W.M.M.J. Bovee

Determination of in vivo rat muscle Gd-DTPA relaxivity at 6.3 T.

For the in vivo relaxivity of Gd-DTPA at 6.3 T in rat muscle a value of 2.7±0.5 (mM s)−1 was found, and for the in vitro value in water 3.00±0.56 (mM s)−1 at 37°C. The temperature dependence of the in vitro relaxivity was −0.087 (mM s °C)−1. The relation between1/T1 and the tissue Gd-DTPA concentration is linear for the normally used in vivo Gd-DTPA concentration range

Influence of the pharmacokinetic model on the quantification of the Gd-DTPA uptake rate in brain tumours using direct T1 measurements

After a bolus injection of Gd-DTPA, a fast tracer uptake in rat brain tumours was already observed during the tracer bolus passage. For the quantification of the uptake rate constant, pharmacokinetic models are commonly used. For a good quantification, the changes of the plasma tracer concentration directly after the bolus injection must be incorporated into these models as prior knowledge. The aim of this paper is to investigate whether or not it is necessary to include the bolus passage into the description for the plasma tracer concentration. The result of this study indicates that the best quantification of the uptake rate constant is achieved by using only the data points after the bolus passage. Using all the data points and incorporating the bolus passage in the pharmacokinetic models results in a less accurate estimation.