Perfusion measurements using Arterial Spin Labeling and MRI in small animals: comparison with radioactive and fluorescent microspheres


Perfusion measurements using Arterial Spin Labeling and MRI in small animals: comparison with radioactive and fluorescent microspheres

Bos, A.; Bergmann, R.; Hofheinz, F.; van den Hoff, J.

Ziel/Aim:

Regional tissue perfusion is a fundamental physiological parameter controlling delivery of oxygen and nutrients to tissue. Arterial Spin Labeling (ASL) is a Magnetic Resonance Imaging (MRI) technique used for perfusion quantification. ASL has been shown to work reasonably well in human brain investigations. In other organs and especially in small animal imaging, however, ASL is not yet well established and validation against other methods is missing. The purpose of this work was to evaluate ASL in the brain of the rat by comparison with microspheres-derived regional perfusion using dedicated small animal PET and Optical Imaging (OI) systems.

Methodik/Methods:

Catheters were implanted through the right carotid artery in the left ventricle of the heart for administration of labeled microspheres (20μm) and in the left femoral artery for blood sampling. Microspheres were double-labeled with Cu-64 (or Ga-68) for PET (microPET P4, Siemens) and and X-sight 670 LSS for OI (Kodak FX). ASL measurements were performed in a 7T small animal MRI system (BioSpec 70/30, BRUKER) using a FAIR (Flow-sensitive Alternating Inversion Recovery) sequence with an adiabatic hyperbolic secant inversion pulse (length-bandwidth product: 80) and EPI (Echo Planar Imaging) acquisition. Global and selective T1 images were used for calculation of the perfusion values.

Ergebnisse/Results:

Perfusion in two brain slices was determined in three different ways (PET, MRI, OI). For the catheterized rat under anesthesia the whole brain perfusion values range from 0.2 to 1.19 ml/min/g for PET measurements and from 0.3 to 1.15 ml/min/g for OI calculations. In the normal rat brain (no catheter) under anesthesia perfusion values from FAIR-ASL ranged from 0.8 to 1.4 ml/min/g in both hemispheres (caudate putamen region). Catheter implantation created left/right differences between hemispheres of 10-30 %. The Pearson correlation factor varies between 0.88 and 0.9 for ASL vs. PET.

Schlussfolgerungen/Conclusions:

Overall the regional perfusion contrast is concordant between ASL and microspheres measurements. However, substantial quantitative deviations exist and are currently investigated. In order to become a useful routine applications in small animal imaging, ASL data acquisition and data evaluation needs to be further optimized. A thorough calibration via a quantitative comparison with radio- and fluorescent-labeled microspheres is mandatory. Altogether, perfusion quantification in the rat brain with ASL seems possible.

  • Lecture (Conference)
    Gemeinsame Jahrestagung der Deutschen, Österreichischen und Schweizerischen Gesellschaften für Nuklearmedizin 2011, 13.-16.04.2011, Bregenz, Österreich
  • Abstract in refereed journal
    Nuklearmedizin 50(2011), A10
    ISSN: 0029-5566

Permalink: https://www.hzdr.de/publications/Publ-15536
Publ.-Id: 15536