Direct access to GIST structure

I was wondering if there is a way to get access to the tree structure
underlying at GIST index? What I would like to do is perform a
breadth-first search on the tree in order to find nearest neighbors
(using PostGIS data types). Nearest neighbor searchers are not very
efficient using only range queries as it is not known a priori how
large a range to sample. Searching the tree is very fast as the tree
encode spatial proximity. Is there an API (backend C-level is fine) to
access a GIST index?

THK

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Timothy H. Keitt, Assistant Professor
University of Texas at Austin http://www.keittlab.org/
Contact info and schedule at http://www.keittlab.org/~tkeitt/
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