any arbhorists/tree experts out there?

[TillEulenspiegel]

I live in Florida and we recently had 4 ( yup count em 4!) hurricanes march through the state.

What I have witnessed is that there there were huge amounts of large live Oaks that crushed the houses they once shaded.
I noticed that almost ALL of the trees that fell had hollow mid-sections ( Disease?Pests?).

I have an enormous 150 yr. old Oak 4 feet from my front door. My question is, How can I determine weather the tree is sick or has a hollow core?
Do I do a core sample? Is there an instrument - ultrasound, X-Ray- that I can see the interior and if its hollow remove the tree?

[OldBlueMoon]

I've seen core samples taken from large trees (on TV). They use a thin pipe and screw it into the trunk. They take it out and count the rings, since it's usually used to determine the ages of the trees. I figure they can also do this to see if the tree is hollow or diseased on the inside.

Don't know any names of those who do it though.
I know Asplundh (that how you spell it?) is a company that tears down trees, but I don't know if they test the trees.

[The Central Scrutinizer]

Either look in the yellow pages or perhaps even better, ask the local botanical garden or arboreteum for their thoughts or recommendations.

[Goshawk]

It's called a "resistograph". Info here.
http://hort.ifas.ufl.edu/woody/maturetreecare/Decayfactor.htm

Call a local tree doctor and have it done.