Author + information
- Lloyd W. Klein, MD⁎ ( and )
- Justin Maroney, MD
- ↵⁎Reprint requests and correspondence:
Dr. Lloyd W. Klein, Professional Office Building, 3000 North Halsted, Suite 625, Chicago, Illinois 60657
The nature of ionizing radiation and its potential health-related effects on catheterization laboratory personnel are well recognized (1) and require the use of protective shielding. Despite the known occupational hazards, the general design of the cardiac catheterization and interventional laboratory has remained stagnant over the past 50 years. Although there have been countless innovations in the types of procedures performed and the instruments used, there has been little substantial improvement in the protection of those who work in the laboratory (2). The necessity for placement of the x-ray tube in close proximity to the operator requires coordinated use of ceiling- and table-mounted lead shielding, and the requirement for wearing protective apparel, yet their optimal employment continues to be operator-dependent (3,4). Indeed, although modern laboratories have the capability to measure all the main radiologic parameters of dose and exposure, few systematically record and evaluate their use of x-rays, and essentially none have ongoing quality assurance of this modality. Indeed, intervening and counseling physicians in regard to limiting fluoroscopy time, using the shielding in the room properly, and remaining cognizant of the angulations used may at times challenge the patience of the laboratory director.
In this issue of JACC: Cardiovascular Interventions, Fetterly et al. (5) measure the protection from scatter radiation provided to the operator by various radiation shield devices that are widely available in cardiac interventional laboratories. A ceiling-mounted upper body shield, a table side rail–mounted lower body shield, an accessory vertical shield that mounts as an upper extension of the lower body shield, and a disposable radiation-absorbing pad were evaluated individually and in combination. A standardized dose of scatter radiation was generated by directing an x-ray beam through an anthropomorphic phantom in a straight posterior–anterior position using 10-s cine acquisitions at a fixed peak tube potential. Scatter radiation air kerma measurements were made at specific elevations for 3 common physician positions corresponding to standard right femoral artery, right jugular vein, and left anterior thoracic access points. The fraction of scatter radiation transmitted through or around these 4 radiation shields alone and in combination was measured, and the shields' relative radiation protection versus no use of shielding was calculated. Additionally, optimal placement of the ceiling-mounted shield was explored by measuring the relative radiation protection provided by shield positions tight to the phantom versus loose to the phantom, and caudal (closer to the operator at the vascular access point) versus cephalad (closer to the radiation source).
Fetterly et al. (5) report that the radiation shield devices examined provide maximal relative scatter radiation protection for an operator at the femoral artery access position. A combination of the ceiling-mounted shield, table side rail–mounted shield, accessory vertical shield, and radiation-absorbing pad offers >90% relative reduction in scatter radiation exposure at heights below 150 cm (and >80% relative reduction in exposure above this height) at the femoral position. Furthermore, they determined that the positioning of the ceiling-mounted shield is crucial to its efficacy: a position tight to the phantom and just cephalad to the vascular access point (closer to the operator) is more than 4 times as effective as positioning the shield loose to the phantom and 20 cm more cephalad (closer to the x-ray tube), reducing scatter radiation exposure to the upper body by >80% in the former position versus <20% in the latter.
Scatter radiation is the principal source of radiation exposure to interventional physicians and fluoroscopy suite staff (1). Kuon et al. (6) have detailed the significant reduction in scatter radiation exposure provided by the use of catheterization table overcouch (ceiling-mounted) and undercouch (side rail–mounted) radiation shields during angiography. Furthermore, they emphasized the importance of shield positioning to minimize scatter radiation. They found that minimizing the area of the vertical gap between the undercouch and overcouch shields minimized scatter radiation “leakage” through the gap and reduced operator exposure. Fetterly et al. (5) add to the fundamental understanding of scatter radiation protection with their finding that physician exposure in the femoral artery access position is best reduced by positioning the ceiling-mounted shielding as tight to the patient's body as possible, and caudal, as close to the operator's femoral access position as possible, rather than closer to the x-ray tube (farther from the operator). Contrary to common practice, positioning the ceiling shield closer to the x-ray tube to maximize its radiation “shadow” is less effective than using the shield as one would use an umbrella in wind-driven rain: the closer to the operator's body the more effective. Additionally, Fetterly et al. (5) provide experimental confirmation that a shield position tight to the patient's body reduces scatter radiation “leakage” through any gaps between the patient and the shielding.
One limitation of the study is the sole use of a straight posterior–anterior angulation when generating the standard radiation doses. In clinical practice, the commonly used left anterior oblique cranial angulations often result in the x-ray tube disrupting the apron of the side-rail mounted lower body shield, opening a “gap” in lower body protection. Performing their relative exposure measurements in standard left and right anterior oblique cranial and caudal angulations might reveal unexpected sources of radiation leakage between shields, or between components of an individual shield (such as the apron on many lower body shields), as well as simple shield-positioning adjustments or different fluoroscopy angulations that could be used to compensate.
Interventional cardiologists are keenly aware of the “as low as reasonably achievable” principle governing patient radiation exposure in the interventional laboratory. Fetterly et al. (5) emphasize the importance of optimal shielding of the operator for protection from the radiation that must be used to achieve diagnostic and/or therapeutic success. That the most advantageous shield positioning can have a greater than 4-fold relative reduction in scatter radiation exposure supports its use even when inconvenient, and suggests that learning to coordinate multiple shields should be among the fundamental principles taught in every interventional cardiology training program. Moreover, the future interventional laboratory must be designed so that radiation safety is not predicated on the voluntary cooperation, sensitivity, and education of operators, but rather is constructed into the design of the laboratory.
The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
↵⁎ Editorials published in JACC: Cardiovascular Interventions reflect the views of the authors and do not necessarily represent the views of JACC: Cardiovascular Interventions or the American College of Cardiology.
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