Atomic - 12:35 am on May 8, 2008 (gmt 0)
In fact it turns out that a separate script that displays images on pages was run several hundred thousand times. The script is intended to discourage linking to my images. The image is on a page with AdSense but the page itself WAS NOT called. The logfile confirms this. Only the script with the querystring identifying the image was run. I can't find anything indicating why AdSense impressions match the image scripts.