HARMONIC organ dose calculation framework for cardiac fluoroscopy

<i>Introduction</i>. The HARMONIC study (health effects of cardiac fluoroscopy and modern radiotherapy in paediatrics) investigates, among other objectives, the relationship between ionising radiation and cancer incidence in children treated by cardiac fluoroscopy (HARMONIC-Cardio). This requires estimation of organ doses for a large patient cohort. This article describes the development and validation of a framework for calculations of cardiac fluoroscopy doses, and its application to build a software tool for rapid cohort dosimetry.<i>Materials and methods</i>. Organ doses were calculated with MCNP6.2, a Monte Carlo particle transport code. Realistic, anthropomorphic phantoms representing patients of both sexes at specific ages (newborn, 1, 5, 10, 15 year old and adult) were used. A large range of technical parameters was covered in the simulations, including 11 primary beam angles and seven secondary angles, four levels of beam filtration, three tube voltages and three field sizes. The absorbed dose was computed for 32 organs and tissues. The calculated organ doses were normalised to the air kerma-area product (P_KA), a common modality-specific dose index, resulting in P_KA-to-organ-dose conversion coefficients.<i>Results</i>. Organ dose conversion coefficients were calculated for 22,176 exposure configurations and extended to a total of 2,667,600. A coefficient database for 12 organs of interest for radiation protection and effective dose, was embedded in HARMONIC-CardioDose, a software tool that enables the estimation of organ doses for any exposure scenario within the simulation range. The program is in the form of a Python script or an executable file (.exe), and uses an Excel document for inputting the calculation parameters.<i>Conclusion</i>. A framework for the calculation of cardiac fluoroscopy doses was developed and validated. It was used as the basis for HARMONIC-CardioDose, a rapid software tool for organ dose estimates for epidemiology studies. The tool is also freely available to the medical and research community for supporting patient dosimetry.