Information extracted from a poster presented at B Chen, AT Yordanov, GA Johnson, Functional pulmonary MR microscopy in mice, Annual Experimental Biology (FASEB) Conference, Washington, DC, April 17-21, 2004. ( pdf of poster )
The mouse has become a key animal model to connect genotype to both structural and functional phenotype. As research in functional genomics progresses, the interest in non-invasive assessment of changes in pulmonary structure and function in a physiological stable mouse has increased.
We report here the use of MR microscopy with gadolinium (Gd)-labeled dendrimers and hyperpolarized 3Helium (He) gas to acquire in vivo pulmonary images that indicate perfusion and ventilation distribution in the lung. The images (512 x 512 with 36 mm field of view) were acquired at 2.0 T with breath-hold using a ventilator-gated 3-dimensional radial encoding technique for thin slices (800 µm).
A custom-made constant flow ventilator was used to deliver gas mixtures of 23% O2 and 77% N2 during 1H imaging and 23% O2 and 77% HP 3He during 3He imaging. Instrumental dead space was minimized and air compression was corrected for tidal volume. The Gd-labeled dendrimer (G4-1B4M-Gd, 10,000 Da) was administered (~150 mg in 0.1 ml) via a tail vein as an intravascular contrast agent (half-life of ~80 min).
| Comparison of 1H images prior-to (a) and after (b) injection of the intravascular contrast agent with voxels of 70 x 70 x 800 µm3. This macromolecular-based agent does not leak through the vascular wall.
The ‘x’ marks indicate the regions of interest in the tissue, left ventricle, and peripheral lung for signal-to-noise (SNR) analysis. The SNR prior to the contrast agent (a) are 4.8 in the tissue, 5.9 in the left ventricle, and 3.5 in the peripheral lung, compared to 5.1, 11.7, and 6.6 after the administration of contrast agent (b).
Note the increase in contrast difference between the vasculature and the surrounding tissues.
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