Poster — Thur Eve — 29: Determination of Contrast Agent Concentration in Tortuous Blood Vessels Using Measured MRI Phase Changes and Fourier‐Based Field Inhomogeneity Equations

There has been considerable research effort into obtaining quantitative measures of perfusion using dynamic contrast‐enhanced MRI. Absolute quantification of the arterial input function (AIF) and/or venous output function (VOF) in major blood vessels improves perfusion estimates, however reliable techniques for doing so are lacking. Using changes in phase (Δφ) in blood vessels is thought to be the best way to quantify the AIF or VOF. However, it is not yet clear how best to deal with the susceptibility physics when the blood vessels have a complex geometry. We propose a methodology for obtaining absolute quantification of the AIF or VOF using a Fourier‐based calculation of field inhomogeneities, in order to convert Δφ to absolute contrast agent concentration, regardless of the blood vessel geometry. This methodology was tested in an aqueous phantom system. The experimentally measured Δφ was divided by the expected Δφ on a pixel by pixel basis. Ideally, this ratio should be one. Considering all pixels in the phantom tubing, the measured Δφ divided by expected Δφ had a mean value of 1.02 and standard deviation of 0.172. The Fourier‐based calculation can therefore successfully predict Δφ and thus can be used to account for the effect of the vessel geometry and orientation in the conversion of MR phase to contrast agent concentration. The methodology is thus promising for making absolute measurements of the AIF or VOF.