Clinical evaluation of nine hollow-fibre membrane oxygenators.

In a comparative study we investigated the performance characteristics of nine hollow-fibre oxygenators. In a clinical setting, 10 units of each type of oxygenator were tested for oxygen exchange, transoxygenator pressure drop, heat exchanger performance and blood trauma. The oxygenators included are Maxima PRF Plus, Affinity, Forte, Affinity NT, Quantum, Optima, Capiox 1.

Aging of the adult human brain: in vivo quantitation of metabolite content with proton magnetic resonance spectroscopy.

The purpose of this study was to examine the effect of aging on brain metabolite concentrations, including N-acetyl aspartate (NAA), the major marker of neurones, using short echo proton spectroscopy. Single-voxel proton spectra (TE 30 msec, TR 2 seconds) were obtained from white and gray matter using automated software (PROBE, G.E.

Absolute metabolite quantification by in vivo NMR spectroscopy: V. Multicentre quantitative data analysis trial on the overlapping background problem.

The goal of this study was to establish the best approach for quantifying nuclear magnetic resonance (NMR) lines, that in the frequency domain are overlapping with broad, unwanted background features. To perform the quantitative data analysis in a controlled way, test signals were designed and utilised, derived from two different real-world in vivo nuclear magnetic resonance signals. One of the main conclusions of the study was that the quantification methods currently available to the biomedical research groups can deliver the correct values of the quantitative parameters, but that great care should be taken in using optimal input parameters for the computer programs concerned.

31P-magnetic resonance spectroscopy and 2H-magnetic resonance imaging studies of a panel of early-generation transplanted murine tumour models.

The objective of this study was first to determine whether three slowly growing early-generation murine transplantable tumours, the T40 fibrosarcoma, T115 mammary carcinoma and T237 lung carcinoma, exhibit patterns of energetics and blood flow during growth that are different from those of the faster growing RIF-1 fibrosarcoma. Serial measurements were made with 31P-magnetic resonance spectroscopy (MRS), relating to nutritive blood flow and 2H-magnetic resonance imaging (MRI), which is sensitive to both nutritive and large-vessel (non-nutritive) flow. All four tumour lines showed a decrease in betaNTP/Pi and pH with growth; however, each line showed a different pattern of blood flow that did not correlate with the decrease in energetics.

New approach for quantitation of short echo time in vivo 1H MR spectra of brain using AMARES.

Short echo time in vivo STEAM 1H MR spectra (4.7 T, TE = 16 ms) of normal rat brain were fitted in the time domain using a VARPRO-like algorithm called AMARES which allows an inclusion of a large amount of prior knowledge. The prior knowledge was derived from phantom spectra of pure metabolite solutions measured under the same experimental conditions as the in vivo spectra.

Improved method for accurate and efficient quantification of MRS data with use of prior knowledge.

We introduce AMARES (advanced method for accurate, robust, and efficient spectral fitting), an improved method for accurately and efficiently estimating the parameters of noisy magnetic resonance spectroscopy (MRS) signals in the time domain. As a reference time domain method we take VARPRO. VARPRO uses a simple Levenberg-Marquardt algorithm to minimize the variable projection functional.

Discrimination of metabolite from lipid and macromolecule resonances in cerebral infarction in humans using short echo proton spectroscopy.

Short-echo proton spectroscopy allows the noninvasive study of metabolites, lipids, and macromolecules in stroke patients, but spectra are difficult to interpret and quantify because narrow metabolite peaks are added to a broad background of lipid and macromolecule peaks. "Metabolite nulling" was used to distinguish the lactate peak from underlying lipid and macromolecule peaks. Increases in the lipid and macromolecule peaks were initially observed within the region of infarction in all patients, and further increases in lipid peaks were seen in five of the six patients during the following 6 weeks.

Intermittent antegrade/selective cerebral perfusion during circulatory arrest for repair of the aortic arch.

If the aortic arch requires repair or replacement due to an aneurysm or dissection, conventional cardiopulmonary bypass (CPB) is not possible during the period in which the aortic arch is excluded from the circulation. This creates a situation in which there is no cerebral circulation. The brain needs adequate protection from this ischaemic insult.

31P-magnetic resonance spectroscopy studies of nucleated and non-nucleated erythrocytes; time domain data analysis (VARPRO) incorporating prior knowledge can give information on the binding of ADP.

Human erythrocytes have no nucleus, mitochondria or endoplasmic reticulum, whereas chicken erythrocytes have a nucleus and mitochondria and are closer in internal morphology, to cells such as the hepatocyte. Erythrocytes were used to test the hypothesis that 31P-MRS invisibility of ADP is associated with the presence of intracellular organelles. Simple frequency domain spectral analysis methods showed that all the acid extractable ADP (and ATP) was MR-visible in human erythrocytes.

Quantification of metabolites from single-voxel in vivo 1H NMR data of normal human brain by means of time-domain data analysis.

We present here a combination of time-domain signal analysis procedures for quantification of human brain in vivo 1H NMR spectroscopy (MRS) data. The method is based on a separate removal of a residual water resonance followed by a frequency-selective time-domain line-shape fitting analysis of metabolite signals. Calculation of absolute metabolite concentrations was based on the internal water concentration as a reference.

Continuing ischemic damage after acute middle cerebral artery infarction in humans demonstrated by short-echo proton spectroscopy.

Background And Purpose: Proton MR spectroscopy is a noninvasive method of monitoring in vivo metabolite concentration changes over time. The aim of this work was to study the ischemic penumbra in humans by measuring the metabolic changes that occur after a middle cerebral artery territory infarction.

Methods: Diagnostic MRI and short-echo time MR spectroscopy were performed on a 1.

In vivo 31P MRS: absolute concentrations, signal-to-noise and prior knowledge.

Absolute metabolite concentrations have been estimated for nucleoside triphosphate and P(i) from in vivo 31P MR measurements using ISIS localization in a rat tumour model, and the results have been compared to those obtained from acid extracts of the tumours. The aim of the experiment was to assess the performance of four different spectral analysis techniques used for absolute quantitation. The spectral analysis techniques used were two frequency domain methods (peak area integration and Lorentzian fitting--FITSPEC) and two time domain methods (VARPRO and HLSVD).

Time and frequency domain analysis of NMR data compared: an application to 1D 1H spectra of lipoproteins.

A comparison between a time domain analysis algorithm (VARPRO) and a frequency domain analysis algorithm (FITPLAC) for parameter estimation of magnetic resonance spectroscopy (MRS) data series is presented. VARPRO analyses the measured MRS signal (free induction decay; FID); FITPLAC analyses the discrete Fourier transform of the FID, the frequency domain magnetic resonance spectrum. A rapid time domain method, used to subtract the dominating water resonance from a 1H MRS FID, without affecting the metabolites of interest, is outlined and applied.

Application of time-domain fitting in the quantification of in vivo 1H spectroscopic imaging data sets.

Time-domain model function fitting techniques were applied to improve the reconstruction of metabolite maps from the data sets obtained from in vivo 1H spectroscopic imaging (SI) experiments. First, residual water-related signals were removed from the SI data sets by using SVD-based linear time-domain fitting based upon the HSVD (State Space) approach. Second, peak integrals of the metabolites of interest were obtained by quantifying the proton spin-echoes of the voxels by means of non-linear time-domain fitting based upon the maximum likelihood principle.

The use of the Biomedicus centrifugal pump in combination with a separate reservoir with integrated heat exchanger in aneurysms of the thoracic aorta.

The surgical correction of aneurysms in the descending thoracic aorta necessitates clamping the aorta both proximal and distal to the aneurysm. The affected length can vary from a few centimetres to large portions of the upper and lower descending aorta. Clamping times can vary from a few minutes to more than one hour.