Search PubMed⌕ Search

Biomedical subjects

A Ericsson

Publications and source records attributed to A Ericsson.

At least 109 records · Page 6Linked to original sources
PubMed1986

Antibodies to staphylococcal teichoic acid and alpha toxin in patients with cystic fibrosis.

Enzyme-linked immunosorbent assay (ELISA) was used for IgG antibody determination to teichoic acid and alpha-toxin from Staphylococcus aureus in 65 patients with cystic fibrosis (CF). In patients chronically colonized with S. aureus, elevated titres to teichoic acid were found in 13/35 (37%) patients, to alpha-toxin in 12/35 (34%) and to either antigen in 18/35 (51%). Patients with elevated titres to teichoic acid had a significantly lower X-ray score than patients with normal titres. The highest titres against both teichoic acid and alpha-toxin were seen in patients not receiving optimal treatment. These findings suggest that staphylococci contribute to the tissue damage in CF and that the determination of antibodies especially to staphylococcal teichoic acid might be of value in the diagnosis and management of staphylococcal infections in patients with CF.

Adolescent↗
PubMed1986

Selective properties of trains of real and complex RF micropulses in slice-selective spin-echo MRI.

The spin nutation properties of frequency selective (space selective in combination with a magnetic field gradient) trains of radiofrequency micropulses were studied in a numeric model. Two cases were considered, one simulating the 90 degrees excitation pulse in spin-echo MRI, the other the 180 degrees spin inversion pulse. Image reconstruction according to the 2-D Fourier transform technique requests that the effect of the 180 degree pulse is independent of the initial phase of the spin vector relative to the radiofrequency field. It was found that with a train of phase-stable radiofrequency micropulses with an envelope of the traditional 'sinc' type the result of the spin inversion pulse was depending on the initial phase whereas this was not the case for a train of phase-shifted (complex) micropulses. The complex train of radiofrequency micropulses also had better selective properties both for excitation and spin inversion than the real one.

Electron Spin Resonance Spectroscopy↗
PubMed1986

Subtraction in magnetic resonance imaging.

Subtraction of images recorded with multiple echo, spin echo (SE) techniques was performed in phantom and clinical studies of patients with pituitary adenomas and gliomas. The tissue differentiation was enhanced in the subtracted images.

Adenoma↗
PubMed1986

Method for quantification of low flow velocities by magnetic resonance phase imaging.

The aim of this study was to compare the influence of flow in the velocity range 0 to 25 mm/s on modulus, phase, real and imaginary images obtained with a standard magnetic resonance scanner (Siemens Magnetom, 0.5 T), and to develop a simple method for determination of flow velocities in vivo from this information. Using a flow phantom, the flow dependent magnetic resonance imaging (MRI) signal has been studied as a function of flow perpendicular to the image slice with non-doped water (simulating moving cerebrospinal fluid) as well as with water doped with Mn2+ (simulating moving blood) for each of the four mentioned image types. The results show a marked flow dependence on all types of images studied. The variation of the signal with flow in the modulus images is relaxation-time dependent in the studied velocity range and it is non-monotone for non-doped water. In the phase images, however, the variations are monotone and not dependent on relaxation times. In modulus images the curve shape is relatively independent on flow direction, while phase images are clearly dependent on flow direction in the studied velocity range. The signal versus velocity curves for the real and imaginary images show resemblance to those for the modulus and the phase images, respectively. It is concluded that the phase information can be used to generate a signal versus velocity calibration curve, which can be used to quantify low flow velocities in vivo.

Magnetic Resonance Imaging↗
PubMed1986

Cerebrospinal fluid flow studied with gated magnetic resonance imaging during the various parts of the cardiac cycle.

The pulsatile movement of cerebrospinal fluid (CSF) through the Sylvian aqueduct has been studied in two normal volunteers. A standard magnetic resonance scanner was used as well as a routine spin echo sequence. Series of ECG-gated axial images were obtained perpendicular to the long axis of the Sylvian aqueduct. Previously it has been demonstrated by flow phantom experiments that the phase information can be used to obtain a linear relation between phase and flow velocity. By multiplying the CSF flow velocity by the cross-sectional area of the aqueduct of Sylvius obtained in each image, the CSF flow variation during the cardiac cycle could be demonstrated and measured.

Cerebrospinal Fluid↗
PubMed1984

Relation between antibody response to Pseudomonas aeruginosa exoproteins and colonization/infection in patients with cystic fibrosis.

Enzyme-linked immunosorbent assay (ELISA) was used to measure the antibody response to Pseudomonas aeruginosa exotoxin A, elastase, alkaline protease and phospholipase C in patients with cystic fibrosis (CF). Only the chronically colonized patients showed elevated antibody titres to phospholipase C (22/22 patients), alkaline protease (16/22 patients), exotoxin A (15/22 patients) and elastase (5/22 patients). In a few patients where serial specimens were available, rising titres were recorded to all four antigens during periods of active infection. Antibiotic treatment resulted in decrease of titres against all four antigens, but only the anti-exotoxin A and anti-elastase titres decreased to normal levels. Titres to phospholipase C were the least influenced by antibiotic treatment. The results imply different roles for these exoproteins in chronic colonization versus active infection. The levels of P. aeruginosa antibodies to exoproteins could probably be used in monitoring treatment of patients with CF.

ADP Ribose Transferases↗
PubMed1983

Clinical results and pharmacokinetics of ceftazidime treatment in patients with cystic fibrosis.

Ceftazidime (50 mg/kg/8 h) alone or combined with tobramycin (5 mg/kg/8 h) was given to 14 patients with cystic fibrosis. Ten courses were given with ceftazidime alone and 6 courses with a combined therapy. All patients were chronically colonized with Pseudomonas aeruginosa and were hospitalized because of lower respiratory tract infections. Using an agar-well diffusion technique, the concentration of ceftazidime was determined in serum and sputum. The mean (+/- S.E.M.) peak serum concentration of ceftazidime was 142 +/- 16 mg/l during the second to third day of treatment and 114 +/- 18 mg/l on the fifth to sixth day of treatment. In the combined therapy the corresponding values were 104 +/- 20 mg/l and 74 +/- 8 mg/l, respectively. The range of the mean half life was 1.2 to 1.4 h. The maximum concentration of ceftazidime in sputum was usually obtained 1 h after the infusion, ranging from 0.7 to 9.8 mg/l. All patients improved during treatment. Non-mucoid strains of Ps. aeruginosa were eradicated in nearly half of the courses, mucoid strains less often. No side reactions were noted.

Adolescent↗
PubMed1978

Influence of the Irradiance on Carbohydrate Content and Rooting of Cuttings of Pine Seedlings (Pinus sylvestris L.).

Seedlings of Pinus sylvestris L. were grown for 6 weeks at an irradiance of either 8 or 40 watts per square meter in a controlled environment room. Cuttings from these plants were rooted in tap water for 75 days at either 8 or 40 watts per square meter. The photoperiod was 17 hours.During the first 30 days of the rooting period quantitative changes in carbohydrates were recorded in cuttings from the different treatments. The carbohydrate contents of the cuttings were mainly regulated by the irradiance during the stock plant stage and generally a higher carbohydrate level was found in cuttings from stock plants grown at 40 watts per square meter.The irradiance during the rooting period had only minor effects on the time course of root formation, whereas the irradiance during the stock plant stage did influence the subsequent root formation. Cuttings from stock plants grown at 8 watts per square meter rooted faster and with higher frequency than those from stock plants grown at 40 watts per square meter. These results are discussed in relation to the mentioned irradiance effects on carbohydrate content.

Journal Article↗
PubMedDate not supplied

A rotating phantom for the study of flow effects in MR imaging.

A common type of phantom used for the study of flow effects in MR imaging is the tube phantom, where a liquid passes through a set of tubes placed in the main magnetic field of an MR scanner. Among the disadvantages with this type of phantom are that a distribution of velocities is present in each tube, and that quantifications of flow effects using tube phantoms may be very time-consuming. In this work, we describe the design and the properties of a rotating wheel flow phantom used for quantification of the effects of flow through the imaging plane as well as in the imaging plane. The proposed phantom is constructed as a rotating gel-filled wheel, surrounded by static volumes filled with the same gel, and the evaluation of the information from rotating and static parts is made with a specially designed computer program. The phantom can be used as a plug flow phantom covering simultaneously an interchangeable velocity interval, which at present has the range -52 mm/s, +52 mm/s. It is shown that the phantom gives adequate information on the dependence of pixel content on first-order motion in MR modulus and phase images. Among the fields of application are rapid calibration of MR imaging units for flow determination using phase information, as well as testing of pulse sequence characteristics and verification of theoretical predictions concerning the flow dependence in MR images.

Electron Spin Resonance Spectroscopy↗
PubMedDate not supplied

A method for MR quantification of flow velocities in blood and CSF using interleaved gradient-echo pulse sequences.

The aim of this study was to establish a rapid method for in vivo quantification of a large range of flow velocities using phase information. A basic gradient-echo sequence was constructed, in which flow was encoded along the slice selection direction by variation of the amplitude of a bipolar gradient without changes in sequence timings. The influence of field inhomogeneities and eddy currents was studied in a 1.5 T interleaved sequences for calibration and in vivo flow determination were constructed, and flow information was obtained by pairwise subtraction of velocity-encoded from velocity non-encoded phase images. Calibration was performed in a nongated mode using flow phantoms, and the results were compared with theoretically calculated encoding efficiencies. In vivo flow was studied in healthy volunteers in three different areas using cardiac gating; central blood flow in the great thoracic vessels, peripheral blood flow in the popliteal vessels, and flow of cerebrospinal fluid (CSF) in the cerebral aqueduct. The results show good agreement with results obtained with other techniques. The proposed method for flow determination was shown to be rapid and flexible, and we thus conclude that it seems well suited for routine clinical MR examinations.

Aorta↗
PubMedDate not supplied

Cardiac gated MR imaging of cerebrospinal fluid flow.

This is a preliminary investigation of the cerebrospinal fluid (CSF) spaces using cardiac gated magnetic resonance imaging. A variation of intensity of the signal from the cerebral aqueduct is demonstrated during the cardiac cycle. The pattern of this variation suggests pulsatile CSF flow. Calculations that have been verified by phantom measurements show that CSF flow rates less than 1 mm/s may be detectable. Magnetic resonance may therefore offer a new method for the demonstration and measurement of CSF flow.

Cerebral Aqueduct↗
PubMedDate not supplied

Quantitative study of flow dependence in NMR images at low flow velocities.

A basic theoretical model that describes the effects of flow in and out of the imaging plane in nuclear magnetic resonance (NMR) images, obtained with the standard pulse sequences single spin echo, multiple spin echo, and inversion recovery, is presented. Theoretically calculated signal values are compared with experimental results obtained from single-slice images of a flow phantom for variable flow velocity v as well as for variable echo time and inversion time at flow velocities less than 10 mm/s, corresponding to those found in cerebrospinal fluid, in capillary systems, and in smaller veins. The quantitative correspondence between theory and experiment is good in the range of velocities studied and for the imaging parameters used, but discrepancies occur when higher velocities are studied. In addition, flow in a capillary model is demonstrated qualitatively for very low linear flow velocities, less than 1 mm/s. It is concluded that the model describes the essentials of the inflow-outflow effect and that this effect can predict the flow dependence of the NMR signal for low flow velocities. Observed differences between model and experiment may be due to effects of flow-induced phase alterations and due to uncertainty in measurements of the relaxation times T1 and T2. The model described here can be extended to suit other types of pulse sequences and to suit multislice imaging. It can also be extended to incorporate flow-induced phase effects.

Blood Flow Velocity↗
PubMedDate not supplied

Proton relaxation in a multicompartmental system with exchange, simulating human tissue.

The proton magnetic resonance behaviour of human tissue was simulated with a numerical model in which the resonating nuclei were assumed to belong to five different compartments of defined relative sizes and with distinct relaxation properties. Effects of various proton exchange rates between the compartments were included in the model. The time evolution of longitudinal and transverse macroscopic magnetizations was calculated. Applications of this model in magnetic resonance imaging are discussed.

Body Fluid Compartments↗