Create a boundary/border inside a QGraphicsScene to allow QGraphicsItem collision

Hi, this is my first Qt project.

I'm looking to simulate a ball on a table rebounding off the edges of the table.
At the moment, I am using a QGraphicsEllipseItem to draw a ball, and then QGraphicsScene to simulate the table.
The animation is working perfectly, but I am now trying to somehow create a border or boundary inside the QGraphicsScene
so that I can say that, if the ball hits the edge of the boundary, it should rebound.
Is there any way I can do this?

Cheers