Journal of magnetic resonance imaging : JMRI
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J Magn Reson Imaging · Dec 2005
Partial volume effects on arterial input functions: shape and amplitude distortions and their correction.
For quantification of perfusion values from a bolus-tracking MRI experiment, the measurement of an arterial input function (AIF) is necessary. Gradient-echo (GE) sequences are commonly used for this type of experiment because they offer a high signal-to-noise ratio (SNR) and the potential to quantify the concentration of contrast agent. Measurements of calibration curves for Gd-DTPA in human blood have shown a quadratic relation between the DeltaR(2)* and the concentration of contrast agent, and a linear relationship between phase changes and the concentration of contrast agent. ⋯ Ignoring the presence of partial volume effects can lead to an overestimation or underestimation of the contrast agent concentration, depending on the experimental conditions. Correction for partial volume effects is feasible in arteries that are parallel to the main magnetic field by estimation and subtraction of the static signal of the surrounding tissue. Patient studies showed a large variation due to the AIF measurements, but it has also been shown that this influence can be minimized by correction for partial volume effects.
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J Magn Reson Imaging · Dec 2005
Arterial spin labeling in small animals: methods and applications to experimental cerebral ischemia.
ASL enables noninvasive, quantitative monitoring of cerebral perfusion to be performed repeatedly over a period of hours. Thus, ASL is an attractive method for basic science studies of the time evolution and pathophysiology of diseases using animal models. ⋯ Some technical factors pertinent to these studies are discussed, including a method for measuring arterial blood T(1) and double-echo PASL for measuring cerebral blood flow (CBF) and volume (CBV). Investigations of the CBF response to forebrain ischemia and reperfusion, and of regional variations in CBF and arterial transit time (ATT) are also discussed.