How come light photons penetrate these solutions easily

1. Apr 11, 2005

g.l.

Hello,

I'm looking for an answer to the following question -

X-rays are attenuated by liquid iodine solutions (in fact, these solutions are used as medical imaging contrast agents). so far so good.
How come light photons penetrate these solutions easily ? (these solutions appear water like - transparent)

Thanks for an educated explanation.