How to select right subgraph for dijkstra's algorithm

I think we can greatly improve the speed if we can reduce nodes to be processed. I want to find a shortest path from source node A to end node B(single-source and single-end).

So I set up a region what diameter is the linear distance from A to B(I do not know if my expression is right or not), denoted d. Or d can be a bit larger, for instance,d=d+0.5. the region is denoted R.

And I find all nodes in R and thus yields a new graph. we apply the dijkstra's algorithm in this subgraph.

I apply this idea into one of our project and proved to be success. But when I think of writing a paper to be published ,I do not know if it is right or not.

So can any of you give me some advice to improve this algorithm (idea)?

any reply to my email : URL
will be appreciated