An embedded optical tracking system for motion-corrected magnetic resonance imaging at 7T

Object

Prospective motion correction using data from optical tracking systems has been previously shown to reduce motion artifacts in MR imaging of the head. We evaluate a novel optical embedded tracking system.

Materials and methods

The home-built optical embedded tracking system performs image processing within a 7T scanner bore, enabling high speed tracking. Corrected and uncorrected in vivo MR volumes are acquired interleaved using a modified 3D FLASH sequence, and their image quality is assessed and compared.

Results

The latency between motion and correction of the slice position was measured to be (19?±?5)?ms, and the tracking noise has a standard deviation no greater than 10???m/0.005° during conventional MR scanning. Prospective motion correction improved the edge strength by 16?% on average, even though the volunteers were asked to remain motionless during the acquisitions.

Conclusion

Using a novel method for validating the effectiveness of in vivo prospective motion correction, we have demonstrated that prospective motion correction using motion data from the embedded tracking system considerably improved image quality.     

Albumin exchange and polymorphonuclear vascular transit in hyperoxic pulmonary oedema in awake rats

Vascular inflammatory response to hyperoxia (FIO2 greater than 0.98) was studied in awake jugular and carotid catheterized rats. Simultaneous i.v. injection of 125I albumin (125I A), 99mTc polymorphonuclear cells (99mTc PMN) and 51Cr red blood cells (51Cr RBC) allowed to study both the macromolecule exchange through vascular endothelium and the leukocyte uptake by several organs (liver, lungs, spleen) with respect to radiolabelled red blood cells, as an intravascular reference. Rats were exposed to O2 for 24, 38 and 45 h. They were anesthetized and killed by exanguination 15 to 120 min following the tracer injection. After 45 h exposure, the plasmatic 125I A half-life decreased significantly (158 +/- 42 min for the control; 106 +/- 34 min for the exposed animals). The ratio 125I A/51Cr RBC varied significantly in the lung. The iodinated albumin exchange through lung vascular endothelium was altered at the 24th h, with a significant difference reached by the 45th h. At the same time, the pulmonary decreasing curve of 99mTc/51Cr RBC ratio versus time was not not modified. In our experimental conditions, there was no detectable variation in the lung uptake and vascular transit of PMN cells. The discussion of the results must be related with the technics used in the present work when the albumin exchange increased.     

On preconditioning for a parallel solution of the Richards equation

In this paper, we present a class of preconditioning methods for a parallel solution of the three-dimensional Richards equation. The preconditioning methods Jacobi scaling, block-Jacobi, incomplete lower–upper, incomplete Cholesky and algebraic multigrid were applied in combination with a parallel conjugate gradient solver and tested for robustness and convergence using two model scenarios. The first scenario was an infiltration into initially dry, sandy soil discretised in 500,000 nodes. The second scenario comprised spatially distributed soil properties using 275,706 numerical nodes and atmospheric boundary conditions. Computational results showed a high efficiency of the nonlinear parallel solution procedure for both scenarios using up to 64 processors. Using 32 processors for the first scenario reduced the wall clock time to slightly more than 1% of the single processor run. For scenario 2 the use of 64 processors reduces the wall clock time to slightly more than 20% of the 8 processors wall clock time. The difference in the efficiency of the various preconditioning methods is moderate but not negligible. The use of the multigrid preconditioning algorithm is recommended, since on average it performed best for both scenarios.     

Relationship between plasma phospholipid transfer protein activity and HDL subclasses among patients with low HDL and cardiovascular disease

NK lysin is a 9-kDa polypeptide that was originally isolated from porcine intestinal tissue based on its antibacterial activity. It is produced by cytolytic lymphocytes and is cytolytic against a number of different types of tumor cells. Here we report the binding of NK lysin to lipopolysaccharide (LPS) and its anti-LPS activity. NK lysin binds to matrix-coated LPS from Escherichia coli, Pseudomonas aeruginosa, and different strains of Salmonella enterica. Lipid A and polymyxin B inhibited the binding, demonstrating a preferential interaction of NK lysin with the lipid part of LPS. Chromium-labeled lymphoma cells were lysed by NK lysin, and LPS dose-dependently inhibited the cytolysis at equimolar amounts. In the same manner, NK lysin inhibited certain LPS-stimulated effects on mouse bone marrow cells as well as LPS binding to mouse granulocytes. These results suggest that NK lysin may be a another natural LPS-binding protein from lymphocytes that may participate in the endogenous defense response associated with elevated concentrations of LPS.     

Nitric oxide synthase activity in human squamous cell carcinoma of the head and neck

A continuous fluorometric assay for tryptophan hydroxylase activity based on the different spectral characteristics of tryptophan and 5-hydroxytryptophan is presented. Hydroxylation of tryptophan at the 5-position results in a large increase in the fluorescence of the molecule. The assay selectively monitors the fluorescence yield of 5-hydroxytryptophan by exciting the reaction mix at 300 nm. The rate of increase of the emission signal was found to be directly proportional to the enzyme concentration. Inner filter effects due to quinonoid dihydropterin accumulation were eliminated by the inclusion of a thiol reductant. Activity measured using this assay method was found to be the same as that determined by established discontinuous HPLC assay methods. The application of the assay to routine activity measurements and to steady-state determinations with the substrates tryptophan and tetrahydropterin is described.     

Delayed onset of hand tremor related to cerebellar hemorrhage

Spontaneous hematomas are rare and can present with acute or chronic symptoms. Our patient presented with deep vein thrombosis of the lower extremity associated with a spontaneous pelvic hematoma. This lesion was radiologically and clinically indistinguishable from a soft-tissue neoplasm. The case of a spontaneous pelvic neoplasm in an otherwise healthy young man is presented and the literature reviewed regarding issues of differential diagnosis and clinical management.     

Influence of antibody binding on oxygen binding behavior of Panulirus interruptus hemocyanin

Evidence linking paclitaxel to cardiotoxicity arose from early Phase I trials in which continuous cardiac monitoring was performed because of the high incidence of major hypersensitivity reactions. A variety of cardiac manifestations have been reported, ranging from asymptomatic sinus bradycardia to fatal myocardial infarction. The following case report describes an acute myocardial infarction occurring shortly after paclitaxel therapy.