Speaker
Description
In small animals quantification of the dynamic arterial input function (AIF) is equally challenging for PET and MRI. AIF measurements provide the basis for kinetic modeling of both MR contrast agents (CA) and PET tracers.
Methodology:
Intracranial tumor-bearing mice received an extracorporeal shunt from the femoral artery to the tail vein. MRI scanning was performed using a 9.4 T MRI (Bruker BioSpec) and a cryo-cooled surface coil. The extracorporeal line featured two thickenings which resided in the MRI field of view. A MRI-compatible measuring chamber for a β-Microprobe (biospace lab) was included in the circulation. Dynamic MRI scanning of the head was performed for 15 minutes using a 3D FLASH with a spatial resolution of 0.175 x 0.175 x 1 mm and a temporal resolution of 4.015 s. A 100 µl solution containing 10-20 MBq F-18-PSMA-1007 and CA (Gadovist, 35 mM) was injected intravenously at 1 ml/min. Dispersion correction for MRI CA was performed based on the recorded distinct dispersion effect at the two interspaced thickenings. Dispersion correction for the PET tracer was performed empirically based on calibration measurements.
Results:
Our method allows for simultaneously resolving the AIF of MR CA and PET radiotracer as well as CA dynamics in tissue. The MR-based quantification shows good agreement with circulated human blood with defined CA concentrations in the range of expected concentrations and flow velocities. The CA-AIFs of 8 recorded mice show a close range of peak concentrations, little noise, typical AIF curve shape related to the simultaneously recorded PET-tracer curves.
Conclusions:
We present a novel approach for DCE-measurements of the AIF in mice providing the basis for quantitative estimation of blood-brain barrier integrity in mice. Moreover, we present the first dual recordings of AIFs of a MR CA and a PET tracer in mice. This supports evaluation approaches to deduce the CA/PET tracer AIF from one another. Further, it might provide the basis for simultaneous and integrated modeling of PET tracer and CA kinetics in mice, which is of high interest in integrated, simultaneous small animal PET/MRI.
Acknowledgment:
P.Backhaus was supported by the SFB 1009 with a 12 month “Research Rotation”.
