, while those from oSVD and cSVD are not. oSVD also provides estimates that are less sensitive to blood volume compared to cSVD. Using PWI data that can be routinely collected clinically, oSVD shows promise in providing tracer arrival timing-insensitive flow estimates and hence a more specific indicator of ischemic injury. Shift maps can continue to provide a sensitive reflection of disturbed hemodynamics.

Aged↗

PubMed2003

Medical telematics in disaster response.

INTRODUCTION: Every year many disasters cause thousands of injuries, deaths, refugees. Depending on the kind of disaster (train/plane accident, flood, earthquake) not only an acute emergency medicine treatment but also general and family medicine and hospital treatment have to be safeguarded over a longer time-period in the disaster area. PROBLEM: Regarding to a lot of organizations, institutions and disaster teams taking part in the disaster assistance is there any lack of work or data flow in the medical treatment? METHODS: From the ODRA flood 1997, the high speed train crash in ESCHEDE 1998, the DANUBE flood 1999 and the ELBE flood in 2002 experience reports were collected. They were analysed with emphasis on data and work flow in the medical treatment and its command system: Standardised command structure? Communication problems? Used communication lines? Language problems? Medical Intelligence distribution? Use of Patient Tracking System? Triage problems? RESULTS: The use of spoken radio communication causes transmission mistakes or misunderstandings and radio-overload and need connection-set-up-time for each call. Manual distribution of same data for many receivers using different communication lines causes a time shift in the up-to-date-information. Language problems during the ODRA flood between German and Polish people led to longer reaction times. Up-to-date triage results as well as up-to-date transportation and hospital information are necessary for medical evacuation. Compared with other reports about these disasters the quality of disaster management depends on the quality of communication and information. CONCLUSION: The use of health telematics in disaster response helps to cope with the scenario. Modern technologies provide support for building up medical aid although the normal infrastructure is destroyed. To cope with disaster scenarios there are some telematic tools which can be used:--Computer-based Command and Control System--Telemedical support --Data-ressources-network /Medical Intelligence. A further study is recommended to evaluate the real impact of using these telematic tools in a disaster.

Disaster Planning↗

PubMed2002

Motor recovery and cortical reorganization after constraint-induced movement therapy in stroke patients: a preliminary study.

Constraint-induced movement therapy (CIMT) is a physical rehabilitation regime that has been previously shown to improve motor function in chronic hemiparetic stroke patients. However, the neural mechanisms supporting rehabilitation-induced motor recovery are poorly understood. The goal of this study was to assess motor cortical reorganization after CIMT using functional magnetic resonance imaging (fMRI). In a repeated-measures design, 4 incompletely recovered chronic stroke patients treated with CIMT underwent motor function testing and fMRI. Five age-matched normal subjects were also imaged. A laterality index (LI) was determined from the fMRI data, reflecting the distribution of activation in motor cortices contralateral compared with ipsilateral to the moving hand. Pre-intervention fMRI showed a lower LI during affected hand movement of stroke patients (LI = 0.23+/-0.07) compared to controls (LI unaffected patient hand = 0.65+/-0.10; LI dominant normal hand = 0.65+/-0.11; LI nondominant normal hand = 0.69+/-0.11; P < 0.05) due to trends toward increased ipsilateral motor cortical activation. Motor function testing showed that patients made significant gains in functional use of the stroke-affected upper extremity (detected by the Motor Activity Log) and significant reductions in motor impairment (detected by the Fugl-Meyer Stroke Scale and the Wolf Motor Function Test) immediately after CIMT, and these effects persisted at 6-month follow-up. The behavioral effects of CIMT were associated with a trend toward a reduced LI from pre-intervention to immediately post-intervention (LI = -0.01+/-0.06, P = 0.077) and 6 months post-intervention (LI = -0.03+/-0.15). Stroke-affected hand movement was not accompanied by mirror movements during fMRI, and electromyographic measures of mirror recruitment under simulated fMRI conditions were not correlated with LI values. These data provide preliminary evidence that gains in motor function produced by CIMT in chronic stroke patients may be associated with a shift in laterality of motor cortical activation toward the undamaged hemisphere.

Adult↗

PubMed2002

Perfusion- and diffusion-weighted magnetic resonance imaging for monitoring decompressive craniectomy in animals with experimental hemispheric stroke.

OBJECT: The aim of this study was to use two types of serial magnetic resonance (MR) imaging-perfusion-weighted (PW) and diffusion-weighted (DW)-to monitor craniectomy in rats with hemispheric stroke. METHODS: Focal cerebral ischemia was induced in 36 rats by using an endovascular method of occlusion of the middle cerebral artery (MCAO). Craniectomy was performed 4 or 24 hours later in 12 animals each. Twelve control animals underwent occlusion but did not receive treatment. Perfusion-weighted, DW, and T2-weighted MR images were obtained at 4, 24, 48, 72, and 168 hours postocclusion in all animals. Relative regional cerebral blood volumes and apparent diffusion coefficients (ADCs) were calculated for the cortex and basal ganglia. Hemispheric lesion volumes (expressed as percentages of total brain volumes; %HLV) as they appeared on DW and T2-weighted MR images and on histological slices stained with 2,3,5-triphenyltetrazolium chloride were compared. Neurological performances and infarct volumes measured 7 days postocclusion were used as study end points. Both PW and DW images demonstrated ischemic tissue 4 hours after MCAO in all animals. Early treatment by performing craniectomy significantly improved cortical perfusion (p < 0.01), whereas the same procedure conveyed no benefit to the basal ganglia. Compared with findings in control animals, the DW image-derived %HLV was significantly reduced (p < 0.01) and the cortical ADCs at 4 and 24 hours postocclusion were significantly higher in animals treated early (p < 0.05). Late treatment with craniectomy did not significantly affect cerebral perfusion. The correlation between the DW imaging-derived %HLV and the histologically derived %HLV at 4 to 72 hours postocclusion was good (r = 0.74), whereas at Day 7 postocclusion the %HLV was underestimated up to 41% on DW imaging. At 4 hours postocclusion T-weighted imaging failed to demonstrate the ischemic lesion, whereas from 24 to 72 hours postocclusion the correlation between the T2-weighted imaging-derived %HLV and the histologically derived %HLV was good (r > 0.81). Neurological performance was significantly improved in animals treated using craniectomy. CONCLUSIONS: Early craniectomy significantly improves cortical perfusion through leptomeningeal collateral vessels, significantly reduces infarct size, and improves neurological performance in animals with experimental acute hemispheric infarction. Both PW and DW imaging are suitable for noninvasive monitoring of the effects of decompressive craniectomy.

Acute Disease↗