# What is this R-like symbol power 2?

I found this in a computer medical research text.

What is the meaning of this R-like letter? S, in this context is an iso-intensity surface.

 Since context is not sufficient, I think it is a good idea to provide the text here:

• Characters is not what you think it is. – Asaf Karagila Jun 27 '11 at 18:34
• Asaf's comment is a reference to the fact (can't really blame the OP) that this question was originally tagged "characters". :-) – ShreevatsaR Jun 27 '11 at 18:44

## 1 Answer

It's hard to tell without a bit more context (and since I don't know what an iso-intensity surface is). But I think it would more commonly be written $\mathbb{R}^2$, which is the set of pairs of real numbers.

So my guess would be that saying $(x,y)\in \Re^2$ just means that $x$ and $y$ are both real numbers.

• This answer is almost certainly correct. I have unfortunately seen this use of this symbol a lot in computing literature. I guess it stems from the fact that it is called \real in LaTeX, presumably because it was meant to represent the operator that gives the real part of a complex number. – yasmar Jun 27 '11 at 19:17
• At the risk of stating what may already be obvious, I would wager that the context is medical imaging (MRI, tomography or something like that), in which case an iso-intensity surface would be the set of points having the same intensity. – Josh Chen Jun 27 '11 at 22:28
• I have edited the question, adding more context. – Karl Jun 28 '11 at 4:34
• I had a German professor who used this symbol instead of $\mathbb{R}$... I'm positive it's the same as a real number. – mathmath8128 Jun 28 '11 at 7:01