It has emerged that a senior consultant wrote to management of the Louth-Meath hospital group seven years ago warning that "mistakes would be made" because of the state of radiology services.
Consultant radiologist Mark Towers wrote the letter in 2001 and said that the staffing situation was "wholly inadequate" for the workload.
He said the situation was "dangerous" for patients and staff.
And he wrote that in Navan things were at "breaking-point" while in Drogheda, he said the radiology services were collapsing.
The emergence of the letter follows a HSE announcement earlier this week, in which it said that it is currently reviewing thousands of chest X-rays and CT scans carried out on patients in the north-east area.
A number of patients in Our Lady of Lourdes Hospital in Drogheda and Our Lady's Hospital in Navan had their diagnoses delayed in 2006/2007 because a radiologist failed to notice an abnormality in their chest X-rays.
Four patients were subsequently diagnosed with lung cancer in follow up scans and all passed away.
All patients involved in the review are to be contacted with their results over the next few weeks.