Intravascular contrast agent T1 shortening: fast T1 relaxometry in a carotid volunteer study

To measure the T1 times in blood after the administration of the intravascular contrast agent gadofosveset trisodium in humans.

In a pilot study for parameter optimization, the T1-shortening induced by the injection of a single dose (0.03 mmol/kg body weight) of the MR contrast agent Vasovist (Bayer Schering Pharma AG) was measured at B0=1.5 T as a function of time. In four sessions, T1 measurements were performed in the carotid vein of 9 volunteers up to 30 min after injection. T1 times were measured using a segmented saturation recovery turboFLASH (SSRTFL) pulse sequence with 7 different saturation recovery delay times in a total acquisition time of 20 s.

The SSRTFL measurements showed T1 times of about 100 ms immediately after injection, which gradually increased to 175 ms at 30 min. The time curve of the R1=1/T1 averaged over all volunteers could be described with an exponential decay with a time constant T=330+/-65 s and an amplitude DeltaR1=4.1+/-0.3 s(-1), and a constant offset of R1(0)=5.7+/-0.2 s(-1). Mean relaxation values are in excellent agreement with theoretical predictions.

An analytical expression for the initial T1-shortening of Vasovist was derived which can now be used for optimization of the pulse sequence parameters in clinical studies.