Somewhat unsurprisingly, doctors who own an investment interest (or outright ownership of equipment / facility) are 3.7 times more likely to order CT/MRI scans.

That is purely human "greed".

I somehow doubt that self-selection of patients needing such imaging is occurring.

Well, or the doctor is interested and knowledgeable in MRI scans, which leads to both investment and more likely to use it as a tool.

Which either says that other doctors are under-using MRI scans (doubtful, the US orders more CT/MRI scans per capita than any other country on earth by nearly seventy per cent, which to say that doctors elsewhere should be doing up to six times more), or that they're exploring their own "interest" at the cost of the consumer.