In-vivo high-resolution X-ray microtomography for liver and spleen tumor assessment in mice

The present study sought to validate the use of glycery1-2-oley-1,3-bis-[7-(3-amino-2,4,6-triiodophenyl)- heptanoate] (DHOG) contrast agent for mouse spleen tumor and liver metastasis imaging by high-resolution X-ray microtomography. Three groups of female nude mice were compared: controls (n = 5), and mice injected with 2.5 x 10(6) STC1 tumor cells in the spleen, imaged at 15 days (group G15, n = 5) and at 30 days (group G30, n = 5, of which one died before imaging). Micro-CT scans (X-ray voltage, 50 kVp; anode current, 200 microA; exposure time, 632 ms; 180 rotational steps resulting in 35 microm isotropic spatial resolution) were acquired at 0, 0.75, 2 and 4 h after i.v. injection of DHOG. CT number (Hounsfield units: HU) and contrast-to-noise ratios (CNR) were determined in three organs. Statistical analysis was performed by Mann-Whitney U-test. Contrast enhancement in normal spleen and liver increased, respectively to 1020 +/- 159 and 351 +/- 27 HU over baseline at 4 h, and 482 +/- 3 and 203 +/- 14 HU on day 6 after a single contrast injection. Automated three-dimensional reconstruction and modeling of the spleen provided accurate and quantifiable images. Spleen tumor and liver metastases did not take up DHOG, making them detectable in contrast to the increased signal in normal tissue. The smallest liver metastasis detected measured 0.3 mm in diameter. High-resolution X-ray micro-CT in living mice using DHOG contrast agent allowed visualization and volume quantification of normal spleen and of spleen tumor and its liver metastases.