Assuming those consents are given, completion is expected by May 31.
Upon completion, the existing doctor shareholders and management will hold between 40 per cent and 49.9 per cent of Pacific Radiology.
"As the majority investor, Infratil will have governance rights consistent with its shareholding and, together with the doctor shareholders, will be able to drive the continued development and growth of the business," Infratil said in a statement.
Infratil chief executive Jason Boyes said the acquisition "sits well with Infratil's other high performing, high-quality assets" and would build on its investment in Qscan.
When Infratil outlined the company's strategic direction in February,Boyes named healthcare as one of three sectors for opportunity.
"Diagnostic imaging is an essential services industry, offering a combination of defensive characteristics and structural long-term growth," Boyes said.
"Pacific Radiology is New Zealand's largest private provider of diagnostic imaging and has a proven track record for delivering long-term growth, both organically and via acquisition," he said.
"We also see this as an opportunity to scale Infratil's investment in Qscan Group and create a meaningful Australasian healthcare platform with potential synergies and adjacent opportunities".
In other deals, Infratil stands to receive gross proceeds of $2 billion from an upgraded offer from Mercury and Australia's PowAR for its 65.5 per cent stake in Australasian wind power generator Tilt Renewables.
In December, Infratil's board, and one of its largest investors, Fisher Funds, rejected AustralianSuper's $5.37 billion offer for the ASX/NZX-listed infrastructure company, saying it undervalued its assets by a large margin.
Shares in Infratil last traded at $7.00, having gained 49 per cent over the last 12 months.
