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Contrast MRI (contrast + mri)

Distribution by Scientific Domains
Medical Sciences100%

Kinds of Contrast MRI

  • phase contrast mri
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    Selected Abstracts

    The role of angiogenesis, vascular maturation, regression and stroma infiltration in dormancy and growth of implanted MLS ovarian carcinoma spheroids

    INTERNATIONAL JOURNAL OF CANCER, Issue 4 2004
    Assaf Gilead
    Abstract MLS ovarian epithelial carcinoma multicellular spheroids xenografted subcutaneously in CD-1 nude mice displayed growth delay, or dormancy, of up to 52 days. In the study reported here, implanted MLS spheroids were used for testing the role of angiogenesis and vascular maturation in triggering the initiation of tumor progression. The kinetics and impact of neovascular maturation and functionality, in dormancy, and growth of MLS spheroid xenografts were studied noninvasively by BOLD contrast MRI. MR data were supported by histologic staining for biotinylated albumin as a blood pool marker and alpha-smooth muscle actin (alpha-SMA) as marker for perivascular mural cells. Although the tumor periphery showed higher levels of total and mature vasculature than normal skin, the fraction of mature out of the total vessels as detected by MRI vascular maturation index (VMIMRI) was significantly lower in the tumor both before and after tumor exit from dormancy. The neovasculature induced by the implanted spheroid was unstable and showed cycles of vessel growth and regression. Surprisingly, this instability was not restricted to the immature vessels, but rather included also regression of mature vessels. During dormancy, neovasculature was predominantly peripheral with no infiltration into the implanted spheroid. Infiltration of alpha-SMA positive stroma cells into the spheroid was associated with functional vascularization and tumor growth. Thus, stroma infiltration and vascular maturation are an important checkpoint linking the angiogenic switch with initiation of tumor progression. © 2003 Wiley-Liss, Inc. [source]

    Absolute quantification of cerebral blood flow in normal volunteers: Correlation between Xe-133 SPECT and dynamic susceptibility contrast MRI

    JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 4 2007
    Linda Knutsson PhD
    Abstract Purpose To compare absolute cerebral blood flow (CBF) estimates obtained by dynamic susceptibility contrast MRI (DSC-MRI) and Xe-133 SPECT. Materials and Methods CBF was measured in 20 healthy volunteers using DSC-MRI at 3T and Xe-133 SPECT. DSC-MRI was accomplished by gradient-echo EPI and CBF was calculated using a time-shift-insensitive deconvolution algorithm and regional arterial input functions (AIFs). To improve the reproducibility of AIF registration the time integral was rescaled by use of a venous output function. In the Xe-133 SPECT experiment, Xe-133 gas was inhaled over 8 minutes and CBF was calculated using a biexponential analysis. Results The average whole-brain CBF estimates obtained by DSC-MRI and Xe-133 SPECT were 85 ± 23 mL/(min 100 g) and 40 ± 8 mL/(min 100 g), respectively (mean ± SD, n = 20). The linear CBF relationship between the two modalities showed a correlation coefficient of r = 0.76 and was described by the equation CBF(MRI) = 2.4 · CBF(Xe),7.9 (CBF in units of mL/(min 100 g)). Conclusion A reasonable positive linear correlation between MRI-based and SPECT-based CBF estimates was observed after AIF time-integral correction. The use of DSC-MRI typically results in overestimated absolute perfusion estimates and the present study indicates that this trend is further enhanced by the use of high magnetic field strength (3T). J. Magn. Reson. Imaging 2007;26:913,920. © 2007 Wiley-Liss, Inc. [source]

    Estimation of pulse wave velocity in main pulmonary artery with phase contrast MRI: Preliminary investigation

    JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2006
    Hsu-Hsia Peng MS
    Abstract Purpose To assess the feasibility and reproducibility of a noninvasive MRI method to measure pulse wave velocity (PWV) in the main pulmonary artery (MPA). Materials and Methods A total of 17 subjects without history of pulmonary diseases (38.2 ± 18.4 years) participated in this study. Series of MR velocity maps of the MPA were acquired at 2 cm above the pulmonary valves using a two-dimensional phase-contrast sequence. Effective temporal resolution was 11 msec after interleaving two dynamic series with different values of electrocardiograph (ECG) trigger delay. PWV was derived as the rate of MPA flow variations per unit change in MPA cross-sectional area, during early systole. Seven healthy subjects underwent three repetitive examinations to investigate intrascan and interscan reproducibility. Results Flow vs. area was highly linear in the MPA during early systole, with Pearson's coefficients ranging from 0.982 to 0.999, rendering derivation of PWV with little difficulty. Average value of PWV in MPA was 1.96 ± 0.27 m/second, in good agreement with literature values measured using invasive means. The percentage intra- and interscan differences were 5.46% and ,10.86%, respectively. Conclusion Phase-contrast MRI to noninvasively measure PWV in the MPA is feasible with good reproducibility. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc. [source]

    Simulation of phase contrast MRI of turbulent flow

    MAGNETIC RESONANCE IN MEDICINE, Issue 4 2010
    Sven Petersson
    Abstract Phase contrast MRI is a powerful tool for the assessment of blood flow. However, especially in the highly complex and turbulent flow that accompanies many cardiovascular diseases, phase contrast MRI may suffer from artifacts. Simulation of phase contrast MRI of turbulent flow could increase our understanding of phase contrast MRI artifacts in turbulent flows and facilitate the development of phase contrast MRI methods for the assessment of turbulent blood flow. We present a method for the simulation of phase contrast MRI measurements of turbulent flow. The method uses an Eulerian-Lagrangian approach, in which spin particle trajectories are computed from time-resolved large eddy simulations. The Bloch equations are solved for each spin for a frame of reference moving along the spins trajectory. The method was validated by comparison with phase contrast MRI measurements of velocity and intravoxel velocity standard deviation (IVSD) on a flow phantom consisting of a straight rigid pipe with a stenosis. Turbulence related artifacts, such as signal drop and ghosting, could be recognized in the measurements as well as in the simulations. The velocity and the IVSD obtained from the magnitude of the phase contrast MRI simulations agreed well with the measurements. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [source]

    Time-resolved flow measurement in the isolated rat heart: Characterization of left coronary artery stenosis

    MAGNETIC RESONANCE IN MEDICINE, Issue 3 2003
    Sascha Köhler
    Abstract The investigation of flow behavior in coronary arteries is of great importance for an understanding of heart failure and heart regulation mechanisms. The purpose of the present study was to demonstrate that flow velocity can be quantified in the coronary arteries of the isolated rat heart with high-resolution phase contrast MRI. A phase contrast cine-FLASH imaging sequence was used for flow quantification with an in-plane resolution of 70 ,m and a slice thickness of 500 ,m. With time-resolved measurements, coronary flow over the heart cycle was analyzed. Furthermore, the flow behavior in coronary stenosis was investigated and the degree of stenosis was quantified with MR phase contrast imaging. To achieve the required spatial resolution and a satisfactory signal-to-noise ratio, the experiments were performed at 11.75 T. Magn Reson Med 50:449,452, 2003. © 2003 Wiley-Liss, Inc. [source]

    Detection of the anoxic depolarization of focal ischemia using manganese-enhanced MRI

    MAGNETIC RESONANCE IN MEDICINE, Issue 1 2003
    Ichio Aoki
    Abstract Mismatch between diffusion- and perfusion-weighted MRI was used to indicate a treatable area following focal ischemia, called the penumbra. Activity-induced manganese contrast MRI has been reported as a new visualization method for neural activation using manganese ions as a depolarization-dependent contrast agent. It is well known that energy failure induced by cerebral ischemia produces anoxic depolarization. The purpose of this study was to detect manganese accumulation caused by permanent middle cerebral artery occlusion (MCAO) of rat brain and to compare regional differences between manganese accumulation and decreased apparent diffusion coefficient (ADC). The ratios of signal intensity of manganese-enhanced MRI in the ipsilateral cortex to that in the contralateral cortex were 171.0 ± 17.5% in MCAO group and 108.4 ± 13.2% in the sham group. In addition, the enhanced region was much smaller than the area which was detected as having a reduced ADC. Magn Reson Med 50:7,12, 2003. © 2003 Wiley-Liss, Inc. [source]