pregnant cat and xrays

I have a pregnant cat that Im fostering through the local animal shelter.. so we have no idea when conception took place, but three weeks ago I got her lactating, and the head techniction there said she was ready to give birth any time..

well that was three weeks ago, so today I took her into the clinic I work at, and we took an xray, and there are skeletons, but they are very faint. I talked to the doctor about how things were going for me, and he said that it was going just fine, and they weren't ready any time.

But I didn't ask him when he thinks.. and he wont be back in for a couple of days.. so.. does anyone here know when kits show up on an xray??

I know that when they do ultrasound, the fetuses can be seen at 20 weeks, but with x-rays the full skeleton of the kittens can't been seen well enough until 2 weeks from delivery

the skeletons were very faint.. so we are probably looking at two weeks at the least??

I think the prior response meant 20 days not 20 weeks. LOL