Fill in a logic image: possible in IDL ?

[Jose Silva <jsilva(at)br.mailandnews.com>]

Hello
I have a grayscale image (512 x 512 x 1 byte from medical TAC).
I applied a threshold to have a logic mask and tried to do a fill in that
mask
in order to remove some background. Most of languages have a fill command,
like FILL in draw programs that FILLs the image starting in X,Y (user
defined)
coordenations.
I search throw IDL commands and I never found any FILL command (or identical
command).
As most of languages (eg MATLAB and many others) have a FILL (BWFILL in
MATLAB, as morphologic operation), did I miss the FILL in IDL or there isn’t
any FILL in IDL?
 I tried to use POLYFILL but my mask is very irregular, not being possible
to
apply a POLYFILL in a predefined region.
Any commend on this subject is welcome…

level=100
mask= (image LE level) ; TAC of lungs (from TAC) with many irregularities
; FILL to “fill” mask starting (eg) in 1,1 pixel coordination