In this article, Bijan Modarai outlines recent research on the effects on radiation exposure in high-volume interventionists, why a future with alternative modalities to X-ray guided procedures is an exciting prospect, and what safety measures could make a difference in the meantime.
In recent years, alarming and emotive reports of cancer diagnoses made in high-volume interventionists at a relatively young age have focused attention on the deleterious effects of occupational radiation exposure. The fact that even the low doses absorbed during fluoroscopically guided procedures can induce DNA damage, triggering inherent reparative mechanisms within the cell, are now beyond doubt and our group has shown this to be the case in both patients and operators after endovascular aortic procedures. These studies also suggested the fact that operators may have differential sensitivity to the same exposure dose. DNA repair pathways are error-prone and can lead to genomic instability and cytogenetic damage after chronic radiation exposure. In the absence of long-term studies in large cohorts of health workers, however, a definitive link between exposure and malignant transformation remains difficult to prove.
Our bodies are continuously bombarded by low-dose environmental radiation and in the UK, for example, an individual would accumulate approximately 2mSv of natural background exposure per year. Flying at altitude increases this exposure, with a 10 hour flight accounting for an extra 50μSv. A link between low dose exposure and cancer may be emerging with a recent publication showing an increased incidence of cancer in pilots who have the highest cumulative air hours and large dose exposures before the age of 40. Our recent studies monitoring real-time radiation exposure have measured an average dose of approximately 70μSv to exposed body parts after a complex endovascular aortic repair. A high volume operator, performing 50 cases per year, for instance, would incur a significantly raised dosage over that time. A modern day vascular trainee in their early 30s would be at risk of accumulating the aforementioned yearly dose for more than 30 years, with consequences that are unknown at present but may become apparent as our understanding of the ill effects of chronic exposure improves.
Real-time monitoring has allowed linkage of operator behaviours that account for the highest dose exposure. Protective manoeuvres during digital subtraction angiography (DSA) appear to be particularly important. Left lateral angulation of the C-arm, distance of the operator from the table and the “air gap” between the detection plate and the patient’s body are independent predictors of radiation exposure during DSA. The operators who were studied remained tableside for the majority of DSA runs, significantly increasing their absorbed dose. Perhaps a paradigm shift in strategies that ensure minimal exposure throughout the procedure is required. A non-operating “spotter”, delegated with prompting the operator to instigate optimal protective manoeuvres for themself and the rest of the team, particularly during the more critical steps of the procedure when focus on radioprotection may wane, could prove highly effective in reducing dose.
A definitive link between low-dose chronic radiation exposure and cancer remains to be demonstrated, but the mere fact that exposure can trigger DNA damage should motivate all, and in particular young and training vascular interventionists, to optimally protect themselves. The promise that one day we may circumvent the use of X-rays during procedures, instead using modalities such as electromagnetic guidance, for example, is exciting. Until then, encouraging radiation safety behaviours, ensuring optimal room set up and insisting on maximal shielding is of paramount importance.
Bijan Modarai is a reader/consultant in vascular surgery and a senior fellow at the British Heart Foundation.