Study finds big variation in hospital X-ray radiation levels

Enormous variation between hospitals in the radiation levels used for identical X-ray procedures have been found in a new study of Irish hospital practice. The radiation exposure in one hospital was 23 times higher than another for a typical chest X-ray, the study showed.

The study, prepared by two UCD researchers and published in the current issue of the British Journal of Radiology, also highlighted the fact that only one in four of the 16 hospitals surveyed applied quality-assurance procedures in its X-ray units to keep radiation exposures to patients as low as possible.

This did not mean, however, that the X-ray practices in any of the hospitals were unsafe, according to Dr Patrick Brennan of the school of diagnostic imaging at UCD, who co-authored the report with Ms Deirdre Johnston, a radiographer at Cork Regional Hospital.

"You can get a considerably higher dose of radiation, depending on which hospital you go to", Dr Brennan said. He pointed out that the dose in a diagnostic Xray was "very, very small" and said that it would be wrong to suggest that it might be unsafe for the patient.

It was good radiological practice, however, to keep X-ray exposure to the patient as low as possible. "The risk is proportional to the dose. If you do increase the dose, you do increase the risk, but the risk is still very, very, very small."

The gains offered by better diagnosis outweighed the risks associated with the use of X-rays, Dr Brennan said.

The study was designed to help Ireland establish national "reference dose levels" (RDLs) for various types of X-rays.

A new EU directive (97/43 Euratom) comes into force here next month and requires all radiology departments to promote the use of RDLs, Dr Brennan said. There had been no previous attempt to establish RDLs on the basis of typical radiological practice in Ireland until this thesis project by Ms Johnston, he added.

The Radiological Protection Institute of Ireland, which licenses the use of X-ray equipment, does not set dose limits for individual procedures, a spokeswoman said yesterday. It was for the medical practitioner to establish how much radiation was needed to get a usable X-ray image, she said.

The institute did apply limits for staff using the equipment and for incidental radiation exposure from all sources for members of the general public, she added.

In general, the researchers found that patient exposures here "were certainly not higher than in other countries". Exposures here were on average 40 per cent lower than in UK hospitals on the basis of one UK study, Dr Brennan said.

There was significant variability between Irish hospital practice, however, leading to wide differences in exposures for similar X-rays. These varied from three times to 23 times the dose, depending on the hospital and the type of X-ray taken.

Other research had shown that if hospitals applied a "quality assurance programme" to reduce patient exposures, these exposures invariably fell, Dr Brennan said. Yet 12 of the 16 Irish hospitals selected at random for the study had no or only very limited quality assurance procedures in place. "Hospitals exhibiting the highest variations in patient doses were among these hospitals, while those with rigorous QA procedures showed much less variation", the report stated.

"Variations in dose within a hospital room emphasise the importance of a quality assurance programme, so that inconsistencies and errors in technique and equipment can be discovered early and thus reduce the variation in dose to patients . . .