Crabb only joined in February but is stepping down “in order to devote more time to his other business interests”.
The search for a new boss is underway and Dr Alastair Riddell will assume the role of executive chairman in the meantime.
“On behalf of the board I would like to acknowledge and thank David for his contribution to Feedback,” said Riddell.
“We wish him well with his future endeavours.”
Feedback, which owns a smart piece of software that analyses medical images to reveal features that are not always evident to the human eye, will make a further announcement in due course.