Magnetic resonance imaging of M64 inhibition of macrophage recruitment at a burn and infection site.

<p><b>a–e. </b><i>In vivo</i> positive contrast imaging of mice infected with PA14, plus and minus M64. The off resonance imaging transverse relaxation in the rotating frame (ORI-T2ρ) images were transformed to signal to noise ratio (SNR) images and thresholded in units of image standard deviation. <b>a., b.</b> The positive-contrast images are presented in pseudocolor, thresholded to signal greater than three in dimensionless SNR units, and superimposed on a FLASH image. For image processing, regions of interest (ROI) were drawn around the burn region and the total thresholded signal intensity was integrated within each ROI. Similar slices were chosen at the same anatomical location in all mice. <b>c., d.</b> 3-dimensional graphs of pixel intensities show an intense peak in the burn area for the PA14 control mouse, with this peak reduced by M64. <b>e.</b> Signal was measured in units of SNR, thresholded at three standard deviations, and measured within ROIs at the level of the burn and infection. The noise threshold was estimated by fitting the image background to a Rician distribution. Error bars depict standard error of the mean image intensity in the ROI. Error bars depict mean +/− SD of at least 3 replicates. Difference between PA14 and PA14 + M64 is statistically significant (<i>p</i><0.05, unpaired t test).