A review is being conducted of some 46,000 x-rays, cat scans and ultra sounds at University Hospital Kerry.
The South/South West Hospital Group (SSWHG) confirms it is investigating patient safety concerns at the hospital.
This follows the notification of three Serious Reportable Events (SREs) over the course of the summer.
Scans of some 26,000 people are involved in the process, with - in some cases - two or three scams per person.
The review, covering scans between the period of March 2016 to July 2017, started at end of October.
As of last Friday, 18,000 files have been reviewed and the SSWHG says "only a very small number of these" have resulted in a patient call back and were "purely precautionary".
It adds that only 21 patients have been called back for "repeat imaging" and that none required any further follow up or treatment.
The group says a 'look back' process with independent oversight is underway, and is expected to be completed within eight to ten weeks.
A clinical coordinator has also been identified to coordinate with patients, arranging appropriate follow-up.
"Any patients deemed to require urgent intervention will be immediately contacted before the full audit is complete", it says
A dedicated information line has been established at 1800-742-900.
This number will operate from 9.00am to 5.00pm Monday to Friday.