The Hindu published an artcile on October 1, 2009
Dr K.S.Parthasarathy
Date:01/10/2009 URL: http://www.thehindu.com/thehindu/seta/2009/10/01/stories/2009100150441500.htm
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How safe are interventional cardiac procedures?
— Photo: S. Thanthoni
Within threshold: Radiation risk is acceptably low when compared to risk of not carrying out the procedures when indicated.
Recently, radiation protection measures in interventional radiology especially in cardiology have been receiving special attention.
These are image-guided therapeutic techniques such as coronary angioplasty (to remove blockades in artery) and diagnostic techniques such as angiography (imaging the blood vessels using an x-ray contrasting agent).
These life-saving procedures require specially designed equipment and involve high radiation exposures to physicians, technologists and patients. Cardiologists must know the equipment specification and characteristics to use radiation effectively and optimally.
Risks compared
Radiation risk is acceptably low when compared to risk of not carrying out the procedures when they are medically indicated.
Recently, a survey supported by the International Atomic Energy Agency (IAEA) in 55 hospitals in 20 countries of Africa, Asia, and Europe indicated that many patients exceeded the dose threshold for erythema (skin reddening); a substantial number (62 per cent) of coronary angioplasty procedures exposed patients to doses above the recommended dose reference level. (American Journal of Roentgenology, August 2009). Though specially needed dose measuring instruments were in place in almost half the facilities, none had experience in its use.
Hundred out of 505 patients monitored, had peak skin doses above the 2-Gy threshold for deterministic effects (Gy is a unit of radiation dose; one Gy is equal to one joule per kg).
Inadequately trained
IAEA has noted that many physicians using interventional radiology techniques are not adequately trained in radiation safety or radiobiology. In a few cases, patients may suffer radiation-induced skin injuries which may go unnoticed. Younger patients may face an increased risk of future cancer.
Patients may ask their physicians about the radiation dose they are likely to get in the procedure. If they feel any changes in the exposed area of the skin later, they must report it to their physician. Though radiation dose is important, it is only one of the factors to be considered.
The dose to patients must be As Low As Reasonable Achievable (ALARA). Cardiac procedures are very complex, doses will be ALARA only if the cardiologists appreciate the importance of dose reduction; they must be constantly vigilant. If patient’s dose is reduced, occupational dose also will be reduced.
A few years ago, a medical physicist working in a corporate hospital introduced me to an eminent cardiologist who has been saving hundreds of lives. “When I have too many patients, I just remove the personnel monitoring badge”, he confessed. Unknown to him, he may become a victim of his carelessness.
Regular monitoring
Cardiologists must monitor their radiation doses regularly; they are among the category of radiation workers who have highest probability to get significant doses.
IAEA surveys conducted during training courses in which cardiologists from 56 countries participated showed that only 33 to 77 per cent of them use personnel dose measuring devices routinely.
During a workshop in Mumbai two cardiologists listed several telling deficiencies ( http://www.aerb.gov.in/t/newsflash/cathlab.pdf).
Cardiologists are not aware of the radiological safety precautions to be taken during angiography or angioplasty. They lack awareness of personal protective equipment, personnel dose monitoring devices and their proper use.
Lens of the eye is radiosensitive. Cardiologists remain near x-ray sources within high scatter radiation areas for several hours every day.
Preliminary results from the IAEA study called Retrospective Evaluation of Lens Injuries and Dose (RELID) indicate identifiable damage to the lens of those cardiologists not using eye protection.
A summary of the results of studies carried out in Colombia, Malaysia, Uruguay and Bulgaria during 2008-09 is freely available (http://rpop.iaea.org/RPOP/RPoP/Content/News/relid-activities.htm). Protracted eye lens dose of 4Gy over 3 months or 5.5 Gy delivered over five months may cause detectable opacities to the eye lens.
IAEA has been very active in the field of radiation protection. They offer educational material of inestimable value free at their web site (http://rpop.iaea.org/).
The International Commission on Radiological Protection has issued its publication No 85 titled “Avoidance of radiation injuries from medical interventional procedures” ( http://www.icrp.org/
educational_area.asp).
K.S. PARTHASARATHY
Former Secretary, AERB
( ksparth@yahoo.co.uk )
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