A concept for a magnetic particle imaging scanner with Halbach arrays.

Magnetic particle imaging (MPI) is a new medical imaging technique visualizing the concentration distribution of superparamagnetic nanoparticles used as tracer material. MPI is not yet in clinical routine, since one of the challenges is the upscaling of scanners. Typically, the magnetic fields of MPI scanners are generated electromagnetically, resulting in an immense power consumption but providing high flexibility in terms of adjusting the field strengths and very fast image acquisition rates. Permanent magnets provide high flux densities and do not need any power supply. However, the flux density is not adjustable, and a mechanical movement is slow compared to electromagnetically varying fields. The MPI scanner concept proposed here uses permanent magnets and provides high flexibility, with the possibility to choose between fast overview scanning and detailed image acquisition. By mechanical rotation of magnetic rings in Halbach array configuration, it is possible to adjust the field or gradient strengths. The latter allows for determining the spatial resolution and the size of the field of view. A continuous mechanical rotation defines the coarseness of the scanning trajectory and image acquisition rate. This concept provides a comparable flexibility, as an alternating magnetic field and an adjustable field gradient can be applied as known from electromagnetically driven MPI systems, and therefore yields high potential for an enlarged system. We present the idea of an arrangement of Halbach arrays and how to calculate the generated magnetic fields. Simulations for an exemplary geometry are provided to show the potential of the proposed setup.

First findings concerning airflow in noses with septal deviation and compensatory turbinate hypertrophy--a model study.

BACKGROUND: The nasal septal deviation is a common cause of nasal obstruction. On the other hand, many septal deviations are asymptomatic. It seems a physiological adaptation occurs on both sides. Septal deviation leads to internal nasal asymmetry, which in turn causes compensatory change in turbinate morphology (e.g. turbinate hypertrophy respectively hypotrophy). This mechanism is investigated with the help of fluid dynamic experiments and functional rhinologic diagnostics. METHODS: Functional models of the nose (modified Mink's boxes) were used and assessment was made by acoustic rhinometry and rhinoresistometry, followed by flow dynamic investigations. Septal deviations of varying position, together with turbinates of differing grades of hypertrophy, were simulated and assessed. RESULTS AND CONCLUSIONS: We observed in models of septal deviation an increase in flow resistance on the ipsilateral side as a result of friction of flow particles in the narrowing. Furthermore, on the opposite side of the deviation, the enlargement of the stream channel did not generally lead to a reduction in flow resistance, but rather to a 'dead space', where only a slow-circling eddy was observed. This eddy causes an increase in turbulence. In vivo turbinate hypertrophy occurs to fill this dead space, thereby reducing turbulent flow without a significant increase in resistance. In cases of moderate septal deviation, compensatory mechanisms of the turbinates can lead to a normalization of nasal airflow and surgical therapy would not be indicated. Deviations in the anterior part of the septum seem to be more symptomatic, because the mechanism is missing and due to the physiological narrowing of the nasal isthmus. To differ between physiologic and pathologic deviation, functional diagnostics are needed.

Development and validation of an indirect enzyme-linked immunosorbent assay (ELISA) for the nonsteroidal anti-inflammatory drug S-ibuprofen.

An indirect enzyme-linked immunosorbent assay (ELISA) was developed for the nonsteroidal anti-inflammatory drug (NSAID) S-ibuprofen. Conjugates for immunization were prepared by linking S-ibuprofen via the spacer 4-aminobutyric acid to bovine serum albumin as well as to a novel synthetic lipopeptide using the N-hydroxysuccinimide/dicyclohexylcarbodiimide method. Immunization with these immunogens was carried out in New Zealand rabbits. A poly-L-lysine-S-ibuprofen conjugate was used as a hapten-carrier for coating the surface of the microtiter plates with the hapten. Horse-radish peroxidase labeled anti-rabbit IgG served as secondary antibody using hydrogen peroxide and ABTS as substrates. The characterization of the polyclonal antiserum with compounds of analogous structure demonstrated that the antiserum possesses a very high specificity for S-ibuprofen (cross-reactivity < 0.14-1.4%). Additional cross-reactivity experiments using R-ibuprofen (cross-reactivity 50.5%), ibufenac (58%) and isopropylphenylacetic acid (6.4%) were carried out to obtain more detailed information about the antigenic recognition concerning the chiral center. The results indicated that the polyclonal antiserum possesses an additional antibody population, whose antigenic recognition did not contain the chiral center. The upper and lower limits of quantification of the developed ELISA were defined as 362 and 3.62 ng S-ibuprofen/ml, respectively, based on a 90% confidence interval.

Renal handling of amino acids in 5/6-nephrectomized rats: stimulation of renal amino acid reabsorption after treatment with triiodothyronine or dexamethasone under amino acid load.

In anaesthetized adult female rats, the renal amino acid handling was measured six days after 5/6 nephrectomy (5/6NX). The distinct rise in blood urea nitrogen as well as the significant reduction in urine flow and GFR indicate an impairment of kidney function. In principle, in 5/6NX rats amino acid plasma concentrations were comparable to those of control animals with two intact kidneys, whereas the fractional excretions (FEAA) of most endogenous amino acids measured were significantly enhanced. After bolus injection of leucine or taurine (each 20 mg/100 g b.wt.) or glutamine (90 mg/ 100 g b.wt.), dissolved in 2 ml normal saline per 100 g b.wt., the FEAA of both the amino acids administered and the endogenous amino acids increased as a sign of overloaded amino acid reabsorption capacity. This effect was more pronounced in 5/6NX rats than in controls. As early as one hour after amino acid load, plasma concentrations and FEAA returned to baseline values of 5/6NX rats. A pretreatment with triiodothyronine (20 micrograms/100 g b.wt.) or dexamethasone (60 micrograms/100 g b.wt.), both given intraperitoneally once daily for 3 days, stimulated the renal amino acid transport capacity in 5/6NX rats: the increase in FEAA after amino acid load was significantly lower compared to non-pretreated animals. This stimulation could be shown for the bolus amino acids and the endogenous amino acids and was more distinct in 5/6NX rats than in controls with two intact kidneys.