Radiation dose simulations for personnel involved in fluoroscopically guided interventional procedures

Abstract

To achieve this goal, three tasks are conducted in this study: (1) development of Monte Carlo simulation capability for radiation field and organ dose calculations in the FGI suite; (2) characterization of the relationship between the organ dose to operators and the operation setting involving variables such as X-ray tube, personnel protective equipment, patient and operator using Monte Carlo simulations; (3) development of radiation protection strategies for personnel involved in FGI procedures, including practical suggestions on dose reduction and design of a mixed-reality based radiation training system. Three-dimensional (3D) models of the FGI suite, the patient and the operator are developed. Radiation doses to several critical organs (brain, thyroid, heart, and eye lens) of FGI operators are calculated using Monte Carlo radiation transport code MCNP. The relationship between organ dose to operators and various operation setting variables are characterized. Specifically, the effects of X-ray parameters including the X-ray tube voltage, filtration, field of view and beam projections on organ doses are investigated. The relationship between the position, height, body orientation and head posture of the FGI operators and organ doses are quantified. The efficacy of protective equipment such as lead eyewear, lead vest, lead collar and lead shields is evaluated. Results show that for the X-ray source, higher tube voltage with a thicker filtration tends to result in a lower level of organ dose to FGI personnel. The field of view is found to have a small effect on the operator’s organ dose. Compared with other beam projections (Anterior Posterior, Postero-Anterior), Caudal and Cranial projections are found to deliver lower organ dose to the FGI operators. Organ dose to operators is also found to decrease as the patient size increases. The results also show that the organ dose is very sensitive to the position and orientation of the exposed person. Results suggest that the operator can reduce exposure by avoiding facing left and standing too close to the patient. It is also found that the head gesture of the operator has a significant impact on the lens dose and brain dose.

According to the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), among all medical professionals who are exposed to X-rays, personnel involved in fluoroscopically guided interventional (FGI) procedures receive the greatest occupational radiation exposure due to scattered X-rays from the patient. Occupational radiation protection in FGI procedures has been a top concern for regulatory agencies and professional societies. The objective of this study is to investigate and assess how various parameters in FGI procedures affect the organ dose to operators in the FGI suite, and to propose clinically deployable measures for radiation protection purposes.

Results suggest that operators can reduce their lens dose and brain dose by avoiding bending head down unless necessary. Protective equipment such as ceiling-suspended lead shields, lead vest and lead collar is found to be essential for dose reduction in FGI procedures. Lead cap and lead eyewear are found to be effective to protect the brain and eye lens. However, their efficacy is affected by the head posture of the operator. Other factors such as the shape of the eyewear and face-to-eyewear distance are also found to have an impact on the efficacy of protective eyewear. Sports wrap protective eyewear which conforms to the curve of the face is essential for the radiation protection of the eye lens. Based on Monte Carlo simulation results, a conceptual design of a mixed reality (MR) based radiation safety training system is proposed to help operators understand complex radiation fields and to avoid high radiation areas through game-like interactive simulations using the Microsoft Hololens headset. The preliminary development of the MR-based training system has demonstrated the feasibility to calculate and report the radiation exposure after each training session based on a database precalculated in task 2. In addition, real-time dose rate and cumulative dose can be displayed to the trainee by Hololens to help them refine their practice.