The medical physicists' union, the Association of Professional and Executive Employees (APEX), backs the strike action.
APEX advocacy leader David Munro said employers need to stop hiding from the problem.
"While like all unions we support the government's emphasis on boosting the low paid, the fact of the matter is that this professional group spend eight years [studying] before they are let loose on a linear accelerator," he said.
"They are incredibly highly qualified, they are very sought after overseas and if we don't have any increase in pay or superannuation ... we're going to lose them."
Australian colleagues in the profession are often paid double that of their New Zealand counterparts.
Their employer's superannuation contribution is also three times larger, at 12.5 per cent, compared to New Zealand's current rate of 3 per cent.
Munro believed that was already having an effect on the industry.
"Late last year one newly qualifying physicist left for Perth to earn as much as the chief physicist at the DHB he was leaving.
"That is close to double what he would earn in New Zealand."
Medical physicists here were asking to have their superannuation contribution doubled to 6 per cent to match that of a New Zealand doctor's, he said.
"These are the best medical physicians in New Zealand and we need to keep them in the public sector."
Medical physicians who work in the public sector make up 95 per cent of the profession's workforce.
Seventy-five employees across six DHBs would take part in the action, Munro said.
Regular appointments have been rescheduled or deferred and no patients have had their therapy compromised for the strike action.
Bargaining talks, facilitated by the Employment Relations Authority, are set to take place next week on February 23 and 24.