Ireland tackles radiation dose in cardiac interventions

The radiation dose delivered during fluoroscopic cardiac interventional procedures is facing scrutiny. Researchers from Ireland aim to establish local x-ray dose reference levels for examinations in cardiovascular centers to produce a benchmark against which individual performance can be judged.

They hope to quantify the ionizing radiation exposure to patients undergoing cardiac intervention and identify causal agents in high-dose situations.

Researchers from the University College Dublin and the University of Ulster in Jordanstown, Belfast, are seeking to establish ways to reduce radiation dose while maintaining image quality and diagnostic efficacy. The goal is to encourage centers to take corrective action if necessary. The group presented its initial findings at the U.K. Radiological Congress in June.

Ireland has the highest rate of heart disease in Europe, accounting for 42% of all deaths, said lead researcher Catherine D'Helft from the School of Diagnostic Imaging, St. Anthony's in Dublin.

Interventional cardiac procedures play an important role in tackling this problem, and the number of patients referred for interventional cardiology has increased because of the technique's cost-effectiveness relative to surgery. Patients can be treated as outpatients or as day cases, and the complication rate is low.

"However, the radiation doses associated with such procedures are high compared with other diagnostic x-ray exams. They have been reported to be close to thresholds causing deterministic radiation effects. This dose implication must be carefully monitored," D'Helft said.

The researchers determined radiation exposure levels to patients for coronary angiography, percutaneous coronary interventions, and permanent pacemaker insertion procedures. They detailed factors that may influence radiation dose: patient demographics, the grade of the cardiologist, projections acquired, equipment specifications, exposure factors, and a complexity score for all exams.

They also identified elements associated with low radiation dose and acceptable/high image quality.

Data on dose measurements using calibrated dose-area product meters, collated from 15 participating centers in the Republic of Ireland and Northern Ireland, are still being collected and analyzed. The researchers presented preliminary results at the June congress and at the European Congress of Radiology in March.

Mean dose values for coronary angiography, percutaneous coronary interventions, and permanent pacemaker insertion were 7426 cGy cm², 10,744 cGy cm², and 3705 cGy cm², respectively, although large exam-specific variations were apparent.

The team also compared data for coronary angiography and percutaneous coronary interventions procedures with radiation dose levels determined by the DIMOND project (Eur Radiol 2003;13:2259-2263).

Dose values from the Irish study were higher than those in the DIMOND project. For coronary angiography and percutaneous coronary intervention procedures, the radiation doses recorded in Ireland were 1.3 and 1.1 times higher, respectively, than those reported by the DIMOND group.

"Direct relationships are being noted between radiation doses and screening time and examination complexity," D'Helft said. "There is also some evidence to suggest that the grade of the operator, patient body mass index, and techniques employed also impact radiation dose levels."

Doses should be kept as low as reasonably achievable consistent with optimizing image quality. Significant variations in radiation dose exist, and doses appear to be higher than those published elsewhere, but the current results are preliminary, she said.

For more information from the Diagnostic Imaging archives:

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IR radiation dose comes under scrutiny