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Tissue Viability (tissue + viability)
Selected AbstractsPerfusion-based functional magnetic resonance imaging,CONCEPTS IN MAGNETIC RESONANCE, Issue 1 2003Afonso C. Silva Abstract The measurement of cerebral blood flow (CBF) is a very important way of assessing tissue viability, metabolism, and function. CBF can be measured noninvasively with magnetic resonance imaging (MRI) by using arterial water as a perfusion tracer. Because of the tight coupling between neural activity and CBF, functional MRI (fMRI) techniques are having a large impact in defining regions of the brain that are activated due to specific stimuli. Among the different fMRI techniques, CBF-based fMRI has the advantages of being specific to tissue signal change, a critical feature for quantitative measurements within and across subjects, and for high-resolution functional mapping. Unlike the conventional blood oxygenation level dependent (BOLD) technique, the CBF change is an excellent index of the magnitude of neural activity change. Thus, CBF-based fMRI is the tool of choice for longitudinal functional imaging studies. A review of the principles and theoretical backgrounds of both continuous and pulsed arterial spin labeling methods for measuring CBF is presented, and a general overview of their current applications in the field of functional brain mapping is provided. In particular, examples of the use of CBF-based fMRI to investigate the fundamental hemodynamic responses induced by neural activity and to determine the signal source of the most commonly used BOLD functional imaging are reviewed. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson 16A: 16,27, 2003 [source] Multiple spin-echo spectroscopic imaging for rapid quantitative assessment of N-acetylaspartate and lactate in acute strokeMAGNETIC RESONANCE IN MEDICINE, Issue 2 2004Astrid Stengel Abstract Monitoring the signal levels of lactate (Lac) and N-acetylaspartate (NAA) by chemical shift imaging can provide additional knowledge about tissue damage in acute stroke. Despite the need for this metabolic information, spectroscopic imaging (SI) has not been used routinely for acute stroke patients, mainly due to the long acquisition time required. The presented data demonstrate that the application of a fast multiple spin-echo (MSE) SI sequence can reduce the measurement time to 6 min (four spin echoes per echo train, 32 × 32 matrix). Quantification of Lac and NAA in terms of absolute concentrations (i.e., mmol/l) can be achieved by means of the phantom replacement approach, with correction terms for the longitudinal and transversal relaxation adapted to the multiple spin-echo sequence. In this pilot study of 10 stroke patients (symptom onset < 24 hr), metabolite concentrations obtained from MSE-SI add important information regarding tissue viability that is not provided by other sequences (e.g., diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI)). Metabolic changes extended beyond the borders of the apparent diffusion coefficient (ADC) lesion in nine of the 10 patients, showing a rise in Lac concentrations up to 18 mmol/l, while NAA levels sometimes dropped below the detection level. Considerable differences among the patients in terms of the Lac concentrations and the size of the SI-ADC mismatch were observed. Magn Reson Med 52:228,238, 2004. © 2004 Wiley-Liss, Inc. [source] Manganese-enhanced magnetic resonance imaging (MEMRI)NMR IN BIOMEDICINE, Issue 8 2004Alan P. Koretsky Abstract Manganese ion (Mn2+) is an essential metal that participates as a cofactor in a number of critical biological functions, such as electron transport, detoxification of free radicals and synthesis of neurotransmitters. Mn2+ can enter excitable cells using some of the same transport systems as Ca2+ and it can bind to a number of intracellular sites because it has high affinity for Ca2+ and Mg2+ binding sites on proteins and nucleic acids. Paramagnetic forms of manganese ions are potent MRI relaxation agents. Indeed, Mn2+ was the first contrast agent proposed for use in MRI. Recently, there has been renewed interest in combining the strong MRI relaxation effects of Mn2+ with its unique biology, in order to further expand the already broad assortment of useful information that can be measured by MRI. Such an approach has been continuously developed in the past several years to provide unique tissue contrast, to assess tissue viability, to act as a surrogate marker of calcium influx into cells and to trace neuronal connections. This special issue of NMR in Biomedicine on manganese-enhanced MRI (MEMRI) is aimed at providing the readers of this journal with an extensive review of some of the most prominent applications of MEMRI in biological systems. Written by several of the leaders in the field, the reviews and original research articles featured in this special issue are likely to offer an exciting and inspiring view of the broad range of applications of MEMRI. Copyright © 2004 John Wiley & Sons, Ltd. [source] Reduced chilling tolerance in elongating cucumber seedling radicles is related to their reduced antioxidant enzyme and DPPH-radical scavenging activityPHYSIOLOGIA PLANTARUM, Issue 2 2002Ho-Min Kang Cucumber seedling radicles become more chilling sensitive as they elongate. Chilling seedlings with radicles 20 mm long for 48 h at 2.5°C inhibited subsequent growth by 36%, while it reduced the growth of 70 mm-long radicles by 63%. Although the growth rate of non-chilled cucumber radicles at 25°C is constant from 20 to 80 mm, tissue viability [i.e. reduction of TTC (2,3,5-triphenyltetrazolium chloride) to formazan] and DPPH (,,, -diphenyl- , -picrylhydrazyl) radical scavenging activity of apical tissue declines as radicles elongate from 20 to 80 mm in length. TTC reduction, DPPH-radical scavenging activity and protein content of apical tissue were higher in 20 than in 70 mm radicles immediately after chilling and after an additional 48 h of growth at 25°C. Catalase (CAT; EC 1.11.1.6) and ascorbate peroxidase (APX; EC 1.11.1.11) activity was higher in the apical tissue of 20 than in 70 mm radicles before chilling. Immediately after chilling and after an additional 48 h at 25°C, superoxide dismutase (SOD; EC 1.15.1.1), glutathione reductase (GR; EC 1.6.4.2), and guaiacol peroxidase (GPX; EC 1.11.1.7) activity increased more rapidly in 70 mm radicles than in 20 mm radicles (SOD, GR, and GPX activity in 70 mm radicles was 1.5-, 1.9- and 8.6-fold higher, respectively, than in 20 mm radicles). However, APX and CAT activity in 20 mm radicles were always higher than in 70 mm radicles. Growth after chilling enhanced the activity of all antioxidant enzymes compared to that found in non-chilled tissue; however, CAT activity in 70 mm radicles did not recover to levels found in non-chilled tissue. Higher levels of CAT, APX and DPPH-radical scavenging activity are correlated with higher chilling tolerance of 20 mm-long cucumber radicles compared to 70 mm-long radicles. [source] Magnetic resonance cerebral metabolic rate of oxygen utilization in hyperacute stroke patientsANNALS OF NEUROLOGY, Issue 2 2003Jin-Moo Lee MD The purpose of this study was to explore the feasibility of obtaining magnetic resonance,measured cerebral metabolic rate of oxygen utilization (MR-CMRO2) in acute ischemic stroke patients. Seven stroke patients were serially imaged: 4.5 ± 0.9 hours (tp1), 3 to 5 days (tp2), and 1 to 3 months (tp3) after symptom onset. Diffusion-weighted, perfusion-weighted, and multiecho gradient-echo/spin-echo images were acquired; cerebral blood flow and oxygen extraction fraction maps were obtained from which CMRO2 was calculated as the product of cerebral blood flow and oxygen extraction fraction. The final infarct lesions obtained from tp3 T2-weighted images and the "penumbra" obtained from the tp1 perfusion-weighted image,defined lesion were coregistered onto tp1 CMRO2 maps. CMRO2 values in the region of brain that eventually infarcted were reduced to 0.40 ± 0.24 of the respective region on the contralateral hemisphere. The "salvaged penumbra" defined by the area of mismatch between the final infarct and the tp1 perfusion-weighted lesion demonstrated an average CMRO2 value of 0.55 ± 0.11 of the contralateral hemisphere. Although our results are preliminary and require further evaluation, the ability to obtain in vivo measurements of MR-CMRO2 noninvasively potentially can provide information for determining brain tissue viability in acute ischemic stroke patients. [source] | ||||||||||