Note that the hematocrit may vary in the same patient over time, especially in cancer patients undergoing chemotherapy. Changing Hct may thus significantly affect serial quantitive DCE measurements if adjustments are not made. Another factor not frequently considered in most DCE calculations is that Hct is a factor of 2 or more lower in capillaries (where gadolinium exchange occurs) than in larger arteries (Fåhraeus effect).
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In cardiac imaging and some other applications a saturation recovery (SR) sequence may be used for DCE instead of a spoiled GRE. In this case the signal intensity equation is given by
S = k [H] (1 − e−TD/T1) e−TE/T2*
where TD is the delay time between the 90°-pulse and acquisition.
Fåhraeus R, Lindqvist T. The viscosity of the blood in narrow capillary tubes. Am J Physiol 1931; 96:562-568. (Classic paper demonstrating what is now known as the "Fåhraeus effect" - that hematocrit decreases strongly with reduced vascular size below about 0.3 mm diameter. This is because blood viscosity decreases and RBCs move more quickly than plasma down the center of capillaries.)
Parker GJM, Barker GJ, Tofts PS. Accurate multislice gradient echo T1 measurement in the presence of non-ideal RF pulse shape and RF filed nonuniformity. Magn Reson Med 2001; 45:838-845.
Pries AR, Ley K, Gaehtgens P. Generalization of the Fåhraeus principle for microvessel networks. Am J Physiol 1986; 251:H1324-H1332.
Schabel MC, Parker DL. Uncertainty and bias in contrast concentration measurements using spoiled gradient echo pulse sequences. Phys Med Biol 2008; 53:2345-2373.
Tofts PS. T1-weighted DCE imaging concepts: modelling, acquisition and analysis. MAGNETOM Flash 2010; 3:30-35.
Zaharchuk G. Theoretical basis of hemodynamic MR imaging techniques to measure cerebral blood volume, cerebral blood flow, and permeability. AJNR Am J Neuroradiol 2007; 28:1850-8.
Is it possible to quantify the actual concentration of Gd from its signal in a DSC study?
Why would you want to use a spoiled-GRE technique? How do you pick the parameters?