Bookings were not taken for a further 262 appointments in readiness for the expected action.
Otago District Health Board diagnostic and support services group manger Sonja Dillon said contingency plans for the action had focused on minimising risk to patients and staff.
During those times when labour was withdrawn or services limited, the board had an arrangement with the Association of Professional and Executive Employees for life-preserving cover.
The 51 technologists are withdrawing labour for all services between noon and 2pm on Monday, Tuesday and Thursday.
During those times, the radiology department will be closed.
Life-preserving cover would apply to situations such as emergency X-ray, computed tomography (CT) scans, magnetic resonance imaging (MRI), angiography and ultrasound.
The technologists' action would also involve withdrawing labour for CT scans, MRI, digital subtraction angiography and ultrasound from 5pm on Tuesday, Wednesday and Thursday to 8am the following days.
Ms Dillon said patients whose appointments had been affected had been contacted.
About 800 technologists are taking a variety of industrial actions around the country this month in protest at District Health Boards New Zealand's nil wage-increase offer.
Their multi-employer collective agreement expired last September and while the union says it has reduced its original claim, the district health board has not moved.
